• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.103-111
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• 2006

To optimize the ventilation and smoke control systems in subway equipped with platform screen door, the technology to analyze the unsteady tunnel flow caused by running of train should be developed. The development of model experiment and numerical analysis technique with relation to unsteady flow of subway were presented. The pressure and air velocity changes in 1/20-scaling experiment unit were measured and results were comparied to those of 3-D unsteady numerical analysis applied with sharp interface method. The experimental and numerical results were quantitatively similar and it would be reasonable to apply sharp interface method to analyze the unsteady flow in subway equipped with platform screen door.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.92-100
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• 2008

The main objective of this study was to clarify the origin of the unsteady flows arising in a mixed-flow vaneless diffuser system and also the effects of physical components of the system. The testing equipment consists of a straight tube, a swirl generator, and a mixed-flow vaneless diffuser. Pressure fluctuations of the flow through the tube and diffuser were measured by using a semiconductor-type pressure transducer and analyzed by an FFT analyzer. In the experiment, the velocity ratio (axial velocity/peripheral velocity) of the internal flow, and the geometric parameters of the diffuser were varied. Two kinds of unsteady flows were measured according to the combination of the components, and the origin of each unsteady flow was clarified. The fundamental frequencies of unsteady flows arose were examined by two-dimensional small perturbation analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.8 no.1
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• pp.101-108
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• 2002

This experimental study was performed to investigate internal flow and unsteady flow characteristics using a model for actual shape of a Plate heat exchanger and visualization of flow through the particle image velocimetry. Seven Reynolds numbers were selected by calculation with the height of grooved channel and sectional mean velocity of inlet flow in the experiment, and instantaneous velocity distributions and flow characteristics were experimently investigated. The triangular grooved channel had a compound flow consisting of the flow in lower channel and the groove flow receiving shear stress by the channel flow in the experiment. The sheared mixing layer, in the boundary between the triangular groove and the channel. affected main flow to raise turbulent in the channel.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1395-1399
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• 2006

The current paper focuses the analysis of leakage detection in water pipeline systems by means of the transient analysis. In order to obtain pressure variation for evaluation the existing methodology, an extensive experimental process has been carried out in a single pipeline system. Several experimental tests were performed with and without a leakage in the system. Using the unsteady friction and improved unsteady friction factors, reasonable match between the computed and measured pressure were presented on the condition of the flow situations. The transient method attempts to estimate the leakage in water pipelines using observed pressure data collected during transient events on the system.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.207-214
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• 2006

The current paper focuses the analysis of leakage detection in water pipeline systems by means of the transient method. In order to obtain essential data for evaluation the existing methodology, an extensive experimental process has been carried out in a single pipeline system, Several experimental tests were performed with and without a leakage in the system. Using the unsteady friction and improved unsteady friction factors gives reasonable match between the computed and measured results on the condition of the flow situations presented in the paper. The transient method attempts to estimate the leakage in water pipelines using observed pressure data collected during transient events on the system.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.1061-1064
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• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.713-716
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• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.393-396
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• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.36-41
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• 1998

The cross-flow fan performance and its sound noise characteristics are predicted by computational methods. The unsteady incompressible Navier-Stokes equations in moving coordinates are solved by a SMAC method on unstructured triangular meshes, using a sliding mesh technique at the interface between the domain rotating with blades and the rest stationary part. The computationally predicted fan performance was favorably compared with experiment, and some numerical aspects of simulating the cross-flow fan are discussed. With the computed unsteady flow field, aeroacoustic sound noise of the fan is predicted by the Lighthill-Curie equation. The unsteady surface pressure fluctuations on stabilizer enables a prediction of BPF noise of the uniform pitch blade fan quite accurately. The aeroacoustic sound noise characteristics of both uniform and random pitch blade fans are also examined by SPL spectrum analysis.

• Journal of Korea Water Resources Association
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• v.45 no.5
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• pp.495-503
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• 2012

It is necessary to perform the precise analysis of unsteady flow for effective design of the side-weir detention basin installed in the river. Generally, the HEC-RAS program, which is a 1D unsteady numerical model, is mostly used to simulate the unsteady flow for rivers. However, it is difficult to have confidence of unsteady flow results simulated by HEC-RAS due to the lack of experimental data and field monitoring data for the channel with a side-weir detention basin. Therefore, the purpose of this study is to validate or verify the simulation results calculated by HEC-RAS through the experiments for the open channel with a side-weir detention basin using specially-designed unsteady discharge-supply system. The experimental cases included unsteady flows in the straight channel with and without a side-weir detention basin. Especially, for the case with a detention basin, the experiment was performed to consider only the free flow condition over the side-weir. The study results showed that values of water level and discharge obtained from HEC-RAS coincided reasonably with experimental results with the maximum error of 3% for water level and 1% for discharge in the case of the flow without the side-weir detention basin and 4% for water level and 2% for discharge with the side-weir detention basin.