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1.
Knowles' representation theorem for harmonically time-dependent free surface waves on a homogeneous, isotropic elastic half-space is extended to include harmonically time-dependent free processes for thermoelastic surface waves in generalized thermoelasticity of Lord and Shulman and of Green and Lindsay.r , , r , , .This work was done when author was unemployed.  相似文献   

2.
An experimental study was done to quantify the effects of a variety of background particulates on the delayed laminar-turbulent transition of a thermally stabilized boundary layer in water. A Laser-Doppler Velocimeter system was used to measure the location of boundary layer transition on a 50 mm diameter, 9:1 fineness ratio ellipsoid. The ellipsoid had a 0.15 m RMS surface finish. Boundary layer transition locations were determined for length Reynolds numbers ranging from 3.0 × 106 to 7.5 × 106. The ellipsoid was tested in three different heating conditions in water seeded with particles of four distinct size ranges. For each level of boundary layer heating, measurements of transition were made for clean water and subsequently, water seeded with 12.5 m, 38.9 m, 85.5 m and 123.2 m particles, alternately. The three surface heating conditions tested were no heating, T = 10°C and T = 15°C where T is the difference between the inlet model heating water temperature, T i, and free stream water temperature, T . The effects of particle concentration were studied for 85.5 m and 123.2 m particulates.The results of the study can be summarized as follows. The 12.5 m and 38.9 m particles has no measurable effect on transition for any of the test conditions. However, transition was significantly affected by the 85.5 m and 123.2 m particles. Above a length Reynolds number of 4 × 106 the boundary layer transition location moved forward on the body due to the effect of the 85.5 m particles for all heating conditions. The largest percentage changes in transition location from clean water, were observed for 85.5 m particles seeded water.Transition measurements made with varied concentrations of background particulates indicated that the effect of the 85.5 m particles on the transition of the model reached a plateau between 2.65 particulates/ml concentration and 4.2 particles/ml. Measurements made with 123.3 m particles at concentrations up to 0.3 part/ml indicated no similar plateau.  相似文献   

3.
The stability of the steady self-similar flow in the boundary layer on a rotating disk of infinite radius with corotation of the surrounding fluid is analyzed by the normal mode method. The spectral problem for infinitesimal three-dimensional disturbances is solved by a collocation method with expansion of the amplitude functions in Chebyshev polynomials. It is established that for all values of the parameter 0, equal to the ratio of the angular velocities of the fluid and the disk, the lower critical Reynolds number is determined byA-type, waves, whose development is governed by the parallel instability mechanism typical of an Ekman layer. TheB-type instability, associated with the presence of an inflection point on the velocity profile, disappears when 4. The neutral surfaces are calculated for Karman flow (=0) and Bödewadt flow (). It is found that in Karman flowA-type waves may grow at values of the Reynolds number several times smaller than the critical Reynolds number for spiral vortices. The results of the analysis are compared with the available experimental data.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.5, pp. 69–77, September–October, 1992.  相似文献   

4.
A study is presented of the flow of stability of a Grad-model liquid layer [1, 2] flowing over an inclined plane under the influence of the gravity force.It is assumed that at every point of the considered material continuum, along with the conventional velocity vector v, there is defined an angular velocity vector , the internal moment stresses are negligibly small, and in the general case the force stress tensor kj is asymmetric. The model is characterized by the usual Newtonian viscosity , the Newtonian rolling viscosity r, and the relaxation time = J/4 r, where J is a scalar constant of the medium with dimensions of moment of inertia per unit mass, is the density. It is assumed that the medium is incompressible, the coefficients , r, J are constant [2].The exact solution of the equations of motion, corresponding to flow of a layer with a plane surface, coincides with the solution of the Navier-Stokes equations in the case of flow of a layer of Newtonian fluid. The equations for three-dimensional periodic disturbances differ considerably from the corresponding equations for the problem of the flow stability of a layer of a Newtonian medium. It is shown that the Squire theorem is valid for parallel flows of a Grad liquid.The flow stability of the layer with respect to long-wave disturbances is studied using the method of sequential approximations suggested in [3, 4].  相似文献   

5.
Summary A new and very general expression is proposed for correlation of data for the effective viscosity of pseudoplastic and dilatant fluids as a function of the shear stress. Most of the models which have been proposed previously are shown to be special cases of this expression. A straightforward procedure is outlined for evaluation of the arbitrary constants.
Zusammenfassung Eine neue und sehr allgemeine Formel wird für die Korrelation der Werte der effektiven Viskosität von strukturviskosen und dilatanten Flüssigkeiten in Abhängigkeit von der Schubspannung vorgeschlagen. Die meisten schon früher vorgeschlagenen Methoden werden hier als Spezialfälle dieser Gleichung gezeigt. Ein einfaches Verfahren für die Auswertung der willkürlichen Konstanten wird beschrieben.

Nomenclature b arbitrary constant inSisko model (eq. [5]) - n arbitrary exponent in eq. [1] - x independent variable - y(x) dependent variable - y 0(x) limiting behavior of dependent variable asx 0 - y(x) limiting behavior of dependent variable asx - z original dependent variable - arbitrary constant inSisko model (eq. [5]) andBird-Sisko model (eq. [6]) - arbitrary exponent in eqs. [2] and [8] - effective viscosity = shear stress/rate of shear - A effective viscosity at = A - B empirical constant in eqs. [2] and [8] - 0 limiting value of effective viscosity as 0 - 0() limiting behavior of effective viscosity as 0 - limiting value of effective viscosity as - () limiting behavior of effective viscosity as - rate of shear - arbitrary constant inBird-Sisko model (eq.[6]) - shear stress - A arbitrary constant in eqs. [2] and [8] - 0 shear stress at inBingham model - 1/2 shear stress at = ( 0 + )/2 With 8 figures  相似文献   

6.
Two-phase flow in stratified porous media is a problem of central importance in the study of oil recovery processes. In general, these flows are parallel to the stratifications, and it is this type of flow that we have investigated experimentally and theoretically in this study. The experiments were performed with a two-layer model of a stratified porous medium. The individual strata were composed of Aerolith-10, an artificial: sintered porous medium, and Berea sandstone, a natural porous medium reputed to be relatively homogeneous. Waterflooding experiments were performed in which the saturation field was measured by gamma-ray absorption. Data were obtained at 150 points distributed evenly over a flow domain of 0.1 × 0.6 m. The slabs of Aerolith-10 and Berea sandstone were of equal thickness, i.e. 5 centimeters thick. An intensive experimental study was carried out in order to accurately characterize the individual strata; however, this effort was hampered by both local heterogeneities and large-scale heterogeneities.The theoretical analysis of the waterflooding experiments was based on the method of large-scale averaging and the large-scale closure problem. The latter provides a precise method of discussing the crossflow phenomena, and it illustrates exactly how the crossflow influences the theoretical prediction of the large-scale permeability tensor. The theoretical analysis was restricted to the quasi-static theory of Quintard and Whitaker (1988), however, the dynamic effects described in Part I (Quintard and Whitaker 1990a) are discussed in terms of their influence on the crossflow.Roman Letters A interfacial area between the -region and the -region contained within V, m2 - a vector that maps onto , m - b vector that maps onto , m - b vector that maps onto , m - B second order tensor that maps onto , m2 - C second order tensor that maps onto , m2 - E energy of the gamma emitter, keV - f fractional flow of the -phase - g gravitational vector, m/s2 - h characteristic length of the large-scale averaging volume, m - H height of the stratified porous medium , m - i unit base vector in the x-direction - K local volume-averaged single-phase permeability, m2 - K - {K}, large-scale spatial deviation permeability - { K} large-scale volume-averaged single-phase permeability, m2 - K * large-scale single-phase permeability, m2 - K ** equivalent large-scale single-phase permeability, m2 - K local volume-averaged -phase permeability in the -region, m2 - K local volume-averaged -phase permeability in the -region, m2 - K - {K } , large-scale spatial deviation for the -phase permeability, m2 - K * large-scale permeability for the -phase, m2 - l thickness of the porous medium, m - l characteristic length for the -region, m - l characteristic length for the -region, m - L length of the experimental porous medium, m - characteristic length for large-scale averaged quantities, m - n outward unit normal vector for the -region - n outward unit normal vector for the -region - n unit normal vector pointing from the -region toward the -region (n = - n ) - N number of photons - p pressure in the -phase, N/m2 - p 0 reference pressure in the -phase, N/m2 - local volume-averaged intrinsic phase average pressure in the -phase, N/m2 - large-scale volume-averaged pressure of the -phase, N/m2 - large-scale intrinsic phase average pressure in the capillary region of the -phase, N/m2 - - , large-scale spatial deviation for the -phase pressure, N/m2 - pc , capillary pressure, N/m2 - p c capillary pressure in the -region, N/m2 - p capillary pressure in the -region, N/m2 - {p c } c large-scale capillary pressure, N/m2 - q -phase velocity at the entrance of the porous medium, m/s - q -phase velocity at the entrance of the porous medium, m/s - Swi irreducible water saturation - S /, local volume-averaged saturation for the -phase - S i initial saturation for the -phase - S r residual saturation for the -phase - S * { }*/}*, large-scale average saturation for the -phase - S saturation for the -phase in the -region - S saturation for the -phase in the -region - t time, s - v -phase velocity vector, m/s - v local volume-averaged phase average velocity for the -phase, m/s - {v } large-scale averaged velocity for the -phase, m/s - v local volume-averaged phase average velocity for the -phase in the -region, m/s - v local volume-averaged phase average velocity for the -phase in the -region, m/s - v -{v } , large-scale spatial deviation for the -phase velocity, m/s - v -{v } , large-scale spatial deviation for the -phase velocity in the -region, m/s - v -{v } , large-scale spatial deviation for the -phase velocity in the -region, m/s - V large-scale averaging volume, m3 - y position vector relative to the centroid of the large-scale averaging volume, m - {y}c large-scale average of y over the capillary region, m Greek Letters local porosity - local porosity in the -region - local porosity in the -region - local volume fraction for the -phase - local volume fraction for the -phase in the -region - local volume fraction for the -phase in the -region - {}* { }*+{ }*, large-scale spatial average volume fraction - { }* large-scale spatial average volume fraction for the -phase - mass density of the -phase, kg/m3 - mass density of the -phase, kg/m3 - viscosity of the -phase, N s/m2 - viscosity of the -phase, Ns/m2 - V /V , volume fraction of the -region ( + =1) - V /V , volume fraction of the -region ( + =1) - attenuation coefficient to gamma-rays, m-1 - -   相似文献   

7.
Zusammenfassung Zur Berechnung der dynamischen Idealviskosität Ideal (T) und der Idealwärmeleitfähigkeit ideal (T) benötigt man die kritische TemperaturT kr, das kritische spezifische Volum kr, die MolmasseM, den kritischen Parameter kr und die molare isochore WärmekapazitätC v(T). Sowohl das theoretisch, als auch das empirisch abgeleitete erweiterte Korrespondenzgesetz ergeben eine für praktische Zwecke ausreichende Genauigkeit für die Meßwertwiedergabe, die bei den assoziierenden Stoffen und den Quantenstoffen jedoch geringer ist als bei den Normalstoffen.
The extended correspondence law for the ideal dynamic viscosity and the ideal thermal conductivity of pure substances
For the calculation of the ideal dynamic viscosity Ideal (T) and the ideal thermal conductivity ideal (T) the critical temperatureT kr, the critical specific volumev kr, the molecular massM, the critical parameter kr, and the molar isochoric heat capacityC v(T) is needed. Not only the theoretically determined but also the empirically determined extended correspondence law gives for practical use a good representation of the measured data, which for the associating substances and the quantum substances is not so good as for the normal substances.
  相似文献   

8.
S. Kase 《Rheologica Acta》1982,21(2):210-211
The general integral of the very simple equation 21/n/() was found to describe the cross sectional area of filaments of isothermal power law fluids while in transient stretching where is time and is the initial location of fluid molecules at time = 0 given as the distance from a reference point fixed in space. Any such stretching transient given as a solution of the above equation is physically realizable subject to the restrictions > 0 and/ < 0.  相似文献   

9.
Hot-wire measurements have been carried out in a turbulent boundary layer subjected to concentrated suction applied through a short porous wall strip with a view to examine the effect suction can have on the anisotropy of the Reynolds stress tensor. The departure of the Reynolds stress ratios from their corresponding values in the undisturbed flow is increased as the normalised suction rate increases. It is argued that the alteration to the Reynolds stress containing motion reflects a cigar to pancake change in the shape of the structures near the wall.  相似文献   

10.
We consider an asymptotic theory of the turbulent boundary layer [1,2]. In this paper we make an attempt to further develop the mathematical aspects of this theory. We demonstrate the features of this theory by applying it to a problem which is close to the so-called equilibrium turbulent boundary layer with a pressure gradient and blowing.Notation x, y coordinates, parallel and perpendicular to the wall - u velocity component in the x direction - p, ',v pressure, density, and kinematic viscosity coefficient - l' scale of turbulence - tangential stress - u speed at the outer edge of the boundary layer - thickness of the boundary layer - * displacement thickness - ** momentum loss thickness - Cf coefficient of friction - R Reynolds number Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 86–95, September–October, 1971.The author thanks S. S. Kutateladze, A. I. Leont'ev, and G. V. Aronovich for their interest in this effort.  相似文献   

11.
The problem of nonsteady-state evaporation or growth of a radiating drop with uniformly distributed internal heat sources is considered. The Reynolds R=ua/v 1 and Peclet PD= ua/D 1 numbers are assumed to be small (a is the radius of the drop, u the velocity of its relative motion, andv, D, the coefficients of viscosity, diffusion and thermal diffusivity of the vapor-gas medium). This enables the convective transfer of vapor and heat to be neglected, and the concentration and temperature fields to be regarded as spherically symmetric [1]. In view of the fact that the density of saturated vapor is less than the density of liquid the convective flow caused by the change in radius of the drop is not taken into account [2]. It has already been shown [3,4], that for r (, r are the coefficients of molecular and radiative thermal conductivity) there exists a bounded region ryo (1/) /r ( is the absorption coefficient for radiation in the gas), in which the effect of radiation on the temperature relaxation of the vapor-gas medium is negligible. If the conditiona (1/) /r is satisfied, then the temperature at the outer boundary of this region will be practically the same as the temperature at infinity T=T. This means that terms in the energy equation connected with energy transferred by radiation can be neglected. It is assumed that the free path of molecules in the gas is less than the radius of the drop, and so concentration and temperature discontinuities close to the surface of the drop can be neglected [2].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 11, No. 1, pp. 78–87, January–February, 1970.The authors are grateful to V. G. Levich for discussing the results of the paper.  相似文献   

12.
By employing the four shafts balance concept paper [1] has reported a balance regime for the second order reciprocal inertia forces on the V-type eight cylinder internal combustion engines with a plane crankshaft. Thereafter, paper [2] has acquired a two-shafts balance regime, but through a rather tedious roudabout degenerating manipulation. The present article has, but starting out directly from the two-shafts balance concept, successfully acquired the same results as those in paper [2]. In addition, we propose, herein, a third balance system which might be, in general, called the slipper balance regime.  相似文献   

13.
Calculations of the flow of the mixture 0.94 CO2+0.05 N2+0.01 Ar past the forward portion of segmentai bodies are presented. The temperature, pressure, and concentration distributions are given as a function of the pressure ahead of the shock wave and the body velocity. Analysis of the concentration distribution makes it possible to formulate a simplified model for the chemical reaction kinetics in the shock layer that reflects the primary flow characteristics. The density distributions are used to verify the validity of the binary similarity law throughout the shock layer region calculated.The flow of a CO2+N2+Ar gas mixture of varying composition past a spherical nose was examined in [1]. The basic flow properties in the shock layer were studied, particularly flow dependence on the free-stream CO2 and N2 concentration.New revised data on the properties of the Venusian atmosphere have appeared in the literature [2, 3] One is the dominant CO2 concentration. This finding permits more rigorous formulation of the problem of blunt body motion in the Venus atmosphere, and attention can be concentrated on revising the CO2 thermodynamic and kinetic properties that must be used in the calculation.The problem of supersonic nonequilibrium flow past a blunt body is solved within the framework of the problem formulation of [4].Notation V body velocity - shock wave standoff - universal gas constant - ratio of frozen specific heats - hRt/m enthalpy per unit mass undisturbed stream P pressure - density - T temperature - m molecular weight - cp specific heat at constant pressure - (X) concentration of component X (number of particles in unit mass) - R body radius of curvature at the stagnation point - j rate of j-th chemical reaction shock layer P V 2 pressure - density - TT temperature - mm molecular weight Translated from Izv. AN SSSR. Mekhanika Zhidkosti i Gaza, Vol. 5, No. 2, pp. 67–72, March–April, 1970.The author thanks V. P. Stulov for guidance in this study.  相似文献   

14.
The complex fluid-dynamic aspects of a turbulent recirculating flow in a cavity with axial throughflow, and a rotating wall, were investigated by adopting a simple procedure for evaluating the turbulent stresses. The flow field was divided into two regions, a core and a wall region respectively. A wall function was adopted in the zones near to the solid boundaries, while a constant eddy diffusivity was assumed, in the core, following the indications of computed heat transfer coefficients in comparison with existing experimental data. The distributions of the stream function and of the tangential velocity are presented for a range of the rotational Reynolds number of the rotating wall and of the Reynolds number of the throughflow.
Turbulente Rezirkulationsströmung in einem Hohlraum
Zusammenfassung Die komplizierten fluiddynamischen Aspekte einer turbulenten Rezirkulationsströmung in einem Hohlraum mit axialem Durchfluß und einer rotierenden Wand werden unter Verwendung einer vereinfachten Methode zur Berechnung der turbulenten Spannungen betrachtet. Das Strömungsfeld wird in einen Kern und einen Wandbereich aufgeteilt. Für die wandnahen Zonen wird eine Wandfunktion angenommen, während im Kern mit konstanter Wirbeldiffusivität gerechnet wird, was durch den Vergleich berechneter mit gemessenen Wärmeübergangskoeffizienten gerechtfertigt erscheint. Verteilungen der Stromfunktion und der tangentialen Geschwindigkeit sind für einen bestimmten Bereich der Reynoldszahlen für die Wandrotation und der für den Durchfluß angegeben.

Nomenclature L axial length of enclosure - P dimensionless pressure, p*2 - p static pressure - R dimensionless radial coordinate, r/r* - r radial coordinate - r* reference length, equal to rO for enclosure - ri radii of inlet and exit apertures - Re Reynolds number, v*r*/ - Rei pipe Reynolds number, ¯vzi(2ri)/ - Ret turbulent Reynolds number, Re(/) - Re rotational Reynolds number, r 0 2 / - t dimensionless time,t/(r*/v*) - t time - Vr, V, Vz dimensionless velocity components, Vr/v*, v, vz/v* - vi turbulent fluctuation of the i-component of velocity - vr, v, vz velocity components - v* reference velocity, equal to ¯vzi for enclosure - X coordinate along a wall, x/r* - Y coordinate normal to a wall, y/r* - Z dimensionless axial coordinate, z/r* - z axial coordinate - eddy diffusivity for momentum - dynamic viscosity - kinematic viscosity - density - shear stress - dimensionless shear stress, /v*2 - dimensionless stream function, /r*2v*2 - stream function - angular velocity - tangential vorticity component - ()eff effective - ()l laminar - ()t turbulent - mean over the time  相似文献   

15.
An effective numerical procedure, based on the Galerkin method, for finding solutions of the stationary traveling wave type in the complete formulation is proposed for the case of viscous liquid films. Examples of a viscous film flowing freely down a vertical surface have been calculated. The calculations have been made for various values of the dimensionless surface tension , including =0. The method makes it possible to predict a number of bifurcations that occur as decreases. The existence of numerous families of stationary traveling waves when 1 was demonstrated in [6]. The present study shows that as 1 all but one of these families of wave solutions disappear. The shape of the periodic and solitary waves and the pressure distribution in the film are found for various . When =0 and the wave number is fairly small, the periodic solution has a singularity, as predicted in [14]: at the crest of the wave a corner point appears; the angle between the tangents at this point =140–150. The method proposed can be used to calculate other wavy film flows.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 94–100, May–June, 1990.  相似文献   

16.
LDA measurements of the mean velocity in a low Reynolds number turbulent boundary layer allow a direct estimate of the friction velocity U from the value of /y at the wall. The trend of the Reynolds number dependence of / is similar to the direct numerical simulations of Spalart (1988).  相似文献   

17.
The physics and biology that found psychoanalysis account for discontinuous experience only in the presence of nonmeasurable, metaphysical operators; these include the ego and its subsystems as well as biological experience inherited through Lamarckian principles. Complex, self-organizing systems, however, can link biology to experience without metaphysics. They can also account for psychoanalytically relevant behaviors without appealing to stable internal representations. These behaviors include what W. R. Bion called transformation in O and its corollary, the appearance of the selected fact. By dimensionally exploding the double-headed arrow that he used to link the states Ps and D in his model for thinking (Ps D), we can generate a space that is, at once, psychoanalytically imaginal and dynamically coadapting. Isomorphic to D. W. Winnicott's transitional space, it is self-organizing. It is describable according to dynamics formulated by W J. Freeman, S. Kauffman and C. Langton and it can generate instantaneous conscious contents by way of a selective process analogous to spatio-temporal binding. As a whole, this model supports a clinical stance advanced by D. W. Winnicott as play, within transitional space.  相似文献   

18.
A computerized infrared (IR) scanning radiometer is employed to characterize the boundary layer development over a model wing, having a Göttingen 797 cross-section, by measuring the temperature distribution over its heated surface. The Reynolds analogy is used to relate heat transfer measurements to skin friction. The results show that IR thermography is capable of rapidly detecting location and extent of transition and separation regions of the boundary layer over the whole surface of the tested model wing. Thus, the IR technique appears to be a suitable and effective diagnostic tool for aerodynamic research in wind tunnels.List of symbols c airfoil chord - c f local skin friction coefficient = 2/( V 2) - c p specific heat coefficient at constant pressure - h local convective heat transfer coefficient - Nu Nusselt number = h x/ - Nu c Nusselt number based on airfoil chord = h c/ - Pr Prandtl number c p / - Q j wall heat flux due to Joule heating - Q l heat flux loss - Re Reynolds number V x/ - Re c Reynolds number based on airfoil chord = V c/ - St Stanton number = h/c p V - T w wall temperature - T aw adiabatic wall temperature - V velocity of the free stream - x chordwise spatial coordinate - angle of attack - thermal conductivity coefficient - dynamic viscosity coefficient - mass density - wall shear stress  相似文献   

19.
Based on the complex viscosity model various steady-state and transient material functions have been completed. The model is investigated in terms of a corotational frame reference. Also, BKZ-type integral constitutive equations have been studied. Some relations between material functions have been derived. C –1 Finger tensor - F[], (F –1[]) Fourier (inverse) transform - rate of deformation tensor in corotating frame - h(I, II) Wagner's damping function - J (x) Bessel function - m parameter inh (I, II) - m(s) memory function - m k, nk integers (powers in complex viscosity model) - P principal value of the integral - parameter in the complex viscosity model - rate of deformation tensor - shear rates - [], [] incomplete gamma function - (a) gamma function - steady-shear viscosity - * complex viscosity - , real and imaginary parts of * - 0 zero shear viscosity - +, 1 + stress growth functions - , 1 - stress relaxation functions - (s) relaxation modulus - 1(s) primary normal-stress coefficient - ø(a, b; z) degenerate hypergeometric function - 1, 2 time constants (parameters of *) - frequency - extra stress tensor  相似文献   

20.
The action of a highfrequency electromagnetic field on a dilute suspension of spherical particles with a constant dipole moment is studied using statistical mechanics. An expression for effective viscosity is obtained. It is shown that the shear viscosity of the dilute suspension depends on the frequency, magnitude, and direction of the highfrequency electromagnetic field. Depending on the frequency of the highfrequency electromagnetic field, the rotation of the suspension particles is decelerated or accelerated, with the viscosity increasing or decreasing, respectively. It is shown that the acceleration of the suspension particles by a highfrequency electromagnetic field and, hence, the decrease in shear viscosity has a resonant nature.  相似文献   

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