Birds of prey hover effortlessly while buffeted by wind but how they do it can teach us how to build better aircraft.
Nerve-rattling turbulence could be a thing of the past, thanks to new research. Based on the ingenuity of feathers and the way birds use them to detect disturbances in airflow, RMIT researchers hope to make flights smoother.
Flight systems that mimic how feathers help birds adjust to differences in airflow have been studied by RMIT’s Unmanned Aircraft Systems research team, in an effort to minimise flight turbulence.
The team has based its studies on the concept of phase-advanced sensing, in which airflow disturbance is sensed before it results in aircraft movement. This is achieved by early detection of the pressures from gust effects on leading parts of plane wings or by measuring the gusts ahead of the wing.
Researchers, led by Professor Simon Watkins, have lodged a provisional patent on this innovative turbulence mitigation system.
Encouragingly, tests on a micro plane showed the system significantly reduced the effects of turbulence. These successful tests have led researchers to be optimistic that similar strategies could be used for larger planes.
“We are pretty sure it will work on larger planes since turbulence is most challenging for the smaller ones – and we have demonstrated that we can make it work for lightweight micro planes,” Watkins says.
“The patented methods of minimising turbulence on aircraft can be used for small and large planes, minimising the motions associated when flying at low altitude – especially take-off and landing for passenger craft.”
Watkins says reducing turbulence has the potential to change the future of the aviation industry significantly.
“It could lead to smoother flying experiences and perhaps even reduced ticket prices since the concept may result in less stress on wings.
“Material fatigue is dependent on dynamic loading and if you can safely extend life, planes can fly for longer before they get retired, potentially reducing airline costs.”
Solving the problem of turbulence and how it is managed by moving objects has long intrigued Watkins.
“I have been thinking about the problem and possible solutions for several decades, as I have been flying small radio-controlled models since my teenage days.
“Even then I used to wonder how I could stop them getting perturbed by wind gusts.
“My very small gliders used to roll around a lot when I was flying them from windy slopes and I found my somewhat delayed reactions, when added to the time delays in the control system, meant that corrections were happening too late.
“Too large and too late – a classic over-control issue.”
The same advanced strategies used to stabilise turbulence in aircraft could also be used in cars. Watkins says minimising wind noise in cars would improve passenger comfort.
“A hot topic for passenger cars is wind noise and how it becomes more annoying to humans when it fluctuates.
“Some of my research conducted in this area was done in Germany at Stuttgart University where we instrumented Mercedes Benz cars by fitting our probes through a hole which we drilled in the car roof.
“We showed the link between the turbulence and sound fluctuations inside the car. Interestingly, a modulation frequency of four hertz (cycles a second) is typical when driving through atmospheric turbulence, and humans find this distracting since it is about the frequency of syllables in speech unless you talk really slowly.”
PhD student Abdulghani Mohamed, supervised by Watkins and Dr Reece Clothier in RMIT’s School of Aerospace, Mechanical and Manufacturing Engineering, has contributed to the success of this pioneering research.
Findings from their research have been published in the prestigious aerospace journal, Progress in Aerospace Sciences.
Story: Kate Jones
This story was first published in RMIT's Making Connections magazine.