基于虚拟边界力法的弧板式防波堤结构水动力特性研究

The impact wave forces on the upstream and downstream of arc-shaped plate breakwater are large, and also pose a threat to the stability and security of the breakwater. At present, the studies on the interaction between waves and such irregular structures are commonly based on the theory of potential flow, which cannot describe the water viscosity resulting in the limitations of its application. Meanwhile, the body-fitted grid method based on Navier-Stokes (N-S) equations would reduce the computational efficiency of the numerical model. The present research project intends to use the virtual boundary force (VBF) method to establish the numerical model of the interaction between waves and complex geometric shape structures based on the N-S equations. In this model, the free surface of the fluid is tracked with the volume of fluid (VOF) method and the interaction between waves and structures is simulated by the VBF method. The established numerical model will be verified by experimental results. And then, the relationships between wave transmission characteristic, wave induced pressures and the flow field structures around the arc-shaped plate breakwater are discussed to reveal the interaction mechanism of wave and arc-shaped plate breakwater. On the basis of this, a new arc-shaped perforated plate is proposed to get good effect of wave attenuation. Its hydrodynamic characteristics will be discussed and some useful results will be presented which should provide scientific basis and technical support for the design and application of such plate barrier structures. At the same time, the VBF-based numerical model established by the present project could provide a new research method for the interaction between waves and coastal irregular structures.

弧板式防波堤受到波浪作用时，迎浪侧与背浪侧均受到较大的冲击荷载，对结构的整体稳定与安全构成威胁。目前波浪与此类不规则结构物相互作用的研究多基于势流理论，无法分析水波粘性作用，应用范围受到限制；采用基于N-S方程的贴体网格方法则影响数值模型的计算效率。因此，本项目拟基于N-S方程采用虚拟边界力法建立波浪与复杂几何外形结构物相互作用的数值模型，应用流体体积法追踪流体自由表面，利用虚拟边界力法模拟波浪与结构物之间的相互作用，通过试验结果验证数值模型的准确性；然后，利用所建立的模型，讨论弧板式防波堤的消浪性能、受力特性及流场结构之间的关系，揭示波浪与弧板式防波堤的作用机理；在此基础上，提出一种消浪效果优良的局部开孔式弧板结构并探讨其水动力特性，为此类新型防波堤结构的设计和应用提供依据。本项目所建立的基于虚拟边界力法的数值模型可为波浪与海岸不规则结构物的相互作用提供一种新的研究手段。

针对现有波浪与不规则结构物作用的数值模型存在的问题，本研究基于N-S方程构建了波浪与板式透空堤相互作用的数值模型，利用理论解、前人研究结果验证所建数值模型。通过对平板式、上弧板式和下弧板式三种透空堤开展的消浪性能数值研究发现，下弧板式透空堤在不同潜深条件下的波面高程均为最低；98%工况情境下，下弧板式透空堤的透射系数Kt和反射系数Kr均为最小，相对于平板式和上弧板式透空堤其Kt最高可分别减小约40%和31%，反射系数Kr最高可分别减小约40%和43%；在相对板宽0.19~0.45范围内，下弧板式透空堤对波浪的能耗系数相对于平板式透空堤提高11.7%~36.7%；下弧板式透空堤的耗散波能占比最大，较平板式透空堤增大31.15%~42.31%，较上弧板式透空堤增大42.04%~53.68%。. 通过物模试验和数值模拟研究了双弧板式透空堤的消浪性能、结构受力和流场特性，并据此探讨了该新型结构的消浪机理。随着相对板宽的增大，透射系数减小、反射系数略有增加。波高每增大4cm，透射系数约增大11%。当d/h=0.05，相对波高H/h为0.10和0.17时的反射系数差异较大，相对波高为0.17时的反射系数较相对波高为0.10时最大减小量为39.6%。波浪压力在弧板上下表面的分布特征差异显著，下表面不同测点的正负压力的变化相对平稳，当d/h=0.05，弧板下表面正负压力绝对值的差值仅在0.06~0.21kPa之间。弧板式透空堤所受垂直波浪力较平板式透空堤显著增大。弧板式透空堤迎浪向与背浪向的流场分布差异显著，其背浪向有显著的漩涡产生。. 本项目研究成果在《Ocean Engineering》《China Ocean Engineering》《Journal of Coastal Research》《Marine Pollution Bulletin》《Atmosphere-Ocean》《船舶力学》《海洋工程》《海洋湖沼通报》等国内外期刊发表学术论文15篇，获得国家授权专利13件，登记软件著作权4件，培养研究生9名。