壁面に衝突する環状噴流における流れ場の特性

抄録

The flow field of an annular jet impinging on the wall was experimentally studied. Experiments were performed at the Reynolds number based on the jet exit velocity and the nozzle outer diameter of Re=67,000. Varying the distance from the nozzle to the wall, four types of flow pattern, from G1 to G4, were identified from the measurements of the central stagnation pressure and the radial pressure distribution. The velocity field between the nozzle and the wall was obtained by LDV and PIV. When the wall impingement distance is large (flow pattern, G1), a single forward stagnation point was formed at the central area of the wall by the merged jet after flowing around the re-circulation zone attached behind the nozzle inner body. For the intermediate impingement distance (flow pattern, G2), a reverse stagnation point which is formed by a large scale re-circulating flow between the nozzle and the wall, and a circular forward stagnation line which is formed by the jet impingement, were found to appear. It was also observed that the radial velocity fluctuation increased over a wide area of the impingement surface in the flow pattern of G2.