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Motion: Total Torque appears to lag behind Hydraulic Torque in an Angular Motion Simulation

Issue

For an angular motion simulation, the total torque reported in the Torque Output file appears to lag behind the hydraulic torque.

Solution

Autodesk® Simulation CFD uses the torque at the beginning of the time step to determine the motion of the object:

d(omega)/dt = torque / rotational inertia

d(theta)/dt = omega

torque = hydraulic torque + spring torque + driving torque - resistive torque

The Torque column is the net torque determined at the beginning of the time step. Once this net torque is used to update omega and theta, a new part position exists, and we can compute a new hydraulic torque for the position at the end of the time step. The "Torque" is computed at the beginning of the time step and the "Hydraulic Torque" is computed at the end of the time step.

For a problem that does not have springs or external driving or resistive torque, the Hydraulic Torque at the end of a time step becomes the "Torque" at the beginning of the next time step.


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  • Document Information

    Published date: 2012-Mar-04
    ID: TS17522982

     

    Applies to:
    Autodesk® Simulation CFD 2014
    Autodesk® Simulation CFD 2013
    CFdesign 2010
    CFdesign 2011
    Autodesk® Simulation CFD 2012