Removal of particles from fouling layers due to an incident particle impact is affected bythe fluid fluctuations in industrial applications if the contact time is larger than the fluctuationstime scales. The contact time is an important parameter when analysing the influence of the fluidstructure interaction on a fouling process. The contact time for a particle hitting a bed of particlesis defined as the time it takes for the incident particle to bounce off the bed. The contact time fora particle hitting a bed of particles arranged in a rectangular and a hexagonal array is measuredexperimentally and calculated numerically based on the discrete element method. The incidentparticle and the bed particles are of the same size and material. It is found that the contact time isproportional to the number of bed layers in case of a rectangular bed array and independent of thenumber of bed layers in case of a hexagonal bed of particles. The contact time is inverselyproportional to the impact speed. The rebound speed of the incident particle is independent of thenumber of bed layers in case of a hexagonal arrangement of particles and is exponentiallydependent on the number of bed layers in case of a rectangular arrangement. A hexagonal bed ofparticles acts as a massive particle due to its large co-ordination number compared to arectangular bed of particles. The force propagation speed in granular matter could be calculatedby plotting the path of the force as a function of the contact time and finding the gradient of thisgraph.
Abd-Elhady, M. S., Rindt, C. C. M., & Steenhoven, van, A. A. (2009). Contact time of an incident particle hitting a 2D bed of particles. Powder Technology, 191(3), 315-326. https://doi.org/10.1016/j.powtec.2008.10.024