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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 21:32, 6 December 2016
, 6 December 2016→Modelling hydrodynamic coefficients
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* The force is scaled by the displacement, so it will decrease as the planing forces increase and lifts the hull towards the water surface. | * The force is scaled by the displacement, so it will decrease as the planing forces increase and lifts the hull towards the water surface. | ||
* The force is crudely increased as the beta angle increases (the drag increases when "side slipping" through the water, but in this case there is no data to base the increment on). | * The force is crudely increased as the beta angle increases (the drag increases when "side slipping" through the water, but in this case there is no data to base the increment on). | ||
* The Cd per lbs displacement value has been tuned to the graph above, but it was also necessary to modify the static buoyancy/displacement lift function to decrease it faster with speed to get a decent match (among other things this simplified model computes the buoyancy based on the undisturbed water level and, further, at planing speeds the interface between the hull and the water is very different from at slower speeds). | * The Cd per lbs displacement and ft^2 of hull cross section value has been tuned to the graph above, but it was also necessary to modify the static buoyancy/displacement lift function to decrease it faster with speed to get a decent match (among other things this simplified model computes the buoyancy based on the undisturbed water level and, further, at planing speeds the interface between the hull and the water is very different from at slower speeds). | ||
The rudder drag function, on the other hand, is simpler (the rudder angle penalty is just guessed): | The rudder drag function, on the other hand, is simpler (Cd has been tuned to the graph above while the rudder angle penalty is just guessed): | ||
<syntaxhighlight lang="xml"> | <syntaxhighlight lang="xml"> | ||
<fcs_function name="hydro/rudder-drag-lbs"> | <fcs_function name="hydro/rudder-drag-lbs"> | ||