• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.66-66
• /
• 2017

Hydraulic jump is typically designed to occur over low-haed dam spillways and weirs in the river. An important engineering application of the hydraulic jump is to dissipate the intense kinetic energy of the flows over such hydraulic structures. Turbulent flow and roller-like vortex riding up the free sureface of the jump cause most of the energy dissipation. We carry out a high resolution three-dimensional numerical simulations of a submerged hydraulic jump in a spillway and compare numerical results with a laboratory measurement obtained by the PIV. The numerical results further show the dynamic behavoirs of the inner and outer layers of the submerged wall-jet and the recirculating roller of the hydraulic jump.

• Journal of Korean Society of Water and Wastewater
• /
• v.22 no.3
• /
• pp.389-396
• /
• 2008

The hybrid model can be used to predict the initial near field mixing and the far field transport of the buoyant jets, which are discharged from the submerged wastewater ocean outfall. In the near field, the jet integral model can be used for single port diffusers while the ${\sigma}$ transformed particle tracking model was used in the far field. In this study, the experimental study was performed to verify the developed hybrid model in the previous research. The developed hybrid model properly predict the surface and vertical concentration distribution of the single buoyant jets with various effluent and ambient conditions. The hybrid model can also simulate the surface concentration distribution of the rosette diffuser except for the parallel diffuser with the higher densimetric Froude number due to the assumption that dynamic effects of the effluent plumes are negligible in the far field. The application of the hybrid model to rosette diffusers can predict the concentration near the diffuser more accurately when the line-plume approximation is used.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.6
• /
• pp.1043-1048
• /
• 2012

We have researched the changes of paddy soil properties and rice yield by several different methods to treated with liquid pig manure(LPM). In the execution of this experiment, rice was cultivated to full maturity at a paddy field in Jeollabuk-do in 2011. Field experiment was designed with surface application on dry field condition+jet hose spray(Tr. 1), surface application on dry field condition+incorporation with irrigation water(Tr. 2), surface application on dry field condition+application device of fertilizer through irrigation(Tr. 3), submerged application on irrigated field condition+jet hose spray(Tr. 4), submerged application on irrigated field condition+incorporation with irrigation water(Tr. 5) and submerged application on irrigated field condition+application device of fertilizer through irrigation(Tr. 6) plot. Total N, P, K contents in used LPM were 0.44%, 0.07% and 0.14%, respectively. After the experiment, soil properties were not significant difference both several treated plots. But $NO_3$ and $NH_4$ contents at incorporation with irrigation water plots in paddy soil were higher than other plots. The yield was 602 kg $10a^{-1}$ in Tr. 2 plot compared Tr. 6 plot, which showed a value of 9.6% higher.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.4
• /
• pp.123-129
• /
• 1993

Because the existing scour prediction formulas for plunge pools of pipe culverts and spillways give a wide range of predicted scour depths, it is difficult to estimate actual scour depths. A review of literature showed that wide range of predicted values was caused mostly by lack of thorough analysis of the scour mechanism. In this study, the effects of the parameters govering scour were examined, and the scour potentials were measured. The major variables govering scour were the velocity and size of jet impinging into the plunge pool, the submerged weight of bed material, the ratio of jet size to bed material size, the tail watr depth of the plunge pool, and the angle of jet impact on water surface. The ratio of jet size to bed material size to bed material size was found to be another significant parameter affecting scour for larger bed materials. A densimetric Froude nember of the bed material in incipient motion was formulated. This number represented the scour potential of the jet at the point where the bed material was tested.

• Korean Journal of Ecology and Environment
• /
• v.49 no.2
• /
• pp.124-129
• /
• 2016

This study was conducted to suggest the cause analysis and mitigation measures of foaming generated in the effluent of wastewater treatment plant. The foam generated in the outlet connected with the tidal river system was identified as structural problems. And the main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. In consideration of these conditions, it present the effective ways such as micro-screen and submerged outlet, to mitigate the foaming generated in the water channel and outlet end.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.6 no.2
• /
• pp.45-52
• /
• 2002

An experimental investigation on the structure and dynamic behavior of two dimensional over-expanded air jets exiting into water was carried out. The hish speed digital video imaging and static pressure distribution measurement were made to characterize the structure and time-dependant behavior of the jets. Mach number at the jet exit was 2.0 and was slightly less than the value predicted by the ideal nozzle calculation. Variance of jet spreading angle at different stagnation condition was measured as a function of mass flow rate. Periodic nature of the air jet distortion in water was observed and the frequency of the repetition was approximately 5-6 Hz for all cases tested. Three characteristic length scales were defined to characterize jet structure. $L_1$, maximum width of the plume when the periodic instability occurs, $L_2$, width of the jet where secondary reverse flow entrained jet flow and $L_3$, distance from the jet exit to the location where entrainment of the secondary reverse flow occurs. The ratio of $L_1$ and $L_2$ decreased with increasing stagnation pressure, i.e. mass flow rate. $L_3$ increased with increasing stagnation pressure. The temporal behavior of static pressure measurements also showed peak around frequency of 5, which corresponds the frequency obtained by visual measurements

• Journal of Korea Water Resources Association
• /
• v.52 no.2
• /
• pp.115-123
• /
• 2019

The effects of the Froude numbers on turbulent flow patterns downstream of a non-submerged spur dike were investigated in a laboratory flume. Three-dimensional velocities and water depths were measured using Acoustic Doppler Velocimetry and distance sensors under three Froude number conditions ($Fr_d=0.31$, 0.38, and 0.46). The results show that there are marginal differences in the velocity fields downstream of a spur dike due to the change of the Froude number. However, an increase of the Froude number was found to reduce cross-sectional area in the flow and to increase the strength of the jet-like flow. The jet-like flow was observed to displace the location of the maximum turbulence kinetic energy within a cross section toward the inner bank in the transverse direction.

• Journal of Korean Society on Water Environment
• /
• v.20 no.4
• /
• pp.365-369
• /
• 2004

Submerged membrane bio-reactor equipped with a hollow fiber microfiltration was applied to reuse weaving wastewater of water jet loom, where two parameters such as the concentration of MLSS and the flux were controlled. While the flux at the concentration of MLSS around 900mg/L was constantly kept over 0.4m/d and 0.8m/d in a short time, the stable flux at around 300mg/L of MLSS was shown at the 8 days later. Regardless of MLSS and flux, BOD, CODcr and Turbidity of the permeate were 1~2mg/L, 7~10mg/L and below 1 NTU, which were 85~90%, 87~90% and 98% of removal efficiency, respectively. The stable operation without fouling was achieved because the contents of ECP were smaller than those of common MBR processes and the composition(saccharide/protein) was kept constantly. In this study, 0.5~1.0m/d of flux and 400~900mg/L of MLSS were considered as the most recommendable operating condition for the reuse of weaving wastewater.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.2 no.1
• /
• pp.40-48
• /
• 1999

Wave absorbing system is needed at various kinds of wave basins (wave flume, towing tank, square tank) for the model test related to the ocean engineering. In this paper, the performance of wave absorbing system with new concept is estimated throughout the experiments. Herein, the wave absorbing system is designed by punching plate with a given porosity which is installed horizontally and submerged near the water surface. As the incident wave generated by a wave maker advances above a punching plate, the strong jet flow is formed near a hole of punching plate. As a result, wave energy is dissipated into heat energy, Systematic model tests were conducted at KRISO to verify the performance of the wave absorber using a punching plate. It was found that the reflection coefficient of wave absorber is deeply dependent on both the porosity and the submerged depth of a punching plate. Inclined installation of a punching plate shows better performance than a horizontal one within a certain inclined angle.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.5 no.1
• /
• pp.75-81
• /
• 1985

The behavior of a plane buoyant jet within the zone of flow establishment(ZFE) which is discharged vertically upward into a stagnant uniform environment, is analyzed by the integral equations of mass, momentum and tracer conservation. The analysis includes the spreading ratio with Froude number and geometry of the potential core of ZFE and the length of ZFE. The central velocity at the end of ZFE is found to be influenced significantly by buoyancy, especially at low discharge Froude number. The results provide the necessary initial conditions for the investigation of the zone of established flow.