Instantaneous velocity profile in a wavy fluid film

Results of measuring the instantaneous velocity profiles in a laminar fluid film in the presence of stationary waves of different shape on its surface are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 3, pp. 399–404, September, 1977.     

Instantaneous optimal control with acceleration and velocity feedback

In the experimental demonstration of aseismic control systems, difficulties were encountered in the measurement of the displacement response of the structure. During earthquake ground motions, both the building and the ground are moving so that there is no absolute reference for the determination of the displacement response. An optimal control algorithm is proposed herein, which utilizes the measurements of acceleration and velocity responses rather than the displacement and velocity measurements. Such an optimal algorithm is developed based on the instantaneous optimal control theories, and it is evaluated and compared with other available optimal control laws. Numerical results indicate that the performance of the proposed optimal algorithm is as good as that of other optimal control laws currently available. However, the contribution of such an optimal control law to the practical implementation of active control systems for seismic hazard mitigations may be quite significant.     

Acceleration of Brownian particle diffusion parallel to a fast random field with a short spatial period

It is shown that a spatially periodic random field fluctuating rapidly near zero with a fairly small spatial period may substantially accelerate the diffusion of Brownian particles parallel to this field. Pis’ma Zh. Tekh. Fiz. 24, 9–15 (November 12, 1998)     

Determining the Instantaneous Effective Energy of x-Ray Tube Bremsstrahlung

A method is described for determining the instantaneous effective energy of x-ray tube brehmsstrahlung by means of two semiconductor detectors employing epitaxial GaAs structures and a measurement circuit, which together determine the effective energy with an error of 5% in the range 20–80 keV in the presence of nonlinearity in the detector response.     

Instantaneous velocity field measurements in unsteady gas flow by speckle velocimetry

An application of speckle photography techniques to unsteady gas flow measurements is presented. The instrumentation developed for the analysis of double-exposure photographs by digital signal processing is described. It is shown that 2-D velocity fields can be measured even when the flow is not perfectly 2-D. Accuracy and limitations of these techniques are discussed.     

Measurement of particle velocity in a two-phase jet by double-exposure speckle photography

Double-exposure speckle photography was used to measure the instantaneous particle velocity field in an intense high-velocity two-phase jet. Scientific Academic Complex “A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of elarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 2, pp. 224–229, March–April, 1996.     

Study of single particle charge and Brownian motions with surface plasmon resonance

We demonstrated a method to accurately measure the zeta potentials and surface charges of individual particles by surface plasmon resonance microscopy (SPRM). The principle is based on the sensitive dependence of surface plasmons in a metal surface on the distance between a particle and the surface. By applying a periodic (ac) electric field to the metal surface, the charged particle oscillates, which is measured with SPRM, from which the zeta potential and the surface charge of the particle can be determined. The ac method reduces the electro-osmotic effect and noises induced by Brownian motions and allows for the rapid determination of the zeta potentials of individual particles.     

Determination of particle velocity in a fluidized bed by the labeled atom method

The distribution of vertical and horizontal particle velocity in a fluidized bed has been investigated. The experimental results are presented below.     

Investigation of a double shrouded probe for particle sampling in high velocity airflows

An accurate forecast of the concentration of fine dust in the atmosphere is critical because of the negative public health impacts associated with high concentrations of particulate matter. To achieve an accurate forecast, large volumes of data need to be collected over a wide range of regions to act as forecast model boundary conditions. Therefore, the concentration of fine particles should be measured at both fixed observatories and from a range of moving monitoring stations, including cars, trains, and aviation vehicles. To accurately record particulate concentrations at flow velocities up to 200?km?h^?1, this study proposed a double-shrouded probe design based on the widely used single-shrouded probe. Using the double-shrouded probe, isokinetic sampling for PM_2.5 was achieved at velocities up to 200?km?h^?1, and for PM₁₀ at velocities up to 75?km?h^?1. When flow velocities exceeded these values and particle sizes increased, particulate concentrations were overestimated. However, as compared to the single-shrouded probe, the double-shrouded probe reduced the level of overestimation markedly.     

Energy and operation management of a microgrid using particle swarm optimization

This article presents an efficient algorithm based on particle swarm optimization (PSO) for energy and operation management (EOM) of a microgrid including different distributed generation units and energy storage devices. The proposed approach employs PSO to minimize the total energy and operating cost of the microgrid via optimal adjustment of the control variables of the EOM, while satisfying various operating constraints. Owing to the stochastic nature of energy produced from renewable sources, i.e. wind turbines and photovoltaic systems, as well as load uncertainties and market prices, a probabilistic approach in the EOM is introduced. The proposed method is examined and tested on a typical grid-connected microgrid including fuel cell, gas-fired microturbine, wind turbine, photovoltaic and energy storage devices. The obtained results prove the efficiency of the proposed approach to solve the EOM of the microgrids.     

Experimental study of fluctuations of particle velocity in a turbulent flow of air in a pipe

The distribution of longitudinal and normal components of the fluctuation velocity of particles in their motion in a downward turbulent airflow in a pipe is obtained. The effect of the concentration of particles on the intensity of fluctuations of their velocity is studied. A high rise of the longitudinal fluctuation of the velocity of particles in the pipe wall region with an increase in their concentration is revealed.     

Effect of a cylindrical shroud on particle conditions in high velocity oxy-fuel spray process

Simulations of solid particles in a highly compressible gas flow in the high velocity oxy-fuel (HVOF) process are presented. The Eulerian formulation is used for the gas flow, and the particl phase is modeled by the Lagrangian method. Effects of attaching a cylindrical shroud to the end of the supersonic HVOF nozzle on gas and particle flows are analyzed. We found that the shroud significantly reduces the oxygen content in the field by protecting the supersonic jet from ambient air entrainment. The validation experiments were performed for the majority of process parameters such as shock formation, particle conditions, and coating oxygen content.     

Potential accuracy of laser methods of measuring the particle velocity

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 23–26, June, 1989.     

Energy dissipation from particulate systems undergoing a single particle crushing event

The energy dissipation from particulate systems undergoing particle crushing is often assumed to scale solely with the increase in surface area, irrespective of the strain energy stored in the surrounding media. By analyzing idealized particulate systems undergoing a single particle crushing event, this assumption is questioned and proven invalid. Two analysis types are considered. One represents the particulate system as an idealized assembly and then represents particle contact forces as members belonging to a periodic lattice. The other treats the particulate system as an elastic continuum. Different sizes of two and three dimensional particulate systems are considered, as well as isotropic and anisotropic confining stress states. The overall dissipation is shown to depend strongly on the dimensionality of the system, the anisotropy of the confining stress state and the elastic properties of the system. The ratio between dissipation due to stored elastic energy redistribution from surrounding media and dissipation by fracture surface energy is calculated. The ratio is found to diminish with the increasing dimensionality of the system. It is also shown that this ratio is independent of the fracture surface energy of the material. The most relevant analysis of a three dimensional particulate system to accurately estimate this ratio seems to be a one dimensional analysis of the force chain containing the most heavily loaded particles.     

A generalized particle algorithm for high velocity impact computations

 This paper presents a Generalized Particle Algorithm (GPA) for high velocity impact and other dynamics problems. A velocity smoothing algorithm is also presented. This generalized algorithm allows for both variable nodal connectivity and fixed nodal connectivity. The variable connectivity option allows for severe distortions with a Lagrangian approach. With fixed nodal connectivity and smoothing it is possible to provide stable computations for large tensile strains. The algorithms are provided for 2D axisymmetric geometry and 3D geometry, and examples are included to demonstrate some of the capabilities. A discussion of interface problems and solutions is also included.     

Identification of linear systems captured in a feedback loop

The identification of model parameters using measured input-output data from linear systems operating in a closed loop is discussed. A frequency-domain maximum likelihood estimator which takes into account the correlation between the input and output disturbances is presented. Its properties are analyzed and illustrated by simulation examples and real measurements     

The relation between stress and particle velocity for Rayleigh pulses

Summary In this note, the relationship between the stress and the particle velocity for Rayleigh pulses which propagate along a free surface of an elastic isotropic half-space is discussed.Dedicated to Prof. Dr. Dr. h. c. Franz Ziegler on the occasion of his 60^th birthday