Bagnold velocity profile for steady-state dense granular chute flow with base slip

2022 ◽  
Author(s):  
James M. Hill ◽  
Debayan Bhattacharya ◽  
Wei Wu
Keyword(s):  
Steady State ◽  
Velocity Profile ◽  
Chute Flow

Rheology of dense snow flows: Inferences from steady state chute-flow experiments

2008 ◽  
Vol 52 (3) ◽  
pp. 729-748 ◽  
Author(s):  
Pierre G. Rognon ◽  
François Chevoir ◽  
Hervé Bellot ◽  
Frédéric Ousset ◽  
Mohamed Naaïm ◽  
...  
Keyword(s):  
Steady State ◽  
Chute Flow ◽  
Flow Experiments

In-Cylinder Flow Correlations Between Steady Flow Bench and Motored Engine Using Computational Fluid Dynamics

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Xiaofeng Yang ◽  
Tang-Wei Kuo ◽  
Orgun Guralp ◽  
Ronald O. Grover ◽  
Paul Najt
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Steady State ◽  
Velocity Profile ◽  
Discharge Coefficient ◽  
Intake Port ◽  
Charge Motion ◽  
Steady State Flow ◽  
Cfd Simulations ◽  
Motored Engine

Intake port flow performance plays a substantial role in determining the volumetric efficiency and in-cylinder charge motion of a spark-ignited engine. Steady-state flow bench and motored engine flow computational fluid dynamics (CFD) simulations were carried out to bridge these two approaches for the evaluation of port flow and charge motion (such as discharge coefficient, swirl/tumble ratios (SR/TR)). The intake port polar velocity profile and polar physical clearance profile were generated to evaluate the port performance based on local flow velocity and physical clearance in the valve-seat region. The measured data were taken from standard steady-state flow bench tests of an intake port for validation of CFD simulations. It was reconfirmed that the predicted discharge coefficients and swirl/tumble index (SI/TI) of steady flow bench simulations have a good correlation with those of motored engine flow simulations. Polar velocity profile is strongly affected by polar physical clearance profile. The polar velocity inhomogeneity factor (IHF) correlates well with the port discharge coefficient, swirl/tumble index. Useful information can be extracted from local polar physical clearance and velocity, which can help for intake port design.

scholarly journals Self-channelisation and levee formation in monodisperse granular flows

2019 ◽  
Vol 876 ◽  
pp. 591-641 ◽  
Author(s):  
F. M. Rocha ◽  
C. G. Johnson ◽  
J. M. N. T. Gray
Keyword(s):  
Steady State ◽  
Velocity Profile ◽  
Numerical Simulations ◽  
Mass Flux ◽  
Critical Mass ◽  
Granular Flows ◽  
Time Dependent ◽  
Pyroclastic Flows ◽  
Shear Stresses ◽  
Flowing Channel

Dense granular flows can spontaneously self-channelise by forming a pair of parallel-sided static levees on either side of a central flowing channel. This process prevents lateral spreading and maintains the flow thickness, and hence mobility, enabling the grains to run out considerably further than a spreading flow on shallow slopes. Since levees commonly form in hazardous geophysical mass flows, such as snow avalanches, debris flows, lahars and pyroclastic flows, this has important implications for risk management in mountainous and volcanic regions. In this paper an avalanche model that incorporates frictional hysteresis, as well as depth-averaged viscous terms derived from the $\unicode[STIX]{x1D707}(I)$-rheology, is used to quantitatively model self-channelisation and levee formation. The viscous terms are crucial for determining a smoothly varying steady-state velocity profile across the flowing channel, which has the important property that it does not exert any shear stresses at the levee–channel interfaces. For a fixed mass flux, the resulting boundary value problem for the velocity profile also uniquely determines the width and height of the channel, and the predictions are in very good agreement with existing experimental data for both spherical and angular particles. It is also shown that in the absence of viscous (second-order gradient) terms, the problem degenerates, to produce plug flow in the channel with two frictionless contact discontinuities at the levee–channel margins. Such solutions are not observed in experiments. Moreover, the steady-state inviscid problem lacks a thickness or width selection mechanism and consequently there is no unique solution. The viscous theory is therefore a significant step forward. Fully time-dependent numerical simulations to the viscous model are able to quantitatively capture the process in which the flow self-channelises and show how the levees are initially emplaced behind the flow head. Both experiments and numerical simulations show that the height and width of the channel are not necessarily fixed by these initial values, but respond to changes in the supplied mass flux, allowing narrowing and widening of the channel long after the initial front has passed by. In addition, below a critical mass flux the steady-state solutions become unstable and time-dependent numerical simulations are able to capture the transition to periodic erosion–deposition waves observed in experiments.

Spectral properties and universal behaviour of advecting–diffusing scalar fields in finite-length channels

2008 ◽  
Vol 612 ◽  
pp. 387-406 ◽  
Author(s):  
M. GIONA ◽  
S. CERBELLI ◽  
F. CRETA
Keyword(s):  
Steady State ◽  
Velocity Profile ◽  
Finite Length ◽  
Scalar Fields ◽  
Dominant Eigenvalue ◽  
Diffusion Operator ◽  
Stagnation Points ◽  
Molecular Diffusivity ◽  
Parallel Flows ◽  
Relaxation Time Scale

This paper analyses the relaxation towards the steady state of an advecting–diffusing field in a finite-length channel. The dominant eigenvalue, −-ΛF, of the advection–diffusion operator provides the slowest relaxation time scale for achieving steady state in open flow devices. We focus on parallel flows and analyse how ΛF depends on the velocity profile and the molecular diffusivity. As a result of the universal localization features of the eigenfunction associated with ΛF, we find that ΛF can be predicted analytically based on the local behaviour of the velocity profile near the stagnation points. Microfluidic applications of the theory are also addressed.

Some engineering applications of magneto-hydrodynamics

1955 ◽  
Vol 233 (1194) ◽  
pp. 396-401 ◽  
Keyword(s):  
Steady State ◽  
Liquid Metal ◽  
Velocity Profile ◽  
Electromagnetic Flowmeter ◽  
Hydrodynamic Forces ◽  
Conducting Liquid ◽  
Engineering Applications

The sensitivity of an electromagnetic flowmeter depends on the form of the velocity profile, which is affected by upstream conditions and, when the fluid is a highly conducting liquid metal, by magneto-hydrodynamic forces. The steady state of the velocity profile and the distance necessary for it to be reached are predicted and compared with experiment. Other results concern the settling of the motion in a flowmeter downstream of an obstruct.

Sizing Directional Pneumatic Valves Based on the Characteristic Dynamic Behavior of Linear Actuators

2021 ◽  
Author(s):  
Vinícius Vigolo ◽  
Antonio Carlos Valdiero ◽  
Victor Juliano De Negri
Keyword(s):  
Steady State ◽  
Velocity Profile ◽  
Transient State ◽  
Design Parameters ◽  
State Time ◽  
First Order ◽  
Characteristic Behavior ◽  
Pneumatic Valves ◽  
Steady State Time ◽  
Emptying Time

Abstract In this paper, a novel approach to size directional pneumatic valves based on the analysis of the characteristic behavior of pneumatic actuators applied for pick and place tasks is presented. The study evidences the existence of three characteristic times in the displacement of a standard pneumatic actuation system, which are the emptying time, the transient-state time, and the steady-state time. The results also indicate that there is a close correlation between the velocity profile and the relative size of the piston area, where the steady-state time might be negligible when the piston is correctly sized. The emptying time, characterized by the depressurization of the counterpressure chamber, occurs predominantly with choked mass flow rate and constant volume. In this way, an analytical equation to estimate the emptying time has been determined. Moreover, during the transient-state time, the velocity profile is similar to the characteristic behavior of a first order system, therefore, the transient-state time is estimated by the time constant of the system, which was obtained by a linear first order model developed using the fundamental equations that govern the system behavior. The total displacement time, which is a design requirement to size directional valves, can be expressed as the sum of the emptying and transient-state time. Consequently, a set of equations are proposed to size the directional valve using design parameters such as displacement time, piston volume, load force, and supply pressure. The proposed equations were evaluated along with simulation and experimental results, demonstrating their validity and accuracy.

scholarly journals A Trapezoidal Velocity Profile Generator for Position Control Using a Feedback Strategy

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1222 ◽  
Author(s):  
Hong-Jun Heo ◽  
Yungdeug Son ◽  
Jang-Mok Kim
Keyword(s):  
Steady State ◽  
Velocity Profile ◽  
Position Control ◽  
Dynamic Range ◽  
Initial Position ◽  
Time Base ◽  
Position Controller ◽  
Basic Functions ◽  
Trapezoidal Profile ◽  
State Error

Position control is usually achieved using a position controller and a profile generator. The profile generator produces a desired position trajectory from a position reference and predefined profiles. The position controller forces the actual position to trace the generated position trajectory. A time-based profile generator is the most famous profile generator due to its capability of generating various profiles. However, time base difference in analysis and implementation causes a steady-state error. In order to remove the steady-state error, this paper proposes a novel profile generator for a trapezoidal velocity profile generation. The proposed generator is based on a cascaded P-PI position controller which is designed to trace the position reference. A dynamic range limiter is adopted to provide the acceleration and velocity restrictions which are basic functions for generating the trapezoidal profile. In spite of these restrictions, it cannot make a desired velocity profile only using the limiter because deceleration point is inaccurate. To adjust the deceleration point, a feedback compensator is designed which requires the velocity of the deceleration point. The velocity of the deceleration point is estimated from the initial position error. The compensator moves the deceleration point to the appropriate point which can generate the desired velocity profile. The proposed profile generator can remove the steady-state error, and the position response can be easily adjusted to be either overdamped or underdamped by selecting the two gains appropriately. Several experimental results are presented to verify the usefulness of the proposed generator.

scholarly journals Turbulence Modeling Using Z-F Model and RSM for Flow Analysis in Z-SHAPE Ducts

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Mohammed Karbon ◽  
Ahmad K. Sleiti
Keyword(s):  
Steady State ◽  
Velocity Profile ◽  
Flow Velocity ◽  
Flow Separation ◽  
Experimental Results ◽  
Mean Flow ◽  
Flow Velocity Profile ◽  
The Mean ◽  
Mean Flow Velocity ◽  
Flow Reattachment

Turbulent flow in Z-shape duct configuration is investigated using Reynolds stress model (RSM) and ζ-f model and compared to experimental results. Both RSM and ζ-f models are based on steady-state RANS solutions. The focus was on regions where the RSM has over- or underpredicted the flow when compared to the experimental results and on regions where there are flow separations and high turbulence. The performance of predicting the flow reattachment length in each model is studied as well. RSM has shown the mean flow velocity profile results match reasonably well with the experiment. Advanced ζ-f turbulence model is introduced as user-defined function (UDF) code and applied to the Z-shape duct. It is found that the turbulent kinetic energy production in ζ equation is much easier to reproduce accurately. Both mean velocity gradient and local turbulent stress terms are also much easier to be resolved properly. The current research has found that not only ζ-f model takes less time to complete the simulation but also the mean flow velocity profile results are in better agreement with the experimental data than the RSM although both are coupled steady-state RANS. ζ-f model numerically resolved both the flow separation and reattachment regions better than the RSM. The current numerical results from ζ-f model are attractive and encouraging for wall-bounded flow applications where flow separation and flow reattachment are important for the flow mechanism.

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