Effects of lower floating-point precision on scale-resolving numerical simulations of turbulence

TL;DR

This study demonstrates that reducing floating-point precision to single precision in turbulence simulations on modern hardware does not significantly affect the accuracy of results, enabling faster computations without compromising fidelity.

Contribution

It provides a comprehensive analysis showing that standard IEEE single precision can be effectively used in high-fidelity turbulence simulations across multiple CFD solvers and flow cases.

Findings

Single precision yields results comparable to double precision in turbulence simulations.

Flow physics are robust against lower floating-point precision.

Potential pitfalls of reduced precision are discussed.

Abstract

Modern computing clusters offer specialized hardware for reduced-precision arithmetic that can speed up the time to solution significantly. This is possible due to a decrease in data movement, as well as the ability to perform arithmetic operations at a faster rate. However, for high-fidelity simulations of turbulence, such as direct and large-eddy simulation, the impact of reduced precision on the computed solution and the resulting uncertainty across flow solvers and different flow cases have not been explored in detail and limits the optimal utilization of new high-performance computing systems. In this work, the effect of reduced precision is studied using four diverse computational fluid dynamics (CFD) solvers (two incompressible, Neko and Simson, and two compressible, PadeLibs and SSDC) using four test cases: turbulent channel flow at Retau = 550 and higher, forced transition in a channel, flow over a cylinder at ReD = 3900, and compressible flow over a wing section at Rec = 50000. We observe that the flow physics are remarkably robust with respect to reduction in lower floating-point precision, and that often other forms of uncertainty, due to for example time averaging, often have a much larger impact on the computed result. Our results indicate that different terms in the Navier-Stokes equations can be computed to a lower floating-point accuracy without affecting the results. In particular, standard IEEE single precision can be used effectively for the entirety of the simulation, showing no significant discrepancies from double-precision results across the solvers and cases considered. Potential pitfalls are also discussed.