• Journal of Environmental Science International
• /
• v.31 no.1
• /
• pp.33-42
• /
• 2022

The objective of this study is to determine the appropriate size of the inlet pipe diameter and thereby conduct hydraulic analysis for the Korean water distribution network. To this end, the data tables for equivalent pipe diameters and outflow rates presently employed in Korea were adopted. By incorporating the table of equivalent pipe diameters, it was found that the size of the inlet pipe diameter was overestimated, which can cause shortage of water pressure and malfunctioning or insufficiency of outflow rate in the corresponding adjacent region. However, by conducting hydraulic analysis based on the table of outflow rates, relatively reasonable flow rates were observed. Furthermore, by comparing the real demand-driven analysis (RDDA) approach and demand-driven analysis (DDA) approach toward managing the huge water demand, it was observed that DDA could not effectively respond to real hourly usage conditions, whereas RDDA (which reflects the hourly effects of inlet pipe diameter and storage tanks) demonstrated results similar to that of real water supply.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.1
• /
• pp.74-80
• /
• 2009

In this study, the static and modal analyses to find the characteristic of eigenvalues for a towed cable were with a free boundary condition at the bottom end carried out with numerical study. The resulting numerical code with finite element method was used to study sample problems for a cable with towing speeds. After tracing the equilibrium state with a towing speed through the static analysis, modal analysis on the basis of static results was performed. The static top tension for a critical towing speed is nearly 50 percent of what it was for a free hanging pipe. From static analyses, it is found that towing speed has a noticeable effect on top tension of a towed pipe. At a high towing speed, differences between the first and second periods become larger. Compared to the fundamental period for a free hanging pipe, that for a towed pipe with a critical towing speed is approximately 1.4 times larger. This result is very important point in that the lock in condition and tension of the towed cable system with top excitation can be predicted. The corrected close form solution to solve natural periods for a towed cable was presented in this study. The code is validated by comparison of the results of theoretical and numerical studies. Two results were in very good agreement. This study can contribute to predicting the lock-in condition and tension for a towed cable or pipe with top excitation.

• Journal of the Korean Society of Safety
• /
• v.12 no.3
• /
• pp.83-89
• /
• 1997

The behaviors of flame propagation and quenching ability in a pipe were investigated to make a design criteria of flame arrester. The effects of the number of wire gauzes and free area on the quenching ability were discussed. Experimental results showed that the flame velocity was important factor of the quenching ability. The flame velocity in case of closed pipe was increased about twenty times faster then that of opened. The quenching ability was increased about 10% with 3% decrease of free area and it was changed significantly by the sealing condition of the pipe end. The quenching flame velocity can be estimated by using experimental equations.

• 한국가시화정보학회:학술대회논문집
• /
• 2003.11a
• /
• pp.95-98
• /
• 2003

When a shock wave discharges from an open end of a duct, an impulse wave is generated outside the duct, causing serious noise and vibration problems. The magnitude of the impulse wave can be reduced by installing of a perforated duct. In the current study, the characteristics of the impulse wave discharged from the exit of a perforated duct are numerically investigated. A TVD (total variation diminishing) scheme is used to solve the unsteady, axisymmetric, compressible Euler equations. In computations, the porosity of a perforated pipe $(\sigma)$ and the Mach number of incident shock wave $(M_s)$ are varied in the range of $\sigma=0\~19\%\;and\;M_s=1.01\~1.50$, respectively. The results show that the directivity and magnitude of impulse wave strongly depend upon the Mach number of incident shock wave and the porosity of the perforated pipe. The present CFD results are in close agreement with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.852-855
• /
• 2004

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a straight pipe attached to the open end of a simple shock tube. The sound pressure level and directivity of the impulse noise propagating from the exit of pipe with several different diameters are measured in the far sound fold for the range of the incident shock wave Mach number between 1.07 and 1.26. The experimental results showed that the peak values of impulse noises had a strong dependance on the exit diameter of a pipe and the shock wave Mach number. The impulse noise had the directivity propagating toward to the pipe axis and the characteristics of inverse square law of propagation distance. Moreover, it was shown that the one-third octave band SPL of impulse noise was almost constant regardless of the frequency band.

• Journal of the Korean Society of Safety
• /
• v.12 no.4
• /
• pp.191-200
• /
• 1997

This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

• Journal of Power System Engineering
• /
• v.14 no.3
• /
• pp.46-51
• /
• 2010

A torsional guided wave was applied to detect a defect in petrochemical pipes. Phase and group velocity dispersion curves for the longitudinal and torsional modes of the inspected pipe were presented for the theoretical analysis. It was found through mode shape analysis that there was mode conversion when torsional wave is incident at an asymmetric defect. An artificial notch was fabricated in the pipe and the detectability was examined from the distance 2m of the end of the pipe by using magnetostrictive sensors. The relativities between the amplitude of the reflected signal and the size of the defect was examined. It was shown that the T(0,1) mode could be used for the long range inspection for the petrochemical pipes.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.829-834
• /
• 2000

This paper is primarily directed toward analyzing the transient response characteristics in hydraulic pipe lines. The exact solution to the transient response characteristics was obtained by using the complicated transfer function derived by Iberall. The discrepancy with the exact and approximate is small, so the approximate solution is adopted to the theoretical one. An equation was derived which describes the pressure times relationship Hat occurs at the end of volume terminated transmission line following a sudden pressure change at its inputs. As a result, It is found that the density has relationship about the Wave Propagation is very useful in analyzing the transient response characteristics of hydraulic pipe lines. The velocity of Pressure wave Propagation decreases as the density of fluid increased.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.2
• /
• pp.13-19
• /
• 2008

A camprehensive review of the expansion behavior of marine pipelines due to thermal and pressure change is presented based on research work over the last 10 years. The review is organized into five main sections, namely free expansion with uniform temperature, free expansion with temperature gradient, expansion with end restraints, expansion of pipe-in-pipe system, and lateral deviation (snaking). Based on the accumulated knowledge of the interactions between the soil and pipeline behavior, a whole pipeline system can be modeled by an accurate finite element method (FEM). This methodology requires a comprehensive understanding and engineering verification of the expansion behavior of marine pipelines.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.03a
• /
• pp.589-596
• /
• 2002

In this study, static pile load tests with load transfer measurement were accomplished in the field. Yield pile capacity (or ultimate pile capacity) determined by load-settlement-time relationship was determined and axial load transfer behavior was analyzed. In the test for the four test piles were behaved as end bearing pile but ratios of skin friction to total pile capacity were 27%∼33%.