What are Navier-Stokes Equations?
One of the most important ways in which a fluid differs from a rigid solid body is that its motion is almost always associated with a drastic deformation of its own shape and size and under some conditions, also its overall volume. The rigid body dynamics taught at the high school level is insufficient to describe the motion of fluid. Nevertheless, the foundation that one can turn to is the Newtons Second Law. When the force balance is applied on fluid elements using different approaches, one arrives at the equation that mathematicians in Western Europe namely, Claude-Louis Marie Henri Navier and later George Gabriel Stokes (though there were more than just these two working on the equations) derived in the 19th century that describes the motion of fluid under the action of any applied external field (pressure, body forces, temperature, etc.). Since a fluid can deform in all the four coordinates of the time-space continuum, the force balance when mathematically formulated would show-up
