Influence of discretization of turbulence equation diffusion terms on flow field compuation of a radial impeller

By discretizing convective terms with the HLLC scheme in the relative rotating coordinate system, a finite volume analysis code based on multi-block structured grids was developed independently, in order to numerically solve the internal flow fields of turbomachineries. The flow simulations of an unshrouded radial impeller and a shrouded backswept impeller were carried out respectively. The surface pressure at various blade heights calculated by the code and commercial software agrees well with the relative difference smaller than 1%, which verifies the accuracy of the algorithm. As for the diffusion terms of turbulence equations, full discretization and part discretization by neglecting cross-derivative terms were used respectively. Through comparisons of turbulence viscosity contour, aerodynamic force and moment, it indicates that neglecting cross-derivative terms exerts little impact of less than 1% on the results when the grid orthogonality is not too bad, and thus the calculation quantity of turbulence equations can be reduced obviously.