Experiments are described in which the vortex shedding from a bluff body and the base pressure coefficient have been measured in a shear flow. It is shown that the shedding breaks down into a number of spanwise cells in each of which the frequency is constant. The division between the cells is thought to be marked by a longitudinal vortex in the stream direction and this is supported by evidence from experiments where a longitudinal vortex was generated in an otherwise uniform flow.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112073000236

Vortex shedding from bluff bodies in a shear flow

Forces on cylinders and spheres in a sinusoidally oscillating fluid

'The unsteady aerodynamic characteristics of a circular cylinder in incompressible crossflow have been studied to obtain a better understanding of the coupling between body motion and Karman vortex shedding. It is found that the coupling is taking place through the effect of body motion on the boundary-layer development between stagnation and flow separation points. Using a moving wall/wall jet analogy, the experimentally observed effects of lateral and longitudinal oscillations on the Karman vortex shedding at subcritical Reynolds numbers can be explained. This permits an assessment to be made of the potential for self-excited oscillations in the different flow regimes. Where experimental results are available, they agree with this assessment. Basic flow similarity indicates that the unsteady flow concepts developed for prediction of dynamic stall of airfoils could be modified and applied to predict the observed effects of body motion on the Karman vortex shedding as well as the measured cylinder response. a c d

Karman Vortex Shedding and the Effect of Body Motion

A numerical analysis of forced-convection heat transfer from a horizontal stationary circular cylinder dissipating a uniform heat flux in a crossflow of air is conducted by solving the full two-dimensional steady-state Navier-Stokes and energy equations in the range of the Reynolds numbers from 100 to 500 (based on diameter). A numerical study by this author for Reynolds numbers less than 100 was previously conducted and therefore is not repeated here. Dependence on the Reynolds number of the flow and thermal fields, vorticity and pressure distributions, separation angle, drag coefficient, and local and average Nusselt number around the cylinder are shown. Correlations for the separation angle and drag coefficient as functions of Reynolds number are suggested. Quantities such as vorticity, pressure, and Nusselt number at the forward and rear (base) stagnation points are also calculated and correlated as functions of Reynolds number. The local and average values of the Nusselt numbers are shown to be in go...

Steady-State Numerical Solution of the Navier-Stokes and Energy Equations around a Horizontal Cylinder at Moderate Reynolds Numbers from 100 to 500

European Mechanics Colloquium number 17 was held at Cambridge from 1 to 3 July 1970, when the subject of bluff bodies and vortex shedding was discussed. The following report summarizes some of the papers presented. No formal proceedings of the meeting will be published.

Bluff bodies and vortex shedding – a report on Euromech 17

Vortex shedding from circular cylinders in sheared flow.

Vortex shedding from circular cylinders in an oscillating freestream

The firstand second-order problems for a uniform shear flow past an airfoil have been formulated and solved. It has been assumed that the stream shear, when properly nondimensionalized, must be of order 1. Expressions for the firstand second-order pressure coefficients have been obtained. The lift and moment coefficients are given in integral form. Once the airfoil shape is known, the force coefficients can be obtained by integration. Numerical calculations have been carried out to obtain lift coefficients on a symmetric Joukowsky airfoil, a circular arc, and a cambered Joukowsky airfoil for different values of stream vorticity. It is found that, in general, if the nondimensional stream vorticity (with respect to the airfoil chord and a reference velocity) is limited to 1 or less, the second-order theory will give lift coefficients within 5% of the exact theory up to 30° angle of attack. The uniformly valid pressure distributions correct to the second order along a symmetric Joukowsky airfoil at 10° incidence are presented to exhibit the effect of stream shear.

Second-order theory for airfoils in uniform shear flow.

Effect of nonequilibrium dissociation on constant pressure laminar mixing.

V Karman and Tsien formulated the lifting line theory for a wing in nonuniform flow in 1945. In their formulation, the approaching flow may have arbitrary variations in the plane perpendicular to the flight direction. By working with the perturbation pressure rather than the perturbation velocities, they have obtained the condition for the minimum induced drag and the method of calculation for the induced drag of a lifting line with arbitrary spanwise lift distribution. No specific examples, however, were given. In this note, we present the calculation of the induced drag of an elliptically loaded lifting line in an exponentially sheared flow in the vertical direction. The result applies equally well to a linearly sheared flow provided the shear rate is small. Consider a lifting line with a unit semispan in an incompressible, inviscid stream which is sheared in the vertical direction. Let the rectangular coordinate system be such that the y axis is in the direction of the span with the lifting line extending from y = — 1 to y = +1, the x axis in the direction of the approaching flow U(z), and the z axis pointing upwards. By considering the flow in the Trefftz plane (x -> oo ), von Karman and Tsien give the following governing equation: ] = 0 (1)

C. F. Chen

Papers

Vortex shedding from circular cylinders in sheared flow.

Vortex shedding from circular cylinders in an oscillating freestream

Second-order theory for airfoils in uniform shear flow.

Effect of nonequilibrium dissociation on constant pressure laminar mixing.

Effect of flow shear on induced drag.