Abstract: Numerical simulations of the blade to blade flow field in a centrifugal impeller have been carried on by using 2 D mean steady incompressible Navier Stokes equations and k ε turbulent model in arbitrary boundary fitted coordinate system.It is shown that the underrelaxation factors of line by line iteration are lower than those in non rotational flow calculations and a more reasonable initial flow field is required due to the larger ratio of centrifugal forces in the source terms of momentum equations.The calculation results of the flow fields are in a good agreement with the LDA data with the exception of the near wall region of the blade surfaces.Some of the discrepancies in the near wall region are caused mainly by the assumption of 2 D flow and ignoring the rotational effects in the turbulence model.Additionally,the calculation precision is also affected,since inlet and outlet boundaries of the computational domain cannot be located so far away from the blades.