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Numerical Simulation of the Roughness Effects on the Asymmetric Flow over Axisymmetric Bodies JIMENEZ-VARONA Jose1, LIANO Gabriel2 INTA, Carretera de Ajalvir Km. 4,5 28850 Torrejon de Ardoz, Madrid, Spain 1 jimenezj@inta.es , 2 liagno@inta.es CASTILLO Jose L.3, GARCIA-YBARRA Pedro L.4 Universidad Nacional de Educacion a Distancia, UNED, Senda del Rey s/n, 28040 Madrid, Spain 3 jcastillo@ccia.uned.es , 4 pgybarra@ccia.uned.es Abstract The flow at high angles of attack over axisymmetric configurations is not symmetric. The mechanism that triggers this asymmetry may be the combination of a global (inviscid nature) instability and a convective instability due to irregularities of the configuration [1]. Numerical simulations with the unsteady Reynolds Averaged Navier-Stokes equations (URANS) have been conducted for an ogive cylinder configuration at low subsonic flow and high angle of attack. There is abundant experimental information for this configuration [1, 2]. For the numerical prediction of the flow about a missile type configuration, how the body surface is modelled is very relevant; especially the tip zone of the body. Two grids were built up. One structured axisymmetric grid -inherently symmetric- and one unstructured grid, not symmetric, with irregularities that resemble a rough model. Previous studies [3] conducted at a high angle of attack with Reynolds Stress Turbulence models (RSM) showed asymmetric flow with no orientation angle effects for the structured grid (symmetric grid), while there were important differences in the global forces if the unstructured grid was used. This grid has some kind of numerical roughness which resembles a rough model. But, there were difficulties in the simulation: the observed damping of the forces in the rear part of the body were not calculated accurately with the RSM model. And the unsteady flow detected in this part was also not predicted. An alternative calculation using an advanced turbulence model has been carried out. The Scale Adaptive Simulation (SAS) model developed by Menter and Egorov [4] has demonstrated to be superior to other typical eddy-viscosity or Reynolds Stress turbulence models. The theoretical results are in consonance with the experimental data and two regions of flow, one steady flow region in the forebody, and one unsteady flow region in the rear are detected as observed in different experiments [5]. References [1] P. Champigny, High Angle of Attack Aerodynamics, AGARD R-804 Special Course on Missile Aerodynamics, June 1994, pp. 5-1-5-19. [2] J.R. Deane, An Experimental and Theoretical Investigation into the Asymmetric Vortex Flow Characteristics of Bodies of Revolution at High Angles of Incidence in Low Speed Flow GARTEUR TP-019, Final Report of GARTEUR AG04, July 1984. [3] Jimenez J., Liano G., Castillo J.L., Garcia-Ybarra P.L., Roll Angle Effects on the Asymmetric Flow over Axisymmetric Bodies, 8th EUCASS Congress, European Conference for Aeronautics and Space Sciences, paper 333, July 2019, Madrid, Spain. [4] F.R. Menter and Y. Egorov, The Scale-Adaptive Simulation Method for Unsteady Turbulent Flow Predictions. Part I: Theory and Model Description, Flow Turbulence Combustion (2010), 85:113-138, June 2010, https://doi.org/10.1007/s10494-010-9264-5. [5] S.E. Ramberg, The Effects of Yaw and Finite Length upon the Vortex Wakes of Stationary and Vibrating Circular Cylinders, Journal of Fluid Mechanics, Vol. 128, pp. 81-107, 1983, https://doi.org/10.1017/S0022112083000397 |
