• 대한기계학회논문집B
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• 제23권6호
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• pp.753-760
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• 1999

Experiments were conducted to investigate the effect of the initial turbulent intensity on the flow and heat transfer characteristics for a two-dimensional impinging jet. A square rod was installed at the nozzle exit to increase initial turbulent intensity. A hot wire probe and thermochromic liquid crystal technique were used to measure the turbulent intensity and the surface temperature. All measurements were made over a range of nozzle-to-plate distance from 1 to 10 at Re=20,000. When the rod is not installed, the maximum stagnation point Nusselt number is occurred at H/B=9. A higher initial turbulent intensity enhanced the heat transfer on the surface. A correlation between stagnation point Nusselt number and turbulent intensity are presented.

• 한국연소학회지
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• 제9권1호
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• pp.32-38
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• 2004

Characteristics of turbulent lifted flames in coflow jet have been investigated by varying initial temperature through the heating coflow air. In the turbulent regime, liftoff height increases linearly with fuel jet velocity and decreases nonlinearly as the coflow temperature increases. This can be attributed to the increase of turbulent propagation speed, which is strongly related to laminar burning velocity. Dimensionless liftoff heights are correlated well with dimensionless jet velocity, which are scaled with parameters determining local flow velocity and turbulent propagation speed. This implies that the turbulent lifted flames are stabilized by balance mechanism between local turbulent burning velocity and flow velocity. Blowout velocity can be obtained from the ratio of mixing time to chemical time. Comparing to previous researches, thermal diffusivity should be evaluated from the initial temperature instead of adiabatic flame temperature.

• 한국공간구조학회논문집
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• 제2권4호
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• pp.61-76
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• 2002

The structure system that is discreterized by continuous shells is usually used to make a large space structures and these structures show the collapse mechanisms that are captured at over the limit load, and snap-through and bifurcation are most well known of it. For the collapse mechanism, rise-span ratio, element stiffness and load mode are main factor, which it give an effect to unstable behavior. Moreover, resist force of structure can be reduced by initial condition and initial imperfection significantly. In order to investigate the instability of shell structures, the finite deformation theory can be applied and it becomes a nonlinear mathematics in which use equation of tangential stiffness incrementally. With an initial imperfection, using simple example and Flow Truss Dome, the buckling characteristics of space truss is main purpose of this paper, and unstable behavior is studied by proposed the numerical method. Also, by using MIDAS, this research work analyzes displacements and inner forces as the design load of model, and the ratio of buckling load of design load is investigated.

• 환경위생공학
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• 제15권2호
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• pp.58-64
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• 2000

The photocatalytic removal of Ag(I) in water by $TiO_2$ at a various conditions, which are initial Ag(I) concentration, circulation flow rate, $TiO_2$ dosage and methanol concentration, was studied. A continuous flow system with a circular type reactor of the TiO2 suspensions with UV light through an photoreactor column was applied. The major results of this study were as follows; 1. First order kinetics was observed from the result at different initial concentration of Ag(I). As the initial Ag(I) concentration was incereased, the reaction rate was decreased. 2. The removal efficiency of Ag(I) increased with increasing the circulation flow rate and $TiO_2$ dosage. However, over $4{\ell}/min$ of circulation flow rate and $1.5g/{\ell}$ of $TiO_2$ dosage, increasing of the efficiency reached a plateau. 3. The addition of methanol as hole scavenger enhanced the removal efficiency of Ag(I) but the removal efficiency reached a plateau over some level of methanol. 4. It was found that $TiO_2$ photocatalysis was effective method to remove of Ag(I) from aqueous solution.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1053-1060
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• 2006

This paper consider an initially deformed state caused by the pressurized fluid flowing through the pipe at a constant velocity. When the initial forte is neglected in curved pipes, the natural frequencies are reduced as flow velocity increases. However, when the initial tension took into account, the natural frequencies are not changed with the change of the flow velocity. As the internal pipe pressure is increased the natural frequencies are also slightly increased. In free vibrational simulation of piping systems in petrochemical plants, it is necessary to calculate the initial state force due to the velocity and the pressure of the fluid flow from the equilibrium first, then the force should be included in the equation of motion of the systems to get more accurate natural frequencies. In this study, calculate the mass matrix and stiffness matrix of piping system by MATLAB

• Journal of Mechanical Science and Technology
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• 제15권8호
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• pp.1165-1173
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• 2001

This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural gas pipelines. The dynamic behaviour of PIG depends on the pressure differential generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze dynamic behaviour characteristics (e.g. gas flow, the PIG position and velocity) mathematical models are derived. Tow types of nonlinear hyperbolic partial differential equations are developed for unsteady flow analysis of the PIG driving and expelled gas. Also, a non-homogeneous differential equation for dynamic analysis of the PIG is given. The nonlinear equations are solved by method of characteristics (MOC) with a regular rectangular grid under appropriate initial and boundary conditions. Runge-Kutta method is used for solving the steady flow equations to get the initial flow values and for solving the dynamic equation of the PIG. The upstream and downstream regions are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. Simulation is performed with a pipeline segment in the Korea gas corporation (KOGAS) low pressure system. Ueijungboo-Sangye line. The simulation results show that the derived mathematical models and the proposed computational scheme are effective for estimating the position and velocity of the PIG with a given operational condition of pipeline.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.448-448
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• 2000

This paper deals with dynamic behaviour analysis for pipeline inspection gauge (PIG) flow control in natural gas pipeline. The dynamic behaviour of the PIG is depending on the different Pressure between the rear and nose parts, which is generated by injected gas flow behind PIG's tail and expelled gas flow in front of its nose. To analyze the dynamic behaviour characteristics such as gas flow in pipeline, and the PIG's position and velocity, mathematical model is derived as two types of a nonlinear hyperbolic partial differential equation for unsteady flow analysis of the PIG driving and expelled gas, and nonhomogeneous differential equation for dynamic analysis of PIG. The nonlinear equation is solved by method of characteristics (MOC) with the regular rectangular grid under appropriate initial and boundary conditions. The Runge-Kuta method is used when we solve the steady flow equations to get initial flow values and the dynamic equation of PIG. The gas upstream and downstream of PIG are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. The simulation is performed with a pipeline segment in the Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. The simulation results show us that the derived mathematical model and the proposed computational scheme are effective for estimating the position and velocity of PIG with different operational conditions of pipeline.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.181-188
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• 2004

A cylindrical constant-volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of an inhomogeneous charge methane-air mixture under several parameters such as stratified pattern, initial charge pressure, ignition time and the excess air ratio of the initial charge mixture. Flow characteristics including mean velocity and turbulence intensity were analyzed by a hot-wire anemometer. The combustion pressure development, measured by a piezo-electric pressure transducer, was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to near-zero value at 3000 ms. For the stratified patterns, the combustion rate under the rich injection (RI) condition was the fastest. Under the initial charge conditions, the second mixture was accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the combustion rate.

• 한국농공학회논문집
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• 제50권6호
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• pp.3-12
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• 2008

It is important to estimate accurate effective rainfall to analyse flood flow and long-term runoff for the rational planning, design, and management of water resource. The initial abstraction is also important to estimate effective rainfall. The Soil Conservation Service (SCS) has developed a procedure and it has been most commonly applied to estimate effective rainfall. But the SCS method still has weak points, because of unnatural assumptions such as antecedent moisture conditions and initial abstraction. The coefficient of initial abstraction(K) is depending on the soil moisture condition and antecedent rainfall. The maximum storage capacity of Umax which is calibrated by stream flow data in the proposed watershed was derived from the DAWAST(DAily WAtershed STreamflow) model. The values of K obtained from 69 storm events at the five watersheds are ranging from 0.133 to 0.365 and its mean value is 0.207. Effective rainfall could be estimated more reasonably by introducing new concept of initial abstraction. The equation of $K=0.076Sa^{0.255}$ was recommended instead of 0.2 and it could be applicable to the small-medium rural watersheds.

• 한국물환경학회지
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• 제26권2호
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• pp.303-310
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• 2010

Recently distinguished AOP means technology resolving organic compounds in water to harmless compounds such as $CO_2$ and $H_2O$ by creating OH radical ($OH{\cdot}$) with more powerful oxidation than general oxidants. It has merits which the 2nd pollution is not caused since it uses solar energy, sludge doesn't take place, it can be applied to high-density waste water and it oxidizes non-biodegradable organic compounds more easily. The purpose of the study was to examine about removable characteristics of phenol which was a non-biodegradable organic matter with UV/$O_3$/Catalyst processes which is one out of AOP and to present applicability of photocatalyst and the optimum conditions of treatment. The study regarded initial phenol concentration, initial pH, photocatalyst amount and flow as its conditions. As the results, the test had the highest removable efficiency (92%) when initial phenol concentration was 100 mg/L, initial pH 7, photocatalyst amount 6L and flow 1.5 mg/min. The removable efficiency was increased as much as initial phenol concentration was increased, when initial pH was 7 (neutrality), photocatalyst amount was increased and flow was increased. It was checked that the optimum HRT was 12 hours. Therefore, phenol is enough removable with UV/$O_3$/Catalyst process and its prospect in the future is expected.