• 에너지공학
• /
• 제7권2호
• /
• pp.187-193
• /
• 1998

The turbulent heat transfer to low Prandtl number fluid flow through rod bundles is analyzed using k-$\varepsilon$ two-equation model. For the prediction of the turbulent flow field, an anisotropic eddy viscosity model is used. In the analysis of the temperature field, the effects of various parameters such as geometry, Reynolds and Prandtl numbers are considered. The calculation in made for Prandtl numbers from 0.001 to 0.1 in order to analyze the heat transfer to low Prandtl number fluid such as liquid metals. The numerical results show that for small P/D (Pitch/Diameter) geometries low Prandtl number makes severe changes of the rod surface temperature.

• 제어로봇시스템학회논문지
• /
• 제16권4호
• /
• pp.368-373
• /
• 2010

A new indoor mobile robot localization method is presented. Robot recognizes well designed single color landmarks on the ceiling by vision system, as reference to compute its precise position. The proposed likelihood prediction based method enables the robot to estimate its position based only on the orientation of landmark.The use of single color landmarks helps to reduce the complexity of the landmark structure and makes it easily detectable. Edge based optical flow is further used to compensate for some landmark recognition error. This technique is applicable for navigation in an unlimited sized indoor space. Prediction scheme and localization algorithm are proposed, and edge based optical flow and data fusing are presented. Experimental results show that the proposed method provides accurate estimation of the robot position with a localization error within a range of 5 cm and directional error less than 4 degrees.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.103-108
• /
• 2010

This article presents computational fluid dynamics (CFD) simulations of nanoparticle movements and flow characteristics in laboratory-scale electrostatic precipitator (ESP) without corona discharge, and for simulation, it uses the commercial CFD program(CFD-ACE) including electrostatic theory and Lagrangian-based equation for nanoparticle movement. For validation of CFD results, a simple cylindrical type of ESP is simulated and numerical prediction shows fairly good agreement with the analytical solution. In particular, the present study investigates the effect of particle diameter, inlet flow rate, and applied electric potential on particle collection efficiency and compares the numerical prediction with the experimental data, showing good agreement. It is found that the particle collection efficiency decreases with increasing inlet flow rate because the particle detention time becomes shorter, whereas it decreases with the increase in nanoparticle diameter and with the decrease of applied electric voltage resulting from smaller terminal electrostatic velocity.

• Journal of Mechanical Science and Technology
• /
• 제15권7호
• /
• pp.889-894
• /
• 2001

In this study, the performances of various turbulence closure models are evaluated in the calculation of a transonic flow over axisymmetric bump. k-$\varepsilon$, explicit algebraic stress, and two Reynolds stress models, i.e., GL model proposed by Gibson & Launder and SSG model proposed by Speziale, Sarkar and Gatski, are chosen as turbulence closure models. SSG Reynolds stress model gives best predictions for pressure coefficients and the location of shock. The results with GL model also show quite accurate prediction of pressure coefficients down-stream of shock wave. However, in the predictions of mean velocities and turbulent stresses, the results are not so satisfactory as in the prediction of pressure coefficients.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1814-1820
• /
• 2003

Nonlinear relationship between Reynolds stresses and the rate of strain of nonlinear ${\kappa}-{\epsilon}$ models is evaluated theoretically by using the boundary layer assumptions against the turbulence-driven secondary flows in noncircular ducts and then their prediction performance is validated numerically through the application to the fully developed turbulent flow in a square duct. Typical predicted quantities such as mean axial and secondary velocities, turbulent kinetic energy and Reynolds stresses are compared with available experimental data. The nonlinear model adopted in a commercial code is found to be unable to predict accurately duct flows with the prediction level of secondary flows one order less than that of the experiment.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1980-1985
• /
• 2003

Two nonlinear ${\kappa}-{\epsilon}$ models with the wall function method are applied to the fully developed turbulent flow in a square duct. Typical predicted quantities such as axial and secondary velocities, turbulent kinetic energy and Reynolds stresses are compared in details both qualitatively and quantitatively with each other. A nonlinear ${\kappa}-{\epsilon}$ model with the wall function method capable of predicting accurately duct flows involving turbulence-driven secondary motion is presented in the present paper. The nonlinear ${\kappa}-{\epsilon}$ model adopted in a commercial code is found to be unable to predict accurately duct flows with the prediction level of secondary flows one order less than that of the experiment.

• Journal of Ship and Ocean Technology
• /
• 제4권1호
• /
• pp.1-10
• /
• 2000

A low-order potential based boundary element method is applied for the prediction of the performance of flapped rudders as well as all-movable rudders in steady inflow. In order to obtain a reasonable solution at large angles of attack, the location of the trailing wake sheet is determined by aligning freely with the local flow. The effect of the wake sheet roll-up is also included with use of a high order panel method. The flow in the gap of a flapped rudder is modeled as Couette flow and its effect is introduced into the kinematic boundary conditions for flux at both the inlet and the outlet of the gap. In order to validate the present method, the method is applied for a series of rudders and the computational results on forces and moments are compared with experimental data. The effect of the gap size on the forces and moments is also presented.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 제39회 하계학술대회
• /
• pp.842-843
• /
• 2008

Many works on the temperature prediction of power apparatus have usually done by coupled magneto-thermal analysis. However, this method can not consider the internal gas or oil flow in the power apparatus. This paper proposes a new coupled magneto-thermal-flow analysis considering Navier-Stokes equations. The convection heat transfer coefficient is calculated analytically and is applied to the boundary condition to the proposed method. Temperature distribution of 145kV 40kA three-phase GIS bus bar model is obtained by coupled magneto-thermal-flow analysis and shows good agreement with the experimental data.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.13-16
• /
• 2008

After the collapse of the Tacoma bay bridge at Tacoma Washington, the accurate prediction of aerodynamics became crucial to the sound design of bridges. CFD(Computational Fluid Dynamics) becomes important tool for the prediction on wind effects on the bridge due to the recent development of CFD. The usage of CFD is further prompted by the advantages in using CFD, such as low-cost and fast feed-back of design. In this paper, an unsteady compressible Reynolds averaged Navier-Stokes code is used for the computation of the flow over bridges. Coakley's ��q-${\omega}$ �� two-equation turbulence model is used for the turbulent eddy viscosity. For accurate and stable computations, the local preconditioning method is adapted to the code. Aerodynamic characteristics of a couple bridges are presented to show the validity and the accuracy of the method.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.168-171
• /
• 2008

In the present study, turbulent flows around cubic and L-shape buildings were simulated numerically. Standard ${\kappa}$-$\varepsilon$, RNG ${\kappa}$-$\varepsilon$, LES turbulence models were adopted for the present simulation. The wind pressure coefficients from these results were compared with the available experimental data. The result of RNG ${\kappa}$-$\varepsilon$ and LES turbulent models gave better prediction than that of standard ${\kappa}$-$\varepsilon$ turbulent model which is widely used in the turbulent flow simulation.