[CFD] Lagrangian Particle Tracking
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- Опубликовано: 10 июл 2024
- A brief introduction to Lagrangian Particle Tracking, which is used to track the motion of solids through a moving fluid. It is often also called the Eulerian-Lagrangian Approach to solids transport. The following topics are covered:
1) 4:10 How are Lagrangian Particle Tracks different to streamlines?
2) 11:51 How is the particle motion affected by Buoyancy and Drag?
3) 20:56 How does ANSYS simplify the particle force balance?
#lagrangianParticleTracking #eulerLagrange #fluidmechanics101
NOTE: There is a slight error in one of the slides. The volume of a sphere is
pi d^3/6 and not pi d^3/8.
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Some useful references:
1) ANSYS Fluent Theory Guide
15.2.1 Equations of Motion for Particles
www.afs.enea.it/project/neptu...
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Disclaimer
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The methods, algorithms, equations, formulae, diagrams and explanations in this talk are for educational and demonstrative purposes only. They should never be used to analyse, design, accredit or validate real scientific / engineering / mathematical structures and flow systems. For such applications, appropriate trained, qualified and accredited (SQEP) engineers / scientists should be consulted along with the appropriate documentation, procedures and engineering standards. Furthermore, the information contained within this talk has not been verified, peer reviewed or checked in any way and is likely to contain several errors. It is therefore not appropriate to use this talk itself (or any of the algorithms, equations, formulae, diagrams and explanations contained within this talk) as an academic or technical reference. The reader should consult the original references and follow the verification and validation processes adopted by your company / institution when carrying out engineering calculations and analyses. Fluid Mechanics 101 and Dr. Aidan Wimshurst are not accountable or liable in any form for the use or misuse of the information contained in this talk beyond the specific educational and demonstrative purposes for which it was intended. 
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Hi Aidan, great intro to lagrangian particle tracking. Towards the end, why is Vp =pi*dp^3/6? Should not it be pi*dp^3/8 instead as mentioned in one of the first few slides for volume of sphere?
This is definitely a typo! I noticed it after i uploaded the video 🤦♂️sorry guys!
Very nice lecture. We are looking future topics on particle track . Thanks
For computation of Reynolds number which velocity should be used . Mean if particle is flowing with wind and falling due to gravity. We should take resultant .
@@fluidmechanics101 Actually the typo is in the earlier slide. Volume of the sphere is (4/3)*pi*r^3 = (4/3)*pi*(d/2)^3 = (4/3)*pi*(d^3/8) = pi*d^3/6
One of the reasons covid -19 is not that bad is because you've got the time to make videos and enlighten us. Thank you Dr. Aidan.
One of your top 5 videos Dr. Aidan, very clear as always. Looking foward for more videos of discrete phase model (DPM). I hope you enjoy your new coffe.
It was very helpful Aidan. Thank you very much.
Thank you so much for making such nice videos. If one looks at the summary slide, one can save so much time and have quick recap of LPT. Please continue to provide high quality videos. Lucky to find Fluid Mechanics 101. Thank you once again.
Wow, that's so great. This is one of the best lectures I have listened to. Keep it up Dr. Aidan. We'll continue to support
Thank you for your work, it's very helpful. I'm very interested in the next topics regarding particle tracks you mentioned in the movie!
Excellent video - crystal clear and really well presented.
Amazing video thank you so much! Really grateful for how carefully the concepts in this video have been explained.
Amazing! waiting for your future videos related to this topic
Thank! As usual, this was a very useful and understandable explanation!
Excellent topic! looking forward to see the next step covering size distribution
I am doing dispersion modelling that uses lagrangian particle tracking. Just discovered this channel and thank you for making it easy to understand. Excited to explore more videos on Yr channel on this topic 🙌
Very clear introduction. Nice one, thanks.
Thank you for such an awesome video.
Great, found this talk very useful. Thank you sir. Looking forward on your lecture on tracking particles in unsteady flow field and coupling between the flow field. thanks
Thank you Dr.Aidan for the great lecture
thank you so much these valuable lesson about cfd and ansys fluent.these are really helping me in learning the fluent basics .
one of the best material regarding LPT
Great explanation and Great content thank you very much for the video.
Hi Aidan, I just want to thank you for the efforts. It would be great to know more about Lagrangian Tacking.
Excellent information. I have been playing around with Ansys's discrete phase model (DPM) and read their manuals, but your explanation is better. Hope you do steady-state vs unsteady next, and other forces (e.g virtual mass etc)
Outstanding video well done High Compliance are working on Methane emissions from land fill sites in the UK so helped us tremendously to understand particulate movement.
Nice video.. looking forward for your next videos on termination, size distribution..thanks
Thank you for the lecture
Thanks!! This content is very helpful for the initial understanding of my M.Tech., thesis work....
Thanks for this videos. I am understanding many things. 🙏
An excellent introductory video on Lagrangian Particle Tracking! Looking forward to the next part with explanations on particle size distributions, steady and unsteady two-way coupling of these Lagrangian phase particles. Would it be possible to look at the evaporation and turbulence effects of these particles as well maybe?
Aidan you're saving my life I LOVE YOU
😂👍
It is a nice explanation, and easy to follow for beginners like me.
Hi Aidan, terrific talk about Lagrangian Particle Tracking, very clear as always. Looking forward for tracking within unsteady flow and two-way interaction.
Are you thinking about doing some videos about users defined scalars, maybe giving some basics about how to code them? This would be a very interesting topic for engineers working in industries.
Great job
Francesco
Hi, great lecture as always! Could you give a lecture on LES where you explain the math behind it and a typical configuration for a high Reynolds number flow? How do you estimate grid size, monitoring convergence, etc? Thank you!
You are amazing. Really.
As always found it very interesting! I would be waiting for your video on particle tracking termination criteria.:)
Maybe in Part 2?
@@fluidmechanics101 very useful video on particle tracking. Please release second part as soon as possible.
Thank you for sharing your knowledge. This helps a lot! I wonder why RUclips hasn't started an online education business cuz this is much better than my graduate courses that I paid thousands of dollars for.
Great to learn from someone my own age! It just feels like a uni mate explaining things to me
That's 100% what I'm going for 👍
Great. Thank you.
excellent work. I would like to know more about this subject
Thank you Aiden
i was hoping you cover the stokes number 😅
however great video, very helpful.
Actually, I believe Vp =pi*dp^3/6 is correct. But at about 22:50 Aidan just misspoke and said 8 rather than 6. Great lecture. Looking forward to more.
Outstanding
Hi Aidan, thanks for your very insightful introduction about the Lagrangian particle tracking. If possible, could you further introduce how to generate particles and how to deal with exchanges with the continuous fluid? many thanks!!!!!
Thank you for this awesome video Dr. Aidan. I have a question, how is this different from Passive Scalar Transport?
thank you.
Amazing video! Would you teach the two-way coupling later, i.e. how to account for the particle's influence on fluids?
Very useful.....
more great content as always. Very clear.
Have you came across CONVERGE CFD code, specifically its use of adaptive meshing with no mesh created by user. Its quite interesting, however I am not convinced by its abilities to resolve BL that well. I understand its primarily aimed at engine simulations.
yes! thank you =)
It was an amazing talk.
Can you please introduce some references for Lagrangian particle tracking?
Hi,Aidan
Exciting as always,could you please make a video relating solid _ liquid equations and correlation on porous media.
Many thanks.
Very nice and clear explanation.
So in the video, we learnt the particle movement due to the fluid flow, but how about the effect of the sphere particle to the fluid flow? In another word, can we do a two-way coupling of fluid and the sphere particle?
Hello thank you for your content. All of them are very helpfull. Can you suggest books or other resources for study turbulence models?
Great explanation about Lagrangian Particle Tracking and the estimation of Reynolds number and drag coefficient in stationary fluids as well as in fluids in motion. Do You have a computer routine [Matlab, Python, R...etc] that You can share in this channel ?
Very lucid explanation Aidan.
I have a question. I read somewhere what I am quoting below. Would you please shed some light on that?
"Lagrangian tracing is not a problem if one is interested in a specific event of short time duration in the simulation. This is, however, a time-consuming process, and 'cannot be used' to study global evolution and long-term time evolution."
-is this right that it can't be used for global evolution and useful only for local part?
You can use Particle tracking for long term evolution. However, you need to check two things:
1) that your particles do not ‘time-out’ (exceed the maximum time allowed for tracking)
2) that the particle tracks are unsteady and are updated as the flow field updates.
Beware though, you will get some very large data files ...
Cool thank you
It would be nice to have a video about rules of thumb for using Euler Euler or Euler Lagrangian for two phase flow simulations.
Thank you very much for such a wonderful lecture.
How are the inert particles are tracked in the study-state fluid flow simulations?
Looking forward to your upcoming lectures.
You just advance the particles through a frozen flow field for a length of time that you specify. The only difference between steady and transient is that the background flow field is updated every time you move the particle in a transient calculation. In steady state, the background flow field stays the same
At 3:57 “they won’t move with the background fluid flow”. They absolutely will unless acted upon by another force in your case gravity, in another inertia- if the streamlines are curved. The particles in that slide would fall vertically downwards having no drag forward or backwards as they match the forwards velocity.
Thank you for this precious contribution. Can you suggest me a textbook where I can go in further details?? I am also using Ansys theory guide but it does not clarify many things. Thank you
Hu man, awesome videos! Can you do a lesson about che staggered grids used in CFD? World be awesome
Can you please make a video about a range of boundary conditions available in OpenFOAM and ANSYS fluent and its impact on the flow field??
Great quick introduction, but I think something is missing here! You discussed the momentum transfer from the fluid to the particle which appears in form of drag force (and buoyancy), but doesn't the particle motion also affect the fluid velocity?! So, shouldn't we also add a source term in the Eulerian momentum equation to account for the momentum transfer from the particle to the fluid?
Yes correct! The particle momentum should affect the fluid momentum. However in the Lagrangian Particle Tracking approach the mass of the each particle is much smaller than the mass of the fluid in each cell (because the particle diameter is small). Therefore the momentum source in the fluid is small and we can neglect it. If you want a multiphase approach that is two way coupled then you will need to look at a different method (e.g discrete element method, fluidised bed etc)
very nice explanation.
One point I couldn't understand clearly.
What is the difference between Up in eq(16) and in eq(4).
Sir kindly make more videos on particle tracking
I think this was a very enlightening insight in particle trajectory tracking. My question is, what if the is perpendicular to the 2D plane...so basically it does not affect the tajectory by bringing the object down, because this direction simply does not exist. At the same time the object isn's as small as a sand grain....what would the approach be there.
Thank you.
nice
Hi Aidan. Again, thanks for the great lecture as always. A minor question at Video 19:17. On the right side of the equation for updating the particle position (item#4), I assume the particle velocity used to update time step i+1 position should be i instead of i+1, correct?
Yep 👍
Impact on the Lagrangian particle tracking because of phase change (mass transfer) ? Thankyou
Thank you it was great! please go to particle size distribution for the next video
Yea i didnt really have time to do the PSD! Maybe part 2?
Fluid Mechanics 101 that would be great!
✌️👍👍👍
Can we get a video on flux limiter in FVM.
Hi Aidan, my name is Claus its is great to follow your videos. I am a new in CDF and use Inventor 21. However, the simulation i need to perform is a centrifuge. I have mainly three elements to look at, the Fluid, water, the solids, sand particle size Micron size to 6 mm, the fluid carries about 50% solid. Two types of solids, sand density about 1.6 heavy metal density about 18. Sand and water are waste the metal i need to capture. The planned volume floe of slurry into the centrifuge is about 25dm³ per second. The future topics as you have stated may help me to do the simulation but am not sure that at my current knowledge base am up the task doing the simulation correctly. The taks will be to optimize the flow and optimize separation of metal from other solids and water. I also expect that at the upper end of the trommel (exit of water and sand, to find a region where water and sand are separated in a way that it might be possible to capture the water separate from the sand, rather than lead the waste int settlement ponds. can you help
Yes 😊 as a first step, see if you can just calculate the flow field (ignore the particles for now). Make a good mesh, have a go at calculating the flow field and then try and do the particle tracking later 👍
Hello, hope you are doing great.
I am having a doubt on Particle number density (no. of particles per unit volume, 1/m^3) distribution of an inert particles obtained at a specific height in a two-phase fluid (water-solid particles) exiting the nozzle simulated in ANSYS Fluent. So, can I know how this radial particles number density distribution (1/m^3) can be converted to only number distribution (i.e., no. of particles distributed radially). Is it possible to find the no. of particles distributed radially at a specific height towards the downstream of two phase fluid exiting the nozzle in steady state simulations of two-phase flow.
Thanks in advance.
I think you might need to open the tracking file and do the calculation manually by importing the file into MATLAB. I know you can do this with the tracking file in CFX but I am not sure about fluent
Thank you for the explanation! One thing which is still bothering me slightly is that the fluid is going to be transferring momentum to the particle via drag. The same thing will happen with temperature via conduction, though that seems somewhat less relevant. Are we considering the momentum/heat transfer's effect on the CFD (fluid) solution to be negligible?
Yes! As the particle diameters are typically very small, their mass is small. Hence their momentum and heat transfer to the fluid is small and we can usually neglect it (unless the particles are large / macroscopic)
Does the particle modify the streamlines? That is to say, does the solver takes into account the effect of the volume of the particle when calculating the streamlines?
This depends on whether you are using one way coupling or two way coupling. If you have one way coupling then the particles have no effect on the fluid. If you have two way coupling then a momentum source is added to the fluid to account for the effect of the particle motion on the fluid
can you explicitly do the video on the workling of Ansys Fluent using the software that will be more intuitive and comprehensible for lots of student like us.
thanks for this video BTW.
hello, thanks for the video! one question that I have from the lecture, in equation 25 about the particle relaxation time, shouldn't appear also the density of the fluid? if the fluid and the particle have the same density the particle even thought it has a really high density, or particle size it would not go down, no? or I am missing something? I thought that it was the kinematic viscosity but no, it is only the viscosity of the fluid....
thanks
Ahhh i must have made a typo 🤦♂️
@@fluidmechanics101 I am not at all sure, it was more of a question 😅
Very interesting question. I think for the relaxation time, the dynamic viscosity fluid is enough to define it. There is no need of density of fluid per se.
If you look at this formula dimensionally, putting kinematic viscosity messes it up.
Is it possible if we applying saffman lift force in ansys than velocity of particle will become higher than the flow velocity ????
That is a good question. I haven't looked into the Saffman lift force in detail (it is usually neglected) so I don't know. Have a look at the basic equation of motion for the particles (force balance). Does it permit a solution where U > Ufluid?
@@fluidmechanics101 thank u i got my answer
I had one question, why do we have to mention the mass flow rate as well as the velocity of the particles when we are defining a particle source. I get why we have to input the velocity, but how does the mass flow rate come into picture?
The mass flow rate is just a convenient way of specifying the number of particles per second. Each particle has a mass and a velocity and we represent a group of particles by a Lagrangian particle. This is usually easier for the user as they are more likely to know the mass flow rate than the 'number flow rate' as this is likely to be a pretty large number
@@fluidmechanics101 oh alright. Thanks for the clarification and the amazing video.
Anytime 😊 glad you found it useful
what is mu in the Reynold's number?
The dynamic viscosity of the fluid that the particle is passing through 👍
Please make a lecture on k - omega model.
Coming soon! 🙃
The streamlines are instantaneous flow pattern and streakline is an instantaneous snapshot of a time integrated
flow pattern. So can we say that Lagragian particle tracking is time averaged phenomenon or will it change at every time step?
You can run LPT over the final flow field, the time averaged flow field or have them update dynamically with each time step, so it is up to you! You can do many things with LPT 😊
@@fluidmechanics101 Thanks for reply Aidan. I am having great learning with your videos.