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arXiv 2102.09617physics.flu-dyn
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考虑流固耦合的空化流动的一种高精度有限元框架

A robust and accurate finite element framework for cavitating flows with fluid-structure interaction

Suraj R. Kashyap, Rajeev K. Jaiman

摘要:

我们提出了一个统一的变分力学框架空化湍流和结构运动通过稳定的有限元公式。为了模拟空化现象中的有限传质速率,我们采用基于均相混合物的方法,通过唯象标量输运微分方程。稳定的线性化的质量连续性方程和标量输运方程的有限质量传递项推导出强大的和准确的实施。空化方程的线性化矩阵被赋予一个正性保持属性,以解决典型的两相空化流的高密度梯度所产生的数值振荡。所提出的配方是强耦合在一个分区的方式与不可压缩的三维Navier-Stokes有限元求解器,和非定常的问题是先进的时间使用全隐式广义$α$时间积分方案。我们首先验证的基准情况下,瑞利气泡崩溃的实施。我们证明了空化求解器的准确性和收敛性,通过比较数值解与解析解的瑞利-Plesset方程的气泡动力学。我们发现我们的求解器是强大的大时间步长和虚假振荡的压力场的情况下。空化流求解器与混合URANS-LES湍流模型耦合,该模型具有针对蒸汽存在进行校正的湍流粘度。我们验证了耦合求解器的非常高的雷诺数湍流空化流在NACA 0012水翼段。最后,在Arbitrary Lagrangian-Eulerian框架下求解该方法,研究了俯仰水翼段上的湍流空化流动,并对空化流动的特征(如再入射流和周期性空泡脱落)进行了耦合流固耦合分析。

英文摘要:

We present a unified variational mechanics framework for cavitating turbulent flows and structural motions via a stabilized finite element formulation. To model the finite mass transfer rate in cavitation phenomena, we employ the homogenous mixture-based approach via phenomenological scalar transport differential equations. Stable linearizations of the finite mass transfer terms for the mass continuity equation and the scalar transport equations are derived for robust and accurate implementation. The linearized matrices for the cavitation equation are imparted a positivity-preserving property to address numerical oscillations arising from high-density gradients typical of two-phase cavitating flows. The proposed formulation is strongly coupled in a partitioned manner with an incompressible 3D Navier-Stokes finite element solver, and the unsteady problem is advanced in time using a fully-implicit generalized-$α$ time integration scheme. We first verify the implementation on the benchmark case of Rayleigh bubble collapse. We demonstrate the accuracy and convergence of the cavitation solver by comparing the numerical solutions with the analytical solutions of the Rayleigh-Plesset equation for bubble dynamics. We find our solver to be robust for large time steps and the absence of spurious oscillations in the pressure field. The cavitating flow solver is coupled with a hybrid URANS-LES turbulence model with a turbulence viscosity corrected for the presence of vapor. We validate the coupled solver for a very high Reynolds number turbulent cavitating flow over a NACA0012 hydrofoil section. Finally, the proposed method is solved in an Arbitrary Lagrangian-Eulerian framework to study turbulent cavitating flow over a pitching hydrofoil section and the coupled FSI results are explored for characteristic features of cavitating flows such as re-entrant jet and periodic cavity shedding.

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