“…In particular, Neustupa-Penel [8] first formulated sufficient conditions for regularity of a so called suitable weak solution (u, p) in a sub-domain D of the time-space cylinder Q T = (Ω × (0, T )) by means of requirements on one of the eigenvalues of strain tensor. Later, for the generalized impermeability boundary conditions and the Navier-Slip boundary condition, in [9,10], they showed that the similar condition holds, then the solution u is regular on [0, T]. As explained in [8], such deformations, when the "infinitely small" volumes of the fluid are compressed in two dimensions and stretched in one dimension support regularity, while the cases when the "infinitely small" volumes of the fluid are compressed in one dimension and stretched in two dimensions support the hypothetical blow up.…”