Comparative study of a vertical round jet in regular and random waves

Abstract

The hydrodynamic behaviors of a vertical round jet in regular and random waves are comparatively investigated. The regular and the random waves are chosen based on the concept of equivalent energy density and energy flux. The experimental study is first carried out to compare the lateral profiles of jet mean axial velocity at various vertical levels. The results show that, under the present experimental conditions, the phenomenon of “twin peaks” appears in the regular waves, but virtually does not exist in the corresponding random waves. This results in a lower axial velocity along the centerline for the jet in the regular waves. A large eddy simulation (LES) model is subsequently developed to quantify the difference of jet half-width under the same wave conditions as those in the laboratory. The numerical results show that the jet in the random waves has a larger jet half-width than that in the regular waves, which is consistent with the visual observations in laboratory experiments. More scenarios of the jet in different regular and random waves are numerically investigated and the results show that the “twin peaks” may also appear under the condition of random waves, but requiring a larger wave-to-jet momentum ratio.