Browsing by Author "Fu, Wu-Shung"

Now showing 1 - 20 of 34

A mixed convection in a reciprocating Pi shape channel with opposite direction of gravity and inlet cooling fluids
(2009-04-01)
Fu, Wu-Shung
;
Lian, Sin-Hong
;
Lai, Yu-Chih
;
機械工程學系
;
Department of Mechanical Engineering
A numerical study is executed to investigate heat transfer mechanisms of a reciprocating channel cooled by fluids. The problem of the reciprocating piston is a moving boundary problem, and the Finite Element Method and arbitrary Largragian-Eulerian Kinematics method are then utilized. Due to the high temperature of the channel, a mixed convection is taken into consideration for simulating a more realistic situation. Directions of inlet cooling fluids and gravity are opposite. Concerning important parameters of the Reynolds number and Grashof number, reciprocating frequency and amplitude are examined. Thermal stratification layers which are found firmly on the top surface are deeply dependent on the magnitude of Gr/Re(2) ratio which directly affects the heat transfer mechanisms.
A new method of adjustment of inlet boundary for improving heat transfer of mixed convection in a vertical channel
(2016-10)
Fu, Wu-Shung
;
Chao, Wei-Siang
;
Wu, Pei-Jung
;
Lin, Yu-Ming
;
機械工程學系
This article is dedicated to a new method for improving heat transfer of mixed convection in a vertical channel from the numerical perspective. An adjustable inlet boundary is proposed in the new method to substitute an inlet that is completely occupied by the amount of fluid provided by forced convection included in mixed convection. According to this new method, the flow reversal occurring in the large Richardson number situation can be eliminated significantly, which results in an improvement in the heat transfer rate of mixed convection. In order to investigate a compressible flow problem, this study focuses on four methods, i.e., Roe scheme, preconditioning, dual time stepping, and the LUSGS (Lower Upper Symmetric-Gauss Seidel), to solve the governing equations. Except for the aperture occupied by the mount of fluid provided by forced convection, this study simulates the non-reflecting boundary conditions in other open boundaries. Based on our previous study which has successfully explored a phenomenon of flow reversal, this study intends to enhance the heat transfer rate under this circumstance, and the result has shown a significant improvement, by 29 percentage, comparing with the previous study. Also, a criterion of estimation of the necessity of forced convection included in mixed convection is proposed for enhancing heat transfer rate. Present results and existing results have good agreement. (C) 2016 Elsevier Ltd. All rights reserved.
An enhancement of the back region forced convection heat transfer rates of a reciprocating curved channel with a rib by the ALE method
(2013-12-01)
Fu, Wu-Shung
;
Lai, Yu-Chih
;
Huang, Shang-Hao
;
機械工程學系
;
Department of Mechanical Engineering
An enhancement of the back region forced convection heat transfer rates of a reciprocating curved channel with a rib by the ALE method is investigated numerically. In order to avoid damage caused by a huge difference of heat transfer rates between the front and back regions of a reciprocating curved channel, a rib is selected and installed at an appropriate location to enhance the heat transfer rate of the back region. In the ALE method, the generalized minimal residual method preconditioned by the mesh free pressure convection-diffusion in which the pressure terms are arranged in a finite element linearized matrix system is used to solve governing equations. The results show that the heat transfer rate of the back region is indeed enhanced by the installation of the rib at an appropriate location. (C) 2013 Elsevier Ltd. All rights reserved.
An experimental investigation of a block moving back and forth on a heat plate under a slot jet
(2007-07-01)
Fu, Wu-Shung
;
Tseng, Ching-Chi
;
Huang, Chien-Ping
;
Wang, Ke-Nan
;
機械工程學系
This experimental study aims to investigate heat transfer phenomena caused by a moving block under a jet flow. The experimental apparatus includes three main systems of a jet flow, periodical movement and heating control. The work fluid is air and the data runs are performed for jet Reynolds numbers and speeds of moving block. The comparison between experimental and numerical results show good consistence, and the destruction of boundary layers discovered by previous authors' numerical results is validated. The enhancement of heat transfer rate is generally accompanied with the increment of jet Reynolds number and speed of moving block. (C) 2005 Elsevier Ltd. All rights reserved.
An experimental investigation of a mixed convection in a (sic) shape channel subject to a reciprocating motion
(2009-07-01)
Fu, Wu-Shung
;
Lian, Sin-Hong
;
Lin, Ching-Lun
;
Yang, Chung-Lin
;
機械工程學系
An experimental work is conducted to study heat transfer phenomena of a mixed convection in a (sic) shape channel which is subject to a reciprocating motion. Simultaneously, a numerical calculation is executed to validate the experimental results auxiliarily. Parameters of Reynolds number, frequency and amplitude are considered. The results show that enhancement of heat transfer rate caused by the reciprocating motion is remarkable. Due to the impingement of cooling fluids, the heat transfer rate of the front heat region is still superior to those of the middle and back heat regions. The phenomena of this object are very complicated, and the maximum deviation between the experimental and numerical results is not over 25%. (C) 2009 Elsevier Ltd. All rights reserved.
An investigation of a dual-reflection phenomenon of a natural convection in a three dimensional horizontal channel without Boussinesq assumption
(2010-03-01)
Fu, Wu-Shung
;
Li, Chung-Gang
;
Tseng, Ching-Chi
;
機械工程學系
;
Department of Mechanical Engineering
An investigation of a dual-reflection phenomenon of a natural convection induced by a high temperature difference in a three dimensional horizontal channel is studied numerically. Because of a situation of high temperature difference, the Boussinesq assumption usually made in the natural convection problem is no longer available, the effects of the compressibility of fluid on all related factors must be considered. Solution methods of Roe. preconditioning and dual time stepping are appropriate for low speed compressible flow field and combined to solve the governing equations. For saving computation time, the computational process is parallel and 8 processors are used. At the aperture of the horizontal channel, the directions of fluid flows in the upper and lower regions are opposite which results in the reflection problems in the upper and lower regions induced by the large difference between the velocities of acoustic waves and fluids being completely different. The two different reflections phenomena occurring at the same aperture is conveniently named as a dual-reflection phenomenon which has never been investigated. (C) 2009 Elsevier Ltd. All rights reserved.
An investigation of a high temperature difference natural convection in a finite length channel without Bossinesq assumption
(2009-05-01)
Fu, Wu-Shung
;
Li, Chung-Gang
;
Huang, Chien-Ping
;
Huang, Jieh-Chau
;
機械工程學系
For expanding industrial applications of a natural convection in a channel under a high temperature difference, a compressible fluid flow is taken into consideration in governing equations instead of renunciation of the Bossinesq assumption. Due to the slowness of the velocity of fluid in the natural convection, the Roe scheme matching methods of preconditioning and dual-time stepping are used to solve the governing equations. In order to resolve reflections induced by acoustic waves at the boundaries of the channel, non-reflection conditions at the boundaries of the channel are derived. The results show that a more reasonable pressure distribution in the channel is first validated and average Nusselt numbers are expressed in terms of Rayleigh number for a wide range temperature difference. (C) 2009 Elsevier Ltd. All rights reserved.
An investigation of a mixed convection in a boolean OR shape channel moving with a reciprocating motion
(2009-11-01)
Fu, Wu-Shung
;
Lian, Sin-Hong
;
Lai, Yu-Chih
;
機械工程學系
;
Department of Mechanical Engineering
This study focuses on utilizing numerical calculation to investigate the heat transfer mechanisms in a shape reciprocating channel system comprised of a horizontal channel at the bottom and vertical channels on both left and right sides. The issue is considered one kind of moving boundary problems and the finite element and Arbitrary Lagrangian-Eulerian (ALE) kinematic methods can be applied to this study. Due to the high temperature at the bottom surface of the horizontal channel and the direction of inlet cooling fluids in the same direction of the gravity, the heat transfer mechanisms induced by the mixed convection flow become extremely complex. The results show that thermal layers near the heat surface are disturbed drastically and the effect of reciprocating motion upon the heat transfer mechanisms strongly depends on a relationship between Reynolds and Grashof numbers. (C) 2009 Elsevier Ltd. All rights reserved.
An investigation of compressible forced convection in a three dimensional tapered chimney by CUDA computation platform
(2011-07-01)
Fu, Wu-Shung
;
Wang, Wei-Hsiang
;
Huang, Yun
;
Li, Chung-Gang
;
機械工程學系
Compressible forced convection in a three dimensional tapered chimney is investigated numerically. Schemes of Roe and preconditioning are adopted to resolve compressible flow problem under a low speed velocity situation. Coordinates transformation of algebraic grid generation and non-reflecting boundary condition is used to execute the coordinated transformation of the tapered duct and decrease the computation domain, respectively. Computing procedures are performed on the CUDA computation platform which is developed recently and is a very effective tool. Due to the variation of the geometry of three dimensional tapered chimney, the flow velocity increases in the central region and decreases near the corner region. Therefore, heat transfer rates are enhanced remarkably in the central region and become inferior abruptly near the corner region. The efficiency of CUDA computation platform is marvelous, and the possibility of capability of super computation of individualization may be realized by using the CUDA computation platform. (C) 2011 Elsevier Ltd. All rights reserved.
An Investigation of Compressible Turbulent Forced Convection by an Implicit Turbulence Model for Large Eddy Simulation
(2013-12-01)
Fu, Wu-Shung
;
Li, Chung-Gang
;
Tsubokura, Makoto
;
Huang, Yun
;
Domaradzki, J. A.
An investigation of compressible turbulent forced convection in a three-dimensional channel flow is studied numerically by an implicit turbulence model for large eddy simulation (LES). Because of a high temperature difference between two walls and turbulent flow, the compressibility and viscosity of fluid should be taken into consideration simultaneously. Methods of the Roe scheme, preconditioning, and dual time stepping coordinating an implicit turbulence model for LES are used for resolving the effect of the compressibility of fluid on a low speed flow field. The magnitudes of Re-tau based on the friction velocity changing from 180 to 940, with the high temperature difference of two walls of 500k are conducted. The results of the mean velocity profiles and turbulent intensities are in good agreement with the benchmark DNS data obtained by spectral codes from a low Reynolds number (Re-tau =180) to a high Reynolds number (Re-tau = 940). Besides, the larger the Re-tau is, with the exception of acquirement of larger average Nusselt number, the more drastic variation of local instantaneous Nusselt number is observed.
An investigation of effects of heights and a length on natural convection of three dimensional parallel plates with a heated bottom surface by a CUDA computation platform
(2013-12-01)
Fu, Wu-Shung
;
Huang, Shang-Hao
;
Wang, Wei-Hsiang
;
機械工程學系
;
Department of Mechanical Engineering
Effects of heights and a length on natural convection of three dimensional parallel plates with a heated bottom surface are investigated numerically. The compressibility of fluid induced by a high temperature difference is taken into consideration for simulating more realistic situations, and then the Boussinesq assumption is not necessary to be adopted. Methods of the Roe scheme, preconditioning and dual time stepping matching the method of LUSGS are simultaneously used to solve the compressible flow problem. Non-reflecting boundary conditions are held on apertures to prevent reflections from apertures induced by pressure waves. A CUDA computational platform is used to economize massive computing time. Under a low height case, the flow field is restricted by the shear force caused by the low height and displays a stable situation. Oppositely, under a high height case the flow field indicates active behaviors and an irregular situation is observed. (C) 2013 Elsevier Ltd. All rights reserved.
An investigation of flow reversal of mixed convection in a three dimensional rectangular channel with a finite length
(2013-09-01)
Fu, Wu-Shung
;
Lai, Yu-Chih
;
Huang, Yun
;
Liu, Kuan-Lan
;
機械工程學系
An investigation of flow reversal of mixed flow in a three dimensional channel is studied numerically. At a high Richardson number, natural convection dominates the flow and thermal fields of mixed convection. Behaviors of the residual mass flow rate produced by the difference of the strength of natural and forced convections coexisting in mixed convection are worthy to be examined deeply for industrial applications. Due to the necessity of considering the fluid compressibility, methods of the Roe scheme, preconditioning and dual time stepping are adopted to solve governing equations. The results show that at a high Richardson number situation, via the outlet in large quantities of fluids are sucked into the channel from the outside that causes the flow and thermal fields in the channel to be unsteady and vice versa. (C) 2013 Elsevier Ltd. All rights reserved.
An investigation of heat transfer of a reciprocating piston
(2006-11-01)
Fu, Wu-Shung
;
Lian, Sin-Hong
;
Hao, Liao-Ying
;
機械工程學系
;
Department of Mechanical Engineering
A numerical simulation of a reciprocating piston cooled by fluid is performed to investigate effects of frequency, amplitude and Reynolds number on heat transfer rate of the piston. For facilitating the analyses, the model of the reciprocating piston is replaced by a "Pi" shape cooling channel. This subject belongs to a kind of moving boundary problems, and the Finite Element Method and arbitrary Lagragian-Eulerian Kinematics description method are then utilized. The heat transfer mechanisms affected by the main parameters of frequency, amplitude and Reynolds number are discussed in detail. The results show that the heat transfer mechanisms influenced by the frequency are more remarkable than those influenced by the amplitude and Reynolds number. Besides, the larger the above three parameters are, the apparent enhancements of heat transfer are usually obtained. (c) 2006 Elsevier Ltd. All rights reserved.
An investigation of natural convection in a three dimensional square wavy channel
(2015-08-01)
Fu, Wu-Shung
;
Huang, Kun-Rong
;
Lo, Chi-Xiu
;
Wang, Wei-Hsiang
;
機械工程學系
Natural convection in a three dimensional wavy channel, which is composed of numerous two dimensional cross sections, is investigated numerically. The method of elliptic partial differential equations grid generation is adopted to construct a distribution of grids on each cross section. The distributions of the whole cross sections are piled up in sequence from the inlet to outlet to form a three dimensional channel. In order to solve a low speed compressible flow problem, the compressibility and viscosity of the working fluid are taken into consideration, and the non-reflecting boundaries at the inlet and outlet of the channel are held. The Bossinesq assumption is then no longer necessary. As well, the methods of the Roe scheme, preconditioning and dual time stepping matching the implicit LUSGS algorithm (Implicit Lower Upper symmetric Gauss-Seidel algorithm) are simultaneously used to solve governing equations. Effects of the Rayleigh number and the ratio of the amplitude to wave length on heat transfer rates of the channel are examined. Results of both this study and existing studies have good agreements. (C) 2015 Elsevier Ltd. All rights reserved.
An investigation of natural convection in a three dimensional tapered chimney without Boussinesq assumption
(2012-04-01)
Fu, Wu-Shung
;
Huang, Yun
;
Wang, Wei-Hsiang
;
機械工程學系
;
Department of Mechanical Engineering
Natural convection in a three dimensional tapered chimney is investigated numerically. In order to investigate the natural convection under a high temperature difference situation. Boussinesq assumption is not adopted instead of consideration of the compressibility of fluid. Methods of Roe scheme, preconditioning and dual time stepping are used to solve governing equations for a low speed compressible flow. Coordinates transformation of algebraic grid generation and non-reflecting boundary condition are used to facilitate computation processes. The results reveal that in the expanding duct local Nusselt numbers distributed around the corner region are larger than those distributed around the central region. An available correlation equation is proposed and is well consistent with the numerical results. (C) 2012 Elsevier Ltd. All rights reserved.
An investigation of natural convection in parallel square plates with a heated bottom surface by an absorbing boundary condition
(2013-01-01)
Fu, Wu-Shung
;
Wang, Wei-Hsiang
;
Li, Chung-Gang
;
Huang, Shang-Hao
;
機械工程學系
A study of natural convection in three dimensional square plates is investigated numerically. Several open boundaries co-exist in the physical domain, and a non-reflecting boundary condition applied at the aperture is no longer suitable for solving the problem of this study. An absorbing boundary condition is then adopted and modified in the solution processes. Methods of the Roe scheme, preconditioning and dual time stepping matching LSUGS scheme are used to solve a situation of a low speed compressible flow. The geometry of the physical model is the parallel square plates, and the parameter of Rayleigh number is not high, and then phenomena observed are almost symmetrical. The results of the work have good agreements with the experimental results of a previous paper. (c) 2012 Elsevier Ltd. All rights reserved.
An investigation of natural convection in parallel square plates with a heated top surface by a hybrid boundary condition
(2014-10-01)
Fu, Wu-Shung
;
Wang, Wei-Hsiang
;
Li, Chung-Gang
;
機械工程學系
;
Department of Mechanical Engineering
Natural convection in parallel squares plats with a heated top surface is investigated numerically. For solving a problem induced by different directions between the thermal diffusion and main flow streams, a hybrid boundary condition composed of the absorbing boundary condition and local one-dimensional inviscid relations (LODI) method is then adopted in artificial buffer zones. Methods of the Roe scheme, preconditioning and dual time stepping matching the Monotone Upstream-centered Schemes for Conservation Laws (MUSCL) are used to solve low speed compressible flows caused by natural convection. The results show that the hybrid boundary condition successfully prevents the rebound of heat energy from the artificial buffer zone back to the domain. The area-averaged Nusselt numbers of this study are slightly larger than those of existing experimental results, and the averaged deviation is about 10%. (C) 2014 Elsevier Masson SAS. All rights reserved.
An investigation of natural convection in parallel square plates with a heated top surface by a hybrid boundary condition
(2014-10-01)
Fu, Wu-Shung
;
Wang, Wei-Hsiang
;
Li, Chung-Gang
;
機械工程學系
;
Department of Mechanical Engineering
Natural convection in parallel squares plats with a heated top surface is investigated numerically. For solving a problem induced by different directions between the thermal diffusion and main flow streams, a hybrid boundary condition composed of the absorbing boundary condition and local one-dimensional inviscid relations (LODI) method is then adopted in artificial buffer zones. Methods of the Roe scheme, preconditioning and dual time stepping matching the Monotone Upstream-centered Schemes for Conservation Laws (MUSCL) are used to solve low speed compressible flows caused by natural convection. The results show that the hybrid boundary condition successfully prevents the rebound of heat energy from the artificial buffer zone back to the domain. The area-averaged Nusselt numbers of this study are slightly larger than those of existing experimental results, and the averaged deviation is about 10%. (C) 2014 Elsevier Masson SAS. All rights reserved.
An investigation of natural convection of three dimensional horizontal parallel plates from a steady to an unsteady situation by a CUDA computation platform
(2012-08-01)
Fu, Wu-Shung
;
Wang, Wei-Hsiang
;
Huang, Shang-Hao
;
機械工程學系
;
Department of Mechanical Engineering
"The heat transfer of natural convection in three dimensional horizontal parallel plates with a heated bottom surface is investigated numerically. For enlarging the application domain, the compressibility of the fluid is taken into consideration instead of the Boussinesq assumption. Numerical methods of the Roe scheme, preconditioning and dual time stepping are adopted for solving governing equations of a low speed compressible flow. A non-reflection condition is used at both apertures in order to decrease computational grids and a CUDA computational platform is developed to economize massive computing time. Variations of thermal and flow fields are examined in detail. The results show that accompanied with elongating the length of the heated bottom surface, both thermal and flow fields are changed from a steady to an unsteady situation. (C) 2012 Elsevier Ltd. All rights reserved."
An investigation of the unstable phenomena of natural convection in parallel square plates by multi-GPU implementation
(2017)
Fu, Wu-Shung
;
Wang, Wei-Hsiang
;
Li, Chung-Gang
;
Tsubokura, Makoto
;
機械工程學系
Unstable phenomena induced by natural convection of parallel square plates are investigated numerically. The geometry belongs to the open boundary problem, and the compressibility of fluids is taken into consideration. The absorbing boundary condition and modified local one-dimensional inviscid relation method are adopted for open boundaries. Numerical methods of the Roe scheme, preconditioning, and dual time stepping matching the data-parallel lower-upper relaxation method are coordinated with multi-GPU implementation. Unstable phenomena of natural convection caused by the buoyancy force can be observed. Present results have good agreement with the experimental results in the overlap range of the existing study.