Shape and Size of Fluid Particles

The shape and size of a fluid particle (a bubble or a drop) significantly affects its motion as well as the associated heat and mass transfer processes. The drag force depends on the particle shape and it is one of the factors that determines the magnitude of the fluid velocity. The transport depends strongly on the interfacial area which is a function of the size and shape of the particle, as well as the overall fluid motion. At the interface between a particle and the ambient fluid, for particle stability, a balance between the normal force, the shear force, gravity, and the surface tension force must be maintained. This balance governs the shape of the particle. The size would also be influenced, particularly if there is phase change.