• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.3-8
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• 2009

Most vehicles have a heating, ventilating and air conditioning (HVAC) device to control the thermal condition and to make comfortable environment in the passenger compartment. The improvement of ventilation flow inside the passenger compartment is crucial for providing comfortable environment. For this, better understanding on the variation of flow characteristics of ventilation air inside the passenger compartment with respect to various ventilation modes is strongly required. Most previous studies on the ventilation flow in a car cabin were carried out using computational fluid dynamics (CFD) analysis or scale-down water-model experiments. In this study, whole ventilation flow discharged from the air vent of a real passenger car was measured using a special PIV (particle image velocimetry) system for large-size FOV (field of view). Under real recirculation ventilation condition, the spatial distributions of stream-wise turbulence intensity and mean velocity were measured in the vortical panel-duct center plane under the panel ventilation mode. These experimental data would be useful for understanding the detailed flow structure of real ventilation flow and validating numerical predictions.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.900-907
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• 2000

The three-dimensional turbulent flow in curved pipes susceptible to flow-accelerated corrosion has been analyzed numerically to predict the pressure and shear stress distributions on the inner surface of the pipes. The analysis employs the body-fitted non-orthogonal curvilinear coordinate system and a standard $ {\kappa}-{\varepsilon}$ turbulence model with wall function method. The finite volume method is used to discretize the governing equations. The convection term is approximated by a high-resolution and bounded discretization scheme. The cell-centered, non-staggered grid arrangement is adopted and the resulting checkerboard pressure oscillation is prevented by the application of a modified version of momentum interpolation scheme. The SIMPLE algorithm is employed for the pressure and velocity coupling. The numerical calculations have been performed for two curved pipes with different bend angles and curvature radii, and discussions have been made on the distributions of the primary and secondary flow velocities, pressure and shear stress on the inner surface of the pipe to examine applicability of the present analysis method. As the result it is seen that the method is effective to predict the susceptible systems or their local areas where the fluid velocity or local turbulence is so high that the structural integrity can be threatened by wall thinning degradation due to flow-accelerated corrosion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.374-387
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• 1999

Two-dimensional turbulent fluid flow and solidification were investigated in a continuous casting process of a steel slab with electromagnetic field. The electromagnetic field was described by the Maxwell equations. The enthalpy-porosity relation was employed to suppress the velocity within a mushy region. A revised low-Reynolds number $k-{\varepsilon}$ turbulence model was used to consider the turbulent effects. It is shown that the temperature gradient in the casting direction in the case with EMBR becomes very weak compared to that of the case without EMBR. The results also show that the velocity profiles of the case with solidification are quite different from those of the case without solidification.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.1
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• pp.1-12
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• 1996

The fully developed tubulent momentum and heat transfer induced by the square- ribbed roughness elements on both the inner and outer wall surfaces in the concentric annuli are studied analytically based on a modified turbulence model. Heat transfer coefficients for two conditions, i.e, a) inner wall heated as constant heat flux and outer wall insulated b) inner wall insulated and outer wall heated as constant heat flux, are investigated. The analytical results of the fluid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity profiles and friction factors, and etc. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Nusselt number and Prandtl number.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.16 no.2
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• pp.1-6
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• 2020

This work experimentally explored the influence of nano-fouling on CHF, flow boiling heat transfer coefficient, contact angle, and surface roughness. In this study, the flow velocity conditions are established at 0.5, 1.0, and 1.5 m/s. Also, the nanoparticles of oxidized MWCNT were deposited on a heat transfer surface for 0, 120, 180, and 240 sec. As the results, it was found that CHF and superheated temperature were increased in case of nano fouling on the heat transfer surface in oxidized MWCNT fluid. Also, the contact angle and surface roughness decreased when flow velocity and nano coating increased.

• Journal of applied mathematics & informatics
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• v.10 no.1_2
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• pp.193-207
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• 2002

The present investigation deals with the pulsatile flow of incompressible viscous fluid through a circular rigid tube provided with constriction. The method applied here is the Decomposition Method, which has been developed by George Adomian [3]. The advantages of this method are the avoidance of simplifications and restrictions, which change the non-linear problem to mathematically tractable one, whose solution is not consistent with physical solution. Theoretically results, such as, wall shear stress and axial velocity component, have been obtained and the graphical solutions of these theoretical results have been shown in the figures.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.3
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• pp.245-256
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• 2014

This work is focused on the boundary layer and heat transfer characteristics of hydromagnetic flow over a stretching sheet with variable thickness. Steady, two dimensional, nonlinear, laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness and power law velocity in the presence of variable magnetic field and variable temperature is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-Swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and the effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.29-35
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• 2000

The present experimental study is focused on the application of multi-point simultaneous measurement by PIV(Particle Image Velocimetry) to guide vane region within diffuser pump. Various different kinds of rotational velocity were selected as experimental condition. Optimized cross correlation identification to obtain velocity vectors is implemented with direct calculation of correlation coefficients. Fine optical setup concerned with PIV performance is arranged for the accurate PIV measurement of high-speed complex flow. Variable flow pattern are represented quantitatively at the stator region.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.177-178
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• 2006

Digital holographic particle tracking velocimetry (HPTV) is developed by single high-speed camera and single continuous laser with long coherent length. This system can directly capture 4000 hologram fringe images for 1 second through a camera computer memory. The 3D particle location is made of the reconstruction by using a computer hologram algorithm. This system can successfully be applied to instantaneous 3D velocity measurement in the water flow inside a micro-tube. The average of 100 instantaneous velocity vectors is obtained by reconstruction and tracking with the time of evolution of recorded fringes images. In the near future, we will apply this technique to measure 3D flow information inside various micro structures.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.375-376
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• 2006

Turbulent structure of a boundary-layer over a flat plate coated with micro riblet film(MRF) has been investigated experimentally. The turbulent structure was visualized using a dynamic particle image velocimetry (Dynamic PIV) system. We identified the vortex structures from 2-D velocity field data by applying the complex eigenvalue definition. The velocity field images acquired by using the complex eigenvalue definition showed the whole 2-D vortex structures clearly. In addition, the spatial distributions of small-scale vortices as well as large-scale vortices were obtained with high accuracy. The difference of vortex structures between the MRF coated flat plate and the smooth flat plate was analysed in detail. With varying upstream flow speed, the characteristics of vortex structure over the MRF coated flate plate was compared with those over the smooth flat plate.