How to display velocity using a tracking system?

Blaisem

Hello,

I want to analyze a fluid velocity in a moving rigid wall.

I use a tracking system (applied on the rigid wall) on HyperView to display the relative displacement of the fluid, but the option "use tracking system" is not available for the velocity.

How could I display the relative velocity?

Thank you in advance.

PaulAltair

I'm not sure this is possible (accurately), if your code is outputting a velocity, then that velocity may not be (simply) 'displayed in a tracking system' as the velocity 'in the tracking system' ought to be the derivative of the tracking system displacement(s) rather than a transformation of the velocity.

Given the simplest possible example, i.e. your tracking system is not rotating and has constant velocity (or at least constant acceleration), then the calculation would be 'possible' (though HV would still not allow it). In this scenario, you could create a derived result subtracting one velocity from the other?

But in any other scenario it becomes very complex, i.e. how do you define/measure the 'velocity' in any vector where that vector is itself undergoing a transformation over the same time period? You would need to get the derivative of the displacement at a high frequency to capture the velocity more accurately.

For displacement itself this isn't a problem as the values are absolute at a given time (we can derive the value from just 2 sets of coordinates), but because velocity is a derivative of displacement and (probably) the displacement is not linear vs time, then deriving that velocity at the time resolution of your animation results would be inaccurate if the vector is changing.

 

PaulAltair

I'm not sure this is possible (accurately), if your code is outputting a velocity, then that velocity may not be (simply) 'displayed in a tracking system' as the velocity 'in the tracking system' ought to be the derivative of the tracking system displacement(s) rather than a transformation of the velocity.

Given the simplest possible example, i.e. your tracking system is not rotating and has constant velocity (or at least constant acceleration), then the calculation would be 'possible' (though HV would still not allow it). In this scenario, you could create a derived result subtracting one velocity from the other?

But in any other scenario it becomes very complex, i.e. how do you define/measure the 'velocity' in any vector where that vector is itself undergoing a transformation over the same time period? You would need to get the derivative of the displacement at a high frequency to capture the velocity more accurately.

For displacement itself this isn't a problem as the values are absolute at a given time (we can derive the value from just 2 sets of coordinates), but because velocity is a derivative of displacement and (probably) the displacement is not linear vs time, then deriving that velocity at the time resolution of your animation results would be inaccurate if the vector is changing.