Experimental and numerical study on onset of inflow in near field of buoyant jet at low Froude number

In the present paper, the onset of inflow in the near field of a vertical buoyant jet issuing from a square duct is studied by experimental flow visualization and numerical simulation. The experimental critical condition for the onset of inflow is obtained from the scanning LIF visualization in the near field of the buoyant jet at various combinations of Froude numbers and Reynolds numbers. The experimental result shows that the critical Froude number increases with an increase in Reynolds number of the buoyant jet. The critical condition is also examined by numerical simulation based on the Navier-Stokes equation and energy conservation equation, under the assumption that the flow separation occurs at the duct exit. The main feature of the inflow observed by experiment is well reproduced in the numerical results.