The time evolution of a turbulent lock release gravity current, formed by a finite volume ofhomogeneous fluid released instantaneously into another fluid of slightly lower density, was studied byexperimental measureme...The time evolution of a turbulent lock release gravity current, formed by a finite volume ofhomogeneous fluid released instantaneously into another fluid of slightly lower density, was studied byexperimental measurements of the density structure via elaborate digital image processing and by a nu-merical simulation of the flow and mixing using a two-equation turbulence model. The essential fact thatthe gravity current passes through an initial slumping phase in which the current head advances steadilyand a second self-similar phase in which the front velocity decreases like the negative third power of thetime after release is satisfactorily presented by the laboratory observation. An overall entrainment ratioproportional to the distance from the release point is found by the numerical simulation. The renormal-ization group (RNG) k- ε model for Reynolds-stress closure is validated to characterize the gravitycurrent with transitional and localized turbulence.展开更多
The fourth-order Zakharov integral equation for surface gravity waves derived by Stiasshie and Shemer is modified to include the effect of shear flow. Using this new equation the class instability of a Stokes wave tra...The fourth-order Zakharov integral equation for surface gravity waves derived by Stiasshie and Shemer is modified to include the effect of shear flow. Using this new equation the class instability of a Stokes wave train in shear flow is studied. The effect of the vorticity on the instability is discussed, and a kind of new unstable regions has been found.展开更多
基金This work was supported by a grant from the University of Hong Kong, the National Key Projects for Basic Studies (No. G1999043605) the Trans-Century Training Foundation sponsored by the Education Ministry of China.
文摘The time evolution of a turbulent lock release gravity current, formed by a finite volume ofhomogeneous fluid released instantaneously into another fluid of slightly lower density, was studied byexperimental measurements of the density structure via elaborate digital image processing and by a nu-merical simulation of the flow and mixing using a two-equation turbulence model. The essential fact thatthe gravity current passes through an initial slumping phase in which the current head advances steadilyand a second self-similar phase in which the front velocity decreases like the negative third power of thetime after release is satisfactorily presented by the laboratory observation. An overall entrainment ratioproportional to the distance from the release point is found by the numerical simulation. The renormal-ization group (RNG) k- ε model for Reynolds-stress closure is validated to characterize the gravitycurrent with transitional and localized turbulence.
基金Project supported by the National Natural Science Foundation of China and by a research grant from the Groucher Foundation in Hong Kong.
文摘The fourth-order Zakharov integral equation for surface gravity waves derived by Stiasshie and Shemer is modified to include the effect of shear flow. Using this new equation the class instability of a Stokes wave train in shear flow is studied. The effect of the vorticity on the instability is discussed, and a kind of new unstable regions has been found.
