How do I invoke this function (specify the vector) and get the return value (hit point)?
November 17, 2005: Version 0.9.9 released:
“Added a function that can intersect any arbitrary vector with the loaded scenery and return the hit point.”
On Thursday 02 March 2006 10:17, wlummis <at> aurora.aero wrote: > How do I invoke this function (specify the vector) and get the return > value (hit point)? > > > > November 17, 2005: Version 0.9.9 released: > > > > "Added a function that can intersect any arbitrary vector with the > loaded scenery and return the hit point." Just click, and see the output in the terminal. Ampere ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
Hello ! Does anyone know if YASim is able to simulate the following: 1. Wing lift change because of the propwash in twin engine airplane. 2. Prop discing effect on high rpm and low torque, where propeller actually produces negative thrust in close to 0 blade angle. What simulation algorithm was used in YASim to simulate the turbine and propeller physics for turboprops ? Thanks ! Regards, Oleksiy ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
Oleksiy Frolov wrote: > 1. Wing lift change because of the propwash in twin engine airplane. 2. > Prop discing effect on high rpm and low torque, where propeller actually > produces negative thrust in close to 0 blade angle. 1. No, YASim doesn't model inter-surface wash and flow effects. The only airflow the surfaces see is the global one. 2. Yes, sort of. YASim does model negative blade pitch (albeit in an abstract coordinate space where "pitch" is a factor, not an angle) Whether it does so well or not is an open question. I don't know anyone who has compared it to a real aircraft. > What simulation algorithm was used in YASim to simulate the turbine and > propeller physics for turboprops ? It's an energy balance model based on a nominal efficiency curve specified by the configuration. This has the advantage of working really well in the middle of the operating range, leading to good thrust estimates even with minimal input data. The disadvantage was mentioned above: performance at the extremes of the performance regime (windmilling, for another example) tends to produce funny effects. Some of this can probably be tuned away for a given application. Andy ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
Hello Andy! Thanks for the answers > 1. No, YASim doesn't model inter-surface wash and flow effects. The > only airflow the surfaces see is the global one. Would it be possible to overcome this limitation by dynamically altering a lift coefficient separatelly for each wing, or in the worst case, using the spoilers ? In the aircraft I am trying to simulate (Dash8 Q400) there is a huge difference in a lift produced by the wing with and without the propwash. Thanks, Oleksiy > Oleksiy Frolov wrote: >> 1. Wing lift change because of the propwash in twin engine airplane. 2. >> Prop discing effect on high rpm and low torque, where propeller actually >> produces negative thrust in close to 0 blade angle. > > 1. No, YASim doesn't model inter-surface wash and flow effects. The > only airflow the surfaces see is the global one. > > 2. Yes, sort of. YASim does model negative blade pitch (albeit in an > abstract coordinate space where "pitch" is a factor, not an angle) > Whether it does so well or not is an open question. I don't know > anyone who has compared it to a real aircraft. > >> What simulation algorithm was used in YASim to simulate the turbine and >> propeller physics for turboprops ? > > It's an energy balance model based on a nominal efficiency curve > specified by the configuration. This has the advantage of working > really well in the middle of the operating range, leading to good > thrust estimates even with minimal input data. The disadvantage was > mentioned above: performance at the extremes of the performance regime > (windmilling, for another example) tends to produce funny effects. > Some of this can probably be tuned away for a given application. > > Andy > > > ------------------------------------------------------- > This SF.Net email is sponsored by xPML, a groundbreaking scripting > language > that extends applications into web and mobile media. Attend the live > webcast > and join the prime developer group breaking into this new coding > territory! > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 > _______________________________________________ > Flightgear-flightmodel mailing list > Flightgear-flightmodel <at> lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-flightmodel > ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
Oleksiy Frolov wrote: > Would it be possible to overcome this limitation by dynamically > altering a lift coefficient separatelly for each wing, or in the > worst case, using the spoilers ? Not without major surgery, unfortunately. The Right Thing here would be to model inter-object effect using a flow field for every object (lifting surface, fuselage, prop, etc...) producing aerodynamic force and use it in a feedback mode to calculate actual airflow at each point. That's going to be complicated and slow. Modifying the wing (or other surface) coefficients directly is probably not a great idea, as those are generated by and intimately involved in the solver computation. You could get the performance effect you want only by making the solver input numbers a lie. If you want a special purpose hack (er, "solution") for this aircraft, one thing you could consider is using a <thruster> object in the wash area of the wing, pointing it appropriately, and adjusting its THROTTLE input based on engine power and airspeed using a little Nasal. This would still need to be set properly at solution time (when Nasal is not available), so there's significant complexity. But you can make the solution as accurate as you want. Andy ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
Hello Andy I see. The effect we actually would like to demonstrate to the students is that when the airplane flies with power on at the near stall condition, the lost of a single engine at the low altitude is more dangerous, then the lost of both engines, because the single engine lost would result in a single wing stall from which the airplane is very hard to recover. Do you think thrusters approach may help in this situation ? If not, do you or anyone else may be know if the effect of the prop flow on lift can be simulated with JSBSim ? Thank you Regards, Oleksiy > Oleksiy Frolov wrote: >> Would it be possible to overcome this limitation by dynamically >> altering a lift coefficient separatelly for each wing, or in the >> worst case, using the spoilers ? > > Not without major surgery, unfortunately. The Right Thing here would > be to model inter-object effect using a flow field for every object > (lifting surface, fuselage, prop, etc...) producing aerodynamic force > and use it in a feedback mode to calculate actual airflow at each > point. That's going to be complicated and slow. > > Modifying the wing (or other surface) coefficients directly is > probably not a great idea, as those are generated by and intimately > involved in the solver computation. You could get the performance > effect you want only by making the solver input numbers a lie. > > If you want a special purpose hack (er, "solution") for this aircraft, > one thing you could consider is using a <thruster> object in the wash > area of the wing, pointing it appropriately, and adjusting its > THROTTLE input based on engine power and airspeed using a little > Nasal. This would still need to be set properly at solution time > (when Nasal is not available), so there's significant complexity. But > you can make the solution as accurate as you want. > > Andy > > > ------------------------------------------------------- > This SF.Net email is sponsored by xPML, a groundbreaking scripting > language > that extends applications into web and mobile media. Attend the live > webcast > and join the prime developer group breaking into this new coding > territory! > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 > _______________________________________________ > Flightgear-flightmodel mailing list > Flightgear-flightmodel <at> lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-flightmodel > ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
> I see. The effect we actually would like to demonstrate to > the students is that when the airplane flies with power on at > the near stall condition, the lost of a single engine at the > low altitude is more dangerous, then the lost of both > engines, because the single engine lost would result in a > single wing stall from which the airplane is very hard to > recover. Do you think thrusters approach may help in this situation ? > > If not, do you or anyone else may be know if the effect of > the prop flow on lift can be simulated with JSBSim ? > > Oleksiy Oleksiy, I don't think anyone has tried this with JSBSim, yet. I've been looking into this lately, and have been writing an extensive paper on modeling aircraft with JSBSim. I _believe_ that prop effects on the wing can be modeled using the newest version of JSBSim-ML (JSBSim Markup Language), v2.0, due to the inclusion of function specifications. The idea would be to create both a function for a lift delta due to prop wash for each engine, and also a function for roll moment delta due to prop wash for each engine. It's just an idea, and I haven't considered it fully, but I hope someone will at some point; I'll probably get around to it sooner or later. If you want to try that out I can probably make some suggestions later. Jon ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid0944&bid$1720&dat1642
Berndt, Jon S wrote:
> I don't think anyone has tried this with JSBSim, yet. I've been looking
> into this lately, and have been writing an extensive paper on modeling
> aircraft with JSBSim. I _believe_ that prop effects on the wing can be
> modeled using the newest version of JSBSim-ML (JSBSim Markup Language),
> v2.0, due to the inclusion of function specifications. The idea would be
> to create both a function for a lift delta due to prop wash for each
> engine, and also a function for roll moment delta due to prop wash for
> each engine.
I had a stab at it once with the DHC6 but I needed a per engine thrust
coefficient which wasn't available a year ago. You might want to
consider using that one instead since a lot of data is available for it
(and used in the configuration file), including an all ice covered
configuration from LaRCsim/UIUC.
From the old file:
<AXIS NAME="PITCH">
<!-- AIAA -->
<!-- COEFFICIENT NAME="DCmTr" TYPE="TABLE">
Pitching_moment_due_to_right_engine_thrust
22 2
aero/alpha-rad
fcs/flap-pos-deg
aero/qbar-psf|metrics/Sw-sqft|metrics/cbarw-ft|propulsion/c-thrust[0]
0.0 40.0
-0.3491 0.003 0.000
-0.2618 0.003 0.077
-0.1745 0.013 0.128
-0.1396 0.018 0.122
-0.1047 0.029 0.117
-0.0698 0.061 0.109
-0.0349 0.059 0.123
0.0000 0.072 0.144
0.0349 0.085 0.192
0.0698 0.094 0.320
0.1047 0.128 0.448
0.1396 0.189 0.504
0.1745 0.203 0.432
0.2094 0.224 0.376
0.2443 0.261 0.192
0.2793 0.291 0.000
0.3142 0.269 0.000
0.3491 0.234 0.000
0.4363 0.000 0.000
0.5236 0.000 0.000
0.6109 0.000 0.000
0.6981 0.000 0.000
</COEFFICIENT -->
Erik
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----- Original Message -----
From: "Berndt, Jon S" <Jon.Berndt <at> escg.jacobs.com>
To: <flightgear-flightmodel <at> lists.sourceforge.net>
Sent: Wednesday, March 22, 2006 6:08 PM
Subject: RE: [Flightgear-flightmodel] YASim prop discing and turboprop
engine
I had considered modeling the change in lift/stall speed for an AC520
twin in MSFS.
Full power stall: 40 mph
Idle power stall: 60 mph.
Losing one powerplant on a short field approach at 50 mph would clearly
be catastrophic!
FS has one 'spoiler' surface. One can set CL_ds, Cd_ds, and Cm_ds. By
controlling spoiler defection with a 'gauge', the Lift could be increased as
Prop Thrust increased. Note that would be appropriate only for symmetrical
throttle settings.
JSBSim is more tractable than MSFS. As Jon mentioned below, perhaps the
new Markup Language would enable setting two independent flap-like surfaces
which have a virtual deflection dependent on individual Prop Thrust.
Some time ago I mentioned there is a NASA report on 'Performance of
Light Twins'. It goes into a lot of detail on prop effects. Much more than
one would want.
Ron
> I see. The effect we actually would like to demonstrate to
> the students is that when the airplane flies with power on at
> the near stall condition, the lost of a single engine at the
> low altitude is more dangerous, then the lost of both
> engines, because the single engine lost would result in a
> single wing stall from which the airplane is very hard to
> recover. Do you think thrusters approach may help in this situation ?
> If not, do you or anyone else may be know if the effect of
> the prop flow on lift can be simulated with JSBSim ?
>
> Oleksiy
"Oleksiy,
I don't think anyone has tried this with JSBSim, yet. I've been looking
into this lately, and have been writing an extensive paper on modeling
aircraft with JSBSim. I _believe_ that prop effects on the wing can be
modeled using the newest version of JSBSim-ML (JSBSim Markup Language),
v2.0, due to the inclusion of function specifications. The idea would be
to create both a function for a lift delta due to prop wash for each
engine, and also a function for roll moment delta due to prop wash for
each engine.
.....
Jon"
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