03.1 - Aerodynamics – CFD Methods and Validation
HYBRID NUMERICAL SCHEMES IN PREDICTION OF HIGH-SPEED LAMINAR-TURBULENT TRANSITION
I.V. Egorov, Russia; A.V. Novikov, Russia; N.K. Nguen, Vietnam
The problem of laminar-turbulent transition (LTT) in supersonic boundary-layer flows is one of the main still unsolved problems of high-speed aerodynamics. LTT leads to a substantial increase of the surface heating and aerodynamic drag of hypersonic vehicles and, thereby as well as affects the efficiency of propulsion system and control surfaces.rnA holistic computation of the all LTT stages is possible only using direct numerical simulations (DNS), where the full unsteady three-dimensional (3D) Navier–Stokes equations are solved without any restriction on the mean (unperturbed laminar) flow and disturbance amplitudes. In addition, as opposed to physical experiments, DNS gives full information about 3D disturbance field, which enables to identify and study in detail different LTT mechanisms. The modern methods of parallel computations and rapid developments of multi-processor supercomputers make it feasible to conduct such numerical experiments for hypersonic boundary layers for simple configurations such as a flat plate and a cone at zero angle of attack [1]. Further progress in computational hardware will allow us to handle more and more complicated and practical configurations. At the same time it is necessary to use difference schemes with minimum dissipative properties that don’t lead to numerical instability in order to increase effectiveness of numerical simulation. Such difference schemes can be hybrid schemes, which are an approximation of convective terms in Navier-Stokes equations with use of central difference schemes and monotone schemes with weights. This talk will demonstrate that use of hybrid difference schemes allow increasing accuracy of numerical data in comparison with fully monotone difference schemes on the same numerical grid. rnIn particular, we discuss our DNS of a transitional flow over a flat plate at the freestream Mach number 3 and high unit Reynolds numbers. The flow parameters are the same as at [2]. It