[tstorm]

Hi all,
I've read that the Boussinesq assumption linearized the relationship between the turbulent stresses and the mean strain rate, so:
u_i*u_j=2/3*k*del_ij - 2*nu_t*S_ij

I've also seen people say that the Boussinesq assumption makes the normal stresses isotropic, so:
uu=vv=ww=2/3*k

My question is where does the second term go? Does the Boussinesq assumption also assume that du/dx = dv/dy = dw/dz = 0?

Thanks!