Experimental flow study over a blunt-nosed axisymmetric body at incidence

摘要

The flowfield over a blunt-nosed cylinder was examined experimentally at a low subsonic speed for Re= 1.88 × 10{sup}5 and angles of attack up to 40°. Velocity measurements were carried out (employing a seven-hole Pitot tube) as well as wall static pressure and wall shear-stress measurements. Surface flow visualization was applied using liquid crystals and a mixture of oil-TiO{sub}2- For all the examined cases no flow asymmetries were found. For high angles of attack (20° and above) a separation "bubble" appears at the leeside of the nose area (streamwise flow separation). The basic feature of the circumferential pressure distribution at the after body area for these angles of attack is a plateau close to the suction peak and a fast recovery next to it. One streamwise vortex on each side of the symmetry plane is formed as well as a separation bubble about 90° far from this plane, where the cross-flow primary separation line is located. Each cross-flow primary separation line starts at the leeside nose area and moves towards the windward side along the cylindrical after body. The space between the two primary separation lines close to the wall is characterized by high flow fluctuations on the leeside, compared to the low fluctuations of the windward side.