That's an amazing video mate! Especially that mention that, the dispersed-continuous and continuous-continuous interaction differs in how we define the interfacial area per unit volume. It was super helpful.
@engineersacademy41373 жыл бұрын
Appreciate alot.. One of the best CFD masters on KZbin. Really very informative and clear
@MalcolmAkner6 ай бұрын
Damn, you are such an expert in explaining this in a way where it feels simple and approachable. Excellent pedagogic skills Aiden!
@tusharthorat5925 Жыл бұрын
Great video. Simple and effective. It would be great if you can post a video on combustion models.
@RichardDuneSJTU Жыл бұрын
Thanks for your very detailed introduction.
@mihirmakwana20265 жыл бұрын
Hi Aidan. This video was very informative. A video on Lagrangian Multiphase model along with a comparison to Eulerian will be good sequel to this one. Cheers :)
@HaithamAhmed-kr8yl4 жыл бұрын
Really, Thank you for this valuable video. Go ahead ! We are waiting your new videos.
@hydrokbar20192 жыл бұрын
i think thanking is not sufficient for your efforts...i really mean it
@sanjaykumaryadav3186 Жыл бұрын
Amazing explanation. Thanks a lot.
@ryanlin51014 жыл бұрын
Thanks for your good teaching really. It's very literally. hope for next video about VOF model!
@nabekary4 жыл бұрын
Very nice explanation. Thanks a lot.
@shubhamphysicist4 жыл бұрын
Simply awesome
@kaushalsorte98703 жыл бұрын
Hello Aiden. This explanation was very helpful. Thanks. Could you please make a video on Volume of Fluid approach as well? Thanks in anticipation.
@akhileshwarsingh40544 жыл бұрын
Today, I watched this lecture and subscribed your channel. Your lecture was compact with quality. I am hoping some lecture related to interface tracking in multi-phase. I mean VOF model with explicit function. Thanks for this video.
@juancamilorojasvalencia92944 жыл бұрын
Very thanks , your content is very useful.
@thunder852za3 жыл бұрын
So in continuous-continuous flows, we don't normally model the ''surface drag'. For two incompressible fluids, the interface velocity is continuous. ie there is no phase velocity difference. However, I am talking about the single-fluid approach - which is the standard approach for fuel/tank slosh - maybe it is different in the multi-fluid approaches. I have never header of using the gradient as a stand-in for the surface area. I mean there is no mathematical reason for the gradient of the volume fraction to be related to the surface area, they are spatially orthogonal quantities. The gradient is used frequently as the interface normal (when normalised). For an algebraic VOF scheme, knowing the surface area of the interface is next to impossible, but for geometric methods, it is implicit in the scheme. Sorry perhaps because I work building these models I am being a bit critical. I love this channel in any case. Please don't take it personally, just a bit of confusion on my side. :D
@fluidmechanics1013 жыл бұрын
Good comments! I always appreciate feedback from people who actually develop the models, as it really helps clarify the understanding. The best I can ever go for is reading the manuals, equations and trying to make deductions from these 😄
@thunder852za3 жыл бұрын
@@fluidmechanics101 Thank you so much for taking the comment in good spirit. I was really worried it came across wrong and I really find these videos of great quality and I appreciate the work you do. I have learned a lot, and it's nice to be able to absorb advanced content in related but different areas of CFD. If you need to reach out regarding multi-phase stuff feel free. I am a Post-Doc in InCFD at the University of Cape Town. :D Thanks again for this channel.
@ashishtiwari19125 жыл бұрын
Good work. Your explanations are simple enough to understand. Keep continuing with the good work. I am a masters student in CFD so it sounds familiar. I would request you to make videos on hybrid RANS LES models and probably on parameters such as q criterion and vorticity.
@fluidmechanics1015 жыл бұрын
Thanks Ashish! Ive got lots of videos to come. I hope you find them all useful and easy enough to understand 😊
@hassanazizi84125 жыл бұрын
Great explanation. I would request you to kindly give an insight to the modelling of mass transfer mechanisms between the different phases in your next video.
@fluidmechanics1015 жыл бұрын
Hi Hassan, the mass transfer mechanisms are very tricky and im going to have to put some careful thought in before making a video. The essence of mass transfer is equal and opposite source terms in the volume fraction equations so that you get an effective transfer of mass between phases where you want it. For now i hope you have enough to help out with your CFD, while i research the video 😄
@water58254 жыл бұрын
@@fluidmechanics101 "The essence of ... source terms in the volume fraction equations ...": this eqn reads partial r_q/partial t+div(r_q U_q)=0 in your video, do you mean in the case of mass transfer between phases, e.g., phase change, we should add source terms on the rhs of the original volume fraction eqn?
@mick74batti4 жыл бұрын
Nice video, thanks. However, in the drag model, please note that what counts is the frontal area of a sphere, not its surface area. The Cd of a body is generally defined using its frontal area. Therefore, equation 12 turns out to be 3/2*rp/dp, not 6*rp/dp
@fluidmechanics1014 жыл бұрын
Well spotted! Thanks for the clarification 😊
@mick74batti4 жыл бұрын
@@water5825 The surface area of a sphere is 4*pi*r^2, the frontal area is the area of a circle, which is pi*r^2. So as you can see, the frontal area is 1/4 of the surface area!!
@anjanmevanrajapakse15113 жыл бұрын
Great lecture mate
@syedimran10522 жыл бұрын
very informative video... thank you very much!!
@ricardoguzman98445 жыл бұрын
Congratulations! Great work!
@abdelaal25 жыл бұрын
that was really informative and helpful thanks and great job
@Miao_zai4 жыл бұрын
Hello Aidan At 20:50 in the video, is that continuous-continuous interaction Cd is calculated same as Dispersed-continuous interaction Cd? All using the Schiller model? Thanks
@sergeianpilov52225 жыл бұрын
Wow, that is an unexpected leap - right into multiphase! Great lection again :> PS I know it's too much to ask for - but .. any plans for lections on evaportaion/condensation/boiling , break-up/coalescence, solid dispersed (granular temeprature etc)?
@fluidmechanics1015 жыл бұрын
😄 im glad you liked it! I havent looked into any phase change processes yet (they are quite hard) but it is something im going to look into in the future! General multiphase is the best place to start for sure with mass and heat transfer terms
@danieltarraf7881 Жыл бұрын
Thank you, may I ask a question ? Assume we are spraying water in hot air (~1000c). some of the water will evaporate. Now, At the beginning of time t=0 we know r_vapor = 0 every where (we don't have vapor yet). If we consider the equation (4), r_vapor will not change as time progress (r_vapor = 0 for every time step). Is this correct ? Should not we add a volume fraction term (representing the transfer from water to vapor) as we did to the continuity equation ?
@mohamedelbouti65563 жыл бұрын
Thank you for this amazing video, i just have a question regarding the VOF and mixture models, in Fluent when choosing VOF model we have also the option to choose dispersed interface , and when choosing mixture model , we have the option to choose sharp/ dispersed interface, could you please give more details about that ? Thanks
@oneuniverse66795 жыл бұрын
dude you are god for us. thanks. :D
@okhwatnoornoor8893Күн бұрын
If I want to see effect of variable gravity on RBCs in blood which model is better ?
@ehsanheshmati58423 жыл бұрын
Perfect
@toptentop10195 жыл бұрын
Thanks for good teaching
@fluidmechanics1015 жыл бұрын
Thanks 😊 glad you liked it!
@HENGELWIN3 жыл бұрын
Hi Aidan, if I want to simulate in Fluent for Moisture diffusion into something (like Electronic Packaging with voids inside them that allow moisture to diffuse in), do I need Multiphase model: Eulerian in this case?
@fluidmechanics1013 жыл бұрын
For moisture diffusion you can just use a mixture model. In fluent you need to define a custom fluid as a mixture of air and water vapour. Then enable species transport and fluent should solve for the mass fraction of water vapour which you can convert into a humidity. With moisture calculations, there are no distinct free surfaces or interfaces between the water droplets and the air so you don't need an Eulerian / Volume fraction based approach. I hope this helps!
@HENGELWIN3 жыл бұрын
@@fluidmechanics101 Thanks for the reply Aidan! will try that out.
@ikacar Жыл бұрын
Thank you.
@manchee23 Жыл бұрын
Hey Aidan great video, any plans of making an dedicated video series of multiphase in focus to mixture models .
@Lunamycat344 жыл бұрын
Great video Aiden. What model should I use if we have both continuous-continuous and dispersed-continuous interactions in the same flow system?
@fluidmechanics1014 жыл бұрын
If you are using CFX you should be able to have different interactions for different fluid couples. I am not sure about fluent or openfoam though
@samueltorres13225 жыл бұрын
Thank you for the clear explanation! For a project I need to simulate the dynamics and concentration profiles of polydispersed nanoparticles in a microfluidic and I was considering to approach the model using the Euler-Euler method in COMSOL (treating them as a dispersed phase), also introducing LES equations. Can this model be considered for nanoparticles? Do you think this approach could work?
@fluidmechanics1015 жыл бұрын
Hi Samuel, yes your approach seems reasonable and will probably work. Im not sure if LES is necessary though. It depends on what quantities you are interested in studying.
@edithlee62212 жыл бұрын
thank you alot
@coolguy16524 жыл бұрын
Thank you for the video. I had a question though, doesn't the two-phase full eulerian model also have an inequality bound restraint on the phase fractions (i.e. 0
@fluidmechanics1014 жыл бұрын
Yes, the CFD code uses a limiter to ensure that rq stays bounded in the range of 0 to 1. Limiters are quite complicated, so i havent covered them yet!
@SantiagoMarquezD4 жыл бұрын
Part of that restraint is imposed in the way you obtain your pressure equation, additionally you have to properly integrate the phase's transport equations.
@sapyman216 Жыл бұрын
Hi, can you please tell me what are the boundary conditions required to solve the volume fraction equation in VOF model?
@fluidmechanics101 Жыл бұрын
The standard boundary conditions normally work. Fixed values on the velocity inlets and zero gradient on the other surfaces
@sapyman216 Жыл бұрын
@@fluidmechanics101 Thanks Aiden. I have another query. In a dam break simulation using VOF, what will be the bc to be applied on the inner surface of the fluid while solving the volume fraction equation?
@TNDeepuKumarmed3 жыл бұрын
As it was mentioned that the dispersed particles are dissolved in the continuous fluid (1:53), So my doubt is if it is a solid particle then will it also get dissolved in CFD simulation? If we don't want the solid particle to be dissolved then what type of modeling approach (i.e., Models in CFD) needs to be followed? Thanks in advance
@fluidmechanics1013 жыл бұрын
If your particles are large, then you probably need to look at Discrete Particle Method / Discrete Element Method. It is available in Fluent or MFIX. Not sure about CFX or OpenFOAM though 👍
@TNDeepuKumarmed3 жыл бұрын
@@fluidmechanics101 So, you mean Dense discrete phase model (DDPM) with Eulerian phase?
@fluidmechanics1013 жыл бұрын
Yep
@leonardohenao76464 жыл бұрын
Hello Aidan. I Have a question. In air-water multiphase flow CFD simulation's it is common to use a VOF = 0.5 to track or identify the position of interface or free surface. I would like to know why this criteria is used and if it can always be assumed the same. Otherwise, I would like to know if volume fraction can be taken different to 0.5 and, if so, ask you about a methodology to find this volume fraction. In Summary: Which value of volume fraction I can to choose for to identify free surface in an air-water simulation of open channel? What you do is great! Thanks for sharing your knowledge!
@fluidmechanics1014 жыл бұрын
Hi Leonardo, yes you are right, it is common to use a volume fraction of 0.5 to track the free surface. This choice is arbitrary of course and you could really use any value between 0 and 1. The important thing to remember is that the CFD code can only resolve the free surface to within a cell. So perhaps a better way of defining it would be: the free surface exists in a cell where the volume fraction changes between 0 and 1. We cant say where in the cell it is, only that it is within a cell. So 0.5 is just useful as it is between 0 and 1. Interface compression algorithms usually try and steepen the gradient so that the volume fraction changes within 1 cell (instead of several) so it makes it easier to locate the free surface. I hope this helps 👍
@thunder852za3 жыл бұрын
In algebraic VoF approaches (CICSAM) this does get used. However, in the actual physics governing equations, there is no distinction, just a region of smoothly varying material properties (its why we do VoF). The 0.5 can help to localise certain terms for example surface tension and evaporation. Although even here typically you don't find 0.5 being used rather volume fraction \in (tole, 1- tole). The geometric methods have a discrete representation of the interface so for them, they 'know' where the interface is. In all, I would say the use of 0.5 is most commonly a post-processing thing.
@leonardohenao76463 жыл бұрын
@@thunder852za Very interesting. Do you recommend some book or paper where I can read about algebraic VoF approaches, particularly COMPRESSIVE AND HRIC MODIFIED? Thank you!
@fluidmechanics1013 жыл бұрын
I would have a read of Unno Ubbinks thesis (you should be able to find it on Google search) from Imperial College London
@adlinasir29534 жыл бұрын
Hello sir, may i ask a few question? Lets say i want to insert diesel fuel in chamber that contain air as their fluid. should i use multi phase model in order to separate the two fluid which is diesel and air to identify the flow of the diesel and if yes which model should i use?.. Thanks sir for answer my question before..
@fluidmechanics1014 жыл бұрын
Yep, i would use an inhomogeneous multiphase method (seperate momentum equations for diesel and oil). I would only go for a homogenous method if you are sure that the drag forces are only significant near the interface
@ketanganatra2403 Жыл бұрын
Dear sir... I referred to your video... can you add energy equation to eulerian model...??? I have checked the ansys fluent theory guide... there energy equation is not clearly interpreting in nature..in fact the energy equation contains the shear stress tensor and velocity vector....though energy equation should contain temperature or enthalpy term.. it will be helpful for me if you can reply...
@finophile Жыл бұрын
good video, but I have some problems with the metaphors. I suspect that you mean "suspension" not "solution" when you discuss Dispersed - Continuous. Specifically this is clear in (c) of sediment transport.
@mdkhairulbasharshovon55304 жыл бұрын
Hello Aidan, It’s a Very nice video. So multiphase modeling is applied for phase transition between liquid and vapor refrigerant in a small diameter channel with larger length. But why most of the time solution diverge or temperature doesn’t not change? Thank you very much Please leave a suggestion
@totaloverdose35914 жыл бұрын
Sir, while modelling flow-boiling how do we decide the first cell size in the mesh accounting for different Reynolds no of different phases?
@fluidmechanics1014 жыл бұрын
I would estimate the volume fraction of each phase and then calculate the volume averaged material properties (density, viscosity). You can use these to get an estimate of the Reynolds number, friction coefficient and y+
@totaloverdose35914 жыл бұрын
@@fluidmechanics101 thank you sir!
@mateusalves95584 жыл бұрын
Thank you for the videos, they are pretty cool. Could you please say to what references do you get to study and maybe make your materials?
@fluidmechanics1014 жыл бұрын
Mostly, i use the CFD user manuals from ANSYS, the OpenFOAM source code and textbooks. Often these sources arent very good, so i try and work things out for myself as well 😊 I then try and compile everything together in a really clear form for you guys, as there really isnt a great source of CFD information out there. Thats what im trying to make 😄
@mateusalves95584 жыл бұрын
@@fluidmechanics101 Thank you for your reply, I asked that becausa I felt the same think as you said and I wanted to confirme. I am doing my course conclusion work and I would like to have some lectures to put on the reference and explain all the things that I have done in my research (that is to develop a tool using OpenFOAM to predict the resistance curve for a ship of the Serie 60 merchant ships) . If you could help in some way with that I would be very thankful, and thank you for your help and your good videos!
@sonyjasonallccarimamunico19904 жыл бұрын
Hi bro, could you recommend me a book or bibliography to have a better understanding of this and multiphase flow equations?
@belfodilfarid45154 жыл бұрын
Which apraoch we should adopt for spray cooling impinging hot flat plate? thanks guys!
@fluidmechanics1014 жыл бұрын
A mixture model would probably be best, or you could use Lagrangian particle tracks 👍
@belfodilfarid45154 жыл бұрын
@@fluidmechanics101 THANKS SO MUCH
@tubaisaha32222 жыл бұрын
Hi Aidan, thanks for uploading such an informative video on Multiphase modelling. I have something to ask, i.e is DPM also pronounced as mixture model?
@matiasbarron9495 жыл бұрын
Thanks !
@fluidmechanics1015 жыл бұрын
Glad you liked it 😄
@europa32333 жыл бұрын
If I want to simulate LNG dispersion which would u recommend?
@fluidmechanics1013 жыл бұрын
Hmmm depends on the morphology of the gas bubbles in the fluid. Are they dispersed or continuous. Is there a free surface or do you have slug flow?
@europa32333 жыл бұрын
@@fluidmechanics101 dispersion, just trying to recreate falcon series tests
@ProjectPhysX5 жыл бұрын
Thank you, found the talk very useful! I'm currently implementing VOF for free surface LBM (see my YT channel) and the hardest part is surface curvature calculation. A talk about this would be very appreciated!
@fluidmechanics1015 жыл бұрын
Will see what i can do! This sounds like quite a challenging problem .... 😅
@nikhilnick88865 жыл бұрын
Found useful🙂 Thks
@fluidmechanics1015 жыл бұрын
Great! Glad you found it useful Nikhil
@shahan35962 жыл бұрын
Hey Aidan, how should the interaction or water-steam or water-vapor be treated? is it dispersed-continuous or continuous-continuous interaction?
@fluidmechanics1012 жыл бұрын
I haven't done boiling calcs myself. I am guessing that it depends on the boiling regime? Do you have nucleate boiling?
@shahan35962 жыл бұрын
@@fluidmechanics101 yes. Nucleate boiling
@Rihan_pls4 жыл бұрын
Nice video👌👌
@naidrenalinadventuresn.a16844 жыл бұрын
Hi Adrian. WHat do you use in creating your nice looking CFD lecture notes on patreon?
@fluidmechanics1014 жыл бұрын
I use latex with the beamer package. If you look through the patreon posts i have put up the template that i use, so you can use it yourself if you like 👍
@manusego3 жыл бұрын
Very good video, teacher.👏👏👏. Could I know the software that you use to draw the figures in the presentation? They are excellent! Lot of thanks in advance💞
@fluidmechanics1013 жыл бұрын
Yep, they are all made using inkscape. I put together a quick course to show you how do it if you are interested? (Link is in the video description)
@manusego3 жыл бұрын
@@fluidmechanics101 Thank you very much teacher. I will learn Inkscape from the video link. I have just joined the udemy course. You are the BEST💞👏💞👏💞👏💞
@lizarettflavour5 жыл бұрын
👍👍👍 thank you!
@fluidmechanics1015 жыл бұрын
😄 No problem, glad you found it useful!
@lizarettflavour5 жыл бұрын
@@fluidmechanics101 it is! it's very useful 🌞
@joseffreebird23723 жыл бұрын
Please I need Help how to handle with spray cooling impinging hot flat wall.
@michelletramper30253 жыл бұрын
Hi! Thanks for another wonderful video. I was wondering, is there a way to know how much governing equations I'm solving in total? If you e.g. have three phases, but they are coupled via drag / the sum of the volume fractions is one. And only considering mass and momentum (no energy and turbulence). I don't quite understand how fluent solves/couples the equations, and thus how many equations you're eventually solving. Cheers! Michelle
@fluidmechanics1013 жыл бұрын
You could always just check the residuals that fluent writes out? Fluent will write the residuals for every governing equation you are solving, so this is a quick way to check. For example: pressure x-mom y-mom z-mom volf-1 volf-2 would give 6 governing equations? (3 momentum, 1 pressure, 2 volume fractions) which is what I would expect for 3 species
@michelletramper30253 жыл бұрын
@@fluidmechanics101 thank you!!
@SatishNatarajan2 жыл бұрын
Why is the mass transfer term 'sink' for the liquid water In case of evaporation?
@fluidmechanics1012 жыл бұрын
The liquid water phase loses mass, while the gaseous vapour phase gains mass. So the source term is negative for the liquid phase and positive for the vapour phase. Of course if you have condensation, it is the other way around 👍
@SatishNatarajan2 жыл бұрын
@@fluidmechanics101 Thanks a lot, Dr. Wimshurst. Now it's clear to me.
@yi_mix52243 жыл бұрын
Can you do an introduction of the interface capturing discretization scheme? Many thanks in advance!!!
@arminsh93153 жыл бұрын
Thanks a zillion for your awesome videos. Honestly, my CFD knowledge has improved significantly since I started watching your great informative videos. Anyway, there was something that I couldn't understand very well at the penultimate slide which was about Ap/V of the continuos-continuous phases. I was wondering if you could explain it to me how this ratio is equal to the gradient of the volume fraction.
@fluidmechanics1013 жыл бұрын
I can't remember exactly why this is the case. It is stated in many of the CFD manuals without much explanation. I know that's not very helpful but it's the best I've got at the moment 😅
@arminsh93153 жыл бұрын
@@fluidmechanics101 Thank you Aiden. By the way, may I ask you to introduce a source from which I can learn better the discretisation methods for the convection term of the volume fraction equation of the continuous-continuous method? Or if it's possible, could you please make video on them?
@diksharaut62413 жыл бұрын
It was a great video, I got this project called modeling of liquid-gas flows using VOF-DBM method and this surely was helpful, so I will be needing more guidance, could you help me out with that?
@amirhosseinparvin21194 жыл бұрын
Hi Aidan, Thank you it was really helpful, I have a question. in the solution of volume fraction equations for three-phase (sharp interface), how it avoids overlapping the interfaces? in references the explanations about the interface tracking are all about the two phases condition.
@fluidmechanics1014 жыл бұрын
Good question. Let me have a think about that one!
@oneuniverse66795 жыл бұрын
can we model heat pipe wick structure in ansys fluent?
@fluidmechanics1015 жыл бұрын
Sorry dude, im not sure what you mean. Can you provide a link/example?
@skhossenali56542 жыл бұрын
Sir, can you make another video on the algorithm/procedure to solve these complex equations.like I didn’t get how do we get pressure equation and solve it.
@fluidmechanics1012 жыл бұрын
Yes, I am working on this at the moment. It is quite confusing and the pressure correction equation is definitely one of the hardest parts to understand in CFD
@skhossenali56542 жыл бұрын
@@fluidmechanics101 Sir, if possible can you suggest some references untill you upload the video prefereably for the compressible cases. Thanks.
@fluidmechanics1012 жыл бұрын
The book by Ferziger and Peric (computational methods for fluid dynamics) is pretty good. I would start there 👍
@vikashkumar-cr7ee4 жыл бұрын
Could you plz upload more lecture on Multiphase modelling
@sylwiawrzesien5183 жыл бұрын
@ZaterranSyzoth11 ай бұрын
Slide number 6: Check your units, they are not consistent in the equation!!!