HiFi-TURB-DLR rounded step

Semi-confined flows

Underlying Flow Regime 3-36

Test Case Study

Brief Description of the Study Test Case

The geometry of this UFR alongside the mesh is shown in Fig. 1. The geometry comprises three main sections: Constant-Width Forebody section ${L_{F}}$ with the largest width ${Y_{F}}$ , Contoured Boat-tail section ${L_{B}}$ with the contoured width ${Y_{B}}$ and Constant-Width-Aftbody section ${L_{A}}$ with the smallest width ${Y_{A}}$ . The width of the last section is modified to generate the desired APG. This modification is achieved through the variation of ${\sigma }$ , which is the ratio of ${Y_{A}}$ to ${Y_{F}}$ .

Figure 1: Flow Domain and grid of RANS simulations

The parametric geometry definition for the three relevant sections is given in [‌6] and is depicted in Fig. 1. The axial origin ${x=0}$ is set at the beginning of the Boattail section.

{\begin{aligned}y_{wall}&=y_{F}=H/(1-\sigma )\qquad \mathrm {for} \qquad -L_{F}<x/H\leq 0\\y_{wall}&=y_{B}=a_{1}+a_{2}x^{3}+a_{3}x^{4}+a_{4}x^{5}\qquad \mathrm {for} \qquad 0<x/H\leq L_{B}\qquad \qquad (1)\\y_{wall}&=Y_{A}=\sigma H/(1-\sigma )\qquad \mathrm {for} \qquad L_{B}<x/H\leq L_{B}+L_{A}\\\\\end{aligned}}

with ${a_{1}=H/(1-\sigma )}$ , ${a_{2}=-10H/L_{B}^{3}}$ , ${a_{3}=15H/L_{B}^{4}}$ and ${a_{4}=-6H/L_{B}^{5}}$ .

CFD Methods

RANS Turbulence models

For the entire computational domain, a structured 2D mesh was created using Pointwise V18.2. Sensitivity studies were carried out. The final mesh contains a total of ${266.112}$ points. Along the body contour 448 points are used in streamwise direction with a smaller spacing in the focus region. In the normal direction to the body wall 298 points are used, 98 of which are concentrated near the body wall region. The body wall-normal growth ratio is approximatively 1.077 and the dimensionless distance from the wall is y^+<1 along the body wall for all meshes and simulation scenarios.