In many industrial equipment such as boilers and heat exchangers, the cylindrical tubes are exposed to the gas- liquid two phase flow. For any immersed body in flow field vortex shedding is created with a frequency that may be constant or variable, according to conditions such as flow rates, geometry of body, and etc. The failure will happen in the equipment, when this frequency is close to...

A wing submerged in the wake of an upstream airfoil experiences periodic forces. The frequency and amplitude oscillations produce vortex streets varying wavelength circulation. lift coefficient depends on a single parameter, which is Strouhal number based airfoil.

Abstract It is known that plunging airfoil can produce both lift and thrust with certain combination of plunging amplitude and frequency. Motivated by our interest in micro air vehicles (MAVs), we utilize a NavierStokes equation solver to investigate the aerodynamics of a flapping airfoil. The roles of the plunging and pitching amplitude and frequency, and Strouhal number are studied. For a sym...

A brute-force testing technique was applied on a robotic controlled-curvature flapping fin propulsor to investigate output thrust and power consumption trends with respect to flapping frequency, amplitude, and gait. It has been discovered that maximum thrust and maximum propulsive efficiency can coexist, that flapping frequency and amplitude are sometimes interdependent parameters, and that act...

Abstract In this paper, unsteady laminar flow around a circular cylinder has been studied. Navier-stokes equations solved by Simple C algorithm exerted to specified structured and unstructured grids. Equations solved by staggered method and discretization of those done by upwind method. The mean drag coefficient, lift coefficient and strouhal number are compared from current work at three diffe...

In a previous paper, we provided a rationale for the empirically observed St–Re number relationship for vortex shedding in bluff-body wakes. This rationale derives from a mechanism of vortex formation observed in numerical simulations coupled with an estimate of the terms in the vorticity transport equation based on this mechanism. Adopting the typical size of the body D as the characteristic l...

In this research numerical simulations are performed, using the multi-relaxation-time lattice Boltzmann method, in the range 3 ≤ β = w[d] ≤ 30 at Re = 100, 200 and 300, where β the blockage ratio, w is the equispaced distance between centers of cylinders, d is the diameter of the cylinder and Re is the Reynolds number, respectively. Special attention is paid to the effect of the equispaced dist...

We examine the effect of prescribed wall-driven oscillations of a flexible tube of arbitrary cross-section, through which a flow is driven by prescribing either a steady flux at the downstream end or a steady pressure difference between the ends. A large-Womersley-number large-Strouhal-number regime is considered, in which the oscillations of the wall are small in amplitude, but sufficiently ra...