Theoretical analysis of internal solitary wave and its flow field in background flow

Abstract The influence of background flow on the vertical structure of concave internal solitary waves (ISW) in the continuous density stratification environment is studied by theoretical analysis method. The vertical inhomogeneous structures of ISWs in three cases of no background flow, linear gradient flow and linear shear flow are described by using the theoretical model suitable for describing completely nonlinear ISW under the condition of continuous stratification. The influence of background flow on the inhomogeneous vertical structure of ISW and its flow field is examined. The results show that the non-uniform vertical structure of internal solitary waves without background is controlled by the density disturbance which is characterized by the non-uniform distribution of density isopycnals, wave amplitudes and shear distribution of horizontal velocity vector along the vertical direction. The study reveals the influence of linear gradient flow and linear shear flow on the characteristic waveform, density field and velocity field of ISW. The research results are helpful to improve the understanding of the propagation and evolution characteristics of ISW within background shear flow in real ocean.