Boundary layer thickness calculation

rohit_turbo · February 3, 2016, 02:08

Hello,
I am working on a transonic axial compressor project in CFX.
Need to know if there might be a possibility of directly calculating the boundary layer thickness.?
I tried the function calculator in CFX-post, but it doesn't show anything related to boundary layer.
Please help me sort this!!
Thanks,
Rohit

ghorrocks · February 3, 2016, 05:44

http://lmgtfy.com/?q=boundary+layer+thickness

rohit_turbo · February 4, 2016, 03:30

Wow dude!! you are amazing!!..
Admin!!! ban people like this!!
He is wasting your websites reputation!!
I was asking about direct calculation of boundary layer and not some formulae that need to be googled dude!!

ghorrocks · February 4, 2016, 04:05

The link gives a heap of different methods to calculate boundary layer thickness. That answers your question doesn't it?

If I have not answered your question then you will need to explain your question better.

Opaque · February 4, 2016, 12:38

If you want FREE help, you can start with two basic steps:
- Explain your questions, or goals better
- RESPECT those in the forum that will be helping you..

For your education, Glenn has been the most cooperative member on this specific forum since its creation and he has carried the torch of helping those in need on CFX issues like nobody else.

Hope the above help you present yourself in a better light next time around. Best of luck.

rohit_turbo · February 4, 2016, 12:57

hello,
Mr.Opaque,
so let me take lessons from you regarding how to post a question!
If you are in this particular situation with the same problem and if you seek free help like as you mentioned, how would you want to put better light on your question??
Lets forget about boundary layer now, I look at this as a challenge Mr.Opaque I have followed all the rules that you mention in the forum before posting a thread!
I have mentioned about using cfx post, I have mentioned what I am working on and I have even mentioned that I have tried using the function calculator!!.So now my problem lies where?. I could not find any direct calculator of boundary layer thickness as you do for temperature, pressure the yplus value!!.with a click of a button you are able to find values!!. Now should I even mention that I want to have the boundary laye thickness value with a click of a button!!.. Now, atleast you big flag carriers and torch bearers of this forum, this is no way to answer!! so unprofessional and unethical!! You insult people by saying them to google it!! If my way asking is mannerless or did I ever say that I need compulsorily an answer!!You call yourself torch bearers , but unfortunately you lack quality of one!! I doubt you only have ego and too much self pride on your knowledge!! Anyways I apologize that I asked a question expecting a realistic solution here!! Thanks for letting e know how kool is website and how your torch bearers react to even the silliest questions!!
Good luck to you to Mr.Opaque!!

ghorrocks · February 4, 2016, 16:25

Let's calm down a little here. If my little bit of sarcasm offended you then I apologise.

If your original post is asking can you click a button and get boundary layer thickness - the answer is no, you cannot.

If your original question is asking how do you calculate boundary layer thickness then the link I posted gives many different ways of doing it as it has many definitions. And once you have the equation you want to implement then it is straight forward (usually) to implement it in CFD-Post.

Or is your original question saying you have a boundary layer equation you wish to implement, but you do not know how to implement it?

This is why your question was unclear, I do not know what of these 3 questions you are asking.

rohit_turbo · February 5, 2016, 05:48

Dear Mr. Glenn,
I sincerely apologize for over reacting here. All I am trying to say is that a person should not be judged just by what question he asks!
It is wrong on my part to rant on a petty issue such as this one, but unfortunately Mr. Opaque took it too far and I wanted to make sure that I am not one of your users who posts questions just for fun without any homework.
Mr. Glenn , I am sorry and I was unaware that there were other 3 layers to my question.
But, rest assured that I do respect what the forum does and I hope I have not offended anyone here!
Just one request, Please try asking only one question to the user or atleast you could post a reply that you weren't able to understand, because it is 2 people who are sitting on two different ends of a computer screen, so there are chances that you are bound to misunderstand what the user wants and what the replier is asking of you, may be after that you can judge whether he is really seeking an answer or he is just trying to mock you without any homework!
I know my question brings to light the situation where people who have contributed so much to the forum must be feeling frustrated enough to reply and hence the troll that you uploaded!!
Next time shall keep in mind to write an essay before asking anything!

Thanks and regards,
-Rohit(An ardent CFD lover and fluid dynamics enthusiast!)

ghorrocks · February 5, 2016, 05:58

No problem and no offence taken. So let's get back on topic and move on.

It looks like I did not understand your original question so can you explain your question more clearly?

alinik · February 8, 2016, 13:05

I have struggled with it before and it seems that CFX does not have a BL thickness calculator function and so on. So if you wanna find out the BL thickness, BL displacement thickness, BL momentum thickness and so on you have to actually export velocity profiles along numerous lines perpendicular to your surface at different locations and write a Matlab script to find all those unknowns. It becomes a real pain especially in case the surface has some curvatures.
That is to best of my knowledge. So if you find an easy way, please share it with us and I certainly do welcome it since it makes my job a lot easier.

honcho62 · February 9, 2016, 09:42

One way might be to make a vertical line. Then in the table do an an if loop such that if( u > 0.989 Uex & u < 0.991 Uex, y, 0). It's not pretty and if you have a lot of sample along that line it might find more than one height, so you could average the results. But this should work and you can do it all in CFD Post

February 3, 2016, 02:08	Boundary layer thickness calculation	#1
rohit_turbo New Member Rohit S Iyer Join Date: Oct 2015 Posts: 16 Rep Power: 10	Hello, I am working on a transonic axial compressor project in CFX. Need to know if there might be a possibility of directly calculating the boundary layer thickness.? I tried the function calculator in CFX-post, but it doesn't show anything related to boundary layer. Please help me sort this!! Thanks, Rohit

February 3, 2016, 05:44		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	http://lmgtfy.com/?q=boundary+layer+thickness Opaque and fresty like this.

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February 4, 2016, 03:30		#3
rohit_turbo New Member Rohit S Iyer Join Date: Oct 2015 Posts: 16 Rep Power: 10	Wow dude!! you are amazing!!.. Admin!!! ban people like this!! He is wasting your websites reputation!! I was asking about direct calculation of boundary layer and not some formulae that need to be googled dude!!

February 4, 2016, 04:05		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The link gives a heap of different methods to calculate boundary layer thickness. That answers your question doesn't it? If I have not answered your question then you will need to explain your question better.

February 4, 2016, 12:38		#5
Opaque Senior Member Join Date: Jun 2009 Posts: 1,804 Rep Power: 32	If you want FREE help, you can start with two basic steps: - Explain your questions, or goals better - RESPECT those in the forum that will be helping you.. For your education, Glenn has been the most cooperative member on this specific forum since its creation and he has carried the torch of helping those in need on CFX issues like nobody else. Hope the above help you present yourself in a better light next time around. Best of luck.

February 4, 2016, 12:57		#6
rohit_turbo New Member Rohit S Iyer Join Date: Oct 2015 Posts: 16 Rep Power: 10	hello, Mr.Opaque, so let me take lessons from you regarding how to post a question! If you are in this particular situation with the same problem and if you seek free help like as you mentioned, how would you want to put better light on your question?? Lets forget about boundary layer now, I look at this as a challenge Mr.Opaque I have followed all the rules that you mention in the forum before posting a thread! I have mentioned about using cfx post, I have mentioned what I am working on and I have even mentioned that I have tried using the function calculator!!.So now my problem lies where?. I could not find any direct calculator of boundary layer thickness as you do for temperature, pressure the yplus value!!.with a click of a button you are able to find values!!. Now should I even mention that I want to have the boundary laye thickness value with a click of a button!!.. Now, atleast you big flag carriers and torch bearers of this forum, this is no way to answer!! so unprofessional and unethical!! You insult people by saying them to google it!! If my way asking is mannerless or did I ever say that I need compulsorily an answer!!You call yourself torch bearers , but unfortunately you lack quality of one!! I doubt you only have ego and too much self pride on your knowledge!! Anyways I apologize that I asked a question expecting a realistic solution here!! Thanks for letting e know how kool is website and how your torch bearers react to even the silliest questions!! Good luck to you to Mr.Opaque!!

February 4, 2016, 16:25		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Let's calm down a little here. If my little bit of sarcasm offended you then I apologise. If your original post is asking can you click a button and get boundary layer thickness - the answer is no, you cannot. If your original question is asking how do you calculate boundary layer thickness then the link I posted gives many different ways of doing it as it has many definitions. And once you have the equation you want to implement then it is straight forward (usually) to implement it in CFD-Post. Or is your original question saying you have a boundary layer equation you wish to implement, but you do not know how to implement it? This is why your question was unclear, I do not know what of these 3 questions you are asking.

February 5, 2016, 05:48		#8
rohit_turbo New Member Rohit S Iyer Join Date: Oct 2015 Posts: 16 Rep Power: 10	Dear Mr. Glenn, I sincerely apologize for over reacting here. All I am trying to say is that a person should not be judged just by what question he asks! It is wrong on my part to rant on a petty issue such as this one, but unfortunately Mr. Opaque took it too far and I wanted to make sure that I am not one of your users who posts questions just for fun without any homework. Mr. Glenn , I am sorry and I was unaware that there were other 3 layers to my question. But, rest assured that I do respect what the forum does and I hope I have not offended anyone here! Just one request, Please try asking only one question to the user or atleast you could post a reply that you weren't able to understand, because it is 2 people who are sitting on two different ends of a computer screen, so there are chances that you are bound to misunderstand what the user wants and what the replier is asking of you, may be after that you can judge whether he is really seeking an answer or he is just trying to mock you without any homework! I know my question brings to light the situation where people who have contributed so much to the forum must be feeling frustrated enough to reply and hence the troll that you uploaded!! Next time shall keep in mind to write an essay before asking anything! Thanks and regards, -Rohit(An ardent CFD lover and fluid dynamics enthusiast!)

February 5, 2016, 05:58		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	No problem and no offence taken. So let's get back on topic and move on. It looks like I did not understand your original question so can you explain your question more clearly?

February 8, 2016, 13:05		#10
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 17	I have struggled with it before and it seems that CFX does not have a BL thickness calculator function and so on. So if you wanna find out the BL thickness, BL displacement thickness, BL momentum thickness and so on you have to actually export velocity profiles along numerous lines perpendicular to your surface at different locations and write a Matlab script to find all those unknowns. It becomes a real pain especially in case the surface has some curvatures. That is to best of my knowledge. So if you find an easy way, please share it with us and I certainly do welcome it since it makes my job a lot easier.

February 9, 2016, 09:42		#11
honcho62 Member Join Date: Jan 2016 Posts: 34 Rep Power: 10	One way might be to make a vertical line. Then in the table do an an if loop such that if( u > 0.989 Uex & u < 0.991 Uex, y, 0). It's not pretty and if you have a lot of sample along that line it might find more than one height, so you could average the results. But this should work and you can do it all in CFD Post