Laboratory study on movement characteristics of a river plume using particle image velocimetry

Rivers are important passages for land-based materials transported to the sea, such as fresh water, sediment, pollutants, and nutrients. River discharge with land-based materials will form a river plume with a buoyancy flow. The river plume is subject to the interaction between nearshore runoff with seawater. In this study, the movement characteristics of the river plume are investigated based on particle image velocimetry (PIV) and the dye tracing method. It is found that the change of flow rate and environmental water density will shape the river plume pattern in both the plan view and the side view. The combined effect of flow rate and environmental water density could be described by the Froude number. The river plume has a free surface in the x-z plane and the horizontal velocity of the plume can be fitted with a 1/2 Gaussian distribution curve. The change of flow rate has little effect on the type of plume thickness curve, while the increase of environmental water density will change the thickness curve type of the river plume. The stable thickness of the river plume increases with the increase of the Froude number. The maximum value of turbulent kinetic energy is located in the middle layer, and the increase of the flow rate or the density difference leads to the increase in the turbulent kinetic energy.