Simulation of the turbulent, nonreacting hydrogen air mixing flowfield in an axisymmetric, sudden expansion geometry is discussed. Numerical solutions for the compressible form of the full Navier-Stokes equations including the energy equation, the turbulence model equations and the species equation are obtained. The two-equation turbulence model used in the present work appears to be well suited for the present problem compared to algebraic eddy viscosity models and one-equation models. Compared with available experimental data, the numerical results indicate reasonable agreement in the distributions of velocity, mass fraction along both axial and radial directions and the wall static pressure. © 1989.