• Title/Summary/Keyword: fluid flow velocity

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Thermal-flow Analysis of the Cooling System in the Medicated Water Electrolysis Apparatus (냉이온수기 냉각시스템에 관한 열유동 해석)

  • Jeon, Seong-Oh;Lee, Sang-Jun;Lee, Jong-Chul;Kim, Youn-Jea
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.3
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    • pp.33-38
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    • 2011
  • Medicated water electrolysis apparatus, which electrolyzes water into acidic water and alkaline water, was in the spotlight as becoming known the effect of alkaline water. It is known as good for health as removing active oxygen in the human's body and promoting digestion. But, the customers could not get that desired water temperature because these apparatuses are directly connected with a water pipe. So, the cooling system was developed for controlling the temperature of the alkaline water. One of the typical way is to store water in water tank and control the temperature. But, in this way, storing water can be polluted impurities coming from outside. For protecting this pollution, the cooling system based on indirect heat exchange method through phase change between water and ice was developed. In this study, we have calculated efficiency of the cooling system with phase change by experiment and commercial CFD(Computational Fluid Dynamics) code, ANSYS CFX. To consider the effect of latent heat that is generated by melting ice, we have simulated two phase numerical analyses used enthalpy method and found the temperature, velocity, and ice mass distribution for calculating the efficiency of cooling. From the results of numerical analysis, we have obtained the relationship between the cooling efficiency and each design factor.

CFD Study for Wave Run-up Characteristics Around a Truncated Cylinder with Damper

  • Zhenhao Song;Bo Woo Nam
    • Journal of Ocean Engineering and Technology
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    • v.37 no.6
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    • pp.225-237
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    • 2023
  • In this study, numerical simulations for a single fixed truncated circular cylinder in regular waves were conducted to investigate the nonlinear wave run-up under various dampers and wave period conditions. The present study used the volume of fluid (VOF) technique to capture the air-water interface. The unsteady Reynolds-averaged Navier-Stokes (URANS) equation with the k- 𝜖 turbulence model was solved using the commercial computational fluid dynamics (CFD) software STAR-CCM+. First, a systematic spatial convergence study was conducted to assess the performance and precision of the present numerical wave tank. The numerical scheme was validated by comparing the numerical results of wave run-up on a bare truncated cylinder with the experimental results, and a good agreement was achieved. Then, a series of parametric studies were carried out to examine the wave run-up time series around the truncated cylinder with single and dual dampers in terms of the first- and second-order harmonic and mean set-up components. Additionally, the local wave field and the flow velocity vectors adjacent to the cylinder were evaluated. It was confirmed that under short wave conditions, the high position of the damper led to a noticeable increase in the wave run-ups with significant changes in the first- and second-order harmonic components.

Oil Leak Analysis using Simulation Model of Hydraulic System for Dental Chair (치과용 유니트체어 유압구동 시스템 해석모델을 활용한 누유량 분석)

  • Dae Kyung Noh;Dong Won Lee;Jae Yong Kim;Joo Sup Jang
    • Journal of Drive and Control
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    • v.20 no.4
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    • pp.35-44
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    • 2023
  • This study aimed to analyze the performance of hydraulic systems for dental chair when long working hours makes the temperature of hydraulic fluid rise. The study was carried out in the following manner. First, 'cylinder's clearance' was reflected in the three kinds of hydraulic circuits, which were developed through the preceding study, in order to analyze oil leak. Second, 12 cases of simulations comprised of the up and down of cylinders were carried out. Third, it was determined whether the cylinder velocity of dental chair surpasses 1cm/s required in the development even in the hydraulic fluid temperature of 60℃. In conclusion, this study used SimulationX to verify the performance stability at high temperatures using three types of hydraulic circuits designed to develop a Korean unit chair.

Computational Fluid Dynamics(CFD) Simulation for a Pilot-scale Selective Non-catalytic Reduction(SNCR) Process Using Urea Solution (요소용액을 이용한 파일럿규모 SNCR 공정에 대한 CFD 모델링 및 모사)

  • Nguyen, Thanh D.B.;Kang, Tae-Ho;Lim, Young-Il;Kim, Seong-Joon;Eom, Won-Hyeon;Yoo, Kyung-Seun
    • Korean Chemical Engineering Research
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    • v.46 no.5
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    • pp.922-930
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    • 2008
  • The selective non-catalytic reduction(SNCR) performance is sensitive to the process parameters such as flow velocity, reaction temperature and mixing of reagent(ammonia or urea) with the flue gases. Therefore, the knowledge of the velocity field, temperature field and species concentration distribution is crucial for the design and operation of an effective SNCR injection system. In this work, a full-scale two-dimensional computational fluid dynamics(CFD)-based reacting model involving a droplet model is built and validated with the data obtained from a pilot-scale urea-based SNCR reactor installed with a 150 kW LPG burner. The kinetic mechanism with seven reactions for nitrogen oxides($NO_x$) reduction by urea-water solution is used to predict $NO_x$ reduction and ammonia slip. Using the turbulent reacting flow CFD model involving the discrete droplet phase, the CFD simulation results show maximum 20% difference from the experimental data for NO reduction. For $NH_3$ slip, the simulation results have a similar tendency with the experimental data with regard to the temperature and the normalized stoichiometric ratio(NSR).

Flow-Turbine Interaction CFD Analysis for Performance Evaluation of Vertical Axis Tidal Current Turbines (I) (수직축 조류 터빈 발전효율 평가를 위한 유동-터빈 연동 CFD 해석 (I))

  • Yi, Jin-Hak;Oh, Sang-Ho;Park, Jin-Soon;Lee, Kwang-Soo;Lee, Sang-Yeol
    • Journal of Ocean Engineering and Technology
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    • v.27 no.3
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    • pp.67-72
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    • 2013
  • In this study, numerical analyses that considered the dynamic interaction effects between the flow and a turbine were carried out to investigate the power output performance of an H-type Darrieus turbine rotor, which is one of the representative lifting-type vertical-axis tidal-current turbines. For this purpose, a commercial CFD code, Star-CCM+, was utilized for an example three-bladed turbine with a rotor diameter of 3.5 m, a solidity of 0.13, and the blade shape of an NACA0020 airfoil, and the optimal tip speed ratio (TSR) and corresponding maximum power coefficient were evaluated through exhaustive simulations with different sets of flow speed and external torque conditions. The optimal TSR and maximum power coefficient were found to be approximately 1.84 and 48%, respectively. The torque and angular velocity pulsations were also investigated, and it was found that the pulsation ratios for the torque and angular velocity were gradually increased and decreased with an increase in TSR, respectively.

The Visualization of the Flowfield around Three Circular Cylinders in the Tandem Arrangement by the PIV (PIV에 의한 직렬배열 상태에 놓인 3원주 주위의 유동장 가시화)

  • Ro, Ki-Deok;Jang, Dong-Hyu;Bae, Hung-Sub;Kim, Won-Cheol
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.2
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    • pp.264-270
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    • 2011
  • The Characteristics of the flowfield around three circular cylinders in tandem arrangement was investigated by PIV. Strouhal numbers, vorticity, velocity vectors and velocity profiles were observed at centre-to-centre space ratios of P/D=1.25~3.75, and Reynolds number of Re=$3.0{\times}10^3{\sim}5.0{\times}10^3$. As the results the Strouhal numbers measured in the rear region of 3rd the cylinder were distinguished three kind of regions with the space ratios and The flow pattern in the wake of each cylinder was different according to these regions. The time averaged flow at region of each cylinder was almost stagnated and the size of the stagnated region was small in order of 1st, 2nd and 3rd cylinder. The direction of vortex at the front and rear region of 2nd cylinder was opposed each other with the small difference(${\alpha}= {\pm}5^{\circ}$) of the attack angle ${\alpha}$.

A Numerical Study on the Effect of Mountainous Terrain and Turbine Arrangement on the Performance of Wind Power Generation (지형에 따른 발전기 배치가 풍력 발전 성능에 미치는 영향에 관한 수치해석 연구)

  • Lee, Myung-Sung;Lee, Seung-Ho;Hur, Nahm-Keon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.10
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    • pp.901-906
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    • 2010
  • A three-dimensional flow simulation was performed to investigate the flow field in a wind farm on a complex terrain. The present study aims to examine the effects of mountainous terrain and turbine arrangement on the performance of wind power generation. A total of 49 wind turbines was modeled in the computational domain; detailed blade shape of the turbines was considered. Frozen rotor method was used to simulate the rotating operation. The torque acting on the turbine blades was calculated to evaluate the performance of the wind turbines. The numerical results showed details of the flow structure in the wind farm including the velocity deficit in the separated flow regions; this velocity deficit was due to the topographical effect. The effect of the wake induced by the upstream turbine on the performance of the downstream wind turbine could also be observed from the results. The methodology of the present study can be used for selecting future wind-farm sites and wind-turbine locations in a selected site to ensure maximum power generation.

Application of Horizontal Flow Fins Inclined Plate for Sedimentation Efficiencies Improvement in River Water with High Turbidity (고탁도 원수의 침전효율 증대를 위한 수평류식 핀 경사판 적용에 관한 연구)

  • Choi, Jung-Su;Jin, Oh-Suk;Joo, Hyun-Jong
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.9
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    • pp.644-650
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    • 2012
  • The purpose of this study is to evaluate the applicability of Horizontal Flow Fins Inclined Plate (HFIP) for the removal of high-turbidity raw water in water treatment plant. As an experimental result, treated water quality and removal efficiency were 0.34 NTU and 90.45% by the application of HFIP for low-turbidity raw water and for the high-turbidity influent resulted 0.75 NTU and 97.27% in removal efficiency. In view of stability for discharge water NTU, the standard deviation were found as 0.12 NTU for low-turbidity and 0.75 NTU for high-turbidity raw water indicating low fluctuations. Result of flow analysis using CFD (Computational Fluid Dynamic) that the addition of HFIP improves the turbidity treatment followed by the stabilization of flow velocity distribution and increases in settling velocity.

The Analysis of Dynamic Pressure in the Molten Flux near the Meniscus during Mold Oscillation for the Continuous Casting of Steel (강의 연속주조시 Mold Oscillation에 따른 Flux층 내의 동적 압력변화 해석)

  • Park, Tae-Ho;Kim, Ji-Hun;Choi, Joo;Ye, Byung-Joon
    • Journal of Korea Foundry Society
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    • v.24 no.1
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    • pp.26-33
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    • 2004
  • The pressure of the mold flux acting on the meniscus shell was investigated through the coupling analysis of heat transfer in the mold and fluid flow in the flux caused by the mold oscillation. Finite element method was employed to solve the conservation equation associated with appropriate boundary conditions. As reported by previous workers, the axial pressure is positive on the negative strip time and negative on the positive strip time. A maximum pressure is predicted toward the top of the meniscus shell which has the thin shell arid a maximum value is in proportion to the relative mold oscillation velocity. The relative mold oscillation velocity was changed by the effect of meniscus level fluctuation. Therefore the pressure of the mold flux acting on the meniscus shell was different each cycle of the mold oscillation due to the irregularity of relative mold oscillation velocity.

Nonlinear wind-induced instability of orthotropic plane membrane structures

  • Liu, Changjiang;Ji, Feng;Zheng, Zhoulian;Wu, Yuyou;Guo, Jianjun
    • Wind and Structures
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    • v.25 no.5
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    • pp.415-432
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    • 2017
  • The nonlinear aerodynamic instability of a tensioned plane orthotropic membrane structure is theoretically investigated in this paper. The interaction governing equation of wind-structure coupling is established by the Von $K\acute{a}rm\acute{a}n's$ large amplitude theory and the D'Alembert's principle. The aerodynamic force is determined by the potential flow theory of fluid mechanics and the thin airfoil theory of aerodynamics. Then the interaction governing equation is transformed into a second order nonlinear differential equation with constant coefficients by the Bubnov-Galerkin method. The critical wind velocity is obtained by judging the stability of the second order nonlinear differential equation. From the analysis of examples, we can conclude that it's of great significance to consider the orthotropy and geometrical nonlinearity to prevent the aerodynamic instability of plane membrane structures; we should comprehensively consider the effects of various factors on the design of plane membrane structures; and the formula of critical wind velocity obtained in this paper provides a more accurate theoretical solution for the aerodynamic stability of the plane membrane structures than the previous studies.