波流作用下破波带内污染物输移扩散试验

Experimental study on transport and diffusivity of pollutant under action of waves and currents in surf zone

利用在破波带内连续采集的污染团图像,研究平直斜坡上规则波斜向入射时破波带内污染物的输移扩散特性。在介绍试验情况以及图像处理方法的基础上,获取污染团的形心点和离散程度,通过追踪形心点在水平二维空间的变化,线形拟合得到污染团在沿岸和垂直岸线方向的输移速度,并分析沿岸方向输移速度与时均沿岸流速最大值的关系;基于高斯扩散理论拟合得到垂直岸线方向扩散系数。利用该方法获得了5种波况下污染团水平方向输移速度、垂直岸线方向的扩散系数,并对其进行分析。结果表明:沿岸方向的污染物输移速度约为时均沿岸流速最大值的33%,垂直岸线方向输移速度及扩散系数分别在0.008~0.030 m/s和0.16×10^-3~2.6×10^-3 m^2/s范围内。

Based on the images of pollution mass continuously collected in the breaking zone,this paper studied the transport and diffusivity of pollutant in the surf zone under the oblique incidence of regular waves on the plane beach.Firstly,the experiment and image processing methods were introduced,and the centroid point and dispersion degree of the pollution mass were obtained.The transport velocity of pollution mass in the longshore direction and the cross-shore direction were obtained by following the change of centroid point in horizontal two-dimensional space and the alignment fitting.Then the relationship between the transport velocity in the longshore direction and the maximum time-averaged current velocity in the long-shore direction were analyzed.The cross-shore diffusion coefficient was estimated by assuming a Gaussian diffusion process in this study,and five horizontal transport velocities of pollution mass and five cross-shore diffusion coefficients were obtained and analyzed.The results show that the alongshore transport velocity of pollution mass is about 33%of the maximum time-averaged current velocity in the long-shore direction,and the transport velocity as well as the diffusion coefficient in the cross-shore direction is respectively within the range of 0.008-0.03 m/s and 0.16×10^-3-2.6×10^-3 m^2/s.