Prediction Of Particle Velocity Research Articles

Semi-empirical model for abrasive particle velocity prediction in abrasive waterjet based on momentum transfer efficiency

AbstractAbrasive waterjet (AWJ) is a technology that removes a target material with an abrasive accelerated by ultra-high-pressure water. Recently, its application for rock excavations in civil and geotechnical engineering has increased. AWJ excavation performance is affected by the abrasive velocity formed by momentum transfer during mixing and acceleration. The abrasive velocity varies owing to changes in the abrasive flow rate, focusing tube diameter, and focusing tube length. In this study, the momentum transfer efficiency (MTE) according to the abrasive flow rate and focusing tube geometry was investigated by a numerical analysis to better understand the multiphase flow inside the AWJ system. The MTE was defined based on the theoretical relationship between the abrasive velocity ratio and focusing tube factor, and evaluated through the empirical relationship between the water stiffness and focusing tube length. The optimal abrasive flow rate for generating efficient MTE was approximately 15 g/s, which enabled economical and effective acceleration of abrasive particles. Accordingly, a prediction model based on the derived MTE was developed for the final abrasive velocity generated at the tip of the focusing tube. Using the prediction model, it is possible to evaluate the comprehensive relationship between various AWJ parameters. Based on the prediction model, the abrasive–water flow ratio to generate the optimal abrasive velocity was 0.83. The developed prediction model provides guidelines for selecting the optimal focusing tube geometry and applying an economical abrasive flow rate when designing an AWJ system.

Optimization of Cold Spray Nozzles Based on the Response Surface Methodology

Spraying technical parameters are important factors that affect spraying efficiency. Most studies on spraying technical parameters use single-factor methods to study the speed of spray particles, and few scholars have studied the joint influence of multiple factors. This article uses gas temperature, particle size, and gas pressure as independent variables, and the independent variables interact. The design-expert method was used to establish a linear regression equation model of the velocity of sprayed Al and Cu particles at the Laval exit and the velocity before deposition with the substrate, and the response surface analysis method was used to predict the optimal spraying parameters of Al and Cu particles. The study found the contribution rate of three factors to particle velocity: the prediction of particle velocity at the exit of the Laval nozzle and before deposition with the substrate was realized; the error between the predicted value of particle velocity and the actual value obtained by simulation is less than 1.6 %, indicating that the speed linear regression equation established is effective and reliable in predicting the simulation results; the optimal spraying parameters and particle speeds of Al and Cu particles were obtained through response surface analysis.

Improving the precision of solids velocity measurement in gas-solid fluidized beds with a hybrid machine learning model

Accurate measurement of solids velocity is crucial for fluidized bed reactor design, optimization, and scaling in chemical engineering. However, the cross-correlation calculation of dual-channel particle concentration signals has limitations in dense-phase fluidized systems. To address this, we propose a data-driven approach using machine learning algorithms in numerical simulations. Four popular algorithms (linear regression, random forest, support vector machine, and neural network) are evaluated. Individual models show poor generalization with a determinable coefficient below 0.2. To overcome this, a hybrid model combining a neural network and random forest is developed, improving data prediction and generalization. The determinable coefficient increases to 0.90, and the relative error in average particle velocity prediction reduces to less than 0.01. This hybrid machine learning model has the potential to overcome limitations of cross-correlation-based particle velocimetry, expanding its applications in multiphase flow systems. It offers a promising solution for accurate solids velocity measurement in fluidized beds.

Understanding of turbulence modulation and particle response in a particle-laden jet from direct numerical simulations

Abstract Point-particle direct numerical simulations have been employed to quantify the turbulence modulation and particle responses in a turbulent particle-laden jet in the two-way coupled regime with an inlet Reynolds number based on bulk velocity and jet diameter $({D_j})$ of ~10 000. The investigation focuses on three cases with inlet bulk Stokes numbers of 0.3, 1.4 and 11.2. Special care is taken to account for the particle–gas slip velocity and non-uniform particle concentrations at the nozzle outlet, enabling a reasonable prediction of particle velocity and concentration fields. Turbulence modulation is quantified by the variation of the gas-phase turbulent kinetic energy (TKE). The presence of the particle phase is found to damp the gas-phase TKE in the near-field region within $5{D_j}$ from the inlet but subsequently increases the TKE in the intermediate region of (5–20)Dj. An analysis of the gas-phase TKE transport equation reveals that the direct impact of the particle phase is to dissipate TKE via the particle-induced source term. However, the finite inertia of the particle phase affects the gas-phase velocity gradients, which indirectly affects the TKE production and dissipation, leading to the observed TKE attenuation and enhancement. Particle response to the gas-phase flow is quantified. Particles are found to exhibit notably stronger response to the gas-phase axial velocity than to the radial velocity. A new dimensionless figure is presented that collapses both the axial and radial components of the particle response as a function of the local Stokes number based on their respective integral length scales.

An inertial number regulated stress model for gas-particle flows with particle friction and volume fraction gradient

In this study, a solid stress model that can be used in both dilute and dense regimes for simulation of gas-particle flows with comprehensive considerations of friction and the effect of local solid volume fraction gradient is proposed. In the dilute regime, solid stress is closed by a modified kinetic theory that accounts for the effect of particle friction and volume fraction gradient. In the dense regime, solid stress is closed by the inertial number model. The transition from dilute to dense regimes is realized by using a dimensionless parameter χ , which is a function of the inertial number I s . This new model is validated with experimental data and discrete particle simulation from spout-fluid bed and bubbling fluidized bed. When compared with the traditional kinetic-frictional stress model, this new model improves the transition from dilute to dense regimes and the particle velocity predictions in both beds. • A solid stress model is proposed in both dilute and dense regimes for gas-solid flow. • The model comprehensively considers the effect of friction and volume fraction gradient. • The expression of excluded volume is derived from the generalized van der Waals theory. • The model gives a better prediction of spout-fluid bed and bubbling fluidized bed.

Large eddy simulation of polydispersed inertial particles using two-way coupled PDF-PBE

This paper presents large eddy simulation (LES) of polydispersed turbulent recirculating flows using a two-way coupled probability density function of the population balance equation (PDF-PBE). A stochastic Monte Carlo method is adopted to solve the PDF-PBE on an ensemble of notional Lagrangian particles and the method of Stokes binning, that was recently developed by Salehi et al. (2017) is employed to explicitly treat effects of inertia. The PDF-PBE is applied to the experiment of Boŕee et al. (2001) which studied dispersion of polysized inertial particles in a bluff body configuration. The particle mass loading is 22% where the dispersed elements affect the carrier phase velocity. The simulations are performed using both the standard Smagorinsky and the Wall-Adapting Local Eddy-viscosity (WALE) subgird turbulent models. It is found that the subgrid model has a significant impact on the results, particularly on the carrier velocity. The WALE model shows a better agreement with the measurements. Different boundary conditions are tested for injection of notional particles. It is demonstrated both dispersed and carrier phase velocities are initially sensitive to the particle boundary condition whereas the difference between tested conditions becomes marginal further downstream. The best results are obtained for the particle boundary condition that accounts for effects of inertia at the inlet. Finally, the sensitivity of the PDF-PBE simulations to the number of Stokes bins is studied. It is found that eight Stokes bins are enough to accurately model the polysized particles dispersion in a bluff body configuration. The results indicate that particle dispersion is notably sensitive to the number of Stokes bins but the particle velocity predictions are much less sensitive with small variation in velocity results over the range of Stokes bins that were tested.

Evaluation of Heat Transfer Transport Coefficient for Cold Spray Through Computational Fluid Dynamics and Particle In-Flight Temperature Measurement Using a High-Speed IR Camera

This work aims at obtaining experimental particle temperature readings during the cold spray (CS) process using a high-speed, high-definition infrared (IR) camera for multiple gas stagnation parameters to infer the suitability and accuracy of Nusselt number and drag coefficient correlations widely used in CS modeling. Measured particle temperatures are compared with values obtained through numerical modeling. Measured particle velocity using recorded data from the IR camera, based on particle streak and particle tracking velocimetry methods, is compared to values obtained from simulations. Additionally, particle velocities acquired using a Cold Spray Meter are also considered. Results demonstrate that only one of all common Nusselt correlations typically used in CS modeling results in accurate particle temperature predictions. Furthermore, the study shows that the drag coefficient correlation must incorporate the particle Mach number in order to provide acceptable particle velocity predictions.

Classification and regression tree technique in estimating peak particle velocity caused by blasting

Blasting is a widely used technique for rock fragmentation in surface mines and tunneling projects. The ground vibrations produced by blasting operations are the main concern for the industries undertaking blasting operations, which can damage the surrounding structures, adjacent rock masses, roads and slopes in the vicinity. Therefore, proper prediction of blast-induced ground vibrations is essential to demarcate the safety area of blasting. In this research, classification and regression tree (CART) as a rule-based method was used to predict the peak particle velocity through a database comprising of 51 datasets with results of maximum charge per delay and distance from the blast face were fixed as model inputs. For comparison, the empirical and multiple regression (MR) models were also applied and proposed for peak particle velocity prediction. Performance of the proposed models were compared and evaluated using three statistical criteria, namely coefficient of correlation (R2), root mean square error (RMSE) and variance account for (VAF). Comparison of the obtained results demonstrated that the CART technique is more reliable for predicting the peak particle velocity than the MR and empirical models and it can be introduced as a new technique in this field.

Prediction of ground vibration due to quarry blasting based on gene expression programming: a new model for peak particle velocity prediction

Blasting is a widely used technique for rock fragmentation in opencast mines and tunneling projects. Ground vibration is one of the most environmental effects produced by blasting operation. Therefore, the proper prediction of blast-induced ground vibrations is essential to identify safety area of blasting. This paper presents a predictive model based on gene expression programming (GEP) for estimating ground vibration produced by blasting operations conducted in a granite quarry, Malaysia. To achieve this aim, a total number of 102 blasting operations were investigated and relevant blasting parameters were measured. Furthermore, the most influential parameters on ground vibration, i.e., burden-to-spacing ratio, hole depth, stemming, powder factor, maximum charge per delay, and the distance from the blast face were considered and utilized to construct the GEP model. In order to show the capability of GEP model in estimating ground vibration, nonlinear multiple regression (NLMR) technique was also performed using the same datasets. The results demonstrated that the proposed model is able to predict blast-induced ground vibration more accurately than other developed technique. Coefficient of determination values of 0.914 and 0.874 for training and testing datasets of GEP model, respectively show superiority of this model in predicting ground vibration, while these values were obtained as 0.829 and 0.790 for NLMR model.

The comparison of most widely used ground vibration predictor equations and suggestions for the new attenuation formulas

Blast-produced ground vibrations is one of the fundamental problems in mining industry as well as construction operations. Therefore, the prediction of ground vibration components is very important in the minimization of blast related complaints. This paper presents the results of simple and multiple linear regression analyses for the comparison of the most widely used peak particle velocity prediction equations. For this purpose, the results of blast-induced ground vibration measurements by different authors with the measurements conducted within this study were taken into account together. In the statistical analyses, a total of 247 regression models were analysed by using a statistical software. Then, the site-specific constants were determined by the regression analyses of scaled distance and peak particle velocity data pairs according to different approaches and considered cases were evaluated statistically. By evaluating the statistical results, a new prediction equation based on scaled distance concepts was proposed. In addition, new attenuation formulas were proposed for the determination of the site-specific constants. The analyses have shown that if scaled distance concept itself is used for inelastic attenuation factor to predict PPV, the highest values of coefficient of determination are obtained.

Physical mechanisms involved in slug transport and pipe blockage during horizontal pneumatic conveying

Moving slugs of plastic pellets were investigated in-situ during low velocity pneumatic conveying in horizontal pipelines. Slug characteristics including the profile of pressure, pressure gradient, particle velocity, porosity, radial and wall shear stresses, aspect and behaviour were combined to obtain a complete picture of moving slugs. The objective was to gain unique knowledge on the physical mechanisms involved in slug formation, transport, and decay and the occurrence of pipe blockage. Slugs in both stable and unstable states were analysed. A strong correlation between particle velocity and wall stresses was found, which suggests that the stresses responsible for the high pressure loss characterising slug flow may result mostly from the transfer of particle impulses to the pipe wall. Most slugs were found to be denser at the rear where particle velocity was the highest, thus leading to slug shortening over time. This phenomenon was successfully modelled using both Newton's 2nd law and the ideal gas law and prediction of particle velocity showed good agreement with experimental values. In contrast, other slugs were found to extend due to the particles at the front moving faster than the particles at the rear. Pipe blockage was found to result from insufficient permeation of the slug by the conveying gas, indicating that sufficient material permeability is a condition for slug flow to occur.

Flowsheet optimization of an integrated continuous purification-processing pharmaceutical manufacturing operation

In this work, a continuous API purification process has been optimized using an integrated flowsheet model. The simulation is dynamic in nature and includes an API purification step (crystallization), followed by filtration, drying and mixing of the API with an excipient. For the first time, this study demonstrates the use of a reduced order model (ROM) within the mixing unit for prediction of particle velocities that is coupled with a population balance model (PBM) of the mixer to quantify macroscopic properties. The main objective is to optimize the integrated flowsheet model such that there is an overall improvement in process operation. The optimum cooling schedule during crystallization has been obtained. The optimum values of filter pressure gradient, drying gas temperature and mixer RPM (speed) have also been determined. It is seen that the optimized operating conditions give a narrower CSD of the API crystals and lower RSD (Relative standard deviation) of the final mixed product, compared to nonoptimal operating condition. The developed model can be used as an effective tool in control and optimization and can have future implementation in design of a Process Analytical Technology (PAT) system which can lead to improved operation of the manufacturing process.

A new damage criteria norm for blast-induced ground vibrations in Turkey

Environmental problems such as vibration and air blast are often faced and discussed in mining, quarrying, civil construction, shaft tunnel, pipeline, and dam operations, where blasting is inevitable. It is necessary to establish national standards in order to minimize environmental problems induced by blasting and judicial matters in our country as it is in the USA, European Union (EU) countries, and other developed countries. This necessity and the obligation of Turkey, which has started the procedure of joining the EU, to accept EU criteria emphasize the importance of this study. In other words, the establishment of a particular national standard related with this subject is inevitable for Turkey. This will be possible only by studying and applying scientific methods and techniques by experts. This paper presents a new damage criterion norm for blast-induced ground vibrations in Turkey. In this study, first, numerous vibration records were taken in blasting operations performed at different sites and rock units. For these rock units, particle velocity predictions and frequency analysis were done. At the same time, structures in the neighborhoods of these blasts were also observed and investigated. Finally, a damage criterion norm based on risk analysis was established and proposed by using these collected data. In light of the norm to be obtained from the data that were collected in the research, it will lead the excavation work in our country to be performed in such way that they are more effective and will cause minimum environmental problems.

Numerical simulation of pulverized coal jet flame employing the TDP model

The effect of the devolatilization model on the coal particle behavior is investigated in detail by performing numerical simulations of a simple pulverized coal jet flame formed by a small jet burner (0.5kg-coal/h) [S. Hwang et al., Energy & Fuels 2005;19:382–92]. As the devolatilization model, widely-used conventional devolatilization model, two competing reaction rate model and newly-proposed tabulated-devolatilization-process model (TDP model) [N. Hashimoto et al., Combust Flame 2012;159:353–366] are used. The results show that the coal particle velocities predicted by the TDP model are in better agreement with the experiments than those by the other models, with a slight increase in computation time. The difference in the mean axial particle velocity between the simulations is caused by the difference in the axial gas velocity, which is ultimately caused by the difference in the volatile matter evolution rate. It is also found that the devolatilization model has great influence on particle velocity prediction compared to the turbulence model, the gas-phase combustion model and the radiation model.

Experimental study on the solid velocity in horizontal dilute phase pneumatic conveying of fine powders

The calculation reliability of pressure drop and gas–solid drag force in horizontal dilute phase pneumatic conveying strongly depends on the accuracy of gas–solid velocity correlation. However, there are limited studies on the solid velocity in horizontal dilute phase pneumatic conveying and it is important to further validate suitability of existing correlation of gas–solid velocity, especially for fine particles (such as pulverized coal). Consequently, in this paper, a negative pressure pneumatic conveying test rig is set up and two kinds of powders with different sizes are adopted. Optical fiber probe (OFP) was used to measure the volumetric solid concentration and particle velocity. The volumetric solid concentration was also calculated by using the measured particle velocity. The results show that the solid concentrations obtained by the two methods have good agreement, and discrepancy is within ± 20%. It was found the particle velocities are different in the upper and lower part of the cross-section in the horizontal pipe. However, the difference is generally no more than 2 m/s. The velocity difference will decrease with the increasing gas velocity, and increases with the solid mass flow rate. In the experimental condition of 0.06 mm < d s < 0.35 mm, 1400 kg/m 3 < ρ s < 2600 kg/m 3, the implicit correlation based on Yang's Unified Theory gives the best prediction of particle velocity among existing studies but still with noticeable discrepancy with the comparison of the present experimental data. By modifying the solid friction factor, an improved correlation of the particle velocity was obtained, which agrees better with the experimental data given in the present and literature studies.

Modeling the acoustic channel for mixed pressure and particle velocity sensors.

Looking at our repertoire of acoustic modeling techniques, ray tracing and Gaussian beams provide a good match to modeling the underwater channel for acoustic communications, given their fundamentally broadband nature. We will discuss how we have augmented existing acoustic models, including Gaussian beam and normal mode codes, to produce particle velocity predictions. In both of these cases, the modifications consisted of manipulating the components used to represent the pressure field, as opposed to relying upon a finite difference approximation of the predicted field itself. We will discuss further modifications to these codes that enable the dynamic features of the channel to be modeled, including source and receiver motion, and motion of the ocean surface due to ocean surface waves. It is important to model realizations of the channel, rather than averaged representations, because many of the high-speed, coherent modulation schemes that are the focus of continuing research use tracking loops in their design. These tracking loops must be stressed with realistically time-evolving channels. Acoustic channel predictions will be compared with experiment data from acoustic communications experiments off the coast of Kauai in Hawaii.

The effect of discontinuity frequency on ground vibrations produced from bench blasting: A case study

A good number of empirical formulae and methods dealing with the analysis of the effects of blast-induced ground vibrations have been developed. The most common approach suggested for estimating the attenuation of particle velocity on the ground is to scale the distance (scaled distance, SD). This approach makes it possible to estimate the peak particle velocity when the amount of explosive charge or the distance or both are altered. Many parameters known to have an influence on particle velocity have been used for particle velocity prediction equations. Some of these parameters are maximum charge per delay, the distance between the station and shot location, burden, inelastic attenuation factor and site factors. However, the impacts of the discontinuities existing on the benches where blasts are detonated on the propagation velocity of seismic waves have not been taken into consideration in these equations. This study aims to examine the impacts of the discontinuity frequency parameter derived through geological measurements carried out on the blasting benches or nearby in a quarry mine (Supren, Eskisehir) in Turkey on the propagation of blast-induced ground vibrations. Developed based on the geological observations carried out on the benches, the model was formed by adding discontinuity frequency parameter to the particle velocity prediction model suggested by Nicholls et al. [Nicholls HR, Johnson CF, Duvall WI. Blasting vibrations and their effects on structures. Bulletin no. 656. Washington, DC: US Bureau of Mines; 1971]. In order to research the effect of the discontinuity frequency in the bench on the blast-induced ground vibrations, the relationship between the recorded peak particle velocity, scaled distance and discontinuity frequency was statistically evaluated for the site. The established relationship and the results of the study are presented.

Dilute gas–solid two-phase flows in a curved [formula omitted] duct bend: CFD simulation with experimental validation

Computational fluid dynamics (CFD) simulations of dilute gas–solid flow through a curved 90 ∘ duct bend were performed. Non-uniform sized glass spheres with a mean diameter of 77 μ m were used as the dispersed phase. The curved bend is square-sectioned ( 150 mm × 150 mm ) and has a turning radius of 1.5 D ( D = duct hydraulic diameter). Turbulent flow quantities for Re = 100 , 000 were calculated based on a differential Reynolds stress model. The solids mass loading considered is 0.00206 and hence justifies the application of one-way coupling between gas and particles. A Lagrangian particle-tracking algorithm which takes into account the effect of shear-slip lift (SSL) force on particles and particle-wall interactions (PWIs) has been utilised to predict velocities of the dispersed phase. The predictions were compared against the experimental data measured using Laser–Doppler Anemometry (LDA). The study found that the predicted gas flow field has a strong influence over the predicted particle velocities. PWI model considerably affects the prediction of particle velocity and distribution of particles at the inner duct wall within the bend. Inclusion of the SSL force also helps the distribution of the particle tracks towards the duct centre in the vertical duct downstream of the bend. Within the bend, particle velocities near the inner wall have been grossly over-predicted in the simulation, especially at mid-bend. The present study thus highlights the importance of the predicted gas flow field, SSL force and particle-wall collisions to Lagrangian particle tracking.

A numerical study of a protection technique against tube erosion

Erosion of tubes by coal particles or coal ash impingement has caused serious problems for many pulverized coal energy conversion systems. It is important to study erosion protection methods for heat exchanger tubes undergoing erosion. In this paper, a new type of erosion-protection technique, the finned tube erosion-protection technique, is proposed. Fins located on both sides of tubes alleviate tube erosion in the way they change gas flow field, then consequently change particle trajectories, particle-tube collision frequency, and erosion damage of tubes. A numerical study has been conducted for the flow of a dilute particle-laden gas moving past a finned tube undergoing erosion. Eulerian equations are used to describe gas-phase motion, with the turbulence viscosity evaluated from the turbulent kinetic energy k and its dissipation ε model of turbulence. The prediction of particle velocities and trajectories takes into account the effect of the turbulence with a stochastic particle dispersion model. The particle impaction/rebound model and the erosion model of ductile alloys are used to predict the particle-rebound phenomena and the erosion damage to the tubes. The present paper discusses the effect of relative length of fins, free stream velocity and particle size on particle-tube collision frequency and erosion damage of the tubes. The results show that the finned tube is a simple and efficient erosion protection method in most industrial two-phase systems where erosion occurs.

Computational Fluid Dynamics Analysis of a Wire-Feed, High-Velocity Oxygen Fuel (HVOF) Thermal Spray Torch

The fluid and particle dynamics of a high-velocity oxygen fuel (HVOF) thermal spray torch are analyzed using computational and experimental techniques. Three-dimensional computational fluid dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco diamond jet rotating wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled using a single-step, finite-rate chemistry model with a total of nine gas species which includes dissociation of combustion products. A continually fed steel wire passes through the center of the nozzle, and melting occurs at a conical tip near the exit of the aircap. Wire melting is simulated computationally by injecting liquid steel particles into the flow field near the tip of the wire. Experimental particle velocity measurements during wire feed were also taken using a laser two-focus (L2F) velocimeter system. Flow fields inside and outside the aircap are presented, and particle velocity predictions are compared with experimental measurements outside of the aircap.