Flow and heat transfer around a diamond-shaped cylinder at moderate Reynolds number

Abstract

Hydrodynamics and heat transfer around a diamond-shaped cylinder in a stationary flow have been investigated using direct numerical simulation. Simulations were carried out for a steady flow with a Reynolds numbers ranging from 1 to 70 and for a Prandtl number corresponding to a gas (P r = 0.7). The study focuses on the influence of the diamond apex angle α (33 ≤ α ≤ 120 • ) on the evolution of drag, wake length and Nusselt number. A comparison with the case of a circular cylinder is performed. It is shown that the drag coefficient of a diamond-shaped cylinder remains very close to the one of a circular cylinder (±10%) for Re < 10 and that it is reduced by decreasing the apex angle for Re > 10. In the same time, compared to the circular cylinder case, the reduction of the apex angle postpones significantly the Reynolds corresponding to the wake recirculation onset. When the Reynolds reference velocity is, as often, taken as the far field velocity, the corresponding Nusselt numbers are found to decrease with the apex angle α. However, it is found that when the reference velocity is based on the maximal vorticity near the equator, the Nusselt number of diamond-shaped cylinders seems to collapse on a single master curve. This may indicate that the relevant velocity scale to describe Nusselt variation, and thus the heat transfer, is dependant on the interfacial vorticity intensity rather than on the far field velocity.

Pressure Losses at Moderate Reynolds Numbers in Diamond-Shaped Cylinders Arrays: Application to Microregenerators

“…This behaviour is first explained by the fact that when the porosity gets close to unity the flow around the cylinders gets close to the flow around a single cylinder whatever the arrangement is. Secondly, as reported recently by Sochinskii et al [52] the drag for a circular cylinder is very close to the one obtained from a diamond-shaped cylinder with an apex angle of α " 90˝. As a result, the arrangement of circular or 90˝diamond-shaped cylinders gives similar drag law and Poiseuille number when the porosity tends to unity.…”

“…Globally, for a given angle α, it is observed that the drag increases systematically when the porosity decreases and the spacing between cylinders is reduced. In addition, the correlation found by Sochinskii et al [52] for a single diamond-shaped cylinder is also reported in this figure . As for an array of particles [53,42], it is found that the drag for one cylinder in a matrix is always larger than the one expected for a single cylinder. This…”

“…As a result, the arrangement of circular or 90˝diamond-shaped cylinders gives similar drag law and Poiseuille number when the porosity tends to unity. This is confirmed by the fact that the dimensionless drag force predicted by the relation proposed by Yeom et al [6] for ǫ " 0.99 with a square array of circular cylinders ( cylinder with α " 90˝at low Reynolds number (F {µU " rpC D {2qpD h qρU 2 s{pµU Hq " 6.98{2 " 3.49, [52]).…”

Modeling of Heat Transfer Around a Square and a Circle: A Novel ANN-Based Approch

“…Levenberg -Marguardt -20 neuron was the best algorithm for o2 and o3 type cycles while Levenberg -Marguardt -22 neuron algorithm was the best algorithm for b3 type cycles. Sochinskii et al [11] examined numerically the heat transfer and hydrodynamics around the diamond type cylinder. Reynolds number was between 1 and 70 whereas Pr number was taken as 0.7.…”

“…Circle cylinder configurationEquations were solved using a staggered grid. The Equation(11) was used in order to observe the independent behaviour of the temperature on flow area. n is the time step.…”