Study on the interaction of a submerged buoyant jet at different depth with on-coming linear waves

• Main Authors: Ying-Pin Lin, 林英斌
• Other Authors: Yang-Yih Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/86169209026976961117

博士 === 國立中山大學 === 海洋環境及工程學系研究所 === 101 === In order to evaluate the environmental and ecological impact of wastewater effluent discharge on coastal waters, it is important to know the physical changes (velocity, concentration, temperature) induced by these discharges. Most of the early research efforts deal with theoretical or experimental predictions of momentum jets, discharged at arbitrary angles into an infinite ambient through a single, circular, submerged pipe, subjected to buoyancy forces, uniform cross flow and ambient density stratification. In recent years, the number of papers on turbulent jets under water waves have increased due to the many outfalls built in shallow-water regions, where the wave effects become important. The incident waves can affect the hydrodynamics and mixing of turbulent plane jet. Therefore, it is important to develop an analytical formula to be used by industries and regulators for outfall design in the prediction of the jet motion under water. For this reason, this paper proposes to develop an asymptotic solution by the integral method to estimate the velocity distribution and boundary thickness under the interaction between buoyant jet and waves, which these physical characteristics in different water depths. A new theoretical solution for the dynamic characteristics of a buoyant jet due to oppositive small amplitude waves is presented. The conservation equations of mass and momentum are solved by the integral method which encompasses the Gaussian profiles of velocity. The action of waves is incorporated into the equations of motion as an external force and a new asymptotic solution is obtained to predict the trajectory, velocity distribution and boundary thickness of the buoyant jet over an arbitrary lateral cross section. It is found that the velocity along the centerline is inversely proportional to the ratio of the momentum of the wave and the buoyant jet. The averaged boundary width varies with the fluctuation of the boundary width, the distance from the orifice and the velocity correction function. Due to the motion of waves, the fluctuation of the boundary width is proportional to the wave steepness.