Mixed convection from a straight isothermal tube of elliptic cross-section

The behavior and characteristics of the wake produced behind an elliptic cylinder at 0° angle of attack, in the presence of trip wires, are investigated experimentally and numerically For this purpose, an aluminum cylinder model with an elliptic cross section and a length of 390 mm, major diameter of 424 mm and minor diameter of 212 mm was tested in the test section of a wind tunnel Realizable k–e turbulence model was used for the numerical analysis and SIMPLEC algorithm was employed for pressure–velocity coupling Reynolds numbers corresponding to the major diameter of the cylinder were 38,550 and 64,250 for air velocities of 15 m/s and 25 m/s, respectively Turbulence trip wires of 5 mm diameter were installed symmetrically on the elliptic cylinder at angles of 237° and 409° relative to the stagnation point The drag coefficient for the smooth elliptic cylinder was about 6 at both Reynolds numbers Results showed a drag coefficient reduction of 75% in the best possible case It was also concluded that a turbulence promoter wire has a significant effect on flow characteristics and reduction in the drag coefficient, and that it strongly depends on the location where the trip wire is installed on the model

Numerical and Experimental Study of Characteristics of the Wake Produced Behind an Elliptic Cylinder with Trip Wires

An experimental investigation has been conducted to clarify heat transfer characteristics and flow behaviors around an elliptic cylinder. Also, flow visualization was carried out to clarify the flow patterns around the cylinder. The elliptic cylinder examined has an axis ratio of 1:2.17, was placed in the focus of a parabolic plate. The test fluid is air and the Reynolds number based on the major axis length, ranged from 5·10 3 to 3·10 4 . The angle of attack was changed from 0° to 90° at 15° interval. It is found that the pressure distribution, form drag, location of separation point, and heat transfer coefficient depend strongly upon the angle of attack. Over the Reynolds number range examined, the mean heat transfer coefficient is at its highest ata = 60°-90°. The values of heat transfer coefficient in the case of free cylinder are higher than those for cylinder/plate combination at all angles of attack and Reynolds number range examined.

/pdf/flow-and-heat-transfer-characteristics-around-an-elliptic-43ltiaxi5h.pdf

Flow and heat transfer characteristics around an elliptic cylinder placed in front of a curved plate

In this study, an experimental investigation has been conducted on the characteristics of the wake behind the elliptical cylinder with the axis ratio of $$AR = 2$$
 . In order to provide a comparison, the same experimental investigation has also been conducted for a circular cylinder with the vertical height equal to the height of the elliptical cylinder. For studying the wake behind these two cylinders, hot-wire anemometry measurement has been performed. All of the tests are carried out in Reynolds number of $$3.0\times 10^4$$
 (which is defined according to the mean velocity of air and the cylinder diameter). Results are presented in terms of time-averaged velocity, standard deviation, higher-order central moments of the hot-wire signals (skewness and kurtosis factors), Strouhal number and drag coefficient. For the regions near the wake, the velocity deficit of the elliptical cylinder is greater compared to the circular cylinder; however, this is completely reversed in the regions far from the wake. As the axis ratio of the cylinder decreases, the dimensionless standard deviation becomes higher, and it’s maximum value is located at an earlier stream-wise location. In addition, it is observed that by increasing the axis ratio of the cylinder, drag coefficient decreases, while the Strouhal number is increasing.

/pdf/comparing-the-wake-behind-circular-and-elliptical-cylinders-13494mqhdw.pdf

L. Ieong

Papers

On Some Aspects of Unsteady Aerodynamics and Vortex Induced Oscillations of Elliptic Cylinders at Subcritical Reynolds Number