The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and c...The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and circumferential correlation were obtained in the spacing range from 1.25 to 6.0. The spatial correlation of pressures of two pressure taps on two different cylinders at the same azimuth was investigated as well. Owing to different flow patterns in various arrangements and spacing, these correlation curves of pressure show different distributions. The lift fluctuation can be estimated qualitatively from the circumferential coefficient curve with the knowledge of the rms pressure distribution. Some critical spacing for each arrangement were found that the flow regimes and the corresponding pressure correlation take a sudden change. Flow interference between cylinders in each arrangement was also discussed with various flow regimes.展开更多
The conjugate flows over a step with the height h_0, which might be positive or negative, was studied in a three-layer fluid and the coupled nonlinear equations were derived, with which the effects of varying height ...The conjugate flows over a step with the height h_0, which might be positive or negative, was studied in a three-layer fluid and the coupled nonlinear equations were derived, with which the effects of varying height h_0 on the existence and evolution of conjugate flows were examined. It is concluded that the conjugate flow is sharply sensitive to the thickness of fluid layers and its characteristics alters remarkably due to the existence of the step. As the flow climbs up a step (h_0>0), the conjugate flow with a convex lower interface and a concave upper interface is allowed to appear, while the flow with the concave lower interface or the simultaneous concave interfaces will be depressed. As the flow goes down a step (i.e., h_0<0), on most occasions only one kind of conjugate flow could exist, which prossesses the form with the simultaneous convex interfaces and will disappear rapidly with the increase of the step depth.展开更多
This paper presents a method for solving Lagrangian version of governing equations that allows boundary conditions at the free surface to be satisfied exactly, which is a three-dimensional generalization of a method f...This paper presents a method for solving Lagrangian version of governing equations that allows boundary conditions at the free surface to be satisfied exactly, which is a three-dimensional generalization of a method first put forward by Stoker. Analytical expressions of nonlinear hydrodynamic pressure up to the third order and of free surface displacement up to the fourth order of an accelerating cylindrical tank were obtained. Here only the motions of objects in their early stage after initial impulses was considered. As a justification of the method, the important special case when the ratio of tank diameter to fluid depth tends to infinity was taken as an example, which shows that the linear hydrodynamic pressure obtained agrees completely with Westergaard or von Karman's classical result.展开更多
文摘The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and circumferential correlation were obtained in the spacing range from 1.25 to 6.0. The spatial correlation of pressures of two pressure taps on two different cylinders at the same azimuth was investigated as well. Owing to different flow patterns in various arrangements and spacing, these correlation curves of pressure show different distributions. The lift fluctuation can be estimated qualitatively from the circumferential coefficient curve with the knowledge of the rms pressure distribution. Some critical spacing for each arrangement were found that the flow regimes and the corresponding pressure correlation take a sudden change. Flow interference between cylinders in each arrangement was also discussed with various flow regimes.
文摘The conjugate flows over a step with the height h_0, which might be positive or negative, was studied in a three-layer fluid and the coupled nonlinear equations were derived, with which the effects of varying height h_0 on the existence and evolution of conjugate flows were examined. It is concluded that the conjugate flow is sharply sensitive to the thickness of fluid layers and its characteristics alters remarkably due to the existence of the step. As the flow climbs up a step (h_0>0), the conjugate flow with a convex lower interface and a concave upper interface is allowed to appear, while the flow with the concave lower interface or the simultaneous concave interfaces will be depressed. As the flow goes down a step (i.e., h_0<0), on most occasions only one kind of conjugate flow could exist, which prossesses the form with the simultaneous convex interfaces and will disappear rapidly with the increase of the step depth.
文摘This paper presents a method for solving Lagrangian version of governing equations that allows boundary conditions at the free surface to be satisfied exactly, which is a three-dimensional generalization of a method first put forward by Stoker. Analytical expressions of nonlinear hydrodynamic pressure up to the third order and of free surface displacement up to the fourth order of an accelerating cylindrical tank were obtained. Here only the motions of objects in their early stage after initial impulses was considered. As a justification of the method, the important special case when the ratio of tank diameter to fluid depth tends to infinity was taken as an example, which shows that the linear hydrodynamic pressure obtained agrees completely with Westergaard or von Karman's classical result.
