scholarly journals Effect of the Rolling Friction on the Heap Formation of Dry and Wet Coarse Discs

2021 ◽  
Vol 11 (13) ◽  
pp. 6043
Author(s):  
Becaye Cissokho Ndiaye ◽  
Zhengguo Gao ◽  
Massamba Fall ◽  
Yajun Zhang
Keyword(s):  
Kinetic Energy ◽  
Threshold Value ◽  
Rolling Friction ◽  
Liquid Volume ◽  
Liquid Content ◽  
Elastic Plastic ◽  
Wet Particles ◽  
Initial Packing ◽  
Good Agreement ◽  
Number Of Particles

We performed 2D numerical simulations to study the dynamic heap formation of coarse particles in different dry and wet conditions. Our results show that the dynamics of the particles depend not only on the amount of liquid contained in the bulk, but also on the initial particles packing, i.e., the arrangement of the grains. The wet particles cohesion model effect on coarse discs heap formation is minimal. This effect is mostly noticed in the particle arrangement and the energy variation rather than the heap formation. We found that the energy of the system varies with the liquid content up to a threshold value, equal to 219% in our study, where the influences of the parameters are minimal. At high liquid volume, the final pile height and radius tend towards an asymptotic value. The initial particles arrangement has a significant impact on the behavior of the bulk after the opening of the lateral walls. The number of particles in the triangle, formed by the initial width of the packing as a base and with a depth equal to N × D, with N representing the number of particles on a vertical line and D their diameter, influences the final shape of the pile. Indeed, the larger the number, the smaller the height of the pile. The simulations performed with the same initial packing show that the cohesion and capillary forces reduce the bulk kinetic energy and increase the potential energy when used with the elastic-plastic spring dashpot model. For the directional constant model, the dependance of the torque on the normal force and the particle size explains that there is almost no difference between the dry and wet model regarding energies. Finally, the elastic-plastic spring-dashpot model is more efficient in reducing the kinetic energy of the system and producing stable piles. Our simulation results using glass beads are in good agreement with the experiments.

Heat Transfer Committee and Turbomachinery Committee Best Paper of 1996 Award: The Path to Predicting Bypass Transition

1997 ◽  
Vol 119 (3) ◽  
pp. 405-411 ◽  
Author(s):  
R. E. Mayle ◽  
A. Schulz
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Energy Equation ◽  
Free Stream ◽  
Bypass Transition ◽  
Turbulence Level ◽  
Free Stream Turbulence ◽  
Energy Profiles ◽  
Computer Codes ◽  
Good Agreement

A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement. In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level that produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.

Local Density Approximations for the Energy of a Periodic Coulomb Model

2003 ◽  
Vol 13 (08) ◽  
pp. 1185-1217 ◽  
Author(s):  
Olivier Bokanowski ◽  
Benoît Grebert ◽  
Norbert J. Mauser
Keyword(s):  
Kinetic Energy ◽  
Local Density ◽  
Exchange Energy ◽  
Asymptotic Approximations ◽  
Exchange Potential ◽  
Energy Term ◽  
Local Exchange ◽  
Coulomb Model ◽  
Local Density Approximations ◽  
Number Of Particles

We deal with local density approximations for the kinetic and exchange energy term, ℰ kin (ρ) and ℰ ex (ρ), of a periodic Coulomb model. We study asymptotic approximations of the energy when the number of particles goes to infinity and for densities close to the constant averaged density. For the kinetic energy, we recover the usual combination of the von-Weizsäcker term and the Thomas–Fermi term. Furthermore, we justify the inclusion of the Dirac term for the exchange energy and the Slater term for the local exchange potential.

Stability and collapse of holes in liquid layers

2018 ◽  
Vol 855 ◽  
pp. 1130-1155 ◽  
Author(s):  
Cunjing Lv ◽  
Michael Eigenbrod ◽  
Steffen Hardt
Keyword(s):  
Liquid Film ◽  
Power Laws ◽  
Theoretical Models ◽  
Liquid Volume ◽  
Capillary Length ◽  
Minimum Thickness ◽  
The Stability ◽  
Film Profile ◽  
Hole Closure ◽  
Good Agreement

We investigate experimentally and theoretically the stability and collapse of holes in liquid layers on bounded substrates with various wettabilities. It is shown that for a liquid layer with a thickness of the order of the capillary length, a stable hole exists when the hole diameter is bigger than a critical value $d_{c}$. Consequently, a further increase of the liquid volume causes the hole to collapse. It is found that$d_{c}$increases with the size of the container, but its dependence on the contact angle is very weak. The experimental results are compared with theory, and good agreement is obtained. Moreover, we present investigations of the dynamics of the hole and the evolution of the liquid film profile after the collapse. The diameter of the hole during collapse and the minimum thickness of the liquid film shortly after the collapse obey different power laws with time. Simple theoretical models are developed which indicate that the collapse of the hole is triggered by surface tension and the subsequent closure process results from inertia, whereas the growth of the liquid column after hole closure results from the balance between the capillary force and inertia. Corresponding scaling coefficients are determined.

Development and verification of a numerical model for the analysis of geosynthetic-reinforced soil segmental walls under working stress conditions

2005 ◽  
Vol 42 (4) ◽  
pp. 1066-1085 ◽  
Author(s):  
Kianoosh Hatami ◽  
Richard J Bathurst
Keyword(s):  
Numerical Model ◽  
Constitutive Models ◽  
Reinforced Soil ◽  
Stress Conditions ◽  
Soil Reinforcement ◽  
Lagrangian Analysis ◽  
Elastic Plastic ◽  
Geosynthetic Reinforced Soil ◽  
Working Stress ◽  
Good Agreement

The paper describes a numerical model that was developed to simulate the response of three instrumented, full-scale, geosynthetic-reinforced soil walls under working stress conditions. The walls were constructed with a fascia column of solid modular concrete units and clean, uniform sand backfill on a rigid foundation. The soil reinforcement comprised different arrangements of a weak biaxial polypropylene geogrid reinforcement material. The properties of backfill material, the method of construction, the wall geometry, and the boundary conditions were otherwise nominally the same for each structure. The performance of the test walls up to the end of construction was simulated with the finite-difference-based Fast Lagrangian Analysis of Continua (FLAC) program. The paper describes FLAC program implementation, material properties, constitutive models for component materials, and predicted results for the model walls. The results predicted with the use of nonlinear elastic-plastic models for the backfill soil and reinforcement layers are shown to be in good agreement with measured toe boundary forces, vertical foundation pressures, facing displacements, connection loads, and reinforcement strains. Numerical results using a linear elastic-plastic model for the soil also gave good agreement with measured wall displacements and boundary toe forces but gave a poorer prediction of the distribution of strain in the reinforcement layers.Key words: numerical modelling, retaining walls, reinforced soil, geosynthetics, FLAC.

Fluid dynamics of the resonance tube

1970 ◽  
Vol 43 (2) ◽  
pp. 369-384 ◽  
Author(s):  
E. Brocher ◽  
C. Maresca ◽  
M.-H. Bournay
Keyword(s):  
Fluid Dynamics ◽  
Kinetic Energy ◽  
Sound Speed ◽  
Pressure Fluctuations ◽  
Oscillation Amplitude ◽  
Cylindrical Body ◽  
Expansion Phase ◽  
Resonance Tube ◽  
Limiting Value ◽  
Good Agreement

Using a simplified wave-diagram and the gas-speed/sound-speed diagram, it is shown how the oscillations start and grow within a resonance tube. It is found that the oscillation amplitude tends to a limiting value which is obtained when the jet is fully swallowed by the tube during the phase of compression of the cycle. Experiments are carried out for jet Mach numbers from 0·1 up to 2. To achieve an adequate evacuation of the tube in the expansion phase, a thin cylindrical body must be used, which is laid along the axis of the jet to produce a wake and a correlative local deficiency of the kinetic energy of the jet. Measured amplitudes of pressure fluctuations are in good agreement with theoretical values.

The Path to Predicting Bypass Transition

1996 ◽  
Author(s):  
R. E. Mayle ◽  
A. Schulz
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Energy Equation ◽  
Free Stream ◽  
Bypass Transition ◽  
Turbulence Level ◽  
Free Stream Turbulence ◽  
Energy Profiles ◽  
Computer Codes ◽  
Good Agreement

A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement. In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level which produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.

Belt-Drive Mechanics: Energy Losses in the Presence of Detachment Waves

2019 ◽  
Author(s):  
Yingdan Wu ◽  
Michael J. Leamy ◽  
Michael Varenberg
Keyword(s):  
Rolling Friction ◽  
Drive System ◽  
Energy Losses ◽  
Belt Drive ◽  
Interface Shear ◽  
Shear Traction ◽  
Friction Moment ◽  
The Difference ◽  
Contact Arc ◽  
Good Agreement

Abstract The dissipative rolling friction moment in a simple belt-drive system is estimated both experimentally and computationally while taking into account the detachment events at the belt-pulley interface. Shear traction is estimated based on measurements of the shear strain along the contact arc. It is shown that the dissipative moment can be approximated by taking the difference between the shear traction and the load carried by the belt. A model is developed for analyzing the contributions of different components to this dissipative moment by considering both the volumetric and surface hysteresis losses. The computed rolling friction moment is found to be in good agreement with that estimated based on the experiments. It is also found that while the shear- and stretching-induced energy losses contribute the most to the dissipation in the belt drive system, the losses associated with the Schallamach waves of detachment make up a considerable portion of the dissipation in the driver case.

scholarly journals A novel rapid method of purely elastic solution correction to estimate multiaxial elastic-plastic behaviour

2019 ◽  
Vol 6 (3) ◽  
pp. 269-283
Author(s):  
Nicolas Antoni
Keyword(s):  
Three Dimensional ◽  
Elastic Solution ◽  
Upper And Lower Bounds ◽  
Efficient Design ◽  
Effective Parameters ◽  
Relative Deviation ◽  
Elastic Plastic ◽  
Plastic Behaviour ◽  
A New Technique ◽  
Good Agreement

Abstract In structural analysis, it is of paramount importance to assess the level of plasticity a structure may experience under monotonic or cyclic loading as this may have a significant impact, particularly in fatigue analysis for singular areas. For efficient design analyses, it is often searched for a compromise in accuracy that consists in correcting a purely elastic analysis, generally simpler and faster to obtain compared to a full non-linear Finite Element (FE) analysis involving elastic-plastic behaviour, to estimate the actual elastic-plastic solution. There exists a great number of correction techniques in the literature among which the most famous and commonly used are Neuber and ESED energy-based methods. Nonetheless, both of them are known to provide respectively upper and lower bounds of the exact solution in most cases, with a relative deviation depending on the level of multiaxiality and on the amount of stress redistribution due to yielding. The new methodology presented in this paper is based on the well-known multiaxial Radial Return Method (RRM) revisited using effective parameters approach. By essence, it is fast and can be applied either to analytical elastic problems or to more complex three-dimensional elastic FE analyses. The accuracy of the proposed method is assessed by direct comparison with results from Neuber and ESED methods on various examples. It is also shown for each of them that this new method is very good agreement with the exact elastic-plastic solution. Highlights A new technique of purely elastic solution correction is presented and evaluated. The proposed method relies on the modification of Return Radial Method (RRM) considering effective parameters in lieu of initial elastic tensor. The obtained equation preserves the simplicity and efficiency of other well-known energy-based methods such as Neuber and ESED. It is shown on several examples that the proposed technique is in very good agreement with the exact or FE elastic-plastic solution, with very low relative deviation.

A CALORIMETRIC DETERMINATION OF THE AVERAGE KINETIC ENERGY OF THE FRAGMENTS FROM U235 FISSION

1955 ◽  
Vol 33 (7) ◽  
pp. 357-363 ◽  
Author(s):  
R. B. Leachman ◽  
W. D. Schafer
Keyword(s):  
Kinetic Energy ◽  
Average Energy ◽  
Fission Products ◽  
Average Kinetic Energy ◽  
U235 Fission ◽  
Induced Fission ◽  
Differential Calorimeter ◽  
Calorimetric Determination ◽  
Good Agreement

The average heat of thermal-neutron induced fission of U235 has been measured by a differential calorimeter. The average energy per fission observed by the calorimeter was 170.1 ± 1.2 Mev. On the basis of the thicknesses of the calorimeter materials and the theoretical energy loss equation, the β energy per fission observed by the calorimeter is 3.0 ± 1 Mev. and, on the same basis, the γ and neutron energy observed is negligible. The resulting 167.1 ± 1.6 Mev. for the average kinetic energy of the fission products is shown to be in good agreement with less direct determinations of this quantity.

Peel Mechanics for an Elastic-Plastic Adherend

1979 ◽  
Vol 52 (5) ◽  
pp. 1057-1071 ◽  
Author(s):  
A. N. Gent ◽  
G. R. Hamed
Keyword(s):  
Energy Dissipation ◽  
Critical Thickness ◽  
Adhesive Layer ◽  
Published Data ◽  
Plastic Yielding ◽  
Plastic Strip ◽  
Elastic Plastic ◽  
Maximum Value ◽  
Good Agreement

Abstract The force required to propagate a 180° bend in an elastic-plastic strip has been calculated from elementary bending theory. Measured forces for Mylar strips of various thicknesses, bent to various degrees, were in good agreement with these calculated values. The corresponding additional stripping force in a peeling experiment will depend upon the thickness of the elastic-plastic adherend, becoming zero both for infinitesimally thin adherends and for those exceeding a critical thickness tc and passing through a maximum value at intermediate thicknesses. Published data are in good agreement with these conclusions. For a strongly adhering strip, higher peel strengths are found for a peel angle of 180°, compared to 90°, and the effect is greater than can be accounted for solely by plastic yielding of the adherend. It is attributed in part to greater energy dissipation within the adhesive layer.

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