Flow-induced structure in a system of nuclear waste simulant slurries

Thixotropy and antithixotropy were characterized in nuclear waste simulant slurries. For the neutralized current acid nuclear waste (NCAW) simulant slurries, NCAW with glycolic acid (NCAW+GA), and NCAW with nitric acid (NCAW+NA) (pH 4), a pre-shear flow at constant shear rate destroys the aggregates in the suspension and reduces viscosity. For the NCAW+NA (pH7–9), a pre-shear enhances the aggregates in the suspension and increases viscosity. With the addition of silica to the NCAW+GA and NCAW+NA slurries, the pre-shear effect tends to promote aggregation due to the formation of a network in the suspension, and hence, the viscosity increases. The macroscopic rheological property variation due to the microstructural aspects of the suspensions associated with the shear-induced effect are addressed.     

Phase-stepped ESPI and moiré interferometry for measuring stress-intensity factor andJ integral

Electronic-speckle-pattern interferometry and moiré interferometry have been used to calculateK ₁ andJ for compact tension specimens. Automated-fringe-pattern analysis enables the full-field of data to be used with the minimum of operator intervention. Measurements are shown to be accurate to within 10 percent. TheJ-measurement procedure employed could form the basis of an automatic-fault detection system.     

Modeling of the dynamics of the change in the index of refraction during resonance interaction of radiation with vibrational-rotational transitions

Moscow. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 1, pp. 21–29, January–February, 1994.     

Numerical analysis of the asymptotic representation of solitary waves

Novosibirsk. Translated from Prikladnaya Mekhanika i Technicheskaya Fizika, No. 5, pp. 44–54, September–October, 1994.     

Optimal control of a spacecraft with a solar sail

Analysis of the results indicates that:

Mixing quantification by visual imaging analysis

This paper reports on development of a method for quantifying two measures of mixing, the scale and intensity of segregation, through flow visualization, video recording, and software analysis. This non-intrusive method analyzes a planar cross section of a flowing system from an instantaneous data record, thereby eliminating the need for statistical analysis of a large number of point measurements at multiple locations throughout the system to characterize the mixing. The method is applied to a cold flow model of a high temperature, gas/solid reactor so that reactor design and operation can be optimized to promote reaction efficiency. This method may be useful for studying a variety of mixing systems in which multiphase components or tracers are visually distinguishable.List of symbols mixing coefficient (defined by Eq. (17)) - standard deviation - a mixing coefficient (defined by Eq. (16)) - C(k, m) sample grayscale covariance (defined by Eq. (3)) - d distance (defined by Eq. (8)) - D divisor (defined by Eq. (3)) - d ^* value of d for which R _I (d) approaches zero - D ₅₀ mass median diameter - I intensity of segregation (defined by Eq. (20)) - M sample size (defined by Eq. (16)) - n number of contiguous pixels - n ^* value of n for which SSE _Q /SSE _L is maximized - n _c number of columns of pixels - N_R number of rows of pixels - P number of pixels per linear distance - r radius of Cold Flow Model - R(k, m) sample correlation function (defined by Eq. (5)) - R _C (k) column correlation function (defined by Eq. (7)) - R _I (d) isotropic correlation function (defined by Eq. (9)) - R _R (m) row correlation function (defined by Eq. (6)) - SSE _Q residual sum of squared errors from the least squares fit of the quadratic model to Eq. (14) - SSE _L residual sum of squared errors from the least squares fit of the linear model to Eq. (14) - S _y ² sample grayscale variance (defined by Eq. (2)) - S _c column scale of segregation (defined by Eqs. (7) and (13)) - S _D Danckwerts' scale of segregation (defined by Eq. (10)) - S _R row scale of segregation (defined by Eqs. (6) and (13)) - S _s scale measure developed in this paper (defined by Eq. (13)) - V _n sample variance of contiguous pixels (defined by Eq. (11)) - V _n ^* normalized variance function (defined by Eq. (12)) - sample grayscale mean (defined by Eq. (1)) - Y _i,j grayscale value at pixel (i,j)     

Excitation of velocity fluctuations and noise in a wind tunnel

The aim of this paper is to develop a theory, consistent with the observations, of the nature and location of the structures that determine self-excitation and the emission of the narrow-band components of the noise generated by the open working section of wind tunnels. At the same time, the theory is applied by using it as a basis for constructive solutions.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.4, pp. 165–173, July–August, 1992.     

Some recent developments in vehicle—terrain interaction studies

This report presents a review of recent developments in the study of vehicle3-terrain interaction, based primarily on papers included in Session 2A of the 10th International Conference of ISTVS. Analytical studies of wheel-soil interaction using visco-elastic soil models and elasto-plastic and rigid-plastic finite element methods are reviewed. Results of experimental investigations of stress distributions on the wheel-soil interface as well as in the soil under various loading conditions are summarized. Various methods for predicting off-road vehicle performance are examined.     

Orienting properties of discotic nematic liquid crystals in Jeffrey-Hamel flows

The orienting properties of incompressible discotic nematic liquid crystals for creeping flows between converging and diverging planar walls (Jeffrey-Hamel) are analyzed using the Leslie-Ericksen theory. The dependence of director orientation on the reactive parameter and the flow kinematics is presented. Closed form stationary solutions for the director orientation are found when elastic effects are neglected. Stationary numerical solutions for the velocity and director fields using the full Leslie-Ericksen theory are presented. The director field in converging flow is characterized by azimuthal (radial) centerline orientation, by being asymmetric with respect to the azimuthal (radial) direction, and by having an allowed orientation range that spans two half-quadrants (full quadrants). In the limiting case of perfectly flat disk ( –) the flow-induced director orientation in converging flow is the azimuthal direction, while in diverging flow the director rotates by a full n radians. By reducing the vertex angle between the walls to vanishingly small values, converging flow solutions properly reduce to those of flow between parallel plates, but diverging flows are expected to lead to a new instability.