# Analysis T106A Cascade boundary condition

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 May 10, 2012, 04:24 Analysis T106A Cascade boundary condition #1 Member   Arun Join Date: Mar 2012 Location: Vellore,TN,India Posts: 39 Rep Power: 6 Hello, I'm doing the T106A cascade analysis for my project. I checked and different sources i didn't find a good solution for the boundary value. I have my value given below. Inlet(is this correct?) V=2.334 (for 1.6*10^5 re) angle of Attack(37.7 deg) x=2.33*cos(37.7) y=2.33*sin(37.7) but the problem is i didn't get the out let pressure value and the angle(do i need to consider angle on outlet pressure?) as i studied the the form it was given "0". i'm doing k and omega sst model And the most worst case is i didn't get any bubble separation still now and the solution is not converging. my friends suggested the form. I hope i'll find some answer from you. thank you.

May 11, 2012, 03:49
#2
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Sijal
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I have done this project. And made calculations for different Re and found boundary conditions. I shall scan this page and send it you on forum.

Quote:
 and the most worst case is i didn't get any bubble separation still now and the solution is not converging
Mostly we used the transient solution and used time step of 1e-3 to 1e-05 and you need thousand of iterations to get the transient flow with separation. Or alternatively initialize with different velocity values in the domain to get the unstable solution in few iterations. (solution initialization >>>> Patch)

 May 11, 2012, 04:45 #3 Member   Arun Join Date: Mar 2012 Location: Vellore,TN,India Posts: 39 Rep Power: 6 thank you for the reply, i would be pleased if you help me in this. I'll try to change the velocity as you suggested. I read that K-omega sst fails to compute this problem. Is that true but my university asked to do in that.

 May 11, 2012, 04:57 #4 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,314 Blog Entries: 6 Rep Power: 43 You need SST transition model (we used this successfully). Later on we used kl-kw-w model with good results. Please note that sst transition model works on correlations for three type of transition mechanism such as : bypass, natural and wake induced transition. While the kl-kw-w model works on the physical models with no correlation.

May 17, 2012, 08:57
#5
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Arun
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i completed the solution but i did't get bubble separation and i have reverse flow in face(some numbers) and on pressure out (some numbers)

i have attached you the jpeg files for reference. I can't figure why i have revers flow. I hope that you can help in this.
Attached Images
 final_part1 vectorfull.jpg (60.7 KB, 25 views) final_part2 vector.jpg (59.6 KB, 17 views) final_part2 pressure plot.jpg (64.0 KB, 17 views)

 May 17, 2012, 09:30 #6 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,314 Blog Entries: 6 Rep Power: 43 What is the turbulence intensity and Reynolds number? Extend domain at least 1.5 chords upstream and 2 chords downstream.

 May 17, 2012, 09:55 #7 Member   Arun Join Date: Mar 2012 Location: Vellore,TN,India Posts: 39 Rep Power: 6 Hi Far, I'm new to fluent . I like to know where i need to change it. i think it is in solution method if i'm not correct please let me know. The turbulence intensity is 4% it took the velocity 8.45 m/s (i'm not in lab i need viscosity and density to calculate Reynolds number)

 May 17, 2012, 09:57 #8 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,314 Blog Entries: 6 Rep Power: 43 I am going to attach the cas and dat file, I just ran with transition.

 May 17, 2012, 10:11 #9 Member   Arun Join Date: Mar 2012 Location: Vellore,TN,India Posts: 39 Rep Power: 6 it will be very helpful

May 18, 2012, 07:43
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Arun
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Quote:
 Originally Posted by Far What is the turbulence intensity and Reynolds number? Extend domain at least 1.5 chords upstream and 2 chords downstream.
Hi Far,
I like to know where need to change this values. I running out of time

 May 18, 2012, 07:53 #11 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,314 Blog Entries: 6 Rep Power: 43 For Reynolds number change velocity (or density or viscosity or chord length, but most suitable is velcoity in this case). For turbulence intensity, in velocity inlet panel change method to turbulence intensity and length scale.

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