INTERNAL SOLITARY WAVE LOADS EXPERIMENTS AND ITS THEORETICAL MODEL FOR A CYLINDRICAL STRUCTURE

Abstract

Series experiments are conducted to investigate interaction characteristics of internal solitary waves with a cylindrical structure in a large-scale gravity type density stratified tank. Based on KdV, eKdV and MCC theories for internal solitary waves in a two-layer fluid of finite depth, a theoretical predicting model is established for internal solitary wave loads on a cylindrical structure, and the applicability conditions for these internal solitary wave theories are presented in order to apply such a load predicting model. It is showed that the horizontal load on the cylindrical structure due to the internal solitary wave consists of the horizontal Froude-Krylov, added mass and drag forces, respectively, which can be determined by Morison formula, while the vertical load mainly is the vertical Froude-Krylov force which can be obtained from the dynamic pressure induced by the internal solitary wave. Results for series experiments show that the added mass coefficient can be taken to be a constant value of approximately 1.0, and there exists an exponential function relationship between the drag force coefficient and the Reynolds number based on the velocity field induced by the internal solitary wave. Moreover, the numerical results based on the theoretical predicting model have good agreement with experimental ones. The investigation provides a practical theoretical model for predicting internal solitary wave loads on marine engineering structures due to internal solitary waves on the basis of the series experiment results.