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Howto:Modelling hydrodynamics in JSBSim: Difference between revisions
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Howto:Modelling hydrodynamics in JSBSim (view source)
Revision as of 21:51, 6 December 2016
, 6 December 2016→Modelling hydrodynamic coefficients
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</syntaxhighlight> | </syntaxhighlight> | ||
The third component of the drag is due to planing. | The third component of the drag is due to planing. The planing force and moments are computed by the generic [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing.xml hydrodynamic-planing.xml] system. The system is based on a (simple) model of planing described in (H. Wagner, "Planing of Watercraft", 1933, translated from German as NACA-TM-1139 in 1948) which models the normal force created by a flat planing surface. | ||
The system is set up by providing geometric information about the location of the planing surfaces (assumed to be 3) in the hydro RP frame and two tuning parameters per surface, a scaling factor for the normal force and an additional skin friction coefficient (per ft^2 of wetted planing surface). | |||
<syntaxhighlight lang="xml"> | |||
<system file="hydrodynamic-planing"> | |||
<!-- Parameters defining the planing surfaces of the hull. --> | |||
<!-- NOTE: Coordinates in the hydro RP frame. --> | |||
<property value="27.20">hydro/planing/forebody-length-ft</property> | |||
<property value="14.76">hydro/planing/forebody-beam-ft</property> | |||
<property value="-7.28">hydro/planing/forebody-keel-z-ft</property> | |||
<property value="-12.17">hydro/planing/forebody-end-x-ft</property> | |||
... <!-- The same set of geometry information for the middle- and afterbody planing surfaces omitted. --> | |||
<property value="0.95">hydro/planing/forebody-normal-force-factor</property> | |||
<property value="0.90">hydro/planing/middlebody-normal-force-factor</property> | |||
<property value="0.85">hydro/planing/afterbody-normal-force-factor</property> | |||
<property value="0.001">hydro/planing/forebody-skin-friction-coefficient</property> | |||
<property value="0.001">hydro/planing/middlebody-skin-friction-coefficient</property> | |||
<property value="0.001">hydro/planing/afterbody-skin-friction-coefficient</property> | |||
</system> | |||
</syntaxhighlight> | |||
The system outputs lift, drag (Fbx) and side (Fby) forces as well as pitch and roll moments (yaw is missing presently) that need to be added into the corresponding channels of the craft specific hydrodynamics configuration. | |||
''''To be continued... '''' | ''''To be continued... '''' | ||