• Journal of the Korean Society of Visualization
• /
• v.8 no.2
• /
• pp.40-44
• /
• 2010

Thermal comfort inside a passenger car has been receiving large attention in automobile industries. Especially, the performance of windshield defroster is important in the design of a car to ensure passenger comport and safety. Thereby, better understanding on the ventilation flow along the vehicle windshield is essential to evaluate the performance of windshield defroster. However, most previous studies dealt with the defrost flow using CFD (computational fluid dynamics) calculations or scale-down model experiments. In this study, a real commercial automobile was used to investigate the flow discharged from the vehicle defroster and the ventilation flow along the windshield using a PIV velocity field measurement technique. The experimental data would be useful to understand the flow characteristics in detail and also can be used to validate numerical predictions.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.141-142
• /
• 2003

When the under-expanded supersonic jet impinges on the perpendicular plate, it is well known that the self-induced flow oscillation occurs at the specific conditions. This phenomenon is related with the noise problems of aeronautical and other industrial engineering. But, the very complicated flow field is formed and it is difficult to clear the flow structure and the mechanism of oscillation. This paper aims to clear the characteristics of flow field and the wave pattern during the under-expanded supersonic jet impinges on the plate. The numerical calculation was carried out using the TVD numerical method. In this paper, the flow visualization, the pressure fluctuation on the surface of plate and the mechanism of oscillation are discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.4
• /
• pp.368-373
• /
• 2004

A flow field in a passage with periodically converging-diverging cross-section is investigated experimentally by PIV measurement. A tube with a sinusoidally wavy cross section is one of several devices employed for enhancing the heat and mass transfer efficiency due to turbulence promotion and unsteady vortical motion. While the numerical flow visualization results have been limited to the fully developed cases, existing experimental results of this flow were simple qualitative ones by smoke or dye streak test. Therefore, the main purpose of this study is to produce quantitative flow data for fully developed and transient flow regime by the Correlation Based Correction PIV (CBC PIV) and to conjecture the analogy between flow characteristics and heat transfer enhancement with low pumping power. Another purpose of this paper is to examine the onset position of the transition and the global mixing, which results in transfer enhancement. At Re=2000, evidences of the global mixing are captured at 2.5 wavy module through the variation of RMS values and instantaneous velocity plot.

• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.5
• /
• pp.589-596
• /
• 2006

This study aims to propose a new model axial flow fan which attachs centrifugal blades, and to investigate the effect of centrifugal blades on the performance improvement of new model axial flow fan. A numerical simulation has been conducted using STAR-CD commercial code to solve the three dimensional incompressible Navier-Stokes equation for high Reynolds number $k-{\epsilon}$ turbulent model. Numerical simulation is carried out to investigate the detail phenomenon in the flow field and performance characteristics of new model and normal model fan. Calculation results are compared with normal model's results to investigate which centrifugal blades effect on velocity profile and pressure distribution at various flow field positions. and calculation results show that new model fan can improve the performance of total pressure.

• Journal of the Korean Society of Visualization
• /
• v.9 no.3
• /
• pp.24-29
• /
• 2011

The improvement of climatic comfort is crucial not only for passenger comfort but also for driving safety. Therefore, a better understanding on the flow characteristics of ventilation flow inside the passenger compartment is essential. Most of the previous studies investigated the ventilation flow using Computational Fluid Dynamics (CFD) calculations or scale-down water-model experiments. In this study, the ventilation flow inside the passenger compartment of a real commercial automobile was investigated using a Particle Image Velocimetry (PIV) velocity field measurement technique. Under real operating conditions, the velocity fields were measured at several vertical planes for several ventilation modes. The experimental data obtained from this study can be used to understand the detailed flow characteristics in the passenger compartment of a real car and to validate numerical predictions.

• Journal of the Korean Society of Visualization
• /
• v.5 no.2
• /
• pp.48-55
• /
• 2007

Flow structure inside a refrigerating compartment of a scale-down display cooler model was investigated experimentally by using PIV (particle image velocimetry) method, a reliable velocity field measurement technique, in the present study. In addition, we also carried out flow visualization regarding flow structure and particle movement inside a display cooler by using a tracer method. As a result, the mean velocity field measurement shows a large scale vortical flow structure inside a refrigerating compartment due to strong entrainment flow, going through a base plate open gaps.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.1002-1006
• /
• 2006

The noise of a refrigerator is consisted of the various flow noises of a refrigerator fan, a compressor and a condenser fan. The demands of high flow rate, compact space and low noise are to be accommodated, especially, in the case of a premium refrigerator. In this study, flow field, noise sources and flow noise are analyzed numerically and compared to the measured data. The flow field is calculated with 3-dimensional CFD solver - SC/Tetra, and the noise source and aeroacoustic noise is analyzed with FlowNoise S/W. Low noise axial fan can be developed by controlling the dominant noise source area.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.9
• /
• pp.799-807
• /
• 2005

The flow characteristics and the heat transfer rate on a surface by the interaction of a pair of vortices are studied numerically. To analyze the common flow up produced by vortex generators in a rectangular channel flow, the pseudo-compressibility viscous method is introduced into the Reynolds-averaged Navier-Stokes equation for 3-dimensional unsteady, incompressible viscous flows. To predict turbulence characteristics, a two-layer $k-\varepsilon$ turbulence model is used on the flat plate 3-dimensional turbulence boundary The computational results predict accurately Reynolds stress, turbulent kinetic energy and flow field generated by the vortex generators. The numerical results, such as thermal boundary layers, skin friction characteristics and heat transfers, are also reasonably close to the experimental data.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.8 no.2
• /
• pp.11-22
• /
• 2000

Holographic interferometric tomography can provide reconstruction of instantaneous three-dimensional gross flow fields. The technique however confronts ill-posed reconstruction problems in practical applications. Experimental data are usually limited in projection and angular scanning when a field is captured instantaneously or under the obstruction of test models and test section enclosures. An algorithm, based on a series expansion method, has been developed to improve the reconstruction under the ill-posed conditions. A three-dimensional natural convection flow around two interacting isothermal cubes is experimentally investigated. The flow can provide a challenging reconstruction problem and lend itself to accurate numerical solution for comparison. The refractive index fields at two horizontal sections of the thermal plume with and without an opaque object are reconstructed at a limited view angle of 80$\circ$. The experimental reconstructions are then compared with those from numerical calculation and thermocouple thermometry. It confirms that the technique is applicable to reconstruction of reasonably complex, three-dimensional flow fields.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.35-38
• /
• 2002

Variations of temperature and velocity fields in a Hele-Shaw Convection Cell (HSC) were measured using a holographic interferometry and PIV technique with varying Rayleigh number. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow at high Rayleigh numbers. Two different measurement methods of holographic interferometry, double-exposure method and real-time method, were employed to measure the temperature field variations of HSC convective flow. In the double-exposure method, unwanted waves can be eliminated and reconstruction images are clear, but transient flow structure cannot be observed clearly. On the other hand, transient flow can be observed and reconstructed well using the real-time method. PIV results show that flow inside the HSC is periodic and the oscillating state is well matched with the temperature field results. The holographic interferometry and PIV techniques employed in this study are useful for analyzing the unsteady convective thermal fluid flows.