text: Consider an infinitely large plate started impulsively with a step change in velocity—from 0 to u—in the direction of the plate–fluid interface plane.
  The equation of motion for the fluid—Stokes flow at low Reynolds number—is
  where u(y,t) is the velocity of the fluid, at some time t, parallel to the plate, at a distance y from the plate, and v is the kinematic viscosity of the fluid (c~continuous phase).
  The solution to this equation is,
  where erf and erfc denote the error function and the complementary error function, respectively.
  Assuming that an acceleration of the plate can be broken up into a series of such step changes in the velocity, it can be shown that the cumulative effect on the shear stress on the plate is
  where u(t) is the velocity of the plate, ρ is the mass density of the fluid, and μ is the viscosity of the fluid.