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[JSBSim] modeling fuel tank with arbitrary MoI

Good sims require good FDMs (the "thing" that makes an aircraft behave like an aircraft).

[JSBSim] modeling fuel tank with arbitrary MoI

Postby amue » Thu Nov 14, 2019 12:58 pm

Is it possible in JSBSim to model a fuel tank with arbitrary (local) MoI (Ixx, Iyy, Izz), i.e other than of spherical shape, that also updates the (local) MoI if fuel is consumed, so that Ixx/mass = Ixx_full/mass_full, Iyy/mass = Iyy_full/mass_full, ...?
amue
 
Posts: 92
Joined: Tue Apr 03, 2018 10:13 am

Re: [JSBSim] modeling fuel tank with arbitrary MoI

Postby Thorsten » Thu Nov 14, 2019 1:01 pm

Define several tanks in the specific configuration and let the fuel system drain them in a specific way as desired?

I don't think you get direct control over the inertia tensor, but by sub-dividing your point mass or tank you can conceptually get any higher moment of it.
Thorsten
 
Posts: 12490
Joined: Mon Nov 02, 2009 9:33 am

Re: [JSBSim] modeling fuel tank with arbitrary MoI

Postby V12 » Thu Nov 14, 2019 8:02 pm

Concorde has 13 tanks modeled as point mass and it working very nice. There is decent difference if You fly with fuel only in #1,2,3 vs #1,2,3,4,7A and 5A. For supersonic speed You need transfer fuel from forward tanks 9 and 10 into 11, CoG (and ofcourse MoI) will change dramatically.

Code: Select all
        <tank type="FUEL">    <!-- Tank number 0 -->
            <documentation>
                Tank 1 :
                - 1/2 radius of tank 5.
                - align 3/4 of gear track.
                - => 39.80 % MAC.
            </documentation>

            <location unit="IN">
                <x> 1170.0000 </x>
                <y> -114.0000 </y>
                <z>  -12.0000 </z>                                                    <!-- aeromatic -12 -->
            </location>
            <radius unit="IN"> 50 </radius>
            <capacity unit="LBS"> 9255.0100 </capacity>
            <contents unit="LBS"> 9255.0100 </contents>
            <temperature> 59 </temperature>                                           <!-- 15 deg C -->
        </tank>
        <tank type="FUEL">    <!-- Tank number 1 -->
            <documentation>
                Tank 2 :
                - 1/2 radius of tank 5.
                - align 1/2 of gear track.
                - near engine center.
                - => 76.10 % MAC.
            </documentation>
            <location unit="IN">
                <x> 1565.0000 </x>
                <y> -76.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 50 </radius>
            <capacity unit="LBS"> 10075.1300 </capacity>
            <contents unit="LBS"> 10075.1300 </contents>
            <temperature> 59 </temperature>
        </tank>
        <tank type="FUEL">    <!-- Tank number 2 -->
            <documentation>
                Tank 3 :
                - 1/2 radius of tank 5.
                - align 1/2 of gear track.
                - near engine center.
                - => 76.10 % MAC.
            </documentation>
            <location unit="IN">
                <x> 1565.0000 </x>
                <y> 76.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 50 </radius>
            <capacity unit="LBS"> 10075.1300 </capacity>
            <contents unit="LBS"> 10075.1300 </contents>
            <temperature> 59 </temperature>
        </tank>
        <tank type="FUEL">    <!-- Tank number 3 -->
            <documentation>
                Tank 4 :
                - 1/2 radius of tank 5.
                - align 3/4 of gear track.
                - => 39.80 % MAC
            </documentation>
            <location unit="IN">
                <x> 1170.0000 </x>
                <y> 114.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 50 </radius>
            <capacity unit="LBS"> 9255.0100 </capacity>
            <contents unit="LBS"> 9255.0100 </contents>
            <temperature> 59 </temperature>
        </tank>
        <tank type="FUEL">    <!-- Tank number 4 -->
            <documentation>
                Tank 5 :
                - center + radius = gear position.
                - => 49.40 % MAC.
            </documentation>
            <location unit="IN">
                <x> 1274.0000 </x>
                <y> -152.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 100 </radius>
            <capacity unit="LBS"> 15873.2800 </capacity>
            <contents unit="LBS"> 15873.2800 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 5 -->
            <documentation>
                Tank 6 :
                - 3/2 radius of tank 5.
                - align 1/2 of gear track.
                - before engine center.
                - => 66.70 % MAC.
            </documentation>
            <location unit="IN">
                <x> 1463.0000 </x>
                <y> -76.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 150 </radius>
            <capacity unit="LBS"> 25544.9600 </capacity>
            <contents unit="LBS"> 25544.9600 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 6 -->
            <documentation>
                Tank 7 :
                - radius of tank 5.
                - before engine center.
                - => 64.70 % MAC.
            </documentation>
            <location unit="IN">
                <x> 1441.0000 </x>
                <y> 152.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 100 </radius>
            <capacity unit="LBS"> 16325.2300 </capacity>
            <contents unit="LBS"> 16325.2300 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 7 -->
            <documentation>
                Tank 8 :
                - 3/2 radius of tank 5.
                - align 1/2 of gear track.
                - => 46.70 % MAC.
            </documentation>
            <location unit="IN">
                <x> 1245.0000 </x>
                <y> 76.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 150 </radius>
            <capacity unit="LBS"> 28302.9500 </capacity>
            <contents unit="LBS"> 28302.9500 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 8 -->
            <documentation>
                Tank 9 :
                - 3/2 radius of tank 5.
                - centred on plane axis.
                - => 16.90 % MAC
            </documentation>
            <location unit="IN">
                <x> 920.0000 </x>
                <y> 0.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 150 </radius>
            <capacity unit="LBS"> 24462.4900 </capacity>
            <contents unit="LBS"> 24462.4900 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 9 -->
            <documentation>
                Tank 10 :
                - 1/2 radius of tank 5.
                - centered on plane axis.
                - => 30.50 % MAC
            </documentation>
            <location unit="IN">
                <x> 1068.0000 </x>
                <y> 0.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 50 </radius>
            <capacity unit="LBS"> 26329.8100 </capacity>
            <contents unit="LBS"> 26329.8100 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 10 -->
            <documentation>
                Tank 11 :
                - 1/2 radius of tank 5.
                - centered on plane axis.
                - => 113.90 % MAC
            </documentation>
            <location unit="IN">
                <x> 1977.0000 </x>
                <y> 0.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 50 </radius>
            <capacity unit="LBS"> 22961.1400 </capacity>
            <contents unit="LBS"> 19735.3100 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 11 -->
            <documentation>
                Tank 5A :
                - radius of tank 5.
                - align 5/2 of gear track.
                - => 74.80 % MAC
            </documentation>
            <location unit="IN">
                <x> 1551.0000 </x>
                <y> -380.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 100 </radius>
            <capacity unit="LBS"> 4905.2900 </capacity>
            <contents unit="LBS"> 4905.2900 </contents>
        </tank>
        <tank type="FUEL">    <!-- Tank number 12 -->
            <documentation>
                Tank 7A :
                - radius of tank 5.
                - align 5/2 of gear track.
                - => 74.80 % MAC
            </documentation>
            <location unit="IN">
                <x> 1551.0000 </x>
                <y> 380.0000 </y>
                <z> -12.0000 </z>
            </location>
            <radius unit="IN"> 100 </radius>
            <capacity unit="LBS"> 4905.2900 </capacity>
            <contents unit="LBS"> 4905.2900 </contents>
        </tank>

Fly high, fly fast - fly Concorde !
V12
 
Posts: 2757
Joined: Thu Jan 12, 2017 5:27 pm
Location: LZIB
Callsign: BAWV12


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