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Issue with VWT

Altair Forum User

Hi,

I am very new to Virtual Wind Tunnel and Hyperworks in general, been at it for a mere few days, so my issue may be incredibly basic.

My issue; I am using Solidworks to create a car model assembly, importing that into Hypermesh and meshing it. Everything seems to go correctly here. I am then importing the meshed file into Virtual Wind Tunnel, setting everything up and running the simulation. My issues comes with the results; it is 'seeing' my model as a number of dots/mesh elements, not as the whole model (I have attached a screenshot, poor quality but it gets my issue across). This could well be an issue with my model or meshing but I really have no idea. I have tried lots of things over the past couple of days to no avail.

Any help would be greatly appreciated.

Tim

<?xml version="1.0" encoding="UTF-8"?>

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Altair Forum User

Hi,

I am also trying to use VWT and when i scale my geometry in hypermesh from mm to m and export it the meshed geometry is bigger than the wind tunnel. Could anyone help me this query?

ydigit

Tim,

Does your surface mesh generated in HyperMesh have only Tria3 Elements?

Please make sure that there is intersection between car wheels and the wind tunnel floor.

Gudlur, please start a new thread. These are two different issue.

Altair Forum User

In Hypermesh I've been using mixed elements.

I am also making sure there is an intersection between the wheels and the tunnel floor.

I have continued my attempts to get the full car model running correctly in VWT and it is still returning the same/similar results to before; with numerous mesh elements dotted around and not as the whole car.

A few more details, I am first scaling the model in Hypermesh, then 2D automeshing the assembly, then checking the mesh to make sure there are no duplicates or other issues with it. After this I am exporting it to VWT in the .nas format.

Tim

ydigit

Seems it would be tough to proceed without having a look at the model.

Would it be possible for you to upload .HM file as zip (using 'more reply option') ?

Altair Forum User

I have attached two files of a very basic bluff body and undertray, one is simply the model and the other is the same model meshed.

Thank you ydigit for your help

Tim

Unable to find an attachment - read this blog

ydigit

I check the meshed model in HyperMesh. The mesh has intersecting elements. You would need to resolve these intersections before proceeding with VWT.

After exporting the .HM file as .Nas (Fluent) and running in VWT, there is a file named mesh_intersections.nas in run folder. This indicates intersection issues in the surface mesh.

VWT needs intersection between wheel and ground in case of Quad4 elements. If it is a Tria3 only surface mesh, intersection between ground and bluff body is not necessary.

See the thread for more tips and troubleshooting

http://forum.altairhyperworks.com/index.php?/topic/13776-workflow-for-virtual-wind-tunnel/?p=20229

Please check for intersections and penetrations in HyperMesh before exporting the .Nas(Fluent) file.

Altair Forum User

Thank you for your help, I will be sure to check these things out.

Rahul_P1

All,

Please refer to this topic - workflow for VWT

Altair Forum User

Hello,

I got a question on Virtual Wind Tunnel. I have car in the wind tunnel all wheels on floor trying to run a steady state test. Its stuck at 2% does not go pass that. I went through the link http://forum.altairhyperworks.com/index.php?/topic/13896-incomplete-vwt-run-stays-at-2/ and i see in my task manager the memory goes up. But its been more than 3 hours and i still do not results. And it is still at 2%. Any suggestions?

Thanks

Gudlur

ydigit

Could you check the run folder for CAD.DIR, MESHSIM.DIR and vwtAnalysis.MeshSim.txt ? Do these files/folders exist?

Please post your vwtAnalysis.ams file here.

Also check the memory usage of acuMeshSim under the Processes Tab of Task Manager. If it is approaching 80% of your RAM, it means you need to define coarser mesh parameter or move to computer with more RAM.

Altair Forum User

Below i have pasted the code as i could find the way to attach my file. Sorry for the inconvenience.

******************************************************************************************************************************

<?xml version='1.0'?>

<ACUMESH_OBJECT

Name = 'vwtAnalysis'

AcuConsoleVersion = '12.0.310'

AcugsVersion = '20130724'

SimmVersion = '8.0-130430'

AcuhdfVersion = '20120831.0'

UnitFactor = '1.0'

KernelType = 'DISCRETE'

InputFile = 'CAD.DIR/windTunnelWithBody.sdm'

GeomCkSum = '-985102207'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.91084'

MinCurveSizeType = 'ABSOLUTE_VALUE'

MeshGrowthRate = '1.0'

CurvatureAngle = '25.0'

CurvatureMeshSizeFactor = '0.5'

SweepAngle = '20.0'

<ACUMESH_PROCESS

Name = 'vwtAnalysis'

ReducedMeshFlag = 'on'

EnsureInteriorVertices = 'ENSURE_NONE'

ShrinkMixedFlag = 'off'

MeshType = 'ACUMESH_VOL_MESH'

VolOptOptimMeshFlag = 'on'

VolOptSmoothMeshFlag = 'on'

VolOptSmoothMeshLevel = '1'

VolOptModifySurfFlag = 'off'

VolOptStructMeshFlag = 'on'

VolOptUnstructMeshFlag = 'on'

VolOptEnforceMeshFlag = 'off'

SrfOptSnapOnMatchFlag = 'on'

SrfOptSmoothMeshFlag = 'on'

SrfOptSmoothMeshLevel = '3'

SrfOptFaceRotAngLim = '15.0'

SrfOptFixIntFlag = 'on'

SrfOptFixIntLevel = '1'

SrfOptContOnErrorFlag = 'off'

SrfOptProximitySizeLevel = '0'

BoundaryLayerHeightGradationRate = '0.0'

BoundaryLayerMaxLayerDifference = '0'

BoundaryLayer2DHeightGradationRate = '0.0'

BoundaryLayer2DMaxLayerDifference = '0'

BoundaryLayerMinAspectRatioFlag = 'off'

BoundaryLayerMinAspectRatio = '0.9'

BoundaryLayer2DMinAspectRatioFlag = 'off'

BoundaryLayer2DMinAspectRatio = '0.9'

BoundaryLayerExposedRatioFlag = 'off'

BoundaryLayerExposedRatio = '0.2'

BoundaryLayerConformityAngle = '150.0'

MaximumVertices = '0'

MaximumEdges = '0'

MaximumFaces = '0'

MaximumRegions = '0'

<ACUMESH_CUBE_REFINE

Name = 'Zone 1'

BoxCenter = '4.47828,-0.599142,0.5994815'

BoxLengthX = '3.735902'

BoxLengthY = '1.797902'

BoxLengthZ = '1.134233'

BoxXRot = '0.0'

BoxYRot = '0.0'

BoxZRot = '0.0'

MeshSize = '0.0569'

<ACUMESH_CUBE_REFINE

Name = 'Zone 3'

BoxCenter = '4.450615,-0.6854335,0.4006285'

BoxLengthX = '2.846402'

BoxLengthY = '1.442103'

BoxLengthZ = '0.778433'

BoxXRot = '0.0'

BoxYRot = '0.0'

BoxZRot = '0.0'

MeshSize = '1.0'

<ACUMESH_VOLUME

Group = 'Fluid'

GeomSets = '1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

<ACUMESH_VOLUME

Group = 'Solid'

GeomSets = '2'

MeshFlag = 'off'

<ACUMESH_SURFACE

Group = '05_chassis_front'

GeomSets = '6:0:2,6:1:1,67:0:2,67:1:1,68:0:2,68:1:1,69:0:2,69:1:1,70:0:2,70:1:1,71:0:2,71:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '06_chassis_rear'

GeomSets = '7:0:2,7:1:1,72:0:2,72:1:1,73:0:2,73:1:1,74:0:2,74:1:1,75:0:2,75:1:1,76:0:2,76:1:1,77:0:2,77:1:1,78:0:2,78:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '07_side_box'

GeomSets = '8:0:2,8:1:1,79:0:2,79:1:1,80:0:2,80:1:1,81:0:2,81:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '08_channel_air_cooler'

GeomSets = '9:0:2,9:1:1,82:0:2,82:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '09_body'

GeomSets = '10:0:2,10:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '10_undertray'

GeomSets = '14:0:2,14:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '11_undertra_upside'

GeomSets = '16:0:2,16:1:1,84:0:2,84:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '12_undertray_border'

GeomSets = '21:0:2,21:1:1,85:0:2,85:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '13_wheel_front'

GeomSets = '33:0:2,33:1:1,66:0:2,66:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '14_wheel_rear'

GeomSets = '44:0:2,44:1:1,83:0:2,83:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '15_cockpit'

GeomSets = '55:0:2,55:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '16_undertray_cutout'

GeomSets = '58:0:2,58:1:1,86:0:2,86:1:1,87:0:2,87:1:1,88:0:2,88:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = '17_chassis_cutout'

GeomSets = '59:0:2,59:1:1,89:0:2,89:1:1,90:0:2,90:1:1,91:0:2,91:1:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.0569'

MinCurveSizeType = 'ABSOLUTE_VALUE'

CurvatureAngle = '10.0'

CurvatureMeshSizeFactor = '0.25'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = 'Wind_Tunnel_Bottom'

GeomSets = '60:0:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

BoundaryLayerFlag = 'on'

BoundaryLayerSpec = 'type_1'

BoundaryLayerResolve = 'ACUMESH_BLRESOLVE_TOTALHEIGHT'

FirstLayerHeight = '0.000422'

GrowthRate = '1.3'

NumberOfLayers = '3'

BoundaryLayerElemType = 'ACUMESH_BL_TETRAHEDRON'

BoundaryLayerBlendsFlag = 'off'

BoundaryLayerPropagateFlag = 'off'

<ACUMESH_SURFACE

Group = 'Wind_Tunnel_Inlet'

GeomSets = '61:0:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

<ACUMESH_SURFACE

Group = 'Wind_Tunnel_Left'

GeomSets = '62:0:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

<ACUMESH_SURFACE

Group = 'Wind_Tunnel_Outlet'

GeomSets = '63:0:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

<ACUMESH_SURFACE

Group = 'Wind_Tunnel_Right'

GeomSets = '64:0:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

<ACUMESH_SURFACE

Group = 'Wind_Tunnel_Top'

GeomSets = '65:0:1'

MeshSizeType = 'ABSOLUTE_VALUE'

MeshSize = '0.45542'

</ACUMESH_OBJECT>

</ACUMESH>

ydigit

I should have also asked you to post the output of *.MeshSim.txt. Apologies.

*.ams seems to be fine. I suspected some very fine refinement box, but thats not the case.

Please use 'More Reply Options' on forum to upload *MeshSim.txt and .Nas file you used to import in VWT.

As I asked previously, do you see MESHSIM.DIR?

ydigit

acuMeshSim: <SIMM_INFO_MSG>:Number of BL regions created = ########
acuMeshSim: <SIMM_PRG>:Creating volume mesh
acuMeshSim: <SIMM_INFO_MSG>: MeshCubeRefine
acuMeshSim: <SIMM_INFO_MSG>: MeshCubeRefine
acuMeshSim: <SIMM_WRN_MSG>:Circumsphere with <= 0 height
....

acuMeshSim: <SIMM_WRN_MSG>:Zero volume: verts 25486988 25486989 25487020
......

acuMeshSim: Encountered an error in meshsim
acuMeshSim: <SIMM_ERR_MSG>:Code: 60 String: General error
acuMeshSim: <SIMM_PRG>:Volume Meshing
acuMeshSim: Error generating volume mesh
acuMeshSim: Extract volume meshing errors
acuMeshSim: Error Msg : <General error>
acuMeshSim: Error Code: <60>

This is most likely a modeling issue:

- either surface mesh has very small/skewed elements, that are leading to problem with mesh generation

- there is very small gap between wheels and the ground, or probably no gap?

I would have to see the .NAS file in order to comment more on this issue. Would it be possible to upload that?

ydigit

Thanks for sending the model.

As suspected, this is an issue of no intersection between wheel and ground. Position the wheel to have slight penetration with ground and the case works!

Tip added to :

http://forum.altairhyperworks.com/index.php?/topic/13776-workflow-for-virtual-wind-tunnel/?p=20359