Stability of miscible fluid displacement in a porous medium

Summary The stability of miscible fluid displacement through porous media has been investigated when concentration induced density and viscosity gradients are present. The dependence of Rayleigh's number on the horizontal planform of cellular motion is established and it is shown that the Rayleigh and wave numbers interact in a nonlinear fashion and hence have to be treated as two independent parameters in the analysis of stability process.Übersicht Untersucht wird die Stabilität der Bewegung mischbarer Flüssigkeiten durch ein poröses Medium bei konzentrationsbedingten Dichte- und Viskositätsgradienten. Der Zusammenhang zwischen der Rayleigh-Zahl und der horizontalen Planheit der Zellbewegung wird aufgezeigt und nachgewiesen, daß die Rayleigh-und Wellenzahlen sich nichtlinear beeinflussen und folglich als zwei unabhängige Parameter der Stabilitäts-analyse zu betrachten sind.

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Stabilität der verschiebung mischbarer flüssigkeiten in einem porösen medium

     

Nonlinear static and dynamic analysis for laminated,annular, spherical caps of moderate thickness

Based on Timoshenko-Mindlin kinematic hypothesis, the shallow shell theory is extended to include the transverse shear deformation for the nonlinear axisymmetric dynamic analysis of the symmetric cross-ply shallow spherical shell. Using the orthogonal point collocation method and the Newmark scheme, an iterative solution is formulated. The numerical results for the nonlinear static and dynamic responses and dynamic buckling of these shallow spherical shells with circular holes under uniformly distributed static or dynamic normal impact loads are presented and compared with available data.     

Coherent and random structure in reacting jets

Combustion rate and stability are strongly related to the interaction of fluid dynamics with the combustion process in reactive flow systems. The ability to control the combustion depends on the understanding of this interaction. This paper describes the use of the Planar Laser Induced Fluorescence (PLIF) technique to get insight into these processes, by looking at the coherent and random structures of a combusting jet. The coherent structures educed by phase-locked averaging are significantly different from instantaneous pictures, which are highly three dimensional. The PLIF images clarify the relationship between the large-scale structures and the generation of small-scale turbulence.     

Friction factor and holdup studies for lubricated pipelining—I. Experiments and correlations

Results from new experiments on the lubricated pipelining of emulsified waxy crude oil and No. 6 fuel oil are presented and compared with other sources of literature. A correlation formula which estimates the holdup fraction is introduced and evaluated for all available experimental data. A simple theory is given which is based on the concentric core-annular flow model and leads to a Reynolds number and friction factor which reduce a large body of experimental data onto one curve; with the best results in the high Reynolds number flow regime.     

Strain rate sensitivity of flow stress at low temperatures in 304n stainless steel

Strain rate and temperature effects on the flow stress of 304N stainless steel were investigated using data obtained from torsion tests on thin-walled tubular specimens, at given strain rates of between 10⁻³ and 10⁻¹ with temperatures ranging from 83 to 296 K. Initially, the apparent strain rate sensitivity of the flow stress, obtained at test temperatures of 83, 153, 213, and 296 K, was examined. The strain dependence and the strain rate dependence of the mechanical threshold stress (the flow stress at O K) at strains less than 0.1 and at strain rates of 2.4 × 10⁻³ and 8.3 × 10² s⁻¹, is also discussed. It was concluded from the experimental results that the mechanical threshold stress depends not only on the strain but also on the strain rate.     

Three-dimensional effects in interfacial crack propagation

The paper describes the use of crack-opening interferometry for examining the variation in normal crack-opening displacements (NCOD) along the front of an interfacial crack in an edge-cracked bimaterial strip under biaxial loading. For the glass/epoxy combination considered here, the crack front was concave in the direction of crack growth, in contrast to previous observations with a glass/polyurethane/glass sandwich specimen and cracks in homogeneous materials. The NCOD were greatest in the interior of the specimen for all mode-mixes considered and the exponents in a power-law fit of NCOD versus distance from the crack front decreased towards the free surface. The exponents varied with mode-mix, suggesting that interfacial crack-front geometries could be similarly affected.     

Laser diffraction methods for high-temperature strain measurements

Optical methods, utilizing the interference fringes produced by diffraction of a laser light beam passing through a narrow slit, have been investigated for strain measurements at high temperatures above 1000°C. Two methods are reviewed, one suitable for dynamic loading conditions and the other for slow rate and static loading conditions. The basic principles of the methods, new instrumentation, and new measurement techniques are described. Experimental verification of the basic optical theory, system calibration, results of cross calibrations with foil strain gage, and sample applications at high temperatures are presented. Test results show that both methods are capable of performing accurate and reliable strain measurements at high temperatures.Paper was presented at the 1989 SEM Spring Conference on Experimental Mechanics held in Cambridge, MA on May 28–June 1.     

A screw dislocation near an elliptic hole in non-local elasticity

Summary The solutions are given for the stress field and elastic energy of a screw dislocation near an elliptic hole in non-local elasticity by a conformal mapping technique. The numerical results are discussed for the stress along thex-axis. Allowing one axis of the ellipse to dwindle to zero, the solution of the finite length crack is obtained.

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Schraubenversetzung neben einem elliptischen Loch bei nichtlokaler Elastizität

Übersicht Durch eine konforme Abbildungstechnik werden die Lösungen für das Spannungsfeld und die elastische Energie der Schraubenversetzung neben einem elliptischen Loch in nichtlokaler Elastizität gegeben. Die numerischen Ergebnisse werden für die Spannung entlang derx-Achse diskutiert. Läßt man eine Ellipsenachse gegen Null gehen, so gewinnt man die Lösung für den Riß endlicher Länge.

     

A steam-soak production model for thick gravity drainage petroleum reservoirs

Summary This paper deals with the production performance for the steam-soak process as applied to a reservoir where oil is produced by gravity drainage. An improved analytical temperature profile which is simple, less time consuming and comparable to the exact solution is used to compute the viscosity variation inside the reservoir. Based on this temperature profile the continuity equation is solved by finite difference technique to find the oil height as a function of radius and time which in turn gives the flow rate and cumulative oil production. Comparison of the developed model with available field data shows that the model gives better prediction of steam-soak oil recovery than other comparable methods.

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Ein Modell zur Ausbeute von Rohölfeldern durch Schwerkraftsickerung bei zyklischer Dampfinjektion

Übersicht Behandelt wird das Förderverhalten eines Rohölspeichers bei Dampfinjektion und Schwerkraftsickerströmung. Zur Berechnung der Viskositätsverteilung im Reservoir wird ein vereinfachtes Temperaturfeld, welches das wahre annähert, benutzt. Mit dieser Temperaturverteilung wird die Kontinuitätsgleichung nach der Finite-Differenzen-Methode gelöst und die Ölstandshöhe als Funktion von Radius und Zeit bestimmt. Daraus ergibt sich der Volumenstrom und die kumulierte Fördermenge. Ein Vergleich des hier entwickelten Modells mit Daten eines Ölfeldes zeigt, daß es bessere Vorhersagen liefert als vergleichbare Methoden.

     

Turbulent film boiling from a vertical non-isothermal surface

The turbulent film boiling from a vertical non-isothermal surface is formulated with due consideration to thermal radiation from its lateral face. It is observed that the application of Reynolds analogy together with thermal conduction in the test surface has yielded a conjugate solution from which the case of an isothermal condition can be generated as a special case. The analysis has further paved the way in establishing a functional relation between the Nusselt numberNu, radiation parameterN _R , fin parameterM, temperature ratio termT _s /(T _w,0?T _s ), and a product of characteristic modified Grashof, Prandtl and superheating parameter defined as (Gr ² Pr S). In a fully developed turbulent film boiling i.e., modified Grashof number being greater than 10¹⁰, the temperature ratio term accounts for the non-linearities arising due to the inclusion of radiation from the lateral face of the fin. The results are in good agreement with experimental data over a wide range of system conditions.