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1
Gumgum, Sevin. "The Dual Reciprocity Boundary Element Method Solution Of Fluid Flow Problems." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611605/index.pdf.
Full textAbstract:
In this thesis, the two-dimensional, transient, laminar flow of
viscous and incompressible fluids is solved by using the dual
reciprocity boundary element method (DRBEM). Natural convection and
mixed convection flows are also solved with the addition of energy
equation. Solutions of natural convection flow of nanofluids and
micropolar fluids in enclosures are obtained for highly large values
of Rayleigh number. The fundamental solution of Laplace equation is
used for obtaining boundary element method (BEM) matrices whereas
all the other terms in the differential equations governing the
flows are considered as nonhomogeneity. This is the main advantage
of DRBEM to tackle the nonlinearities in the equations with
considerably small computational cost. All the convective terms are
evaluated by using the DRBEM coordinate matrix which is already
computed in the formulation of nonlinear terms. The resulting
systems of initial value problems with respect to time are solved
with forward and central differences using relaxation parameters,
and the fourth-order Runge-Kutta method. The numerical stability
analysis is developed for the flow problems considered with respect
to the choice of the time step, relaxation parameters and problem
constants. The stability analysis is made through an eigenvalue
decomposition of the final coefficient matrix in the DRBEM
discretized system. It is found that the implicit central difference
time integration scheme with relaxation parameter value close to
one, and quite large time steps gives numerically stable solutions
for all flow problems solved in the thesis. One-and-two-sided
lid-driven cavity flow, natural and mixed convection flows in
cavities, natural convection flow of nanofluids and micropolar
fluids in enclosures are solved with several geometric
configurations. The solutions are visualized in terms of
streamlines, vorticity, microrotation, pressure contours, isotherms
and flow vectors to simulate the flow behaviour.
2
REA, Omar Stevenson Guzman. "Fluido micropolar: existência e unicidade de solução forte." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18552.
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CNPQ
Estudamos aspectos teóricos de um sistema que modela o comportamento dos unidos micro polares incompressíveis num domínio limitado _ Rn (n = 2 ou 3). Especificamente, utilizamos o método espectral de Galerkin para mostrar a existência de soluções fortes e com determinadas condições mostramos a unicidade das soluções
We study theoretical aspects of a system that models the behavior of incompressible micropolar uids in a bounded domain _ Rn (n = 2 or 3). Speci cally, we use the spectral Galerkin method to show the existence of strong solutions and under certain conditions show the uniqueness of solutions.
3
Mostefai, Mohamed Sadek. "Déduction rigoureuse de l'équation de Reynolds à partir d'un système modélisant l'écoulement à faible épaisseur d'un fluide micropolaire, et étude de deux problèmes à frontière libre : Hele-Shaw généralisé et Stephan à deux phases pour un fluide non newtonien." Saint-Etienne, 1997. http://www.theses.fr/1997STET4019.
Full textAbstract:
Dans le chapitre 1, on considère le modèle micropolaire de Navier-Stokes avec conditions de bords de type Dirichlet non homogènes en dimension deux. On donnera un résultat d'existence d'une solution faible en utilisant le théorème du point fixe de Leray-Schauder, puis on prouvera l'unicité de la solution faible du problème sous certaines hypothèses. On établiera une justification mathématique de l’équation de Reynolds généralisé à partir de ce modèle là. On étudiera ensuite la forme de l'équation de Reynolds suivant le choix de la viscosité et des données initiales. Dans le chapitre 2, nous considérons le modèle de Hele-Shaw généralisé dans une cellule laminaire, qui consiste à injecter du fluide, avec un débit non constant w 0, à travers un trou de frontière 1, situé sur l'une des deux surfaces ; et à tenir compte que l'une des surfaces a une géométrie quelconque et animée d'un mouvement relatif vertical. En introduisant un changement de variable de type Baiocchi, le problème initial se ramène à l'étude d'une inéquation variationnelle avec terme de Volterra. L'existence d'une solution pour cette dernière est donnée par le théorème du point fixe de Banach. Des résultats de régularité en espace pour la solution seront prouvés en introduisant un problème pénalisé et en utilisant la méthode de Rothe (semi-discrétisation en temps), puis on montrera que la dérivée par rapport à t de la solution de l'inéquation variationnelle est dans l#(0, t, h#2()), ce dernier résultat nous permet de revenir au problème initial. Dans le chapitre 3, on considère un problème de Stefan à deux phases avec convection. Le problème est gouverné par un système couple non linéaire, comprenant la loi de Darcy pour un fluide non newtonien et l'équation d'équilibre d'énergie avec second membre dans l#1. Pour prouver l'existence de solutions du problème faible on introduira une famille de solutions approchées (#, p#), > 0, définies sur le domaine entier , en insérant une fonction de pénalité convenable dans l'équation de pression. On considère ensuite séparement les problèmes en # et p#, respectivement, et en utilisant le principe de point fixe de Schauder, on montre l'existence de couples solutions (#, p#) du problème approché, pour tout > 0. En faisant tendre vers zéro, on montre que les solutions du problème approché convergent vers une limite (, p) qui est une solution faible du problème variationnel. On montre aussi que la fonction est continue d'où le domaine où > 0 est un ensemble ouvert, et l'interface des deux phases est définie a posteriori comme l'ensemble de niveau = 0. On établira, enfin, quelques relations entre les solutions faibles et classiques, dans le cas d’une courbe assez régulière
4
Martin, Grégoire. "Étude numérique des équations d'un fluide micropolaire." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ51263.pdf.
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5
BENHABOUCHA, Nadia. "Quelques problèmes mathématiques relatifs à la modélisation des conditions aux limites fluide-solide pour des écoulements de faible épaisseur." Phd thesis, Université Claude Bernard - Lyon I, 2003. http://tel.archives-ouvertes.fr/tel-00005482.
Full textAbstract:
Ce travail de thèse est consacré à l'étude asymptotique d'écoulements de faible épaisseur et à la modélisation des conditions aux limites à imposer à l'interface fluide-solide dans différentes situations. Le chapitre 1 est consacré à l'etude asymptotique d'un écoulement fluide constitué d'une couche poreuse mince adjacente à un milieu fluide mince. On met en évidence l'existence d'un rapport critique entre la taille de la microstructure du milieu poreux et les deux épaisseurs, rapport pour lequel une équation de Reynolds modifiée est obtenue. De plus il est montré qu'on peut toujours pour une géométrie réelle se placer dans ce cas critique. Enfin, on présente des simulations numériques qui mettent en évidence les différences entre le modèle présenté ici et deux autres modèles utilisés en mécanique. Dans le chapitre 2, on s'intéresse à l'étude d'un écoulement de faible épaisseur quand une des surfaces est rugueuse. Ceci peut etre relié à l'étude du chapitre précédent en considérant un milieu poreux qui ne comporterait qu'une seule couche. On utilise la technique de la double échelle en homogénéisation pour obtenir rigoureusement les résultats de convergences. En outre, la convergence des contraintes normales et tangentielles sur les surfaces lisses et rugueuses est étudiée. Dans le chapitre 3, on étudie un écoulement d'un fluide non newtonien de type micropolaire avec de nouvelles conditions à l'interface fluide solide couplant la vitesse et la microrotation par l'introduction d'une viscosité de surface. On démontre l'existence et l'unicité de la solution et des estimations a priori qui conduisent, via l'étude asymptotique, à une équation de Reynolds micropolaire généralisée. Une étude numérique montre l'influence des conditions aux limites sur la charge et le coefficient de frottement. Les résultats sont comparés avec ceux d'autres modèles retenant une condition d'adhérence à la paroi.
6
Labassi, Kamel. "Contribution a la maitrise du dimensionnement des turbines hydrauliques "banki-mitchell"." Paris, ENSAM, 1987. http://www.theses.fr/1987ENAM0005.
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Dimensionnement d'une turbine hydraulique de type banki-mitchell. Etude de l'ecoulement en fluide parfait au travers de la roue. Puissance effective. Hauteur de chute. Application a des micro-centrales hydrauliques
7
Ji, Yan-Cheng, and 季彥成. "Mixed convection of micropolar fluids in a lid-driven enclosure filled with a fluid-saturated porous medium." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/82220661454099916909.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
93
A number of applications in thermal technology require an analysis of convective flow and heat transfer near the thermal boundary condition. The influences of these effects on heat transfer result are much significant. In addition, the study of convection heat transfer in a porous medium has attracted considerable interest because of its important applications in several engineering process, such as chemical, cooling and drying process, etc. Mixed convection heat transfer of micropolar fluids in a lid-driven enclosure filled with a fluid-saturated porous medium is numerically investigated in this study. The governing equations for micropolar fluid were first presented by A.C. Eringen, wherein we furthermore expand the applications to non-Newtonian fluids. The numerical computations were obtained using the cubic spline collocation method in a personal computer. The governing equations, including stream function, vorticity, microrotation and energy, were first put in dimensionless form. The governing parameters appearing in present study are Pr, Gr, R, λ, Darcy number, and several micropolar parameters. The numerical results of the flow fields are discussed with plot of isotherms, streamlines and velocity vectors. The results indicate that the Newtonian fluid has more significant convection heat transfer effect than that of micropolar fluids.
8
Liu, Keng-Hao, and 劉耿豪. "Transient Convection in Micropolar Fluid Flow Through a Wavy Wall Channel Including the Magnetic Field Effect." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/42790866147250540757.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
90
Forced and mixed convection of micropolar fluids through a periodic array of wavy-wall channel has been analyzed by a simple coordinate transformation method and the spline alternating-direction implicit method. The governing equations of system are derived from complete Navier-Stokes equations with theories of micropolar fluid, we can expand the applications from in Newtonian fluids to in non-Newtonian fluids. The transformed governing equations can expand the irregular boundary into a calculable regular plane, and then solve it by using the spline alternating-direction implicit method (SADI). Numerical results show that, in micropolar fluids, both the velocity of fluid and heat transfer rate would decrease since effects of vortex viscosity, spin-gradient viscosity and micro-inertia density. When the heat transfer surface is lumpy, this displacement of boundary will disturb the flow and alter the heat transfer rate. The synthetic result show that the add quantity of heat transfer area in wavy surfaces is enough to offset the thermal resistance which is due to the geometry surfaces. Therefore, the heat transfer rate of wavy surface is higher than that of the corresponding flat plate in all fluids. Furthermore, it should be noted that the increase in heat transfer rate usually implies the increase in skin-friction coefficient. This would make a penalty in pumping power required for wavy channels. Incluiding the magnetic field effect also can increase the velocity near the wavy surface，so the heat transfer rate is better。
9
Wang, Ying-Chi, and 王盈啟. "A nonlinear rupture analysis of the thin liquid films of micropolar fluid under magnetic field effects." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/36510935295408110173.
Full textAbstract:
碩士國立成功大學
機械工程學系
87
The thesis is conferring to the rupture of the thin liquid film. First, we consider the Newton fluid under magnetic effect and the micropolar fluid on the cylindrical coordinates then consider the micropolar fluid under magnetic effect on the plane plate. This thesis refers to the research to find a nonlinear evolution equation of liquid thin film by long wave small perturbation method and quasi-steady lubrication theory. In order to reveal the physical parameter effect in the first order governing equation, we made the preliminary estimate of the degree. And then we got the simple governing equation and boundary condition. After solve the couple equation with kinetic boundary condition, we can get a nonlinear evolution equation. Finally, we use numerical analysis method to find out the rupture process and the rupture time. In general, the thin liquid film on the cylinder has more plenty of lateral capillary force than it is on plane plate. This force may increase the perturbation of amplitude, and accelerate the rupture of thin liquid film. When the radius of cylinder becomes small and small, the effect of lateral capillary force become remarkable. The result of the micropolar fluid under magnetic effect is similarity to the result of the Newton's fluid.
10
Tessema, Kassahun Mengist. "On free convection and heat transfer in a micropolar fluid flow past a moving semi-infinite plate." Thesis, 2012. http://hdl.handle.net/10413/8852.
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In this dissertation we investigate free convective heat and mass transfer in micropolar fluid flow past a moving semi-infinite vertical porous plate in the presence of a magnetic field. The aim of this study was to use recent semi-numerical methods such as the successive linearisation method and the spectral-homotopy analysis method to study the effects of viscous heating and the effects of different fluid parameters. The governing boundary layer equations for linear momentum, angular momentum (microrotation), temperature and concentration profiles are transformed to a system of ordinary differential equations and solved using the successive linearisation method and the spectral-homotopy analysis method. The accuracy of the solutions was determined by comparison with numerical approximations obtained using the Matlab bvp4c solver. The influences of the micropolar parameter, Darcy number, Prandtl number, Schmidt number, magnetic parameter, heat absorption parameter, Soret and Dufour numbers, local Reynolds number and Grashof number on velocity, microrotation, temperature and concentration profiles were determined. The results obtained are presented graphically and in tabular form.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
11
Yeh, Wen-Yih, and 葉文義. "Transient Convection Heat and Mass Transfer of Micropolar Fluid Flow through a Wavy Channel Including Magnetic Field and Chemical Reaction Effects." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/45639399793821151024.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
91
The micropolar fluids pass through a wavy-wall channel whit magnetic field effect and chemical reaction has been analyzed. We used the theory of micropolar fluid that derived by Erigen and took the chemical parameter that used by Anjalidev. The governing equations of system are derived from complete Navier-Stokes equations with theories of micropolar fluid and chemical reaction parameter. After dimensionless, we used a coordinate transformation method to expand the irregular boundary into a calculable regular and spline alternating- direction implicit (SADI) method to solve the equation. Numerical results show that, heat and mass transfer rate will increase when rise the Reynolds number. In micropolar fluid, though, the characteristics of effects of vortex viscosity, spin-gradient viscosity and micro-inertia density will increase the vorticity, the drag force and transfer rate will get rise and down respectively because of that micropolar fluids has higher viscosity than Newtonian fluid. Use the model of wavy channel will increase the quantity of heat transfer area but it will arise the area of vortex called “dead water”. Including the magnetic field effect can decrease the velocity in the middle of the channel and increase near the wavy surface, and the heat transfer rate will get better. Furthermore, it should be noted that adding in heat transfer rate usually implies the increase in skin-friction coefficient. This would make a penalty in pumping power required for wavy channels. When including the buoyancy force effects cause by temperature and concentration difference will add the velocity and then raise the skin-friction coefficient, Nusselt number and Sherwood number. Chemical reaction is just effect upon the mass transfer rate in mixed convection.
12
Wang, I.-Jan, and 王怡然. "Study on Transient Mixed Convective Heat Transfer of Micropolar Fluid Flow through a Vertical Wavy Plate underMagnetic Field and Chemical Reaction Effects." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/25504550945569849050.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
91
In this study, the coordinate transformation method is used to analyze the transient behavior of the mixed convection in micropolar fluids flow through a vertical wavy surface under magnetic field and chemical raction effect. The governing equations of system are derived from complete Navier-Stokes equations with theories of micropolar fluids, and we can expand the applications from in Newtonian fluids to in non-Newtonian fluids. The transformed governing equations can expand the irregular boundary into a calculable regular plane, and then solve it by using the spline alternating-direction implicit method (SADI). Numerical results show that, in micropolar fluids, with the velocity of fluid and heat transfer rate and mass transfer rate would decrease since effets of vortex viscosity, spin-gradient viscosity and micro-inertia density. After entering the magnetic field, the produced Lorentz force opposed the buoyancy effects, and urges the fluid motion into slowing, then the effects on heat transfer and mass transfer are going to decrease. The chemical reaction induces the concentration change of the fluid, and the concentration gradient in the fluid is not only in one direction. It leads that the effects on mass transfer rate is much stronger than the effects on heat transfer rate. The synthetic result show that the add quantity of heat transfer area in wavy surfaces is enough to offset the thermal resistance which is due to the geometry surfaces. Therefore, the heat transfer rate of wavy surface is higher than that of the corresponding flat plate in all fluids. Furthermore, it should be noted that the increase in heat transfer rate usually implies the increase in skin-friction coefficient.
13
Hong, Kuo-Yi, and 洪國益. "Natural convection of micropolar fluids in an open cavity." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/90500173422465552903.
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碩士國立高雄應用科技大學
機械與精密工程研究所
92
Natural convection heat transfer of micropolar fluids in an open square cavity is numerically investigated in this study. The governing equations for micropolar fluid were first presented by A.C. Eringen, wherein we furthermore expand the applications to non-Newtonian fluids. The numerical computations were obtained using the cubic spline collocation method in a personal computer. The governing equations, including stream function, vorticity, microrotation and energy, were first put in dimensionless form. The governing parameters appearing in present study are Pr, Gr, and several micropolar parameters. The numerical results of the flow fields are discussed with plot of isotherms, streamlines and velocity vectors. The results indicate that the Newtonian fluid has more significant convection heat transfer effect than that of micropolar fluids.
14
Tsai, Jia-Huay, and 蔡佳潓. "On The Solution for Convection Flow of a Micropolor Fluid." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/77750131754685870081.
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Chen, Qing-Gui, and 陳清桂. "Mixed convection of micropolar fluids in a lid-driven enclosure." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/34796502062008466135.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
96
Mixed convection of micropolar fluids in a lid-driven enclosure is numerically investigated in this study. The top and bottom horizontal moving walls are maintained at different constant temperature while left and right walls are adiabatic.The top wall is maintained at a higher temperature than the bottom wall. The governing equations for micropolar fluid were first presented by A.C. Eringen, wherein we furthermore expand the applications to non-Newtonian fluids. The numerical computations were obtained using the cubic spline collocation method in a personal computer. The governing equations, including stream function, vorticity, microrotation and energy, were first put in dimensionless form. The governing parameters appearing in present study are Gr, Re, Ri and several micropolar parameters. The numerical results of the flow fields are discussed with plot and tables of isotherms, streamlines and velocity vectors. The results indicate that the micropolar fluids has more significant convection heat transfer effect than that of Newtonian fluid.
16
Lin, Li-Wei, and 林立偉. "Mixed convection of micropolar fluids in a square vented enclosure." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86846025898577659523.
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碩士國立高雄應用科技大學
機械與精密工程研究所
95
Mixed convection of micropolar fluids in a square vented enclosure is numerically investigated in this study. The fluid flows into the square vented enclosure from an inlet at the bottom surface, and exits from a vent at the top surface. Both the temperature and the velocity of the inflow fluid are kept constant. The governing equations for micropolar fluid were first presented by A.C. Eringen, wherein we furthermore expand the applications to non-Newtonian fluids. The numerical computations were obtained using the cubic spline collocation method in a personal computer. The governing equations, including stream function, vorticity, microrotation and energy, were first put in dimensionless form. The governing parameters appearing in present study are Ri, Re and several parameters of micropolar fluid. The numerical results of the flow fields are discussed with plots and tables of isotherms, streamlines, microrotations and velocity vectors. The numerical solutions indicate that increasing the amount of Re or Ri leads to higher heat transfer coefficient. Besides, the Newtonian fluid has more significant convection heat transfer effect than that of micropolar fluids.
17
HUANG, CAI-WANG, and 黃財旺. "Study on lubrication performance of micropolar fluids in journal bearings." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/45713074134808883990.
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博士國立成功大學
機械工程研究所
79
Since the properties of the lubricants containing suspended particles or polymeric molecules are no longer those of the bulk, their flow behavior was studied through the theory of microploar fluids instead of classical continuum mechanics. In addition to the usual concepts of classical continuum mechanics, there are two main physical concepts in the theory of the micropolar fluids: the internal spin of the fluid particles and the couple stresses. So the micropolar fluid has two independent vector fields : the vector field representing the translation velocities of the fluid particles and the vector field representing the angular ( or spin ) velocities of the fluid particles, and can support the surface and body couples due to the effects of couple stresses. The subject of this research is to analyze the performance of the finite-width fournal bearings lubricated by micropolar fluids. The items considered are the dynamic characteristic coefficients, the critical stability parameter and the critical whirling speed of the journal beraing, which are mainly influenced by the eccentricity ratio, the width-to -diameter ratio, the coupling number and the ratio of clearance to characteristic length of micropolar fluids. A computer program is developed for the above mentioned lubrication problem in order to solve the generalized Reynolds equation by a finite difference method with an iterative procedure, claculate the steady state performance by the numerical differentiation and integration, and analyze the dynamic characteristics by the linearized stability theory. Compared to the Newtonian fluids, the micropolar fluids exhibit higher load capacity and friction drag, lower friction coefficient, but the same side flow rate in the steady state; and show lower normal stiffness coefficients, normal damping coefficients and critical stability parameter, but higher whirling speed in the dynamics. When the width-to -diameter ratio is smaller, and the eccentricity ratio and the coupling number are larger, the polar effects of micropolar fluids becomes more obvious. Besides, the ratio of clearance to characteristic length at the strongest polar effects varies with different width-to-diameter ratio, since the effect of couple stresses is length-dependent. 含微粒或高分子聚合物之潤滑劑，因不具均質性，古典流體力學無法解析，通常採實 驗求得之本構方程式求近似解或以微極流體理論求其潤滑性能，微極流體理論考慮流 元中微粒旋轉量及流場中的應力偶(couple stresses) ，因此該理論有兩個基本的獨 立運動向量場，一為傳統之流元速度向量場，另一為微粒相對於流元之角速度向量場 ；同時由於流場中的應力偶，微極流體能支持面偶力及體偶力(surface and body couples)。 本文以微極流體理論解析定長頸軸承含微粒液膜之潤滑性能及穩定性，探討頸軸偏心 比，寬徑比及微極流體耦合參數，N ，間隙與特徵長度比參數，L 等對頸軸穩態潤滑 性能及動態特性係數，穩定性參數，臨界液膜渦漩轉速之影響；文中採用有限差分法 解定長頸軸承之雷諾方程式，然後以數值積分計算定長頸軸承之穩定態潤滑性能；並 以線性化穩定性理論解析定長頸軸承液膜之動態特性係數，穩定性及臨界渦漩轉速。 分析結果顯示，在穩態潤滑性能方面，由於微極流體中微粒之微轉動及流場中之應力 偶效應能提高頸軸承汶膜徑向及周向不同程度的等效黏度，因而提高頸軸承之負載能 力、磨阻力及同時降低磨阻係數，但是頸軸承汶膜之側流量並不因負載能力的提高而 增加。動態特性方面，微極流體具有較牛頓流體為低的正剛性係數、正阻尼係數、較 差的穩定性及較大之臨界渦漩轉速。微極流體在頸軸承潤滑中，影響潤滑性能的因素 有頸軸承寬徑比，偏心比，耦合參數及軸承間隙與微粒特徵長度比參數四者，當較小 寬徑比（即較短頸軸承），較大偏心比（或較大負荷）及較大耦合參數時，微粒微旋 轉之效應較大。然而應力偶效應為長度依賴效應(length dependent effect) ，因此 應力偶效應最大時不同寬徑比之頸軸承具有不同之軸承間隙與微粒特徵長度比值。
18
Gu, Shu-Cheng, and 古戍成. "Effects of micropolar fluids to the performance of parabolic slider bearings." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/05565253306256954993.
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碩士桃園創新技術學院
機械工程系機械與機電工程碩士班
103
The influences of micro-polar non-Newtonian lubricant and shape factor δ to the parabolic steady-state sliding bearing performances were investigated in this thesis. The properties of micro-polar fluid could be described with parameters of characteristic material length ι and dimensionless coupling parameter N. According to the studies, the shape factor δ has a great affect to the bearing pressure distribution, the larger the value of δ is, the greater offset to the bearing right end side of the pressure distribution and position of maximal pressure are. Besides, characteristic material length ι and dimensionless coupling parameter N can enhance both the bearing pressure rather than the pattern of the pressure distribution. Within the analytic values of δ, the maximal bearing loading capacity F*max occurred all at shape factor δ was 1.4; that is, δ＝1.4, the parabolic sliding bearing will have the optimal bearing performances. As about to position of the loading center, affected most by the shape factor δ. Whatever the value δ is, the position of the loading center will locate all at the right end side of journal bearing (X*c≧0.53); the larger the value δ is, the more offset of the loading center to the outlet zone of bearing.
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Chang, Cheng Long, and 張振龍. "The analysis of boundary effects on convective heat transfer of micropolar fluids." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/04876213545522151333.
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Wang, Chen-Chieh, and 王鎮傑. "Natural Convection of Micropolar Fluids in an Enclosed Cavity under Magnetic Field Effects." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/08490083836053353691.
Full textAbstract:
碩士國立成功大學
機械工程研究所
82
In this thesis the transient natural convective heat transfer analysis of micropolar fluids which are effected by the external constant magnetic field, vertical with gravity, and the two side walls are maintained at constant temperature deference is studi- ed. By controling the magnitude of the external magnetic field the heat flux from the wall can be controlled. The dynamic of micropolar fluids has received the attention of many researchers. This theory includes the effects of local rota- ry inertial and couple stress and is expected to provide a mathe- matical model for the non-Newtonian fluid behavior. SADI (spline alternating direction implicit ) method is appli- ed to solve the present problem. In order to compare the numeric- al accuracy and the material characteristics, the flow fields of Newtonian fluid have also been solved. The results obtained indi- cate that the cubic spline technique is an efficient method for solving this problem. Average and local Nusselt number, distribution of velocity at X=0.5 or Y=0.5, stream-line , and distribution of temperature are showed in this paper. The results show that when the magnitude of the external magnetic field increases the flow characteristics reduce.In other words,the stronger external magnetic field is the less heat transfer will become.The aforementioned points explica- te in this text in detail.
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Shich, Jow-Yiing, and 謝卓穎. "Studies on Transient Natural Convection Heat Transfer of Micropolar Fluids between Concentric Spheres." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/84083918842755233822.
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Wang, Shun-Ching, and 王舜卿. "Natural Convection Heat Transfer of Micropolar Fluids Between Concentric and Vertical Eccentric Cylinders." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/45649005546211585633.
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Chou, Huann-Ming, and 周煥銘. "Studies on Natural Convection Heat Transfer of Micropolar Fluids by Using the Coordinate Transformation Method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/44240490244709176174.
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Huang, Yu-Sheng, and 黃毓勝. "Heat and mass transfer of micropolar fluids over a vertical wavy surface with injection and suction." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/20717877729101985062.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
93
Heat and mass transfer of micropolar fluids by natural convection over a vertical wavy surface with suction or injection are analyzed in this study. The governing equations for micropolar fluids were first presented by A.C. Eringen, we expand the application in a Newtonian fluid to that in non-Newtonian fluids. The numerical computations were employed by the cubic spline collocation method in a personal computer. The transformed governing equations change the irregular boundary into a calculable regular plane. The governing parameters appearing in present study are α,Sc,C,Pr and several micropolar fluid parameters. The range of Grashof number is from 104 to 105, Pr=10. Also, the effect of various suction or injection velocity on the wall surface, skin-friction coefficient, micropolar parameter R and concentration parameter on the flow fields are considered. Numerical results show that the enhanced quantity of heat transfer area in awavy surface is enough to offset the thermal resistance which is due to the geometry surfaces. Therefore, the heat transfer rate of a wavy surface is higher than that of a corresponding flat plate.
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Hung, Kuo-Yi, and 洪國益. "Investigation on convection heat transfer of micropolar fluids passing through a wavy channel saturated with porous media." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/42554444255481045122.
Full textAbstract:
博士國立高雄應用科技大學
機械與精密工程研究所
102
The transient and steady state heat convection phenomena of micropolar fluids flowing through wavy channels with porous media are numerically analyzed by using the coordinate transformation and the spline alternating-direction implicit method. Numerical results considering about the material characteristics of micropolar fluids and comparing with Newtonian fluid are discussed in details. Calculations are performed on a personal computer by using the SADI (Spline Alternating-Direction Implicit Method), which applies the theory of coordinate transformation and transforms complex curves into flat surface. The governing equations after non-dimensional transformation are expressed with stream function, vortex function, angular momentum and temperature function, and the transient and steady state heat transfer effect is determined to discuss forced and mixed heat convection of micropolar fluid in vertical wavy channels saturated with porous media. The numerical results indicate that the wavy surface is lumpy, the displacement of boundary causes the flow field to change and further affects heat transfer rate. Both the minimum and maximum of average Nusselt numbers occur nearby the wave troughs and wave peaks. The integral value of average Nusselt number for the sin2-wave forms induces the variation of average Nusselt number against the longitudinal direction merely occurring nearby the half-front portion of the wavy channel. The figure also displays that the average Nusselt number of a flat plate (a=0) is larger than those of wavy channels. Also, they decrease with increasing value of amplitude. One of the reasons why a complex-wavy wall is more efficient in heat transfer is its capability to promote a correspondingly complicated fluid motion near the surface. The numerical results demonstrate that the additional harmonic substantially alters the flow field and temperature distribution. Moreover, the total heat-transfer rate for a complex-wavy wall channel is greater than that for a corresponding flat plate or for a single-wavy surface. The micropolar fluids have higher flow resistance but lower heat transfer rate. As the wavy surface is lumpy, the displacement of boundary causes the flow field to change and further affects heat transfer rate. The magnetic field effect also can increase the velocity near the wavy surface, so the heat transfer rate is better. The higher the Ri value indicates more apparent buoyancy effect, reduced recirculation flow in the trough region and increased velocity gradient at the surface, thereby leading to higher Nusselt number and heat transfer rate.
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Ji, You-Jheng, and 紀侑政. "Effect of a local heater on natural convention of micropolar fluids in a square enclosures filled with a porous medium." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/78262745525874824469.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
96
Natural convection in heat transfer of micropolar fluids in a square enclosure with a local heater on left wall is numerically investigated in this study. The governing equations for micropolar fluid were first presented by A.C. Eringen, wherein we furthermore expand the applications to non-Newtonian fluids. The numerical computations were obtained using the cubic SADI (Spline Alternating-Direction Implicit Method) collocation method in a personal computer. The governing equations, including stream function, vorticity, microrotation and energy, were first put in dimensionless form. The governing parameters appearing in present study are Pr, Ra,Darcy and several micropolar parameters. The numerical results of the flow fields are discussed with plot of isotherms, streamlines and velocity vectors. The results indicate that the effect of convective heat transfer depends on the location of the local heater to a large extent.