Mr Cagatay Sabri Koksal (Istanbul Technical University)
A new research project, involving the construction of a modern, large, closed-circuit depressurized high-speed water tunnel to support the detailed hydro-acoustic, hydrodynamic, cavitation and flow visualization based experimental campaigns, has been started in Istanbul Technical University. The present paper covers the fundamental viscous flow computations concerning the design of the critical criterions of the tunnel, which includes the diffuser and test section. Incompressible Reynolds-Averaged-Navier-Stokes computations were performed for the analyses. The simulations were carried out considering the designed contraction and test section geometries from previous study on Hydrodynamic Design of Contraction, Diffuser and Elbow Geometries for a High Speed Cavitation Tunnel. In order to discharge flow from the test section with minimum energy loses, diffuser takes a critical place in downstream side of test section. Therefore, achievable minimum pressure loss is directly related with minimum flow separation region, also this flow phenomenon directly affects the acoustic performance of the tunnel with decreasing overall back noise level. Three steps expansion of diffuser was determined aiming minimum separation flow region in diffuser. The effect of several design parameters, such as the length and expansion ratio of the diffuser as well as each steps’ diffuser angle properties, were analyzed in order to determine the best diffuser geometry. The influence of the introduction of chamfer at corner of the cross section is also discussed.