Effect Of Horizontal Vibration Research Articles

Effect of Horizontal Vibrations and Particle Size on the Packing Density of Multi-Sized Sphere Mixtures: Discrete Element Method Simulation

Abstract Particle packing densification due to vibrations is a common process that occurs in many industrial applications and is beneficial for achieving better mechanical properties in powder metallurgy. However, most of the research up to this point was focused on vibration compaction of uniform-sized or binary particle mixtures, while most actual commercial powders consist of particles of variable sizes. In this work, the packing of multi-sized sphere mixtures under horizontal vibrations is simulated with the help of the discrete element method (DEM). The variations of total and local packing density with vibrations and particle size were investigated. The simulation results suggest that there are optimal values for the two vibration parameters at which the closest packing is obtained. Further increase in the particle size decreases the density and slightly shifts these peaks to the lower values of vibrations. Local density values are quite uniform at the optimal vibration parameters, but the deviations become higher when frequency or amplitude is too low or high. With an increase in particle size, these trends become less profound and more deviated. The investigations of effects of size can help in predicting optimal parameters and density values for experimental studies. These developments are similar to those for uniform and binary particle assemblies and correlate with experimental and numerical studies from the literature. The results can be helpful in carefully choosing the particle mixture properties and vibration conditions for actual manufacturing.

Effect of Horizontal Vibrations on Thermo-Solutocapillary Convection and Free Surface of Liquid Bridge

In this study, effect of lateral vibrations on the thermo-solutocapillary convection and surface behavior in a liquid bridge of toluene/n-hexane solution has been studied numerically under microgravity. The Navier-Stokes equations coupled with the concentration diffusion equation are solved on a staggered grid, and the level set approach is used to capture the deformation of free surface. Present results indicate the interface deformation is convex below the midheight of the liquid bridge and relatively complex at the upper height of the liquid bridge under different frequency vibrations. The lateral vibrations restrain radial and axial velocities on the surface under lateral vibrations with frequencies of 5 Hz and 10 Hz. While the radial and axial velocities on the surface increase under the lateral vibration with frequency of 15 Hz, which illustrates that the effect of lateral vibrations on the free surface has uncertainty.

Effect of horizontal vibrations on mass flow rate and segregation during hopper discharge: discrete element method approach

Vibration is often utilized as a means of initiating and/or controlling flow from hopper in industries dealing with powder/granular materials such as packing, conveying, etc. The effect of horizontal vibration on gravity flow of granular material from conical hopper is modeled using the discrete element method. Material considered in this study includes glass beads of diameter ranging between 0.7 mm and 2.0 mm. The flow dynamics and segregation of material are analyzed for different mixtures characterized based on mass percentage of smaller particles (fines) and multi-component mixtures (binary and ternary) at different vibration parameters. The study includes the influence of vibration frequency, acceleration amplitude, fines percentage, diameter ratio and mixture components on segregation and mass flow rate during vibratory hopper discharge. The extent of segregation is calculated by means of mass fraction of fines inside hopper for different operating conditions. The numerical results indicate that the increase in vibration acceleration at a fixed frequency results into increased mass flow rate and there exists acceleration amplitude beyond which segregation is predominant. Mixture components play significant role in segregation behaviour and binary mixture suffers more segregation as compared to ternary mixture. The spatial distribution of the velocity profile indicates that different mixtures behave differently at a particular vibration conditions. The phenomena like sieving or percolation are also observed based on the analysis of top view simulation snap shots.

Whole-Body Vibration in Horizontal Direction for Stroke Rehabilitation: A Randomized Controlled Trial.

BackgroundAs most of the existing whole-body vibration (WBV) training programs provide vertical or rotatory vibration, studies on the effects of horizontal vibration have rarely been reported. The present study was conducted to investigate the effect of WBV in the horizontal direction on balance and gait ability in chronic stroke survivors.Material/MethodsThis study was designed as a randomized controlled trial. Twenty-one stroke survivors were randomly allocated into 2 groups (whole-body vibration group [n=9] and control group [n=12]). In the WBV group, WBV training in the horizontal direction was conducted for 6 weeks, and a conventional rehabilitation for 30 min, 3 days per week for a 6-week period, was conducted in both the WBV and control groups. Outcome variables included the static balance and gait ability measured before training and after 6 weeks.ResultsOn comparing the outcome variables before and after training in the WBV group, significant differences were observed in the cadence and single support time of gait ability. However, there were no significant differences in other variables, including velocity, step length, stride length, and double support time. In addition, after training, no significant differences in all variables were observed between the 2 groups.ConclusionsThe results of this study suggest that WBV training in the horizontal direction has few positive effects on balance and gait function in chronic stroke survivors. However, further investigation is needed to confirm this.

Experimental investigation on partially filled liquid pools under combined thermal and vibrational loads

The seismic excitation affects the performance of a heat exchanger submerged in a water pool. Hence, the potential effect of external vibrations on a boiling and heat transfer system is investigated in this work. The effect of horizontal vibration on heat transfer performance of a submerged heater rod has been experimentally investigated under atmospheric pressure conditions. The experimental results show that the heat transfer is enhanced by 15% with vibration in single-phase convection. Heat transfer in subcooled boiling is significantly affected by higher mode excitation frequencies. However, there is no significant influence of excitation frequency on heat transfer in the saturated boiling regime. The effect of circumferential wall temperature around the heater is investigated and a maximum temperature difference of 6.3% has been found between the top and bottom heater surface. Thermal stratification of pool water is also studied without and with external vibration. The vertical temperature difference between zone 1 and zone 2, (i.e. thermal stratification) is suppressed by 80% at excitation frequency of 6.35 Hz.

THE INFLUENCE OF THE HORIZONTAL LOAD VIBRATIONS OF THE CRANE-PIPE LAYING MACHINE GIBBET ON THE LOAD MOMENT STABILITY

Introduction : the main feature of operation of cranes-pipe layers is work in difficult ground conditions, which significantly affects the operating mode of the machine. This factor is one of the main reason leading to the rocking of the load on the crane-pipe laying machine gibbet and as a consequence it leads to emergency and contingency situations. In the research the forced vibration of the load on the crane-pipe layer gibbet and the causes of their occurrence and the problems to which they lead are observed. Engineering solutions of predecessors are considered. A new approach to the solution of these problems is proved. Materials and methods : the design scheme of the crane-pipe laying machine is justified, assumptions are accepted, coordinate systems are introduced, and a mathematical model of the crane-pipe-laying machine is compiled. Results : the following time dependences are constructed: the deflection of the cargo in the transverse plane of the crane-pipe layer (horizontalvibrations), the deflection of the cargo in the longitudinal plane of the pipe laying crane, the roll of the base machine, the change in the load moment are also constructed. The influence of the horizontal vibrations of the load on the change in the load moment and the occurrence of vertical vibrations is determined. Discussion and conclusion : the effect of horizontal vibrations on the change of the load moment is evaluated and as a consequence of the negative effect on the stability of the crane-pipe laying machine is presented.

Effect of horizontal vibration on pile of cylinder avalanches as a pseudo-two dimensional granular system

Dynamics of pseudo-two dimensional granular material consisted of two layers cylinder piles positioned on top of a horizontally vibrated plate is reported in this work. It is aimed to observe structural change of the cylinder pile vibrated in certain frequency and amplitude. Dimensionless acceleration Γ= 4π2f2A/g (with g is gravitational acceleration), which is generally used in granular materials to observe transition between states, e.g. stable, rotating without slipping, rolling and slipping in Γ-f plane, does not work well for this system. For this system additional states for the piles can also be observed, e.g. stable and flowing states. Observations parameters are frequency f (measured in Hz) and amplitude A (measured in cm). These parameters are used to construct the A-f plane instead of Γ-f one.

Fluidization behavior of glass beads under different vibration modules

The expansion of free bubbling gas fluidized beds has been investigated experimentally in a two-dimensional perspex-walled bed. Glass beads were fluidized with dried air at varying gas velocities, while the bed was vibrated at different frequencies, amplitudes and directions to study their effects on the fluidization quality. The experimental results showed that the particle flow pattern depends on the vibration direction, especially at superficial gas velocities less than the minimum fluidization velocity U mf. The effect of horizontal vibration on fluidization behavior of glass beads exists at superficial gas velocities less than U mf, while the effect of vertical vibration on fluidization behavior still exists even at higher superficial gas velocities than U mf.

Effects of horizontal vibration on hopper flows of granular materials

The current experiments investigate the discharge of glass spheres in a planar wedge-shaped hopper (45° sidewalls) that is vibrated horizontally. When the hopper is discharged without vibration, the discharge occurs as a funnel flow, with the material exiting the central region of the hopper and stagnant material along the sides. With horizontal vibration, the discharge rate increases with the velocity of vibration as compared with the discharge rate without vibration. For a certain range of acceleration parameters (20–35 Hz and accelerations greater than about 1 g), the discharge of the material occurs in an inverted-funnel pattern, with the material along the sides exiting first, followed by the material in the core; the free surface shows a peak at the center of the hopper with the free surface particles avalanching from the center toward the sides. During the deceleration phase of a vibration cycle, particles all along the trailing or low-pressure wall separate from the surface and fall under gravity for a short period before reconnecting the hopper. For lower frequencies (5 and 10 Hz), the free surface remains horizontal and the material appears to discharge uniformly from the hopper.