Adjoint-based optimization of a source-term representation of vortex generators. (30th January 2018)

• Record Type: Journal Article
• Authors: Florentie, Liesbeth; Hulshoff, Steven J.; van Zuijlen, Alexander H.
• Is Part Of: Computers & fluids. Volume 162(2018)
• Page Start: 139
• Page End: 151
• Publication Date: 2018-01-30
• Subjects: Continuous adjoint method -- Source-term model -- Vortex generators -- Finite-volume method -- Computational fluid dynamics; Fluid dynamics -- Data processing -- Periodicals; 532.050285
• DOI: 10.1016/j.compfluid.2017.12.009
• Languages: English
• ISSNs: 0045-7930

Abstract

Highlights: A method to calculate optimal source terms for VG-induced flows is presented. Highly accurate shape-factor profiles can be obtained with optimized source terms. Accurate representation of VG-induced flows is possible on coarse meshes. Comparison with the jBAY model, of source term and result, is included. The viability of source-term simulations for VG-induced flows is demonstrated. Abstract: An optimization approach is presented that can be used to find the optimal source term distribution in order to represent a high-fidelity vortex-generator (VG) induced flow field on a coarse mesh. The approach employs the continuous adjoint of the problem, from which an exact sensitivity is calculated and used in combination with a trust-region method to find the source term which minimizes the deviation with respect to the reference velocity field. The algorithm is applied to an incompressible flow over a rectangular VG and VG pair on a flat plate and compared to results obtained with the jBAY-model and a body-fitted mesh simulation. The results indicate that a highly accurate flow, yielding only minimal errors with respect to the shape factor, circulation and vortex core, can be obtained on coarse meshes when adding a source term to only a limited number of cells. This approach therefore demonstrates the potential of source-term models to include the effects of VGs in computations of large-scale geometries. It also allows quantification of the achievable accuracy on a particular mesh and the calculation of the source term which is optimal for a specific situation. Furthermore, the optimization approach can be used to diagnose the deficiencies of an existing source-term VG model, in this work the jBAY model.