Need CFD help for very un-car-related project

Post here information about your own engineering projects, including but not limited to building your own car or designing a virtual car through CAD.
timbo
108
Joined: Mon Oct 22, 2007 9:14 am

Need CFD help for very un-car-related project

Post by timbo » Mon Dec 17, 2018 9:30 am

OK, so I am physical chemist. Among other thing we study is the vaporization of low-volatile substances.
We have an experimental setup where a substance vaporizes from the very small surface heater and is carried away with the flow of the gas.
On of the important parameters in the calculations of the system is the flow velocity over the surface and the thickness of the stagnant/boundary layer.
There are some more or less good models, but I wanted to maybe try CFD for this problem. The thing is I am totally naive to the CFD.
So can anybody provide any advice on where to start and if there are some free/open-source tools for the CFD?

Just_a_fan
456
Joined: Sun Jan 31, 2010 7:37 pm

Re: Need CFD help for very un-car-related project

Post by Just_a_fan » Mon Dec 17, 2018 10:46 am

NIST's FDS is a free CFD tool that might be useful for this as it's designed to look at heat and smoke transport in fires. Relatively easy to set up each model. It runs as LES but, if you're in a small enough domain and have enough processing power, can be run as DNS. Has a related visualisation tool (Smokeview)

I used it in my Masters degree in FIre Engineering to look at smoke movement in rooms. It can be used in smaller models - I once did a DNS run of a single candle flame. Took a week to run!

https://pages.nist.gov/fds-smv/
Turbo says "Dumpster sounds so much more classy. It's the diamond of the cesspools." oh, and "The Dutch fans are drunk. Maybe"

Greg Locock
164
Joined: Fri Jun 29, 2012 11:48 pm

Re: Need CFD help for very un-car-related project

Post by Greg Locock » Mon Dec 17, 2018 11:24 am

OpenFoam is (or was) open source and free. It is also powerful. But...

(and as Jon Snow said "Everything before the word "but" is horse ---.")

..it is pretty hard for a noob to pick up. i gave up.

There is a lovely 2d code around for a virtual windtunnel, the 2d version of this. http://microcfd.com/3d.htm Absolutely brilliant .

timbo
108
Joined: Mon Oct 22, 2007 9:14 am

Re: Need CFD help for very un-car-related project

Post by timbo » Mon Dec 17, 2018 4:30 pm

Thanks for advice guys!

wpsiatwin
2
Joined: Tue Jun 12, 2018 3:34 pm

Re: Need CFD help for very un-car-related project

Post by wpsiatwin » Mon Dec 17, 2018 10:52 pm

Simscale uses openFoam but with a GUI, you can use it free and if this is for an academic study you can get a free account with more features. I use openFoam so could at least try and help if you go with that too.

timbo
108
Joined: Mon Oct 22, 2007 9:14 am

Re: Need CFD help for very un-car-related project

Post by timbo » Fri Dec 21, 2018 8:17 am

wpsiatwin wrote:
Mon Dec 17, 2018 10:52 pm
Simscale uses openFoam but with a GUI, you can use it free and if this is for an academic study you can get a free account with more features. I use openFoam so could at least try and help if you go with that too.
Thank you!

Vyssion
265
User avatar
Joined: Sun Jun 10, 2012 1:40 pm

Re: Need CFD help for very un-car-related project

Post by Vyssion » Fri Feb 08, 2019 1:19 pm

timbo wrote:
Mon Dec 17, 2018 9:30 am
OK, so I am physical chemist. Among other thing we study is the vaporization of low-volatile substances.
We have an experimental setup where a substance vaporizes from the very small surface heater and is carried away with the flow of the gas.
On of the important parameters in the calculations of the system is the flow velocity over the surface and the thickness of the stagnant/boundary layer.
There are some more or less good models, but I wanted to maybe try CFD for this problem. The thing is I am totally naive to the CFD.
So can anybody provide any advice on where to start and if there are some free/open-source tools for the CFD?
Just to clarify what it is you are looking to simulate, are you looking into blowing across a flat surface to convect away these vapourised chemicals, or is it purely a buoyancy dominated flow?

If you are looking to blow across a flat plate at some given speed, there are equations called the "Blasius Flat Plate" theory which define the exact solution to this problem, which would give you boundary layer thicknesses as well as velocity, skin friction, local Re, etc. all by hand almost.

If the flow is buoyancy dominated, then that is an area I don't have too much experience with, however, I know that OpenFOAM which is Open Source does have a "bouyancyFOAM" type solver which can be used. However, with its super steep learning curve required, I would recomend checking Simscale as mentioned above (which is a sort of "super robust" web based CFD solver based on OpenFOAM code) which you could find many tutorials on and perhaps even copy someone elses public simulation and adapt it to suit your needs.

As always, feel free to ask me for any help if you need it and I'll do my best to do so.
"And here you will stay, Gandalf the Grey, and rest from journeys. For I am Saruman the Wise, Saruman the Ring-maker, Saruman of Many Colours!"

#aerosaruman

timbo
108
Joined: Mon Oct 22, 2007 9:14 am

Re: Need CFD help for very un-car-related project

Post by timbo » Sat Feb 09, 2019 7:27 am

Vyssion wrote:
Fri Feb 08, 2019 1:19 pm
Just to clarify what it is you are looking to simulate, are you looking into blowing across a flat surface to convect away these vapourised chemicals, or is it purely a buoyancy dominated flow?
The former.
Vyssion wrote:
Fri Feb 08, 2019 1:19 pm
If you are looking to blow across a flat plate at some given speed, there are equations called the "Blasius Flat Plate" theory which define the exact solution to this problem, which would give you boundary layer thicknesses as well as velocity, skin friction, local Re, etc. all by hand almost.
I will look, and as I said they kinda work but the problem is that we don't really know the velocity of the flow and the source flow is hitting the plate at some angle.
Vyssion wrote:
Fri Feb 08, 2019 1:19 pm
If the flow is buoyancy dominated, then that is an area I don't have too much experience with, however, I know that OpenFOAM which is Open Source does have a "bouyancyFOAM" type solver which can be used. However, with its super steep learning curve required, I would recomend checking Simscale as mentioned above (which is a sort of "super robust" web based CFD solver based on OpenFOAM code) which you could find many tutorials on and perhaps even copy someone elses public simulation and adapt it to suit your needs.

As always, feel free to ask me for any help if you need it and I'll do my best to do so.
Thank you for advice and the suggestion!
At the moment we are trying to sort of "calibrate" the flow, i.e. tweaking the calculation procedure so that it gives results which are the same for some well-studied compounds, so we stopped investigating CFD for now, but I think at some point we will come back to this.