Improved prediction of flow separation in thrust optimized parabolic nozzles with FLUENT

Allamaprabhu, CY and Raghunandan, BN and Moríñigo, JA (2011) Improved prediction of flow separation in thrust optimized parabolic nozzles with FLUENT. In: 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2011, 31 July-3 August, 2011, United States.

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Abstract

Accurate numerical simulation of separated flows in contoured rocket nozzles is challenging because of the complex flow field phenomena, in which turbulence has a major role, that develops (shock-pattern, shock-boundary layer interaction, high-speed shear layers and vortices, fluctuations). Hence, turbulence modeling is a key aspect for success in the simulations, specif- ically for the accurate prediction of shock-induced flow separation, as it is stressed by the failure of many existing turbulence models intended for engineering applications. In this work, the assessment of turbulence mod- eling with the commercial CFD code FLUENT is investigated. Validation results with separated cold gas flow in Thrust-Optimized Parabolic noz- zle using the Spalart-Allmaras (SA) and the Shear Stress Transport (SST) turbulence models are compared in axisymmetric steady-state simulations carried out for the DLR-PAR subscale nozzle. The comparison with ex- perimental data shows that the standard SST model yields more accurate results than the SA model, albeit still predicts an earlier separation lo- cation to some extent. The present study suggests tuning of the major coeffcients in the eddy-viscosity equation of the SST model in order to improve the predictions, by matching the wall pressure distributions with the measurements. Simulations with a new modification included in the SST model have been carried out for the DLR-PAR nozzle. They reveal that the modified SST model predicts a closer location of flow separation, in better agreement with the experiments, for the range of nozzle pressure ratios analyzed.

Item Type:	Conference Paper
Publication:	47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2011
Publisher:	American Institute of Aeronautics and Astronautics Inc.
Additional Information:	The copyright of this article belongs to American Institute of Aeronautics and Astronautics Inc.
Keywords:	Atmospheric thermodynamics; Boundary layers; Computational fluid dynamics; Flow of gases; Flow separation; Forecasting; Propulsion; Rocket nozzles; Rockets; Shear stress; Turbulence models; Wall flow, Accurate prediction; Engineering applications; Nozzle pressure ratio; Shear-stress transport; Shock boundary-layer interactions; Steady-state simulations; Validation results; Wall-pressure distribution, Shear flow
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	25 Aug 2020 10:32
Last Modified:	25 Aug 2020 10:32
URI:	http://eprints.iisc.ac.in/id/eprint/66030

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