Cylinder In Turbulent Flow Research Articles

Corrosion of Copper Metal in Presence of Binary Mixtures

The rates of copper corrosion were determined in presence and in absence of different compositions of water-ethanol, -ethylene glycol, -glycerol, -dimethyl sulfoxide (DMSO) and -dioxane binary mixtures. The rates of corrosion were found to decrease by increasing the concentration of solvents. The percent inhibition range from 10.9 to 78.2% depends on the nature of solvent and its concentration. The calculated energies of activation prove that the reactions are diffusion controlled. Thermodynamic parameters were calculated. The investigated adsorption isotherms indicate that, protic solvents fit the Langmuir model. The rate of corrosion of copper in presence of diphragm is less than that in absence of diphragm due to the prevention of stirring of hydrogen evolved at cathode. The overall mass transfer correlations under the present conditions have been obtained using dimensional analysis method. The results agreed with the previous studies of mass transfer to rotating cylinder in turbulent flow.

Numerical prediction of a plume diffusion field around a circular cylinder by the particle method

In order to elucidate the applicability of particle methods to the prediction of diffusion of matter in free turbulent flow, a point-source plume diffusion field upstream of, around and behind a circular cylinder in turbulent flow is simulated. The velocity field is calculated by a vortex method, while the concentration field is computed by a particle method analogous to the vortex method. The calculated mean concentration field from a point source can be favorably discretized by the concentration elements with a finite core. The diffusing matter is entrained into the Kármán vortices and exhibits meandering behavior in accordance with the experiment. The mean concentration is in good agreement with the experiment upstream of, around and behind the cylinder, suggesting that the present particle method has high applicability to the analysis of the mean concentration field.

The effect of turbulence on aerodynamic forces on a square cylinder with various corner shapes

To comprehensively investigate the effect of corner modification on aerodynamic forces, we set up an experimental model of a two- and three-dimensional square cylinder in several types of oncoming flow, a smooth and homogeneous turbulent flow. We carried out wind tunnel tests for measurements of aerodynamic quantities, such as averaged and fluctuating statistics of lift and drag forces, acting on a square sectioned cylinder with sharp, chamfered or rounded corners. The principal results are as follows: (1) Chamfered and rounded corners decrease drag forces, as a result of reduction in wake width. (2) For a round-cornered cylinder in turbulent flow, it is found that the shear layer that separate from the windward edge reattaches to the side surface even at angle of attack a=0°. (3) The values of CLRMS for three-dimensional cylinders are reduced to about 10% (in uniform flow) of the values for two-dimensional cylinders. This means that the effect of Karman vortices and the resulting lift force are not so large for three-dimensional cylinders.

Discussion of bluff bodies - 4: The coherence of cross-wind velocity and pressure on two-dimensional rectangular cylinders in turbulent flows. E. Jancauskas & R. Sankaran

Discussion of bluff bodies - 4: The coherence of cross-wind velocity and pressure on two-dimensional rectangular cylinders in turbulent flows. E. Jancauskas & R. Sankaran

The coherence of cross-wind velocity and pressure on two-dimensional rectangular cylinders in turbulent flows

Measurements of spanwise coherence of velocity and pressure, obtained for a range of two-dimensional rectangular cylinders in grid generated turbulence, support the contention that the von Kámán parameter is a more appropriate and theoretically justifiable choice for collapsing the coherence data than the simple separation-to-wavelength ratio. More importantly, the present measurements have also been used to investigate the relationship between the spanwise coherence of pressure fluctuations and vertical velocity fluctuations. It appears that, in general, the coherence of velocity is less than that of pressure measured at the leading edge of the model.

On the Diffusion of Fluid Particles by the Combined Model of Random Fourier Modes and Random Flight.

To investigate the motion of fluid particles round a cylinder in turbulent flows, we have developed a new model simulating the trajectory of particles: the combined model of Kinematic Simulation (KS) and Random Flight (RF). The large-scale turbulence is simulated by a sum of random Fourier modes varying in space and time, and the small-scale turbulent fluctuation is simply modelled by ITO type of stochastic differential equation with a memory time comparable to a Lagrangian integral time scale TLS of small-scale motion. The Lagrangian properties of fluid particles in homogeneous isotropic turbulence with uniform mean flow has been examined. Some new results have been obtained using this new model: (a) the cross-correlation of the displacements by the large and small scale motions is negligibly small; (b) the random small-scale motion causes the decorrelation of the large-scale velocity; (c) the value of TLS used in RF is estimated from pure KS.

Characteristics of Circular Cylinders in Turbulent Flows

The effect of a free-stream turbulence of high intensity on the flow past a rigid circular cylinder was experimentally studied in a Reynolds-number range 7.9×103∼5.4×l04. Square-meshed grids were used to produce homogeneous turbulent-flow fields. The intensity and scale of a turbulent flow in which the cylinder was immersed were varied by positioning the cylinder at various locations downstream of the grid. Measurements were made of the time-averaged drag coefficient, Strouhal number of the vortex shedding, spanwise correlation length and length of the vortex formation region in the wake of the cylinder. These properties of flow around the cylinder were found to be considerably different from those measured in a smooth flow.

The interference between bluff sharp-edged cylinders in turbulent flows representing models of two tower buildings close together

The interference between bluff sharp-edged cylinders in turbulent flows representing models of two tower buildings close together

Tests on Cylinders in Turbulent Flow

The note describes the experimental investigation under way to study the effect of turbulence on the drag coefficient of cylinders at Lehigh University.

乱流中に於ける円柱の振動性状について

In this paper, the results of measurements on oscillatory tendencies of circular cylinder in turbulent flow having the linear distribution of mean wind velocity along the height are presented. The experiment was conducted at the roof of the building of Dept. of Architecture & Bldg. Eng., Tokyo Inst. of Tech. A circular cylinder model, made of plastics and fixed vertically on a steel frame on the roof with a steel bar, is 0.37m in diameter and 1.8m in height. Its natural frequency n_0 is 2.44, 3.03c/sec for two cases, damping ratio is about 0.0025 and Reynolds Number is between 5.0×10^4 and 2.5×10^5 for 30 seconds mean wind velocity U_0. The response of the model was measured using wire strain gauges bonded on the bar. Features of the observed wind by wind meter are as follows; U_0 is 2〜10m/sec, turbulence level is 20〜50% for longitudinal wind velocity and 10〜30 degrees for wind direction and this observed wind can be identified with natural wind. From the experiment, following conclusions were obtained. (1) Adoption of seconds; 100 times of the period of the model, for response evaluating time could be satisfying. (2) A prominent oscillation by Karman vortex was observed. (3) The beat phenomenon based on a characteristics of the model had large effects. (4) Though a prominent peak was seen at S(=n_0D/U_0)=0.2, effects based on "beat phenomenon" and the turbulence of wind were found in calculated mean drag and fluctuating lift coefficient for a oscllating circular cylinder.

The Axial Frictional Resistance of Long Cylinders in Turbulent Flow

In ship-model extrapolation the frictional resistance of the ship surface is generally taken to be equal to that of the flat plate having the same length and area. Experiments carried out at several laboratories with models of different size show dearly that each model should have its own extrapolation curve. In spite of general agreement that this is so, the flat-plate extrapolation curve is still generally used. On the other hand it is not easy to derive mathematical relations for ship-form frictional resistance or to make extensive experiments for this purpose. It is obvious that a first step towards departing from the flat-plate resistance basis should be to study the effect of transverse curvature on frictional resistance.

Cavitation Tests of the Cylinder in Turbulent Flow

Cavitation tests of the cylinder were performed in a small type cavitation tank, measuring the pressure distribution around the cylinder. The turbulence of the flow in the test channel was given by two kinds of grid with the square mesh. The cavitation tests showed that the characteristics of the cylinder i. e. the drag was affected by the turbulence of flow.