Continuous Eddy Simulation (CES): Conceptual approach and applications

TL;DR

This paper introduces Continuous Eddy Simulation (CES), a new turbulence modeling approach that adaptively adjusts to flow resolution, enabling reliable high Reynolds number flow simulations at significantly reduced computational costs.

Contribution

CES provides a mathematically rigorous, adaptive turbulence model that seamlessly transitions between RANS and LES regimes, outperforming hybrid methods in accuracy and efficiency.

Findings

CES accurately simulates high Re flows like periodic hill and hump flows.

CES reduces computational costs by orders of magnitude compared to traditional hybrid methods.

CES demonstrates reliable predictions across complex turbulent flow applications.

Abstract

The simulation of high Reynolds number (Re) separated turbulent flows faces significant problems for decades: large eddy simulation (LES) is computationally too expensive, and Reynolds-averaged Navier-Stokes (RANS) methods and hybrid RANS-LES methods often provide unreliable results. This has serious consequences, we are currently unable to reliably predict very high Re regimes, which hampers applications and our understanding of turbulence structures. The paper reports the advantages of a strict mathematical approach, continuous eddy simulation (CES), to derive partially resolving turbulence models. In contrast to popular hybrid RANS-LES, this minimal error approach includes a dynamic modification of the turbulence model in response to the actual flow resolution: the model can increase (decrease) its contribution to the simulation in dependence of a low (high) flow resolution. This property is the essential requirement to seamlessly cover RANS and LES regimes. The CES modeling approach offers essential advantages regarding its functionality: basically, it is independent of a variety of simulation settings applied in popular hybrid RANS-LES to improve the model performance. In addition, the CES computational cost can be below the cost of other hybrid RANS-LES and LES by orders of magnitude. Essential simulation performance advantages of CES simulations are described here with respect to three complex flow applications: periodic hill flows at high Reynolds number, the NASA wall-mounted hump flow, and the Bachalo & Johnson axisymmetric transonic bump flow.