Been doing particle simulations
Sometimes having trouble getting the particles to flow all the way through
In the upper geometry steady state simulation is fine
But unsteady state: the particles seem to nose dive into the wall no matter what Laura does
It is similar for the lower geometries as well
Dr. Chung: does this particle have mass? Yes, it is about 1 micron size
Dr. Chung: does it make any difference in unsteady whether you start from scratch or whether you start from unsteady simulation?
Laura: I don’t think I’ve tried that
Laura: A bit worried that the steady simulation has this ‘nose dive’ effect as well.
Talha: what is the pressure difference? 3 Pa
What is the maximum velocity: 1.5 m/s
Talha: maybe if pressure difference is high the particles will jump across that.
Dr Chung: So for steady state, when you look at your velocity field it looks normal?
Yes. Dr. Chung: so the particle doesn’t follow the velocity field?
Laura: no it doesnt
Dr. Chung: is it to do with the position you release the particles?
Can you move it a little bit down, I.e. a little bit down from the in plane surface.
Laura: I could assign it to a cross section
Dr. Chung: particle should follow the flow field exactly
Dr Chung: what is typical simulation time? 30 mins to 1 hour?
Dr. Chung: how many elements? Between 800,000 and 1million for the upper one
Dr. Chung: What base size do you set? 400%
Dr. Chung: you need to fix your final parameters soon
So as the base size is decreased, the absolute size of the prism layer is fixed to 2 mm
Dominic: have been re-doing the grid independence test with a finer mesh
Have given some results to Adrian
Talha: You gave adrian plane section velocity yesterday, but the bulk mean velocity is 0.1, which is quite low.
We are thinking maybe the 3pa is too low
Talha: where did you get the 3pa inlet condition from?
From a paper.
Dr Chung: maybe you can double check the source
Dr Chung: laura are you using 3pa as well? Yes
Dr. Chung: maybe you can look at the flow field around the jet area?
Check whether it is unsteady or steady
Adrian and I are doing the grid independence
Tom: I segmented the airways for patient 53
Dr Chung: you can use the patient 53 geometry to give to Adrian
Until you get the other one working
Tom: I was working out one pathway and getting the pressure drop.
Dr. Chung: you choose one airway each time and run the model.
Dr. Chung: read that angle change paper and find out what they actually measured
This needs to be sorted out for the viva
Have started writing up the report
I will now output the angle change, length, start and end point to Tom for the 1D model
Tried to get better boundary conditions however it would involve re-writing a lot of the program.
Seeing as there isn’t much time left and error checking takes so long there isnt enough time
Looking into research of CT scanning of the lungs
Adrian mentioned he found a paper of Weibull measuring the bronchioles of the lung, which Daniel wants to look into
Mainly rat and dog papers found
Dr Chung: Rat and dog ones are better than nothing
Well then maybe I can use the rat one
Dr Chung’s Concluding remarks:
Poster: spend very little time but get good marks
Can we set a draft report date, Dr Chung: yes
Group: how about mid to late week 9
Dr Chung: Everyone needs to bring proof to the remaining meetings, as I haven’t been shown anything yet.
This will stop Dr. Chung getting the wrong idea of what we are doing
Dr Chung: it is essential that we get the pressure drop from the lower airways
Dr Chung: at the moment we are not doing anything with them, by doing this we are increasing the mass flow rate as we are not putting that extra resistance on the end of the airways.
To reduce computing time, we chop the top bit off (i.e. get rid of the larger and average airways), as we know this bit, and then we need to get the pressure drop of the lower airways (i.e. from generation 6 down to the alveoli)
Dr. Chung: if you start from the trachea, you incorporate all of the error from the average airways.
Tom can start from wherever he likes but it is better to start from generation 6 with the inlet conditions that the 3D team generates.
Dr Chung: Next meeting: Wednesday 13:15
Dr Chung: maybe it is time to start writing up
Laura: we have already allocated work to different people