• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.433-434
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• 2006

The limited slip differential(LSD) is a device which enables the driving force to be transmitted from one slipping wheel to another wheel in such case that the car is stuck in clay or snow. When the unwanted slipping occurs on one wheel, the LSD temporarily restraints the differential motion to transmit the driving force in the other wheel. So far, many types of LSD were developed such as mechanical lock type, disk clutch type, viscous coupling type, torsion type and multiple clutch type. we designed a new type of the hydraulic LSD which uses the principle of trochoid gear pump.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.131-136
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• 2004

The limited slip differential(LSD) is a device which enables the driving force to be transmitted from one slipping wheel to another wheel in such case that the car is stuck in clay or snow. When the unwanted slipping occurs on one wheel, the LSD temporarily restraints the differential motion to transmit the driving force in the other wheel. So far, many types of LSD were developed such as mechanical lock type, disk clutch type, viscous coupling type, torsion type and multiple clutch type. However these types of LSD is too complicated and expensive, so it is used only for 4WD outdoor vehicles, military vehicles, and a portion of deluxe car. So, many studies has been devoted to improve new types of LSD to cover those demerits of existing LSDs that the hydraulic LSD is developed as arepresentative result of that. The hydraulic LSD which uses the principle of gear pump is packed with viscous oil in tight container. When a slip occurs on one wheel, the hydraulic LSD generates torque caused by high oil pressure in the container. This study has been devoted to suggest an improved hydraulic LSD. In order to achieve it, we designed a new type of hydraulic LSD, produced it and did a rig test with it on real vehicle. From the rig test, it has been confirmed that the new type of hydraulic LSD can be directly applied to exiting vehicles without changing the design criteria

• 대한기계학회논문집
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• 제15권1호
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• pp.163-168
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• 1991

본 연구에서는 여러가지의 성형조건에서 미끄름을 지배하는 상수를 측정하고, 유동 선단(flow front)에 미치는 이 상수의 영향을 검토한다. 또 측정된 상수를 가 지고 사각형 및 중공 원형 평판 압축성형에 대해서 2차원 유한 요소해석을 하고 실험 결과와 비교 검토한다.

• 한국전산유체공학회지
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• 제4권1호
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• pp.1-7
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• 1999

The numerical methodology for computing tile impact forces and water entry behaviors of high speed water entry bodies was been developed. Since the present method assumed the impact occurs within a very short time interval. the viscous effects do not have enough time to play a significant role in the impact forces, that is, the flow around a water-entry object was assumed as an incompressible potential flow and is solved by the source panel method. The elements fully submerged into the water are routinely treated, but the elements intersected by the effective planar free surface are redefined and reorganized to be amenable to the source panel method. To validate the present code, it was applied to disk, cone and ogive model and compared with experimental data. Good agreement was obtained. The water entry behavior such as the bouncing phenomena from the free surface was also simulated using the impact forces and two degree of freedom dynamic equation. Physically acceptable results were obtained.

• 한국전산유체공학회지
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• 제6권3호
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• pp.32-40
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• 2001

Viscous solutions of supersonic jet impinging on a flat plate normal to the flow are simulated using three-dimensional Navier-Stokes solver. The jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. In the present study, the nozzle contour and the pressure ratio are held fixed, while the jet impinging distance is varied to illuminate the characteristics of the jet plume with the distance. As the plate is placed close to the nozzle at 3D high, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. Here D is the nozzle exit diameter. The amplitude of wall pressure fluctuations subsides as the distance increases, but the maximum mean pressure level at the plate is achieved when the distance is about 4D high. The frequency of the wall pressure is estimated at 6.0 kHz, 9.3 kHz, and 10.0 kHz as the impinging distance varies from 3D, 4D, to 6D, respectively.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.804-816
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• 2021

This paper investigates the effect of different flow models on the Pre-Swirl-Stator structural response from the perspective of a non-existing unified design procedure. Due to viscous effects near the propeller plane, the hydrodynamic solution is calculated by Computational Fluid Dynamics (CFD). Three different models are analysed: without the propeller, with the actuator disk and with the propeller. The main intention of this paper is to clarify the effects of the propeller model on the structural stresses in calm-water and waves which include the ship motion. CFD simulations are performed by means of OpenFOAM, while the structural response is calculated by means of the Finite Element Method (FEM) solver NASTRAN. Calm-water results have shown the inclusion of the propeller necessary from the design perspective, while the wave simulations have shown negligible propeller influence on the resulting stresses arising from the ship motions.

• 대한조선학회논문집
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• 제60권4호
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• pp.240-247
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• 2023

In this study, morphological and hydrodynamic characteristics of the non-axisymmetric supercavity generated behind a disk-shaped cavitator were examined. By extending the previous study on axisymmetric supercavitating flow based on a boundary element method, hydrodynamic forces acting under the angle of attack condition of 0 to 30 ° and shape characteristics of the supercavity were analyzed. The results revealed that increasing the angle of attack by 30 ° reduced the length and width of the cavity by about 15% and the volume by about 40 %. An empirical formula that can quantitatively estimate the geometrical characteristics and change of the cavity was derived. It is expected that this method can be used to evaluate the shape information and force characteristics of the supercavity for the control of the vehicle in a very short time compared to the viscous analysis in the initial design stage of the supercavity underwater vehicle.

• Advances in nano research
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• 제16권4호
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• pp.325-340
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• 2024

There are several novel uses for dispersing many nanoparticles into a conventional fluid, including dynamic sealing, damping, heat dissipation, microfluidics, and more. Therefore, melting heat and mass transfer characteristics of a 3-D MHD Hybrid Nanofluid flow over a rotating disc with presenting dufour and soret effects are assessed numerically in this study. In this instance, we investigated both ferric sulfate and molybdenum disulfide as nanoparticles suspended within base fluid water. The governing partial differential equations are transformed into linked higher-order non-linear ordinary differential equations by the local similarity transformation. The collection of these deduced equations is then resolved using a Chebyshev spectral collocation-based algorithm built into the Mathematica software. To demonstrate how different instances of hybrid/ nanofluid are impacted by changes in temperature, velocity, and the distribution of nanoparticle concentration, examples of graphical and numerical data are given. For many values of the material parameters, the computational findings are shown. Simulations conducted for different physical parameters in the model show that adding hybrid nanoparticle to the fluid mixture increases heat transfer in comparison to simple nanofluids. It has been identified that hybrid nanoparticles, as opposed to single-type nanoparticles, need to be taken into consideration to create an effective thermal system. Furthermore, porosity lowers the velocities of simple and hybrid nanofluids in both cases. Additionally, results show that the drag force from skin friction causes the nanoparticle fluid to travel more slowly than the hybrid nanoparticle fluid. The findings also demonstrate that suction factors like magnetic and porosity parameters, as well as nanoparticles, raise the skin friction coefficient. Furthermore, It indicates that the outcomes from different flow scenarios correlate and are in strong agreement with the findings from the published literature. Bar chart depictions are altered by changes in flow rates. Moreover, the results confirm doctors' views to prescribe hybrid nanoparticle and particle nanoparticle contents for achalasia patients and also those who suffer from esophageal stricture and tumors. The results of this study can also be applied to the energy generated by the melting disc surface, which has a variety of industrial uses. These include, but are not limited to, the preparation of semiconductor materials, the solidification of magma, the melting of permafrost, and the refreezing of frozen land.

• 한국군사과학기술학회지
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• 제4권2호
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• pp.256-262
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• 2001

Viscous solutions of supersonic side jet nozzle and supersonic jet impinging on a flat plate are simulated using three-dimensional Navier-Stokes solver. For rapid and abrupt control of a missile in supersonic flight, side jet on a missile body is found to be a useful devise as evidenced by recent missile development at several nations. The magnitude of the side jet and the duration of it decide the level of control of such a missile system. The aerodynamic characteristics of the side jet devise itself are examined in terms of key parameters such as the side jet nozzle geometry, the chamber pressure and temperature. On the other hand, the jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. As the plate is placed close to the nozzle, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. The amplitude of wall pressure fluctuations subsides as the plate/nozzle distance increases, and the frequency of the wall pressure is estimated on the order of 10.0 KHz. Objectives of this paper are to show accurate simulation of nozzle flow itself and to demonstrate the jet flow structure when the jet interacts with a wall at a close range.

• Tribology and Lubricants
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• 제30권2호
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• pp.108-115
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• 2014

The friction behaviors of bulk amorphous thermal spray coating (BAC) and second phase-reinforced composite coatings using a high velocity oxy-fuel spraying process were investigated using a ball-on-disk test rig that slides against a ceramic ball in an atmospheric environment. The surface temperatures were measured using an infrared thermometer installed 50 mm from the contact surface. The crystallinities of the coating layers were determined using X-ray diffraction. The morphologies of the coating layers and worn surfaces were observed using a scanning electron microscope and energy-dispersive spectroscopy. The results show that the friction behavior of the monolithic amorphous coating was sensitive to the testing conditions. Under lower than normal loads, a low and stable friction coefficient of about 0.1 was observed, whereas under a higher relative load, a high and unstable friction coefficient of greater than 0.3 was obtained with an instant temperature increase. For the composite coatings, a sudden increase in friction coefficient did not occur, i.e., the transition region did not exist and during the friction test, a gradual increase occurred only after a significant delay. The BAC morphology observations indicate that viscous plastic flow was generated with low loads, but severe surface damage (i.e., tearing) occurred at high loads. For composite coatings, a relatively smooth surface was observed on the worn surface for all applied loads.