• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2625-2630
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• 2008

Horseshoe vortices are formed at the junction of an object immersed in fluid-flow and endwall plate as a result of three-dimensional boundary layer separation. This study shows preliminary results of the kinematics of such horseshoe vortices around a circular cylinder with a cavity (slot) placed upstream to disturb the primary separation line. Through the cavity, no mass flow addition (blowing) or reduction (suction) is applied. The upstream cavity weakens the adverse pressure gradient before the cavity. With the upstream cavity, a single vortex is found to form immediately upstream of the cylinder whereas a typical two vortex system is observed in the absence of the cavity. Furthermore, the strength of the single vortex tends to be reduced, resulting from the interaction with the separated flow convecting directly towards the leading edge of the cylinder.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.1
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• pp.43-48
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• 1997

The present study is aimed to investigate experimentally on the hydrodynamic behaviours of air ~ pulverized coal flow in rectangular combustor with cavity. Mean velocity, density and tur¬bulent properties of pulverized coal in rectangular entrained flow combustor were measured by PDA. Experimental results show that the flow reattachment point at the lower plane in the com¬buster chamber has been developed near X/D= 15. The similarities at each section are found after the flow reattachment point. The maximum values of turbulent intensity and Reynolds shear stress have been shown near Y/D=6, which is higher than centerline. The maximum density of the pulverized coal sited in the range ofY/D=6~8.

• Journal of computational fluids engineering
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• v.4 no.1
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• pp.8-18
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• 1999

In devising a numerical approximation for the convective spatial transport of a fluid mechanical quantity, it is noted that the convective motion of a scalar quantity occurs in one-way, or from upstream to downstream. This consideration leads to a new scheme termed a pure upwind difference scheme (PUDS) in which an estimated value for a fluid mechanical quantity at a control surface is not influenced from downstream values. The formal accuracy of the proposed scheme is third order accurate. Two typical benchmark problems of a wall-driven fluid flow in a square cavity and a buoyancy-driven natural convection in a tall cavity are computed to evaluate performance of the proposed method. for comparison, the widely used simple upwind scheme, power-law scheme, and QUICK methods are also considered. Computation results are encouraging: the proposed PUDS sensitized to the convection direction produces the least numerical diffusion among tested convection schemes, and, notable improvements in representing recirculation of fluid stream and spatial change of a scalar. Although the formal accuracy of PUDS and QUICK are the same, the accuracy difference of approximately a single order is observed from the revealed results.