改进多松弛伪势模型模拟附壁空化泡溃灭演化和壁面润湿性机制的研究
SIMULATION OF THE COLLAPSE EVOLUTION OF ATTACHED CAVITATION BUBBLE AND STUDY ON THE MECHANISM OF WALL WETTABILITY BASED ON IMPROVED MULTI RELAXATION PSEUDO POTENTIAL MODEL
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摘要: 结合改进后的多松弛伪势模型, 使用格子Boltzmann方法对附壁空化泡溃灭演化过程进行了数值模拟及分析, 着重研究了壁面润湿性对附壁空化泡溃灭的影响规律. 首先, 对改进后的多松弛伪势模型开展了热力学一致性验证, 通过对比气液共存密度的数值解与解析解, 选取了满足热力学一致性需求的参数, 使得模型能够实现大密度比多相流动的数值计算; 然后, 对不同壁面润湿性条件下的附壁空化泡平衡接触角进行了数值模拟, 分析了壁面润湿性与附壁空化泡平衡接触角的关系, 分析表明: 随着壁面与流体相互作用强度的增大, 平衡接触角逐渐增大, 壁面润湿能力逐渐减弱. 进一步, 对附壁空化泡的溃灭问题进行建模, 处理了相应的边界格式, 完成了附壁空化泡溃灭过程的数值计算, 并分析了不同壁面润湿能力对附壁空化泡溃灭的影响规律; 当初始空化泡内外压差及形态相同时, 增强壁面疏水性缩短了空化泡溃灭的时间. 特别是, 壁面润湿性由亲水逐渐变为疏水时, 最大溃灭压力先降低后又逐渐升高, 而最大溃灭速度随着壁面疏水性的增强而持续升高. 研究结果揭示了壁面润湿性对附壁空化泡溃灭的影响规律, 为进一步抑制附壁空化泡溃灭的破坏效应及利用空化泡溃灭效应实现工程应用提供了理论指导.Abstract: Combined with the improved multi-relaxation pseudo-potential model, the lattice Boltzmann method was used to numerically simulate and analyze the evolution process of the collapse of attached cavitation bubble, with a focus on studying the influences of wall wettability on the collapse of attached cavitation bubble. First, a thermodynamic consistency verification was conducted on the improved multi-relaxation pseudo-potential model. By comparing the numerical and analytical solutions of gas-liquid coexistence density, the parameters that satisfy the thermodynamic consistency requirements were chosen to enable the model to achieve numerical computation of multiphase flows with a large density ratio. Then, the equilibrium contact angle of attached cavitation bubble was numerically simulated for different wall wettability, and the relationship between wall wettability and the equilibrium contact angle of attached cavitation bubbles was analyzed. The analysis show that the equilibrium contact angle gradually increases and the wall wetting ability gradually becomes weaken, as the interaction strength between the wall and the fluid increase. Further, the collapse process of attached cavitation bubble was modeled, and the corresponding boundary formats were processed to complete the numerical calculation of the collapse of attached cavitation bubble. The influence of different wall wetting conditions on the collapse of attached cavitation bubble was analyzed in detail. The analysis show that the enhancement of wall hydrophobicity shortens the collapse time when the initial pressure difference and morphology of the cavitation bubble are the same. In particular, as the wall wettability gradually changed from hydrophilic to hydrophobic, the maximum collapse pressure decreases first and then gradually increases, while the maximum collapse velocity continued to increase with the enhancement of the wall hydrophobicity. The results reveal the influence law of wall wettability on the collapse of attached cavitation bubble, providing theoretical guidance for further suppressing the destructive effects of the collapse of attached cavitation bubble and the engineering application of utilizing the cavitation bubble collapse effects.