Complex Flow Dynamics in Dense Granular Flows—Part II: Simulations

2006 ◽  
Vol 74 (4) ◽  
pp. 691-702 ◽  
Author(s):  
Piroz Zamankhan ◽  
Jun Huang
Keyword(s):  
Granular Flow ◽  
Large Scale ◽  
Flow Behavior ◽  
Granular Flows ◽  
Industrial Applications ◽  
Complex Flow ◽  
Flow Phenomena ◽  
Newton’S Cradle ◽  
Large Scale Simulations ◽  
Dense Granular Flows

By applying a methodology useful for analysis of complex fluids based on a synergistic combination of experiments, computer simulations, and theoretical investigation, a model was built to investigate the fluid dynamics of granular flows in an intermediate regime, where both collisional and frictional interactions may affect the flow behavior. In Part I, experiments were described using a modified Newton’s Cradle device to obtain values for the viscous damping coefficient, which were scarce in the literature. This paper discusses detailed simulations of frictional interactions between the grains during a binary collision by employing a numerical model based on finite element methods. Numerical results are presented of slipping, and sticking motions of a first grain over the second one. The key was to utilize the results of the aforementioned comprehensive model in order to provide a simplified model for accurate and efficient granular-flow simulations with which the qualitative trends observed in the experiments can be captured. To validate the model, large scale simulations were performed for the specific case of granular flow in a rapidly spinning bucket. The model was able to reproduce experimentally observed flow phenomena, such as the formation of a depression in the center of the bucket spinning at high frequency of 100rad/s. This agreement suggests that the model may be a useful tool for the prediction of dense granular flows in industrial applications, but highlights the need for further experimental investigation of granular flows in order to refine the model.

Complex Flow Dynamics in Dense Granular Flows—Part I: Experimentation

2005 ◽  
Vol 73 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Piroz Zamankhan ◽  
Mohammad Hadi Bordbar
Keyword(s):  
Flow Behavior ◽  
Viscoelastic Behavior ◽  
Granular Flows ◽  
Viscous Damping ◽  
Complex Flow ◽  
Interparticle Interactions ◽  
Dynamic Simulations ◽  
Newton’S Cradle ◽  
The Impact ◽  
Dense Granular Flows

By applying a methodology useful for analysis of complex fluids based on a synergistic combination of experiments, computer simulations, and theoretical investigation, a model was built to investigate the fluid dynamics of granular flows in an intermediate regime where both collisional and frictional interactions may affect the flow behavior. In Part I, the viscoelastic behavior of nearly identical sized glass balls during a collision have been studied experimentally using a modified Newton’s cradle device. Analyzing the results of the measurements, by employing a numerical model based on finite element methods, the viscous damping coefficient was determined for the glass balls. Power law dependence was found for the restitution coefficient on the impact velocity. In order to obtain detailed information about the interparticle interactions in dense granular flows, a simplified model for collisions between particles of a granular material was proposed to be of use in molecular dynamic simulations, discussed in Part II.

Granular Flow Modeling and Simulation Using a Dynamic Finite Element Method

2007 ◽  
Author(s):  
M. A. Kabir ◽  
C. Fred Higgs ◽  
Michael R. Lovell
Keyword(s):  
Finite Element ◽  
Modeling And Simulation ◽  
Granular Flow ◽  
Flow Behavior ◽  
Food Service ◽  
Complex Nature ◽  
Complex Flow ◽  
Dual Nature ◽  
Simulation Techniques ◽  
Flow Phenomena

Granular flow behavior is of fundamental interest to the engineering and scientific community because of the prevalence of these flows in the pharmaceutical, agricultural, food service, and powder manufacturing industries. Granular materials exhibit very complex behavior, oftentimes acting as solids and at other times as fluids. This dual nature leads to very complex and rich behavior, which is not yet well understood. Therefore, the present investigation introduces a new technique that can potentially be used to unveil the mystery of granular flow phenomena. To this end, advanced finite element modeling and simulation techniques have been applied to the study of the complex nature of granular flow. More specifically, the explicit dynamic code LS-DYNA has been utilized to gain an understanding of the complex flow nature and collision stresses of granules in a shear cell.

Complex Flow Dynamics in Dense Granular Flows: Part I — Experimentation; Part II — Simulations

2005 ◽  
Author(s):  
Piroz Zamankhan
Keyword(s):  
Continuum Model ◽  
Complex Fluids ◽  
Flow Behavior ◽  
Granular Flows ◽  
Viscous Damping ◽  
Interparticle Interactions ◽  
Dynamic Simulations ◽  
Intermediate Regime ◽  
Newton’S Cradle ◽  
Dense Granular Flows

PART I: By applying a methodology useful for analysis of complex fluids based on a synergistic combination of experiments, computer simulations and theoretical investigation, a model was built to investigate the fluid dynamics of granular flows in an intermediate regime where both collisional and frictional interactions may affect the flow behavior. In Part I, the viscoelastic behavior of nearly identical sized glass balls during a collision, have been studied experimentally using a modified Newton’s Cradle device. Analyzing the results of the measurements, by employing a numerical model based on finite element methods, the viscous damping coefficient was determined for the glass balls. Power law dependence was found for the restitution coefficient on the impact velocity. In order to obtain detailed information about the interparticle interactions in dense granular flows, a simplified model for collisions between particles of a granular material was proposed to be of use in molecular dynamic simulations, discussed in Part II. PART II: By applying a methodology useful for analysis of complex fluids based on a synergistic combination of experiments, computer simulations, and theoretical investigation, a model was built to investigate the fluid dynamics of granular flows in an intermediate regime, where both collisional and frictional interactions may affect the flow behavior. In Part I, experiments were described using a modified Newton’s Cradle device to obtain values for the viscous damping coefficient, which are scarce in the literature. In this paper, molecular dynamic simulations were performed using the simplified model for collisions between particles, developed in Part I, to obtain detailed information about the interparticle interactions. This information was used to develop a continuum model for granular flows, accounting for both collisional and frictional interactions between particles. To validate the continuum model, simulations were performed for the specific case of granular flow in a rapidly spinning bucket. The model was able to reproduce experimentally observed flow phenomena in buckets spinning at high frequencies (higher than 50 Hz), such as the transition from a cusp to a depression in the center of the bucket with increasing rotation rate. This agreement suggests that the model may be a useful tool for the prediction of dense granular flows in industrial applications, but highlights the need for further experimental investigation of granular flows in order to refine the model.

scholarly journals Machine Learning for Fluid Mechanics

2020 ◽  
Vol 52 (1) ◽  
pp. 477-508 ◽  
Author(s):  
Steven L. Brunton ◽  
Bernd R. Noack ◽  
Petros Koumoutsakos
Keyword(s):  
Machine Learning ◽  
Fluid Mechanics ◽  
Domain Knowledge ◽  
Large Scale ◽  
Past History ◽  
Fluid Flows ◽  
Field Measurements ◽  
Industrial Applications ◽  
Current Lines ◽  
Large Scale Simulations

The field of fluid mechanics is rapidly advancing, driven by unprecedented volumes of data from experiments, field measurements, and large-scale simulations at multiple spatiotemporal scales. Machine learning (ML) offers a wealth of techniques to extract information from data that can be translated into knowledge about the underlying fluid mechanics. Moreover, ML algorithms can augment domain knowledge and automate tasks related to flow control and optimization. This article presents an overview of past history, current developments, and emerging opportunities of ML for fluid mechanics. We outline fundamental ML methodologies and discuss their uses for understanding, modeling, optimizing, and controlling fluid flows. The strengths and limitations of these methods are addressed from the perspective of scientific inquiry that considers data as an inherent part of modeling, experiments, and simulations. ML provides a powerful information-processing framework that can augment, and possibly even transform, current lines of fluid mechanics research and industrial applications.

The Granular Lubricated Journal Bearing: Evidence of Lift Formation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Venkata K. Jasti ◽  
Martin C. Marinack ◽  
Deepak Patil ◽  
C. Fred Higgs
Keyword(s):  
Carrying Capacity ◽  
Granular Flow ◽  
High Speed ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Flow Behavior ◽  
Extreme Environments ◽  
Granular Flows ◽  
Load Carrying Capacity ◽  
Load Carrying

This work demonstrates that granular flows (i.e., macroscale, noncohesive spheres) entrained into an eccentrically converging gap can indeed actually exhibit lubrication behavior as prior models postulated. The physics of hydrodynamic lubrication is quite well understood and liquid lubricants perform well for conventional applications. Unfortunately, in certain cases such as high-speed and high-temperature environments, liquid lubricants break down making it impossible to establish a stable liquid film. Therefore, it has been previously proposed that granular media in sliding convergent interfaces can generate load carrying capacity, and thus, granular flow lubrication. It is a possible alternative lubrication mechanism that researchers have been exploring for extreme environments, or wheel-regolith traction, or for elucidating the spreadability of additive manufacturing materials. While the load carrying capacity of granular flows has been previously demonstrated, this work attempts to more directly uncover the hydrodynamic-like granular flow behavior in an experimental journal bearing configuration. An enlarged granular lubricated journal bearing (GLJB) setup has been developed and demonstrated. The setup was made transparent in order to visualize and video capture the granular collision activity at high resolution. In addition, a computational image processing program has been developed to process the resulting images and to noninvasively track the “lift” generated by granular flow during the journal bearing operation. The results of the lift caused by granular flow as a function of journal rotation rate are presented as well.

scholarly journals Impinging jets – a short review on strategies for heat transfer enhancement

2018 ◽  
Vol 32 ◽  
pp. 01013
Author(s):  
Ilinca Nastase ◽  
Florin Bode
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Short Review ◽  
Great Difficulty ◽  
Impinging Jets ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Small Scale ◽  
Strong Shear ◽  
Flow Phenomena

In industrial applications, heat and mass transfer can be considerably increased using impinging jets. A large number of flow phenomena will be generated by the impinging flow, such as: large scale structures, large curvature involving strong shear and normal stresses, stagnation in the wall boundary layers, heat transfer with the impinged wall, small scale turbulent mixing. All these phenomena are highly unsteady and even if nowadays a substantial number of studies in the literature are dedicated, the impinging jets are still not fully understood due to the highly unsteady nature and more over due to great difficulty of performing detailed numerical and experimental investigations.

Numerical Simulation of Inner Flow in a Double Blades Pump Based on OpenFOAM and its PIV Verification

2012 ◽  
Author(s):  
Yun Ren ◽  
Houlin Liu ◽  
Kai Wang ◽  
Minggao Tan ◽  
Denghao Wu ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Flow Behavior ◽  
Energy Performance ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Complex Flow ◽  
Unstable Flow ◽  
Software Packages ◽  
Flow Phenomena ◽  
Particle Imaging

The presence of unstable flow phenomena may significantly alter the flow pattern and characteristics of centrifugal pumps; that is, the unstable flows may seriously deteriorate the pumps performance. In this paper, considering the high cost of running license fees and not available with all the computing resources, a high quality Open Source CFD simulation platform like OpenFOAM instead of commercial software packages is adopted. Furthermore, the required capability such as GGI is added and boundary conditions are specialized to better simulate complex flow behavior through rotor-stator components in a double blades pump, whose specific speed is 115.6. In order to disclose the characteristics completely, six research schemes are developed and are now presented in this paper. The ratios (Q/Qd) of the flow rate are 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, respectively. The task mainly focuses on the comparison of energy performance under different operating conditions between numerical calculations and experiments, the analysis of the inner flow in the impeller and the comparison of the velocity field in the impeller mid-height between simulation data and the Particle Imaging Velocimetry (PIV) experimental data. The results show that good agreements are found both in terms of the energy performance with experimental results and computed velocities with the PIV data, but improvements can be made.

An Investigation of the Effect of Swirl Vane Angle on Fuel Concentration and Velocity Fields in Gas Turbine Mixers

2005 ◽  
Author(s):  
Louis J. Turek ◽  
Robert W. Dawson ◽  
Marcos Chaos ◽  
Ruey-Hung Chen
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Flow Behavior ◽  
Flux Ratio ◽  
Industrial Applications ◽  
Concentration Profiles ◽  
Concentration Data ◽  
Operational Conditions ◽  
Mixing Performance ◽  
Fuel Concentration

The flow fields of two different Siemens-Westinghouse gas turbine mixers were studied experimentally in an effort to better understand fuel-air mixing in confined swirling flows found in industrial applications. The mixers consist of an annular flow region and mixing is achieved using swirl vanes, the pressure side of which is used to inject the fuel. The difference between the two mixers studied is the degree of swirl imparted on the flow by the swirl vanes (45° vs. 55°). Velocity (both axial and azimuthal) and fuel concentration profiles were obtained for non-reacting, atmospheric pressure flows at several axial and radial locations downstream of the swirl vanes by the use of LDV and infrared laser light absorption techniques, respectively. The fuel used in this work was a methane/air mixture, which was injected at a momentum flux ratio comparable to that under operational conditions. Results show that flow uniformity, as evidenced by velocity and fuel concentration profiles, is reached further downstream of the swirl vanes for the 45° mixer than for the 55° mixer. This indicates a lesser mixing performance in the 45° mixer. The axial and azimuthal RMS velocities were consistently higher for the 55° degree mixer and this was a likely contributor to its superior mixing performance. High velocity and fuel concentration gradients are common for both mixers and present in the near-field region close to the swirl vanes. The data obtained indicates that the flow behavior in the region near the swirl vanes strongly influences the mixing of the fuel and air. Frequency analysis of the fuel concentration data shows that some turbulent structures prevail throughout the mixing region in both mixers, revealing that some large scale flow features emanating from the swirl vanes are not dissipated even in the high degree of swirl hardware. Lastly, unmixedness levels in both mixers tested are calculated and compared with a discussion on how they might impact NOx emission levels.

scholarly journals A Model for Scaling Avalanche Speeds

1990 ◽  
Vol 36 (123) ◽  
pp. 188-198 ◽  
Author(s):  
D.M. Mcclung
Keyword(s):  
High Precision ◽  
Granular Flow ◽  
Granular Flows ◽  
Field Measurements ◽  
Snow Avalanche ◽  
Steep Gradient ◽  
Dense Granular Flows

AbstractSnow-avalanche speeds, run-out distances, and the concepts from dense granular flows are combined in a model for prediction of speeds along the incline. Field measurements indicate that speeds and run-out distances are nearly independent of path steepness once a length is chosen to scale them. Application of granular-flow concepts explains these results. The most important feature of the model (and the speed data) is the steep gradient of speeds in the run-out zone. These results emphasize the need for high precision in run-out prediction when construction or defences are contemplated.

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