低雷诺数下的钉螺绕流特征数值模拟

研究钉螺在水流中的运动规律对于控制钉螺扩散具有十分重要的意义。通过开源流体力学计算软件OpenFOAM,使用非结构化的三角形网格拟合钉螺边界,采用有限体积法和PISO算法计算平面无限区域中黏性不可压缩流体下的钉螺绕流运动,模拟了低雷诺数下横向和纵向2种水流条件螺体后方尾流形态变化,详细描述了漩涡脱落过程等现象;对比分析不同条件下钉螺的阻力系数C_D、回流区长度L_w/D、斯特罗哈数St等的区别。研究结果表明:随着雷诺数的增加,钉螺的阻力系数逐渐减小,尾流形态呈现3种不同的形态,初步确定各流态转变的临界雷诺数的范围。该研究可为进一步掌握钉螺扩散规律、改进水利阻螺措施提供理论依据。

Numerical Simulation on Characteristics of Flow Past an Oncomelania at Low Reynolds Number

Researching the movement of oncomelania in water flow is of vital significance in controlling oncomelania diffusion. In this paper, the open source software OpenFOAM for computational fluid dynamics is adopted to calculate the water flow past an oncomelania in two-dimensional viscous incompressible unbounded domain.Triangular unstructured meshes are generated to simulate two streamwise flows past an oncomelania. The finite volume method and PISO (Pressure-Implicit with Splitting of Operators) algorithm are used for solving the time-dependent two-dimensional incompressible Navier-Stokes equations and the wake flow is simulated at low Reynolds number. The detailed information of flow quantities including coefficients of drag and lift, vortex shedding Strouhal number, and wake formation length varying with Reynolds number is obtained. Research results suggest that the drag coefficient of oncomelania declines gradually with the increase of Reynolds number; wake flow displays three different forms. The scopes of the critical Reynolds number which marked the transformation of flow behavior from steadiness to instability are preliminarily determined.The research could serve as a theoretical basis for improving oncomelania control.