The coherent structures and the chaotic phenomena in the transition of the axisymmetric countercurrent mixing shear flow were investigated experimentally. Two kinds of self-excited oscillation modes could exist in the...The coherent structures and the chaotic phenomena in the transition of the axisymmetric countercurrent mixing shear flow were investigated experimentally. Two kinds of self-excited oscillation modes could exist in the axisymmetric countercurrent mixing shear flow. One is the shear layer self-excited oscillation mode corresponding to the high Reynolds number regime and the other is the jet column self-excited oscillation mode corresponding to the low Reynolds number regime in the case of the velocity ratio ranging from I to 1.5. Analyzing the auto-power spectrum, self-correlation-function and three dimensional reconstructed phase trajectory, the route to chaos through three Hopf bifurcations intercepted by an intermittence of the dynamical system corresponding to the axisymmetric countercurrent mixing shear flow was discovered when the velocity ratio is equal to 1.32.展开更多
The development of a simplified 2-D numerical model was described forwind-driven circulation in reservoir u-sing standard k-ε turbulence model to specify eddy viscositydistribution. The governing equations are transf...The development of a simplified 2-D numerical model was described forwind-driven circulation in reservoir u-sing standard k-ε turbulence model to specify eddy viscositydistribution. The governing equations are transformed and solved on variable vertical grids, whichallows refinement at the surface and bottom boundaries. The results of the model simulation for floware compared with analytical solutions for laminar and turbulent flows, experimental data in awind-flume and wind wave tank. The sensitivity analysis results show that use of large number ofdepth layers increases the accuracy for the bottom counter-current flow. Prediction of surface driftwas not very sensitive to surface grid refinement. The model was also applied to Baisha reservoirfor an assumed wind condition and showed to be able to simulate the general features of surfacedrift and return flow under variable flow depth. The model can serve as alternative means ofstudying wind-driven flow beside experiments. It also reduced the problem complexity associated with3-D circulation models while faithfully reproducing the drift and near bottom return currents.展开更多
文摘The coherent structures and the chaotic phenomena in the transition of the axisymmetric countercurrent mixing shear flow were investigated experimentally. Two kinds of self-excited oscillation modes could exist in the axisymmetric countercurrent mixing shear flow. One is the shear layer self-excited oscillation mode corresponding to the high Reynolds number regime and the other is the jet column self-excited oscillation mode corresponding to the low Reynolds number regime in the case of the velocity ratio ranging from I to 1.5. Analyzing the auto-power spectrum, self-correlation-function and three dimensional reconstructed phase trajectory, the route to chaos through three Hopf bifurcations intercepted by an intermittence of the dynamical system corresponding to the axisymmetric countercurrent mixing shear flow was discovered when the velocity ratio is equal to 1.32.
文摘The development of a simplified 2-D numerical model was described forwind-driven circulation in reservoir u-sing standard k-ε turbulence model to specify eddy viscositydistribution. The governing equations are transformed and solved on variable vertical grids, whichallows refinement at the surface and bottom boundaries. The results of the model simulation for floware compared with analytical solutions for laminar and turbulent flows, experimental data in awind-flume and wind wave tank. The sensitivity analysis results show that use of large number ofdepth layers increases the accuracy for the bottom counter-current flow. Prediction of surface driftwas not very sensitive to surface grid refinement. The model was also applied to Baisha reservoirfor an assumed wind condition and showed to be able to simulate the general features of surfacedrift and return flow under variable flow depth. The model can serve as alternative means ofstudying wind-driven flow beside experiments. It also reduced the problem complexity associated with3-D circulation models while faithfully reproducing the drift and near bottom return currents.
