狭さくのある管内の脈動噴流により形成される渦輪の挙動 : 流体工学, 流体機械

抄録

The effect of pulsatile flow conditions on vortex behavior downstream of stenosed was studied experimentally by means of PTV methods. Phase mean velocity vectors in the downstream region of stenosed model with 89% area reduction were measured under the condition of sinusoidal pulsatile flow of mean Reynolds number Re= 100∼300 and Stokes number St =151∼410. It was observed that, in all conditions, vortex ring was produced with a trailing jet downstream of a stenosed during the period of increase in flow rate. In the case of higher St number, the second vortex ring was produced in contiguity with the leading vortex ring. In the case of higher Re number, a row of small vortex rings was produced along the shear layer of the trailing jet. These vortex rings were propagated downstream field with constant velocity, and breakdown was followed. The position of vortex ring breakdown was only influenced by St number, and the ratio of propagation velocity of vortex ring to mean velocity in a period at the stenosed was constant under the all conditions.