• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.683-692
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• 2007

Recently, plastic products in air-intake parts of automotive engines have become very popular due to advantages that include reduced weight, constricted cost, and lower intake air temperature. However, flow-induced noise in air-intake parts becomes a more serious problem for plastic intake-manifolds than for conventional aluminum-made manifolds. This is due to the fact that plastic manifolds transmit more noise owing to their lower material density. Internal aerodynamic noise from an idle speed control actuator(ISA) is qualitatively analyzed by using a scaling law, which is expressed with some flow parameters such as pressure drop, maximum flow velocity, and turbulence kinetic energy. First, basic flow characteristics through ISA passage are identified with the flow predictions obtained by applying computational fluid dynamics techniques. Then, the effects on ISA passage noise of each design factors including the duct turning shape and vane geometries are assessed. Based on these results, the preliminary low noise design for the ISA passage are proposed. The current method for the prediction of internal aerodynamic noise consists of the steady CFD and the scaling laws for the noise prediction. This combination is most cost-effective, compared with other methods, and therefore is believed to be suited for the preliminary design tool in the industrial field.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.153-160
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• 2018

In order to develop the driving pump for High-speed Cavitation Tunnel(HCT) which can experiment the super-cavitating submerged body, KRISO decided on the pump specification, designed the mixed-flow pump on the basis of the existing pump data and predicted the performance of the design pump using commercial CFD code (CFX-10). After the manufacture and installation of the driving pump, KRISO conducted the trial-test for HCT, analyzed the pump performance and compared trial-test results to those of design stage. The trial-test items for the HCT driving pump are measurements of output current/voltage at the inverter of the driving pump and the flow velocity in the HCT test section. The trial-test results showed the decrease in the flow rate of about 4.6% and the increase in pump head of about 8%, compared with those of the pump prediction. After the trial-test, the performance of the driving pump is predicted using CFX-10 with measured flowrates and pump rotational velocities. Though there is some difference between trial-test and prediction results due to inadequate motor data, it is thought that the tendency is reasonable. It is found that CFX-10 is useful to predict a mixed-flow pump.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.763-774
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• 2023

The water availability in a river is related to the return flow of residential water. However it is still difficult to determine the exact return flow. In this study, the residential water-cycle system is defined as a process consisting of water inflow, water transfer and water outflow. The study area is Hampyeong-gun, Jeollanam-do, and is set as a single inflow to a single outflow through the water-cycle system after classification of complete and incomplete measurement points. The time-series prediction models(ARIMA model and TFM) are established with daily inflow and outflow data for 6 years. Inflow and outflow are predicted by dividing into training and test periods. As a result, both models show the feasibility of short-term prediction by deriving stable residuals and securing statistical significance, implementing the preliminary form of the water-cycle system. As a further study, it is suggested to predict the actual return flow of the target basin and efficient water operation by adding input factors and selecting the optimal model.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.368-371
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• 2008

The optimal operation condition of gasifier is one of the most important parameters to increase efficiency and reliability in IGCC plant. Also the prediction of the syngas composition and quantity must be predicted to carry out process design of the gasification plant. However, the gasifier process licensor are protective with information on process design and optimal gasifier design conditions. So, the most of process studies in the engineering company for gasification plant have carried out to look for key parameters and optimal design conditions using several prediction methods. In this paper, we present the estimated preliminary optimal operation condition of the 300MW Demonstration Entrain Flow Gasifier using Aspen Plus. The gasifier operation temperature considering slag flow was predicted by FactSage software and Annen Model.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.141-153
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• 1999

Numerical analysis for the combustion flow in the combustion chamber of incineration system has been carried out in order to acquire the basic design capability of incineration system. Established mathematical model was applied to the performance prediction of the pre-designed combustion chamber of commercial plant. Especially, combustion characteristics and the variation of flow pattern have been deeply discussed in accordance with secondary air injection. Secondary air injection was effective for the turbulent mixing between air and carbon monoxide/volatile matter resulting in considerably reduced CO content at the exit. Secondary air injection was found to be one of the key design parameters because the size of recirculation zone could be changed with the variation of injection characteristics.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.220-223
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• 2004

The initial conditions such as the film thickness and the void fraction at the onset of annular flow are required for the analytical dryout model. The Disturbance Wave Instability model(DWI model) is one of the model describing the Annular-to-Intermittent Flow regime Transition(AIFT). The experimental CHF conditions for the uniformly heated tube were compared with the predictions by the modified Levy model, for which the initial conditions at AIFT were estimated by the DWI model. For the flow through long tubes with small inlet subcooling, the effect of AIFT model on the dryout prediction was little. However, the use of DWI model gave better prediction of CHF in a short tube.

• Journal of computational fluids engineering
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• v.6 no.4
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• pp.15-25
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• 2001

Numerical prediction of the diffusion controlled transition in a turbine gas pass is important because it can change the local heat transfer rate over a turbine blade as much as three times. In this study, the gas flow over turbine blade is simplified to the flat plate boundary layer, and an adaptive grid scheme redistributing grid points within the computation domain is proposed with a great emphasis on the construction of the grid control function. The function is sensitized to the second invariant of the mean strain tensor, its spatial gradient, and the interaction of pressure gradient and flow deformation. The transition process is assumed to be described with a κ-ε turbulence model. An elliptic solver is employed to integrate governing equations. Numerical results show that the proposed adaptive grid scheme is very effective in obtaining grid independent numerical solution with a very low grid number. It is expected that present scheme is helpful in predicting actual flow within a turbine to improve computation efficiency.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.275-279
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• 2005

The vortex convection and induced flow field behind the KARI 3m x 4m LSWT gust generator was computed by using Computational Fluid Dynamics. For the accurate simulation of vortex convection, inviscid, laminar, Spalart-Allmars k-e and k-w turbulence models were tested with the NAL gust generator configuration and Spalart-Allmaras turbulence model was selected for the prediction of induced flow field behind the KARI LSWT gust generator. The wind tunnel test was also carried out at KARI LSWT and the results were compared with CFD prediction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3039-3045
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• 1994

The k-$\varepsilon$ turbulence models by Launder et al.(1977, LPS) and Leschziner and Rodi(1981, LR) are modified to account for the secondary straining effect with having a generality in the present paper. The modified models are obtained by replacing the gradient Richardson number used to account for the secondary straining effect in the original models by a new parameter with a tensor-invariant correction form. These two modified models are used to predict the turbulent flow over a backward-facing step. In contrast to both standard and modified LR models, the modified LPS model is found to predict the reattachment point fairy well, as well as mean velocity, wall static pressure, turbulent kinetic energy and Reynolds shear stress in the recirculating region.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3357-3368
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• 1994

Total pressure losses required to calculate the total-to-total efficiency are estimated by integrating empirical loss coefficients of four loss mechanisms along the mean-line of blades as follows; blade profile loss, secondary flow loss, end wall loss and tip clearance loss. The off-design points are obtained on the basis of Howell's off-design performance of a compressor cascade. Also, inlet-outlet air angles and camber angle are obtained from semi-empirical relations of transonic airfoils' minimum loss incidence and deviation angles. And nominal point is replaced by the design point. It is concluded that relatively simple loss models and Howell's off-design data permit us to calculate the off-design performance with satisfactory accuracy. And this method can be easily extended for off-design performance prediction of multi-stage compressors.