RANS CFD applied to 2D canonical shock wave turbulent boundary layer interaction

1. Introduction John K. Harvey and Holger Babinsky 2. Physical introduction Jean Delery 3. Transonic shock wave boundary layer interactions Holger Babinsky and Jean Delery 4. Ideal gas shock wave turbulent boundary layer interactions in supersonic flows and their modeling - two dimensional interactions Alexander A. Zheltovodov and Doyle D. Knight 5. Ideal gas shock wave turbulent boundary layer interactions in supersonic flows and their modeling - three dimensional interactions Doyle D. Knight and Alexander A. Zheltovodov 6. Experimental studies of shock wave/boundary layer interactions in hypersonic flows Michael S. Holden 7. Numerical simulation of hypersonic shock wave boundary layer interactions Graham V. Candler 8. Shock wave/boundary layer interactions taking place in hypersonic flows John K. Harvey 9. Shock wave unsteadiness in turbulent shock wave boundary layer interactions P. Dupont, J. F. Debieve and J. P. Dussauge 10. Analytical treatment of shock/boundary layer interactions George Inger.

: The primary objective of this research is to enhance our understanding of the flow field physics associated with shock wave turbulent boundary layer interactions and thereby enable more accurate predictive models to be developed. It is widely recognized that shock wave turbulent boundary layer interactions are very important in a variety of high speed aerodynamic applications and yet, despite much attention to this topic in the past, the dynamic mechanisms involved remain poorly understood. The compression ramp generated shock wave turbulent boundary layer interaction is experimentally investigated in this study. It is a primary objective of this research to isolate the mechanism(s) responsible for the amplification of turbulent stresses through the shock. The interplay between the combined effects of bulk compression, concave curvature, 'direct' amplification and pressure gradient will be clarified. In addition, the dynamic mechanism(s) responsible for shock wave oscillation and the role this oscillation plays in the turbulent stress amplification through the shock will also be examined. Measurements documenting the mechanism of turbulent stress relaxation downstream of shock are also obtained.

The intent of this study on micro-array flow control is to demonstrate the viability and economy of Response Surface Methodology (RSM) to determine optimal designs of micro-array actuation for controlling the shock wave turbulent boundary layer interactions within supersonic inlets and compare these concepts to conventional bleed performance. The term micro-array refers to micro-actuator arrays which have heights of 25 to 40 percent of the undisturbed supersonic boundary layer thickness. This study covers optimal control of shock wave turbulent boundary layer interactions using standard micro-vane, tapered micro-vane, and standard micro-ramp arrays at a free stream Mach number of 2.0. The effectiveness of the three micro-array devices was tested using a shock pressure rise induced by the 10 shock generator, which was sufficiently strong as to separate the turbulent supersonic boundary layer. The overall design purpose of the micro-arrays was to alter the properties of the supersonic boundary layer by introducing a cascade of counter-rotating micro-vortices in the near wall region. In this manner, the impact of the shock wave boundary layer (SWBL) interaction on the main flow field was minimized without boundary bleed.

Large eddy simulation was made of transonic flow over a two-dimensional bump where shock wave turbulent boundary layer interaction takes place. Grid refinement and the effect of the domain width were investigated. Special care was taken to ensure physically correct inlet boundary conditions. The shock wave turbulent boundary layer interaction induces strong separation of the boundary layer and events such as bursting events in the incoming boundary layer, and creation of large flow scale structures behind the shock are detected. However, the shock features no large scale movement even though, according to several sources, the prerequisites for such movement are fulfilled.

Three-dimensional mixed explicit-implicit generalized Galerkin spectral element methods for high-speed turbulent compressible flows

Advances in CFD prediction of shock wave turbulent boundary layer interactions

Application of Direct Numerical Simulation and Large Eddy Simulation for shock wave turbulent boundary layer interaction appeared beginning in the early twenty-first century for supersonic flows. Application to hypersonic shock wave turbulent boundary layer interaction began subsequently. Examples are presented in this chapter.

Fluctuating surface pressure measurements have been made to investigate the effectiveness of boundary layer separators (BLS's) in reducing the fluctuating pressure loads produced by separated shock wave turbulent boundary layer interactions. Measurements have been made under unswept and swept compression corner interactions in a Mach 5 flow. BLS's fix the separation location and eliminate the large-amplitude, low-frequency fluctuating pressure loads upstream of the compression corners. The loads on the unswept compression corner face are reduced by as much as 59%. The BLS's also shift the mean pressure distribution on the unswept corner face in the streamwise direction. Results show that the loads on the corner face vary with the BLS height and the distance between the BLS and the compression corner. Suggestions for the optimum placement and the use of the BLS's are also made.

: An experimental study of three-dimensional (3-D) shock wave turbulent boundary layer interaction has been carried out. Interactions generated by fin models having sharp and hemi-cylindrically blunted leading edges have been studied. The emphasis in this particular study was twofold. First, the influence of incoming turbulent boundary layer thickness delta on the streamwise, spanwise and vertical scaling of the interaction was examined. Turbulent boundary layers varying in thickness from .127 cm (.05 in.) to 2.27 cm (0.89 in.) were used. In addition, a study has been conducted to examine the effects of the ratio D/delta (where D is the blunt fin leading edge diameter) on the interaction properties and scaling. Second, an investigation has been started to examine the unsteady shock wave-boundary layer structure and the resulting high frequency, large amplitude pressure fluctuations which occur ahead of and around the blunt fin leading edge. This is an area which in the past has been largely ignored, yet has important implications, since it is not clear that any mean surface property or flowfield measurements have any real physical significant. To date, measurement techniques and computer software have been developed and exploratory measurements made in the undisturbed turbulent boundary layer and also on the plane of symmetry ahead of the blunt fin.

Flow physics and sensitivity to RANS modelling assumptions of a multiple shock wave/turbulent boundary layer interaction

The unsteadiness of crossing shock wave turbulent boundary layer interactions at a nominal Mach number of 3 was examined by measuring wall pressure fluctuations using multiple, high frequency response, pressure transducers. The unsteadiness in the initial part of the interaction for all the interactions is similar to that of single fin interaction as studied by Tran and Bogdonoff (1987). However, for stronger interactions, flow downstream of the inviscid shock crossing position has a significant unsteady characteristic. In this unsteady region of the interaction, mean surface pressure rises significantly over the value obtained from the inviscid shock approximation. The energy spectrum of the fluctuating pressure signal shows a significant increase in the energy level at the higher frequencies.

Unsteady numerical simulation is carried out for shock wave turbulent boundary layer interaction (SWTBLI) at wedge shock angle θw = 10o over a flat plate at freestream Mach 6 for freestream Reynolds number varying from 17.2 × 106, 37.3 × 106 and 72.8 × 106/m and wall to stagnation temperature ratio Tw/T = 0.56. A preliminary investigation is presented to analyse the fluid-surface interaction and to determine the sound pressure level. Spectral analysis is carried out using Fast Fourier Transform. The maximum shock wave frequency is about 645 Hz. The maximum sound pressure level of 110 dB is found near the separation points. The pressure and the heat flux fluctuations are found to be strongly, especially near the separation and reattachment points.

: NATO RTO Working Group 10 was established in December 1998 to examine the technologies of plug nozzles, scramjet propulsion and Computational Fluid Dynamics (CFD) for design of propelled hypersonic vehicles. The CFD subgroup evaluated six topics: boundary layer transition and instability, real gas flow, laminar viscous-inviscid interactions, shock-shock interactions, shock wave turbulent boundary layer interaction (SWTGBLI) and base flows with and without plume interaction. This paper presents a summary of the evaluation of shock wave turbulent boundary layer interactions. Five configurations were considered: 2-D compression corner, 2-D expansion-compression corner, 2-D shock impingement, 3-D single fin and 3-D double fin. Recent Direct Numerical Simulations (DNS), Large Eddy Simulations (LES) and Reynolds-averaged Navier-Stokes (RANS) simulations are compared with experiment. The capabilities and limitations are described, and future research needs identified.

: Three-dimensional shock wave turbulent boundary layer interactions caused by a fin-plate configuration were investigated experimentally and analytically. Wind tunnel tests were conducted at a Mach number of 3.71 and the interactions were studied at near full scale conditions by mounting one of several fins normal to the tunnel sidewall in the naturally turbulent, 6 inches thick sidewall boundary layer. Tests were conducted primarily with a sharp leading edge planar fin, although blunt and blunt swept planar fins were also used. The experimental data were used to develop new analytical and correlation procedures.

: The three year period covered in the subject report was a considerable shift from the previous years of work on shock wave turbulent boundary layer interactions. The earlier work concentrated on simple building block experiments and a search for fundamental understanding of the flow phenomena. In the subject research, most of the work on fundamentals for the simple configurations was stopped. The main emphasis for the first two years of the current program was on complex configurations and the final year was a close-out program on a new approach. The work on complex configurations was limited to two geometries which used the much studied single sharp fin interaction, Fig. 1, as the initial conditions. This shift in emphasis had two main purposes: (1) block experiments in more complex interactions required for applications and (2) to provide a more critical test of computation which, although giving the general characteristics for the building block experiments, did not give highly quantitative results. The primary activities for the first two years will be discussed in three major groupings: (1) and (2) Discussions of the two complex configurations, and (3) a description of the boundary layer conditions which are critical to the definition of the experiment and the check by computational fluid dynamics.