Granular Flow Rate Research Articles

Project Based Learning of Free-Falling Objects inPhysics: Microcontroller-Based Multi-SensorTest in Granular Flow Rate Measurement

Project Based Learning of Free-Falling Objects inPhysics: Microcontroller-Based Multi-SensorTest in Granular Flow Rate Measurement

Investigating the Flow Rate of Granular Material in a Dynamic System

The aim of this research is to investigate the effective method of predicting granular flow rate in a dynamic system, specifically a system undergoing vertical periodical fluctuation, simplified into uniform circular motion in this investigation. The preliminary investigation recognises the explanation from Beverloo’s relation in literature and confirmed its effectiveness in predicting the flow rate of granular material through a static silo. Hence, a mathematical hypothesis regarding the research question is established successfully, synthesizing the hypothesis of projection of effective diameter and vertical acceleration. In experiment, the hypothesis of the projection of effective diameter of the flow region is verified experimentally; whereas various implications arise when applying the conventional force analysis into the Beverloo’s relation. Although the current evidence is deficient in supporting me proposing the new law, this investigation systematically discuss the interconnection among the variables in Beverloo’s relation, and the current implication revealed shed a light on further research.

The modeling of free-fall arch formation in granular flow through an aperture

In this study, to predict the formation of the free-fall arch via granular flow through an aperture, an analytical model has been developed based on the particle-scale force equilibrium. This model calculates the size and location of the meta-stable arch and can be extended to predict the granular flow rate. According to the developed analytical model, the formation of a free-fall arch is independent of granular height and stress state above the arch, where only granular particle size, aperture size, and granular friction influence the development of the arch. Besides, this proposed model can predict the formation of the meta-stable arch without empirical parameters. In comparison with experimental results, the predicted granular flow rate based on the model exhibits high accuracy for uniform-sized granular flow. According to numerical simulations, the free-fall arch appears above the aperture; however, the particle velocity at the arch is low and can be considered negligible. Gravity will cause the granular particles under the arch to fall freely. This mathematical model offers an efficient method to predict the formation of the free-fall arch and calculate the granular flow rate through an aperture.

Discharge of a 2D magnetic silo

We investigate experimentally the discharge of a 2D-silo, a Hele-Shaw cell, filled with a mono layer of ferromagnetic grains submitted to an external magnetic field B perpendicular to the cell plane. In this case the magnetic pair interactions are repulsive. We show that the granular flow rate decreases systematically with the amplitude of the external magnetic field applied. Interestingly, while the output flow rate remains constant during an experiment, we reveal very large spatio-temporal fluctuations of the packing density within the cell, particularly evident for magnetic field of high amplitudes.

Experimental study on filtration performance of a sliding granular bed filter

A new sliding granular bed filter (SGBF), coupling the features of fixed and moving granular bed filters, was presented. An inclined granular bed was used and filter grains slid down along the inclined bed in SGBF. The grains slid fastest at bed surface and are slowed down along bed depth. According to the movement of grains, SGBF is classified as partial SGBF (P-SGBF) and whole SGBF (W-SGBF). Our results showed that P-SGBF exhibited a similar pressure drop with W-SGBF, whereas its collection efficiency was close to that of the fixed bed. The filter quality factor was adopted to estimate the performance of SGBF by coupling the effects of collection efficiency and pressure drop. P-SGBF was superior to W-SGBF and fixed granular bed filters with increasing filtration time. In addition, effects on the performance of SGBF including granular flow rate, gas velocity and inlet dust concentration were further discussed.

A digital image flow meter for granular flows with a comparison of direct regression and neural network computational methods

Effective measurement of dense granular flow rates is essential for ensuring optimal performance of a wide variety of industrial processes with digital imaging processing techniques being developed and implemented in many manufacturing control applications. This paper presents a digital image flow meter system that utilizes sequential image pairs to determine granular mass flow rates with a comparison of two different computational strategies: Direct Regression (DR) of the displacements and Neural Network (NN) modeling. Results show DR is a robust method that can accurately predict flow rates with an average relative error of 7.56% without calibration despite its simplicity. Both methods can have the relative error reduced below 3% by time-averaging over a series of measurements. NN models were found to predict flow rates from image pairs faster than DR, but the NN predictions had a higher variance and lower accuracy. The proposed granular flow metering strategy has the potential of utilizing inexpensive hardware to effectively estimate flow rates and can be easily implemented in hardware platforms where there is a visible granular flow.

Increasing granular flow rate with obstructions

We describe a simple experiment involving spheres rolling down an inclined plane towards a bottleneck and through a gap. Results of the experiment indicate that flow rate can be increased by placing an obstruction at optimal positions near the bottleneck. We use the experiment to develop a computer simulation using the PhysX physics engine. Simulations confirm the experimental results and we state several considerations necessary to obtain a model that agrees well with experiment. We demonstrate that the model exhibits clogging, intermittent and continuous flow, and that it can be used as a tool for further investigations in granular flow.Received: 22 November 2015, Accepted: 19 February 2016; Edited by: L. A. Pugnaloni; Reviewed by: C. M. Carlevaro, Instituto de Física de Líquidos y Sistemas Biológicos, La Plata, Argentina; DOI: http://dx.doi.org/10.4279/PIP.080003Cite as: A Murray, F Alonso-Marroquin, Papers in Physics 8, 080003 (2016)This paper, by A Murray, F Alonso-Marroquin, is licensed under the Creative Commons Attribution License 3.0.

How does internal angle of hoppers affect granular flow? Experimental studies using digital particle image velocimetry

Mechanical behaviour of powders and grains often displays features of solid-like and liquid-like characteristics of matter. In spite of processing granular materials quite extensively in the industries, their flow behaviour is still complex to understand under different process conditions. In this paper, using digital particle image velocimetry (DPIV) and high speed videography, we probe systematically on the spatial and temporal distributions of the velocity fields of pharmaceutical excipient granules flowing though smooth hoppers with different internal (orifice) angles. This helps to visualise and identify the locations and formation of the flow channels and conversely the stagnation zones of granular materials inside the hoppers as a function of the internal angle of the hoppers. We show that even when a powder characterised as a free-flowing type in the conventional sense could experience a significant level of hindrance to flow even when passing through smooth hoppers of different internal angles, and its impact increases with an increase in the internal angle. Theoretical predictions are made using experimentally evaluated grain-scale properties as input parameters for understanding the effects of hopper angle on the granular flow rate. A good level of agreement is obtained between the experimental and theoretical estimates of the granular flow rate in terms of the hopper angle. The outcomes presented here are a step forward in designing granular flow devices more efficiently in the future.

Simulation of Granular Flows and Pile Formation in a Flat-Bottomed Hopper and Bin, and Experimental Verification.

Granular flows of 200 μm particles and the pile formation in a flat-bottomed hopper and bin in the presence of air and in a vacuum were predicted based on three-dimensional numerically empirical constitutive relations using Smoothed Particle Hydrodynamics and Computational Fluid Dynamics methods. The constitutive relations for the strain rate independent stress have been obtained as the functions of the Almansi strain including the large deformation by the same method as Yuu et al. [1]. The constitutive relations cover the elastic and the plastic regions including the flow state and represent the friction mechanism of granular material. We considered the effect of air on the granular flow and pile by the two-way coupling method. The granular flow patterns, the shapes of piles and the granular flow rates in the evolution are compared with experimental data measured under the same conditions. There was good agreement between these results, which suggests that the constitutive relations and the simulation method would be applicable for predicting granular flows and pile formation with complex geometry including free surface geometry. We describe the mechanisms by which the air decreases the granular flow rate and forms the convergence granular flow below the hopper outlet.

The influence of granular flow rate on the performance of a moving bed granular filter

The goal of this study is to evaluate the effect of granular flow rate on the performance of a moving bed granular filter designed for hot gas filtration of fine char particles (dust) produced during fast pyrolysis of biomass. The filter employs a counter-current configuration, in which down-flowing granular material spreads out at the bottom of the filtration vessel to form an interfacial area where the dusty gas enters the granular bed and much of the gas cleaning is hypothesized to occur. This study uses a real-time particle counter to measure the instantaneous filtration efficiency during cold flow tests of the filter. Differential pressure measurements at various locations within the granular bed are used to assess the level of char dust hold-up over time. These experiments reveal a critical granular residence time below which the filter must be operated to achieve filtration efficiencies exceeding 99%. Operating above the critical value causes the filter to “clog” and decrease in efficiency. The clogging is characterized by a critical dust volume fraction as determined through a fixed bed filtration test. The filter is found to accumulate most of the dust at the interfacial region. Also the interfacial region is more efficient than the downcomer section of the granular bed in removing dust. Decreasing residence time of granular material in the filter reduces the hold-up of char dust in the filter, which is expected to mitigate coking reactions of organic vapors when the filter is used to remove char from fast pyrolysis gas streams.

The effect of opening-angle at choke point on the two-dimensional granular flow on a conveyor belt

The relationship between the granular flow rate Q on a two-dimensional conveyor belt and the opening-angle θ at choke point together with the velocity of the conveyor belt and the exit-size has been studied in the experiment. The result shows that the granular flow rate Q is influenced chiefly by the following factors: the exit width R, the speed of the conveyor belt and the opening-angle θ at choke point. The rate of flow Q increases linearly with the speed v and the exit width R, and the rate of flow Q decreases linearly with cosθ when the opening-angle θ is larger than 15° for the dilute granular flow.

Experimental study of a granular flow in a vertical pipe: A spatiotemporal analysis

The spatiotemporal characteristics of the flow of $125 \ensuremath{\mu}\mathrm{m}$ glass beads have been studied experimentally in a 2.9 mm diameter vertical glass pipe by means of a digital linear charge coupled device camera. The dynamics and propagation of granular density fluctuations have been analyzed in various flow regimes for different values of the granular mass-flow rate and of the degree of humidity H. At low flow rates, the granular flow has a high compactness and periodic intermittency effects occur at high H values: a pulsating bubble appears at the top of the flow channel and its time dependence is studied. At higher granular flow rates, a wave regime is observed with alternate low and high compactness regions: at low H values, the wave velocity is constant with time and can be measured precisely from the spatiotemporal diagrams. At higher humidity contents, periodic oscillations of the wave system are observed: at high amplitudes, transient blockages of the flow and a stick-slip displacement mode have been identified.