Here’s the standard formula for the Navier–Stokes equation for a Newtonian fluid:
$$
\rho \left( \frac{\partial \mathbf{u}}{\partial t} + (\mathbf{u} \cdot \nabla)\mathbf{u} \right) = -\nabla p + \mu \nabla^2 \mathbf{u} + \rho \mathbf{g}
$$
– ρ: fluid density
– u: velocity
– p: pressure
– μ: viscosity
-g: external forces (like gravity)
This formula basically says: change in momentum = pressure forces + viscous forces + external forces. 🚀
However different experiments has been carried out and different attempts made but the Navier Stokes Equation is still one unsolved mystery.