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trying to understand the boundary condition "oscillatingFixedValue" |
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May 29, 2015, 00:20 |
trying to understand the boundary condition "oscillatingFixedValue"
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#1 |
Senior Member
Huynh Phong Thanh
Join Date: Aug 2013
Location: Ho Chi Minh City
Posts: 105
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Hi foamer,
I would like to setup oscillatingFixedValue with the equation u = 2.7 + 16(sėn2pit/16) I saw the guide at https://openfoamwiki.net/index.php/M...tingFixedValue if I understand exactly, the inlet velocity will: inlet { type oscillatingFixedValue; value uniform 0; // Initialization value refValue uniform (1 0 0); // Reference value for oscillation offset (1.7 0 0); // Oscillation mean value offset amplitude constant 16; // Amplitude of oscillation frequency constant 0.0625; // frequency } Following the equation, I set offset 1.7 will it plus 1 to 2.7? Thank you Thanh Last edited by hiuluom; May 29, 2015 at 12:09. |
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May 29, 2015, 23:38 |
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#2 |
Senior Member
Huynh Phong Thanh
Join Date: Aug 2013
Location: Ho Chi Minh City
Posts: 105
Rep Power: 12 |
I ran inlet BCs above no problem with Tjunction tutorial. I only confuse about the "refValue" and "offset":
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May 30, 2015, 08:05 |
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#3 |
Senior Member
Huynh Phong Thanh
Join Date: Aug 2013
Location: Ho Chi Minh City
Posts: 105
Rep Power: 12 |
Does anyone can help me explain my question?
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May 30, 2015, 08:34 |
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#4 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
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Greetings Thanh,
I don't understand what's the doubt you're having? I've checked the source code and the expression on the wiki seems to be correct: Therefore, it's a basic mathematical expression. If "refV" is set to 1.0, then you're left with this: The rest is simple math, namely for having a final offset of 2.7 (with refV =1), you need the "offset" parameter to be 1.7. And when in doubt, don't be afraid to simulate with OpenFOAM and test things yourself. If you create a simple test case, you can easily test if this works as intended or not. Specifically, if you want to be able to prove that it works as intended, you should in fact do that simple test case first! Best regards, Bruno
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May 30, 2015, 12:56 |
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#5 |
Senior Member
Huynh Phong Thanh
Join Date: Aug 2013
Location: Ho Chi Minh City
Posts: 105
Rep Power: 12 |
Hi Bruno,
Your explaination is very clearly at refVal. I have simulated with Tjuntion tutorial with inlet Bcs above. I only confuse that offset should be 2.7 or 1.7. Thank you so much. |
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July 25, 2015, 12:45 |
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#6 |
Senior Member
Huynh Phong Thanh
Join Date: Aug 2013
Location: Ho Chi Minh City
Posts: 105
Rep Power: 12 |
I add more answer the oscillating. If the equation don't have offset:
Code:
U = 16(sėn2pit/16) (m/s) Code:
U = 1 + 16(sėn2pit/16) (m/s) Code:
16 +16(sėn2pit/16) - 16 = 16(sėn2pit/16) |
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July 25, 2015, 13:12 |
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#7 |
Senior Member
anonymous
Join Date: Aug 2014
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Use groovyBC for the BC, it is easier
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August 17, 2015, 03:58 |
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#8 |
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Stephanie
Join Date: Feb 2015
Location: Magdeburg, Germany
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Hello everyone,
I am not sure if this is the right place to asked, but maybe one of you might help me. In my case I have an airfoil in a channel. Now my task is to implement a condition for an oscillating stream. I thought I might use oscillatingFixedValue for it. I tried for my inlet condition under 0/U: type oscillatingFixedValue; refValue (1.56 0 0); //my verlocity amplitude 0.05; offset 0; frequency 0.8; value uniform (0 0 0) When I have a look in to the vectorplot I can't see any movement of the vectors, so I think it doesn't work. Have anyone a hint for me how I can fix my problem? I would be very gratefule! Thank you and best regards, Stephie |
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August 17, 2015, 08:17 |
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#9 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,975
Blog Entries: 45
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Quick answer: Sorry, but you're being too vague in order to give an accurate answer. The best I can say is that you should compare with the plot of the oscillation you're requesting: Plot[0. + 1.56 (1. + 0.05 Sin[2*pi*0.8* t]), {t, 0, 10}]
And/or that perhaps you're not familiar enough yet with the time controls in ParaView? Beyond this, I suggest:
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