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:

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.

Products:

Simulation CFD

Versions:

2010;2011;2012;2013;2014

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