平板喷气流场特性及气流量分配策略试验研究

Experimental study of flow field characteristics and air distribution strategies on a flat plate with air injection

为了探讨气流量分配对平板喷气流场特性的影响,在高速拖曳水池里开展了平板下表面喷气减阻试验,研究了气流量纵向和横向分配对平板减阻率和气层形态的影响规律。研究结果表明:平板下表面气液混合流的形态主要受航速和气流量影响,当无因次气流量系数Cq≤1.554时,混合流主要表现为气泡流;当Cq≥1.675时,混合流转变为过渡气层流;当Cq≥2.331时,混合流由过渡流转变为分层流。平板下表面的局部摩擦力减阻率在喷气口附近处为100%;改善喷气策略,在首部喷气装置左腔、中腔和右腔横向喷气比例为1∶4∶1时,平板下表面的气层覆盖率较高,减阻率可以达到60.65%;首部和中部喷气装置联合喷气并未使平板减阻效果有改善。

To investigate the effect of air flow distribution on plate flow field characteristics,we conducted a plate experiment with air injection in a high-speed towing tank. We studied the influence of air flow distribution in the longitudinal and transverse directions on drag reduction and the shape of the air layer. The results show that the shape of the air-water mixed flow under the plate surface is mainly affected by flow speed and air flow rate. When the non-dimensionalized air flow rate coefficient is equal to or less than 1.554（ Cq ≤1.554）,the mixed flow will be mainly bubbly flow; when Cq ≥1.675,the mixed flow becomes transitional air flow that is both bubbly and stratified; and when Cq ≥2.331,the mixed flow becomes air-water stratified flow. We obtained a local friction drag reduction of 100% at the lower surface of the plate near the injection. We found the drag reduction to reach 60.65%by improving the air injection strategy,and the transverse air injection ratio in the left,middle,and right chambers to be 1 ∶ 4 ∶ 1 in the header air injection device. We found the joint air injection of the header and central device to make no contribution to drag reduction.