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Ship Self Propulsion Results in Negative Torque value

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Old   April 20, 2023, 08:44
Default Ship Self Propulsion Results in Negative Torque value
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Hi everyone, i have been working on ship self propulsion simulations including 2 dof (heave and pitch) with Virtual Disk method, using StarCCM+

There is no problem with setting the simulation up and running it, almost for all cases i get proper thrust value but negative torque value.

I use Hull Performance Workflow to set up the simulations, use thrust option for virtual disk, and enter the open water table (including kq instead of 10kq).

At first trials i have encountered "thrust input cannot be negative" error, and realized that it stems from Total Resistance estimation going negative at some point, which leads to negative thrust value and then the simulation stops. To overcome this i have employed absolute value of Total Resistance and since then simulations work just fine (not being sure if this is a proper way of overcoming this problem).

I want to know if it is natural to get negative torque values, and if not, what can be the most possible reasons and from which point should i start investigating the problem.

Thanks in advance.
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Old   April 23, 2023, 06:16
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Can you share the definitions of the coordinate systems that you use (with pictures) and the definition of the resistance report?
Also the inputs in the virtual disk model in the physics.

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negative torque., starccm+, virtual disk model

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