[Savio Poovathingal]

Hi All,

I am new to SU2 (not new to CFD) and I am trying to setup the classic infinite parallel channel flow problem for the incompressible solver.

I am running into trouble with specifying the inlet boundary conditions. Based on the sample config template file, I think I should be using,

%Incompressible: (inlet marker, NULL, velocity magnitude, flow_direction_x, flow_direction_y, flow_direction_z, ... ) where flow_direction is a unit vector.
MARKER_INLET= ( NONE )

Correspondingly, my command is
MARKER_INLET= ( inlet, NULL, 0.075, 1.0, 0.0, 0.0 )

but I get an error, MARKER_INLET: improper option value for type inlet. I also tried specifying INLET_TYPE = INCOMPRESSIBLE but that didn't help.

Any help would be appreciated.

Thanks,
Savio

[talbring]

Hi Savio,

can you try to put there a 0.0 instead of NULL ?

Tim

[Sprotte]

Hi there,

quick answer so that you can start your simulation:

Set INLET_TYPE= MASS_FLOW and specify a number at NONE's place, e.g.
MARKER_INLET= ( inlet, 1.0, 0.075, 1.0, 0.0, 0.0 ). It will be ignored.

(In compressible mass flow BC, the second number would be the prescribed density).

What the incompressible BC routine essentially does is weakly prescribing the velocities. So it cares only for them and the commands above are at least sufficient to tell them.

There might be other ways to tell SU2 what the inlet BC for incompressible flow are, though. I don't know by heart.
This might be a bit puzzling sometimes but it's all inherited from the compressible origin.

Regards, Ole


EDIT: Never leave the 'Post Reply'-Tab open for more than ten minutes. talbring will be quicker then. *thumbsup*

[Savio Poovathingal]

Hi Tim and Ole,

Your suggestion worked and I am getting a parabolic profile for a fully developed flow, but it appears that the parabolic profile depends on the velocity of the inlet boundary condition. I am not sure why this would be the case. Since the incompressible solver uses artificial compressibility, it needs 2 inlets b.c.'s but the steady state solution should not be affected.

Based on the Re number, the entrance length should be ~0.49m, and my pipe is 1m long.

I have attached my config file and mesh file, if that helps.

[talbring]

Hi savio,

first of all the mesh is probably way too coarse to get any meaningful results.

Second, in your config file the FREESTREAM_VELOCITY is 50 times smaller then the actual inlet velocity. Since the solution is initialized with the freestream velocity, this initial guess is quite bad, hence you get a very poor convergence.

That's probably the reason why you see a difference in the velocity when you change the freestream velocity.

Tim

[musa19]

Error in "void CConfig::SetPostprocessing(short unsigned int, short unsigned int, short unsigned int)":
-------------------------------------------------------------------------
Inlet types for incompressible problem improperly specified.
Use INC_INLET_TYPE= VELOCITY_INLET or PRESSURE_INLET.
Must list a type for each inlet marker, including duplicates, e.g.,
INC_INLET_TYPE= VELOCITY_INLET VELOCITY_INLET PRESSURE_INLET
------------------------------ Error Exit -------------------------------

[akoodlyr]

Hi,

So there are a few of issues in the cfg file. Firstly, the inlet type is defined using INC_INLET_TYPE and not just INLET_TYPE as it is specified in your file. Also, it looks like you have not specified the outlet type in your cfg file. Can you add the line INC_OUTLET_TYPE=PRESSURE_OUTLET (assuming that is a pressure outlet). Finally, the arguements for the inlet boundary defintion are

(name of the marker, temperature, Vel magnitude, flow_directions_x,y and z).

I think you are specifying the actual velocity components instead of flow directions. Can you use a definition like

(inlet, 0.0, 52.1572, cos(10), sin(10), 0)

instead? Note that you should write the actual values of cos(10) and sin(10). Let me know if this works.

Cheers,
Akshay

[musa19]

Thank you very much for your precious time. I am getting following error again after modifying accordingly;

Error in "short unsigned int CConfig::GetMarker_CfgFile_TagBound(std::__cxx11:: string)":
-------------------------------------------------------------------------
The configuration file doesn't have any definition for marker inlet
------------------------------ Error Exit -------------------------------

IN CASE I USE COS(10) AND SIN (10) INSTEAD OF VALUES, I GET ERROR;

ARKER_INLET: must have a number of entries divisible by 6

------------------------------ Error Exit -------------------------------


FILES ARE ATTACHED.
THANKS AGAIN.

[akoodlyr]

Hi,


It looks like your mesh does not have any boundary called inlet. You have to specify the name of the inlet marker that you defined in the mesh file for the first entry in inlet marker definition. Can you share the .su2 file?



Re your second error, you should not write cos(10) or any such expression and instead specify the unit vector along the velocity direction.



Cheers.

[musa19]

Thank you,
I have created my mesh using GMSH With all boundary markers including inlet. I am trying to attach the file but itz bigger than the allowed size. Here is my inlet marker of mesh file:

NMARK= 4
MARKER_TAG= inlet
MARKER_ELEMS= 399
3 201 1398
3 1398 1399
3 1399 1400
3 1400 1401
3 1401 1402
3 1402 1403
3 1403 1404
3 1404 1405
3 1405 1406
3 1406 1407
3 1407 1408
3 1408 1409
3 1409 1410
3 1410 1411
3 1411 1412
3 1412 1413
3 1413 1414
3 1414 1415
3 1415 1416
3 1416 1417
3 1417 1418
3 1418 1419
3 1419 1420
3 1420 1421
3 1421 1422
3 1422 1423
3 1423 1424
3 1424 1425
3 1425 1426
3 1426 1427
3 1427 1428
3 1428 1429
3 1429 1430
3 1430 1431
3 1431 1432
3 1432 1433
3 1433 1434
3 1434 1435
3 1435 1436
3 1436 1437
3 1437 1438
3 1438 1439
3 1439 1440
3 1440 1441
3 1441 1442
3 1442 1443
3 1443 1444
3 1444 1445
3 1445 1446
3 1446 1447
3 1447 1448
3 1448 1449
3 1449 1450
3 1450 1451
3 1451 1452
3 1452 1453
3 1453 1454
3 1454 1455
3 1455 1456
3 1456 1457
3 1457 1458
3 1458 1459
3 1459 1460
3 1460 1461
3 1461 1462
3 1462 1463
3 1463 1464
3 1464 1465
3 1465 1466
3 1466 1467
3 1467 1468
3 1468 1469
3 1469 1470
3 1470 1471
3 1471 1472
3 1472 1473
3 1473 1474
3 1474 1475
3 1475 1476
3 1476 1477
3 1477 1478
3 1478 1479
3 1479 1480
3 1480 1481
3 1481 1482
3 1482 1483
3 1483 1484
3 1484 1485
3 1485 1486
3 1486 1487
3 1487 1488
3 1488 1489
3 1489 1490
3 1490 1491
3 1491 1492
3 1492 1493
3 1493 1494
3 1494 1495
3 1495 1496
3 1496 1497
3 1497 1498
3 1498 1499
3 1499 1500
3 1500 1501
3 1501 1502
3 1502 1503
3 1503 1504
3 1504 1505
3 1505 1506
3 1506 1507
3 1507 1508
3 1508 1509
3 1509 1510
3 1510 1511
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3 1518 1519
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3 1599 1600
3 1600 1601
3 1601 1602
3 1602 1603
3 1603 1604
3 1604 1605
3 1605 1606
3 1606 1607
3 1607 1608
3 1608 1609
3 1609 1610
3 1610 1611
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3 1649 1650
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3 1684 1685
3 1685 1686
3 1686 1687
3 1687 1688
3 1688 1689
3 1689 1690
3 1690 1691
3 1691 1692
3 1692 1693
3 1693 1694
3 1694 1695
3 1695 1696
3 1696 1697
3 1697 1698
3 1698 1699
3 1699 1700
3 1700 1701
3 1701 1702
3 1702 1703
3 1703 1704
3 1704 1705
3 1705 1706
3 1706 1707
3 1707 1708
3 1708 1709
3 1709 1710
3 1710 1711
3 1711 1712
3 1712 1713
3 1713 1714
3 1714 1715
3 1715 1716
3 1716 1717
3 1717 1718
3 1718 1719
3 1719 1720
3 1720 1721
3 1721 1722
3 1722 1723
3 1723 1724
3 1724 1725
3 1725 1726
3 1726 1727
3 1727 1728
3 1728 1729
3 1729 1730
3 1730 1731
3 1731 1732
3 1732 1733
3 1733 1734
3 1734 1735
3 1735 1736
3 1736 1737
3 1737 1738
3 1738 1739
3 1739 1740
3 1740 1741
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3 1742 1743
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3 1744 1745
3 1745 1746
3 1746 1747
3 1747 1748
3 1748 1749
3 1749 1750
3 1750 1751
3 1751 1752
3 1752 1753
3 1753 1754
3 1754 1755
3 1755 1756
3 1756 1757
3 1757 1758
3 1758 1759
3 1759 1760
3 1760 1761
3 1761 1762
3 1762 1763
3 1763 1764
3 1764 1765
3 1765 1766
3 1766 1767
3 1767 1768
3 1768 1769
3 1769 1770
3 1770 1771
3 1771 1772
3 1772 1773
3 1773 1774
3 1774 1775
3 1775 1776
3 1776 1777
3 1777 1778
3 1778 1779
3 1779 1780
3 1780 1781
3 1781 1782
3 1782 1783
3 1783 1784
3 1784 1785
3 1785 1786
3 1786 1787
3 1787 1788
3 1788 1789
3 1789 1790
3 1790 1791
3 1791 1792
3 1792 1793
3 1793 1794
3 1794 1795
3 1795 200
MARKER_TAG= outlet
MARKER_ELEMS= 399
3 199 602
3 602 603
3 603 604
3 604 605
3 605 606
3 606 607 etc

[akoodlyr]

Hi,



I see the problem now, your boundary condition is called 'inlet' and in your cfg file you write 'Inlet'. C++ is case sensitive, so you should change the cfg file to read


MARKER_INLET = (inlet, 0.0, 52.1572, 0.98480775301, 0.17364817766, 0.0)


Cheers,
Akshay