“…The existence, long-time behavior and regularity of solutions to the 3D Navier-Stokes-Voigt equations without delays in bounded domains or unbounded domains satisfying the Poincaré inequality have attracted the attention of many mathematicians [2,3,6,15,16,20,21,30,31,32]. There are many results involving PDEs in fluid mechanics with delay (see e.g., [1,8,9,10,11,12,13,27,28,29]).…”