Author(s): Samuel Ukpong Okon; Zhiguo He; Peng Hu; Yanan Chen
Linked Author(s): Zhiguo He
Keywords: Density currents; Collision dynamics; Turbulent mixing; Vertical Motion; Maximum rise height
Abstract: The collision and interaction between counterflowing bottom currents represent an important phenomenon in estuaries and oceans. Field observations have documented colliding gravity currents, yet inaccessible bottom locations and associated technical difficulties limit an in-depth understanding of the collision dynamics. In this study, we designed novel deep-ambient colliding gravity current laboratory experiments to understand the circulation pattern, quantify important collision parameters, and provide valuable insights into the implications of such interactions in nature. Advanced high-speed cameras and particle image velocimetry systems were deployed to capture the flow evolution and velocity fields of the colliding currents during the interaction process. Results revealed that the interaction between bottom-flowing gravity currents generates intense turbulent mixing and vertical motion of the mixed collision front. The deep-ambient experimental set-up allowed a new insight that the maximum rise height of the mixed collision front exceeds twice the height of the colliding currents, establishing an exchange pathway between the bottom and overlying waters. It also revealed a strong relationship between the maximum rise height of the collision front and the buoyancy ratio of the colliding currents. This paper highlights possible reasons the meeting point of two currents is energetic and biologically productive.
Year: 2024