Particle Velocity Measurements Research Articles

Measurements of particle velocity and solid concentration near the wall of a cyclone using high-speed particle shadow velocimetry

The particle velocity and solid concentration distribution in the near-wall region of a cyclone separator was experimentally studied. A series of measurement experiments were conducted based on the high-speed particle shadow velocimetry (HPSV) method. The experiment was conducted on a ϕ160 mm cyclone at an inlet velocity of 12-20 m/s and inlet concentration of 30-300 g/m3 with glass beads whose median diameter was 136.7 μm. The measured results of the microscopic particle movement demonstrate the moving behavior of the spiral particle band near the cyclone wall. It was found that the particle velocity and solid concentration are greatly different from those in and outside the particle band. The particle velocity inside the particle band can drop to 1.9 m/s, while the dispersed particle velocity outside the particle band away from the wall can reach 15.2 m/s. Along the downward movement of particle band, the particle velocity decrease and velocity fluctuation become milder, the solid concentration increases four times and reaches the highest at the cone wall. On the cross-section plane, the solid concentration decreases along the radial direction away from the wall. In the near-wall region inside particle band, the solid concentration can reach 0.004 or even higher, which is 32 times higher than the inlet solid concentration. This study helps to understand the complex gas-solid two-phase flow phenomena in cyclones.

Compressive equivalent source method based on particle velocity measurements for near-field acoustic holography

In order to solve the problems of spatial resolution limit and reduce the measurement cost, the compressive sensing theory and the sparse regularization are applied to the near-field acoustic holography (NAH) technology. In the previous works, the Equivalent Source Method (ESM)-based NAH has been extended in the sparsity framework by sampling the sound pressure signals sparsely. However, this Compressive ESM (CESM) mode would suffer from the low precision problem in the particle velocity reconstruction. To improve the reconstruction accuracy of the particle velocity, this paper is going to take the sparse particle velocity as the input of NAH to establish a new CESM mode based on the particle velocity measurement. In the meantime, the number of sampling points will be reduced greatly without losing the reconstruction accuracy when compared to the conventional ESM with the Tikhonov regularization based on the particle velocity measurement. Several numerical simulation experiments have been carried out to examine the performance of the proposed model. The results show that the proposed model delivers a satisfactory performance in the reconstruction of both the pressure and particle velocity on the condition that the number of sampling points is much smaller than that of the conventional ESM, and the proposed model performs much better than the existing CESM mode based on the sound pressure measurement especially when reconstructing the particle velocity.

Shock and Spallation Behavior of a Compositionally Complex High-Strength Low-Alloy Steel under Different Impact Stresses

The shock and spalling behavior of a compositionally complex high strength low-alloy steel (HSLA) was studied using plate impact testing. The free surface velocity of the specimen in the range of 194~938 m/s was measured by a displacement interferometer system for any reflector (DISAR). The Hugoniot elastic limit (HEL), spallation fracture and microstructural evolution of the HSLA under an impact stress of 3.04~18.66 GPa were analyzed. Shock Hugoniots were obtained from the measured particle velocities and calculated shock velocities. The velocity curves show clear signs of HEL and velocity fallback, indicating a transition from elastic to plastic and spalling behavior. When the impact velocity exceeds 757 m/s, the particle velocity rises to the peak and then increases again, indicating that an α→ε phase transition occurred, with a threshold of 13.51 GPa. It was found that the impact velocity is linearly related to the particle velocity of the HSLA. As the impact stress increased, the HEL remained within the range of 1.32~1.50 GPa, while the spalling strength presented an upward trend with the increasing impact stresses. Metallographic analysis shows that the impact failure is dominated by brittle fracture at lower velocities, while more ductile fracture occurs at higher velocities.

Shear wave elastography: From dispersion matching to full waveform inversion

Shear Wave Elastography (SWE) involves estimating mechanical properties through inversion, i.e., matching measured and simulated propagation characteristics of shear waves in the tissue. The accuracy of the estimated properties depends significantly on the specific characteristics/responses that are being matched. These could range from simple group velocity to dispersion curves and to full-wave response (particle velocity measurements). Using specific applications of arterial, liver, and tumor elstography, we illustrate that effective SWE is performed by resorting to an inversion approach, or combination of inversion approaches, guided by the underlying physics. To this end, we present inversion approaches ranging from matching dispersion characteristics to matching full waveform responses and provide rationale for choosing the appropriate technique(s) depending on the problem at hand.

Robust filtering of ghost and peg-leg from sea floor seismic data

ABSTRACT. The processing of compressional waves from the acoustic components of ocean bottom seismic data is performed decomposing the compressional wavefield on its upgoing an downgoing components, treating the first order multiples, composed by the overlap between the receiver ghost and peg-leg. The separation of these wavefields is achieved through the adaptive summation of the hydrophone and geophone components, usually on a least square sense. This method of separation is known as PZ summation, because it involves an operation between pressure and vertical particle velocity measurements. However, due to the difference in response of the pressure and velocity sensors, the premises assumed on the least square summation can be violated, degrading the results. To overcome these difficulties, a more robust method can be achieved using the L1 norm criterion for the adaptive sum. A comparison was made between the results obtained with the Iterative Reweighted Least Squares and Wiener-Levinson filters. The robustness of the L1 norm sum was demonstrated by applications on PZ summation of Ocean Bottom Cable data from the Jubarte area, in the Campos Basin, Brazil, showing improvements, especially when the multiples are present in the estimation window used to derive the filter coefficients.

Velocity measurement of pneumatically conveyed particles via a simple current signal technique and the influence of electrostatic charge

Particle velocity in pulse feeding pneumatic conveying was measured utilizing current signal analysis and video imaging. Glass beads and silica particles were conveyed in a conductive tube (ID of 4.57 × 10 −3 m) at gas velocities of 7, 15, and 30 m/s. To measure particle velocity, electrical current signal method was used with a new approach that uses raw current data and eliminates signal conditioning and cross-correlation analysis. This technique was successful and results were comparable to video imaging results. The conveyed particles' charge was measured to determine its influence on particle velocity. 30 m/s gas velocity resulted in a turbulent flow and greater charge generation causing more deviations between particle and gas velocity due to the enhancement of particles' radial motion. Finally, the comparison of results with predictions of existing models revealed that further research is necessary to better understand the effect of particles' motion and charge on their conveying velocity. Video imaging and current signal measurement techniques and the acquired electrostatic charge during pneumatic conveying. • Particle velocity in pneumatic conveying was measured based on particles charge. • A simplified technique based on electrical current signal method was proposed. • Influence of particles electrostatic charge on their velocity was investigated. • Existing models overestimated particle velocity in the presence of electrostatics. • Existing models predictions were not in agreement to the measurements at high gas velocities.

Experimental investigation of shock response to an insensitive explosive under double-shock wave

A new integrated velocimetry system that includes terahertz-wave-based Doppler velocimetry (TDV) and a multiplied electromagnetic particle velocity gauge (EMV) is demonstrated by measuring the particle velocity history and the corresponding shock-to-detonation transition (SDT) distance in double-shock experiments of insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-2. This system overcomes the defects in resolution, testing distance, particle velocity measurement history, and shock-wave capture when TDV or EMV are used separately in double-shock experiments. The effectiveness of the integrated velocimetry system is verified via double-shock experiments, and the deviation of shock wave displacement is less than 6%. Furthermore, the desensitization effects of TATB-2 are determined by comparing the initiation behavior for the double-shock and sustained-pulse experiments. Results indicate that the longer the time of the unreactive preshock wave, the stronger the desensitization effects. Further, the reactive main shock wave in the double-shock experiment can weaken the desensitization effects of the double-shock wave.

3D particle sizing, thermometry and velocimetry of combusting aluminized propellants

Due to the unique advantages of high specific impulse, high thrust, simplicity and reliability, solid propellant with metal powder additives has emerged as a promising energy carrier for rockets in aerospace engineering. In-situ characterization of the metal particle combustion is crucial for the validation of numerical models and optimization of the propellant formulas. Previous studies mainly focused on the measurement of particle size and velocity near the combusting propellant surface with holography. Whereas, the behavior of the particles away from the surface is also essential for the full understanding the combustion and agglomeration mechanisms. Nevertheless, holography suffers from inaccurate depth estimation due to the large depth-of-focus. To overcome this limitation, a hybrid method which combines three-dimensional (3D) fiber optic imaging with two-color pyrometry is developed to realize simultaneous 3D localization, velocimetry, sizing, and thermometry of combusting aluminum particles in a large field of view. The method is validated both with numerical studies and experiments for a field of view of ∼60 × 50 × 50 mm3. According to the experimental results, the particle size follows a log-normal distribution which agrees with the specification of the propellants. In addition, the evolution of particle temperature and velocity were recorded for a duration of ∼13.9 ms. The results suggest that the temperature of most particles were between 2000 and 3500 K, while particle velocities were between 1 and 10 m/s. The measurement method proposed here is promising for the quantitative analysis of the complicated combustion process of aluminized propellants.

Onset and dynamics of avalanches in a rotating cylinder: From experimental data to a geometric model.

Particle image velocimetry has been applied to measure particle velocities on the free surface of a bed of particles within a rotating cylinder during avalanching. The particle velocities were used to examine the validity of existing avalanche models and to propose an alternative model. The movement of particles depends on their location on the surface of the bed: Particles located near the center of the bed travel the farthest, while the distance traveled decreases at an increasing rate for particles located farther from the center. The start of an avalanche can be determined to a single initiation point that can be located on the bottom half of the bed; the avalanche quickly propagates through the entire free surface with 90% of the surface in motion within 257 ms (approximately 20% of the total duration of an avalanche). The experimental insight is used to formulate a geometric model, in which three equal-sized sections flow down the bed surface during an avalanch. The predictions of the model are validated by experimental mixing measurements.

Comparative study of the single and double specularity coefficients on two-fluid modeling of a pseudo-2D gas–solid fluidized bed

The specularity coefficient is an unmeasurable parameter in the most popular wall boundary model during the two-fluid modeling of dense gas–solid flows. Using multiphaseEulerFoam solver, the influence of different specularity coefficient setting strategies on the gas–solid flow inside a pseudo-2D fluidized bed has been explored. It is found that the single specularity coefficient plays a regulatory role in the quantitative prediction. Increasing the specularity coefficient would cause a fluidization transition from freely bubbling to slugging, and the bed characteristics such as pressure drop and bed expansion present monotonic nonlinear changes. The double specularity coefficients approach is shown to significantly improve the predictive accuracy through verifying with the measured particle velocities, bubble diameter and rise velocity. In addition, the lognormal bubble size distribution and Gaussian bubble rise velocity distribution are observed. The specularity coefficient for walls in thickness direction is crucial and its different effects are unignorable. Overall, the present study provides a practical strategy of double specularity coefficients for the solid wall boundary conditions during two-fluid modeling.

Investigation on direct measurement method of particle velocity in the plume for intelligent laser welding-oriented

The dynamic plume behavior is one of the key features that allows one to obtain the required information for monitoring the process quality of the intelligent laser welding. This paper proposed a method of directly measuring particle velocities in plume induced in fiber laser keyhole welding based on the self-mixing interferometry (SMI) effect. This method was verified by measuring tiny metal objects with known sizes and velocities. The particle velocities can be calculated according to the number of SMI fringes induced by the particles, and the temporal data. To measure the diameters of particles, it is expedient to use a detection laser with a spot diameter larger than that of particles. A smaller diameter of the detection laser spot will result in more accurately measured values of particle velocities. A direct measurement was conducted to assess the particle velocities in the plume induced in fiber laser keyhole welding. These particles in plume had a velocity of 1.9–90 m/s, and more than 45% of these particles had a velocity of 10–60 m/s. Particles with larger diameters were more likely to have higher velocities.

A new woven composite constitutive model validated by shock wave experiments

In this paper, we present results of plate impact simulations of shock compressed woven glass fiber-reinforced plastic (GRP) performed using the Arbitrary Lagrangian–Eulerian three-dimensional finite element code. A hyperelastic large-strain-based empirical Continuum Damage Mechanics (CDM) formulation is employed to describe damage initiation and growth in the shock-compressed GRP. The model parameters calibration scheme utilizes the Velocity Interferometer System for Any Reflector normal particle velocity measurements at the free surface of the GRP target plates. The impact velocity in the experiments ranged from 8.5 to 418 m/s. The finite element model considered planar 0°/90° bidirectional plies with an individual ply thickness of 0.68 mm, stacked to reach a total laminate thickness of 6.8 mm. The anisotropic elastic strains were estimated from the experimentally determined tetragonal symmetry stiffness matrix for the GRP. The strain-based damage model captures several salient features observed in the measured free surface particle wave profiles, including the shock rise time, onset of Elastic—Elastic Cracking, and the shape of the nonlinear portion of the experimental particle velocity profiles. The CDM model predicts the dominant damage mode to be matrix microcracking due to shear and the associated bulk expansion (bulking) under the global compressive loading in the plate impact configuration.

Dynamics and Near‐Field Surface Motions of Transitioned Supershear Laboratory Earthquakes in Thrust Faults

AbstractWe study how the asymmetric geometry of thrust faults affects the dynamics of supershear ruptures and their associated trailing Rayleigh ruptures as they interact with the free surface, and investigate the resulting near‐field ground motions. Earthquakes are mimicked by propagating laboratory ruptures along a frictional interface with a 61° dip angle. Using an experimental technique that combines ultrahigh‐speed photography with digital image correlation, we produce sequences of full‐field evolving measurements of particle displacements and velocities. Our full‐field measurement capability allows us to confirm and quantify the asymmetry between the experimental motions of the hanging and footwalls, with larger velocity magnitudes occurring at the hanging wall. Interestingly, because the motion of the hanging wall is generally near‐vertical, while that of the footwall is at dip direction shallower than the dip angle of the fault, the horizontal surface velocity components are found to be larger at the footwall than at the hanging wall. The attenuation in surface velocity with distance from the fault trace is generally larger at the hanging wall than at the footwall and it is more pronounced in the vertical component than in the horizontal one. Measurements of the rotations in surface motions confirm experimentally that the interaction of the rupture with the free surface can be interpreted through a torqueing mechanism that leads to reduction in normal stress near the free surface for thrust earthquakes. Nondimensional analysis shows that the experimental measurements are consistent with larger‐scale numerical simulations as well as field observations from thrust earthquakes.

An Acoustic Sea Glider for Deep-Sea Noise Profiling Using an Acoustic Vector Sensor

Abstract An acoustic sea glider has been developed for ambient sea noise measurement and target detection through the deployment of an acoustic vector sensor (AVS). The glider was designed with three cabins connected in sequence and it can dive to depths exceeding 1200m. The AVS fixed on the glider measure acoustic pressure and particle velocities related to undersea noise, and the inner attitude sensors can effectively eliminate the estimation deviation of the direction of arrival. The inherent self-noises of the acoustic sea glider and AVS are presented respectively in respect to the Knudsen spectra of sea noise. Sea trial results indicate that the AVS could work well for undersea noise measurement when the glider is smooth sliding, and the target azimuth estimated by AVS after correction is remarkably consistent with the values measured by the GPS, and direction-finding errors are less than 10 degrees. The research in this paper shows that the acoustic sea glider is able to undertake tasks such as a wide range of underwater acoustic measurement and detection.

Microfluidic Rheometry and Particle Settling: Characterizing the Effect of Polymer Solution Elasticity.

The efficient transport of solid particles using polymeric fluids is an important step in many industrial operations. Different viscoelastic fluids have been designed for this purpose, however, the effects of elasticity have not been fully integrated in examining the particle-carrying capacity of the fluids. In this work, two elastic fluid formulations were employed to experimentally clarify the effect of elasticity on the particle drag coefficient as a proxy model for measuring carrying capacity. Fluids were designed to have a constant shear viscosity within a specific range of shear rates, , while possessing distinct (longest) relaxation times to investigate the influence of elasticity. It is shown that for dilute polymeric solutions, microfluidic rheometry must be practiced to obtain a reliable relaxation time (as one of the measures of viscoelasticity), which is on the order of milliseconds. A calibrated experimental setup, furnished with two advanced particle velocity measurement techniques and spheres with different characteristics, was used to quantify the effect of elasticity on the drag coefficient. These experiments led to a unique dataset in moderate levels of Weissenberg numbers, . The data showed that there is a subtle reduction in the drag coefficient at low levels of elasticity (), and a considerable enhancement at high levels of elasticity (). The experimental results were then compared with direct numerical simulation predictions yielding . These evaluations endorse the numerically quantified behaviors for the drag coefficient to be used to compare the particle-carrying capacity of different polymeric fluids under different flow conditions.

Measurement of Particle Velocity, Particle Size Distribution, and Particle Volume Fraction in Two-Phase Flow Using Transmission Fluctuation Correlation Spectrometry

Measurement of Particle Velocity, Particle Size Distribution, and Particle Volume Fraction in Two-Phase Flow Using Transmission Fluctuation Correlation Spectrometry

Measurement of Particle Velocity, Particle Size Distribution and Concentration in Particulate Suspension by Transmission Fluctuation Correlation Spectrometry

In coal-fired power generation industry, parameters such as particle size affect combustion efficiency. Especially in the application of two-phase flow clean energy, the parameters such as particle velocity, particle size distribution and concentration are very important, because the coal particle velocity, concentration or size range have an impact on the whole combustion process. This paper introduces an optical measurement setup based on the transmission fluctuation correlation spectrum measurement technique, which realizes the simultaneous measurement of particle velocity, particle size distribution and concentration. Compared with image method, ultrasonic spectrum method and other methods, the experimental device is simple and low-cost.

An Approach for Reconstructing the Time-Dependent Force Acting on a Thin Plate from Particle Velocity Measurements

An Approach for Reconstructing the Time-Dependent Force Acting on a Thin Plate from Particle Velocity Measurements

Design of an Electromagnetic Particle Velocity Measurement System Based on Superconducting Magnet

The electromagnetic particle velocity measurement technology is an important measurement method in the study of stress wave propagation. This paper analyzes the problem that the pulsed-magnetic-field-based electromagnetic particle velocity measurement technology will introduce additional induced electromotive force, and proposes an electromagnetic particle velocity measurement technology based on superconducting magnet. After considering the factors of electromagnetism, structure and heat distribution, a superconducting magnet with 500mm room-temperature bore was constructed, and the proposed electromagnetic particle velocity measurement system based on the superconducting magnet was designed subsequently. The experiment of filled explosion in PMMA was carried out, and high quality particle velocity and displacement signals were obtained, which verified the measurement performance of the system. The proposed method can provide a more powerful test means for the study of stress wave propagation.

Liquid–Solid Two-Phase Flow Rate Measurement by Electrical and Ultrasound Doppler Sensors

Flow rate measurement in multiphase flow is essential for process control and safety production. As the drawbacks of conventional flowmeter measurement error produced by the heterogeneous phase or velocity distribution, a measurement technique combining an electrical resistance tomography (ERT) and an ultrasound Doppler (UD) sensor is proposed. The UD sensor obtains the dispersed particle velocity distribution, and the ERT acquires the solid phase distribution. An experimental platform is constructed for the liquid-solid two-phase horizontal flow experiments. The dual-plane ERT with the cross-correlation signal analysis compensates for the inaccurate particle velocity measurement at the bottom of the pipe by using UD independently due to the locally high concentration. The liquid-solid two-phase mixed flow rate under different flow regimes is measured with the two sensors. The proposed method has a 6.3% maximum uncertainty for the liquid-solid two-phase flow rate measurement.