Triyogi Yuwono

Flow Characteristics around Four Circular Cylinders in Equispaced Arrangement near a Plane Wall

The flow characteristics around four circular cylinders in equispaced arrangement located near a plane wall were investigated experimentally. The pressure distributions on the each cylinder surface and on the plane wall were measured for a spacing ratio L/D= 1.5 (L, center to center spacing between cylinders; D, diameter) and G/D= 0.2 (G, gap spacing between cylinder surface and the plane wall) in a uniform flow at a Reynolds Number of 5.3 x 104. The 2D U-RANS numerical simulation with k-ω SST as viscous model was used to visualize the flow phenomena occured around the cylinders. The results showed that the flow tend to be biased on the upper side of cylinders configuration. It causes the stagnation at the upstream cylinders occured at lower side of cylinders and results a formation of a narrower wake behind the third cylinder and a wider wake behind the fourth cylinder.Keywords: equispaced arrangement, circular cylinders, plane wall

The effect of width of single curtain on the performance of Savonius wind turbine

This is a preliminary results of the flow around the Savonius wind turbine with installing curtain plate in front of the returning blade turbine. It was investigated numerically in a uniform flow at Reynolds number of 30,000 and 90,000. The velocity vector and pressure distribution around the turbine were simulate by varying the width of curtain plate relative to the diameter of rotor blade (S/D) of = 1.00, 1.02, 1.03, 1.15, 1.41, and 2.00, using STAR CCM++ Software. The k- realizable as turbulence model was used to visualize the flow phenomena occurred around the turbine, and where in this simulation, the rotor turbine was set static. The results show that it seems the width of the curtain installed in front of the returning blade of the turbine plays an important role in the performance of the turbine. In general, the installing of the curtain in front of the returning blade of the turbine is more effective to improve the turbine performance. This is not necessarily, but depends on the width of the curtain and the number of Reynolds (Re). For the width of the large curtain of S/D = 2 at Re = 90,000, the performance of the turbine is estimated lower than when the turbine without

Numerical simulation of cross-flow around four circular cylinders in-line square configuration near a plane wall at supercritical Reynolds number

In this research, it would be investigated numerically the effects of spacing between centres of cylinders (L) on flow characteristics around four circular cylinders in in-line square configuration near a plane wall at supercritical Reynolds number. A spacing ratio between centres of cylinders (L/D) would be varied. It is set at L/D = 2.0, 2.7, and 4.0, while a gap ratio between the surface of lower cylinders and the wall (G/D) was fixed at 0.2. To analyse flow characteristics around cylinders is used FLUENT 6.3.26 software. Two-dimensional Unsteady Reynolds Averaged Navier Stokes equations and SST k-ω turbulence equations are solved with finite volume method. This simulation was performed at Reynolds number 8.4 × 106 based on a single circular cylinder diameter and free stream velocity. The numerical results show that at supercritical Reynolds number separation point of the upstream cylinders and the downstream cylinders move far from front-ward of cylinder, while a minimum pressure of cylinder-1 decrease particularly at lower surface. At the downstream cylinders, increasing of spacing ratio cause of reattachment point at lower surface move to front-ward. While at the plane wall, increasing of spacing ratio cause of the negative pressure points starts to recover the static pressure move to back-ward of wall.In this research, it would be investigated numerically the effects of spacing between centres of cylinders (L) on flow characteristics around four circular cylinders in in-line square configuration near a plane wall at supercritical Reynolds number. A spacing ratio between centres of cylinders (L/D) would be varied. It is set at L/D = 2.0, 2.7, and 4.0, while a gap ratio between the surface of lower cylinders and the wall (G/D) was fixed at 0.2. To analyse flow characteristics around cylinders is used FLUENT 6.3.26 software. Two-dimensional Unsteady Reynolds Averaged Navier Stokes equations and SST k-ω turbulence equations are solved with finite volume method. This simulation was performed at Reynolds number 8.4 × 106 based on a single circular cylinder diameter and free stream velocity. The numerical results show that at supercritical Reynolds number separation point of the upstream cylinders and the downstream cylinders move far from front-ward of cylinder, while a minimum pressure of cylinder-1 decreas...

Numerical simulation of cross flow around four circular cylinders in an in-line square configuration with the critical spacing ratio “L/D” near a plane wall

Flow cross around four circular cylinders arrangement near a plane wall could be found in many engineering application such as subsea pipeline, shell and tube heat exchangers, and tube banks, etc. When flow crosses the bodies, it would form a particular flow pattern according to the bodies arrangement. The objective of this research is to study numerically the effect of gap (G) on flow characteristics around four cylinders placed near a plane wall. Gap ratio (G/D) is defined as ratio between a distance of the wall to a surface of the bottom of the lower cylinders (G) and the cylinder diameter (D). It is varied of 0.2, 0.3, 0.5, 0.7, 1.0 and 1.5 with critical spacing ratio L/D (where L is a distance of cent re of cylinders) is fixed at 2.7. A numerical simulation with two dimensional Unsteady Reynolds Averaged Navier-Stokes equations and k-ω SST turbulence model is solved with a finite volume method has been applied to investigate this problem. To analyze flow characteristics around the cylinders is used F...