simtk.org

Hello,

I am trying to match my simulation time steps to PC-MRI data. My period for this patient is 0.76734 (s) and the PC-MRI data has 50 evenly distributed frames (i.e. every 0.0156 s).
Originally, I decided to run 5 cycles, with 200 frames/cycle, and saving 50 of the 200 frames to match my data.

I inputted the following:

# of TS: 1000
TS size: 0.0038367
# of TS between Restarts: 50

However, this only gave me 4 time steps per cycle . I'm in the process of re-running my simulation now with the exact same inputs except I have changed "# of TS between Restarts" to 4 with the expectation it will now give me 50 frames/cycle. Is this correct?
If it is, I guess I'm confused why its called "restarts" it makes it seem like every 4 timesteps it will restart the cycle? Can you please explain this further to me so I know I'm running it properly?

Thanks for your help!

Kind regards,
Hannah

P.S. - if you have time could you also tell me for the pulsatile flow file whether I should be using the max velocity from each frame of the PC-MRI data or the average? I also have it set to a womersley profile because it is the inlet of the thoracic aorta.

Restart files are "snapshots" that record all variables during a simulation. They can be used to restart a simulation from a certain time point. If you want to have simulation snapshots that correspond to your 50 PCMRI data, you need to save a restart file every 0.0156s.

You ran 1000 time steps and dt=0.0038367. So your total simulation time is 3.8367s = 5 cardiac cycles for the patient.
Saving restart files every 50 time steps means that you have a snapshot every 50*0.0038367=1.91835s. You need to save a restart file every 4.066 steps (0.0038367*4.066=0.0156s) to have the same time interval as the PCMRI data. You can also adjust your time step size dt to be a factor of 0.0156s so you have an integer number for restart snapshots.
I am not sure about the last question. The inflow file is a volumetric flow waveform. I think you should make sure the flow rate is equal to the PCMRI flow rate (a velocity integral) at each time point.