透水鱼礁型潜堤内部流场及绕流特性模拟

Simulation Methods of Inner Flow Field and Flow Characteristics Induced by Perforated Reef-Type Breakwater

摘要:

为探究透水鱼礁型潜堤近区绕流结构的形态和水动力特性，通过水槽试验和数值模拟对均匀来流作用下单体鱼礁型潜堤近区绕流结构展开精细化研究。水槽试验采用粒子图像测速技术获得礁体内外的三维湍流特征，内部湍流在时均流场中呈现出横向对称的连续涡旋结构，揭示了鱼礁型潜堤表面的穿孔设计增强礁体内外水交换的流动机制。基于有限体积法建立了三维水槽数学模型，采用标准k-ε、重整化群k-ε、可实现k-ε和大涡模拟4种典型湍流模型模拟鱼礁型潜堤绕流流场，并根据试验结果评估各湍流模型的计算精度和效率。数值结果表明：大涡模拟方法对Navior-Stokes方程直接求解大涡的优势使其对礁体内部的流动分离现象预测最为精确，但模型计算效率最低；可实现k-ε模型对礁体结构内外的流速和涡旋分布的模拟基本反映了实测结果，且计算效率最高，是在计算能力有限时最适用于模拟透水鱼礁型潜堤的湍流模型。

关键词:鱼礁型潜堤;绕流;涡旋结构;粒子图像测速;湍流模型

Abstract:

Based on flume experiment and numerical simulation， a refined study on 3D flow induced by a reef-type submerged breakwater was conduced to observe the turbulence performance and hydrodynamic characteristics in uniform inflow. Particle image velocimetry （PIV） is experimentally employed to successfully capture the three-dimensional vortex structure inside and outside the reef and a continuous vortex structure with transverse symmetry in the time-average flow field， which reveals the ambient water exchange mechanism promoted by perforation of reef-type breakwaters. Further， a 3D numerical model with the same specifications of the PIV experiment is built using the finite volume method. An evaluation of the most frequently typically used four turbulence models， i.e. standard k-ε， renormalization group k-ε， realizable k-ε and large eddy simulation （LES）， on the flow field in vicinity of the perforated reef-type breakwater reef is presented. The results show that the inner flow separation predicted by LES is the most accurate due to the advantage of LES for directly solving the large eddy in the Navior-Stokes equation. However， the computational efficiency of the model is the lowest. The velocity and vortex structure near the reef block captured by realizable k-ε approximates the PIV flow visualization， and the computational efficiency is the highest， which is the most suitable turbulence model for the limited computed hardware equipment.

Key words:reef-type breakwater;detour flow;eddy structure;particle image velocimetry(PIV);turbulence model