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EXPERIMENTAL INVESTIGATION OF SEPARATING FLOW IN A PLANE ASYMMETRIC DIFFUSER

Olle Tornblom
Department of Mechanics, Royal Institute of Technology, Osquarsbacke 18, SE-100 44 Stockholm, Sweden

Bjorn Lindgren
Department of Mechanics, Royal Institute of Technology, Osquarsbacke 18, SE-100 44 Stockholm, Sweden

Arne V. Johansson
Linne FLOW Centre, Dept. of Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

Аннотация

The flow in a plane asymmetric diffuser has been studied experimentally and compared to an explicit algebraic Reynolds stress model (EARSM) computation (Gullman-Strand (2002)). The inlet flow is fully developed turbulent channel flow and a separation bubble is formed on the inclined wall. The mean separation and reattachment points are found, in the experiment, at 9 and at 31 inlet channel heights respectively. The model under-predicts the size of the separation bubble, this is attributed to an over-estimation of the wall normal turbulence component in a region close to the diffuser inlet. By analyzing the balance between the production and dissipation of turbulence kinetic energy we find that the predicted dissipation is too large. Hence, a better model for the production term in the transport equation for the turbulence time-scale-determining quantity (e.g. ε or ω) might be a key to better agreement.