Influence of an entropy layer on the formation of Goertler vortices in a hypersonic flow
Final Report Abstract
This report presents the final status of the experimental research on the interaction of entropy layers with Görtler vortices in hypersonic ramp flows. A modular model consisting of five different leading edge with radii 0.05 (sharp), 0.5, 1, 3, and 5 mm and a ramp with variable ramp angle 0° - 30° is designed and manufactured to investigate the phenomenon. The separation bubble created due to shock wave / laminar boundary layer interaction, leads to curving of the shear layer especially in the reattachment region and results in Görtler vortex formation on the ramp. The spanwise heat flux variation due to Görtler vortices reduces with increasing bluntness and beyond a critical radius Görtler vortices are no longer visible. In other words, entropy layers have a stabilizing effect on the Görtler instability. The influence of different freestream Mach number and unit Reynolds number on the Görtler vortices is also studied. At the Aachen Shock Tunnel TH2, the reference case considered is a previously calibrated flow condition, which is at a Mach number 7.7 and a unit Reynolds number 4·10^6 m^-1. Two new tailored-conditions are calibrated, wherein in for the first case, the Reynolds number is held constant and the Mach number is raised to M∞ = 10, and for the second case, the Mach number is held constant and the Reynolds number is raised to Re∞,u = 8·10^6 m^-1. For the calibration campaign, an existing rake is refurbished and new parts are designed and manufactured for the same. At higher Mach number, even for sharp leading edge, the Görtler vortices exhibit very less spanwise heat flux variation in comparison to the reference case. Further, it shows that higher Mach number boundary layers are relatively stable. At higher Reynolds number, the Görtler vortices exhibit higher spanwise heat flux variation in comparison to the reference case. The highly-instrumented ramp model is equipped with newly developed quadthermocouples, thermocouples and low-cost pressure sensors. Apart from it, schlieren imaging and high-frequency infrared imaging have been applied to characterize the flow features. The experiments performed show that the occurrence of Görtler vortices is inevitable for hypersonic vehicles when the leading-edge radius, ramp-angle and freestream conditions are in the critical range. The tested flow conditions represent a typical hypersonic flight condition at an altitude of about 22, 27, and 30 km. The fundamental research has enabled more insights on the centrifugal instability and will provide a basis for Görtler instability analysis in presence of entropy layers. The high-quality and exhaustive experiments have not only aided in understanding the complex phenomenon, but will also provide scope for theoretical and numerical validation.
Publications
- (2017) Effect of Small Bluntness on Formation of Görtler Vortices in a Supersonic Compression Corner Flow. J Appl Mech Tech Phy (Journal of Applied Mechanics and Technical Physics) 58 (6) 975–989
Chuvakhov, P. V.; Borovoy, V. Ya.; Egorov, I. V.; Radchenko, V. N.; Olivier, H.; Roghelia, A.
(See online at https://doi.org/10.1134/S0021894417060037) - (2017) Experimental investigation of Görtler vortices in hypersonic ramp flows. Exp Fluids (Experiments in Fluids) 58 (10)
Roghelia, Amit; Olivier, Herbert; Egorov, Ivan; Chuvakhov, Pavel
(See online at https://doi.org/10.1007/s00348-017-2422-y) - 2015, “Direct Numerica Simulation of H personic Flows over Compression Ramps and Study of Appearing Görtler Vortices,” 8th European Symposium on Aerothermodynamics for Space Vehicles, ESA, Lisbon, Portugal
Klioutchnikov, I., and Olivier, H.
- 2016, “Joint Influence of High Entropy Layer and Goertler Vortices on Heat Transfer in Supersonic Compression Ramp Flow,” Comput. Therm. Sci., 8(6), pp. 543–553
Chuvakhov, P. V., Egorov, I. V., Olivier, H., and Roghelia, A.
(See online at https://doi.org/10.1615/ComputThermalScien.2016018947) - 2017, “Experimental Investigation of Görtler Vortices in Hypersonic Ramp Flows behind Sharp and Blunt Leading Edges,” 47th AIAA Fluid Dynamics Conference, AIAA, Denver, Colorado. Paper No. 2017-3463
Roghelia, A., Chuvakhov, P. V., Olivier, H., and Egorov, I.
(See online at https://doi.org/10.2514/6.2017-3463)
