NAVAIR Leverages CFD to Simulate Aircraft Engine Health and Aerodynamics

Sailors assigned to the Nimitz-class aircraft carrier USS George H.W. Bush (CVN 77) test a jet engine cell on the ship’s fantail. CharLES is reducing the time and cost it takes to simulate the aerodynamics inside an aircraft’s engine and troubleshoot problems. (Image: U.S. Navy)

Developed by Naval Air Systems Command's (NAVAIR) Small Business Innovation Research/Small Business Technology Transfer (SBIR/STTR) programs, "CharLES" is described by the Navy as the "aerospace industry’s high-fidelity computational fluid dynamics (CFD) solver," in a May 31 announcement.

CharLES uses large eddy simulation (LES), computer processing units and graphical processing units (GPU) to achieve results with significantly faster turnaround time than standard approaches. NAVAIR claims it is reducing the time and cost it takes to simulate the aerodynamics inside an aircraft’s engine and troubleshoot problems.

CFD is a science that uses computations to analyze the mechanics of fluid flows, the temperature, pressure, velocity and density of air or liquid, around and or through an object. This analysis then yields engineering data that can be used to troubleshoot, modify or test an engine, explained Naval Air Warfare Center Aircraft Division (NAWCAD) Computational Fluid Dynamics and Noise Branch Propulsion and Flow Modeling Science and Technology Lead Dr. Russell Powers.

Current industry-standard CFD predictive tools for propulsion applications rely on steady-state turbulence models that approximate the flow and simulate the engine component-by-component. The result? The transient aerothermal interactions between components within gas turbine engines are poorly approximated during design and off-design operations.

That’s where CharLES comes in.

“There is a strong persistent need in naval aviation for improved CFD tools to support both early trade studies, initial detailed design, system redesign and retrofit efforts related to gas turbine engine development and integration,” Powers said.

Originally developed by Cascade Technologies, a small business now part of Cadence Design Systems, CharLES is designed to tackle fluid dynamics challenges, predicting accurately traditionally complex problems for CFD in aeroacoustics, aerodynamics, combustion, heat transfer and multiphase. CharLES has been optimized to consume as little memory as possible and can be scaled linearly to hundreds of GPUs across dozens of nodes.

Tests of the CharLES showed total simulation time and costs were substantially decreased — engine simulations were completed in a matter of hours and days rather than weeks. Powers credits this achievement to using emerging, high-performance, computing hardware on GPUs.

“This capability to rapidly and reliably simulate multiple designs — and to correctly understand design directional trends at realistic conditions — can and already has supplemented flight test results,” said Computational Fluid Dynamics and Noise Branch Lead Michael Smith.

“It’s a tool that supports early trade studies, initial detailed designs and system redesign/retrofit efforts related to gas turbine engine design and integration in a way that captures the complex turbulence critical to improved engine design/analysis,” Smith added.

The work to improve CharLES and expand its use continues. The Computational Fluid Dynamics and Noise Branch plans to continue licensing the software via a cost-sharing program with DoD High Performance Computing Modernization Program (HPCMP) and is exploring further development at Cadence Design Systems. In addition, NAWCAD is using a DoD HPCMP Frontier project for significant computational allocations to enable transient, full-engine simulations using CharLES. Frontier projects receive additional assistance from the entire HPCMP ecosystem (DSRCs, user support, software development, PET, and networking) throughout their development processes.

The concept behind CharLES is a powerful one with other potential uses.

“The software is expanding the practical application of LES to a broad range of engineering applications beyond aerospace — to include automotive and turbomachinery as well,” Powers said. “I also believe the use of an efficient, accurate, high-fidelity, simulation software in a production environment would prove to be a disruptive, game-changing technology in NAWCAD and across aeronautics.”