An energy-based lengthscale for reduced order models of turbulent flows

In this paper, we propose a novel reduced order model (ROM) lengthscale that is constructed by using energy distribution arguments. The new energy-based ROM fundamentally different from the current lengthscales, which are built dimensional To assess novel, lengthscale, compare it with standard, dimensionality-based in two types of models: (i) mixing-length (ML-ROM), closure model; and (ii) evolve-filter-relax (EFR-ROM), regularized ROM. We test four combinations (i.e., ML-ROM EFR-ROM equipped lengthscales) numerical simulation turbulent channel flow at Reτ=395. investigation yields following conclusions: significantly (almost orders magnitude) larger than standard lengthscale. As result, more stable ML-ROMs EFR-ROMs displays correct asymptotic behavior respect to dimension, whereas does not. intrinsically adaptive important realistic settings where full data determine an optimal may not be possible. (iii) (when significant filtering effected) whose parameters less sensitive robust) based on could enable development better scale-aware strategies for flow-specific applications expected have long term nuclear reactor thermal-hydraulics.