Numerical Simulation of Flow around Diamond-Shaped Obstacles at Low to Moderate Reynolds Numbers

Abstract

In this paper, viscous fluid flow over an unconventional diamond-shaped obstacle in a confined channel is simulated in low to moderate Reynolds numbers. The diamond-shaped obstacle is altered geometrically in order to represent different blockage coefficients based on the channel height and different aspect ratios based on the length to height ratios of the obstacle. An in-house finite difference Navier-Stokes solver using staggered grid arrangement and Chorin's projection method is developed for the simulation of the laminar viscous flow. The numerical solver is validated against numerical results that are presented in the literature for the flow over rectangular cylinders and good agreement is observed. Grid resolution has been studied within a mesh convergence test and as a result, suitable grid dimension is achieved. A series of simulations have been carried out for each set of geometry and configuration in order to find the critical Reynolds number for each case in which the vortex shedding will occur. Therefore, simulations are divided into two groups of steady and unsteady flows. In the case of unsteady flow, nondimensional Strouhal Number (St) is investigated and results prove the dependency of St on the blockage coefficient and aspect ratio. It is shown that the Strouhal number will increase with the rise of blockage ratio and the local maximum of St will occur at lower Re for geometries with lower aspect ratios (bluff bodies) than geometries with higher aspect ratios, i.e. with more streamlined bodies.

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

“…In this article, the influence of the incident angle on the flow pattern, the drag and lift, the angle of separation and the Strouhal number (linked to vortex shading frequency in the cylinder wake) is analysed. The flow around a single diamond-shaped cylinder confined in a channel has been studied by Djeddi et al [30] using direct numerical simulation for low and moderate Reynolds numbers (Re < 200). In this work, the Strouhal number variation was characterized against the cylinder aspect ratio and a blockage coefficient.…”

Numerical Analysis of Unsteady Laminar Flow past a Pentagonal Obstacle

“…The pressure contour is available in figure 7 for Re = 500 to closely visualize the pressure stagnation point and pressure difference in upper and lower streams of laminar flow in the computational domain. From the review of literature, it can be seen that the findings of this article are justifying the fact that obstacle having smooth rounded shape or flat face gives smaller value of drag coefficient when putting them against the flow direction [1]; whereas the shapes possesses sharp corners are comparatively produces larger drag value, [2], [7]. The case of Re = 500 is the case where both studies are found to have similar flow characteristics to some extent, the unsymmetrical eddies and phenomena of vortex shedding can be observed in both the cases in figure.5(e) & 6(e).…”

“…Their study primarily based on the comparison of drag coefficient determined at moderate Re = 200, it is beheld that the value of drag coefficient of faceoriented hexagonal is comparatively smaller than the drag coefficient found in the case of corner-oriented hexagonal cylinder. Such studies encourages scholars to conduct more research works on unconventional shaped cylinders in order to determine the effects of fluid inertia over the flow characteristics, specifically drag force, [7]. As discussed earlier that unconventional shaped obstacles getting too much attention of researchers since they come up with novelty in order to explore different behaviors of flowing fluid in open channel.…”

Turbulent Flow Around Obstacles: Simulation and Study with Variable Roughness

“…For their part, Kanfoudi et al [24] employed the large eddy simulation (LES) to perform a numerical analysis of the turbulent flow structure induced by the cavitation shedding. In addition, Djeddi et al [25] conducted a simulation of a viscous fluid flow over an unconventional diamond-shaped obstacle inside a confined channel, for low to moderate Reynolds numbers. For this, the diamond-shaped obstacle was geometrically modified to represent different blockage coefficients, depending on the height of the channel and for different aspect ratios, based on the obstacle's length-to-height ratios.…”