• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.264-270
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• 2011

The Characteristics of the flowfield around three circular cylinders in tandem arrangement was investigated by PIV. Strouhal numbers, vorticity, velocity vectors and velocity profiles were observed at centre-to-centre space ratios of P/D=1.25~3.75, and Reynolds number of Re=$3.0{\times}10^3{\sim}5.0{\times}10^3$. As the results the Strouhal numbers measured in the rear region of 3rd the cylinder were distinguished three kind of regions with the space ratios and The flow pattern in the wake of each cylinder was different according to these regions. The time averaged flow at region of each cylinder was almost stagnated and the size of the stagnated region was small in order of 1st, 2nd and 3rd cylinder. The direction of vortex at the front and rear region of 2nd cylinder was opposed each other with the small difference(${\alpha}= {\pm}5^{\circ}$) of the attack angle ${\alpha}$.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.156-162
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• 2013

The characteristics of the unsteady flowfield of a square prism having a detached splitter plate at the wake side were investigated by advanced vortex method. The instantaneous and average velocity field and pressure field around a square prism without and having splitter plate were calculated by forcing the gap ratio having the maximum drag reduction rate, at Reynolds number $Re=1.0{\times}10^4$ and the width ratio H/B=1.0 of splitter to the prism width. The drag and lift coefficients on the square prism were also obtained. The calculated results agree with the measured drag coefficients and pressure distributions on the square prism. The vortices of the opposite direction at upside and down side of the splitter plate were generated by installing of the plate. And the drag on the square prism was decreased by increasing of the pressure of back face of the prism with the vortices.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.4
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• pp.20-25
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• 2016

A primary benefit of flight at high angle-of-attack conditions is to be able to reduce the speed of flight and maneuvers, which can enhance the capability of sensing and obstacle avoidance for a small UAV. The flight at high angle-of-attack conditions, however, is easy to be beyond stall which is characterized by substantial flow separation over an airfoil. Current numerical analysis was conducted on the capabilities of three representative turbulence models to predict the aerodynamic characteristics of a typical airfoil at angle-of-attack conditions. The investigation shows that these turbulence models provide good comparison with experimental data for attached flow at moderate angle-of-attack conditions. Calculation by current turbulence models are, however, not appropriate at high angle-of-attack conditions with flow separation.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.2
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• pp.12-17
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• 2020

Even though the benefit of flight at high angle-of-attack is to be able to reduce the speed of flight and maneuvers in complex flight environment, the flight at high angle-of-attack, however, is easy to be in stall which is characterized by sever unsteady flow separation over an airfoil. Current unsteady numerical analysis using DES was conducted to predict the aerodynamic characteristics of a NACA 0021 airfoil at high angle-of-attack conditions. And this provides the comparison with the steady numerical one with the typical turbulence models. The unsteady calculation by DES is appropriate in terms of predicting the aerodynamic performance of NACA 0021 airfoil at high angle-of-attack conditions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.191-194
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• 2003

A series of computational simulations have been carried out for non-reacting and reacting flows in a supersonic combustor configuration with and without a cavity. Transverse injection of hydrogen, a simplest form of fuel supply, is considered in the present study with the injection pressure of 0.5 and 1.0 ㎫. The corresponding equivalence ratios are 0.17 and 0.33. The work features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous studies. In particular, oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The role of the cavity, injection pressure, and amount of heat addition are examined systematically.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.527-530
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• 2006

In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

• Journal of computational fluids engineering
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• v.5 no.2
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• pp.9-19
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• 2000

Transient aerodynamic response of an airfoil to a moving plane-flap is numerically investigated using the two-dimensional Euler equations with conservative Chimera grid method. A body moving relative to a stationary grid is treated by an overset grid bounded by a 'Dynamic Domain Dividing Line' which has an advantage for constructing a well-defined hole-cutting boundary. A conservative Chimera grid method with the dynamic domain-dividing line technique is applied and validated by solving the flowfield around a circular cylinder moving supersonic speed. The unsteady and transient characteristics of the flow solver are also examined by computations of an oscillating airfoil and a ramp pitching airfoil respectively. The transient aerodynamic behavior of an airfoil with a moving plane-flap is analyzed for various flow conditions such as deflecting rate of flap and free stream Mach number.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.85-94
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• 1999

Transient aerodynamic response of an airfoil to a moving plane-flap is numerically investigated using two-dimensional Euler equations with conservative Chimera grid method. A body moving relative to a stationary grid is treated by an overset grid bounded by a 'dynamic domain-dividing line' the concept of which is developed in this study. A conservative Chimera grid method with a dynamic domain-dividing line technique is applied and validated by solving the flowfield around circular cylinder moving supersonic speed. The unsteady and transient characteristics of the flow solver is also examined by computations of a oscillating airfoil and a ramp pitching airfoil respectively. The transient aerodynamic behavior of an airfoil with a moving plane-flap is analyzed for various flow conditions such as deflecting rate of flap and free stream Mach number.

• The KSFM Journal of Fluid Machinery
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• v.9 no.4 s.37
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• pp.36-42
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• 2006

In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.126-131
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• 2003

A series of computational simulations have been carried out for supersonic flows in a scram jet engine with and without a cavity. Transverse injection of hydrogen, a simplest form of fuel supply, is considered in the present study with the injection pressure varying from 0.5 to 1.5 MPa. The corresponding equivalence ratios are 0.167 - 0.50. The work features detailed resolution of the flow dynamics in the combustor, which was not typically available in most of the Previous studies. In particular, oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between shock waves and shear layer may cause a large excursion of flow oscillation. The role of the cavity and injection pressure are examined systematically.