ABSTRACT
If the relative velocity is sufficiently low, the fluid streamlines can follow the contour of the body almost completely all the way around without incurring any loss of momentum. As the fluid flows over the forward part of the sphere, the velocity increases because the available flow area decreases, and the pressure must decrease in order to satisfy the conservation of energy. Conversely, as the fluid flows around the back side of the body, the velocity decreases due to the expanding flow area, and the pressure increases. The boundary layer is the region of the fluid near a solid boundary in which viscous forces dominate and the velocity varies with the distance, from zero at the wall to a maximum value at the edge of the boundary layer. Many engineering operations involve the separation of solid particles from fluids, in which the motion of the particles is the result of a gravitational force.
