Simulation approach could solve major challenge for flying taxi deployment

Noise is a major challenge to the deployment of novel new aircraft such as flying taxis, with urban populations unlikely to embrace hundreds of whirring vehicles overhead.

A new simulation approach could help solve that challenge, by quickly and accurately computing the noise characteristics of complex aerofoil designs under extreme operating conditions. By shortening simulation timeframes from months to hours, the approach – developed by researchers at King Abdullah University of Science & Technology in Saudi Arabia – could accelerate the design and deployment of quieter aerofoils for next-generation aircraft.

“Aircraft noise is already a problem for many communities located near major airports, and this will only get worse with the expanded use of drones and, in the future, air taxis and private airborne vehicles,” said researcher Radouan Boukharfane.

Aerofoils – wings, propellers and turbine blades – are typically designed and refined using relatively fast applied mathematical techniques. Characteristics like noise generation are more complex, however. These typically require tests using experimental models, because the direct numerical simulations capable of resolving such features are so computationally intensive. Even on today's fastest computers they can take months to complete.

“In realistic engineering problems in aeroacoustics, the interactions between the turbulent airflow and the surface are important,” said Boukharfane. “One of our main challenges was how to model compressible airflows across the surface, under high turbulence, with sufficient accuracy to predict the separation of the airflow over a smoothly curved surface and its reattachment near the trailing edge.”

Rather than directly simulate the entire flow field at high resolution, Boukharfane, with colleagues Matteo Parsani and Julien Bodart, applied a wall-modelled large-eddy simulation (WMLES) to model the near-surface flows at high resolution, while reducing overall computational intensity by modelling only larger flow structures further from the aerofoil.

“The WMLES approach used in this work allows us to reproduce many of the key qualitative features of the airflow seen in experiments, as well as noise-related characteristics such as the wall pressure spectra. Importantly, we have also shown that the method is valid for high speed and highly turbulent flow,” said Boukharfane.

The algorithm described in the paper is the latest in a suite of tools developed by the Advanced Algorithms and Numerical Simulations Laboratory, and builds on a collaboration with the Higher Institute of Aeronautics and Space in France under the Clean Sky Joint Undertaking of the European Union. Some of the tools are being used and tested by NASA, Airbus and the National Institute of Aerospace in Virginia.

“Our team is uniquely placed at the intersection of numerical analysis, physics, and high-performance computing to develop novel and efficient algorithms that better account for physical phenomena and efficiently utilise modern computing architectures,” said Parsani.

The research was published in Scientific Reports.

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