$13.$ Three$-$phase flows require advanced models to account for the interactions between gas, $\_\_\_\_\_\_\_\_,$ and $\_\_\_\_\_\_\_\_$ phases.

$14.$ Fluidized beds operate effectively when particles are suspended by an upward$-$flowing $\_\_\_\_\_\_\_,$ reaching a state of $\_\_\_\_\_\_\_$ fluidization.

$15.$ The pressure drop in packed beds is significantly influenced by the fluid flow rates and the properties of the packed $\_\_\_\_\_\_\_.$

$16.$ The $\_\_\_\_\_\_\_$ of solid particles in gas$-$solid liquid flows complicates the accurate identification of flow $\_\_\_\_\_\_\_.$