closure_enstrophy_decay_of_exists_energy_inequality is
exists_closure_gronwall_bound_of_exists_energy_inequality for the cutoff enstrophy
cutoffEnstrophy χ u and its dissipation cutoffEnstrophyDissipation χ u: it composes the
substitution step deriv_le_of_closure_energy of eq:aniso:closure:energy with the Grönwall step
closure_gronwall_bound of lem:aniso:closure, so that the energy inequality in the form
∃ Cstar ≥ 1, … together with the G, W decay data gives the enstrophy decay
Y + 1 ≤ C' (−t)^{−C_*η}. closure_enstrophy_decay_sixteenth_eta_of_exists_energy_inequality is
the specialization to the manuscript's choice η = 1/(16 C_*), for which the decay exponent is
the universal constant 1/16 (exists_closure_gronwall_bound_sixteenth_eta), and
closure_enstrophy_decay_of_mixed_term_bound obtains the energy inequality from
CIV.energy_inequality_of_mixed_term_bound.