成層流体中を進行する重力流に関する可視化実験と計算

抄録

The structure of a gravity current advancing into a stratified fluid is investigated in the experiment and the computation of a lock-exchange flow. A finite volume of homogeneous fluid was released instantaneously into stratified fluid of constant density gradient in an open rectangular channel when a lock gate was opened. Visualization experiments were made by the shadowgraph method and with dye to trace the gravity currents of the homogeneous and stratified fluides. The homogeneous fluid released into stratified fluid advances at constant speed at the initial stage at the depth where the density of the released fluid coincides with that of the stratified fluid. At the same time the stratified fluid separated to upper and lower side advances in the opposite direction. In the following stages, several patterns of the penetration and the advancement of the fluids have been observed according to the density difference ratio. To study the effect of the stratification and the structure of the gravity current, the computation was also made in the same condition as the experiments. The incompressible Navier-Stokes equation for an inhomogeneous fluid together with the transport equation for solute was solved by the finite volume method. The computational results show the same patterns of the penetration as the experiment, and it is confirmed that the advancing gravity current changes remarkably the shape and the structure according to the density difference ratio.