【摘要】 利用计算流体力学软件FLUENT对磁致伸缩超声振动仪中超声空化发生特性进行数值模拟。通过考察流场内的绝对压力、气含率以及流体速度的变化,分析了超声空化的发生特性,并分析了相关参数对模拟结果的影响。结果表明:试样振动时,试样中间区域为主要空化区域。边缘区域发生空化的概率很小,但该区域始终受到试样周边流体绕流的作用,会对试样的两个边缘产生"磨削"破坏。在次边缘区域,水蒸气泡在快速流动的过程中溃灭,因而会对试样表面造成辐射状"划痕"。在影响参数中,密度和质量力的欠松弛因子的取值影响模拟结果的准确性;RNGk-ε模型对低压较敏感;非平衡壁面函数与增强壁面函数对贴近壁面处的流体压力变化更加敏感;在空化模型中,水的气化压力越高,流场内的高低压降幅越小,压力变化越稳定,而试样表面的气含率分布差异更大;不可压缩气体质量分数越大,试样表面压降幅度越小,试样表面的平均气含率越高。更多还原

【Abstract】 Simulation calculation of fluid flow in ultrasonic cavitation was performed by FLUENT through observing variation of Absolute pressure,vapor volume fraction and velocity magnitude in flow field.Mechanism of ultrasonic cavitation and influence factors were investigated.The results show that while sample vibrates,middle area in the sample is the primary cavitating area.Cavitation hardly ever occurs on the marginal area of sample.Passing water has an effect on the marginal area,and wear abrasion could happen to the marginal area of sample.On the sub-marginal area of sample,vapor bubbles collapse when flowing rapidly.Therefore,the sample surface appears radialized scratch.The under-relaxation factors of density and body force affect simulation results intensively.RNG k-ε model is sensitivity to low pressure.Non-equilibrium wall function and enhanced wall function are more sensitive to variation of near-wall pressure.The higher vaporization pressure is,the smaller variation of pressure in flow field is,and pressure changes more steadily,but variation of vapor volume fraction on sample is bigger.The bigger non-condensable gas mass fraction is,the smaller variation of pressure on sample is,and vapor volume fraction on sample is higher.更多还原