• Title/Summary/Keyword: Temperature Jump

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Temperature jump and concentration slip effects on bioconvection past a vertical porous plate in the existence of nanoparticles and gyrotactic microorganism with inclined MHD

  • Choudhary, Rakesh;Jain, Shalini
    • Advances in nano research
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    • v.11 no.1
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    • pp.27-36
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    • 2021
  • The paper presents the effects of temperature jump and concentration slip on inclined MHD bioconvection past a vertical porous plate via porous media. The authors have examined how the presence of both nanoparticles and gyrotactic microorganism impact the whole procedure. It is researched that the numerical scheme, called Runge-Kutta fourth fifth order Fehlberg method (RKF45) has been used to solve the governing partial differential equations. The equations are reduced into ordinary differential equations by using suitable similarity transformation. The effects of pertinent parameter for variation in the velocity profile, velocity profile at far field, temperature profile, concentration profile and motile microorganism density profile have been obtained. The results obtained from current study in the concluding part of the paper match to the pre researched data which validate the authenticity of the study.

NUMERICAL STUDY OF WEDGE FLOW IN RAREFIED GAS FLOW REGIME USING A SLIP BOUNDARY CONDITION (희박기체 영역에서 미끄럼 경계조건을 적용한 쐐기 형상 주위의 유동 해석)

  • Choi, Y.J.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.19 no.2
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    • pp.40-48
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    • 2014
  • For rarefied gas flow regimes, physical phenomena such as velocity slip and temperature jump occur on the solid body surface. To predict these phenomena accurately, either the Navier-Stokes solver with a slip boundary condition or the direct simulation Monte Carlo method should be used. In the present study, flow simulations of a wedge were conducted in Mach-10 flow of argon gas for several different flow regimes using a two-dimensional Navier-Stokes solver with the Maxwell slip boundary condition. The results of the simulations were compared with those of the direct simulation Monte Carlo method to assess the present method. It was found that the values of the velocity slip and the temperature jump predicted increase as the Knudsen number increases. Also, the results are comparatively reasonable up to the Knudsen number of 0.05.

Numerical Analysis of the Slip Velocity and Temperature-Jump in Microchannel Using Langmuir Slip Boundary Condition (미소채널내의 Langmuir 미끄럼 경계조건을 통한 미끄럼 속도 및 급격한 온도변화에 관한 수치해석)

  • Kim, Sang-Woo;Kim, Hyun-Goo;Lee, Do-Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.3
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    • pp.164-169
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    • 2009
  • The slip velocity and the temperature jumps for low-speed flow in microchannels are investigated using Langmuir slip boundary condition. This slip boundary condition is suggested to simulate micro flow. The current study analyzes Langmuir slip boundary condition theoretically and it analyzed numerically micro-Couette flow, micro-Poiseuille flow and grooved microchannel flow. First, to prove validity for Langmuir slip condition, an analytical solution for micro-Couette flow is derived from Navier-Stokes equations with Langmuir slip conditions and is compared with DSMC and an analytical solution with Maxwell slip boundary condition. Second, the numerical analysis is performed for micro-Poiseuille flow and grooved microchannel flow. The slip velocity and temperature distribution are compared with results of DSMC or Maxwell slip condition and those are shown in good agreement.

Study on Optimization of Temperature Jump-Bending Process for Reducing Thickness Attenuation of Large-Diameter Steel Pipe (대구경 곡관 두께감소율 제어를 위한 온도점프 벤딩 공정의 최적화에 관한 연구)

  • Xu, Zhe-Zhu;Kim, Lae-Sung;Jeon, Jeong-Hwan;Liang, Long-Jun;Choi, Hyo-Gyu;Lyu, Sung-Ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.4
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    • pp.21-27
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    • 2015
  • Induction bending is a method that allows the bending of any material that conducts electricity. This technology applies a bending force to a material that has been locally heated by an eddy current induced by a fluctuating electromagnetic field. Induction bending uses an inductor to locally heat steel through induction. This results in a narrow heat band in the shape to be bent. In general, the reduction of thickness attenuation of a large-diameter steel pipe is not allowed to exceed 12.5%. In this paper, in order to meet the standard of thickness attenuation reduction, a non-uniform heating temperature jump-bending process was investigated. As a result, the developed bending technique meets the requirements of thickness attenuation reduction for large-diameter steel pipes.

A Study on the Transfer of the Oscillator's Motion Information with 2 Degrees of Freedom;Thermal Boundary Resistance (2자유도 진동계의 운동정보 전달에 관한 연구;경계면열저항)

  • Choi, Soon-Ho;Choi, Hyun-Kye;Jin, Chang-Fu;Kim, Kyung-Kun;Yoon, Seok-Hun;Oh, Cheol
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.06a
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    • pp.1102-1107
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    • 2005
  • The analysis of the thermal boundary resistance is very important in the both cases of microscale and macroscale systems because it plays a role of thermal barrier against a heat flow. Especially, since fairly large heat energy is generated in microscale or nanoscale systems with electronic chips, the thermal boundary resistance is a key factor to guarantee the performance of those devices. In this study, the transfer of the oscillator's motion information with 2 degrees of freedom is investigated for clarifying the mechanism of a thermal boundary resistance. We found that the transfer of the oscillator's motion information is defined as a cross-correlation coefficient and the magnitude of it determines the temperature jump over a solid interface. That is, the temperature jump over an interface increases as the magnitude of a cross-correlation coefficient decreases and vice versa.

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Numerical Investigation of Flows around Space Launch Vehicles at Mid-High Altitudes (중/고고도 영역에서의 우주발사체 주위 유동에 대한 수치적 연구)

  • Choi, Young Jae;Choi, Jae Hoon;Kwon, Oh Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.1
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    • pp.9-16
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    • 2019
  • In the present study, to investigate flows around space launch vehicles at mid-high altitudes efficiently, a three-dimensional unstructured mesh Navier-Stokes solver employing a Maxwell slip boundary condition was developed. Validation of the present flow solver was made for a blunted cone-tip configuration by comparing the results with those of the DSMC simulation and experiment. It was found that the present flow solver works well by capturing the velocity slip and the temperature jump on the solid surface more efficiently than the DSMC simulation. Flow simulations of space launch vehicles were conducted by using the flow solver. Mach number of 6 at the mid-high altitude around 86km was considered, and the flow phenomena at the mid-high altitude was discussed.

Extended Graetz Problem Including Axial Conduction and Viscous Dissipation in Microtube

  • Jeong Ho-Eyoul;Jeong Jae-Tack
    • Journal of Mechanical Science and Technology
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    • v.20 no.1
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    • pp.158-166
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    • 2006
  • Extended Graetz problem in microtube is analyzed by using eigenfunction expansion to solve the energy equation. For the eigenvalue problem we applied the shooting method and Galerkin method. The hydrodynamically isothermal developed flow is assumed to enter the microtube with uniform temperature or uniform heat flux boundary condition. The effects of velocity and temperature jump boundary condition on the microtube wall, axial conduction and viscous dissipation are included. From the temperature field obtained, the local Nusselt number distributions on the tube wall are obtained as the dimensionless parameters (Peclet number, Knudsen number, Brinkman number) vary. The fully developed Nusselt number for each boundary condition is obtained also in terms of these parameters.

Transient heat transfer in thin films (초박막에서의 비정상 열전달)

  • Bai, C.H.;Chung, M.
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.1
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    • pp.1-11
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    • 1998
  • For the analysis of phonon heat transfer within short time and spatial scales, conventional macroscopic heat conduction equations with jump boundary conditions are tried and the results are compared to those of equation of phonon radiative transport(EPRT), which is one of microscopic transport equation. In transient state the macroscopic temperatures show far different behavior from EPRT. In steady state the hyperbolic temperatures with temperature jump at the wall from time relaxation model agrees well with EPRT temperatures. Since EPRT is also an approximate form of microscopic transport equation and there are no experimental results to verify the proposed model in this study, we can not conclude whether the approaching method from this study is valid or not. To the authors' knowledge, there are no experimental results available which can be used to test the validity of these models. Such an experiment, while difficult to conduct, would be invaluable.

Heat Transfer in a Micro-actuator Operated by Radiometric Phenomena

  • Heo Joong-Sik;Hwang Young-Kyu
    • Journal of Mechanical Science and Technology
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    • v.19 no.2
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    • pp.664-673
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    • 2005
  • The heat transfer characteristics of rarefied flows in a micro-actuator are studied numerically. The effect of Knudsen number (Kn) on the heat transfer of the micro-actuator flows is also examined. The Kn based on gas density and characteristic dimension is varied from near-continuum to highly rarefied conditions. Direct simulation Monte Carlo calculations have been performed to estimate the performance of the micro-actuator. The results show that the magnitude of the temperature jump at the wall increases with Kn. Also, the heat transfer to the isothermal wall is found to increase significantly with Kn.

HALL EFFECTS ON HYDROMAGNETIC NATURAL CONVECTION FLOW IN A VERTICAL MICRO-POROUS-CHANNEL WITH INJECTION/SUCTION

  • BHASKAR, P.;VENKATESWARLU, M.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.24 no.1
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    • pp.103-119
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    • 2020
  • In this work, the hydromagnetic and thermal characteristics of natural convection flow in a vertical parallel plate micro-porous-channel with suction/injection is analytically studied in the presence of Hall current by taking the temperature jump and the velocity slip at the wall into account. The governing equations, exhibiting the physics of the flow formation are displayed and the exact analytical solutions have been obtained for momentum and energy equations under relevant boundary conditions. The impact of distinct admissible parameters such as Hartmann number, Hall current parameter, permeability parameter, suction/injection parameter, fluid wall interaction parameter, Knudsen number and wall-ambient temperature ratio on the flow formation is discussed with the aid of line graphs. In particular, as rarefaction parameter on the micro-porous-channel surfaces increases, the fluid velocity increases and the volume flow rate decreases for injection/suction.