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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 1472-1481 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The steady fluid flow that is initiated by a cascade of cylinders, which oscillates harmonically in an unbounded, incompressible, viscous fluid that is otherwise at rest, is investigated, both numerically and experimentally. Finite-difference techniques are used to obtain the numerical solutions, and the streaming flow results show a reasonable agreement with the experimental data. It is found, both numerically and experimentally, that for large values of the streaming Reynolds number, Rs, the flow is not symmetrical about the axis of the oscillation, i.e., there exists a critical value of Rs, Rs0 say, such that the streaming flows for Rs(approximately-greater-than)Rs0 are unstable and those for Rs〈Rs0 are stable. In order to understand this asymmetry, a stability analysis is performed, and the agreement between the theory and the experimental results is encouraging.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 22 (1988), S. 125-127 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung In dem Aufsatz wird die freie Konvektion von einer horizontalen, linienförmigen Wärmequelle untersucht, die in ein unbegrenztes poröses Medium eingebettet ist. Die Poren des porösen Mediums sind mit einem Fluid gefüllt, das unter Schwerkrafteinfluß ruht. Das strömende Fluid und das poröse Medium sind örtlich im thermischen Gleichgewicht.
    Notes: Abstract In this paper we consider the free convection from a horizontal line source of heat which is embedded in an unbounded porous medium saturated with a fluid at rest under gravity. The convective fluid and the porous medium are in local thermal equilibrium.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 26 (1991), S. 289-298 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Eine Untersuchung über freie Konvektionsströmung in einer rechtwinkligen Ecke, die aus einer horizontalen und vertikalen, halbunendlichen Platte gebildet wird, wurde für ziemlich hohe Werte der Grashofzahl mit der asymptotisch, erwartungstreuen Schätzung durchgeführt. Bei der vertikalen Platte wird die Umgebungstemperatur konstant gehalten und die Horizontale Platte steht unter gleichmäßigem Wärmefluß. Für die Geschwindigkeits-und Temperaturfelder sind gleich gute Verbesserungen höherer Ordnung gefunden worden, wie für die Wärmeübertragung und den Oberflächenreibungskoeffizient. Die gegenseitige Beeinflussung der beiden Grenzschichten, die sich auf der horizontalen und vertikalen Platte bilden, entstand durch eine isotherme Außenströmung. Eigenwerte und ihre darauf bezogenen Eigenfunktionen, die mit der Expansion verbunden sind, wurden ermittelt. Wir sind in der Lage, die Lösung durch eine Approximation hoher Ordnung zu ersetzen und dadurch eine einzige Eigenlösung zu finden. Die numerischen Ergebnisse sind für weite Bereiche der Prandtlzahl, σ erhalten worden. Dargestellt wurden jedoch nur die für σ=0,72 (Luft) und 6,7 (Wasser). Es wurde herausgefunden, daß die Verbesserungen höherer Ordnung für die klassische Grenzschichttheorie sehr bedeutend sind, besonders für die Grashofzahlen der Ordnung 109.
    Notes: Abstract A study of natural convection flow in a right angled corner formed by a semi-infinite vertical plate, which is maintained at the ambient temperature, and a semi-infinite horizontal plate, which is prescribed with a uniform heat flux, is carried out for moderately large values of the Grashof number by the method of matched asymptotic expansions. Higher-order corrections are found for the velocity and temperature fields as well as for the heat transfer and skin friction coefficients. The interaction between the two boundary-layers, which form on the vertical and horizontal plates, takes place through an isothermal outer flow. Eigenvalues and their corresponding eigenfunctions which are associated with the inner expansions have been sought. We are able to continue the solution up to the contribution played by the first eigenvalue and to uniquely find the first eigensolution. Numerical results have been obtained for a wide range of values of the Prandtl number, σ, but the results are only presented for σ=0.72 (air) and 6.7 (water). It is found that higher-order corrections to the classical boundary-layer theory are quite significant even for Grashof numbers of order 109.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 20 (1986), S. 237-241 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung In der Arbeit wird das Problem der freien, inkompressiblen, laminaren und nichtstationären Konvektion über eine halbunendliche waagerechte Platte theoretisch untersucht. Es wird vorausgesetzt, daß die Platte fürt〈0 wärmer als die sie umgebende Flüssigkeit ist und dann im Momentt=0 plötzlich bis auf die Temperatur der Umgebung abgekühlt wird. Es werden drei Lösungen für die Impulsgleichung und die Energiegleichung angegeben, und zwar: (i) eine analytische Lösung für kleine Werte des Zeitparameters, (ii) eine asymptotische analytische Lösung für große Werte des Zeitparameters und (iii) eine numerische Lösung, die sich den beiden analytischen Lösungen anpaßt. Es wird gezeigt, daß sich die numerische Lösung den Lösungen für kleine bzw. große Zeitwerte genau anpaßt. Zum Abschluß wird die Veränderung der Geschwindigkeit, Temperatur, Wandreibung und des Wärmeübergangs an der Platte in Abhängigkeit von der Zeit behandelt.
    Notes: Abstract The problem of unsteady laminar, incompressible free convection above a horizontal semi-infinite flat plate is studied theoretically. It is assumed that for timet〈0 the plate is hotter than its surroundings and at timet=0 the plate is suddenly cooled to the same temperature of its surroundings. Three solutions of the momentum and energy equations are obtained, namely (i) an analytical solution which is valid for small time, (ii) an asymptotic analytical solution which is valid for large time, and (iii) a numerical solution which matches these two limiting analytical solutions. It is found that the numerical solution matches the small and large time solutions accurately. Finally, the variation of the velocity, temperature, skin friction and heat transfer on the plate with time are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 20 (1986), S. 283-289 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wird die Strömung und der Wärmeübergang an einem beheizten, halbunendlichen horizontalen Kreiszylinder betrachtet, der mit konstanter Geschwindigkeit sich in ein poröses Medium bewegt. Dabei wird angenommen, daß die Grashof- und Reynolds-Zahlen groß sind, so daß die Bestimmungsgleichungen von den dreidimensionalen Grenzschichtgleichungen gebildet werden. Es wird ein numerisches Verfahren zur Lösung dieser Gleichungen beschrieben und eine asymptotische Lösung präsentiert, die sowohl in der Nähe als auch in großem Abstand von dem vorderen Ende des Zylinders gültig ist. Der Gültigkeitsbereich dieser asymptotischen Lösungen wird diskutiert und die Ergebnisse werden im Detail mit vollständigen numerischen Lösungen verglichen. Das Problem ist z.B. beim Eindringen von Rohrleitungen in geothermische Reservoire von praktischer Wichtigkeit.
    Notes: Abstract The flow and heat transfer from a heated semi-infinite horizontal circular cylinder which is moving with a constant speed into a porous medium is considered. It is assumed that the Grashof and Reynolds numbers are large so that the governing equations are the three dimensional boundary-layer equations. A numerical procedure for solving these equations is described and the asymptotic solutions which are valid both near and distant from the leading edge of the cylinder are presented. The range of validity of these asymptotic solutions is discussed and the results are compared in detail with the full numerical solution. The problem is of practical importance, for example in the drilling of pipes into a geothermal reservoir.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 22 (1988), S. 239-242 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es werden Grenzschichteinflüsse höherer Ordnung für die freie Konvektionsströmung über schrägen ebenen Platten (sowohl für positive als auch für negative Schräge) bei gleichmäßigem Wärmestrom in einem gesättigten porösen Medium untersucht. Mit Hilfe der Methode der angepaßten asymptotischen Entwicklungen werden drei Terme der inneren und äußeren Entwicklung bestimmt. Es wird gezeigt, daß die erste Eigenfunktion für
    Notes: Abstract Higher-order boundary-layer effects for natural convection flow along inclined flat plates (of both positive and negative inclinations) with a uniform heat flux surface condition in a saturated porous medium are studied. Using the method of matched asymptotic expansions the three terms in inner and outer expansions have been obtained. It is shown that the first eigenfunction for this considered problem coincides with 0(ɛ 2)-term in the inner expansion.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 91 (1992), S. 27-46 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Fluid flow induced by a harmonically oscillating cascade of normal flat plates and square cylinders has been investigated. We assume that the amplitude of the oscillation is small in comparison with the typical length of the body and that the Reynolds number, based on the typical length and speed being the size of the body and the frequency of the oscillation, respectively, is small. First-order solutions have been obtained using both a numerical technique and the series truncation method and the results from these two methods show good agreement. The streaming flow induced by the oscillation has also been investigated by solving the set of coupled perturbation equations numerically.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 99 (1993), S. 135-153 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Numerical solutions are presented for the problem of steady laminar combined convection flows in vertical parallel-plate ducts, with linearly varying wall temperatures. Neglecting streamwise diffusion in the analysis leads to a parabolic set of governing equations. These are solved using a marching technique for an implicit finite-difference scheme with vorticity, streamfunction and temperature as variables. A constant wall temperature is applied after a certain height to mimic downhole conditions in an oil well. Various values of the governing parameter,Gr, are considered, including the forced convection solution,Gr=0, whilstPr is set at a value of unity in order to present the numerical method. As |Gr| increases reverse flow regions appear and these are dealt with using a modification of the standard marching technique. Results are obtained in terms of velocity profiles, local Nusselt numbers, flow average temperatures and friction factors, with particular attention applied to the case where the wall temperature decreases with height.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 44 (1993), S. 53-72 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Flows induced by the small-amplitude and high frequency harmonic oscillations of a cascade of bodies in an unbounded fluid which is otherwise at rest are investigated theoretically. In the theoretical study we separate the flow into inner and outer regions. The flow in the inner region is governed by the Stokes boundary-layer equation. The first-order outer flow is governed by the potential solution which is found by using a conformai mapping technique. The second-order outer flow is governed by the full Navier-Stokes equation and the steady streaming flow has been obtained using a modified central-difference scheme for cascades with square cylinders and flat plates for values of the streaming Reynolds number,R s , up to 70. These results show a complicated flow structure.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 43 (1992), S. 191-206 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract The motion of a two-dimensional bubble which is moving between two parallel plates under the influence of a constant pressure has been investigated using the Boundary Element Method. A free surface location algorithm has been developed so that the profile of the bubble may be predicted over a large range of values of the surface tension. The numerically predicted results are compared with existing experimental data and the results are encouraging.
    Type of Medium: Electronic Resource
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