Three-dimensional simulations were used to model how a temperature difference between the incoming water and tank water influences the flow pattern and residence time in a detention tank. Buoyant, neutrally buoyant and negatively buoyant incoming jets were simulated. The simulations were compared with measurements for neutrally buoyant jets in a large-scale model of a detention tank (13 × 9×1 m). The results show that a negatively buoyant jet gives slightly less effective volume, defined as the time when 50% of added tracer has passed the outlet divided by the nominal residence time, than a neutrally buoyant jet. The flow pattern for a negatively buoyant jet at low densimetric Froude numbers consists of a current that travels along the bottom towards the outlet and a counter current at the surface towards the inlet, while the neutrally buoyant jet excites a surface jet with two large eddies on each side of the jet. This implies that the short-circuiting will decrease when a negatively buoyant jet at low densimetric Froude number occurs in the tank. The difference between the flow pattern excited by a buoyant jet and a neutrally buoyant jet is small.
Research Article|February 01 2006
Simulation of temperature influence on flow pattern and residence time in a detention tank
Åsa Adamsson, Lars Bergdahl; Simulation of temperature influence on flow pattern and residence time in a detention tank. Hydrology Research 1 February 2006; 37 (1): 53–68. doi: https://doi.org/10.2166/nh.2006.0005
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