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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 37 (1986), S. 895-909 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Zusammenfassung In der vorliegenden Arbeit wird die Dispersion einer flüssigen Substanz in einem symmetrischen Kanal studiert, dessen ebene Wände sich in der vertikalen Richtung bewegen. Es zeigt sich, daß die longitudinale Dispersion damit vergrößert wird. Die Flüssigkeit wird als reibungsfrei angenommen. Die Lösung wird in analytischer Form dargestellt und an verschiedenen Bewegungen der Kanalwände angewendet. Die Lösung wurde auch für den achsensymmetrischen Fall erweitert.
    Notes: Abstract The dispersion of a diffusing substance along a channel or pipe is augmented if the channel walls (resp. pipe wall) are moving in the lateral direction. The fluid in the present theoretical investigation is supposed to be inviscid. The longitudinal dispersion enhancement is evaluated analytically and the expressions for various movements of the walls are given in simple formulas.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 57 (1987), S. 73-80 
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Übersicht Ausgehend von den Grundgleichungen der instationären Stromfadentheorie wird die Ausbreitung sinusförmiger Druckpulse in einem geraden Rohr mit Kreisquerschnitt und elastischen Wänden berechnet. Die Verzerrung der Druckpulse hängt in dimensionsloser Form von den Parametern Euler- und Strouhal-Zahl ab. Die Resultate der vorliegenden Arbeit dienen der Korrektur des gemessenen instationären Druckes, wenn der Meßort und die Druckmeßdose mit einem elastischen Schlauch verbunden sind.
    Notes: Summary The present paper describes a nonlinear mathematical model for the pressure-pulse transmission through an elastic straight tube with circular cross-section. The distortion of a sinusoidal pressure pulse in dimensionless form depends on two parameters, the Strouhal number and the Euler number. The analysis is useful to the correction of the errors which enter in the measurement of the dynamic pressure when long elastic tubes connecting the point of measurement and the pressure transducer are used.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 18 (1984), S. 89-103 
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Summary In the present paper a perturbation method is developed in order to study viscous laminar flows through wavy-walled channels. The stream function of the flow is expanded in a series thereby the wall amplitude being the perturbation parameter. The walls of the channel are transformed into parallel straight lines in order to simplify the boundary conditions of the problem on the wall. Flow field and wall-shear stresses are calculated numerically up to the first perturbation order. The position of the beginning separation on the channel walls and the associated critical Reynolds number are determined, as well as the extension of the region of the separated flow. The position of separation and reattachment points are given as functions of Reynolds numbers lying above the critical Reynolds number. The results are discussed and compared with the experimental results of other papers and further theoretical analysis.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 27 (1989), S. 82-88 
    ISSN: 1741-0444
    Keywords: Arterial blood flow ; Initially stressed anisotropic elastic tube ; Pulsating flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A mathematical model for pulsating flow of a viscous incompressible fluid in an initially stressed elastic tube with anisotropic structure is developed and an analysis of the propagation of pressure waves is presented. The theoretical model can be applied to the study of blood flow in arteries, and its solution leads to a dispersion equation relating wave number with frequency and the rheological parameters of the wall. Determination of fluid velocities and displacement components is obtained.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 41 (1981), S. 185-196 
    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
    Description / Table of Contents: Summary Physiological flow features can be modelled by elastic and non-elastic elements [1], [2], [3]. Pulsatile flow can be generated when a tube-valve is applied to the steady adjustable volume-flow. The velocities were measured in the centerline of the tube by hot-film-probes. In this paper the valve action in connection with the generated pulsatile flow is investigated theoretically. Thereby it proves to be necessary to analyse separately the opening and the closing phase of the tube valve. In particular the velocity distribution versus time is considered in the case of the sudden opening of the valve, thereby the previous data obtained experimentally are compared with the theoretical results. These results then also could be used to determine the elastic portion of the model of circulation or of the Young's modulus of the elastic tube element.
    Notes: Zusammenfassung In einer experimentellen Strömungs-Anordnung, bestehend aus nichtelastischen und elastischen Elementen, [1], [2], [3], können physiologische Geschwindigkeitsverläufe nachgebildet werden. Aus dem regulierbaren stationären Volumenstrom kann mit einem pulsierenden Schlauchventil ein pulsierender Volumenstrom erzeugt werden. Der Geschwindigkeitsverlauf an der Mittellinie des Rohres wurde mit Heißfilmsonden gemessen. Im folgenden wird der Zusammenhang von Ventilaktion und erzeugter Strömung theoretisch untersucht. Dabei ist eine gesonderte Analyse der Öffnungs-und der Schließphase des Schlauchventils wesentlich erforderlich. Im besonderen wird der Geschwindigkeitsverlauf beim plötzlichen Öffnen betrachtet und dabei werden die früher erhaltenen experimentellen Daten den theoretischen Ergebnissen gegenübergestellt. Diese Ergebnisse könnten dann auch für die Abschätzung des elastischen Anteils der Elemente im Kreislaufmodell oder des Elastizitätsmoduls des elastischen Rohr-Elementes herangezogen werden.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 61 (1986), S. 109-115 
    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 In the present paper a perturbation method is developed in order to study viscous, laminar flow over a small amplitude wavy solid boundary. The wall is transformed into a straight solid boundary in order to simplify the use of boundary conditions of the problem on the wall. The flow field is calculated numerically up to first perturbation order. separation of the flow is included.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 16 (1993), S. 759-775 
    ISSN: 0271-2091
    Keywords: Euler/NAVIER-STOKES equations ; Hypersonic flows ; Real gas ; Upwind scheme ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A study of viscous and inviscid hypersonic flows using generalized upwind methods is presented. A new family of hybrid flux-splitting methods is examined for hypersonic flows. The hybrid method is constructed by the superposition of the flux-vector-splitting (FVS) method and second-order artificial dissipation in the regions of strong shock waves. The conservative variables on the cell faces are calculated by an upwind extrapolation scheme to third-order accuracy. A second-order-accurate scheme is used for the discretization of the viscous terms. The solution of the system of equations is achieved by an implicit unfactored method. In order to reduce the computational time, a local adaptive mesh solution (LAMS) method is proposed. The LAMS method combines the mesh-sequencing technique and local solution of the equations. The local solution of either the Euler or the NAVIER-STOKES equations is applied for the region of the flow field where numerical disturbances die out slowly. Validation of the Euler and NAVIER-STOKES codes is obtained for hypersonic flows around blunt bodies. Real gas effects are introduced via a generalized equation of state.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 25 (1997), S. 523-545 
    ISSN: 0271-2091
    Keywords: incompressible Navier-Stokes equations ; flux-vector-splitting method ; artificial compressibility ; upwind schemes ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An implicit, upwind arithmetic scheme that is efficient for the solution of laminar, steady, incompressible, two-dimensional flow fields in a generalised co-ordinate system is presented in this paper. The developed algorithm is based on the extended flux-vector-splitting (FVS) method for solving incompressible flow fields. As in the case of compressible flows, the FVS method consists of the decomposition of the convective fluxes into positive and negative parts that transmit information from the upstream and downstream flow field respectively. The extension of this method to the solution of incompressible flows is achieved by the method of artificial compressibility, whereby an artificial time derivative of the pressure is added to the continuity equation. In this way the incompressible equations take on a hyperbolic character with pseudopressure waves propagating with finite speed. In such problems the ‘information’ inside the field is transmitted along its characteristic curves. In this sense, we can use upwind schemes to represent the finite volume scheme of the problem's governing equations. For the representation of the problem variables at the cell faces, upwind schemes up to third order of accuracy are used, while for the development of a time-iterative procedure a first-order-accurate Euler backward-time difference scheme is used and a second-order central differencing for the shear stresses is presented. The discretized Navier-Stokes equations are solved by an implicit unfactored method using Newton iterations and Gauss-Siedel relaxation. To validate the derived arithmetical results against experimental data and other numerical solutions, various laminar flows with known behaviour from the literature are examined. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 711-726 
    ISSN: 0271-2091
    Keywords: Euler equations ; Upwind methods ; Real gases ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A formulation of an implicit characteristic-flux-averaging method for the unsteady Euler equations with real gas effects is presented. Incorporation of a real gas into a general equation of state is achieved by considering the pressure as a function of density and specific internal energy. The Ricmann solver as well as the flux-split algorithm are modified by introducing the pressure derivatives with respect to density and internal energy. Expressions for calculating the values of the flow variables for a real gas at the cell faces are derived. The Jacobian matrices and the eigenvectors are defined for a general equation of state. The solution of the system of equations is obtained by using a mesh-sequencing method for acceleration of the convergence. Finally, a test case for a simple form of equation of state displays the differences from the corresponding solution for an ideal gas.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 14 (1992), S. 1391-1405 
    ISSN: 0271-2091
    Keywords: Artificial dissipation schemes ; Central difference schemes ; Compressible flow ; Euler equations ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The influence of artificial dissipation schemes on the accuracy and stability of the numerical solution of compressible flow is extensively examined. Using an implicit central difference factored scheme, an improved form of artificial dissipation is introduced which highly reduces the errors due to numerical viscosity. A function of the local Mach number is used to scale the amount of numerical damping added into the solution according to the character of the flow in several flow regimes. The resulting scheme is validated through several inviscid flow test cases.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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