Formation flying and Aerodynamic efficiency
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mythbusters did it with prop planes. I dont know of any other research or experiments…
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Nope mate, for all
Well! good! … I’ve never noticed the jet wash when changing wing! … (maybe because I’m doing it right ) as during fighting wing. I remember one day, IRL, I’ve passed through the jet wash of my leader following him under a high AOA maneuver, my a/c initiated a roll departure… just had the time to counter act it … but byby leader! (wasn’t able to close him up after that energy lost)
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"No benefits at all if you are considering the risks and pilot’s tiredness. "
What should be the min/max distance between the fighters for fuel saving? Have you ever made experiments to check this out? Is there any research that have been conducted by (or for) your Air force to verify that?
some articals:
“http://www.guardian.co.uk/environment/blog/2009/aug/13/commercial-aircraft-formation”
“http://www.aviationchatter.com/2009/12/formation-flying-with-airliners-to-cut-fuel-costs/”
“http://www.gizmag.com/vortex-surfing-usaf/24582/”Thanks
Only thing I know, is that we are a little bit “tired” after that :
… personally, I do not imagine staying in that position 5 hours long or more.
EDIT: after having a look to your links … C-17 are not so close. But even at that distance, keeping that position for long cruise need a 100% attention during all the flight (may requirer reinforced or doubled crews depending on flight duration) and/or a good (reliable) AP.
Concerning the sim, personally I do not think it would change things a lot on a 2 or 3 hours F-16 mission (?) … I would simply prefer an AAR before entering hostile area.
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What should be the min/max distance between the fighters for fuel saving?
IMO, very close. (?) because turbulent airflow increase the drag… so if not at the right position, you will certainly burn more fuel.
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If there is no “air” modeled, why is there “turbulence” when caught in the tanker’s wake?
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Dee-Jay, the proposed “flock of C-17” formation would use special automated equipment to maintain formation distances for long periods of time. It wouldn’t be hand flown.
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IMO, very close. (?) because turbulent airflow increase the drag… so if not at the right position, you will certainly burn more fuel.
The wingtip vortex trails exist 60-120 sec depending on AC size on the ground this is why required spacing between landing AC. In the air even at high altitude if the vortex trails are existing 30-40 sec with traveling speed means km of spacing.
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If there is no “air” modeled, why is there “turbulence” when caught in the tanker’s wake?
My guess it is made be “hand”, it does not come from calculated airflow. Fly close to any fighter you will be fly as smooth as silk…
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The wingtip vortex trails exist 60-120 sec depending on AC size on the ground this is why required spacing between landing AC. In the air even at high altitude if the vortex trails are existing 30-40 sec with traveling speed means km of spacing.
But this vortex is moving away from a/c. How can you predict the trajectory of the vortex.
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But this vortex is moving away from a/c. How can you predict the trajectory of the vortex.
As the birds knows where are the vortexes. You can measure where they are or with today CFD modeling it is not a big issue to predict their locations.
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No, as I know. There is no medium (air) in Falcon modeling. Velocity and AoA and other factors are used to calculate the areo focres with FM data, but there is no interaction between AC and air. Forces are simply “summoned” on AC airframe, there is not real airflow calcuation. I do not know how many simulations are available which are calculating RL the airflow and aerodynamic forces, but I know only one, the X-Plane.
this is wrong and true
Wrong because there IS air modeling
temperature
pressure
humidity
volumetric mass
mean speed
rotation speeds
heat/mech turbulences
jetwashare modeled , are evoluitive parameters and have real actions on aerodynamics
True that there is no real Navier Stokes 3D calculation around airframe, simply because it is impossible with 2013 computation power and that would be useless because our modeling for F16 is VERY accurate (based on wind tunnel testing from NASA ).
i would add some specific stuff when AC is behind another, like i did for Jetwash…but jeeeeez …
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Wrong because there IS air modeling
I know*, but there is no medium between aircraft. The parameters of the air what you listed are counted for aerodynamics calculation but airframe does not generate vortexes, etc. and do not fly “in the medium”. There in no real air, that is why i wished to say only its parameters. The parameters of air is counted (I guess) for thrust (modify the thrust which is defined by FM) and density of the air I guess also different.
*When I tried to reproduce the climbing record of Streak Eagle - with well set EW - in Falcon the F-15 at high the acceleration always were slower as in RL as long a I did not set temperature which is typical in a cold winder morning. The climbing records of Streak Eagle can be reproduced with 2-3% accuracy. This means a very good FM/thrust model, because the acceleration of F-15 is well modelled from 0 to 40k feet.
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Mav, I was under the impression (engendered by the articles available for download from this very website) that rather than each packet of air being independently calculated for each quanta of time, instead forces are applied to each control surface individually and the vectors are summed to determine the course of the aircraft, with forces varying according to a number of factors.
this I believe is what molni was getting at, rather than attempting to point out that no real air was harmed in the making of this sim.
I trust my impression was not in error? if so, I might recommend the updating of the articles on the flight model.
I hope this is not the case, as they were a most entertaining and informative read.
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It’s already pointed in Mav-JP’s articles. Tabular data is used for angular movement coefficients together with (I presume) dynamic pressure. See the article talking about Navier-Stokes equations in the title.
What I don’t understand is whether compressible or incompressible flows are used in the sim for calculating the dynamic pressure in order to calculate the pitching/yawing/rolling moment coefficients and resulting movement. It’s never pointed out anywhere in the documents.
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What is meant by not modeling air is that there is no n-element tracking of the air medium. Computations are done with the assumption that the air’s properties are irrespective to previous interactions with objects. It’s not possible to for example have an airplane change the air and that changed air to affect another airplane. There is no air medium which can take on a history or have a memory. If you want an airplane behind another airplane to feel wake turbulence then it must be done directly from plane to plane, not plane-air-plane.
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It’s already pointed in Mav-JP’s articles. Tabular data is used for angular movement coefficients together with (I presume) dynamic pressure. See the article talking about Navier-Stokes equations in the title.
What I don’t understand is whether compressible or incompressible flows are used in the sim for calculating the dynamic pressure in order to calculate the pitching/yawing/rolling moment coefficients and resulting movement. It’s never pointed out anywhere in the documents.
compressible of course
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What is meant by not modeling air is that there is no n-element tracking of the air medium. Computations are done with the assumption that the air’s properties are irrespective to previous interactions with objects. It’s not possible to for example have an airplane change the air and that changed air to affect another airplane. There is no air medium which can take on a history or have a memory. If you want an airplane behind another airplane to feel wake turbulence then it must be done directly from plane to plane, not plane-air-plane.
well you are actually wrong…
in BMS, wake turbulence is done via AC - AIr - AC …
how ?
i have created a AIR rotation behind each AC and the physical model is reacting to the roation of the air around it … how ? well easy , the fact that the AIR is rotating makes it variable in force and direction, which is taken into account into the model as a varation of local parameters (like AOA , speeds , sideslip angle etc etc…)
so YES there is AIR in BMS, if you read the BMS flight models articles you will see that the improvment of AIR modelisation has taken several monts/years
without AIR, turbulence modeling would have been impossible…
i think you need to go flying back on FF or AF just to remind you what it was…then you will realize in BMS you fly IN AIR compared to the others
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Mav, I was under the impression (engendered by the articles available for download from this very website) that rather than each packet of air being independently calculated for each quanta of time, instead forces are applied to each control surface individually and the vectors are summed to determine the course of the aircraft, with forces varying according to a number of factors.
this I believe is what molni was getting at, rather than attempting to point out that no real air was harmed in the making of this sim.
I trust my impression was not in error? if so, I might recommend the updating of the articles on the flight model.
I hope this is not the case, as they were a most entertaining and informative read.
there are two aerodynamics models developped for BMS, one local (the one you described) used only by A10 in BMS and the other Global (the NASA one) used by F16 - AFM.
as said in the article, there is no NS calculation indeed , but saying there is no AIR is wrong…without AIR modeling , there would be ZERO force applied …
for instance Local Aero modeling models AIR on each part of the AC…with local AIR parameter
you guys believe Navier Stokes calculation IS the answer …but for a flight sim this is COMPLETELY useless…why calculating NS on a surface in real time when you know ALREADY (by Navier Stoke calculation done not in real time or by reverse engineering , or wind tunnel testing) what is the RESULT you need to simulate…
you wont get better result by calculing in real time NS on each surface rather than calculating (or testing) the same prior simulation, translate the result into tabular data and use the data in real time
i still dont understand why simmers dont get this point…
Flow equations are used to DEVELOP an aircraft , NOT TO SIMULATE IT once it already flies and been tested
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and actually to answer the original question
YES i could improve the AIR modeling of BMS by making the airspeed (which i did already for jetwash) and pressure different behind a AC…which will make immediatly the AC behind react accordingly…but jeeeeeez , i dont want to do that