Flow Simulation Trials - Sites.Udel.Edu · Flow Simulation Trials Example 1: ... How to address the...

Ewald Fauster 1/34 05/06/15

FlowSimulationTrials

Example1:RectangularFlatPlate,SinglePointInjection

Simulationdetails Type of process: RTM

Geometry: flat rectangular panel, 100x200mm² (BxH)

Injection gate: corner node

Settingupthepartgeometry Tool: gmsh, version 2.8.5

Set up overall geometry with basic geometric elements (menu “Add ‐ Point, Straight Line”):

Add surface to the geometry (menu “Add – Plane Surface”)


Meshingthepart Tool: gmsh, version 2.8.5

Set meshing size (menu “Tools – Options”, select “Mesh”, tab “General”):

Create 2D mesh (menu „Mesh – 2D“):


Datatransfer Tool: LIMS, version 5.0.7, command line

Commands:

o SETINTYPE “GMSH”

o READ

Choose .msh‐file exported through gmsh

o SETOUTTYPE “DMP”

o WRITE

Choose filename of .dmp‐file to export

Runningtheflowsimulation Tool: LIMS, version 5.0.7, GUI

Set fluid viscosity (menu “Global – Set Viscosity”):

Set permeability (menu “File – Options”, tab “Default Values” ):

Set injection gate (menu “Node – Set Gate”) :


Specify injection type and quantitative value:

Run simulation (menu “File – Run Simulation”) and analyze filling time characteristics:


Meeting1‐QuestionsandAnswers:

QuestionsonSoftwareTools: Gmsh:

o . What are physical groups used for?

Physical groups are regions of identical physical properties,

e.g. fiber volume content, permeability values

Properties could be but are not directly transferred from GMSH to LIMS!

o . What is the difference between elementary entities and physical groups?

Raw “dummy” geometric elements vs. regions with physical properties

o . What about the mesh types?

Work with standard triangular meshing, eventually refine by splitting

o . What about the meshing options?

Functionality unclear!

2D elements should work

3D elements (“bricks”) rather not

LIMS command line:

o What is the effect of using “SETINTYPE”

“Open File Dialog” is not adapting?

o What is the effect of using “SETOUTTYPE”

“Open File Dialog” is not adapting?

LIMS GUI:

o . Opening files seems to be restricted to root directories, e.g. “C:\”, “D:\” ?

Work with “Favorites”

o . Simulation display speed seems to be affected by mouse activity?

It is as it is!


QuestionsonSimulationExamples: How to address the tutorial example (flat RTM plate with quarter circle injection region) in

terms of:

o . meshing with gmsh – plate and fluid injection region?

(a) work with a single quadratic region, or

(b) add two additional points and define a separate quarter‐circular region

injection region will be represented more closely

o . setting the injection gate in the quarter‐circular region?

(a) select a couple of points next to one corner

zhis might be a bit imprecise!

(b)work with two regions and specify particular properties

o . 2D or 3D?

Work with 2D geometry unless 3D is really needed due to geometry issues

or varying material properties

How to address the transverse permeability characterization cell simulation published by

Scholz et al.: “Measurement of transverse permeability using gaseous and liquid flow”.

o Geometry?

o Meshing?

o Material Properties?


Example2:QuadraticFlatPlate,QuarterCircularInjectionRegion

Prepareflowsimulation Tool: LIMS, version 5.0.7, GUI

Select elements of quarter circular injection region (Toolbar “Select&Cover”, choose “Element” + “Lasso”):

Create a region (menu “Element” –“Create Region”)


See an overview of all regions specified (menu “LimsTools” – “RegionManager”)

Set material properties on the elements region (menu “Element” – “Material Properties”), e.g. fiber volume fraction or (anisotropic) permeability characteristics:


Runflowsimulation Set injection gate on the nodes region (menu “Node – Set Gate”) :

Run simulation (menu “File – Run Simulation”) and analyze filling time characteristics:

o Results with isotropic permeability settings (kxx = kyy):

o Results with anisotropic permeability settings (kxx = 10 kyy):


Example3:TransversePermeabilityCharacterizationCell,2007

Settingupthepartgeometry Tool: gmsh, version 2.8.5

Dimensions of the geometry (estimated from figure in the paper: Scholz et al.:

“Measurement of transverse permeability using gaseous and liquid flow”):

o Segments along flow direction: 0.02 / 0.03 / 0.02m

o Segments in horizontal direction: 0.04 / 0.03 / 0.10 / 0.03 / 0.04m

Set up overall geometry with basic geometric elements (menu “Add” – “Point”, “Straight

Line”, “Plane Surface”), work with two additional points along the long edge of the central

rectangular region in order to prevent unwantedly large meshing elements there:

Meshingthepart Tool: gmsh, version 2.8.5

Add 2D mesh, decrease element size using „Refine by Splitting“ (2x):


Datatransfer Tool: LIMS, version 5.0.7, command line

Commands:

o SETINTYPE “GMSH”

o READ

Choose .msh‐file exported through gmsh

o SETOUTTYPE “DMP”

o WRITE

Choose filename of .dmp‐file to export

Prepareflowsimulation Tool: LIMS, version 5.0.7, GUI

Clear results (menu “Global” – “Clear Results”):

Set fluid viscosity (menu “Global – Set Viscosity”):


Create regions:

o 1 x reinforcing material (central rectangular region)

o 2 x injection nodes (lower left and right nodes)

1 x injection nodes (united)

o 2 x injection gates (lower left and right rectangular regions)

1 x injection gates (united)

o 2 x vent (upper left and right rectangular regions)

1 x vents (united)

Set material properties for reinforcing material

o Fiber volume content: 50%

o Permeability: anisotropic, kxx = 1E‐11 m2, kyy = 1E‐13 m2

Set material properties for injection region


o Permeability: isotropic, 1E‐1 m2

Set material properties for vents


o Permeability: isotropic, 1E‐1 m2


Set injection gate on the nodes region (menu “Node – Set Gate”) :

Runflowsimulation Tool: LIMS, version 5.0.7, GUI


Meeting2‐QuestionsandAnswers:

QuestionsonSoftwareTools: Gmsh:

o . How to realize a 2D mesh with rectangular elements?

Check documentation!

Play with meshing options:

Lego:

o . What to expect after running lego.exe?

Tool seems to get stuck …

Specification of input and output file required!

Check help file “lego.chm” for further details

LIMS GUI:

o . Menu “Elements” – “Material Properties” is not opening when selecting a group of

elements?

Take care of selecting just one group of elements (1D, 2D, …)!!!

o . Are regions stored in the .dmp files?

After re‐loading a .dmp‐file, regions seem to have been cleared…

Regions are not stored in the .dmp‐files, but in the .zon‐files!

Choose automatic saving and loading in the options dialog!

o . Menu “Elements” – “Material Properties”

What does “fb” and “pr” stand for in the drop down menu of “Volume

Fraction”?

fb … fiber, i.e. fiber volume content

pr … porosity


o . What about setting anisotropic material properties?

After setting anisotropic properties and reselecting an element of the

region, “Isotropic Material” is indicated, whereas anisotropic (different from

the ones originally set) are displayed, partially grayed out …

By selecting the menu entry “Element” – “Material Properties”, the

user is asked to assign new parameters, i.e. the default settings for

new parameters are displayed (isotropic, kxy and ky grayed out, …)

When displaying the parameters currently set for a specific element

(menu “Select/Cover” – icon ), the permeability values are shown

with respect to the local coordinate system of the element, e.g.:

Are these to be understood as local permeability values, i.e.

permeability values of the particular FEM elements? What about the

local coordinate system?

The local coordinate system is defined as follows:

o Point of origin: in the first node of the element

o x‐axis: in the direction of node 1 to node 2

o y‐axis: orthogonal to the x‐axis, such that the x‐coordinate

of node 3 is positive


o . How to represent vents?

There is no direct way of integrating a vent as it is possible for injection

gates

However, there are a couple of alternatives, which are used depending on

the actual task:

1. manually specify the properties of 1D elements at the desired region

of the vents with (a) low cross‐section and (b) high permeability

2. define the region as an injection gate with a significantly lower

injection pressure as the “real” injection gate, followed by setting

the type of the gate to value “5” (instead of “1”), which represents

the behavior of a vent

3. integrate the vent region with a significantly higher size, such that it

takes a rather long time for it to be filled without reaching a border

4. stop the simulation with the restriction “run until node is reached”

and select a node at the vent region, however this might cause the

simulation to stop before fully completed …

Is it a good alternative to use 2D elements with very low fiber volume

content and very high permeability, respectively?

See option (3) above …

o . How to represent distribution media?

Region of very high permeability values?

Modify properties of 1D elements along the border underneath the

reinforcement with:

o Low cross‐section

o High permeability


QuestionsonSimulationExample2: . What is the impact of setting the properties of the 1D border elements such that they

“truly” represent a border, i.e. low cross‐section, compared to the flow behavior with the

default settings on the 1D elements, i.e. rather high cross‐section?

o Results with isotropic permeability settings (kxx = kyy = 10‐11):

o Results with anisotropic permeability settings (kxx = 10‐10, kyy = 10

‐12):


QuestionsonSimulationExample3: . Impact of meshing on the flow simulation results?

o If the meshing is selected finely enough, there should not be an impact of the

chosen meshing (triangular, quadratic elements) on the results

o In case of strongly anisotropic properties, e.g. in‐plane vs. transversal permeability

values, the mesh should be chosen such the element dimension ratio reflects the

ration of the anisotropic property, e.g. rectangular mesh with appropriate aspect

ratio

. What is the reason for the flow front being kind of blocked along the top border of the

central region of reinforcement before entering the vent zone?

o The border of the region is represented by 1D elements, whose properties have not

been modified by the user

o Without manually changing the properties of these 1D elements (permeability,

cross‐section), the default properties are used

o These default properties are given as to represent omega‐tubes, i.e. with a rather

high value for the cross‐section, high permeability, 0% fiber volume content

o This volume of the 1D elements needs to filled, the flow being limited through the

reinforcement, where the fluid has to flow through, i.e. it takes some considerable

time for the fluid to fill the 1D elements before filling the vent regions!

. How to overcome this?

o Manually set the properties of the 1D elements with:

High permeability

Low values for the cross‐section


Re:Example3:TransversePermeabilityCharacterizationCell,2007

Flowsimulationtrial1:o Run 1 – properties of reinforcement:

f: 50%

kxx: 1E‐11 m2 kyy: 1E‐13 m2

o Run 1 – properties of 1D border elements:

f: 0%

k: 3E‐08 m²

A: 8E‐07 m²

o Run 1 – results of flow simulation:

(C:\Users\Engineer\Desktop\2014_11_DrumImpregnation_SABIC_CCM\FlowSimulation\WorkingFiles\testFlowSimu

lation_03_TransversPermeabilityCell2007_V2_res4.dmp)

Race tracking!


f: 50%

kxx: 1E‐11 m2 kyy: 1E‐13 m2

o Run 2 – properties of 1D border elements:

f: 0%

k: 1E‐11 m²

A: 1E‐11 m²

o Run 2 – results of flow simulation:



Homogeneous 1D filling behavior!



f: 50%

kxx: 1E‐12 m2

kyy: 1E‐13 m2 o Run 3 – properties of 1D border elements:

f: 0%

k: 1E‐12 m²

A: 1E‐12 m²

o Run 3 – results of flow simulation



Clearly Non‐1D filling behavior!


WorkingwithLEGO

GeneralInformation LEGO is a simple data converter, it is to be invoked through command line according to:

LEGO infile.def outfile.dmp [tolerance]

with the parameters:

o infile.def … geometry definition file

o outfile.dmp … output file holding the meshing of the input geometry,

readable from LIMS and LIMS UI

o tolerance … optional value specifying how close nodes need to be to one

another in order to be merged by LEGO, default value: 1E‐04

The geometry definition file contains a sequence of blocks. There are several types of blocks

representing 1‐, 2‐ or 3‐dimensional geometric elements:

o 1D: Bar,

o 2D: Quad, Triangle and Pie,

o 3D: Brick.

By running LEGO, these blocks will be uniformly meshed (as far as possible)

Blockdefinitionconventions: Definition of a 1D bar element:

Definition of a 2D quad element:

For further information, see documentation file: lego.chm


Example1:Meshingofaquadraticplategeometry Dimensions:

o X‐dimension: 0.1m

o Y‐dimension: 0.1m

o Z‐dimension: 0.01m

o Number of nodes: 10 (along x‐direction) x 5 (along y‐direction)

Properties:

o f: 50%

o kxx: 1E‐12 m2

o kxy: 0 m2

o kyy: 1E‐12 m2

Geometry definition file:

Output (meshing) file – opened in LIMS GUI:


Example2:Meshingofatrapezoidalplategeometry Geometry definition file:



Example3:Meshingofthe“transversepermeabilitycharacterizationcell”geometry

Injection gates:





o f: 10%

o kxx: 1E‐1m2

o kxy: 0 m2

o kyy: 1E‐1m2

Vent regions:


o Y‐dimension: 0.3m (quite long, in order to ensure complete filling)



o f: 10%

o kxx: 1E‐1m2

o kxy: 0 m2

o kyy: 1E‐1m2

Reinforcement:




o Number of elements: 45 (along x‐direction) x 10 (along y‐direction)

o f: 50%

o kxx: 1E‐12m2

o kxy: 0 m2

o kyy: 1E‐13m2

Setup of the geometry definition file

o 2 quads representing the injection gate regions

o 2 quads representing the vent regions

o 1 quad representing the reinforcement


Running the flow simulation:

Example4:Meshingofthe“transversepermeabilitycharacterizationcell”geometrywithdistributionmediaadded

Setup of the geometry definition file

o 2 quads representing the injection gate regions

o 2 quads representing the vent regions

o 1 quad representing the reinforcement

o 1 bar representing the distribution media

Injection gates:

o as in Example 2

Vent regions:

o as in Example 2

Reinforcement:

o as in Example 2

Distribution media:


o Number of elements: 45 (along x‐direction)

o f: 0%

o k: 1E‐11m2

o cross‐section: 1E‐1m2

Fluid viscosity: 100mPas



Meeting3‐Discussion: Meshing with LEGO

Flow simulation trials with triangular‐shaped elements made with GMSH

Flow simulation trial with the quad‐element meshing made with LEGO

Meeting3‐Questions: Meshing:

o . Differences in the results with triangular‐shaped and quad elements?

Possibly an effect of the meshing

Try refining the triangular mesh and re‐run the simulation ‐ if changes occur,

the original triangular mesh has been chosen too coarse

Rerunning the simulation shows change in results:


o Comparison of results:

Coarse triangular mesh (GMSH):

Refined triangular mesh (GMSH):

Rather coarse quad mesh (LEGO):

Conclusions:

Even though the ratio of permeability values is 1:10, the simulation

run with a coarse triangular mesh shows a (half‐)circular flow front

advancement.

Effect of meshing obvious, as rerunning the simulation after refining

the mesh with a factor of 2 (4 times as much elements) gives results

showing more a reasonable elliptical flow front advancement.

Simulation run with refined mesh gives similar results as with quad

elements (mesh size ratio 2:1) meshing.


o . Aspect ratio of element dimensionality vs. aspect ratio of permeability values:

Why is there a quadratic relation? Explanation based on physical units?

Is there a relation to the permeability computation algorithm published by Chan and

Hwang, which makes use of a transformation from anisotropic system to isotropic

situation?

When deriving the Laplace‐type ODE from the pressure distribution in an

anisotropic material (a Non‐Laplace‐type ODE), make use of dimensionless

units and choose the scaling factors such the derivation works out:

;

;

.


FlowSimulationswith3DGeometryData

Example1:Meshingofacuboid Definition of a 3D brick element:

Outer dimensions and corresponding number of meshing elements:

o X‐dimension: 0.4m 11

o Y‐dimension: 0.3m 15

o Z‐dimension: 0.1m 15

Preform properties:

o f: 50%

o kxx: 1E‐12 m2

o kyy, kzz: 1E‐13 m2

o kxy, kxz, kyz: 0 m2

Fluid viscosity: 100mPas



Location of injection gate (central to bottom x‐y‐plane):


Comments:

o strongly elliptical flow front advancement along x‐y‐plane

ratio of permeability values 10:1

o rather hemispherical flow front advancement along y‐z‐plane

ratio of permeability values 1:1


Meeting4‐Questions: 3D visualization:

o . How to change visualization options?

Menu “View” – “Clipping”

Menu “File” – “Options”, identical with menubar “Mesh‐Display” and

Data scaling

Orthotropic/Perspective projection

o . How to visualize a cross‐section of a 3D object, e.g. the cuboid of example 1?

Within LIMS: use “Clipping” functionality

o . Alternative visualization options?

TecPlot … commercially available visualization tool for simulation output

data (free trial version available)

GMSH … free software tool

o . How to visualize simulation results with GMSH?

When starting the simulation in LIMS (menu “File” – “Run Simulation”),

choose “Edit Script”, which opens the simulation task file (file type: .lb)

Change line SETOUTTYPE "dump” to SETOUTTYPE "gmsh"

Change filename of output file: WRITE "filename.msh"


Open “filename.msh” file with GMSH

o . How to modify visualization parameters n GMSH?

Menu “Tools” – “Options” … projection mode

Menu “Tools” – “Visibility”

Menu “Tools” – “Clipping”

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