Particle motion modeling of oblate spheroids in complex flow geometries

The orientation of kaolin pigments is expected to influence the flow behavi or during coating and the final behavior during coating and the final prope rties of the coating layer. The work provides a new computation tool to pre dict the trajectories and orientation of oblate spheroids in any coating ge ometry. The motion of oblate spheroids in a coating geometry is simulated using a S tokesian dynamics technique.. Computation fluid dynamics is used to calcula te velocity fields that are used to estimate the long-range hydrodynamic fo rces and torques on the particles. The model calculates the trajectories, r otation, forces, and torques on the particles, including particle-particle hydrodynamic and colloidal forces. Process variables, such as coat weight a nd particle aspect ratio, are studied. In general, the particles are predic ted to be aligned with the web, but the blade coater produces more orientat ion than the metering size press for particle aspect ratios less that 10. P articles with a low aspect ratio are found to have a low orientation. Parti cles are forced together in the metering zone, which may lead to processing issues.