Determination of the discharge coefficient through vent driven by a non-Boussinesq plume in an emptying filling box

School of Civil and Surveying & Mapping Engineering, Jiangxi University of Science and Technolog, Ganzhou, China

^* Corresponding author: jxlgliuyang@163.com

Abstract

The effect of high buoyancy forces due to density contrast between the fluids on either side of the vent on the discharge coefficient C_d is taken into account in the laboratory. Salt water experiments are conducted at small scale in a large fresh water tank with saline to generate buoyancy force. In non-Boussinesq cases, a larger discharge parameter Γ_d at the vent may make plume-like flow contract further with a smaller value of the discharge coefficient. A nearly twofold time in the non-dimensional form for draining light fluid fully out of the space is observed comparing with time predicted with a constant value of C_d = 0.6 for simple draining flows. A displacement flow theoretical model with virtual source correction at the initial position of an internal source is developed to reveal a time-dependent movement of the layer interface, and the oscillatory amplitude of the interface overshooting during the transient period is found to depend on the two dimensionless geometrical parameters Λ and Θ.