Experimental and numerical investigation on a fully developed turbulent pipe flow over a semicircle orifice

The internal separated flow associated with remarkable mean secondary flow is investigated both experimentally and computationally. The computational investigation indicates that the commercially available RANS model group and LES provide obvious difference in terms of the prediction of the flow reattachment and recovery. On the other hand, some over-proportional magnitude of the velocity fluctuation across the mean flow direction is found by velocity measurement by stereo PIV. The recirculation region in either side of the orifice seems to be the source of the streamwise vortex that governs the development of the flow near the flow reattachment point. The considered flow serves as a useful test case for both RANS modeling and LES.