https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&feed=atom&action=history UFR 3-15 Evaluation - Revision history 2024-03-28T16:13:25Z Revision history for this page on the wiki MediaWiki 1.39.2 https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=33596&oldid=prev Dave.Ellacott: Dave.Ellacott moved page Gold:UFR 3-15 Evaluation to UFR 3-15 Evaluation over redirect 2017-02-12T13:30:10Z <p>Dave.Ellacott moved page <a href="/w/index.php/Gold:UFR_3-15_Evaluation" class="mw-redirect" title="Gold:UFR 3-15 Evaluation">Gold:UFR 3-15 Evaluation</a> to <a href="/w/index.php/UFR_3-15_Evaluation" title="UFR 3-15 Evaluation">UFR 3-15 Evaluation</a> over redirect</p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <tr class="diff-title" lang="en"> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:30, 12 February 2017</td> </tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div> </td></tr></table> Dave.Ellacott https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=21804&oldid=prev Dave.Ellacott: /* Comparison of CFD calculations with Experiments */ 2011-09-25T13:11:44Z <p><span dir="auto"><span class="autocomment">Comparison of CFD calculations with Experiments</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:11, 25 September 2011</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l358">Line 358:</td> <td colspan="2" class="diff-lineno">Line 358:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>As pointed out by P. Durbin, the skin friction is larger in JD experiments due to the low Reynolds number of the flow and this is correctly predicted by his k-&amp;epsilon;-&amp;chi;&lt;sup&gt;2&lt;/sup&gt; model, although a larger negative value than the observed one is predicted for the DS case. The main difference with respect to experiments is the extent of the positive skin friction coefficient that is due to the secondary bubble located in the base corner of the step. In Parneix and <del style="font-weight: bold; text-decoration: none;">Durbin’s </del>(1996) second moment calculations, the size of this secondary bubble is still smaller than the observed one. Figure 5, taken from Parneix and Durbin (1996), shows the streamlines obtained with the second moment closure model compared to those obtained by DNS.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>As pointed out by P. Durbin, the skin friction is larger in JD experiments due to the low Reynolds number of the flow and this is correctly predicted by his k-&amp;epsilon;-&amp;chi;&lt;sup&gt;2&lt;/sup&gt; model, although a larger negative value than the observed one is predicted for the DS case. The main difference with respect to experiments is the extent of the positive skin friction coefficient that is due to the secondary bubble located in the base corner of the step. In Parneix and <ins style="font-weight: bold; text-decoration: none;">Durbin's </ins>(1996) second moment calculations, the size of this secondary bubble is still smaller than the observed one. Figure 5, taken from Parneix and Durbin (1996), shows the streamlines obtained with the second moment closure model compared to those obtained by DNS.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This aspect was studied in depth by Hanjalic and Jakirlic (1998) for second moment closures. The predicted length of the secondary bubble is approximately 0.5 with the LRRG and SSG models (a little bigger in the first one) as can be seen in the streamline patterns presented. A small improvement is obtained when using the modified P equation.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This aspect was studied in depth by Hanjalic and Jakirlic (1998) for second moment closures. The predicted length of the secondary bubble is approximately 0.5 with the LRRG and SSG models (a little bigger in the first one) as can be seen in the streamline patterns presented. A small improvement is obtained when using the modified P equation.</div></td></tr> </table> Dave.Ellacott https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=11141&oldid=prev Niek.verhoeven at 17:16, 29 August 2009 2009-08-29T17:16:23Z <p></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 17:16, 29 August 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l499">Line 499:</td> <td colspan="2" class="diff-lineno">Line 499:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{UFR|front=UFR 3-15|description=UFR 3-15 Description|references=UFR 3-15 References|testcase=UFR 3-15 Test Case|evaluation=UFR 3-15 Evaluation|qualityreview=UFR 3-15 Quality Review|bestpractice=UFR 3-15 Best Practice Advice|relatedACs=UFR 3-15 Related ACs}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{UFR|front=UFR 3-15|description=UFR 3-15 Description|references=UFR 3-15 References|testcase=UFR 3-15 Test Case|evaluation=UFR 3-15 Evaluation|qualityreview=UFR 3-15 Quality Review|bestpractice=UFR 3-15 Best Practice Advice|relatedACs=UFR 3-15 Related ACs}}</div></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;"></del></div></td><td colspan="2" class="diff-side-added"></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;"></del></div></td><td colspan="2" class="diff-side-added"></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">[[Category:Underlying Flow Regime]]</del></div></td><td colspan="2" class="diff-side-added"></td></tr> </table> Niek.verhoeven https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=8894&oldid=prev Tonyh at 10:07, 14 April 2009 2009-04-14T10:07:15Z <p></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:07, 14 April 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l419">Line 419:</td> <td colspan="2" class="diff-lineno">Line 419:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This secondary bubble is absent when using k-&amp;epsilon; model, and appeared when using two layer models as pointed out by Rodi (1991). In the works of Menter (1994) and Menter (1996) it can be inferred from the C&lt;sub&gt;f&lt;/sub&gt; distribution. These two equation calculations predicted a small (second) bubble except the k-&amp;epsilon; one equation of Menter (1996).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This secondary bubble is absent when using k-&amp;epsilon; model, and appeared when using two layer models as pointed out by Rodi (1991). In the works of Menter (1994) and Menter (1996) it can be inferred from the C&lt;sub&gt;f&lt;/sub&gt; distribution. These two equation calculations predicted a small (second) bubble except the k-&amp;epsilon; one equation of Menter (1996).</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Turbulent kinetic energy and shear stress calculations, carried out using the modified ASM model, presented by Driver and Seegmiller (1985), showed in general a good agreement to experimental values. The increase in the kinetic energy and turbulent stresses after the step and their decrease after the reattachment are correctly predicted. There are however some differences in the backflow region mainly in the position of the peak values of both turbulent shear stress and turbulent kinetic energy. The authors suggest some problem in the convection of kinetic energy as one would expect the energy to be convected along the streamlines. The authors also comment the tendency of the unmodified k-&amp;epsilon; and ASM to overpredict the turbulent kinetic energy and shear stresses. The same situation is found by Rodi (1991) where better predictions of turbulent shear stress by two-layer models are shown. Results reported by Yoder et al. (1999) for turbulent kinetic energy profiles and turbulent shear stress show that k-&amp;epsilon; model implemented in different codes and with variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;, overpredict both the kinetic energy and the shear stress. The SST model on the other hand, underpredicts these values due to the form of the k-&amp;omega; model used in the near-wall region. The incorrect peak locations can be appreciated clearly in these figures (available at '''[http://www.<del style="font-weight: bold; text-decoration: none;">arnold</del>.<del style="font-weight: bold; text-decoration: none;">af</del>.<del style="font-weight: bold; text-decoration: none;">mil</del>/<del style="font-weight: bold; text-decoration: none;">nparc</del>/<del style="font-weight: bold; text-decoration: none;">Alliance_information</del>.html NPARC Alliance]'''), especially at ''x/''h= 2.5, 5 and 6 for both kinetic energy and shear stress and for all the turbulence models employed. It can be also mentioned that the use of variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt; reduces the turbulent kinetic energy and shear stresses mainly in the recirculation region. According to the author this is due to an increase in the turbulent dissipation rate within the recirculation zone because of the variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Turbulent kinetic energy and shear stress calculations, carried out using the modified ASM model, presented by Driver and Seegmiller (1985), showed in general a good agreement to experimental values. The increase in the kinetic energy and turbulent stresses after the step and their decrease after the reattachment are correctly predicted. There are however some differences in the backflow region mainly in the position of the peak values of both turbulent shear stress and turbulent kinetic energy. The authors suggest some problem in the convection of kinetic energy as one would expect the energy to be convected along the streamlines. The authors also comment the tendency of the unmodified k-&amp;epsilon; and ASM to overpredict the turbulent kinetic energy and shear stresses. The same situation is found by Rodi (1991) where better predictions of turbulent shear stress by two-layer models are shown. Results reported by Yoder et al. (1999) for turbulent kinetic energy profiles and turbulent shear stress show that k-&amp;epsilon; model implemented in different codes and with variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;, overpredict both the kinetic energy and the shear stress. The SST model on the other hand, underpredicts these values due to the form of the k-&amp;omega; model used in the near-wall region. The incorrect peak locations can be appreciated clearly in these figures (available at '''[http://www.<ins style="font-weight: bold; text-decoration: none;">grc</ins>.<ins style="font-weight: bold; text-decoration: none;">nasa</ins>.<ins style="font-weight: bold; text-decoration: none;">gov</ins>/<ins style="font-weight: bold; text-decoration: none;">WWW</ins>/<ins style="font-weight: bold; text-decoration: none;">wind/valid/backstep/backstep01/backstep01</ins>.html NPARC Alliance]'''), especially at ''x/''h= 2.5, 5 and 6 for both kinetic energy and shear stress and for all the turbulence models employed. It can be also mentioned that the use of variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt; reduces the turbulent kinetic energy and shear stresses mainly in the recirculation region. According to the author this is due to an increase in the turbulent dissipation rate within the recirculation zone because of the variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Figure 6, taken from Durbin (1995) presents turbulent kinetic energy profiles for both DS and JD experiments. As can be seen there is a little overprediction of turbulent kinetic energy profiles in the separated region. The peak value locations are well predicted for the JD case, and a little shifted in the DS case near the reattachment.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Figure 6, taken from Durbin (1995) presents turbulent kinetic energy profiles for both DS and JD experiments. As can be seen there is a little overprediction of turbulent kinetic energy profiles in the separated region. The peak value locations are well predicted for the JD case, and a little shifted in the DS case near the reattachment.</div></td></tr> </table> Tonyh https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=8705&oldid=prev Daveg: UFR 3-15 Evaluation moved to Gold:UFR 3-15 Evaluation 2009-04-07T13:22:59Z <p><a href="/w/index.php/UFR_3-15_Evaluation" title="UFR 3-15 Evaluation">UFR 3-15 Evaluation</a> moved to <a href="/w/index.php/Gold:UFR_3-15_Evaluation" class="mw-redirect" title="Gold:UFR 3-15 Evaluation">Gold:UFR 3-15 Evaluation</a></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <tr class="diff-title" lang="en"> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:22, 7 April 2009</td> </tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div> </td></tr></table> Daveg https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=6030&oldid=prev Daveg: /* Comparison of CFD calculations with Experiments */ 2009-03-19T10:05:34Z <p><span dir="auto"><span class="autocomment">Comparison of CFD calculations with Experiments</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:05, 19 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l350">Line 350:</td> <td colspan="2" class="diff-lineno">Line 350:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Some calculations present comparisons of the performance including the k-&amp;epsilon; model, from which the well-known fact that it underpredicts the reattachment length can be seen. In the work of Rodi (1991) it is shown the reattachment length found using the two layer k-&amp;epsilon; model is closer to the experimental value than that obtained using the k-&amp;epsilon; model, but is still 14% shorter. In later results presented by Menter (1996), the reattachment length using the k-&amp;epsilon; model was 5% short and, remarkably, using the one equation model is within the experimental uncertainty. A significant improvement was found by Driver and Seegmiller (1985) when using a modified P equation by a new production term, but only when using ASM models and not with the k-&amp;epsilon;. It is to be noted that the grid employed is coarse. Better predictions of the recirculation length (Menter (1994) and Yolder (1999)) are found when using other two equation models, k-&amp;omega; and SST. The SST was found to slightly overpredict it. The same tendency to overpredict the reattachment length was found with non linear two equation models in Apsley and Leschziner (1998), although the values are not presented in this study, this can be seen in the friction coefficient distribution. The predictions are much better when using the k-&amp;epsilon;-&amp;chi;&lt;sup&gt;2&lt;/sup&gt; model, or second moment closures. Large eddy simulations provide values that are less than 2% far from DNS.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Some calculations present comparisons of the performance including the k-&amp;epsilon; model, from which the well-known fact that it underpredicts the reattachment length can be seen. In the work of Rodi (1991) it is shown the reattachment length found using the two layer k-&amp;epsilon; model is closer to the experimental value than that obtained using the k-&amp;epsilon; model, but is still 14% shorter. In later results presented by Menter (1996), the reattachment length using the k-&amp;epsilon; model was 5% short and, remarkably, using the one equation model is within the experimental uncertainty. A significant improvement was found by Driver and Seegmiller (1985) when using a modified P equation by a new production term, but only when using ASM models and not with the k-&amp;epsilon;. It is to be noted that the grid employed is coarse. Better predictions of the recirculation length (Menter (1994) and Yolder (1999)) are found when using other two equation models, k-&amp;omega; and SST. The SST was found to slightly overpredict it. The same tendency to overpredict the reattachment length was found with non linear two equation models in Apsley and Leschziner (1998), although the values are not presented in this study, this can be seen in the friction coefficient distribution. The predictions are much better when using the k-&amp;epsilon;-&amp;chi;&lt;sup&gt;2&lt;/sup&gt; model, or second moment closures. Large eddy simulations provide values that are less than 2% far from DNS.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The k-&amp;epsilon; model gives smaller velocities than those observed in the DS experiments in the reverse flow region, a fact that is observed in the skin friction coefficient distribution along the bottom wall (Rodi(1991)). The calculations presented by Driver and Seegmiller (1985) show an improvement in this distribution when using ASM models, but mainly in the recirculation length and not in the C&lt;sub&gt;f&lt;/sub&gt; negative peak values, so the experimental velocity gradients near the wall are steeper than those calculated. The situation is improved with the two layer k-&amp;epsilon; model as reported by Rodi (1991). The C&lt;sub&gt;f&lt;/sub&gt; peaks are now a little overpredicted. This fact is even more pronounced in the JL k-&amp;epsilon; model as shown by Menter (1994) and Menter (1996) were significant improvements have been achieved with the k-&amp;omega;, the k-&amp;omega; BSL, the k-&amp;omega; SST and also with the k-&amp;epsilon; 1eq model, using a fine grid in all cases. A similar behaviour is reported by Yoder et al. (1999) (that can be seen at '''[http://www.<del style="font-weight: bold; text-decoration: none;">arnold</del>.<del style="font-weight: bold; text-decoration: none;">af</del>.<del style="font-weight: bold; text-decoration: none;">mil</del>/<del style="font-weight: bold; text-decoration: none;">nparc</del>/<del style="font-weight: bold; text-decoration: none;">Alliance_information</del>.html NPARC Alliance]''') where it is shown that the k-&amp;epsilon; models (including k-&amp;epsilon; with variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;) not only underpredict the recirculation length but also present some overshoots and undershoots in the friction coefficient. It is mentioned that this behaviour can be reduced by strongly increasing the discretization near the bottom wall. The use of a variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;, tends to reduce the turbulent viscosity within the separation region, and thus reduces the magnitude of skin friction. It is also found a good prediction of the skin friction distribution when using the SST model.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The k-&amp;epsilon; model gives smaller velocities than those observed in the DS experiments in the reverse flow region, a fact that is observed in the skin friction coefficient distribution along the bottom wall (Rodi(1991)). The calculations presented by Driver and Seegmiller (1985) show an improvement in this distribution when using ASM models, but mainly in the recirculation length and not in the C&lt;sub&gt;f&lt;/sub&gt; negative peak values, so the experimental velocity gradients near the wall are steeper than those calculated. The situation is improved with the two layer k-&amp;epsilon; model as reported by Rodi (1991). The C&lt;sub&gt;f&lt;/sub&gt; peaks are now a little overpredicted. This fact is even more pronounced in the JL k-&amp;epsilon; model as shown by Menter (1994) and Menter (1996) were significant improvements have been achieved with the k-&amp;omega;, the k-&amp;omega; BSL, the k-&amp;omega; SST and also with the k-&amp;epsilon; 1eq model, using a fine grid in all cases. A similar behaviour is reported by Yoder et al. (1999) (that can be seen at '''[http://www.<ins style="font-weight: bold; text-decoration: none;">grc</ins>.<ins style="font-weight: bold; text-decoration: none;">nasa</ins>.<ins style="font-weight: bold; text-decoration: none;">gov</ins>/<ins style="font-weight: bold; text-decoration: none;">WWW</ins>/<ins style="font-weight: bold; text-decoration: none;">wind/valid/backstep/backstep01/backstep01</ins>.html NPARC Alliance]''') where it is shown that the k-&amp;epsilon; models (including k-&amp;epsilon; with variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;) not only underpredict the recirculation length but also present some overshoots and undershoots in the friction coefficient. It is mentioned that this behaviour can be reduced by strongly increasing the discretization near the bottom wall. The use of a variable C&lt;sub&gt;&amp;mu;&lt;/sub&gt;, tends to reduce the turbulent viscosity within the separation region, and thus reduces the magnitude of skin friction. It is also found a good prediction of the skin friction distribution when using the SST model.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In Figure 4 the skin friction coefficient distribution taken from Durbin (1995) is shown including comparisons to both DS and JD experimental results.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In Figure 4 the skin friction coefficient distribution taken from Durbin (1995) is shown including comparisons to both DS and JD experimental results.</div></td></tr> </table> Daveg https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=5147&oldid=prev David.Fowler: /* Comparison of CFD calculations with Experiments */ 2009-03-12T12:06:21Z <p><span dir="auto"><span class="autocomment">Comparison of CFD calculations with Experiments</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:06, 12 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l477">Line 477:</td> <td colspan="2" class="diff-lineno">Line 477:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Figure 10, from Hanjalic and Jakirlic (1998) shows the velocity profiles at three stations in the recovery region comparing the results to those of the DNS. It is a very instructive plot showing how far from the log-law (which predicts local equilibrium) the velocity profile is, even at ''x/''h=19 and this is handled quite well by the RSM models.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Figure 10, from Hanjalic and Jakirlic (1998) shows the velocity profiles at three stations in the recovery region comparing the results to those of the DNS. It is a very instructive plot showing how far from the log-law (which predicts local equilibrium) the velocity profile is, even at ''x/''h=19 and this is handled quite well by the RSM models.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">&lt;center&gt;&lt;/center&gt;</del></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{|</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{|</div></td></tr> <tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l487">Line 487:</td> <td colspan="2" class="diff-lineno">Line 487:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|}</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;''Figure 10: mean velocities in the recovery region taken from Hanjalic and Jakirlic (1998)''</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /<ins style="font-weight: bold; text-decoration: none;">&gt;</ins></div></td></tr> <tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr> <tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">&lt;center</ins>&gt;''Figure 10: mean velocities in the recovery region taken from Hanjalic and Jakirlic (1998)''<ins style="font-weight: bold; text-decoration: none;">&lt;/center&gt;</ins></div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;font size=&quot;-2&quot; color=&quot;#888888&quot;&gt;© copyright ERCOFTAC 2004&lt;/font&gt;&lt;br /&gt;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;font size=&quot;-2&quot; color=&quot;#888888&quot;&gt;© copyright ERCOFTAC 2004&lt;/font&gt;&lt;br /&gt;</div></td></tr> </table> David.Fowler https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=5146&oldid=prev David.Fowler: /* Comparison of CFD calculations with Experiments */ 2009-03-12T12:03:10Z <p><span dir="auto"><span class="autocomment">Comparison of CFD calculations with Experiments</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:03, 12 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l451">Line 451:</td> <td colspan="2" class="diff-lineno">Line 451:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>&lt;<del style="font-weight: bold; text-decoration: none;">centre</del>&gt;''Figure 7 : turbulent shear stress taken from Alkselvol and Moin (1993).''&lt;/<del style="font-weight: bold; text-decoration: none;">centre</del>&gt;</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>&lt;<ins style="font-weight: bold; text-decoration: none;">center</ins>&gt;''Figure 7 : turbulent shear stress taken from Alkselvol and Moin (1993).''&lt;/<ins style="font-weight: bold; text-decoration: none;">center</ins>&gt;</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>&lt;<del style="font-weight: bold; text-decoration: none;">centre</del>&gt;''Solid lines LES dashed lines DNS''&lt;/<del style="font-weight: bold; text-decoration: none;">centre</del>&gt;</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>&lt;<ins style="font-weight: bold; text-decoration: none;">center</ins>&gt;''Solid lines LES dashed lines DNS''&lt;/<ins style="font-weight: bold; text-decoration: none;">center</ins>&gt;</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>&lt;<del style="font-weight: bold; text-decoration: none;">centre</del>&gt;''a) x/h=2.0 b) x/h=7.0 c) x/h=13 d) x/h=18''&lt;/<del style="font-weight: bold; text-decoration: none;">centre</del>&gt;</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>&lt;<ins style="font-weight: bold; text-decoration: none;">center</ins>&gt;''a) x/h=2.0 b) x/h=7.0 c) x/h=13 d) x/h=18''&lt;/<ins style="font-weight: bold; text-decoration: none;">center</ins>&gt;</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A very important feature of this problem is the absence of balance between production and dissipation rate of turbulent kinetic energy in the separated region, because this balance (the local equilibrium) is assumed when using wall functions. Driver and Seegmiller (1985) presented experimental data and calculations of the kinetic energy balance. The computations carried out with the different models overpredict production and dissipation of turbulent kinetic energy, The modified ASM is slightly better in predicting production but it still overestimates dissipation mainly in the shear layer. Figure 8 from Driver and Seegmiller (1985) shows experimental and calculated production and dissipation rate of turbulent kinetic energy.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A very important feature of this problem is the absence of balance between production and dissipation rate of turbulent kinetic energy in the separated region, because this balance (the local equilibrium) is assumed when using wall functions. Driver and Seegmiller (1985) presented experimental data and calculations of the kinetic energy balance. The computations carried out with the different models overpredict production and dissipation of turbulent kinetic energy, The modified ASM is slightly better in predicting production but it still overestimates dissipation mainly in the shear layer. Figure 8 from Driver and Seegmiller (1985) shows experimental and calculated production and dissipation rate of turbulent kinetic energy.</div></td></tr> </table> David.Fowler https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=5145&oldid=prev David.Fowler: /* Comparison of CFD calculations with Experiments */ 2009-03-12T12:00:41Z <p><span dir="auto"><span class="autocomment">Comparison of CFD calculations with Experiments</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:00, 12 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l451">Line 451:</td> <td colspan="2" class="diff-lineno">Line 451:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;br clear=&quot;ALL&quot; /&gt;</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>''Figure 7 : turbulent shear stress taken from Alkselvol and Moin (1993).''</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">&lt;centre&gt;</ins>''Figure 7 : turbulent shear stress taken from Alkselvol and Moin (1993).''<ins style="font-weight: bold; text-decoration: none;">&lt;/centre&gt;</ins></div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>''Solid lines LES dashed lines DNS''</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">&lt;centre&gt;</ins>''Solid lines LES dashed lines DNS''<ins style="font-weight: bold; text-decoration: none;">&lt;/centre&gt;</ins></div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>''a) x/h=2.0 b) x/h=7.0 c) x/h=13 d) x/h=18''</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">&lt;centre&gt;</ins>''a) x/h=2.0 b) x/h=7.0 c) x/h=13 d) x/h=18''<ins style="font-weight: bold; text-decoration: none;">&lt;/centre&gt;</ins></div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A very important feature of this problem is the absence of balance between production and dissipation rate of turbulent kinetic energy in the separated region, because this balance (the local equilibrium) is assumed when using wall functions. Driver and Seegmiller (1985) presented experimental data and calculations of the kinetic energy balance. The computations carried out with the different models overpredict production and dissipation of turbulent kinetic energy, The modified ASM is slightly better in predicting production but it still overestimates dissipation mainly in the shear layer. Figure 8 from Driver and Seegmiller (1985) shows experimental and calculated production and dissipation rate of turbulent kinetic energy.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A very important feature of this problem is the absence of balance between production and dissipation rate of turbulent kinetic energy in the separated region, because this balance (the local equilibrium) is assumed when using wall functions. Driver and Seegmiller (1985) presented experimental data and calculations of the kinetic energy balance. The computations carried out with the different models overpredict production and dissipation of turbulent kinetic energy, The modified ASM is slightly better in predicting production but it still overestimates dissipation mainly in the shear layer. Figure 8 from Driver and Seegmiller (1985) shows experimental and calculated production and dissipation rate of turbulent kinetic energy.</div></td></tr> </table> David.Fowler https://kbwiki.ercoftac.org/w/index.php?title=UFR_3-15_Evaluation&diff=5144&oldid=prev David.Fowler: /* Comparison of CFD calculations with Experiments */ 2009-03-12T11:59:21Z <p><span dir="auto"><span class="autocomment">Comparison of CFD calculations with Experiments</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 11:59, 12 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l430">Line 430:</td> <td colspan="2" class="diff-lineno">Line 430:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:U3-15d32_files_image013.gif]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:U3-15d32_files_image013.gif]]</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|}</div></td></tr> <tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr> <tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">&lt;br clear="ALL" /></ins></div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;center&gt;''Figure 6: Turbulent kinetic energy taken from Durbin (1995)''&lt;/center&gt;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>&lt;center&gt;''Figure 6: Turbulent kinetic energy taken from Durbin (1995)''&lt;/center&gt;</div></td></tr> </table> David.Fowler