Microscopic analysis of saltation of particles on an obliquely oscillating plate

Abstract

a b s t r a c tThis paper presents a microscopic analysis of the saltation of particles on an obliquely oscillating plate driven by sine waves with an amplitude on the order of tens of micrometers and a frequency on the order of hundreds of hertz. To examine the effect of the diameter of a particle on its motion, the trajectories and velocities of different-sized particles, from 0.5 to 500 lm in mass median diameter, are analyzed using images captured by a high-speed microscope camera. The results show that larger particles bounce higher, whereas smaller particles easily agglomerate and bounce only slightly, owing to the low restitution caused by their loosely packed structure. In addition, larger particles bounce forward and backward repeatedly, while the agglomerated particles always bounce forward, and consequently have the highest transport velocity among these particles. The particle motion and the transport velocity can be explained by a theoretical probability model.

Numerical and theoretical study of particle saltation on an obliquely oscillating plate

“…2 shows the cumulative distributions of bounce heights obtained from 200 simulated datasets. The plots indicate previous experimental data for D p50 = 500 μm, 50 μm and 0.5 μm (Dag50 = 150 μm) [33], and lines indicate the simulation results for particle A, B, and C. The height distributions of particle A, B, and C had ranges of 0 -8 mm, 0 -2 mm, and 0 -0.3 mm, respectively. The range of particle B was lower than that of particle A because of kinetic energy dissipation as a result of fluid resistance during flight.…”

“…(1)−(6), (11) and (12). The simulation conditions match the experimental conditions in the previous study [33], i.e., Ax = Ay = 35 μm and f = 280 Hz for the oscillating substrate, and the parameters of particles are listed in Table 1.…”

“…The bounce heights and distances distributions obtained from the simulation were compared with experimental results [33]. Fig.…”

“…However, if the vertical incident velocity is less than the downward velocity of the moving plate, a collision cannot occur. Thus, a lower incident velocity increases the probability of particle collision when the plate is moving upward [23][24][25]28,33]. To quantitatively analyze the effect of the fluid resistance on the motion for each particle, the ratio of the fluid resistance to the gravity was calculated from the median velocity in Fig.…”

“…We previously studied the saltation of different-sized particles, from 0.5 to 500 μm in diameter, on an obliquely oscillating plate by analyzing images captured by a high-speed microscope camera to examine the effect of the diameter of a particle on its motion [33]. The experimental results showed that the particles with Dp50 = 500 μm and 50 μm saltated individually on the plate, while particles with Dp50 = 0.5 μm formed agglomerated particles with Dag50 = 150 μm and the agglomerated particles bounced only slightly.…”