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Article

Statistical modeling of vortex generators in pressure gradient boundary layers

Authors: von Stillfried, , Wallin, S.W., Johansson, A.V.J.
Document Type: Article
Pubstate: Published
Journal: The Sixth International Symposium on Turbulence and Shear Flow Phenomena, June 22 - 24, 2009, Seoul National University, Seoul, Korea
Volume:   
Year: 2009

Abstract

Modeling arrays of passive vortex generators (VGs) pairs, mounted in a flat plate boundary layer with adverse pressure gradient (APG) flow and generating streamwise counter rotating vortex structures is the object of this investigation. Usually, a sound computational fluid dynamics (CFD) investigation requires an adequate grid with a corresponding large number of grid points around such VGs in order to obtain an accurate solution of this flow case. This, in turn, leads to a time-demanding grid generation which often comes along with lots of practical challenges during the creation. An effective way to get around this time-consuming process is to introduce a way to model these flow separation devices statistically and, by that, to add their statistical physical effects to the governing equations rather than resolving their geometries in the computational grid. This approach for the modeling of passive VGs turbulent flow separation devices is presented for APG flow over a flat plate using the CFD code Edge by FOI, the Swedish Defence Research Agency. Moreover, computational results for three dimensional fully resolved VGs as well as experimental results without VGs are evaluated and compared to this statistical VG model approach. It is shown that flow separation can be successfully prevented by means of the statistical VG model.
The main objective of this work is to examine the capabilities of the statistical VG model in adverse pressure gradient (APG) flow over a flow plate. First, the clean flat plate with APG was investigated and adjusted in order to match experimental results, i.e. the wall pressure distribution along the streamwise coordinate. Then, the two dimensional (2D) VG model was introduced in the flow at the respective position as in experiments. Second, a parameter variation study was conducted, using different streamwise positions for the VG model forcing region. The results were then compared to experimental results without flow control devices and to three dimensional (3D) computations including fully resolved VGs.