Numerical Simulation And Analysis On The Boundary Layer Under The Solitary Wave

The boundary layer under the solitary wave is an important model for studying underwater flow patterns under tsunami waves.In the article,firstly the theoretical analysis of the solitary wave and the boundary layer under the solitary wave are introduced,and then the governing equations are presented with a spectral multi-domain model method.Since the basic model can only calculate laminar flow field,thus the influence of KH instability of the flow field simply are analyzed,and a perturbation velocity function model to simulate and compute the boundary layer at high Reynolds are proposed.After that,the model adding the perturbation velocity function is analyzed,validated,and proposed the scope and limitations of the model: First,there is a gridindependence test between six different grids,and then the most suitable one is chosen.Secondly based on the division of flow pattern proposed by Sumer et al.,three flow patterns are simulated and analyzed,laminar flow,laminar flow with vortex tubes and transitional flow triggered by transverse vortex tubes separately;Thirdly,the shear stress distribution and the distribution of the shear coefficients were analyzed with eight different flow conditions.Finally,there are some following conclusions:(1)perturbation velocity function model can be used to calculate the flow pattern under test conditions,and predict higher Reynolds number flow condition cases;(2)the perturbation velocity does no function on laminar flow field and there are no vortex tubes can be found;(3)in the flow pattern of laminar flow with vortex tubes,the vortex tubes have the stream-wise velocity before they turn opposite,however this kind of movement lasts shortly,and would not do much effect on the flow condition;(4)with Reynolds number increasing,the stream-wise flow for vortex tubes continues a long time,which has an impact on the nature of the flow field,and thus the flow pattern becomes the unstable transitional flow period;(5)with the increase of the Reynolds number,the initial phase of flow instability will be ahead of time,but no earlier than38°;with the increase of Reynolds number,there will appear an exponential growth trend in turbulence;(6)there are different flow characteristics of maximum shear stress in acceleration and deceleration period,when in acceleration period,the shear stress coefficient is a straight line distribution in logarithmic coordinates,and the maximumshear stress occurs at-20°mostly;in deceleration period,the shear stress coefficient decreases with Reynolds number decreases,and there is a one peak distribution for the phase of generation of the maximum shear stress,and the peak is 97.5°.