• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.233-237
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• 2011

In the present experiments, vortical structures behind the hydrofoil trailing edge are visualized and analyzed as an elementary study for propeller singing phenomena. Two sorts of hydrofoil are selected for the measurement of shedding vortices. One was KH45 hydrofoil section and the other is KH45 with the truncated trailing edge that is positioned at X/C = 0.9523(C=chord length). Assuming the Strouhal number of 0.23, the shedding frequencies of vortices are extracted by analyzing the boundary layer thickness and the flow speed. The frequency distribution of shedding vortices is obtained with the variation of angle-of-attack while the flow speed is fixed to 8m/s. The truncation of the trailing edge makes the frequency of shedding vortices about 120Hz lower than that of original trailing edge and makes the vorticity value higher than the original trailing edge.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.159.1-159.1
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• 2011

Due to the global warming, the need to secure the alternative resources has become more important worldwide. Having very strong current on the west coast with up to 10 m tidal range, there are many suitable sites for the application of TCP(Tidal current power) in Korea. Not only from the current produced from the high tidal range, but also it can be widely applied to the offshore jetties and piers. The VAT(Vertical axis turbine) system could be very effective tidal device to extract the energies from the attacking flow to the structures. For the relatively slow current speed, the VAT system could be more effective application than HAT(Horizontal axis turbine) device. The performance of VAT can be evaluated by various parameters including number of blades, shape, sectional size, diameters and etc. The paper introduces the multi-layer vertical axis tidal current power system with savonius turbine. The turbine was designed with consideration of optimal blade numbers and the performance was simulated by CFD analysis.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.24 no.4
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• pp.19-25
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• 1979

Lowland and upland rice were grown under the both of lowland and upland conditions. Ecological variations in plant characteristics such as plant height, leaf emergence, length of leaf blade, leaf angle, leaf width, heading date, culm length, panicle length and straw weight were observed. Plant height, leaf emergence and heading were accelerated under the lowland condition for both lowland and upland varieties, while leaf length, leaf angle, leaf breadth, number of leaves were increased in upland condition for both lowland and upland varieties.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.267-274
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• 2004

The optimum condition is defined as one that best suits the purpose of flocculation; the number of small particles should decrease, while that of large particles should increase. The object of this research was to develop a new impeller and substitute for conventional flocculators. The flow characteristics of turbines and hydrofoil type flocculators in turbulent fluids were observed using a standard k-$\epsilon$ Model and a computational fluid dynamics (CFD) simulation program- FLUENT The experiments were performed to compare PBT(Pitched Blade Turbine) flocculator with twisted hydrofoil type flocculators for velocity distribution, and floc formation at conventional water treatment plants in Korea. As a result of the CFD solution, twisted hydrofoil types are similar to hydrofoil flocculators for flow characteristics without regard to the twisted angle, On the other hand, it was established that turbine flocculators are greater than hydrofoil flocculators with flow unevenness and dead zone formation. Twisted hydrofoil type- II (Angle $15{\~}20^{\circ}$) is the most proper impeller for water flocculation from this point of view with a decreasing the dead zone, maintaining of the equivalent energy distribution and a drawing up of the sedimentation substance from the bottom of the flocculation basin.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1309-1314
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• 2008

I.G.G is abbreviation for Inert Gas Generator, High temperature in Cargo Tank it desulfurize, exhausted and froze the gas that combined brimstone element and soot, then supply Inert gas by blower, and mack tank inside incombustible range this is equipment that nip in the bud the explosion. The blower for suppling inactivated gas has big impeller with heavy weight to achieve the high pressure, it causes a delay for first operation time and too much load is delivered to motor, total destruction by fire of motor is happening frequently. On this research, we will reduce the size & weight of impeller and install it with several stage, it makes an effect for reducing the first operation time. We also intend to contribute to efficient IGG blower design by research a flowing & pressure specialty from the diameter of impeller, number of blade, and size of casing.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.155-161
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• 1999

The three-dimensional turbulent cascade flows with and without endwall fences are numerically investigated by solving the incompressible Navier-Stokes equations with a high-Reynolds number $k-{\varepsilon}$ turbulence closure model. A projection method based algorithm is used in the finite-volume formulation, with the second order upwind-differencing scheme for the convective terms. First, assessments on accuracy of the present method are made by comparing the static pressure distributions at the mid-span of the cascade with measured data, and also by confirming the experimental observations on the choice of an optimal fence height for the secondary flow control. In understanding the three-dimensional nature of the secondary flow in turbine cascade, the limiting streamline patterns and the static pressure contours at the suction surface of the blade as well as on the cascade endwall are employed to visualize the effectiveness of the endwall fence for the secondary flow control. Analysis on the streamwise vorticity contour maps along the cascade with the three-dimensional representation of their iso-surfaces reveals the strucuture of the complicated vortical flow in the turbine cascade with endwall fence, and also leads to an understanding on formation of the counter-rotating streamwise vortex over the endwall fence, in explaining the mechanisms of controlling the secondary flow and also for the proper selection of an optimal fence height.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1975-1980
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• 2004

The three-dimensional flow in a turbine nozzle guide vane passage causes large secondary loss through the passage and increased heat transfer on the blade surface. In order to reduce or control these secondary flows, a linear cascade with a contoured endwall configuration was used and changes in the three-dimensional flow field were analyzed and discussed. Measurements of secondary flow velocity and total pressure loss within the passage have been performed by means of five-hole probes. The investigation was carried out at fixed exit Reynolds number of $4.0{\times}10^5$. The objective of this study is to document the development of the three-dimensional flow in a turbine nozzle guide vane cascade with modified endwall. The results show that the development of passage vortex and cross flow in the cascade composed of one flat and one contoured endwalls are affected by the flow acceleration which occurs in contoured endwall side. The overall loss is reduced near the flat endwall rather than contoured endwall.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1195-1207
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• 1998

Periodic pulsations in the static pressure near turbine surfaces as blade rows move relative to each other is one of the important sources of turbine unsteadiness. The present experiment aims to investigate the effect of the static pressure pulsations on the interaction of film coolant flows from two rows of staggered holes with mainstream and its effect on film cooling heat transfer. Potential flow pulsations are generated by the rotating shutter mechanism installed downstream of the test section, The free-stream Strouhal number based on the boundary layer thickness is in the range of 0.033 - 0.33, and the amplitude of about 10-20%. Measured are time-averaged and phase-averaged velocity variations, pressure variations and temperature distributions of the flow field. Experimental conditions are identified by boundary layer measurements. Injectant behavior is characterized by the measurements of unsteady pressure in the plenum chamber and free-stream static pressure. The film cooling effectiveness is evaluated from the insulated wall temperature measurement. It has been found that bulk flow pulsation provides very large diffusion of the injectants and the effectiveness is significantly reduced by the flow pulsations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.3
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• pp.241-255
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• 2012

Three types of 100 kW-class tidal stream turbines are proposed and their performance is studied both numerically and experimentally. Following a wind turbine design procedure, a base blade is derived and two additional blades are newly designed focusing more on efficiency and cavitation. For the three designed turbines, a CFD is performed by using FLUENT. The calculations predict that the newly designed turbines perform better than the base turbine and the tip vortex can be reduced with additional efficiency increase by adopting a tip rake. The performance of the turbines is tested in a towing tank with 700 mm models. The scale problem is carefully investigated and the measurements are compared with the CFD results. All the prediction from the CFD is supported by the model experiment with some quantitative discrepancy. The maximum efficiencies are 0.49 (CFD) and 0.45 (experiment) at TSR 5.17 for the turbine with a tip rake.

• International Journal of Naval Architecture and Ocean Engineering
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• v.1 no.2
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• pp.64-69
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• 2009

The two-dimensional unsteady flow around a vertical axis turbine for tidal stream energy conversion was investigated using a computational fluid dynamics tool solving the Reynolds-Averaged Navier-Stokes equations. The geometry of the turbine blade section was NACA653-018 aiifoil. The computational analysis was done at several different angles of attack and the results were compared with the corresponding experimental data for validation and calibration. Simulations were then carried out for the two-dimensional cross section of a vertical axis turbine. The simulation results demonstrated the usefulness of the method for the typical unsteady flows around vertical axis turbines. The optimum turbine efficiency was achieved for carefully selected combinations of the number of blades and tip speed ratios.