A CFD study on Interaction of the Single Expansion Ramp Nozzle flow and the External Flow.
- Paper number
IAC-08.D2.5.6
- Author
Mr. Vamshi Togiti, Germany
- Coauthor
Dr. José Longo, Germany
- Coauthor
Dr. Patrick Gruhn, Germany
- Year
2008
- Abstract
Introduction A well researched technology for reusable launch vehicles are air-breathing engines. One major design issue, common to all air-breathing vehicle configurations, whether they are single-stage-to-orbit (SSTO) or two-stage-to-orbit (TSTO) vehicles or whether they are powered with subsonic (Ramjet) or supersonic combustion (Scram-jet), is the integration of the propulsion system into the airframe. One essential component of the propulsion system is the nozzle and that has to be designed carefully because of its large volume, its strong interaction with the vehicle and the large impact of nozzle efficiency on net thrust at high Mach numbers. Single Expansion Ramp Nozzles (SERN) are often considered as adequate solution because they offer good integration into the aircraft and have a certain self-adapt ability at off-design operation. The interaction of the nozzle flow, base flow and external flow is of major importance for aerodynamic stability of the complete hypersonic transportation vehicle. The detailed knowledge of the interaction can improve the performance of the vehicle. It is not always possible to understand the complete flow interaction only with experiments. A detailed computational fluid dynamics, CFD, study is also required in addition to the experiments. One of the objectives of the present activity is to study the interaction of nozzle flow with external flow at different nozzle pressure ratios (NPR) and at different temperatures of the exhaust plume and compare the computational results with experiments, which include pressure distribution along the expansion ramp and flap and the total pressure that is measured at a plane perpendicular to nozzle exit. Thus validated CFD tool will be used for ground to flight extrapolation, which is a major goal of the present work. Present computational study is based on the experimental work performed at the hypersonic blow-down facility H2K at DLR cologne as a part of on-going European Union project LAPCAT. In the experiment the free stream Mach number is varied from 5.3 and 7.0 and the total pressure at the entrance of the nozzle is varied based on the NPR. The Reynolds number based on the length of the wind tunnel model (0.6m) ranged from 1.5 million to 9.2 million. Computations are done using the DLR-Tau code[1], which is an unstructured compressible flow solver. The convective fluxes are approximated with AUSM type schemes and diffusion fluxes with a central scheme. Steady computations are done applying Spalart-Allmaras one-equation turbulence model. An advanced turbulence model Detached-eddy simulation [2] is also used for the cases in which flow separates from the nozzle ramp. Predicted pressures along the expansion ramp and the flap at different pressure ratios are in good agreement to the experiments. Total pressure distributions at the nozzle exit plane are also in good agreement with experiments, but the level is slightly under predicted. A three-dimensional flow field is observed inside the SERN flow as it was also observed in the experiments. Computations with hot gas are planned and can be ready for the final paper. References [1]. Mack, A., Hannemann, V. (2002). Validation of the Unstructured DLR TAU-Code for Hypersonic Flows, AIAA, 2002-3111. [2] Togiti, V.K., Luedeke, H. (2006). Computation of Supersonic Base Flow using Detached-Eddy Simulation. STAB/DGLR Symposium, Darmstadt, Germany.
- Abstract document
- Manuscript document
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