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Virtual Disk - Ship propulsion

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Old   December 7, 2017, 23:03
Default Virtual Disk - Ship propulsion
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Daniel
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Just wondering if the Virtual disk adds resistance to the ship resistance?

I've already have the ship resistance but as soon as i add a virtual disk to simulate the propeller, my resistance increases at least twice. Didn't change anything i.e. mesh, physics model, dfbi, time-step.
The thrust value is pretty similar to my experiment but the resistance is at least 2x more.

Help, anyone?
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Old   December 8, 2017, 03:45
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Quote:
Originally Posted by dbalan View Post
Just wondering if the Virtual disk adds resistance to the ship resistance?

I've already have the ship resistance but as soon as i add a virtual disk to simulate the propeller, my resistance increases at least twice. Didn't change anything i.e. mesh, physics model, dfbi, time-step.
The thrust value is pretty similar to my experiment but the resistance is at least 2x more.

Help, anyone?
How did you add the virtual disk force? Sounds like you added the thrust force in the wrong direction (the coordinate System of the virtual disk is different than the lab coordinate system, i think z-direction for virtual disk is x in labratory) A simple way to check the thrust vs resistance is to use an Expression Report where you subtract the thrust x component from the resistance, this should be almost Zero (not taking into account the Propeller suction).
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Old   December 8, 2017, 21:27
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Originally Posted by Jonass19 View Post
How did you add the virtual disk force? Sounds like you added the thrust force in the wrong direction (the coordinate System of the virtual disk is different than the lab coordinate system, i think z-direction for virtual disk is x in labratory) A simple way to check the thrust vs resistance is to use an Expression Report where you subtract the thrust x component from the resistance, this should be almost Zero (not taking into account the Propeller suction).
I've added the virtual disk force via DFBI.
I've actually followed the tutorial in Star CCM, setting the coordinate system of the virtual disk to the coordinate system of the ship.
I was actually having problems with tutorial in Star CCM for a self propulsion ship as the ship will just trim and heave like crazy.
I was expecting my thrust for would be very high but it is the exact same value as my experimental value.
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