While EADS develops Blue Edge NASA goes for Blue Thunder
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From: US
While EADS develops Blue Edge NASA goes for Blue Thunder
Not the be left behind by European advances in blade noise reduction research NASA, finally, embarks on a campaign to make 'whisper mode' a reality!
NASA Pursues ‘Whisper Mode’ In World’s Biggest Wind Tunnel | Autopia | Wired.com
NASA Pursues ‘Whisper Mode’ In World’s Biggest Wind Tunnel
By Jason Paur
As more and more helicopters are used for everything from medical transportation to news gathering, more and more people on the ground are complaining about the noise. NASA recently spent several months researching new design ideas to make helicopters quieter and more efficient. The work could not only make things quieter on the ground, but could lead to faster helicopters that are able to carry a bigger payload.
“NASA hopes to make those new designs quieter, faster, more fuel efficient, and capable of carrying more people and cargo,” said Tom Norman, the researcher for the project test team.
The research was performed at the world’s largest wind tunnel located at the Ames Research Center in Moffett Field, California. There researchers used a rotor from a Sikorsky UH-60 Blackhawk helicopter mounted on a fuselage used only for the research. The goal was to study the interaction between the rotor blades and the air.
Pilots often like to joke that helicopters don’t fly, they simply beat the air into submission. But the truth is most of the noise and vibration is due to the main and tail rotor blades interaction with the air. The NASA researchers used a technique known as particle image velocimetry to study the airflow over the rotor blades. The technique uses laser light to measure the airflow without having to touch, and therefore interfere with the rotor blades. NASA says the research conducted with the massive Blackhawk rotor blades was the largest ever using this technique.
High speed cameras were also used to watch and measure how the blades flex and bend during flight. A helicopters main rotor blades are constantly twisting and turning during flight. A blade moving forward relative to the direction of flight has very different loads compared to the retreating blade. The high speed cameras along with sensors were used to measure the rotor lift.
Helicopter noise is a major factor affecting operations around the world. Helicopter makers including Eurocopter, Bell and Sikorsky are investing in quiet technologies that will allow expanded helicopter use in both combat and civilian markets.
By Jason Paur
As more and more helicopters are used for everything from medical transportation to news gathering, more and more people on the ground are complaining about the noise. NASA recently spent several months researching new design ideas to make helicopters quieter and more efficient. The work could not only make things quieter on the ground, but could lead to faster helicopters that are able to carry a bigger payload.
“NASA hopes to make those new designs quieter, faster, more fuel efficient, and capable of carrying more people and cargo,” said Tom Norman, the researcher for the project test team.
The research was performed at the world’s largest wind tunnel located at the Ames Research Center in Moffett Field, California. There researchers used a rotor from a Sikorsky UH-60 Blackhawk helicopter mounted on a fuselage used only for the research. The goal was to study the interaction between the rotor blades and the air.
Pilots often like to joke that helicopters don’t fly, they simply beat the air into submission. But the truth is most of the noise and vibration is due to the main and tail rotor blades interaction with the air. The NASA researchers used a technique known as particle image velocimetry to study the airflow over the rotor blades. The technique uses laser light to measure the airflow without having to touch, and therefore interfere with the rotor blades. NASA says the research conducted with the massive Blackhawk rotor blades was the largest ever using this technique.
High speed cameras were also used to watch and measure how the blades flex and bend during flight. A helicopters main rotor blades are constantly twisting and turning during flight. A blade moving forward relative to the direction of flight has very different loads compared to the retreating blade. The high speed cameras along with sensors were used to measure the rotor lift.
Helicopter noise is a major factor affecting operations around the world. Helicopter makers including Eurocopter, Bell and Sikorsky are investing in quiet technologies that will allow expanded helicopter use in both combat and civilian markets.
Joined: Jan 2001
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From: North Queensland, Australia
I wonder how they make it simulate free flight properly - if they're driving the rotors at something like normal rpm and pitch settings, they'd create a bunch of downwash which would then interact with the tunnel walls and floor in weird ways, wouldn't it?
Joined: Dec 2007
Posts: 411
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From: Ireland
The recent developments in "Quiet Rotor" technology are quite interesting. It is a little puzzling that it has taken this long for the manufacturers to tackle the issue of achieving lower noise emissions from rotorcraft, though.
I have been researching the history of the various prototypes and test ships of the H-6/Model 500 series of helicopters and just selecting that helicopter as a single example, quite a lot of research and testing has been carried out in the past in relation to "Quiet Rotor" technology and, indeed, other systems that can contribute to quieter helicopters. NASA and Hughes carried out testing on a H-6 in the late sixties and early seventies and achieved quite large noise reductions with their "Quiet One" prototype. Air intakes, MGB transmission and engine shrouded in sound-absorbent material, a tuned engine exhaust, shaped rotor tips, an increase in blade numbers (main and tail) and reduced rotor RPM all made the "Quiet One" exceptionally quiet, apparently.
Another system tested by Hughes and NASA was their "Higher Harmonic Control" system, which was primarily seeking to reduce vibrations emanating from the main rotor system. It was successful in reducing vibration but it was also possible to "tune" the noise coming from the main rotor. This system was tested in the period 1982 to 1985 using computers of the day. Given the power of today's computers, the HHC system could be worth exploring again for the various benefits it has to offer.
Eurocopter seem to have had some success with the "Staggered-Blade" design fenestron tail rotor as regards noise emissions. Perhaps if a similar fan was fitted to the NOTAR anti-torque system, it might lower noise levels even further.
Combine all three of these systems in one helicopter and the noise reductions could be notable. Perhaps the cost of R&D in this area has been prohibitive up to now but given the demand for eco-friendly transport these days, the next generation of helicopters could be very interesting indeed.
500 Fan.
I have been researching the history of the various prototypes and test ships of the H-6/Model 500 series of helicopters and just selecting that helicopter as a single example, quite a lot of research and testing has been carried out in the past in relation to "Quiet Rotor" technology and, indeed, other systems that can contribute to quieter helicopters. NASA and Hughes carried out testing on a H-6 in the late sixties and early seventies and achieved quite large noise reductions with their "Quiet One" prototype. Air intakes, MGB transmission and engine shrouded in sound-absorbent material, a tuned engine exhaust, shaped rotor tips, an increase in blade numbers (main and tail) and reduced rotor RPM all made the "Quiet One" exceptionally quiet, apparently.
Another system tested by Hughes and NASA was their "Higher Harmonic Control" system, which was primarily seeking to reduce vibrations emanating from the main rotor system. It was successful in reducing vibration but it was also possible to "tune" the noise coming from the main rotor. This system was tested in the period 1982 to 1985 using computers of the day. Given the power of today's computers, the HHC system could be worth exploring again for the various benefits it has to offer.
Eurocopter seem to have had some success with the "Staggered-Blade" design fenestron tail rotor as regards noise emissions. Perhaps if a similar fan was fitted to the NOTAR anti-torque system, it might lower noise levels even further.
Combine all three of these systems in one helicopter and the noise reductions could be notable. Perhaps the cost of R&D in this area has been prohibitive up to now but given the demand for eco-friendly transport these days, the next generation of helicopters could be very interesting indeed.
500 Fan.
Last edited by 500 Fan; 13th June 2010 at 18:11.
Joined: Nov 2004
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From: Cambridgeshire, UK
Originally Posted by Yellow & Blue Baron
Graviman and riff raff to the rescue !!!
In a fixed wing the reason you feel a buffet during stall is because the seperated airflow passes through the elevator (a canard stalls its front elevator first so i imagine you still get a buffet). A helicopter shedding vortices at its rotor blade tips is sure to suffer blade vortex interaction (BVI) between tail rotor and main rotor. So the solution is to design a rotor system that achieves its downwash distribution without shedding tip vortices. Queue the ring-rotor....
Maybe Bug will take the opportunity to parade his innovation.
From thread:
All i need now is the balls to try it
