Non-linear rolling friction of a tyre-caster system: analysis of a rugby wheelchair

2011 ◽  
Vol 225 (4) ◽  
pp. 1015-1020 ◽  
Author(s):  
J J C Chua ◽  
F K Fuss ◽  
A Subic
Keyword(s):  
Friction Coefficient ◽  
Wind Tunnel ◽  
System Analysis ◽  
Aerodynamic Drag ◽  
Rolling Friction ◽  
Constant Component ◽  
Wind Tunnel Experiments ◽  
Non Linear ◽  
The One ◽  
Rolling Friction Coefficient

Tyre-caster systems such as wheelchairs consist of several components with different bearing and rolling friction, with the latter depending on the tyre pressure. The aim of this study was to determine the rolling friction of a rugby wheelchair with deflated and maximally inflated tyres. The rolling friction was determined with coast-down tests by instrumenting the wheelchair with an accelerometer. As the energy loss of coasting down comes primarily from the rolling friction and aerodynamic drag, the latter (including the lift) was determined using wind tunnel experiments. The ratio of the sum of horizontal forces (drag and inertial) to the sum of vertical forces (lift and gravitational) determined the rolling friction coefficient. The rolling friction coefficient expressed as a function of the velocity was found to be highly non-linear, consisting of an initial viscous spike at low velocities, a constant component, and a parabolic component increasing with velocity. The rolling friction coefficient of the wheelchair with deflated tyres was on average three times higher than the one with maximally inflated tyres.

scholarly journals Research on the Mechanical Efficiency of High-Speed 2D Piston Pumps

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 853 ◽  
Author(s):  
Yu Huang ◽  
Jian Ruan ◽  
Chenchen Zhang ◽  
Chuan Ding ◽  
Sheng Li
Keyword(s):  
Friction Coefficient ◽  
High Speed ◽  
High Pressures ◽  
Weight Ratio ◽  
Rolling Friction ◽  
Mechanical Efficiency ◽  
Load Pressure ◽  
Axial Piston Pumps ◽  
Series Of Experiments ◽  
Rolling Friction Coefficient

Since many studies on axial piston pumps aim at enhancing their high power-weight ratio, many researchers have focused on the generated mechanical losses by the three friction pairs in such pumps and attempted to diminish them through abundant and new structural designs of the pump’s components. In this paper, a high-speed 2D piston pump is introduced and its architecture is specifically described. Afterward, a mathematical model is established to study the pump’s mechanical efficiency, including the mechanical losses caused by the viscosity and stirring oil. Additionally, in this study the influences of the rotational speed, the different load pressures, and the rolling friction coefficient between the cone roller and the guiding rail are considered and discussed. By building a test rig, a series of experiments were carried out to prove that the mechanical efficiency was accurately predicted by this model at low load pressures. However, there was an increasing difference between the test results and the analytical outcomes at high pressures. Nevertheless, it is still reasonable to conclude that the rolling friction coefficient changes as the load pressure increases, which leads to a major decrease in the mechanical efficiency in experiments.

scholarly journals Influence of Rolling Friction Coefficient on Inter-Particle Percolation in a Packed Bed by Discrete Element Method

2016 ◽  
Vol 61 (4) ◽  
pp. 1795-1804
Author(s):  
Heng Zhou ◽  
Zhiguo Luo ◽  
Tao Zhang ◽  
Yang You ◽  
Haifeng Li ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Discrete Element Method ◽  
Dispersion Coefficient ◽  
Packed Bed ◽  
Discrete Element ◽  
Rolling Friction ◽  
Size Ratio ◽  
Longitudinal Dispersion ◽  
Longitudinal Dispersion Coefficient ◽  
Rolling Friction Coefficient

Abstract Rolling friction representing the energy dissipation mechanism with the elastic deformation at the contact point could act directly on particle percolation. The present investigation intends to elucidate the influence of rolling friction coefficient on inter-particle percolation in a packed bed by discrete element method (DEM). The results show that the vertical velocity of percolating particles decreases with increasing the rolling friction coefficient. With the increase of rolling friction coefficient, the transverse dispersion coefficient decreases, but the longitudinal dispersion coefficient increases. Packing height has a limited effect on the transverse and longitudinal dispersion coefficient. In addition, with the increase of size ratio of bed particles to percolation ones, the percolation velocity increases. The transverse dispersion coefficient increases with the size ratio before D/d<14. And it would keep constant when the size ratio is greater than 14. The longitudinal dispersion coefficient decreases when the size ratio increases up to D/d=14, then increases with the increase of the size ratio. External forces affect the percolation behaviours. Increasing the magnitude of the upward force (e.g. from a gas stream) reduces the percolation velocity, and decreases the dispersion coefficient.

scholarly journals Pre-service teachers’ conceptual understanding of rolling friction coefficient

2018 ◽  
Author(s):  
Puspita Septim Wulandari ◽  
C. Cari ◽  
Nonoh Siti Aminah ◽  
Dewanta Arya Nugraha
Keyword(s):  
Friction Coefficient ◽  
Conceptual Understanding ◽  
Rolling Friction ◽  
Rolling Friction Coefficient

Discrete Element Modeling of Seed Metering as Affected by Roller Speed and Damping Coefficient

2020 ◽  
Vol 63 (1) ◽  
pp. 189-198
Author(s):  
Leno J. Guzman ◽  
Ying Chen ◽  
Hubert Landry
Keyword(s):  
Friction Coefficient ◽  
Mass Flow ◽  
Discrete Element ◽  
Rolling Friction ◽  
Angle Of Repose ◽  
Discrete Element Modeling ◽  
Flow Rates ◽  
Damping Coefficients ◽  
Mass Flow Rates ◽  
Rolling Friction Coefficient

Abstract. The development of highly efficient seed metering is required to meet the demands of modern seeding equipment. The discrete element method (DEM) was used to simulate metering of seeds with a fluted roller meter. This approach was chosen due to its capability to accurately represent granular material flow. The contact model selected for the DEM simulation was the linear rolling resistance model. Angle of repose experimental tests and simulations were performed to calibrate the rolling friction coefficient for peas. The calibrated value for the rolling friction coefficient was 0.016. A 192 mm cross-section of an air cart seed roller and housing was defined as the domain of the simulation. Sensitivity analysis showed that simulated mass flow rates were not sensitive to the selected damping coefficients (0.2, 0.5, and 0.8). Sensitivity indicator values varied between -0.049 and 0.088 for the range of damping coefficients and roller speeds studied. The simulated geometry of the seed meter and housing resulted in a steady flow of seeds, with discharged mass increasing linearly. The simulated mass flow rates were 34.0, 72.3, 110.4, 147.3, and 182.0 g s-1 for roller speeds of 10, 20, 30, 40, and 50 rpm, respectively. An experiment was performed to validate the simulation results. The predicted mass flow rate values of the simulation were within 10 g s-1 of the experimental results, with the largest relative error being 16.5%. Keywords: DEM, Damping, Metering, Peas, Rolling friction coefficient, Seed, Simulation.

Influence of Shape and Particle Size Distribution on Discrete Element Simulation Flow Characteristics of Granular Compound Fertilizers

2021 ◽  
Vol 37 (6) ◽  
pp. 1169-1179
Author(s):  
Wenli Xiao ◽  
Hui Chen ◽  
Xingyu Wan ◽  
Mengliang Li ◽  
Qingxi Liao
Keyword(s):  
Particle Size ◽  
Friction Coefficient ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Golden Section ◽  
Discrete Element ◽  
Rolling Friction ◽  
Angle Of Repose ◽  
Compound Fertilizer ◽  
Rolling Friction Coefficient

HighlightsThe relationship between the angle of repose and compound fertilizer particle size distribution and sphericity was revealed.The range of the rolling friction coefficient obtained by different modeling was calibrated by the golden section method.Scanning modeling required 80% of the rolling friction coefficient of spherical modeling to reflect actual motion.The relative error of scanning modeling (7.91%) was better than that of spherical modeling (30.84%).Abstract. The discrete element method (DEM) is widely used to simulate the behavior of granular materials. The accurate establishment of the particle model has a great influence on the accuracy of the simulation. Most of the existing discrete element simulations of granular compound fertilizers use spherical modeling without considering the shape or particle size distribution. To compare the simulation accuracy of spherical modeling (spherical particles with equivalent diameters) and scanning modeling (a three-dimensional model of fertilizers was obtained by a scanner and then automatically filled by EDEM2020 software) on compound fertilizer discharge, three kinds of granular compound fertilizers (Changqingshu, Xinshidai, and Munvhong) were selected as the research objects. The characterization parameters of fertilizer shape and fluidity were measured. Principal component analysis and Pearson correlation analysis were used to analyze the influence of the compound fertilizer characterization parameters on the angle of repose. The results showed that the particle shape and particle size distribution of compound fertilizer were the main factors affecting its angle of repose. Through the golden section method and a single-factor experiment, the rolling friction coefficients of the three granular fertilizers under the two granular modeling methods for spherical modeling and scanning modeling were determined. The results showed that the rolling friction coefficient when using scanning modeling to approximate the actual angle of repose was approximately 80% of that when using the spherical modeling method. The influence of different modeling methods on the total rotational kinetic energy and the formation of the angle of repose was discussed. For the same fertilizer, the total rotational kinetic energy was greater in spherical modeling than in scanning modeling, and the formation time of the angle of repose was longer in scanning modeling than in spherical modeling. The results of an external tank wheel fertilization simulation and bench test showed that considering the scanning modeling of fertilizer shape and particle size distribution, the fertilization variation coefficient obtained from the simulation test was closer to that of the bench test. This research helps to better understand the influence of particle shape and particle size distribution on DEM simulations and provides references for discrete element modeling of other granular fertilizers. Keywords: Compound fertilizer, Modeling method, Shape, Simulated flow characteristics, Size distribution.

Calibration and Experimental Validation of Contact Parameters for Oat Seeds for Discrete Element Method Simulations

2021 ◽  
Vol 37 (4) ◽  
pp. 605-614
Author(s):  
Lingxin Geng ◽  
Jiewen Zuo ◽  
Fuyun Lu ◽  
Xin Jin ◽  
Chenglong Sun ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Discrete Element Method ◽  
Static Friction ◽  
Discrete Element ◽  
Rolling Friction ◽  
Angle Of Repose ◽  
Static Friction Coefficient ◽  
Contact Parameters ◽  
Rolling Friction Coefficient ◽  
Element Method

Highlights The static friction coefficient and rolling friction coefficient of oat seeds were calibrated by the discrete element method. Two representative oat varieties were selected. The hollow cylinder method and sidewall collapse method were used together to reduce the test error. Abstract . Hulless and shelled oat are two types of oat with major differences in physical appearance. To study the contact parameters between the two different oat seed types, these parameters were delineated with the discrete element method and graphic image processing technology. Using plexiglass as the contact material, the experiments used two different angle of repose measurement methods—hollow cylinder and collapse sidewall devices, to perform bench and simulation experiments on the two different oats. Under different measurement methods, bench experiments measured the angles of repose of the two oat seed types at 33.19°, 33.82° and 22.45°, 23.57°; the static friction coefficient and rolling friction coefficient were the experimental factors, and the angle of repose was the experimental indicator in the simulation. The steepest climbing experiment determined the optimal range of the experimental factor, and the regression equation between the static friction coefficient, rolling friction coefficient and angle of repose was established by a quadratic orthogonal rotation combination experiment. Finally, the angles of repose measured by the bench experiment with the two different measurement methods were treated as target values, the coefficient of static friction and the coefficient of rolling friction were solved; the coefficient of static friction between hulless oats was 0.36, and the coefficient of rolling friction between hulless oats was 0.052; the coefficient of static friction between shelled oats was 0.24, and the coefficient of rolling friction between shelled oats was 0.036. The obtained contact parameters between seeds were input into EDEM, the simulation and bench experiment results were verified. The difference between the simulation results and the actual values was within 3%. The angle of repose of oats after calibration was close to the actual situation, and the calibration results had high reliability and provided a referencefor the measurement of contact parameters between other agricultural crop seeds. Keywords: Calibration, Contact parameters, Discrete element method, Oat.

Design on Disc Cam Mechanism of Roller Follower

2010 ◽  
Vol 33 ◽  
pp. 631-635
Author(s):  
A.P. Hu ◽  
D.J. Kong ◽  
W. Zhu
Keyword(s):  
Friction Coefficient ◽  
Rolling Friction ◽  
Rolling Motion ◽  
Relative Movement ◽  
Cam Mechanism ◽  
Base Circle ◽  
The Common ◽  
Roller Radius ◽  
Rolling Friction Coefficient ◽  
Inappropriate Choice

The requirements on the movement law of the follower imposed by disc cam mechanism of roller follower are considered, and the influencing factors of the relative motion between the roller and the cam contour are investigated. The requirements on the roller radius for the rolling motion of the roller that is relative to the cam contour are analyzed. It can be found that the constant speed movement, one of the common follower motion laws, cannot be applied alone to roller follower disc cam mechanism; otherwise movement distortion for the follower will happen. The movement distortion caused by inappropriate choice of the movement law can not be avoided by increasing cam base circle radius or by decreasing roller radius. There is a required minimum roller radius for the relative movement between the roller and the cam contour to be rolling movement. The minimum radius is inversely proportional to the rolling friction coefficient between the roller and the cam contour, proportional to the radius of the friction circle of the revolute pair between the roller and the follower lever, and independent of the load of the cam mechanism, pressure angle and other dimension parameters.

Examining the Aerodynamic Drag and Lift Characteristics of a Newly Developed Elliptical-Bladed Savonius Rotor

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Nur Alom ◽  
Ujjwal K. Saha
Keyword(s):  
Wind Tunnel ◽  
Stokes Equations ◽  
Aerodynamic Drag ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Wind Tunnel Experiments ◽  
Drag Forces ◽  
Velocity Magnitude ◽  
Bladed Rotor ◽  
Drag And Lift

The elliptical-bladed Savonius wind turbine rotor has become a subject of interest because of its better energy capturing capability. Hitherto, the basic parameters of this rotor such as overlap ratio, aspect ratio, and number of blades have been studied and optimized numerically. Most of these studies estimated the torque and power coefficients (CT and CP) at given flow conditions. However, the two important aerodynamic forces, viz., the lift and the drag, acting on the elliptical-bladed rotor have not been studied. This calls for a deeper investigation into the effect of these forces on the rotor performance to arrive at a suitable design configuration. In view of this, at the outset, two-dimensional (2D) unsteady simulations are conducted to find the instantaneous lift and drag forces acting on an elliptical-bladed rotor at a Reynolds number (Re) = 0.892 × 105. The shear stress transport (SST) k–ω turbulence model is used for solving the unsteady Reynolds averaged Navier–Stokes equations. The three-dimensional (3D) unsteady simulations are then performed which are then followed by the wind tunnel experiments. The drag and lift coefficients (CD and CL) are analyzed for 0–360 deg rotation of rotor with an increment of 1 deg. The total pressure, velocity magnitude, and turbulence intensity contours are obtained at various angles of rotor rotation. For the elliptical-bladed rotor, the average CD, CL, and CP, from 3D simulation, are found to be 1.31, 0.48, and 0.26, respectively. The average CP for the 2D elliptical profile is found to be 0.34, whereas the wind tunnel experiments demonstrate CP to be 0.19.

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