Re = 10000下通过表面空气喷射实现的球体通气空化

中文摘要 AI 辅助

我们对亚临界雷诺数Re=10000下球体的通气空化进行了直接数值模拟（DNS）。该流动被建模为水和空气的均匀混合物，采用体积分数法（VOF）追踪界面。与以往数值研究不同，本研究明确考虑了表面张力。空气通过球体上的环形带注入，注入位置根据整体流动动力学选定，分为三类：前部（FR025，θ范围为18°至63°）、中部（MD025、MD050，θ范围为75°至104°）和后部（BK025，θ范围为120°至180°），注入流量系数C_q分别为0.2和0.4。注入位置显著控制空化的起始与稳定性，并改变前部和中部注入案例的流动分离情况。前部注入因剧烈的喷注产生不稳定的气泡状空化，使注入的空气破碎，与单相案例相比阻力增加约56%。相比之下，中部和后部注入产生稳定空化，具有不同的前缘动力学特性。中部注入案例中，喷注占主导，尽管流动分离延迟，但空化从注入区前缘脱落；对于后部注入，空化因空化形成诱导的逆压梯度而在注入区上游脱落，其特征为开尔文-亥姆霍兹不稳定性和凹坑形成。稳定空化表现出强烈的空气夹带，并通过凹入射流闭合。中部注入案例在C_q=0.2和0.4时分别实现35%和25%的阻力降低，而后部注入相对于单相案例实现最大46%的阻力降低。

英文摘要

We perform DNS of ventilated cavitation over a sphere at subcritical (Re=10,000). The flow is modeled as a homogeneous mixture of water and air, with the interface tracked using the volume-of-fluid method. Unlike previous numerical investigations, surface tension is explicitly included. Air is injected through a circular strip on the sphere at three locations selected based on the bulk flow dynamics: front (FR025, (18^\circ\leqθ\leq63^\circ)), mid (MD025, MD050, (75^\circ\leqθ\leq104^\circ)), and back (BK025, (120^\circ\leqθ\leq180^\circ)), with (C_q=0.2) and (0.4). The injection location strongly governs cavity inception and stability and alters flow separation in the front- and mid-injection cases. Front injection produces an unsteady bubbly cavity due to vigorous puffing, which fragments the injected air and increases drag by (\sim56%) relative to the single-phase case. In contrast, mid- and back-injection produce stable cavities with distinct leading-edge dynamics. In the mid-injection cases, puffing dominates and, despite delayed flow separation, the cavity detaches from the leading edge of the injection patch. For back injection, the cavity detaches upstream of the injection patch owing to the adverse pressure gradient induced by cavity formation. Kelvin--Helmholtz instabilities and divot formation characterize the back-injection cavity. Stable cavities exhibit strong air entrainment and close through a re-entrant jet. The mid-injection cases achieve (35%) and (25%) drag reduction at (C_q=0.2) and (0.4), respectively, while back injection yields a maximum drag reduction of (46%) relative to the single-phase case.

发表机构

• IITK（印度理工学院坎普尔分校）

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