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노우진(Ujin Roh),심영삼(Youngsam Shim),천무환(Muhwan Chon) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
When the conceptual design phase or the modification design phase, it is essential to confirm realistic predictions of the 1-D air distribution ratio inside the combustor which has the complicated geometry. This accurate initial design would make that the less time is spent on following design period like 3-D CFD analysis and test. There are many research which have performed on the internal flow but these researches have focused on the simple shape like a circular pipe, an annular pipe, an orifice and so on. However, the configuration of the gas turbine combustor does not consist of simple configurations. Therefore, many researches have focused on the way to simplify the combustor geometry and on the correlation for the real combustor configurations. The purpose of this study is to verify the 1-D flow network modeling using the effective area test and define the air distribution ration of the combustor. The commercial 1-D network tool, ‘Flowmaster’ is used for 1D flow network modeling.
노우진(Woo-Jin Roh),이종원(Chong-Won Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
This paper reviews and develops green dynamics, and the run of a golf ball. We analyze green dynamics using stimpmeter and Werner and Greig's empirical equations. Reasonable empirical equations are suggested to satisfy mechanical principles. The resistance moment is calculated to find rolling resistance of a golf ball on the green. Then, the rolling friction coefficient is deduced using previous results. Finally, it is found that the bounce form of forward or backward is caused by landing backspin and the coefficient of kinetic friction.
노우진(Woo-Jin Roh),이종원(Chong-Won Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In a previous study, the motion of a rolling golf ball on a sloped green was modeled. In this paper, the equation of motion for a golf ball interacting with a hole on a sloped green are found. The capture process is studied by numerically solving the equations for rolling without slipping on the rim.
노우진(U Jin Roh),임주현(Ju Hyun Im),송성진(Seung Jin Song) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.5
Bent duct 는 손실을 가중시키고, 효율을 저하시킨다. 지금까지 bent duct에 대한 많은 연구가 진행되었지만, 입구와 출구가 같은 형상에 대해서 연구가 되어왔다. 이번 연구에서는 입구는 환형이지만, 출구는 원형을 가진 bent duct에 대해서 진행되었다. 입구 속도 54 m/s, 레이놀즈수 238,000에서 수행된 이번 연구에서는 bent duct 바깥에 태핑홀을 배치하여 정압분포를 확인하고, 입구와 출구에서 5공 프로브로 유동을 측정하여 스트림 방향 속도 프로파일과 전압 손실 계수를 얻었다. 본 연구에서는 전압 손실 계수, 0.243를 얻었다. Bent ducts add loss and decrease efficiency. Many researchers have been conducted the performances of bent ducts, but their shapes of inlet and outlet are same. However, in this investigation, the focus is on a bent duct which is annular at the inlet and circular at the outlet. The bent duct of these complex shapes has not been investigated, but has been used in many fields. The performance of such bent duct is investigated under inlet speed 54 m/s and Re = 238,000. Wall static pressure tappings are located surface of the bent duct to measure the static pressure and a probe is traversed at the inlet and outlet of the bent duct to measure the total pressure. As a result, it presents static pressure distribution on the bent duct surface, streamwise velocity profile at inlet and outlet of the bent duct and total pressure loss profile at outlet. In this investigation, the total pressure loss coefficient is 0.243.
노우진(Roh, Woo-Jin),이종원(Lee, Chong-Won) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.5
It is important to improve the initial launch conditions of golf ball at impact between golf club and ball to get a long flight distance. The flight distance is greatly influenced by the initial launch conditions such as ball speed, launch angle and back spin rate. It is also important to analyze the mechanism of ball spin to improve the initial conditions of golf ball. Back spin rate is created by the contact time and force. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of ball, and the tangential force creates the spin. Especially, the tangential force is known to take either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail in the literature. In this paper, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and time at impact between golf club head and ball are computed using FEM and compared with previous results. In addition, we investigate the impact phenomenon between golf club head and ball by FEM and clarify the mechanism of ball spin creation accurately, particularly focusing on the effect of negative tangential force on ball spin rate.
노우진(Roh, Woo-Jin),이종원(Lee, Chong-Won) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.11
Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.