plot pressure wavweform inlet and coronary

[Luca Gontier]

In the coronary project for obtain the pressure waveform at the inlet and at the coronary outlet, i used the file "all_results-pressures.txt" and converted the value in mmHg, but i do not obtain the same waveform and range. I tried view your project and your setting.
Can you please tell me which value i need to use, if i used the wrong file, so i can try with my simulation.

Thank you so much for your help

[Justin Tran]

Hi Luca,

Thank you for your question. The pressure waveform we have shown on the website is for the aortic inlet. Can you confirm that the pressure waveform you are looking at is also for the aortic inlet? Also, how far off are you simulation results from the ones displayed on the tutorial? Does the 3D results in "all_results.vtp" match up well with Figure 14?

[Luca Gontier]

Thanks for the helps tried for 1 cycle for test (Number of Timesteps: 1000, Time Step Size: 0.001, Number of Timesteps between Restarts: 50) I should get it if I did not mistake the wave for a cycle.You think i need to make the full simulation 6000 timestep?
I used your coronary project and not change any parameter. the vtp i think is different from figure 14 the pressure and i cannot understand why, i used the auto rescale in paraview i attach the file.
I used the file "all result pressure" converted in mmHg (dividing fo 1333) and plot a graph with tilmestep for 1 cycle and inlet value pressure. I think the idea it is correct.

[Justin Tran]

Hi Luca,

Thanks for the info. Yes you are right that running it for the full 6000 timesteps would help. The reason we do this is because the velocities and pressures in the computational domain are initialized to 0 (as the first time point in your plot indicates). It takes a few cycles for the system to "warm up" to the boundary conditions, so we typically run pulsatile flow simulations for 6 cycles and examine the results of the 6 and last cycle. By that time, all the transient behavior that originated from the 0 starting condition should be damped out. I would try re-running your simulation for 6 cycles (6000 time steps) then compare your results to the ones posted in the tutorial.

[Luca Gontier]

thank you so much.
I need to watch the 6 cycle for the pressure value and not the first, that was my error. I will try again the tutorial and after my project. I am confident this is the problem. You are also very helpful in helping these simple problem. I repeat the simulation and let you know.

Thanks

Luca

[Justin Tran]

Great glad to help! Let us know how it goes. We should make this fact more clear in our documentation, that 6 cycles are needed when running pulsatile simulations. Thank you!

[Luca Gontier]

Hi, i tried and it worked perfectly. I needed to look at the 6 cycle for plot the waveform.
Now i just need to find how to estimate the correct compliance, because I have a max pressure to high for my model.

Thank you

[Justin Tran]

Great! Glad to hear it worked out.

Estimating compliance is definitely tricky. Generally, an iterative approach ends up working the best where we adjust the compliance after running a simulation. Increasing the compliance leads to a dampening of the peak-to-peak pressure amplitude, while decreasing the compliance increases the peak-to-peak amplitude. But the mean pressure should not be affected by the value of compliance. If you need to increase or decrease the mean pressure, you will need to adjust the resistance values (more resistance leads to higher pressures, and vice versa).

[Luca Gontier]

I think i need to increase di compliance to decrease the max pressure who is to high. the waveform otherwise it is correct now.
The mean pressure i think it is a little low (85 mmHg) in my project and initially I set 93,33 mmHg like in the tutorial.
The resistance i need to increase is the R_tot for the aortic outlet, increasing the p_mean?

[Justin Tran]

Increasing the compliance will surely lower the systolic pressure from ~138 mmHg, but it will also raise the diastolic pressure. I did a quick calculation and it seems like your mean pressure is indeed around 93.33 mmHg, so you are right in that increasing the compliance should bring the pressure amplitude down without changing the mean pressure too much.

And yes, in cases where you want to increase the mean pressure, you would typically increase R_tot for the aortic outlet.