• Wind and Structures
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• v.24 no.1
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• pp.79-93
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• 2017

Wind-induced fluctuating internal pressures in a building with a dominant opening can be described by a second-order non-linear differential equation. However, the accuracy and efficiency of the governing equation in predicting internal pressure fluctuations depend upon two ill-defined parameters: inertial coefficient $C_I$ and loss coefficient $C_L$, since $C_I$ determines the un-damped oscillation frequency of an air slug at the opening, while $C_L$ controls the decay ratio of the fluctuating internal pressure. This study particularly focused on the value of loss coefficient and its influence factors including: opening configuration and location, internal volumes, as well as wind speed and approaching flow turbulence. A simplified formula was presented to predict loss coefficient, therefore an approximate relationship between the standard deviation of internal and external pressures can be estimated using Vickery's approach. The study shows that the loss coefficient governs the peak response of the internal pressure spectrum which, in turn, will directly influence the standard deviation of the fluctuating internal pressure. The approaching flow characteristic and opening location have a remarkable effect on the parameter $C_L$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.615-622
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• 2000

Numerical simulation is performed with Denton's code to get pressure loss coefficients in wide range of reverse flow incidence(from -90 degree to +85 degree) for an axial compressor cascade. As a results, it is found that the pressure loss coefficient is increased with incidence and there exist critical incidence which corresponds to the maximum pressure loss coefficient. Pressure loss coefficient with bigger incidence than its critical value is decreased. The effect of increasing incidence in a cascade extremely reduce the mass flow rate by the large flow separation region. Consequently this effect reduce the portion of dynamic pressure in the total pressure loss and beyond the critical incidence the pressure loss coefficient decrease.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1603-1612
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• 1996

The pressure loss coefficient of Newtonian and non-Newtonian fluids such as water, aqueous solutions of Carbopol-934 and Separan AP-273 and blood in the stenotic tubes are determined experimentally and numerically. The numerical analyses for flows of non-Newtonian fluids in the stenotic tubes are conducted by the finite element method. The effect of the contraction ratio and the ratio of length to diameter on the pressure drop are investigated by the experiments and numerical analysis. The pressure loss coefficients are significantly dependent upon the Reynolds number in the laminar flow regime. As Reynolds number increases, the pressure loss coefficients of both Newtonian and non-Newtonian fluids decrease in the laminar flow regime. As the ratio of length to diameter increases the maximum pressure loss coefficient increases in the laminar flow regime for both Newtonian and non-Newtonian fluids. Newtonian fuid shows the highest values of pressure loss coefficient and blood the next, followed by Carbopol solution and Separan solution in order. Experimental results are used to verify the numerical analyses for flows of Newtonian and non-Newtonian fluids. Numerical results for the maximum pressure loss coefficient in the stenotic tubes are in fairly good agreement with the experimental results. The relative differences between the numerical and experimental results of the pressure loss coefficients in the laminar flow regime range from 0.5% to 14.8%.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.126-133
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• 2007

An experimental apparatus has been designed and prepared in order to measure a pressure loss coefficient of hydropneumatic components, which is an important parameter in a hydropneumatic system Blow-down system has been adopted for the experimental apparatu to meet the high flow energy requirement as well as the apparatus safety. Especially, pressure loss coefficient measurements of pyrostarter filters have been performed and the pressure loss coefficient, K of CQSF has been experimentally acquired. Then it is shown that the turbine inlet pressure $p_2$, which is predicted from the measured K, is in accord with the results of combustion tests. Moreover, the relation between K and combustion pressure $p_0$ has been presented and it is disclosed that the relation accords well with the results of combustion tests. It is anticipated that K of a filter could play a role in PS size reduction by rising up the combustion pressure resulting in increasing the burning rate of solid propellant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.797-805
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• 2014

The purpose of this study was to investigate the drag and lift characteristics of the cavitator of a supercavitating underwater vehicle and the pressure loss due to water intake. These investigations were performed by changing the diameter, velocity, radius of curvature of the intake, and angle of attack of the cavitator. With increasing ratio of the intake diameter to the cavitator diameter ratio($d/D_1$), the drag coefficient and the pressure loss coefficient of the water intake decreased. The greater the increase in the ratio of the intake velocity-to-free stream velocity ratio(S), the smaller was the decrease in the drag coefficient and the lift coefficient. When the intake had a radius of curvature(c), the pressure loss coefficient decreased. On the contrary, the effect of the radius of curvature on the drag coefficient was imperceptible. For angles of attack (${\alpha}$) of the caviatator in the range of $0^{\circ}$ to $10^{\circ}$, the drag coefficient and the pressure loss coefficient changed slightly, whereas the lift coefficient increased linearly with increasing angle of attack.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.779-786
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• 2019

Effects of chamfered perforated plate on pressure loss characteristics were studied with CFD analysis. Both inlet chamfer angle and outlet chamfer angle were considered. Perforated patterns were compared by pressure loss coefficient in certain porosity and Reynolds number. Reynolds number effects were studied for several chamfer angles and plate thickness. As the inlet chamfer angle was increased, the pressure loss coefficient was decreased until the certain angle and reversed to increase. In the outlet chamfered shape cases, the pressure loss coefficient was increased with chamfer angle. Effects of pattern shapes and Reynolds number on pressure loss characteristics were negligible with different chamfer angles and thickness studied in this paper.

• Journal of Hydrogen and New Energy
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• v.19 no.5
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• pp.367-376
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• 2008

To obtain the data of the pressure loss and differential pressure at the inside of the stack that was composed of 126 cells with 7,500 cm2 electrode area, 75kW molten carbonate fuel cell system has been operated. Computational fluid dynamics was applied to estimate reactions and thermal fluid behavior inside of the stack that was adopted with internal manifold type separator. The pressure loss coefficient K showed 72.29 to 84.01 in anode and 6.34 to 8.75 in cathode at low part of cells at the inside of 75 kW MCFC stack respectively. Meanwhile, the pressure loss coefficient of the higher part of cells at the interior of the stack showed 15.36 and 56.44 in anode and cathode respectively. These results mean that there is no big total pressure difference between anode and cathode at the inner part of 75 kW MCFC stack. This result will be reflected in 250kW MCFC system design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5696-5703
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• 2012

In this study, the characteristics of filter that make up the automotive airbag system were analyzed. The gas pressure change of airbag is directly impacted by the filter. However, it is uncertain how much the design factors of filter affect the pressure of airbag. And it is difficult to access the pressure loss coefficient in the respect of characteristics of the airbag filter in the simulation method. To solve this problem, this study suggests pressure loss coefficient of the filter using simulation analysis. But it is impossible to interpret a sudden increase of pressure such as airbag filter. To solve this problem, by applying interpolation and scale down method, analysis was processed. Also, through the simulation interpretation of airbag filter's pressure loss coefficient, the guidelines for the filter design could be suggested.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.258-264
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• 2010

Most of fluid systems, such as P&ID in ships, power plants, and chemical plants, consist of various components. The components such as bends, tees, sudden-expansions, sudden-contractions, and orifices contribute to overall pressure loss of the system. The local pressure losses across such components are determined using a pressure loss coefficient, k-factor, in lumped parameter models. In many engineering problems Idelchik's k-factor models have been used to estimate them. The present work compares the k-factor based on CFD calculation against Idelchik's model in order to confirm whether a commercial CFD package can be used for pressure loss coefficient estimation of complex geometries. The results show that RSM is the best appropriate for evaluating pressure loss coefficient. Commercial CFD package can be used as a tool evaluating k-factor even though the accuracy is influenced by a turbulence model.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.157-163
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• 1992

In this paper, the relationship between static pressure recovery and turbulent energy was presented in case of swirling flows into a conical diffuser. The distributions of turbulent energy in a diffuser sectional area were measured by a hot wire anemometer. The following conclusion can be drawn from the experiment. Diffuser loss is constituted by a dynamic pressure loss and total pressure loss. The static pressure recovery depends strongly on the total pressure loss. The static pressure recovery depends strongly on the total pressure loss, and the turbulent energy varies inversely as the static pressure recovery coefficient.