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고속철도 터널입구에서 형성되는 압축파의 특성에 관한 연구
김희동,김태호,이종수,김동현,Kim, Heuy-Dong,Kim, Tae-Ho,Lee, Jong-Su,Kim, Dong-Hyeon 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.2
Flow phenomena such as the pressure transients Inside a high-speed railway tunnel and the Impulsive waves at the exit of the tunnel are closely associated with the characteristics of the entry compression wave, which is generated by a train entering the tunnel. Tunnel entrance hood may be an effective means for alleviating the Impulsive waves and pressure transients. The objective of the current work is to explore the effects of the train nose shape and the entrance hood on the characteristics of the entry compression wave. Numerical calculations using the method of characteristics were applied to one-dimensional, unsteady, compressible flow field with respect to high-speed railway/tunnel systems. Two types of the entrance hoods and various train nose shapes were employed to reveal their influences on the entry compression wave for a wide range of train speeds. The results showed that the entry compression wave length increases as the train nose becomes longer and the train speed becomes lower. The entry compression wave length in the tunnel with hood becomes longer than that of no hood. Maximum pressure gradient in the compression wavefront reduces by the entrance hood. The results of the current work provide useful data for the design of tunnel entrance hood.
김희동,김태호,김동형,Kim, Heuy-Dong,Kim, Tae-Ho,Kim, Dong-Hyeon 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.1
The entry compression wave, which forms at the entrance of a high-speed railway tunnel, is closely related to the pressure transients in the train/tunnel systems as well as an impulsive noise appearing at the exit of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Optimum hood shape necessary to reduce the pressure transients and impulsive noise was found to be of an abrupt type hood with its cross-sectional area 2.5 times the tunnel area. It is believed that the current results are highly useful in predicting the effects of entrance hoods and in choosing the shape of proper hood.
김희동,Kim, Heuy Dong 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.9
Experiments of shock-wave/turbulent boundary layer interaction were conducted by using a supersonic wind tunnel. Nominal Mach number was varied in the range of 1.6 to 3.0 by means of different nozzles. The objective of the present study is to investigate the effects of boundary layer suction on normal shock-wave oscillations caused by shock wave/boundary layer interaction in a straight duct. Two-dimensional slits were installed on the top and bottom walls of the duct to bleed turbulent boundary layer flows. The bleed flows were measured by an orifice. The ratio of the bleed mass flow to main mass flow was controlled below the range of 11 per cent. Time-mean and fluctuating wall pressures were measured, and Schlieren optical observations were made to investigate time-mean flow field. Time variations in the shock wave displacement were obtained by a high-speed camera system. The results show that boundary layer suction by slits considerably reduce shock-wave oscillations. For the design Mach number of 2.3, the maximum amplitude of the oscillating shock-wave reduces by about 75% compared with the case of no slit for boundary layer suction.
김희동,Kim, Heuy-Dong,Matsus, Kazuyasu 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.10
Experiments of shock wave/turbulent boundary layer interaction were conducted by using a supersonic wind tunnel. Nominal Mach number was varied in the range of 1.6 to 3.0 by means of different nozzles. The objective of the present study is to investigate the effects of boundary layer flow bleed on the interaction flow field in a straight tube. Two-dimensional slits were installed on the tube walls to bleed the turbulent boundary layer flows. The bleed flows were measured by an orifice. The ratio of the bleed mass flow to main mass flow was controlled within the range of 11 per cent. The wall pressures were measured by the flush mounted transducers and Schlieren optical observations were made for almost all of the experiments. The results show that the boundary layer flow bleed reduces the multiple shock waves to a strong normal shock wave. For the design Mach number of 1.6, it was found that the normal shock wave at the position of the silt was resulted from the main flow choking due to the suction of the boundary layer flow.
Numerical simulation on characteristics of particle-gas flows in supersonic impinging jet
Heuy Dong Kim(김희동),Guang Zhang,Yingzi Jin,Toshiaki Setoguchi 한국가시화정보학회 2016 한국가시화정보학회 학술발표대회 논문집 Vol.2016 No.4
The supersonic impinging jets always occur when crafts are starting short takeoff and vertical landing from the ground. The adverse flow conditions happen to decrease the performance of aircrafts, such as impinging force, high noise spectrum and high shear stresses. Due to rare results on particle-gas impinging jet flows to date, numerical simulations were performed to investigate the supersonic impinging jet flows of particle-gas two phases in the present studies. Convergent-divergent supersonic and convergent sonic nozzles were used to induce the supersonic jet flows. Discrete phase model (DPM) was used to simulate the particle-gas flows. Different particle diameters were investigated. The flow Mach number and pressure coefficients on the ground surface were obtained to describe phenomena inside impinging and wall jet flows. The particle motion was obtained in details from the present simulations.
고속열차의 선두부 형상이 터널 입구압력파에 미치는 영향
김희동(Kim Heuy-Dong),김태호(Kim Tae-Ho),서태원(Seo Tae-Won) 한국철도학회 1998 한국철도학회 학술발표대회논문집 Vol.- No.-
The entry compression wave, which is generated at the entrance of the tunnel, is almost always associated with the pressure transients in the tunnel as well as the impulse noise at the exit of the tunnel. It is highly required to design the train nose shape that can minimize such undesirable phenomena. The objective of the current work is to investigate the effects of the train nose shape on the entry compression wave. Numerical computations were applied to one-dimensional unsteady compressible flow in high-speed railway train/tunnel systems. A various shape of train noses were tested for a wide range of train speeds. The results showed that the strength of the entry compression wave is not influenced by the train nose shape, but the time variation of pressure in the entry compression wavefront is strongly related to the train nose shape. The current method of the characteristics was able to represent a desirable nose shape for various train speeds. Optimum nose shape was found to considerably reduce the maximum pressure gradient of the entry compression wave.