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1.
The thermal decomposition of nitric oxide (diluted in Argon) has been measured behind incident shock waves by means of IR diode laser absorption spectroscopy. In two independent runs the diode laser was tuned to the=0 =12 3/2 R(18.5)-rotational vibrational transition and the=1 =22 3/2 R(20.5)-rotational vibrational transition of nitric oxide, respectively. These two transitions originating from the vibrational ground state (=0) and the first excited vibrational state (=1) were selected in order to probe the homogeneity along the absorption path. The measured NO decomposition could satisfactorily be described by a chemical reaction mechanism after taking into account boundary layer corrections according to the theory of Mirels. The study forms a further proof of Mirels' theory including his prediction of the laminar-turbulent transition. It also shows, that the inhomogeneities from the boundary layer do not affect the IR linear absorption markedly.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.  相似文献   

2.
In this paper, a method using the mean velocity profiles for the buffer layer was developed for the estimation of the virtual origin over a riblets surface in an open channel flow. First, the standardized profiles of the mixing length were estimated from the velocity measurement in the inner layer, and the location of the edge of the viscous layer was obtained. Then, the virtual origins were estimated by the best match between the measured velocity profile and the equations of the velocity profile derived from the mixing length profiles. It was made clear that the virtual origin and the thickness of the viscous layer are the function of the roughness Reynolds number. The drag variation coincided well with other results.Nomenclature f r skin friction coefficient - f ro skin friction coefficient in smooth channel at the same flow quantity and the same energy slope - g gravity acceleration - H water depth from virtual origin to water surface - H + u*H/ - H false water depth from top of riblets to water surface - H + u*H/ - I e streamwise energy slope - I b bed slope - k riblet height - k + u*k/ - l mixing length - l s standardized mixing length - Q flow quantity - Re Reynolds number volume flow/unit width/v - s riblet spacing - u mean velocity - u* friction velocity = - u* false friction velocity = - y distance from virtual origin - y distance from top of riblet - y 0 distance from top of riblet to virtual origin - y v distance from top of riblet to edge of viscous layer - y + u*y/ - y + u*y/ - y 0 + u*y 0/ - u + u*y/ - shifting coefficient for standardization - thickness of viscous layer=y 0+y - + u*/ - + u*/ - eddy viscosity - ridge angle - v kinematic viscosity - density - shear stress  相似文献   

3.
In this paper the solution for the bending of corner-supported rectangular plate under concentrated load at any point (α/2, η) of the middle line of the plate is given by means of a conception called modified simply supported edges and the method of superposition. Some numerical example is presented. The solution obtained by this method checks very nicely with what was obtained by G.T. Shih[3] by means of spline finite element method when η=d/2. This shows that this method of solution is satisfactory.  相似文献   

4.
An analysis is presented for laminar source flow between parallel stationary porous disks with suction at one of the disks and equal injection at the other. The solution is in the form of an infinite series expansion about the solution at infinite radius, and is valid for all suction and injection rates. Expressions for the velocity, pressure, and shear stress are presented and the effect of the cross flow is discussed.Nomenclature a distance between disks - A, B, ..., J functions of R w only - F static pressure - p dimensionless static pressure, p(a 2/ 2) - Q volumetric flow rate of the source - r radial coordinate - r dimensionless radial coordinate, r/a - R radial coordinate of a point in the flow region - R dimensionless radial coordinate of a point in the flow region, R - Re source Reynolds number, Q/2a - R w wall Reynolds number, Va/ - reduced Reynolds number, Re/r 2 - critical Reynolds number - velocity component in radial direction - u dimensionless velocity component in radial direction, a/ - average radial velocity, Q/2a - u dimensionless average radial velocity, Re/r - ratio of radial velocity to average radial velocity, u/u - velocity component in axial direction - v dimensionless velocity component in axial direction, v - V magnitude of suction or injection velocity - z axial coordinate - z dimensionless axial coordinate, z a - viscosity - density - kinematic viscosity, / - shear stress at lower disk - shear stress at upper disk - 0 dimensionless shear stress at lower disk, - 1 dimensionless shear stress at upper disk, - dimensionless stream function  相似文献   

5.
Conclusions The investigations have shown that the auxiliary asynchronous parametric excitation ca be used to effectively suppress resonance vibrations in systems with highly nonlinear elast characteristics. Either local or wideband suppression of the resonance regime can be achieved, depending on the relation between the frequencies of the primary external and auxiliary parametric excitations (/=const or /const); also, the width and positions of the instability intervals can be controlled. This affords the possibility of using auxiliary parametric excitation not only to enhance the efficiency of nonlinear antivibration systems (by wideband suppression of resonance vibrations), but also for the design of fundamentally new resonance devices to monitor the frequency and amplitude of vibrations by exploiting the effect of local instability of the resonance regime.Polytechnic Institute, Riga. Translated from Prikladnaya Mekhanika, Vol. 27, No. 5, pp. 102–107, May, 1991.  相似文献   

6.
Summary Thermal free convection from a sphere has been studied by melting solid benzene spheres in excess liquid benzene (Pr=8,3; 108<Gr<109). Overall heat transfer as well as local heat transfer were investigated. For the effect of cold liquid produced by the melting a correction has been applied. Results are compared with those obtained by other workers who used alternative experimental methods.Nomenclature coefficient of heat transfer - d characteristic length, here diameter of sphere - thermal conductivity - g acceleration of free fall - cubic expansion coefficient - T temperature difference between wall and fluid at infinity - kinematic viscosity - density - c specific heat capacity - a thermal diffusivity (=/c) - D diffusion coefficient - Nu dimensionless Nusselt number (=d/) - Nu* the analogous number for mass transfer (=kd/D) - mean value of Nusselt number - Gr dimensionless Grashof number (=gd 3T/ 2) - Gr* the analogous number for mass transfer (=gd 3x/ 2) - Pr dimensionless Prandtl number (=/a) - Sc dimensionless Schmidt number (=/D)  相似文献   

7.
This paper concerns with obtaining the solution of the problem of viscous lifting and drainage of a thin liquid film clinging to a vertical plane surface moving with a velocityf(t) in the presence of a transverse magnetic field. Specializing to the case when the surface moves with a constant acceleration, it has been found that the film thickness, for large magnetic fields, increases with the increase in magnetic field.Nomenclature a acceleration of the plate - A non-dimensional acceleration, =a/g - B magnetic induction vector - B 0 applied magnetic field - f(t) any function oft - Laplace transform off(t) - g gravitational acceleration - h film thickness - H non-dimensional film thickness, =h(g/ 2)1/3 - J current density vector - k (/)1/2 B 0 - M k( 2/g)1/3 - n summation index - q mass flow rate - Q non-dimensional mass flow rate, =q/ - t time - T non-dimensional time, =t(g 2/)1/3 - Laplace transform ofv(x, t) - V fluid velocity vector, =[0,v(x, t), 0] - (x, y, z) space coordinates - Y non-dimensionaly-coordinate, =y(g/ 2)1/3 Greek symbols n (n+1/2) - conductivity - density - kinematic viscosity  相似文献   

8.
Summary This paper is devoted to a study of the flow of a second-order fluid (flowing with a small mass rate of symmetrical radial outflow m, taken negative for a net radial inflow) over a finite rotating disc enclosed within a coaxial cylinderical casing. The effects of the second-order terms are observed to depend upon two dimensionless parameters 1 and 2. Maximum values 1 and 2 of the dimensionless radial distances at which there is no recirculation, for the cases of net radial outflow (m>0) and net radial inflow (m<0) respectively, decrease with an increase in the second-order effects [represented by T(=1+2)]. The velocities at 1 and 2 as well as at some other fixed radii have been calculated for different T and the associated phenomena of no-recirculation/recirculation discussed. The change in flow phenomena due to a reversal of the direction of net radial flow has also been studied. The moment on the rotating disc increases with T.Nomenclature , , z coordinates in a cylindrical polar system - z 0 distance between rotor and stator (gap length) - =/z 0, dimensionless radial distance - =z/z 0, dimensionless axial distance - s = s/z0, dimensionless disc radius - V =(u, v, w), velocity vector - dimensionless velocity components - uniform angular velocity of the rotor - , p fluid density and pressure - P =p/(2 z 02 2 , dimensionless pressure - 1, 2, 3 kinematic coefficients of Newtonian viscosity, elastico-viscosity and cross-viscosity respectively - 1, 2 2/z 0 2 , resp. 3/z 0 2 , dimensionless parameters representing the ratio of second-order and inertial effects - m = , mass rate of symmetrical radial outflow - l a number associated with induced circulatory flow - Rm =m/(z 01), Reynolds number of radial outflow - R l =l/(z 01), Reynolds number of induced circulatory flow - Rz =z 0 2 /1, Reynolds number based on the gap - 1, 2 maximum radii at which there is no recirculation for the cases Rm>0 and Rm<0 respectively - 1(T), 2(T) 1 and 2 for different T - U 1(T) (+) = dimensionless radial velocity, Rm>0 - V 1(T) (+) = , dimensionless transverse velocity, Rm>0 - U 2(T) (–) = , dimensionless radial velocity, Rm=–Rn<0, m=–n - V 2(T) (–) = , dimensionless transverse velocity, Rm<0 - C m moment coefficient  相似文献   

9.
Zusammenfassung Der lokale Stoffübergang wurde in Abhängigkeit von der Meßlänge, dem Startort und der Zulaufhöhe gemessen. Der Gültigkeitsbereich der Theorie von Nusselt wird ermittelt. Die Reynolds-Zahl nahm Werte zwischen 3,86 und 2496 an. Die örtlich wirkende Hydrodynamik ist entscheidend für das Anwachsen der örtlichen Sherwood-Zahl. Die Genauigkeit aller Versuchsergebnisse kann auf ± 5% abgeschätzt werden.
Investigation of the local mass transfer of a laminar and turbulent falling liquid film
The local mass transfer was measured as a function of the measuring length, the starting point and the liquid height above the ring-slot. The range of the Reynolds number was 3,86 Re 2496. The validity of the Nusselt theory and the range of it is shown. The local hydrodynamic is the most important factor of the increase of the local Sherwood number. The accuracy of the measurements is ± 5%.

Bezeichnungen a Temperaturleitfähigkeit m2/s=/(cp) - c Konzentration, c=¯c + c kmol/m3 - ci0 Konzentration im Flüssigkeitskern kmol/m3 - D Diffusionskoeffizient m2/s - EL-NR Elektrodennummer - Fa Faraday-Konstante A s/kgäq=96,5·106 - g Erdbeschleunigung m/s2 - iG Grenzstromdichte A/m2 - u Geschwindigkeit in x-Richtung, u= + u - U Umfang des Rohres m - v Geschwindigkeit in y-Rich- m/stung, v=¯v + v - V* Volumenstrom m3/s - x Lauflänge, Koordinate in m Strömungsrichtung - xM Meßlänge für den Stoff-Übergang m - xST Startort für den Stoff-Übergang m - y Wegkoordinate senkrecht zur Rohroberfläche m - z Wertigkeit der Elektro-denreaktion kgäq/kmol - ZH Zulaufhöhe m - Wärmeübergangskoeffizient W/m2C - Stoffübergangskoeffizient m/s - Filmdicke m - Wärmeleitfähigkeit W/(mC) - kinematische Viskosität m2/s - Re=u/=V*/U Reynolds-Zahl - Pr=/a=cp/ Prandtl-Zahl - Sc=/D Schmidt-Zahl - Nu= / Nusselt-Zahl - Sh= /D Sherwood-Zahl - SHL lokale Sherwood-Zahl - SHM mittlere Sherwood-Zahl - - zeitlich gemittelt - örtlich gemittelt Die Durchführung der Arbeit am Institut für Verfahrens — und Kältetechnik der ETH Zürich bei Prof. Dr. P. Grassmann wurde ermöglicht durch Zuschüsse der Kommission zur Förderung der wissenschaftlichen Forschung und meiner Eltern.  相似文献   

10.
The paper reports the outcome of a numerical study of fully developed flow through a plane channel composed of ribleted surfaces adopting a two-equation turbulence model to describe turbulent mixing. Three families of riblets have been examined: idealized blade-type, V-groove and a novel U-form that, according to computations, achieves a superior performance to that of the commercial V-groove configuration. The maximum drag reduction attained for any particular geometry is broadly in accord with experiment though this optimum occurs for considerably larger riblet heights than measurements indicate. Further explorations bring out a substantial sensitivity in the level of drag reduction to the channel Reynolds number below values of 15 000 as well as to the thickness of the blade riblet. The latter is in accord with the trends of very recent, independent experimental studies.Possible shortcomings in the model of turbulence are discussed particularly with reference to the absence of any turbulence-driven secondary motions when an isotropic turbulent viscosity is adopted. For illustration, results are obtained for the case where a stress transport turbulence model is adopted above the riblet crests, an elaboration that leads to the formation of a plausible secondary motion sweeping high momentum fluid towards the wall close to the riblet and thereby raising momentum transport.Nomenclature c f Skin friction coefficient - c f Skin friction coefficient in smooth channel at the same Reynolds number - k Turbulent kinetic energy - K + k/ w - h Riblet height - S Riblet width - H Half height of channel - Re Reynolds number = volume flow/unit width/ - Modified turbulent Reynolds number - R t turbulent Reynolds numberk 2/ - P k Shear production rate ofk, t (U i /x j + U j /x i ) U i /x j - dP/dz Streamwise static pressure gradient - U i Mean velocity vector (tensor notation) - U Friction velocity, w/ where w=–H dP/dz - W Mean velocity - W b Bulk mean velocity through channel - y + yU /v. Unless otherwise stated, origin is at wall on trough plane of symmetry - Kinematic viscosity - t Turbulent kinematic viscosity - Turbulence energy dissipation rate - Modified dissipation rate – 2(k 1/2/x j )2 - Density - k , Effective turbulent Prandtl numbers for diffusion ofk and   相似文献   

11.
The unsteady laminar boundary layer flow is investigated for a semi-infinite flat plate subjected to impulsive motion. An approximate solution is obtained by utilizing Meksyn's method. These results vary smoothly from Rayleigh's unsteady solution to the steady state solution of Blasius. Results are compared to those of Lam and Crocco.Nomenclature A expansion coefficient, see eq. (13) - a expansion coefficient, see eq. (10) - B expansion coefficient, see eq. (14) - b expansion coefficient, see eq. (12) - G function defined by eq. (6) - U free stream velocity - u velocity in x direction - v velocity in y direction - x coordinate along plate - y coordinate normal to plate Greek symbols (l, ) incomplete gamma function - function defined by eq. (15) - y(U/x) 1/2 - kinematic viscosity - x/Ut - (Uvx)1/2 f(, )  相似文献   

12.
The wisdom of classicalunified field theories in the conceptual framework of Weyl, Eddington, Einstein and Schrödinger has often been doubted and in particular there does not appear to be any empirical reason why the Einstein-Maxwell (E-M) theory needs to be geometrized. The crux of the matter is, however not whether the E-M theory is aesthetically satisfactory but whether it answers all the modern questions within the classical context. In particular, the E-M theory does not provide a classical platform from which the Dirac equation can be derived in the way Schrödinger's equation is derived from classical mechanics via the energy equation and the Correspondence Principle. The present paper presents a non-dualistic unified field theory (UFT) in the said conceptual framework as propounded by M. A. Tonnelat. By allowing the metric formds 2=g dx v x v and the non-degenerate two-formF=(1/2> l) dx vdx vto enter symmetrically into the theory we obtain a UFT which contains Einstein's General Relativity and the Born-Infeld electrodynamics as special cases. Above all, it is shown that the Dirac equation describing the electron in an external gravito-electromagnetic field can be derived from the non-dualistic Einstein equation by a simple factorization if the Correspondence Principle is assumed.  相似文献   

13.
Conclusions The extensions of Trostel's solutions derived in this paper may be employed tor general over wide conditions with a resulting error less than 3%, the stress values being too small in magnitude by this amount. The error decreases as the variation of physical properties of the media decreases or as 1/2. M. M. Stanii, Lectures in Mathematical Elasticity during summer semester 1958, Purdue University.  相似文献   

14.
A theoretical study is made of the flow behavior of thin Newtonian liquid films being squeezed between two flat plates. Solutions to the problem are obtained by using a numerical method, which is found to be stable for all Reynolds numbers, aspect ratios, and grid sizes tested. Particular emphasis is placed on including in the analysis the inertial terms in the Navier-Stokes equations.Comparison of results from the numerical calculation with those from Ishizawa's perturbation solution is made. For the conditions considered here, it is found that the perturbation series is divergent, and that in general one must use a numerical technique to solve this problem.Nomenclature a half of the distance, or gap, between the two plates - a 0 the value of a at time t=0 - adot da/dt - ä d2 a/dt 2 - d3 a/dt 3 - a i components of a contravariant acceleration vector - f unknown function of z 0 and t defined in (6) - f i function defined in (9) f 1=r 0 g(z 0, t) f 2= 0 f 3=f(z 0, t) - F force applied to the plates - g unknown function of z 0 and t defined in (6) - g g/z 0 - h grid dimension in the z 0 direction (see Fig. 5) - Christoffel symbol - i, j, k, l indices - k grid dimension in the t direction (see Fig. 5) - r radial coordinate direction defined in Fig. 1 - r 0 radial convected coordinate - R radius of the circular plates - t time - v r fluid velocity in the r direction - v z fluid velocity in the z direction - v fluid velocity in the direction - x i cylindrical coordinate x 1=r x2= x3=z - z vertical coordinate direction defined in Fig. 1 - z 0 vertical convected coordinate - tangential coordinate direction - 0 tangential convected coordinate - viscosity - kinematic viscosity, / - i convected coordinate 1=r0 2=0 3=z0 - density  相似文献   

15.
Summary This paper presents the solution to the problem of determining the flow field and the fluctuating torque necessary to sustain the motion of a torsionally oscillating plate in a viscous conducting fluid subjected to a uniform axial field under the assumptions that the amplitude of the oscillation is small and that the magnetic Prandtl number Pr m () is small enough to justify the neglect of induced fields. The analysis reveals that the field decreases the flow velocities, but increases the magnitude of the fluctuating torque.  相似文献   

16.
Zusammenfassung Zur Berechnung turbulenter Strömungen wird das k--Modell im Ansatz für die turbulente Scheinzähigkeit erweitert, so daß es den Querkrümmungs- und Dichteeinfluß auf den turbulenten Transportaustausch erfaßt. Die dabei zu bestimmenden Konstanten werden derart festgelegt, daß die bestmögliche Übereinstimmung zwischen Berechnung und Messung erzielt wird. Die numerische Integration der Grenzschichtgleichungen erfolgt unter Verwendung einer Transformation mit dem Differenzenverfahren vom Hermiteschen Typ. Das erweiterte Modell wird auf rotationssymmetrische Freistrahlen veränderlicher Dichte angewendet und zeigt Übereinstimmung zwischen Rechnung und Experiment.
On the influence of transvers-curvature and density in inhomogeneous turbulent free jets
The prediction of turbulent flows based on the k- model is extended to include the influence of transverse-curvature and density on the turbulent transport mechanisms. The empirical constants involved are adjusted such that the best agreement between predictions and experimental results is obtained. Using a transformation the boundary layer equations are solved numerically by means of a finite difference method of Hermitian type. The extended model is applied to predict the axisymmetric jet with variable density. The results of the calculations are in agreement with measurements.

Bezeichnungen Wirbelabsorptionskoeffizient - ci Massenkonzentration der Komponente i - cD, cL, c, c1, c2 Konstanten des Turbulenzmodells - d Düsendurchmesser - E bezogene Dissipationsrate - f bezogene Stromfunktion - f Korrekturfunktion für die turbulente Scheinzähigkeit - j turbulenter Diffusionsstrom - k Turbulenzenergie - ki Schrittweite in -Richtung - K dimensionslose Turbulenzenergie - L turbulentes Längenmaß - Mi Molmasse der Komponente i - p Druck - allgemeine Gaskonstante - r Querkoordinate - r0,5 Halbwertsbreite der Geschwindigkeit - r0,5c Halbwertsbreite der Konzentration - T Temperatur - u Geschwindigkeitskomponente in x-Richtung - v Geschwindigkeitskomponente in r-Richtung - x Längskoordinate - y allgemeine Funktion - Yi diskreter Wert der Funktion y - Relaxationsfaktor für Iteration - turbulente Dissipationsrate - transformierte r-Koordinate - kinematische Zähigkeit - Exponent - transformierte x-Koordinate - Dichte - k, Konstanten des Turbulenzmodells - Schubspannung - allgemeine Variable - Stromfunktion - Turbulente Transportgröße Indizes 0 Strahlanfang - m auf der Achse - r mit Berücksichtigung der Krümmung - t turbulent - mit Berücksichtigung der Dichte - im Unendlichen - Schwankungswert oder Ableitung einer Funktion - – Mittelwert Herrn Professor Dr.-Ing. R. Günther zum 70. Geburtstag gewidmet  相似文献   

17.
In marine geophysical seismological prospecting extensive use is made of towed receiving systems consisting of extended flexible cylinders containing acoustic sensors over which the water flows in the longitudinal direction. The boundary layer pressure fluctuations on the cylinder surface are picked up by the sensors as hydrodynamic noise. This paper is concerned with the study of the energy and spacetime characteristics of the pressure fluctuations in the turbulent boundary layer on an extended flexible cylinder in a longitudinal flow. The pressure fluctuations on the cylinder surface have been investigated experimentally for ReX=(2–4)·107, a dimensionless diameter of the pressure fluctuation sensors d p + =dpu*/=500, where dp is the sensor diameter, u* the dynamic viscosity, and the viscosity coefficient, and frequencies 0.02311.259 (=*/U). The spectral and correlation characteristics of the pressure fluctuations on the surface of the flexible cylinder are found to differ from the corresponding characteristics for a rigid cylinder [1–4].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i aza, No, 5, pp. 49–54, September–October, 1989.  相似文献   

18.
Zusammenfassung Es wurden die Verhältnisse der empirisch ermittelten Nusselt- und Sherwoodzahlen bei querangeströmten Membran- und Glattrohrbündeln errechnet. Auf Grund dessen ist die Analogiefunktion=Nu/Sh statistisch abgeschätzt und mit den Analogien von Chilton-Colburn und Jayatillaka verglichen worden.
Analogy between convective heat and mass transfer in tube banks
An attempt is made to compare the mass and heat transfer for the flow normal to the finned and conventional i.e. plain tube banks. The comparison is based upon experimental results for various staggered and in-line arrangements of the tubes. The statistically determined analogy factor=Nu/Sh is compared with Chilton-Colburn and Jayatillaka analogies.

Formelzeichen Le=Sc/Pr Lewiszahl - Nu= 1 d/ Nusseltzahl - Pr=/a Prandtlzahl - Re=w d/v Reynoldszahl - Sc=/D A Schmidtzahl - Sh= Ad/A Sherwoodzahl - a Temperaturleitzahl - d Außendurchmesser des Rohres - DA kinematische Diffusionszahl - s l Längsteilung - s q Querteilung - w Geschwindigkeit im engsten Querschnitt zwischen den Rohren (A-A, Bild 1) - 1 Wärmeübergangszahl - A Stoffübergangszahl - A dynamische Diffusionszahl - =Nu/Sh Analogiefunktion - l=si/d q=sq/d  相似文献   

19.
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   

20.
The present work aims to consider the.fourth test of general relativity theory by Shapiro.using radar echo delay in Yu’s(Ω,Aμν)-field theory.  相似文献   

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