In this paper, we introduce a new class of functions satisfying spacial absolutely continuous (see Definition 3.1), denoted by \documentclass[12pt]{minimal}\begin{document}$L^{2}_{sac}(\mathbb {R};\mathbb {R}^{n})$\end{document}Lsac2(R;Rn), which are translation bounded but not normal (see [S. S. Lu, H. Q. Wu, and C. K. Zhong, “Attractors for non-autonomous 2D Navier-Stokes equations with normal external forces,” Discrete Contin. Dyn. Syst. A 13(3), 701−719 (2005)]10.3934/dcds.2005.13.701 and Definition 3.1) in \documentclass[12pt]{minimal}...