极平缓岸坡上的底部波能损耗

Dissipation of wave energy on very mild slope

本文分别分析与计算了波浪在粉沙质海床、沙纹海床和淤泥质海床上传播时波高的衰减。研究表明 ,波浪在粉沙质海床上传播的渗透损耗可以忽略不计 ;波浪在沙纹海床上传播的底摩阻损耗比在平滑粉沙底床上传播的损耗大 ,前者的摩擦系数约比后者值大一个数量级。波浪在淤泥质海床上传播的能量损耗最大 ,其损耗机理也很复杂。为了便于比较 ,将波浪在淤泥质海床上的衰减换算成等价摩擦系数。并运用宾汉模型和波浪作用通量守恒原理计算了波浪在极平缓淤泥质海滩上传播时的衰减及沿程等价摩阻系数。与连云港波浪观测资料对比 ,符合较好。此外。理论计算发现沿程等价摩阻系数与水深关系较大 ,由深水至浅水逐渐增大 ,且水深越浅 ,增速越快。

This paper presents the analysis and calculation of wave attenuations when waves travel on sand bed, sand ripple bed and muddy bed, respectively. The study shows that (1) porous dissipation of wave energy may be neglected on sand bed; (2) wave attenuation due to the friction of sand ripples is one order larger than that of flat sand bed and (3) the energy loss of waves propagating on muddy bed is the largest. The equivalent coefficients of friction were calculated in order to compare the solutions with those of bottom-friction model. Wave attenuations were also computed by using the Binham model and the principle of conservation of wave flux on very mild muddy slope. The calculated results coincide well with the measured data at the Lian-yungang Wave Observation Station. Theoretical prediction proves that the equivalent coefficients of friction strongly rely on water depth, and the equivalent coefficient of friction increases with decreasing depth.