scholarly journals The effect of boundary roughness on dense granular flows

2021 ◽  
Vol 249 ◽  
pp. 03014
Author(s):  
Farnaz Fazelpour ◽  
Karen E. Daniels
Keyword(s):  
Granular Flows ◽  
Coarse Graining ◽  
Pressure Profile ◽  
Stress Profile ◽  
Flow Profile ◽  
Granular Rheology ◽  
Shear Stress Profile ◽  
Rate Profile ◽  
Open Question ◽  
Boundary Roughness

In the field of granular rheology, an important open question is to understand the influence of boundary conditions on granular flows. We perform experiments in a quasi-2D annular shear cell subject to 6 different boundaries with controlled roughness/compliance. We characterize the granular slip at the boundaries to investigate which aspects of a dense granular flow can be controlled by the choice of boundary condition. Photoelastic techniques are implemented to measure the stress fields P(r) and τ(r) throughout the material. A full inverse-analysis of the fringes within each disk provides the vector force at each contact. This allows us to measure the continuum stress field by coarse-graining internal forces. We have observed that boundary roughness and compliance strongly controls the flow profile v(r) and shear rate profile γ˙(r). We also observed that boundary roughness and compliance play a significant role in the pressure profile P(r) and shear stress profile τ(r).

Shear-Stress Profile along a Cell Focal Adhesion

2006 ◽  
Vol 18 (12) ◽  
pp. 1537-1540 ◽  
Author(s):  
D. Raz–Ben Aroush ◽  
H. D. Wagner
Keyword(s):  
Shear Stress ◽  
Focal Adhesion ◽  
Stress Profile ◽  
Shear Stress Profile ◽  
A Cell

scholarly journals Free Convection in Heat Transfer Flow over a Moving Sheet in Alumina Water Nanofluid

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Padam Singh ◽  
Manoj Kumar
Keyword(s):  
Free Convection ◽  
Physical Parameters ◽  
Stress Profile ◽  
Distribution Profile ◽  
Electrically Conducting ◽  
Runge Kutta Method ◽  
Mhd Boundary Layer ◽  
Shear Stress Profile ◽  
Layer Flow ◽  
Mhd Boundary Layer Flow

The present paper deals with study of free convection in two-dimensional magnetohydrodynamic (MHD) boundary layer flow of an incompressible, viscous, electrically conducting, and steady nanofluid. The governing equations representing fluid flow are transformed into a set of simultaneous ordinary differential equations by using appropriate similarity transformation. The equations thus obtained have been solved numerically using adaptive Runge-Kutta method with shooting technique. The effects of physical parameters like magnetic parameter, temperature buoyancy parameter on relative velocity and temperature distribution profile, shear stress profile, and temperature gradient profile were depicted graphically and analyzed. Significant changes were observed due to these parameters in velocity and temperature profiles.

Numerical Analysis on the Refractory Wear of the Blast Furnace Main Trough

2014 ◽  
Vol 92 ◽  
pp. 294-300 ◽  
Author(s):  
Ca Min Chang ◽  
Yon Sen Lin ◽  
Chien Nan Pan ◽  
Wen Tung Cheng
Keyword(s):  
Shear Stress ◽  
Blast Furnace ◽  
Erosion Rate ◽  
Three Dimensional ◽  
Stress Profile ◽  
Refractory Wear ◽  
Main Trough ◽  
Split Operator ◽  
Shear Stress Profile ◽  
Volume Method

This study aims to numerically analyze the refractory wear of the blast furnace main trough. The three dimensional transient Navier-Stocks equation associated with the volume of fluid (VOF) was developed to describe the flow fields of air, molten iron and slag in the main trough of the blast furnace during tapping process; and then solved by the finite volume method (FVM) subject to the pressure implicit with split operator (PSIO). Based on the Newton’s law of viscosity, the computed shear stress profile in the impingement region consists with the erosion rate of main trough from the no. 4 blast furnace at China Steel Corporation (CSC BF4). The influence of the tapping angle and the ratio of iron to slag in tapping stream on the wall shear stress of main trough was also examined for the suggestion to minimize the refractory wear of blast furnace main trough in this work.

scholarly journals Measurements and one-dimensional model calculations of snow transport over a mountain ridge

2001 ◽  
Vol 32 ◽  
pp. 153-158 ◽  
Author(s):  
J. Doorschot ◽  
N. Raderschall ◽  
M. Lehning
Keyword(s):  
Wind Speed ◽  
Turbulent Shear ◽  
Stress Profile ◽  
Mountain Ridge ◽  
Model Calculations ◽  
One Dimensional ◽  
Turbulent Shear Stress ◽  
Shear Stress Profile ◽  
Snow Distribution ◽  
Snow Transport

AbstractWind transport of snow can cause an additional snow load on leeward slopes, which often has a considerable influence on avalanche danger. For a quantitative assessment of this process, a model is proposed which calculates the snow transport over a two-dimensional mountain ridge, based on input measurements of wind speed and precipitation. Since the topography is idealized, the model is focused on the snow mass that is transported over the ridge, and no statements are made about the exact snow distribution over the slopes. Three transport modes are distinguished: snow transport in saltation, snow transport in Suspension, and preferential deposition of precipitation. Suspension is modelled with a one-dimensional diffusion equation, and for the saltation layer a newly developed model, based on the microscale physical processes, is implemented. The effect of speed-up of the wind over the ridge is included by assuming an analytical wind profile with a maximum wind speed at a few meters above the ridge Advective effects are taken into account in a parameterization of the turbulent shear stress profile. The model is compared with measurements taken at the experimental snowdrift site Gaudergrat in the Parsenn area, Switzerland, and good agreement is obtained between calculated and measured results.

Observations of grain-scale interactions and simulation of dry granular flows in a large-scale flume

2015 ◽  
Vol 52 (5) ◽  
pp. 638-655 ◽  
Author(s):  
Sarah K. Bryant ◽  
W. Andy Take ◽  
Elisabeth T. Bowman
Keyword(s):  
Slip Velocity ◽  
Large Scale ◽  
Granular Flows ◽  
Stress Transfer ◽  
Material Source ◽  
Interface Friction ◽  
Scale Interactions ◽  
Basal Friction ◽  
Boundary Roughness ◽  
Single Set

A series of 30 tests on dry granular flows were performed using a large-scale flume under varying source volumes and basal friction conditions to capture grain-scale interactions and their impact on overall runout behaviour. These grain interactions and ultimately the flow regimes developed were found to be a function of material source volume and boundary roughness. The dimensionless inertial number was computed for each flow, but was found to be of limited utility except perhaps to define a general state (e.g., liquid regime) for the material due to the high slip velocity encountered in the granular flows. Using the depth-averaged “dynamic analysis” numerical model DAN, it was found that a single set of semi-empirically derived frictional parameters (i.e., specific to internal and basal friction conditions) was appropriate for matching the overall mobility of the experimental flows over a range of flow volumes and slope inclinations. However, these angles were found to be lower than those determined from laboratory interface friction tests, highlighting the importance of collisional stress transfer in the basal zone of the dry flowing landslides.

scholarly journals Impaired handgrip exercise-induced brachial artery flow-mediated dilation in young obese males

2016 ◽  
Vol 41 (5) ◽  
pp. 528-537 ◽  
Author(s):  
David J. Slattery ◽  
Troy J.R. Stuckless ◽  
Trevor J. King ◽  
Kyra E. Pyke
Keyword(s):  
Shear Stress ◽  
Brachial Artery ◽  
Reactive Hyperemia ◽  
Obese Group ◽  
Stress Profile ◽  
Flow Mediated Dilation ◽  
Handgrip Exercise ◽  
Brachial Artery Diameter ◽  
Shear Stress Profile ◽  
Forearm Occlusion

Flow mediated dilation (FMD) stimulated by different shear stress stimulus profiles may recruit distinct transduction mechanisms, and provide distinct information regarding endothelial function. The purpose of this study was to determine whether obesity influences brachial artery FMD differently depending on the shear stress profile used for FMD assessment. The FMD response to a brief, intermediate, and sustained shear stress profile was assessed in obese (n = 9) and lean (n = 19) young men as follows: brief stimulus, standard reactive hyperemia (RH) following a 5 min forearm occlusion (5 min RH); intermediate stimulus, RH following a 15 min forearm occlusion (15 min RH); sustained stimulus, 10 min of handgrip exercise (HGEX). Brachial artery diameter and mean shear stress were assessed using echo and Doppler ultrasound, respectively, during each FMD test. There was no group difference in HGEX shear stress (p = 0.390); however, the obese group had a lower HGEX-FMD (5.2 ± 3.0% versus 11.5 ± 4.4%, p < 0.001). There was no group difference in 5 min RH-FMD (p = 0.466) or 15 min RH-FMD (p = 0.181); however, the shear stress stimulus was larger in the obese group. After normalization to the stimulus the 15 min RH-FMD (p = 0.002), but not the 5 min RH-FMD (p = 0.118) was lower in the obese group. These data suggest that obesity may have a more pronounced impact on the endothelium’s ability to respond to prolonged increases in shear stress.

Streamwise development of turbulent boundary-layer drag reduction with polymer injection

2008 ◽  
Vol 597 ◽  
pp. 31-66 ◽  
Author(s):  
Y. X. HOU ◽  
V. S. R. SOMANDEPALLI ◽  
M. G. MUNGAL
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Turbulent Boundary Layer ◽  
Drag Reduction ◽  
Reynolds Shear Stress ◽  
Depletion Region ◽  
Stress Profile ◽  
Total Stress ◽  
Polymer Injection ◽  
Shear Stress Profile

Zero-pressure-gradient turbulent boundary-layer drag reduction by polymer injection has been studied with particle image velocimetry. Flow fields ranging from low to maximum drag reduction have been investigated. A previously developed technique – the (1 − y/δ) fit to the total shear stress profile – has been used to evaluate the skin friction, drag reduction and polymer stress. Current results agree well with the semi-log plot of drag reduction vs. normalized polymer flux which has been used by previous workers and can be used as a guide to optimize the use of polymer from a single injector. Detailed flow-field statistics show many special features that pertain to polymer flow. It is shown that the mean velocity responds quickly to the suddenly reduced wall shear stress associated with polymer injection. However, it takes a much longer time for the entire Reynolds shear stress profile to adjust to the same change. The Reynolds shear stress profiles in wall units can be higher than unity and this unique feature can be used to further judge whether the flow is in equilibrium. The streamwise evolution of drag reduction magnitude is used to divide the flow into three regions: development region; steady-state region; and depletion region. The polymer stress is estimated and found to be proportional to drag reduction in the depletion region, but not necessarily so in the other regions. The interaction between injected polymer and turbulent activity in a developing boundary-layer flow is dependent upon the flow history and it produces an equally complex relationship between polymer stress and drag reduction. The stress balance in the boundary layer and the dynamical contribution of the various stresses to the total stress are evaluated and it is seen that the polymer stresses can account for up to 25% of the total stress. This finding is in contrast to channel flows with homogeneous polymer injection where the polymer stress is found to account for up to 60% of the total stress.

Sign in / Sign up

Export Citation Format

Share Document