Sport Archery » Archery Arrows » Wind tunnels

Wind tunnels

Question:

> Rotation while oscillating is an intriguing problem…. i’m gonna have to think > about a way to do that one….

Its kind of "Prrrrrrr!" with "Boioioioing!" at the same time followed by "Thwack!" if you get it right…. Zolan    😀

Response:

> Rotation while oscillating is an intriguing problem…. i’m gonna have to > think > about a way to do that one…. > Its kind of "Prrrrrrr!" with "Boioioioing!" at the same time followed by > "Thwack!" if you get it right…. > Zolan    😀

kinda like this? http://dialspace.dial.pipex.com/town/pipexdsl/o/aoon40/mighter/index.htm

Response:

– Hide quoted text — Show quoted text -> > Rotation while oscillating is an intriguing problem…. i’m gonna have > to > think > > about a way to do that one…. > Its kind of "Prrrrrrr!" with "Boioioioing!" at the same time followed by > "Thwack!" if you get it right…. > Zolan    😀 > kinda like this? > http://dialspace.dial.pipex.com/town/pipexdsl/o/aoon40/mighter/index.htm

I used to shoot those Jazz arows from Quicks…trouble aren’t they? (I got more pens that way…..) Zolan

Response:

Rotation while oscillating is an intriguing problem…. i’m gonna have to think about a way to do that one…. – Hide quoted text — Show quoted text – > depends how you want to attack this problem. micro-time elapse photography > equipment can give you the frequency (Hz) of oscillation of the arrow. Now, if > you want to see how this oscillation affects the flight and fluid, you can > simulate this this oscillation by supporting the arrow in front, back, and > centroid. The oscillations of an arrow quickly become hyperbolic shaped, and by > moving these supports as a function of time, that will simulate the oscillation. > As for measuring useful things,    (static and dynamic pressure), one would have > to fit the arrow itself with pitot tubes (the ones i use aren’t small enough, > but i believe they are out there for micro-pumps, etc.) that are lined up > perfectly tangent to the flow to be measured, ususally done in cartesian > coordinates. These would have to be then fitted to a pressure transducer, which > wuold be then hooked up to a Data Acquisition Card then to a computer with time > dependent data acquisition software (LabView for instance). So, whether or not i > think it can be done, yes. Do i think its too much of a pain in the arse? quite > possibly when you could simulate an equivalent system on a computer. > Just some thoughts. > Oh, you wouldn’t need a boeing tunnel, just any tunnel is astronomically > expensive. The big three auto makers in the United States (GM, Ford, > DaimlerChrysler) don’t all have their own wind tunnels because the cost of > making and maintaining one that is large enough to do large scale testing is > outrageous. But in these velocities we are talkiing about (around 300 miles per > hour, even higher with some compounds), if you were to try to test in a tiny > cross sectional area, the viscous forces from the walls would force a boundary > layer across nearly the entire test section, which would lead to premature > turbulence, and give non consistent results as the flow itself changes with > time. I’ll do some equating and see how large a boundary layer for this flow > would be over a flat plate. > > Even though this FLL, probably not a true wind tunnel, though basically > the same > > uses, would be small, the price is still quite large. The venturi effect > can be > > used to speed up the air flow, but is limited by the increasing size of > the > > boundary layer and the turbulence using this would create. cascading > baffles > > would probably have to be used, maybe even several cascades… plus some > room in > > order for the flow to "dampen" (dont’ know how to explain this phenomena). > > Steve > > Sorry bout it being off topic > > > Off topic I know but an arrow would only need a very small wind tunnel, > as > > > the venturi effect can be used to up the wind speed in the area where > the > > > arrow would be. Coventry University used this effect when helping with > the > > > early design of Thrust SSC. The model is tiny! > > > Boyracer. > Yep…still can’t understand why you’d need a "boeing" size tunnel, kind of > dificult to see whats happening to an arrow in the middle of a $nK/hour > tunnel n metres wide, when you can fit the whole thing, life-size, in a > small highspeed tunnel. But even more questionable is the way you would > analyse what you see…with an aircraft there is some range of > inclinations/attitudes in the air flow which define the flight envelope. > When an arrow flies it is rarely flying straight in the air flow but also it > is flexing and rotating. Unless you could actually measure it during a real > free flight (telemetry built in!), how could a tethered arrow give any > useful information? Or can you suggest how to simulate rotation and flex > over the flight time? > Zolan

Response:

depends how you want to attack this problem. micro-time elapse photography equipment can give you the frequency (Hz) of oscillation of the arrow. Now, if you want to see how this oscillation affects the flight and fluid, you can simulate this this oscillation by supporting the arrow in front, back, and centroid. The oscillations of an arrow quickly become hyperbolic shaped, and by moving these supports as a function of time, that will simulate the oscillation. As for measuring useful things,    (static and dynamic pressure), one would have to fit the arrow itself with pitot tubes (the ones i use aren’t small enough, but i believe they are out there for micro-pumps, etc.) that are lined up perfectly tangent to the flow to be measured, ususally done in cartesian coordinates. These would have to be then fitted to a pressure transducer, which wuold be then hooked up to a Data Acquisition Card then to a computer with time dependent data acquisition software (LabView for instance). So, whether or not i think it can be done, yes. Do i think its too much of a pain in the arse? quite possibly when you could simulate an equivalent system on a computer. Just some thoughts. Oh, you wouldn’t need a boeing tunnel, just any tunnel is astronomically expensive. The big three auto makers in the United States (GM, Ford, DaimlerChrysler) don’t all have their own wind tunnels because the cost of making and maintaining one that is large enough to do large scale testing is outrageous. But in these velocities we are talkiing about (around 300 miles per hour, even higher with some compounds), if you were to try to test in a tiny cross sectional area, the viscous forces from the walls would force a boundary layer across nearly the entire test section, which would lead to premature turbulence, and give non consistent results as the flow itself changes with time. I’ll do some equating and see how large a boundary layer for this flow would be over a flat plate. – Hide quoted text — Show quoted text -> Even though this FLL, probably not a true wind tunnel, though basically > the same > uses, would be small, the price is still quite large. The venturi effect > can be > used to speed up the air flow, but is limited by the increasing size of > the > boundary layer and the turbulence using this would create. cascading > baffles > would probably have to be used, maybe even several cascades… plus some > room in > order for the flow to "dampen" (dont’ know how to explain this phenomena). > Steve > Sorry bout it being off topic > > Off topic I know but an arrow would only need a very small wind tunnel, > as > > the venturi effect can be used to up the wind speed in the area where > the > > arrow would be. Coventry University used this effect when helping with > the > > early design of Thrust SSC. The model is tiny! > > Boyracer. > Yep…still can’t understand why you’d need a "boeing" size tunnel, kind of > dificult to see whats happening to an arrow in the middle of a $nK/hour > tunnel n metres wide, when you can fit the whole thing, life-size, in a > small highspeed tunnel. But even more questionable is the way you would > analyse what you see…with an aircraft there is some range of > inclinations/attitudes in the air flow which define the flight envelope. > When an arrow flies it is rarely flying straight in the air flow but also it > is flexing and rotating. Unless you could actually measure it during a real > free flight (telemetry built in!), how could a tethered arrow give any > useful information? Or can you suggest how to simulate rotation and flex > over the flight time? > Zolan

Response:

– Hide quoted text — Show quoted text -> Even though this FLL, probably not a true wind tunnel, though basically the same > uses, would be small, the price is still quite large. The venturi effect can be > used to speed up the air flow, but is limited by the increasing size of the > boundary layer and the turbulence using this would create. cascading baffles > would probably have to be used, maybe even several cascades… plus some room in > order for the flow to "dampen" (dont’ know how to explain this phenomena). > Steve > Sorry bout it being off topic > Off topic I know but an arrow would only need a very small wind tunnel, as > the venturi effect can be used to up the wind speed in the area where the > arrow would be. Coventry University used this effect when helping with the > early design of Thrust SSC. The model is tiny! > Boyracer.

Yep…still can’t understand why you’d need a "boeing" size tunnel, kind of dificult to see whats happening to an arrow in the middle of a $nK/hour tunnel n metres wide, when you can fit the whole thing, life-size, in a small highspeed tunnel. But even more questionable is the way you would analyse what you see…with an aircraft there is some range of inclinations/attitudes in the air flow which define the flight envelope. When an arrow flies it is rarely flying straight in the air flow but also it is flexing and rotating. Unless you could actually measure it during a real free flight (telemetry built in!), how could a tethered arrow give any useful information? Or can you suggest how to simulate rotation and flex over the flight time? Zolan

Response:

Even though this FLL, probably not a true wind tunnel, though basically the same uses, would be small, the price is still quite large. The venturi effect can be used to speed up the air flow, but is limited by the increasing size of the boundary layer and the turbulence using this would create. cascading baffles would probably have to be used, maybe even several cascades… plus some room in order for the flow to "dampen" (dont’ know how to explain this phenomena). Steve Sorry bout it being off topic – Hide quoted text — Show quoted text -> Off topic I know but an arrow would only need a very small wind tunnel, as > the venturi effect can be used to up the wind speed in the area where the > arrow would be. Coventry University used this effect when helping with the > early design of Thrust SSC. The model is tiny! > Boyracer.

Response:

– Hide quoted text — Show quoted text -> To build a reputable wind tunnel, the costs are astronomical…. I doubt that > there is too much benefit to arrow companies to using such places, because > testing time is ridiculously expensive. Now, if they used a FLL(bascially a > mini-wind tunnel), possibly they can get some use for it. Most of the physical > phenomena behind arrow flight and design can be calculated and or represented in > simulations (Fluent, StarCD, etc.). Not saying wind tunnels wouldn’t be cool to > mess around in. The largest one in the world is in the US, I believe its owned > by boeing, but not too sure, i’m sure they rent it out to whoever can pay for > it. This wind tunnel uses about the same electricity as a city of 250000 people. > Of course, thats an extreme, but it gives you some idea. When you consider the > fact that the arrow is traveling around 300 mph, it would take a substantial > tunnel to accurately simulate the arrow flight, especially in order to make that > kind of flow laminar in the arrows direction. Like a lot of other things, arrows > are probably designed using intuition, hand calculations, and estimates. Maybe > my idea of a wind tunnel differs from yours, if so i’m sorry for the rant.It > would be kinda cool to visually see the boundary layer, vortex shedding, and > turbulence generated by it, but these can also be simulated using a reynolds > number correlation.

Off topic I know but an arrow would only need a very small wind tunnel, as the venturi effect can be used to up the wind speed in the area where the arrow would be. Coventry University used this effect when helping with the early design of Thrust SSC. The model is tiny! Boyracer.

Response:

Hi all, Further to my posts in regard to wishlists for a national archery centre, i’m now on the look out for more specific details, particularly in regard to wind tunnels, something a number of people suggested: Specifically; 1. what are the benefits to archers, will club shooters improve much by using one? 2. are there many tunnels in the uk for this purpose? 3. do many arrow manufacturers have these as standard and if so, any in the uk? Any help much appreciated, regards, Simon Rispin

Response:

– Hide quoted text — Show quoted text -> Hi all, > Further to my posts in regard to wishlists for a national archery centre, > i’m now on the look out for more specific details, particularly in regard to > wind tunnels, something a number of people suggested: > Specifically; > 1. what are the benefits to archers, will club shooters improve much by > using one? > 2. are there many tunnels in the uk for this purpose? > 3. do many arrow manufacturers have these as standard and if so, any in the > uk? > Any help much appreciated, > regards, > Simon Rispin

I know a club whose field lies by one of the most high-tech wind tunnels in europe. What do you expect the archer is going to do in this tunnel? ( I can, almost, imagine that an arrow manufacturer might just have a use for one…ocassionally) Zolan

Response:

Mabe this could be a new "extreme" sport. You stand in the wind tunnel with your back to the target.  Fire into the wind and try to duck when the arrow comes back for the target.               What’s the worst that could happen?

Response:

> Mabe this could be a new "extreme" sport. > You stand in the wind tunnel with your back to the target.  Fire into the wind > and try to duck when the arrow comes back for the target. >               What’s the worst that could happen?

Someone throws a bottle of Dr Pepper at you. Tom

Response:

To build a reputable wind tunnel, the costs are astronomical…. I doubt that there is too much benefit to arrow companies to using such places, because testing time is ridiculously expensive. Now, if they used a FLL(bascially a mini-wind tunnel), possibly they can get some use for it. Most of the physical phenomena behind arrow flight and design can be calculated and or represented in simulations (Fluent, StarCD, etc.). Not saying wind tunnels wouldn’t be cool to mess around in. The largest one in the world is in the US, I believe its owned by boeing, but not too sure, i’m sure they rent it out to whoever can pay for it. This wind tunnel uses about the same electricity as a city of 250000 people. Of course, thats an extreme, but it gives you some idea. When you consider the fact that the arrow is traveling around 300 mph, it would take a substantial tunnel to accurately simulate the arrow flight, especially in order to make that kind of flow laminar in the arrows direction. Like a lot of other things, arrows are probably designed using intuition, hand calculations, and estimates. Maybe my idea of a wind tunnel differs from yours, if so i’m sorry for the rant.It would be kinda cool to visually see the boundary layer, vortex shedding, and turbulence generated by it, but these can also be simulated using a reynolds number correlation. Sorry, its very late at night and I tend to ramble on and on when i’m tired. Steve – Hide quoted text — Show quoted text – > Hi all, > Further to my posts in regard to wishlists for a national archery centre, > i’m now on the look out for more specific details, particularly in regard to > wind tunnels, something a number of people suggested: > Specifically; > 1. what are the benefits to archers, will club shooters improve much by > using one? > 2. are there many tunnels in the uk for this purpose? > 3. do many arrow manufacturers have these as standard and if so, any in the > uk? > Any help much appreciated, > regards, > Simon Rispin

Response:

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