Effect of Turbulence Modeling on Particle Dispersion and Deposition on Compressor and Turbine Blade Surfaces

Abstract

One of the main mechanisms that control particle movement is the turbulent diffusion by which the particles in the turbulent boundary layer migrate to the surface under the influence of random flow fluctuations. Theoretical approaches to particle dispersion use random walk models to represent the effect of turbulent fluctuation velocity on particle movement. As a consequence, the turbulence model has a significant effect on the particle trajectory. Particle sticking probability, on the other hand depends upon the particle impact velocity. Moreover, the wall shear stress that is calculated from the turbulence model is the main cause of particle detachment from the surface. In this work, the effect of turbulence models on particle dispersion, deposition on turbine blade surfaces and detachment from the surfaces is studied. Two turbulence models have been tested: the Renormalization Group (RNG) k-ε model and the standard k-ε model. The near-wall region is solved by two different models: the standard wall function and the two-layer zonal model. It is found that the RNG k-ε model with the two-layer zonal near-wall model is the more appropriate turbulence model for particle deposition. It is also concluded that the standard wall function should not be used when solving the flow field near the wall for particle deposition. The reason is that this method does not give the detailed solution of the flow near the wall that is very important for deposition models.