Why is turbulence so difficult? After all, we have the Navier-Stokes Equations:   (From [1])   Even for incompressible subsonic flow at reasonable temperatures and pressures, the problem of turbulence remains intractable. Why? "It is that we cannot solve these equations in any meaningful sense for physically relevant initial conditions..." Even global existence of solutions (in 3-D) has not been given. [2] The Navier-Stokes Equations for incompressible flow: