Showing papers on "Dissipation published in 1969"
TL;DR: In this article, an experimental system which allows the ready acquisition of heat transfer data necessary for thermal design of turbine airfoils is described, and the measurement of local heat-transfer coefficients on a full-size model is accomplished by considering Joulean dissipation in very thin platinum strips bonded to the model.
Abstract: Although internal impingement cooling of the leading edge of gas-turbine airfoils has been shown to be effective, previously available heat-transfer data are not generally applicable to present-day turbine designs because of the unique geometry requirements. An experimental system which allows the ready acquisition of heat-transfer data necessary for thermal design of turbine airfoils is described. A cold-flow model is developed, and the measurement of local heat-transfer coefficients on a full-size model is accomplished by considering Joulean dissipation in very thin platinum strips bonded to the model. Heattransfer results are given which show the dependence of Nusselt number on Reynolds number, geometry, and chordwise location on the inside leading-edge region of the airfoil. Dimensionless correlations are presented which allow the designer to predict heat transfer for impingement cooling in these geometries for the range of parameters tested.
202 citations
TL;DR: In this article, the effects of viscous dissipation are considered for external natural convection flow over a surface and a class of similar boundary-layer solutions is given and numerical results are presented for a wide range of the dissipation and Prandtl numbers.
Abstract: The effects of viscous dissipation are considered for external natural convection flow over a surface. A class of similar boundary-layer solutions is given and numerical results are presented for a wide range of the dissipation and Prandtl numbers. Several general aspects of similarity conditions for flow over surfaces and in convection plumes are discussed and their special characteristics considered. The general equations including the dissipation effect are given for the non-similar power law surface condition.
163 citations
TL;DR: In this paper, a two-layer dry atmospheric model containing non-geostrophic effects and parametrized dissipation is used to investigate the large-scale tropical eddies as perturbations on a basic state which has empirical static stability and symmetric zonal current.
Abstract: A two-layer dry atmospheric model containing non-geostrophic effects and parametrized dissipation is used to investigate the large-scale tropical eddies as perturbations on a basic state which has empirical static stability and symmetric zonal current. The perturbed motion is treated as a stationary random process driven by stochastic forcing at ±30° latitude. The latter is inferred from observations at 30N. In the predicted internal statistics, 1) variance of horizontal velocity components is much larger at the upper level and decreases equatorward, 2) variances of horizontal divergence and of temperature decrease markedly equatorward, and 3) the eddies transport sensible heat and wave energy equatorward, and transport zonal momentum poleward. The eddies gain kinetic energy from pressure work on the boundaries and lose it by dissipation and conversions to zonal kinetic energy and eddy available potential energy, which is in turn depleted by radiative cooling and conversion to zonal available pot...
94 citations
84 citations
TL;DR: In this article, hot-film anemometry was used to measure the characteristics of turbulence in hydrodynamically smooth and hydroynamically rough open-channel flow and showed that the relative turbulent intensity of the vertical velocity component was about 60% of the longitudinal, and spectral energy distribution was not significantly affected by the type of flow.
Abstract: Measurements of the characteristics of turbulence in hydrodynamically smooth and hydrodynamically rough open-channel flow using hot-film anemometry technics showed: (a) that the relative turbulent intensity of the vertical velocity component was about 60% of the longitudinal, (b) that the spectral energy distribution was not significantly affected by the type of flow, (c) that most of the turbulent energy is contained in frequencies less than 5 hertz, (d) the macroscale of the turbulence as determined from the autocorrelation function was on the same order as the depth and (e) the ratio of the microscale to depth ranged from 0.1 to 0.2. The measurements were used to verify experimentally the longitudinal direction momentum terms in the Navier-Stokes equation and to determine qualitatively the magnitude of the production, diffusion, and dissipation terms in the energy equation.
70 citations
TL;DR: In this article, a combination of the Gibbs equation of thermostatics, with appropriate conservation equations, is shown to yield an expression, (10), for the local production of entropy accompanying the flow of heat and mass.
70 citations
TL;DR: In this paper, a new algorithm for the computation of the energy dissipated by normally incident, monoenergetic electron beams, provides good agreement with experimental data and with the computations of Spencer.
66 citations
TL;DR: In this article, the mixing shock was treated as a one-dimensional macroscopic process and the laws of conservation of mass, momentum and energy were obtained for the pressure and entropy change across the mixing process.
Abstract: In gas-liquid flows a certain sudden change of the flow structure may occur, which can be described as a transition from ‘jet flow’ to ‘froth flow’ accompanied by energy dissipation and pressure build-up. Upstream of this phenomenon the gas is the continuous phase; downstream the liquid is the continuous phase. The phenomenon, which has been called ‘mixing shock’, shows some similarity and also some differences with the plane shock wave in gasdynamics. In the first part of this paper the mixing shock is treated as a one-dimensional macroscopic process. With the aid of the laws of conservation of mass, momentum and energy, expressions are obtained for the pressure and entropy change across the mixing process. In addition the stability of the mixing shock in a cylindrical flow channel is treated. Next, a theory that explains the gas entrainment mechanism in the mixing shock is proposed. As an experimental tool a water-air ejector with the water as a driving medium was used. The experiments confirm the macroscopic and the microscopic theory. In the last section of this paper theoretical and experimental evidence is combined to construct a model of the processes that play a role in the shock.
57 citations
TL;DR: In this article, the effects of particle size, geometry, and interface formation on strain magnification were considered and compared with experimental data for three types of glass particle in a polyurethane elastomeric matrix.
42 citations
TL;DR: In this article, it was shown from clear-air turbulence spectra measurements and clear air turbulence probabilities that the energy dissipation between 25,000 and 40,000 ft is just over 1 watt m 2, a quantity of the same order as the dissipation near the ground.
Abstract: It is shown from clear-air turbulence spectra measurements and clear-air turbulence probabilities that the energy dissipation between 25,000 and 40,000 ft is just over 1 watt m ?2 , a quantity of the same order as the dissipation near the ground. DOI: 10.1111/j.2153-3490.1969.tb00448.x
40 citations
01 Jun 1969
TL;DR: In this article, a nonlinear response of a single Helmholtz resonator subjected to finite amplitude pressure oscillations, detailing entrance, orifice and cavitational flow is described.
Abstract: Nonlinear response of single Helmholtz resonator subjected to finite amplitude pressure oscillations, detailing entrance, orifice and cavitational flow
TL;DR: In this paper, a semi-infinite chain of mass points with linear and nonlinear nearest neighbor interaction is analyzed and a finite velocity step is applied at the first mass point at zero time to generate a shock-like disturbance in the system.
TL;DR: In this paper, a model of a microwave radiation field contained within a plasma dielectric sphere, resonant at a frequency much greater than the electron-molecule collision frequency, is presented and its properties discussed.
Abstract: A model for ball lightning is presented and its properties discussed. The model is that of a microwave radiation field contained within a plasma dielectric sphere, resonant at a frequency much greater than the electron-molecule collision frequency. Calculations are made of the energy stored in the microwave field, the electron temperature, the rate of energy loss due to ionization, and the effects of recombination. It is concluded (a) that a self-consistent set of conditions can be obtained only when the neutral density within the sphere is much lower than atmospheric, and (b) that the microwave field strength required is of the order of 109V/m. Under these conditions the radiation pressure becomes comparable to that of the atmosphere; the second case investigated is when these two become equal. It is then found that this ‘radiation bubble’ appears to satisfy the requirements imposed on energy storage and dissipation, recombination and resonant frequency. The electron density in such a bubble is found to be typically 1011 cm−3 and the stored energy typically 103 Joules. A discussion is given of some of the problems associated with the model-formation, stability, neutral number density, and the problem of hydrostatic equilibrium.
TL;DR: In this article, it is suggested that, in Petschek's model of magnetic field annihilation, plasma which flows through the boundary layer where its magnetic energy is released is rendered highly turbulent by current driven electrostatic instability.
Abstract: It is suggested that, in Petschek's model of magnetic field annihilation, plasma which flows through the boundary layer where its magnetic energy is released is rendered highly turbulent by current driven electrostatic instability. This leads to a physical insight into the mechanism of dissipation, and, by analogy with laboratory experiments on turbulent plasma, can explain the observed X-ray and microwave emissions. When the microstructure is calculated using electrical conductivity appropriate to highly turbulent plasma, a field configuration exists in which protons can be accelerated to very high energies. The results of some numerical calculations of this process are presented.
TL;DR: In this article, the thermal effects of resonant coupling hydromagnetic oscillations in inhomogeneous, finite-β plasmas were studied and the basic equations for the coupling modes between the Alfven and magnetosonic waves in a nonuniform, collisionless plasma were obtained.
Abstract: The thermal effects of resonant coupling hydromagnetic oscillations in inhomogeneous, finite‐β plasmas, are studied. There are two thermal effects for such oscillations, the thermal phase mixing due to wave‐particle resonance interactions and the drift effect arising from plasma inhomogeneities. Applying the drift kinetic approximation, the basic equations for the coupling modes between the Alfven and magnetosonic waves in a nonuniform, collisionless plasma are obtained. For the plasma with β ≃ me/mi, ratio of electron to ion mass, it is shown that the electron thermal dissipation of hydromagnetic oscillations with ω/k‖ ≃ VA is most effective within the resonance coupling regions which appear in the cold plasma limit. This dissipation is very large as compared with the same dissipation process in the homogeneous plasma. On the other hand, if the hot plasma with β ∼ 1 is considered, attenuation of hydromagnetic waves due to ion‐wave interaction becomes important. It will be an important process for ion hea...
TL;DR: This paper found that phase changes due to dissipation can stabilize nonlinear instablities, which otherwise grow faster then exponentially, and vice versa it seems possible that dissipation effects destabilize situations which are otherwise stable.
TL;DR: In this article, the set of random phase equations describing wave interaction with dissipation is solved exactly and the critical limit for stabilization is determined, which is the same as in this paper.
TL;DR: In this article, a review is given of some recent measurements of the following energy balance parameters in the 90-110 km height region: ϵ0, the viscous dissipation of kinetic energy by shears in the mean winds; ϵd, the viscosity of the kinetic energy from the mean motion to the turbulent motion; and ϵg, the transfer of turbulent kinetic energy to potential energy by buoyancy action.
Abstract: A review is given of some recent measurements of the following energy balance parameters in the 90–110 km height region: ϵ0, the viscous dissipation of kinetic energy by shears in the mean winds; ϵd, the viscous dissipation of kinetic energy by shears in the turbulent winds; ϵs, the transfer of kinetic energy from the mean motion to the turbulent motion; ϵg, the transfer of turbulent kinetic energy to potential energy by buoyancy action; and ϵw, the rate of dissipation of wave energy of tides and irregular winds interpreted as gravity waves. Some measurements of the growth rates of globular structure on chemical release clouds and the growth rate of interglobular distances are presented. These data indicate that the diffusion mechanism is a mixture of the 〈v2〉t2 variation expected for the diffusion of a point from its initial position with the ϵdt3 variation expected for the variation of the separation between pairs of points.
TL;DR: In this paper, a nonlinear mechanism connected with the motion of dislocations is proposed to explain an attenuation proportional to the frequency (internal friction Q−1 independent of the frequency) present for the earth's crust.
Abstract: To explain an attenuation proportional to the frequency (internal friction Q−1 independent of the frequency) present for waves in the earth's crust, a nonlinear mechanism connected with the motion of dislocations is proposed. With the kink model for dislocation motion, it is shown that an energy loss occurs when the kink goes over the kink barrier and becomes unstable. This loss is proportional to the number of kink displacements, and for a given strain level the number of kink displacements per cycle, i.e. the Q−1 value, will be independent of the frequency. The energy loss measured is consistent with theoretical calculations of the dissipation stress, and the loop length lA and the number of dislocations found are consistent with the results for polycrystalline metals and rocks.
TL;DR: In this paper, an approximate analysis of the plastic energy dissipation rate during stable growth of a centrally located through crack is presented, where the analysis is not applicable in this inner zone as deformation is not homogeneous.
Abstract: An approximate analysis is presented for the calculation of the plastic energy dissipation rate during stable growth of a centrally located through crack. in a sheet subjected to gradually increasing uniaxial tension normal to the crack plane. It is shown that the plastic energy dissipation rate is a function of the slow growth parameter (δωp/δσ)·(dσ/da)+(δωp/δa), where ωp is the plastic enclave width in the plane of the crack and dσ/da is the rate of increase of the gross stress with respect to stable growth. At the point of instability this parameter becomes equal to δωp/δa. By assuming that this parameter is zero at the point of instability, a simple expression is obtained for the plastic energy dissipation rate. The analysis excludes the energy dissipation rate resulting from energy changes in an inner “fracture zone” in the immediate neighborhood of the crack tip in which it is presumed that fracture processes such as vacancy formation, crack initiation by dislocation pile ups etc., are active. The analysis is not applicable in this inner zone as deformation is not homogeneous.
TL;DR: In this article, the authors derived transformation laws for the energy density W, the power flow density S and the time rate of energy density dissipation Q of a wave in an anisotropic dispersive medium which is in motion.
Abstract: The transformation laws have been derived for the energy density W , the power-flow density S and the time rate of energy density dissipation Q of a wave in an anisotropic dispersive medium which is in motion. It has been found that to the zeroth order in \(\tilde{\varepsilon}^{a}\) (antihermitian part of the reduced permittivity) the action density W /ω (ω is the frequency) and the action-flow density S /ω transform in the same way as the energy and momentum of a particle do relativistically. Response of a medium against motion of a test charge immersed in the medium is calculated and conditions in which the negative-energy wave behaves as an active was are discussed.
TL;DR: In this paper, a study of the energy dissipation in the flow of the superfluid component of liquid helium in wide chambers (6-1 mm) and slits (150-15 μm) is performed by means of a calorimetric technique.
TL;DR: In this article, an integral formulation for the scattered-wave solution of an isolated fiber is used to study the multiple scattering in an infinite slab of the composite material and the transmitted and reflected waves from the composite and from a homogeneous slab are shown to be similar.
Abstract: A theoretical study is presented on the propagation of a plane sinusoidal wave through a material that is reinforced with parallel fibers in one direction. The wave propagates in a direction normal to the fibers, and both fiber and matrix are made of linear elastic materials. An integral formulation for the scattered‐wave solution of an isolated fiber is used to study the multiple scattering in an infinite slab of the composite material. The transmitted and reflected waves from the composite and from a homogeneous slab are shown to be similar. By matching the two sets of results, formulas expressed in terms of the isolated‐fiber solution are derived for the wave speed, the effective density, and the modulus of the composite. In general, the effective density and modulus so defined are complex numbers and depend on the wave frequency. This fact indicates the possible existence of dissipation and dispersion in the composite under dynamic loadings. A series solution is presented for a composite containing ci...
Patent•
28 Aug 1969
TL;DR: In this article, a high speed rotating system driven by a motor which constitutes a source of heat is described, where the system has bearings of porous material through which a liquid coolant is fed and in which heat of friction causes vaporization of the lubricant and hence cooling of the bearing.
Abstract: A high speed rotating system driven by a motor which constitutes a source of heat. The system has bearings of porous material through which a liquid coolant is fed and in which heat of friction causes vaporization of the lubricant and hence cooling of the bearing and dissipation of heat from the motor due to the fact that the latent heat of vaporization is derived from the bearing surface and immediately adjacent areas.
TL;DR: In this paper, the authors examined the effect of a stress pulse on equipment located underground and concluded that linear dissipative mechanisms are insufficient in themselves to yield a substantial reduction in accelerations for equipment buried in a saturated soil.
Abstract: The problem of a stress pulse applied to a semi-infinite region of a poroelastic medium is examined to determine the effect of a stress pulse on equipment located underground. If dissipation is neglected, an applied step pulse splits into two pulses that propagate unchanged in shape, each moving at one of the dilatational speeds of the medium. If dissipation is included, the step pulse splits into a “smeared-out” component and a component that retains the sharp front. The latter component travels at a speed that would occur if the fluid and solid were locked together. It is concluded that linear poroelastic dissipative mechanisms are insufficient in themselves to yield a substantial reduction in accelerations for equipment buried in a saturated soil.
Patent•
28 Nov 1969
TL;DR: A rotary friction construction has a rotatable hub on which there is at least a mounting member mounting a friction member in a rivetless, bond-free manner to permit the dissipation of heat generated at the friction member without producing a consequent distortion of the mounting or the friction members as discussed by the authors.
Abstract: A rotary friction construction having a rotatable hub on which there is at least a mounting member mounting a friction member in a rivetless, bond-free manner to permit the dissipation of heat generated at the friction member without producing a consequent distortion of the mounting or the friction members.
TL;DR: In this paper, the effects of the Lyman continuum on the shock front were analyzed for a range of shock speeds typifying a cepheid atmosphere, and it was shown that to a great extent, the structure of the shock structure is separated into successive regions of internal and radiative relaxation by an intermediate layer of ionized gas appearing at high shock speeds.
Abstract: A shock wave passing through a stellar atmosphere disturbs the gas, and the consequent adjustment of the fluid is a redistribution of the shock's kinetic energy among the various degrees of freedom. This paper deals with the effects of the Lyman continuum on the shock front. The shock heated gas is cooled principally by ionizing collisions of ground state atoms. This process is followed by a large quasi-isothermal region in which radiative recombinations occur. A final cycle of processes consisting of ionization, photo-recombinations to upper-level and collisional de-excitation, gives way to a sequence of statistical balances as each degree of freedom in the fluid attains equilibrium. Our calculations show that to a great extent, the shock structure is separated into successive regions of internal and radiative relaxation by an intermediate layer of ionized gas appearing at high shock speeds. Numerical results are presented for a range of shock speeds typifying a cepheid atmosphere.