Navier Stokes equations
These equations were derived independently by G.G Stokes and M. Navier in the 19th century, and describe the motion of a non-turbulent Newtonian fluid.
In its general form the equation that describes the motion is:
Stokes_equations/latex_a4a578906b40ce205dc69625fb1472a155c41e6f_p1.png "$\rho \left(\frac{\partial \bf{v}}{\partial t} + \bf{v} \cdot \nabla \bf{v} \right) = -\nabla p + \nabla \cdot \bf{T} + \bf{f}$")
where \rho denotes density, p pressure, v is velocity, T is the stress tensor, and f is forces acting on the fluid.