Wave-induced sediment transport is an important issue in coastal engineering. It is of fundamental significance to manifest the boundary layer behavior of nonlinear waves to accurately describe sediment transport in coastal areas, where wave forms are typically cnoidal or forward leaning rather than sinusoidal or symmetrical. In the present work, a novel expression of the near bed orbital velocity beneath forward-leaning waves is worked out. It is a series in which the coefficients are invariable for arbitrarily forward-leaning waves and just depend on the order of expansion. Based on this new expression, a theoretical solution of the laminar boundary layer beneath forward-leaning waves is derived by solving the governing equation via the method of variable separation. With this theoretical solution, it is convenient to acquire the velocity and shear stress (especially at the bottom) of the boundary layer beneath forward-leaning waves, which are different from those beneath sinusoidal waves as the degree of forward leaning increases. The phase lag between the bottom shear stress and the free-stream velocity is also analyzed, as well as the boundary layer thickness. In addition, the applicability of the present theory is discussed by comparing theoretical results with numerical results of different flow regimes.

波浪引起的沉积物运输是沿海工程中的重要问题。展现非线性波的边界层行为以准确描述沿海地区的沉积物传输具有根本意义，因为沿海地区的波形通常为正弦或前倾而不是正弦或对称。在目前的工作中，提出了前倾波作用下近床轨道速度的新表达。这是一个序列，其中系数对于任意前倾波都是不变的，并且仅取决于展开的阶数。基于该新表达式，通过变量分离法求解控制方程，推导出前倾波下方层流边界层的理论解。通过这种理论上的解决方案，可以方便地获取前倾波下方边界层的速度和切应力（特别是在底部），这与正弦波下方的边界层的速度和切应力不同，因为前倾程度增加。还分析了底部切应力和自由流速度之间的相位滞后以及边界层厚度。另外，通过将理论结果与不同流态的数值结果进行比较，讨论了本理论的适用性。