Large eddy simulation of a sheet/cloud cavitation on a NACA0015 hydrofoil
Large eddy simulation of a sheet/cloud cavitation on a NACA0015 hydrofoil
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DOI：
10.1016/j.apm.2005.11.019
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发表时间：
2007-03
影响因子：
5
通讯作者：
G. Wang;M. Ostoja-Starzewski
中科院分区：
文献类型：
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作者：
G. Wang;M. Ostoja-Starzewski
建立了片云空化的单流体模型，并将其应用于NACA 0015翼型。首先，建立了基于三维非空化Navier-Stokes方程的弱可压缩流动大涡模拟（LES）模型。采用五次多项式曲线描述空化发生时密度系数比与压力系数的关系。采用MacCormack的显式校正格式，用有限体积法和时间推进法求解含空化泡团的Navier-Stokes方程。对NACA 0015翼型在攻角为4°、8°和20°，空化数σ=1.0、1.5和2.0，Re=106，网格划分为360×63×29时的三维流场进行了数值模拟。我们研究时间相关的片/云空化结构，所造成的相互作用的粘性物体，如旋涡，和空化气泡。在小攻角（4°）时，片空泡相对稳定，只是在积聚阶段尺寸发生振荡;在8°时，片空泡有脱离上翼型截面的趋势，云状空泡结构变得明显;在20°时，流与翼型前缘完全分离，出现涡空泡。与其他研究相比，主要是在先前的实验和模拟的流动模式的背景下进行的，证明了我们的模型的力量。总的来说，它可以快照云空化的崩溃，并允许研究流型及其不稳定性，如“新月形区域”。
A single fluid model of sheet/cloud cavitation is developed and applied to a NACA0015 hydrofoil. First, a cavity formation model is set up, based on a three-dimensional (3D) non-cavitation model of Navier–Stokes equations with a large eddy simulation (LES) scheme for weakly compressible flows. A fifth-order polynomial curve is adopted to describe the relationship between density coefficient ratio and pressure coefficient when cavitation occurs. The Navier–Stokes equations including cavitation bubble clusters are solved using the finite-volume approach with time-marching scheme, and MacCormack’s explicit-corrector scheme is adopted. Simulations are carried out in a 3D field acting on a hydrofoil NACA0015 at angles of attack 4°, 8° and 20°, with cavitation numbers σ=1.0, 1.5 and 2.0, Re=106, and a 360×63×29 meshing system. We study time-dependent sheet/cloud cavitation structures, caused by the interaction of viscous objects, such as vortices, and cavitation bubbles. At small angles of attack (4°), the sheet cavity is relatively stable just by oscillating in size at the accumulation stage; at 8° it has a tendency to break away from the upper foil section, with the cloud cavitation structure becoming apparent; at 20°, the flow separates fully from the leading edge of the hydrofoil, and the vortex cavitation occurs. Comparisons with other studies, carried out mainly in the context of flow patterns on which prior experiments and simulations were done, demonstrate the power of our model. Overall, it can snapshot the collapse of cloud cavitation, and allow a study of flow patterns and their instabilities, such as “crescent-shaped regions.”