• Journal of computational fluids engineering
• /
• v.17 no.3
• /
• pp.87-92
• /
• 2012

The presence of a layer of vegetation which is relevant in river engineering or coastal engineering can modify the overall flow resistance, turbulent characteristics of flow. The patch of vegetation can be modelled and studied in a simple porous cylinder by previous researchers. Fully three dimensional Large Eddy Simulation is conducted in flow past a porous cylinder with a solid volume fraction (SVF) 0f 20%. The porous cylinder of diameter D contains 89 smaller cylinders which diameter is 0.048D in a regular staggered way. Reynolds number based on porous cylinder diameter D and the bulk velocity is 10,000. The large scale shedding is qualitatively similar to the one observed in the non-porous case (SVF=100%). The difference in the dynamics of the separated shear layer and the streamwise flow penetrating through the porous cylinder are compared with those in the non-porous cylinder. In particular, the wake billows form a larger distance from the back of the porous cylinder.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.5
• /
• pp.349-357
• /
• 2009

Effect of computational domain size in simulating of periodic obstacle flow has been investigated for the flow past tube banks. Reynolds number, defined by freestream velocity ($U_{\infty}$) and cylinder diameter (d), was fixed as 200, and center-to-center distance (P) as 1.5d. In-line square array and staggered square array were considered. Drag coefficient, lift coefficient and Strouhal number were calculated depending on domain size. Circular cylinders were implemented on a Cartesian grid system by using an immersed boundary method. Boundary condition is periodic in both streamwise and lateral directions. Previous studies in literature often use a square domain with a side length of P, which contains only one cylinder. However, this study reveals that the domain size is improper. Especially, RMS values of flow-induced forces are most sensitive to the domain size.

• Wind and Structures
• /
• v.29 no.1
• /
• pp.65-75
• /
• 2019

A heated square cylinder (with height $A^*$) is kept parallel to the cold wall at a fixed gap height $0.5A^*$ from the wall. Another adiabatic rectangular cylinder (of same height $A^*$ and width $0.5A^*$) is placed upstream in an inline tandem arrangement. The spacing between the two cylinders is fixed at $3.0A^*$. The inlet flow is taken as Couette-Poiseuille flow based non-linear velocity profile. The conventional fluid (also known as base fluid) is chosen as water (W) whereas the nanoparticle material is selected as $Al_2O_3$. Numerical simulations are performed by using SIMPLE algorithm based Finite Volume approach with staggered grid arrangement. The dependencies of hydrodynamic and heat transfer characteristics of the cylinder on non-dimensional parameters governing the nanofluids and the fluid flow are explored here. A critical discussion is made on the mechanism of improvement/reduction (due to the presence of the upstream cylinder) of heat transfer and drag coefficient, in comparison to those of an isolated cylinder. It is observed that the heat transfer increases with the increase in the non-linearity in the incident velocity profile at the inlet. For the present range studied, particle concentration has a negligible effect on heat transfer.