SUMMARY The suitability of Wilcox's 2006 k– ω turbulence model for scramjet flowfield simulations is demonstrated by validation against five test cases that have flowfields representative of those to be expected in scramjets. The five test cases include a 2D flat plate, an axisymmetric cylinder, a backward‐facing step, the mixing of a pair of coaxial jets and the interaction between a shock wave and turbulent boundary layer. A generally good agreement between the numerical and experimental results is obtained for all test cases. These tests reveal that despite the turbulence model's sensitivity to freestream turbulence properties, the numerically predicted skin friction agrees with experimental data and theoretical correlations to their degree of uncertainty. The tests also confirm the importance of using a y+ value of less than 1 in getting accurate surface heat transfer distributions. In the coaxial jets case, the importance of matching the turbulence intensities at the inflow plane in improving the predictions of the turbulent mixing phenomena is also shown. A review of guidelines with regard to the setting up of grids and specification of freestream turbulence properties for turbulent Reynolds‐averaged Navier–Stokes CFD simulations is also included in this paper. Copyright © 2011 John Wiley & Sons, Ltd.

A method is proposed for the aerodynamic design of nozzles with uniform outflow for supersonic and hypersonic ground-test facilities. This method involves the coupling of an open-source Reynolds-Averaged Navier-Stokes CFD solver, Eilmer, with the simplex optimisation method of Nelder & Mead for the design of an expanding nozzle contour with the least variations in Mach number and flow angularity. Three nozzles were designed using this method to produce an exit flow of Mach 4, Mach 7 and Mach 10. Numerical simulations of the flow in these optimised nozzle contours showed excellent flow uniformity in the core flow-typical Mach number variations were less than 0.5%, flow angularity variations were less than 0.05 • , static temperature and flow velocity variations were less than 1%, and Pitot and static pressures variations were less than 2%. Experimental surveys of the Pitot pressures at several planes downstream of the exit of the three optimised nozzles showed excellent agreement with numerical simulations. The experimental measurements showed that there were good levels of uniformity in the core flow regions of all three nozzles, thus proving the validity of the proposed design method.

Abstract

No abstract

No abstract