Experimental study of horizontal heated buoyant jets in a linearly stratified ambience

Horizontal warm buoyant jets injecting into a linearly stratified ambience are common in lakes, estuaries, and oceans. Dynamic features and potential surface temperature signatures of heated buoyant jets are experimentally investigated using particle image velocimetry and an infrared camera. Results reveal that when heated jets are completely underwater, the flow evolution can be classified into the horizontal regime, ascending regime, and collapsing regime, respectively. The maximum rise height and the neutral height both increase linearly with the increasing jet length scale. Based on this relationship, an equation is developed to predict the surface impingement of a horizontal heated buoyant jet. If the surface impingement occurs, staggered vortexes and large meanders caused by mixing between the jet and the free surface are observed on the surface temperature maps. Furthermore, surface temperature fluctuation fields are decomposed using the Karhunen-Loeve method, the first four eigenmodes appear to capture the root mean square temperature fluctuations and the features correlated with the swirling vortexes. In the turbulent kinetic energy budget, mean-flow convection is found to be mainly balanced by turbulent transport. As the heated jet propagates downstream, more kinetic energy is transferred into potential energy rather than into turbulent energy.