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Licentiate seminar

Experimental study of the turbulent flow in a plane asymmetric diffuser


Defendant Main Advisor Extra Advisor Date
Olle Törnblom Arne Johansson 2003-01-15

Opponent
Rolf Karlsson, Vattenfall Utveckling AB

Evaluation committee

Abstract

The separating turbulent flow in a plane asymmetric diffuser is investigated experimentally. The considered flow case is suitable for fundamental studies of separation, separation control and turbulence modelling. The flow case has been studied in a specially designed wind-tunnel under well controlled conditions. The velocity field has been mapped out with PIV and LDV techniques in order to determine all three velocity components. Knowledge of all velocity components allows the formation of several quantities of interest in turbulence modelling such as the turbulence kinetic energy, the turbulence anisotropy tensor and the turbulence production rate tensor. Pressures are measured through the diffuser. The measured data will form a reference database which can be used for evaluation of turbulence models and other computational investigations. A comparative study is made where the measured turbulence data are used to evaluate an explicit algebraic Reynolds stress turbulence model (EARSM). A discussion regarding the underlying reasons for the discrepancies found between the experimental and the model results is made. A simple form of separation control using vortex generators is tested with positive result.
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