Re: Force instead of lift

Hello Bill

 This is a good suggestion, thank you.

 I understand about calculating 2(4) different CL-s.

 Do I also understand correctly we will than have use something you guys
did to the flaps once:

     <axis name="ROLL">
      .................
         <function name="aero/coefficient/CldF3">
            <description>
               Roll Moment Coefficient due to Asymetrical Fowler Flaps
Deflection
               calculated as difference between left and right flap lift
coef,
               times distance from centerline to MAC of surface.
            </description>
            <product>
               <value>     21.28</value>
               <difference>
                  <property>aero/coefficient/CLdF3R</property>
                  <property>aero/coefficient/CLdF3L</property>
               </difference>
            </product>
         </function>


in order to calculate the moments due to difference in individual CLs ?

With best regards,
Oleksiy Frolov

>
>
>> -----Original Message-----
>> From: Oleksiy Frolov [mailto:[email protected]]
>> Sent: Friday, September 30, 2011 3:43 PM
>> To: [email protected]
>> Subject: [Flightgear-flightmodel] Force instead of lift
>>
>> Hello
>>
>>  I am trying to simulate the effects of the differential wing
>> lift. Such as single wing stall due to the propwash loss at a
>> low speed, and the effect of the icing on a single wing
>> (which can happen during a deicing failure on that wing). All
>> of these are important aerodynamic effects.
>>
>>  Now, we know we only have one wing in jsbsim currently, not
>> 2. My idea is therefor to try using 2 <force> records to
>> simulate the wings separately, instead of the usual CL record.
>> This however would require some kind of algorithm to define
>> how the force origin moves to overlay with center of lift for
>> each wing, which is probably not an easy task
>>
>>  I was wondering if anyone have tried a similar approach
>> before, and if this problem pechaps has an easier solution ?
>>
>> Thank you
>>
>> regards,
>> Oleksiy Frolov
>>
>
>
> No reason that you couldn't build this inside of the existing JSBSim
> format
> without using the external forces. Divide your wing into panels, maybe (on
> each side) one that is influenced by the propeller slipstream, one not.
> Sum
> all of your lifts to apply them at the aero reference point. So with a two
> engine aircraft, you might have a total of four panels, two per wing half,
> one inboard in the slipstream, one outboard in clean air. A mismatch of
> forces left/right would normally shift the aero reference point left or
> right, but that can be resolved with a moment.
>
> You have a couple advantages doing this. A force at a distance is a
> moment,
> so if the outer panels are experiencing different lift forces, that lift
> times its arm creates a moment. If the aircraft is rolling, each wing sees
> a
> different angle of attack, and therefore different lift. This is usually
> handled other ways, but your method has the advantage of spinning
> properly.
> There are disadvantages, though.
>
> If you are going to that trouble, you might consider keeping the flaps and
> ailerons seperate as well, unless the actuator mechanism is guaranteed to
> never give you different flap or aileron angles.
>
> Bill
>
>
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------------------------------------------------------------------------------
All of the data generated in your IT infrastructure is seriously valuable.
Why? It contains a definitive record of application performance, security
threats, fraudulent activity, and more. Splunk takes this data and makes
sense of it. IT sense. And common sense.
http://p.sf.net/sfu/splunk-d2dcopy2