residence time calculation for a fluid in a reservoir
Computation of the residence time for fluid in a reservoir. There are two ways of computing the residence time of fluid in a reservoir. In both approaches the fluid flow is solved first, using the steady state solver. Than a transient simulation of species tracking follows. In the first approach, the tracer is supplied to the tank over a fixed time interval. The tracer concentration versus time is plotted at the reservoir exit and the resulting curve has a bell shape (Ecurve). The residence time is defined as the time corresponding to cover 10% of the surface area under the curve. This is also the experimental approach. In the second approach, the tracer is supplied continuosuly. At the reservoir exit c/c0 = f(t) is plotted where c0 is the tracer concentration at the inlet (Fcurve). The time corresponding to c/c0=0.1 is defined as the residence time. This approach is not applied in the experiments due to the high cost of the tracer which would have to be supplied continuously. 

