Making gusts to smooth out the bumps

How can a gust generator help to improve the safety of flights and mitigate climate change? Researchers experimenting with the one at the Open Jet Facility (OJF) to recreate turbulence explained how their work will contribute to achieving this goal.

A better understanding of turbulence is essential because it’s happening more owing to climate change and impacting aircraft operation. Air travel is becoming bumpier. Every week turbulence causes discomfort and injuries to people on flights, typically with flight attendants as the unfortunate victims getting thrown around the cabin.

At the same time, advances in materials make for lighter, more flexible airframes, wings and rotors that are more sensitive to turbulence. So designers need tools to predict the dynamic loads to optimise their design. Apart from smoothing out the ride, an added benefit of lighter aircraft will be more fuel efficiency and less carbon emissions, coming full circle to mitigate climate change.

PhD researcher Paul Lancelot and Dr. Jurij Sodja, working in assistant professor Dr. Roeland De Breuker’s Smart Structures and Aeroelasticity Group of the Faculty of Aerospace Engineering (LR), are creating turbulence in the wind tunnel at the scale of jet streams and in proximity to mountains and other aircraft.

“There’s not much data from dynamic tests in the literature,” said Lancelot, “and in Delft we have the required infrastructure to use the wind tunnel to fill the gap.” Current computational fluid dynamics can numerically simulate complex airflow disturbances similar to what aircraft and wind turbines encounter but with less confidence.

“We also want to model and test the interaction of the air with the structure of the wings, which is even more complex,” said Sodja.

The gust generator deflects the wind tunnel’s steady air flow by flapping two controllable vertical vanes mounted on a 200kg aluminium frame in front of it. After a first experiment to check that the equipment worked, they confirmed the strength of the gusts, their uniformity and whether generating them was repeatable. Now they are investigating the unsteady aerodynamic response of a rigid wing, measuring 300 configurations exposed to 50 repeated gusts. The challenge is then to correlate the 15,000 gust data points to its aeroelastic response and assess how loads can be alleviated.

In June 2017 they want to obtain data on a flexible wing, followed by a wing with control surfaces in 2018. They hope other research groups will use the gust generator to put their wind turbines, micro drones and other designs through their paces in turbulence.

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