Effect of ambient density and orifice diameter on gas entrainment by a single-hole diesel spray

The gas entrainment into a non-vaporizing single-hole Diesel spray submitted to variable density is studied experimentally in order to better understand the effect on mixture formation. Particle Image Velocimetry on fluorescent tracers has been applied to obtain measurement in the flow field surrounding the spray. The “quasi-steady” region of the spray (far from the head vortex) as well as the non-stationary region has been investigated. Significant effects of both ambient density and nozzle diameter on gas entrainment have been pointed out.     

Motion of a shock wave through a gas of variable density

A successive approximation method is used to solve the self-similar problem of gas flow accompanying a shock wave propagated through a polytropic gas of variable density. The method is based on a special choice of independent variables and the use of Whitham's approximation [1] as the initial approximation for the motion of the discontinuity. A first approximation for the self-simulation index is calculated which is in good agreement with exact values.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 68–72, September–October 1970.The author wishes to thank S. V. Fal'kovich for suggesting this problem and for his help in the work.     

Yttria-stabilized-zirconia hollow spheres prepared by atmospheric plasma spray

Yttria-stabilized-zirconia （YSZ） hollow spheres are widely utilized for their novel physical and chemical properties. However, developing a simple and low-cost method for preparing such hollow spheres still remains a great challenge. In this paper, an atmospheric plasma spray （APS） method is introduced, and the formation mechanism of hollow 7YSZ （ZrO2-7wt%Y2O3） spheres is presented. The hollow sphere morphology was observed by scanning electron microscopy （SEM） when agglomerated and sintered 7YSZ powders were used. Additionally, additive composition changes, phase transformations, and the thermal behavior of 7YSZ powders were analyzed by energy dispersive spectroscopy （EDS）, X-ray diffractometry （XRD）, thermogravimetric analysis （TG） and differential scanning calorimeter analysis （DSC）. Furthermore, the phase transformations of agglomerated and sintered 7YSZ powders, 7YSZ hollow spheres that annealed at various temperatures for different times are analyzed.     

Yttria-stabilized-zirconia hollow spheres prepared by atmospheric plasma spray

Yttria-stabilized-zirconia (YSZ) hollow spheres are widely utilized for their novel physical and chemical properties. However, developing a simple and low-cost method for preparing such hollow spheres still remains a great challenge. In this paper, an atmospheric plasma spray (APS) method is introduced, and the formation mechanism of hollow 7YSZ (ZrO₂-7wt%Y₂O₃) spheres is presented. The hollow sphere morphology was observed by scanning electron microscopy (SEM) when agglomerated and sintered 7YSZ powders were used. Additionally, additive composition changes, phase transformations, and the thermal behavior of 7YSZ powders were analyzed by energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD), thermogravimetric analysis (TG) and differential scanning calorimeter analysis (DSC). Furthermore, the phase transformations of agglomerated and sintered 7YSZ powders, 7YSZ hollow spheres that annealed at various temperatures for different times are analyzed.     

Experimental study of density fluctuations in a hypersonic laminar wake behind a cone

The characteristics of natural fluctuations of density in a laminar near wake behind a sharp cone in a hypersonic flow of nitrogen at zero incidence are studied by the method of electronbeam fluorescence at Mach numberM=21 and unit Reynolds numberRe ₁=6·10⁵ m⁻¹. The distributions of the mean density, integral fluctuations, and spectra of density fluctuations are obtained, the longitudinal and azimuthal phase velocities of perturbations are determined, and the growth rates of perturbations in the wake are found. The results are compared with the measurement data in the shock layer on a flat plate. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 3, pp. 111–117, May–June, 2000     

Determination of soil density by cone index data

In this paper a novel soil-density determination method is presented. The classic method (sampling, drying, mass measuring, etc.) can give proper results for the given problem but the standard methodology requires a lot of practical effort. While the soil is generally inhomogeneous, the measured density values of the soil sample applies only for the sample itself. On the entire soil territory this density can be interpreted only with significant errors. For a better mapping of the soil-density distribution expansive measurements are required. The task is complicated by the determination of density distribution in deeper layers of the soil as well. Our work presents a simpler method to determine the soil-density distribution in deeper layers with the use of cone penetration test (CI) results. With this method we can obtain detailed results of the soil-density distribution in deeper layers that may help further calculations for soil deformation analysis such as an exact determination of the soil sinkage below a tire track.     

Liquid and gas entrainment to a small break hole from a stratified two-phase region

A theoretical and experimental study has been conducted for liquid and gas entrainment to a small break hole from a stratified two-phase region. Theoretical correlations previously obtained for top, side and bottom entrainment were modified to express the relation between break flow rate, break quality and bulk water level so that they can be used easily for any break geometry. The modified correlations were assessed with experimental data obtained under room temperature and low pressure conditions using air and water. The experiment results were predicted well with the present model without using any adjustment coefficient when the upstream flow was symmetrical around the break. The effects of vortex, crossflow and wavy flow, observed in the experiment but not taken into account in the model, were empirically correlated based on the present correlation. By using the empirically modified correlations, the data in the literature, including high-pressure steam-water conditions, were reasonably predicted.     

Influence of a strong density stratification on the entrainment of a turbulent axisymmetric plume

The effect of entrainment and the role of the interface during the interaction between an axisymmetric turbulent mass plume and a strong stratified layer are investigated. We describe mainly the characteristics of the plume: the change in the profiles of the density, the horizontal component of the velocity and the corresponding intensity of turbulence, the change in the entrainment co-efficient, when the plume goes through the impingement interface, assuming a self-similar Gaussian property of the axial velocity component and of the density difference. The influence of the stratification on the plume angle coefficient is studied, and compared with the results related to a homogeneous environment, obtained elsewhere. Experimental correlation on the mean entrainment coefficient in a given plume cross-section, is formulated.     

Drag of a slender cone in a supersonic rarefied gas flow

On the basis of an analysis of experimental data, obtained by the authors or taken from the literature, on the drag of a slender cone with half-angle =2.5–20° an average correlation curve is proposed for the range of flow regimes extending from continuum to free molecular flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 187–189, January–February, 1987.     

Thermal stresses in a sector of a hollow cylinder having variable elastic properties

International Applied Mechanics -     

Torsion of hollow cylinder with variable shear moduli

Kiev Institute of Civil Aviation Engineers, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 29, No. 11, pp. 41–46, November, 1993.     

Joule loss due to compressibility of gas in a channel of variable section

It is known that closed electric currents arise in a conducting medium moving in a non-uniform magnetic field. These currents lead to additional energy loss and adversely affect the characteristics of magnetohydrodynamic channels. (The numerous investigations of these effects are dealt with in the review [2, 3].) Eddy electric currents are also formed, however, when a medium flows in a uniform magnetic field perpendicular to the to the plane of motion if the channel has a variable cross section and the medium is compressible [1], This paper is devoted to an investigation of some features of these flows. It is assumed in the analysis that the gas flows in channels whose geometry varies slightly.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 9, No. 4, pp. 3–9, July–August, 1968.     

Gas jets in fluidized beds: The influence of particle size,shape and density on gas and solids entrainment

Gas has been injected in two-dimensional fluidized beds of solids different in size, density and shape. The ranges of solids sizes and bed heights were such as to produce relatively steady permanent jets.The mechanics of dispersion of these jets has been studied measuring jet angles, jet gas and solids velocity profiles, and particle entrainment velocities. The proportions of total mass and momentum flowrates pertaining to gas and solids have been calculated from these data.     

Theoretical and experimental studies on the coefficient of discharge and spray cone angle of a swirl spray pressure nozzle using a power-law non-Newtonian fluid

An extension of earlier work is made in the present paper to determine both theoretically and experimentally the coefficient of discharge and spray cone angle of a swirl nozzle using a time-independent purely viscous power-law non-Newtonian fluid. The theoretical predictions are made through an approximate analytical solution of the hydrodynamics of flow inside the nozzle. Experiments are carried out with aqueous solutions of CMC (carboxymethyl cellulose sodium salt) powder of various concentrations as the working fluids. The rheological properties of the working fluids are established by a capillary tube viscometer. From both the theoretical and experimental analyses, the pertinent independent input parameters are recognised as the generalised Reynolds number at inlet to the nozzle Re_Gi, the flow behaviour index of the fluid n, length-to-diameter ratio of the swirl chamber L₁/D₁, spin chamber angle 2α and the orifice-to-swirl-chamber-diameter ratio D₁/D₁. Although the theory predicts the correct qualitative trend in all cases, it does not agree well with the experimental results. Therefore, on the basis of the theoretical results, emperical relationships between nozzle characteristics and input parameters heve been established. Finally it is recognised that, regarding the injection conditions and fluid properties, the generalised Reynolds number at nozzle inlet Re_Gi and the flow behaviour index n have inverse and direct effects, respectively, on the coefficient of discharge, but have a negligible influence on the spray cone angle. Amongst the nozzle geometries, an increase in the values of D₂/D₁ and 2α or a decrease in the value of L₁/D₁ decrease the coefficient of discharge and increase the spray cone angle.     

Particle image velocimetry in a variable density flow: application to a dynamically evolving microburst

A fondamental difficulty in the experimental study of gravity-driven flows using particle image velocimetry (PIV) and other optical diagnostic techniques is the problem associated with variations in thé refractive index within the fluid. This paper discusses a method by which the refractive indices of two fluids are matched while maintaining density differences of up to 4%. Aqueous solutions of glycerol and potassium phosphate are used to achieve precise index matching in the presence of mixed and unmixed constituents. The effectiveness of the method is verified in a PIV study of a laboratory-scale model of an atmospheric microburst where planes of two-dimensional velocity vectors are obtained in thé evolving flow field.This work was sponsored by the National Science Foundation under grant CTS-9209948. We also thank TSI, Inc. for the use of its facility     

A preliminary laboratory study of the lateral entrainment of non-local waters by a subsurface mesoscale eddy

Most previous studies of mesoscale variability in the ocean have emphasized that rings and eddies are isolated vortices embedded in relatively homogeneous water. Recent observations of eddy systems in the California Current System (CCS), however, show that at least some CCS eddy systems continue to dynamically interact with inshore coastal (cold) and offshore (warm) waters of the California Current through the process of lateral vortex entrainment. Oceanic data suggest that lateral vortex entrainment of non-local waters with significantly different temperature and salinity characteristics may partially account for the presence of high shear mixing regimes, double diffusive phenomenon and secondary circulations at depth in the vicinity of the eddies. Two different sets of laboratory experiments were conducted to assess the kinematic possibility of lateral vortex entrainment as a generation mechanism for these oceanic phenomena. The results of the laboratory studies qualitatively support the conclusion that lateral vortex entrainment could produce at least some of the observed oceanic phenomena.     

Influence of magnetic field and thermal radiation by natural convection past vertical cone subjected to variable surface heat flux

A numerical study is performed to examine the heat transfer characteristics of natural convection past a vertical cone under the combined effects of magnetic field and thermal radiation.The surface of the cone is subjected to a variable surface heat flux.The fluid considered is a gray,absorbing-emitting radiation but a non-scattering medium.With approximate transformations,the boundary layer equations governing the flow are reduced to non-dimensional equations valid in the free convection regime.The dimensionless governing equations are solved by an implicit finite difference method of Crank-Nicolson type which is fast convergent,accurate,and unconditionally stable.Numerical results are obtained and presented for velocity,temperature,local and average wall shear stress,and local and average Nusselt number in air and water.The present results are compared with the previous published work and are found to be in excellent agreement.     

Theoretical analysis of the onset of gas entrainment from a stratified region through multiple branches

A theoretical analysis has been developed to predict the critical height of the onset of gas entrainment (OGE) during dual and triple discharge from a stratified two-phase region. The two and three discharge branches are mounted on a circular wall, resembling a circular reservoir of a CANDU header–feeder configuration. A point sink model has been developed to predict the critical height and to map the velocities and acceleration flow fields during OGE. The model was verified by comparing the theoretically predicted critical height with the available experimental results. The theoretically predicted critical height is found to be a function of the branch Froude number, the location of the secondary branch with respect to the primary branch, and the angle between the branches. The effect of these variables on the predicted OGE height was investigated and is presented in this paper. Predictions of the critical height were shown to be within 25% of experimental values in both dual and triple discharge.