|
[Sponsors] |
[swak4Foam] Difference between snGrad(U) using swakExpression and wallgradU utility ? |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
December 16, 2014, 23:52 |
Difference between snGrad(U) using swakExpression and wallgradU utility ?
|
#1 |
Member
Daniel
Join Date: Jun 2014
Posts: 60
Rep Power: 12 |
Hello,
I am doing an LES of pipe flow. The streamwise direction is the z-direction. In my controlDict I enter the following "swakExpression" to keep track of my wall shear stress: Code:
wallShear { type swakExpression; valueType patch; patchName Side; accumulations ( average ); expression "nu*1.16*snGrad(U)"; verbose true; } Code:
Time 1.15 (0.00158395 -0.00195003 -0.309623) 1.15001 (0.0015569 -0.0018457 -0.31036) 1.15002 (0.00154682 -0.00179581 -0.310094) 1.15002 (0.0015546 -0.00176741 -0.30988) 1.15003 (0.0015752 -0.00177392 -0.309709) 1.15003 (0.00154428 -0.00172741 -0.309567) 1.15004 (0.00152869 -0.00170179 -0.309448) 1.15004 (0.00154396 -0.00171494 -0.309346) 1.15005 (0.00153824 -0.00171052 -0.309258) 1.15005 (0.00153934 -0.00171405 -0.309179) 1.15006 (0.00153327 -0.00170792 -0.30911) 1.15006 (0.00152485 -0.00169658 -0.309047) 1.15007 (0.00152928 -0.00169544 -0.308991) 1.15007 (0.00153558 -0.00170495 -0.30894) 1.15008 (0.00153235 -0.00170306 -0.308893) 1.15008 (0.00153008 -0.00169775 -0.308849) 1.15009 (0.00154298 -0.00171269 -0.30881) 1.15009 (0.00154351 -0.00171235 -0.308773) 1.1501 (0.00153823 -0.00170273 -0.308739) 1.1501 (0.00153198 -0.00169867 -0.308707) 1.15011 (0.00152493 -0.00169242 -0.308677) 1.15011 (0.00153547 -0.00170078 -0.30865) 1.15012 (0.00153531 -0.00170344 -0.308624) 1.15012 (0.00152695 -0.00169185 -0.3086) 1.15013 (0.00152394 -0.00168702 -0.308578) 1.15013 (0.00152902 -0.00170066 -0.308557) 1.15014 (0.00152878 -0.00170005 -0.308537) However when I compute the wall shear stress using the wallShearStressLES utility, the output is as follows: Code:
(0.00922472 -0.00948885 -0.436616) (0.0167652 -0.0139423 -0.497059) (0.027834 -0.0217006 -0.573286) (0.0405144 -0.0274527 -0.648546) (0.0479752 -0.029261 -0.717811) (0.0462766 -0.0244107 -0.7791) (0.0379119 -0.0177215 -0.833495) (0.0251241 -0.010028 -0.885577) (0.0158647 -0.00529415 -0.91607) (-0.00224175 0.000942265 -0.846752) (-0.0139847 0.0031963 -0.695487) (-0.0133073 0.00202354 -0.506113) (0.00138907 -0.000239348 -0.352859) (-0.00568237 0.000631173 -0.211232) (-0.0198709 0.000730177 -0.169419) (-0.00914825 -0.00054803 -0.258058) (0.0156156 0.00114809 -0.448939) (0.00519621 0.0010823 -0.597595) (0.00899102 0.00132361 -0.671042) (0.0455127 0.0108841 -0.716581) (0.0519395 0.0163323 -0.705576) (0.0428748 0.0163925 -0.644185) (0.0271054 0.0124011 -0.564419) (0.0127216 0.00706786 -0.551247) (0.00512223 0.00361148 -0.617746) (0.00279277 0.00222053 -0.690317) (0.00107463 0.0039771 -0.730843) (0.00670205 0.00761867 -0.778388) (0.0236784 0.0209093 -0.886947) (0.0405041 0.0391589 -1.10094) (0.011279 -0.0109334 -0.438007) (0.0185427 -0.0161606 -0.500274) (0.0297334 -0.0231098 -0.57867) (0.0411742 -0.0284098 -0.654419) (0.0476158 -0.029062 -0.72111) (0.0457186 -0.0245445 -0.77872) (0.0385896 -0.018128 -0.830116) (0.0269545 -0.0107781 -0.883763) (0.0166884 -0.00548417 -0.914038) (-0.00277345 0.00124665 -0.838704) (-0.0161723 0.00388169 -0.685918) (-0.0180005 0.00293102 -0.501037) (3.30381e-05 -1.50492e-05 -0.35243) (-0.00945636 0.00110753 -0.208022) (-0.0277763 0.000992707 -0.172966) (-0.0160046 -0.000732155 -0.269808) (0.00941981 0.000497363 -0.453516) (0.00323716 0.000629968 -0.600543) (0.0046372 0.000533136 -0.683728) Which one is correct and what is the difference between both using snGrad(U) in the first approach and then using the wallShearStressLES utility ?? Please help Last edited by Dan1788; December 17, 2014 at 22:26. |
|
December 17, 2014, 22:26 |
|
#2 |
Member
Daniel
Join Date: Jun 2014
Posts: 60
Rep Power: 12 |
Can anyone help please?
|
|
December 18, 2014, 05:40 |
|
#3 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
Rep Power: 51 |
Quote:
__________________
Note: I don't use "Friend"-feature on this forum out of principle. Ah. And by the way: I'm not on Facebook either. So don't be offended if I don't accept your invitation/friend request |
||
December 21, 2014, 18:21 |
Test between nu*rho*snGrad(U) and nu*rho*wallGrad(U)
|
#4 |
Member
Daniel
Join Date: Jun 2014
Posts: 60
Rep Power: 12 |
Hi Bernhard,
Thanks for your reply. So I did a small test to compare results of the wall Shear stress using snGrad(U) and using wallGrad(U) utility. Following are a couple of lines as output from wallGrad(U) -latestTime Code:
(158.301 -63.0679 9752.01) (-18.023 -183.104 9801.31) (70.9486 -45.88 9654.49) (119.605 -84.467 9432.72) (138.58 -85.0173 9607.43) (138.097 -74.9961 10680.3) (240.245 -116.391 12213) (439.328 -183.63 12451.1) (545.342 -192.911 11860.8) (507.157 -148.288 10896.3) (177.236 -40.1328 9856.27) (-232.057 45.4857 10258.2) Code:
Time 1.15 (0.00158395 -0.00195003 -0.309623) 1.15001 (0.0015569 -0.0018457 -0.31036) 1.15002 (0.00154682 -0.00179581 -0.310094) 1.15002 (0.0015546 -0.00176741 -0.30988) 1.15003 (0.0015752 -0.00177392 -0.309709) 1.15003 (0.00154428 -0.00172741 -0.309567) 1.15004 (0.00152869 -0.00170179 -0.309448) 1.15004 (0.00154396 -0.00171494 -0.309346) 1.15005 (0.00153824 -0.00171052 -0.309258) |
|
January 7, 2015, 16:50 |
|
#5 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
Rep Power: 51 |
Quote:
You are comparing an averaged value at different times (swak) with the raw data at one timestep (wallGrad(U), snGrad(U)) Of course they differ. But if you average the wallShearStressLES-output you should get similar values to swak BTW: if your patch has faces of different sizhes you'll probably want to use weightedAverage as the accumulation
__________________
Note: I don't use "Friend"-feature on this forum out of principle. Ah. And by the way: I'm not on Facebook either. So don't be offended if I don't accept your invitation/friend request |
||
Thread Tools | Search this Thread |
Display Modes | |
|
|