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COMPRESSION OF A TUMBLING VORTEX: A LES AND PANS STUDY

Suad Jakirlic
Department of Mechanical Engineering Institute of Fluid Mechanics and Aerodynamics (SLA) / Center of Smart Interfaces (CSI) Technische Universitat Darmstadt Petersenstrasse 17, D-64287 Darmstadt, Germany

C.-Y. Chang
Institute of Fluid Mechanics and Aerodynamics / Center of Smart Interfaces Technische Universitat Darmstadt Petersenstr. 30 / 32, D-64287 Darmstadt, Germany

Branislav Basara
AVL LIST GmbH, Advanced Simulation Technologies, Hans List Platz 1, 8020 Graz, Austria

Cameron Tropea
Technische Univeritat Darmstadt

Sinopsis

In this paper we report on parallel LES (Large Eddy Simulation) and PANS (Partial-Averaged Navier-Stokes) study of the flow and turbulence in the process of the tumbling vortex generation and their response to the consequently imposed compression. Reference database was provided by Borée et al. (2002) who designed a square-piston compression machine to investigate experimentally the generation and breakdown of a tumbling motion. The computational approach whose validation represents the main objective of the present work is the so-called PANS method, proposed recently by Girimaji (2006), which provides a seamless transition from Unsteady RANS to the direct numerical solution (DNS) as the unresolved-to-total ratios of kinetic energy and its dissipation are varied.
Whereas the results obtained by both methods exhibit reasonable agreement of the mean velocity field with reference database during both the intake and compression strokes, the predicted turbulence enhancement during the compression stroke is somewhat retarded.