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Meeting Minutes 17/02/12


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