The main transport mechanisms of proppant particles are settlement and fluidization, which cause a three-layer flow pattern (stationary proppant bed, fluidization layer and clean fluid layer) to form.
Due to relatively larger size as compared to nanosize particles, one may expect settlement of microsize particles.
Despite being the most used worldwide, railway ballasted tracks presents high maintenance cost related to ballast settlement and particle degradation.
Ballasted railway tracks, despite their benefits, present some limitations and drawbacks, mainly associated with geometry degradation due to ballast settlement and particle breakage.
However, the degradation of the ballast particles and the layer settlement lead to important maintenance costs.
Several approaches have been reported in the literature for placement of the nanomaterials between the electrodes, but most of them do not offer selective settlement of particles or need expensive apparatus and high vacuum [20].
The solid particles are exposed to centrifugal acceleration and therefore, the settlement rate of particles will be varied in accordance to their various sizes, densities, and shapes.
In addition, packing density of tissue ultrastructures (for example, fiber density) may also be responsible, because an excessive looseness of the structure may not allow secure settlement of silver particles.
Their settlement rate depends upon: particle size, salinity of the water, temperature, the mineralogy, the organic content, and the presence and activity of biological factors such as bacteria and phytoplankton.
Based on single particle model, the rate of barite settlement and fluid pressure reduction have been modeled.
