New 2-D horizontal free-surface-flow models with applications for water waves

• Published in: Journal of fluid mechanics 2024-11, Vol.999, Article A32
• Main Authors: Yang, Zhengtong, Liu, Philip L.-F.
• Format: Article
• Language: English
• Subjects: Accuracy; Agreements; Algorithms; Approximation; Bathymeters; Bathymetry; Boundary conditions; Boussinesq approximation; Boussinesq equations; Continuity equation; Deep water; Experiments; Finite difference method; Free surfaces; Initial conditions; JFM Papers; Linear waves; Mathematical models; Momentum; Numerical models; Polynomials; Regular waves; Shallow water; Shape functions; Shoaling; Shoals; Stokes waves; Two dimensional flow; Velocity; Water circulation; Water column; Water currents; Water depth; Water waves; Wave groups; Wave propagation; Wave properties; Wavelength
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2024.604

The depth-integrated horizontal momentum equations and continuity equation are employed to develop a new model. The vertical velocity and pressure can be expressed exactly in terms of horizontal velocities and free-surface elevation, which are the only unknowns in the model. Dividing the water column into elements and approximating horizontal velocities using linear shape function in each element, a set of model equations for horizontal velocities at element nodes is derived by adopting the weighted residual method. These model equations can be applied for transient or steady free-surface flows by prescribing appropriate lateral boundary conditions and initial conditions. Here, only the wave–current–bathymetry interaction problems are investigated. Theoretical analyses are conducted to examine various linear wave properties of the new models, which outperform the Green–Naghdi-type models for the range of water depth to wavelength ratios and the Boussinesq-type models as they are capable of simulating vertically sheared currents. One-dimensional horizontal numerical models, using a finite-difference method, are applied to a wide range of wave–current–bathymetry problems. Numerical validations are performed for nonlinear Stokes wave and bichromatic wave group propagation in deep water, sideband instability, regular wave transformation over a submerged shoal and focusing wave group interacting with linearly sheared currents in deep water. Very good agreements are observed between numerical results and laboratory data. Lastly, numerical experiments of wave shoaling from deep to shallow water are conducted to further demonstrate the capability of the new model.