Circular Cylinder In Fluid Research Articles

Oscillations of a Cylinder beneath an Ice Cover in the Neighborhood of a Vertical Wall

The solution to the problem of oscillations of a circular cylinder in fluid of finite depth beneath an ice cover in the neighborhood of a vertical wall is obtained. The ice cover is simulated by a thin elastic semi-infinite plate of constant thickness. Different boundary conditions at the plate edge are considered, namely, the free and clamped edges. The added mass and damping coefficients, the deflection and strain amplitudes of the ice cover, and the forces exerted on the wall are investigated depending on the oscillation frequency and input parameters of the problem.

A Fast Immersed Boundary Fourier Pseudo-spectral Method for Simulation of the Incompressible Flows

Abstract The present paper is devoted to implementation of the immersed boundary technique into the Fourier pseudo-spectral solution of the vorticity-velocity formulation of the two-dimensional incompressible Navier-Stokes equations. The immersed boundary conditions are implemented via direct modification of the convection and diffusion terms, and therefore, in contrast to some other similar methods, there is not an explicit external forcing function in the present formulation. At the beginning of each time step, the solenoidal velocities (also satisfying the desired immersed boundary conditions), are obtained and fed into a conventional pseudo-spectral solver, together with a modified vorticity. The classical explicit fourth-order Runge-Kutta method is used in time integration, and the boundary conditions are set at the beginning of each sub-step, in order to increase the time accuracy. The method is employed in simulation of some different test cases, including the flow behind impulsively started circular cylinder, oscillating circular cylinder in fluid at rest and insect-like flapping wing motion. The results show accuracy and efficiency of the method.

An adaptive version of ghost-cell immersed boundary method for incompressible flows with complex stationary and moving boundaries

An adaptive version of immersed boundary method for simulating flows with complex stationary and moving boundaries is presented. The method employs a ghost-cell methodology which allows for a sharp representation of the immersed boundary. To simplify the implementation of the methodology, a volume-of-fluid method is introduced to identify the immersed boundary. In addition, the domain is spatially discretized using a tree-based discretization which is relatively simple to implement a fully flexible adaptive refinement strategy. Finally, the methodology is validated by comparing it with numerical and experimental results on three cases: (1) the flow passing a circular cylinder at Re=40 and Re=100, (2) a periodic oscillation of a circular cylinder in fluid at rest and (3) the self-propelled fish-like swimming at Re=6400.

Scattering of surface waves by a half immersed circular cylinder in fluid of finite depth

A train of surface waves is normally incident on a half immersed circular cylinder in a fluid of finite depth. Assuming the linearized theory of fluid under gravity an integral equation for the scattered velocity potential on the half immersed surface of the cylinder is obtained. It has not been found possible to solve this in closed form even for infinite depth of fluid. Our purpose is to obtain the asymptotic effect of finite depth “h” on the transmission and reflection coefficients when the depth is large. It is shown that the corrections to be added to the infinite depth results of these coefficients can be expressed as algebraic series in powers of a/h starting with (a/h) 2 where “a” is the radius of the circular cylinder. It is also shown that the coefficients of (a/h) 2 in these corrections do not vanish identically.

Experiments on Strouhal's Number

The frequency n of eddies generated behind a circular cylinder in fluid is expressed by the equation n=S(v/d), where v is the fluid velocity, d the diameter of circular cylinder and S Strouhal's number, which has been treated as the function of Reynold's number. Many inverstigators have experimented on the values of Strouhal's number between R6≒3×10∼5×105, but the values between. R6≒2×104∼1×105 have not been obtained. The present authors have experimented on all of them between R6≒6×10∼5×105 by three devices with a high speed tunnel, a low speed tunnel and a water rotating vessel respectively and have made it clear that they take nearly a value of 0.18 between R6=1×104∼1×105, suddenly increasing to 0.3∼0.6 at the point near the critical Reynold's number Rec≒5×105.

Experiments on Strouhal's Number

The frequency n of eddies generated behind a circular cylinder in fluid is expressed by the equation n=S (v/d), where v is the fluid velocity, d the diameter of circular cylinder and S Strouhal's number, which has been dealt with the function of Reynold's number. Many investigators have experimented on the values of Strouhal's number between Re≒3×10∼5×105, but the values between Re≒2×104∼1×105 have not been obtained. The present authors have experimented on all of them between Re≒6×10∼5×105 by three devices with high speed tunnel, low speed tunnel and water rotating vessel respectively and have made it clear that they take nearly a value of 0.18 between Re=1×104∼1×105 and suddenly increase 0.3∼0.6 at the point near the critical Reynold's number Rec≒5×105.

On the Eccentric Rotation of a Circular Cylinder in Fluid

The critical speed of a shaft rotating in water differs from that in vacuum. This is due to the hydrodynamical force generated by the eccentric rotation of the shaft. So, to analyse this problem, these fluid motions must be investigated. In this report, these fluid motions are approximately calculated and the hydrodynamical force is derived. Furthermore, the experiments are made and compared with the calculations. They coincide with each other very well. Also, the attached moments of inertia are calculated.

On the Eccentric Rotation of a Circular Cylinder in Fluid (2nd Report)

On the Eccentric Rotation of a Circular Cylinder in Fluid (2nd Report)

On the Eccentric Rotation of a Circular Cylinder in Fluid (1st Report)

In the previous and another reports, we obtained the stream functions for the eccentric rotational motion of a cylinder in fluid. In this report, from these results we calculate the pressure distributions on the surface of the cylinder and the resultant force. The pressure distributions for the motion in the infinitely wide region (Case A) are expressed by Eq. (4) and for the motion in the cylindrical vessel (Case B), by Eq. (12), and some numerical examples are shown in Fig. 1 for Case A and in Fig. 5 and 6 for Case B. The resultant force PL' acting towards the direction that increases the eccentricity, is expressed by Eq. (8) for Case A and by Eq. (22) and (25) (when ri/r0 is nearly equal to 1) for Case B. Figs. 7 and 8 show the above results respectively for ω/Ω=1 (forward precession) and for ω/Ω=-1 (backward precession). Also we calculate the attached moment of inertia which is shown in Eqs. (30) and (31), and in Fig. 12.