摘要
考虑瞬时压力脉动对空化初生的影响,采用动态亚格子应力模型对某高压柴油喷嘴内部瞬时流动进行大涡模拟。计算结果表明:喷孔入口分离形成的局部低压区内时均湍流脉动压力可达时均静压的2倍,两相流场时均空泡位置及形态与实验结果十分吻合,并与基于时均静压及湍流脉动压力预测的空化初生区域基本一致。分离剪切层失稳形成柱状涡并激发了转捩过程,在分离转捩区域柱状涡发生扭曲变形并产生强烈的瞬时压力脉动,从而导致了空化。喷孔入口倒角处理使得分离减弱,对分离转捩过程和空化初生具有抑制作用。
In order to take account of pressure fluctuation impact on cavitation inception,the instantaneous flow field inside a high-pressure diesel nozzle was investigated by a large eddy simulation method with a dynamic subgrid-scale stress model.The results show that time-averaged turbulent fluctuated pressure can reach up to twice as much as the time-averaged static pressure within the local low pressure area induced by inlet flow separation.The time-averaged location and shape of cavitation inception calculated by two-phase simulation is in a good agreement with the experimental results,which is also consistent with the cavitation inception zone predicted by time-averaged static pressure and turbulent fluctuated pressure.The instability of a separation shearing layer leads to the formation of a large-scale cylindrical vortex and triggers the laminar-turbulent transition process.Within the separation transition zone,the cylindrical vortex distorts,accompanied with intense instantaneous pressure fluctuation which results in cavitation.Further,the inlet filleting reduces a flow separation and has a suppressive effect on the transition process and cavitation inception.
出处
《工程力学》
EI
CSCD
北大核心
2013年第4期417-422,共6页
Engineering Mechanics
关键词
喷嘴
空化初生
流动分离
转捩
大涡模拟
nozzle
cavitation
flow separation
laminar-turbulent transition
Large eddy simulation
