Numerical simulations of constant-influx gravity currents in confined spaces: Application to thermal storage tanks

This study uses Computational Fluid Dynamics (CFD) to investigate numerically the flow phenomena in the intrusion region of a thermal storage water tank during discharge. The early times of the discharging process have significant effect on the thermal mixing and the associated energy losses. A detailed time-evolution of the flow and temperature fields inside the tank was obtained for a range of relevant Froude (Fr) numbers. Parameters such as the thermocline thickness (δ), the entropy generation rate (S˙g) and the thermal mixing factor (κ) were calculated to quantify the mixing mechanism in the tank. Authors chose several alternative discharging scenarios where the Froude number (Fr) varied between 0.05 and 2.00, a range which corresponds to typical discharging conditions in real applications involving water storage tanks. The gravity currents (GCs) developing as the incoming cold fluid flows along the floor of the tank, their subsequent reflection on the opposite vertical wall and the interaction between the reverse flow and the incoming flow were analyzed and correlated to δ, S˙g and κ.