[CFD] Non-Newtonian Flows in CFD

[@elliotenriquecortesreyna7115]

Thank you, this is what I call democratization of the knowlage.

[@TahsinEngin-Akademi]

It would be great if you write a stand alone introductory textbook on CFD. You have a very good style.

[@fluidmechanics101]

Yes, thanks for the great suggestion! I am actually starting to put together an introductory textbook for CFD right now 😄 if you want to have a look, you can have a look at my ‘CFD fundamentals course’ on my website: www.fluidmechanics101.com/pages/shop.html Have a look and let me know what you think! I am definitely looking for feedback for how I can improve it in future

[@soyagricola7526]

You definitely have to write a cfd book

[@killua9369]

This guy is amazing! Now you are the reference for many students in CFD :)

[@Thescavenger4]

Great job, keep on so more people will understand and like fluid mechanics/CFD !

[@FreeMostImportant]

Very great course!

[@sergeianpilov5222]

Oh, purrfect! Thank you so much - I was realizing that I miss basic knowledge about non-Newtonian flows and not thankx to your lecture - I have a good basis to start with. PS 1.3k subscribers - great progress :> I've sent links to your videos to my colleagues in Germany - should help them a lot.

[@fluidmechanics101]

Fantastic, thanks Sergey! Its great to see the channel growing and everyone getting involved 😄

[@ibragim_on]

Учу по вашим видео английский и CFD!

[@ignacioholert6486]

Excelente contenido! Muchas gracias por compartirlo!

[@Gamhi0313]

I really appreciate this man

[@shriramkrishna6122]

Thank you fort this awesome video. COuld you also shed some light on typical ways of visco elastic flows in a CFD context? Some references would be really helpful.

[@MrMixlist]

Discovered your channel about a week ago and already watched all your videos! Your way of explain and introduce these complex topics is awesome. Now that you have presented an example of two phase flow (water and sludge), it would be cool to have some introduction about methods to deal with these kind a problem, like VOF and any other (trying to implement VOF on some 2D code right now hehe). Keep it up mam, you're awesome!! Cheers from Brazil!!

[@fluidmechanics101]

Fantastic! Thanks for the support Pedro 😊 yes, i am definitely planning on doing a VOF video soon. The focus will be on the interface sharpening algorithms, as these seem to be pretty tricky to get right. Good luck with your 2D code and thanks again!

[@mtg_ishtu3195]

Great job man!

[@mtg_ishtu3195]

Nice

[@mohammadamereh7193]

Thank you for your brilliant courses. Just to remined the dot above the omega in equation 5 is missed. Thanks.

[@HeitorvitorC]

Aidan, you are amazing. I am learning a lot with your videos. Might I ask you if you could maybe talk about the Volume of Fluid Method and its differences when dealing with interface tracking (differences from the level-set method and other techniques)? I am having a hard time finding good content about those subjects, and I believe you might have good things to say about it. Cheers!

[@fluidmechanics101]

Yep! This is one of my upcoming videos 😄

[@muratcan4624]

Can you please suggest a sourcebook to see how to discrete the non-Newtonian rheology equation (Hershel Bulkaky model) to seek apparent viscosity?

[@venkatkrisshna]

Great video. Could you explain why there is a 1/2 term in equation 7?

[@AshokKBarik]

I think, matrix inner product will have component A13B13 instead of A13C13.

[@martinschmidt8608]

Hello Aidan, First of all I wanna thank you for this really nice overview of how to handle non-newtonian fluids in CFD. I am trying to model fresh concrete as a fluid with herschel-bulkley behaviour in ansys fluent. I have experimental data (the dynamic viscosity and the yield stress) to implement into the cfd code. The Herschel-Bulkley has four Parameters that Need to be defined. I was wondering if I have for example in reality a yield stress of 400 Pa and a dynamic viscosity of 20 Pas how to implement them correctly. So n should be equal to 1 in order to have a Bingham fluid. But how do I define the Consistency factor? Best regards Martin

[@fluidmechanics101]

Hi Martin, for a bingham plastic n=1 gives a linear relationship. The consistency index sets the gradient of this straight line. You will need to do a curve fit to your experimental data to get the gradient 👍

[@martinschmidt8608]

@@fluidmechanics101 So actually the Consistency index in ansys fluent is the dynamic viscosity from the experimental data? I tried to take my strain rate at different times from the solution plot and multiplied it by the molecular viscosity. Because as a result I can have a function of the shear stress over the shear rate? And it should be the same as my original experimental data?

[@Ideenschmiede]

Do you get the values for K and n from fitting experimental data?

[@fluidmechanics101]

Yes!

[@asharmd2001]

I have a question, how do we calculate Time step size and number of time steps required for a particular problem? Is there any equation? Or is it random until we see fully developed flow?

[@fluidmechanics101]

As a minimum, you want to choose time steps so that the solution is stable. This often requires a courant number less than 1. In addition to this you would like your time step to be sufficiently small to resolve any unsteady physics that you are simulating (vortex shedding for example). Finally you want your time step to be large enough that your simulation doesnt take weeks to run ... so play around and see what works 😊

[@arminkashani5695]

Dear Aidan, Thank you for the helpful video. It seems to me there is an error in Equation 10; the velocity gradient tensor (i.e. grad{U}) must be replaced with 2*E where E is the strain-rate tensor defined as E = 0.5*(grad{U}+transpose(grad{U})). Please correct me if I am wrong. Regards, Armin

[@ЕгорЧуйков-н8л]

Aiden, thank you for the video. It is very informative! After watching a video a question came up to my mind? If the power law with the n=1 describes newtonian fluid, why one usually applies newtonian rheological model for newtonian fluid (water) in CFD code but not power law? Is it because newtonian model for water is easier to implement in a CFD code, than a power law? Thank you in advance.

[@fluidmechanics101]

Yep! 100% correct. Non-Newtonian fluids also tend to be quite unusual, as the majority of CFD always seems to involve air and water .... After all CFD of toothpaste and custard only have a few applications 🙃

[@ЕгорЧуйков-н8л]

Thank you very much, Aiden!