Assessment of a quintuple hotwire measurement technique for highly turbulent flows

A five-wire calibration and measurement technique is presented, which is an extension of the four-wire method developed by Döbbeling et al. (1990a, b). From numerical simulations of the uniqueness domain and the angular resolution it is concluded that the uniqueness domain of the quintuple technique can be expanded to a hemisphere as opposed to the four-wire techniques which are restricted to a conical domain of about 40° half angle. Measurements of the mean velocities and Reynolds stresses in a low-turbulence jet and in grid turbulence confirm and complement the results of the numerical simulations. It is thus shown that the quintuple method achieves increased accuracy in an expanded measurement range.The work of D. Hölzer, student of engineering at the University of Karlsruhe, and the support of W. Paulat and W. Pfeffinger in writing the data aquisition software, and H. Klette who manufactured the probe, is gratefully acknowledged. This work was supported by the Deutsche Forschungsgemeinschaft within the framework of the Sonderforschungsbereich 167, Hochbelastete Brennräume- Stationäre Gleichdruckverbrennung, Teilprojekt A10.     

Construction of asymptotic solutions to scattering problems in the fourier transform representation

Summary It is shown that the construction of a high-frequency asymptotic solution for the problem of a slit can be greatly simplified in the Fourier transform representation. This is accomplished by iterative solution of a pair of coupled integral equations whose kernels are the Green's functions for two isolated half planes.Part of the results given in this paper were presented at the USNC-URSI Spring Meeting held in Washington, D. C. in May, 1964.The author was with the Department of Electrical Engineering, New York University, when the research reported here was performed.     

Similarity solutions to some non-linear impact problems

Impact and wave propagation problems are considered for nonlinearly viscous and nonlinearly elastic materials. The governing partial differential equations are reduced to ordinary differential equations by means of similarity transformations. The resulting non-linear two point boundary value problems are then, in general, integrated numerically, although some closed form solutions are presented.     

On the influence of a flexural biasing state on the velocity of piezoelectric surface waves

A system of linear electroelastic equations for small fields superposed on a bias is applied in the determination of the velocity of acoustic surface waves in piezoelectric substrates subject to flexural biasing stresses. The influence of the biasing stresses appears in the boundary conditions as well as the differential equations. Direct calculations performed for both quartz and lithium niobate when the spatial variation of the flexural biasing state is omitted indicate that the biasing stresses in the boundary conditions have an important influence of the surface wave velocity. In addition, perturbation calculations are performed which include the influence of the spatial variation of all flexural biasing terms and it is shown that, for substrate thickness-to-wavelength ratios well within the practical range, the spatial variation in the biasing state has an appreciable effect on the velocity of acoustic surface waves.     

Equation for nonsteady-state combustion velocity of a powder

An integral equation is obtained for the nonsteady-state combustion velocity of a powder. It is shown that the effect of a variable tangential stream of gases on the rate of burning (nonsteady-state erosion) can be calculated in a similar way as for the change of pressure. The solution of the equation in linear approximation is considered (rate of burning differs slightly from steady-state).Translated from Zhurnal Prikladnoi Mekhaniki i Teknicheskoi Fiziki, No. 4, pp. 73–78, July–August, 1970.     

A method for calculating the two-dimensional temperature field of a reservoir with thermal injection

In [1–3] and other studies devoted to the determination of the temperature field of an oil reservoir when injecting into it a fluid with a temperature different from that of the initial reservoir temperature, the one-dimensional fluid flow (linear or radial) was considered in the case of an injection gallery or a single injection well in the reservoir. The problem was formulated in [4] with an arbitrary distribution of wells, but the solution was obtained only for the integral thermal-loss characteristic. To evaluate the coverage of the reservoir by the thermal effect, we must know the temperature distribution in the multi-well reservoir system at any instant of time. In this paper we propose a method for calculating the reservoir temperature field in the case of two-dimensional fluid flow using the simplifying assumptions which were used earlier by Lauwerier [1] and other authors to describe the thermal phenomena in a reservoir.     

Calculation of the discharge of underground explosion gases into the atmosphere

Nonstationary gas filtration from the cavity of a camouflaged underground explosion through a disaggregated porous medium is calculated. The computations were carried out for a spherically symmetric gas experiencing two-dimensional motion. A two-term law of filtration was used. The space-time pressure distribution of the gas within the medium was obtained. Motion hodographs of the front of filtration and the interface between the explosion products and air were constructed. The influence of the soil filtration characteristics and pressure in the cavity was investigated. The time at which gas is discharged into the atmosphere is determined based on well-known data on the permeability of certain types of rocks that have undergone the effects of an explosion. The variation of gas flow with time as a function of explosion depth is established.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 111–120, January–February, 1976.     

Strain-optic law for a certain class of birefringent composites

A strain-optic law for a certain class of birefringent fiber-reinforced composite materials is developed. The strain-optic law requires both mechanical and optical characterization of the material. Previous investigations have hypothesized the existence of three independent optical properties for the anisotropic birefringent material. The strain-optic relation developed in this study, however, requires only a single strain-optic coefficient, coupled with four independent mechanical material properties, for prediction of the optical response of a birefringent anisotropic material. Experimental results are presented which show good agreement with the developed strain-optic relation. Finally, the isoclinic parameter is investigated and preliminary evidence is presented which indicates a correspondence between principal-strain direction and optical isoclinic angle.     

Numerical simulation of the dynamics of an intense relativistic beam of charged particles

A method for the numerical simulation of stochastic processes in intense relativistic beams of particles moving in electric and magnetic fields is described. A two-dimensional approximation using coarse particles is considered. The action functions are first tabulated with respect to three variables. The method combines high speed and good accuracy. The results of a simulation are presented.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 61–66, November–December, 1973.