Particle-laden swirling flow

Application Challenge AC3-12 © copyright ERCOFTAC 2013

Overview of CFD Simulations

Detailed numerical calculations were also performed by Sommerfeld et al. (1992) and Sommerfeld and Qiu (1993) using the two-dimensional axially-symmetric Euler/Lagrange approach without two-way coupling. The fluid flow calculation is based on the time-averaged Navier-Stokes equations in connection with a closure assumption for the turbulence modelling. The solution of the above equations is obtained by using the so-called FASTEST-code (Dimirdzic and Peric, 1990) which incorporates the well-known k-ε two-equation turbulence model and uses a finite- volume approach to descretize the equations. In order to minimize the effects of numerical diffusion in the present calculations, the quadratic, upwind-weighted differencing scheme (QUICK) was used for differencing the convection terms. Furthermore, flux-blending techniques, where the convective flux can be calculated as a weighted sum of the flux expressions from the "upwind" and QUICK differencing schemes (Peric et al., 1988), was used to avoid instabilities and convergence problems that sometimes appear when using higher order schemes. The choice of the solution procedure described above was based on the recommendations of Durst and Wennerberg (1991) who also concluded that for moderate swirl intensities the k-( turbulence model performs reasonably well.

Computational Domain and Boundary Conditions Fluid Flow

The present calculations have been performed on a mesh of 80 by 78 grid points in the stream-wise and radial directions, respectively. For two- dimensional axis-symmetric calculations this grid resolution was found to be sufficient as demonstrated by Durst and Wennerberg (1991). The computational domain corresponds exactly to the experimental configuration given in Figure 1. However, in the stream-wise direction it was only extended up to 1.0 m downstream from the inlet. The applied inlet conditions correspond to the measured mean velocity components (i.e. available for all three components) and the measured turbulent kinetic energy. At the walls no-slip conditions were applied in connection with the standard wall function. At the outflow boundary zero-gradients have been assumed.