Lesson 2:
A Steady State Composite Slab
In order to demonstrate solution of thermal problems using ANSYS two conduction problems will be illustrated. The first one is the steady state solution of the temperature field in a composite slab with a hole in one of the slabs. The geometry and boundary conditions under consideration are illustrated in the figure shown below.
In the following the symbol ``\ret'' will be used to indicate that you
should hit return on the keyboard. The symbol ``\click'' will be used to
ask you to click the first button on the mouse. \click \click will be used
to indicate that you should double-click on a particular item.
ANSYS Commands for the Steady State Problem
/units,si \ret (in the grey box)
/title,Steady state slab problem \ret (also in grey box)
Preprocessor \click
Element Type \click
Add/Edit/Delete \click
Add \click
Thermal Solid \click (in library of element types - left box)
Quad 4node 55 \click
OK \click
Close \click
plane55 will produce either quadrilateral or triangular elements for thermal analysis
Material props \click (green menu box on left)
Isotropic \click
Type in a number to identify the material
OK \click
Enter Thermal Conductivity value KXX = 20
Same procedure will be used to enter values of other properties when necessary
OK \click
Repeat the process to enter the KXX value for the second material in the problem
Go to the section labeled Modeling
Create \click
Rectangle \click ( in the Areas section )
By Dimensions \click
Enter dimensions X1,Y1 and X2,Y2 for the left bottom corner and right top corner of the 1st rectangular area respectively.
OK \click
Create \click
Rectangle \click ( in the Areas section )
By Dimensions \click
Enter dimensions X1,Y1 and X2,Y2 for the left bottom corner and right top corner of the 2nd rectangular area respectively.
OK \click
Plot \click (Blue menu on top)
Areas \click
This produces a plot of the two areas you just created and fills the entire view screen with them.
Create \click
Circle \click ( in the Areas section )
By Dimensions \click
Enter the circle radius as RAD1
OK \click
This creates a circle at the left corner of our first rectangle. We want to cut a hole in the rectangle. So we must move this circle from the left bottom corner to the center of the 1st rectangle.
Move/modify \click
Areas \click
Pick the circular are with the mouse
OK \click (green box on the left )
Enter the x and y offsets to place the circular area in the center of our 1st rectangular box.
Plot \click (blue menu on top)
Replot \click
Now we must subtract the circular area from the first rectangle to create the circular hole.
Operate \click (green menu on left)
Subtract \click
Areas \click
Enter 1 (green box on top, used to be grey)
OK \click (green menu on left )
Enter 3 (green box on top)
OK \click (green menu on left)
This should result in a circular hole in area 1.
The two rectangular areas that we created are not joined in any way. We must therefore glue them, letting ANSYS know that they are in contact, to make it one big composite slab.
Operate \click
Glue \click
Areas \click
Pick all \click (green box on left)
OK \click (green box on left)
This will renumber the areas. Now Area 1 is the rectangular area with the hole and Area 2 is the other rectangular area.
It is good to save your work often. To do this
File \click (blue menu on top)
Save as Jobname.db \click
Now we must mesh our model. To do this
Shape & size \click (in the meshing region in the green box on the left)
Global, Other \click
Enter the maximum edge length that you want to allow (I have chosen 1cm, 0.01m). Enter this in the EDGMX field.
OK \click
Mesh \click
Areas, Free \click
Pick all \click (green box on left)
OK \click
Plot \click (Blue menu on top)
Elements \click
This produces a plot of the two areas and the elements created by the meshing procedure.
We have not yet specified the material properties for the two rectangles. These properties are usually assigned to the elements. Now that we have nodes and elements we can go ahead and do that.
Select \click (blue menu on top)
Entities \click
Areas \click (in the blue menu which pops up)
OK \click
This opens up a green box on top.
Enter 1 \ret
OK \click (green box on the left)
Select \click (blue menu on top)
Entities \click
Elements \click (in the blue menu which pops up)
Click on the box which says By Num and select Attached to
Areas \click (top half of menu)
OK \click (bottom of blue menu)
Now ANSYS is pretending to only know about Area 1 and the elements attached to it. If you go:
Plot \click (blue menu top)
Replot \click
You should see:
Now enter
mpchg,1,all \ret (in grey box top-left)
This sets properties corresponding to material 1 defined earlier to the selected elements. Again, ANSYS only knows about the elements we selected above. It does not know about the elements in the second rectangle.
Since we are done with this piece, we must now select everything so ANSYS "remembers" about the rest of the model.
Select \click
Everything \click
Repeat above procedure to select elements attached to area 2 (rectangle on the right side) and set the properties to those of material number 2 defined earlier. Be sure to "select everything" once you have finished.
Let's look at what we did:
PlotCtrls \click (blue menu on top)
Numbering \click
Elem / Attrib numbering \click
select "Material numbers"
OK \click
This should give you a color plot showing the areas and elements. Each element contains a number which refers to the material numbers we just set for each piece. The different material types are also denoted by the different colors.
We have now completed creating a geometric model of our composite slab with a hole and also meshed it for finite element analysis. Note the procedure used to assign different material properties to different regions of the model.
FINISH \click \click (top right corner of screen)
This finishes the preprocessing
Once again it is wise to save the model to a file.
We now proceed to apply the boundary conditions and obtain a steady state solution. Note: All geometry boundaries are adiabatic by default in ANSYS. So if you wish to apply symmetry or zero heat flux boundary conditions at any face of your model you have to do nothing to that face. To go to the solution phase of the problem
Solution \click (green box on left)
Applying temperature boundary conditions
Apply \click (green box on left in the Loads section)
Temperature \click
On nodes \click
Box \click (green box at left)
Draw a box around the left edge of the model to pick these nodes.
OK \click (green box on left)
Enter the temperature 200
OK \click (grey box on top)
Repeat above procedure to apply the temperature boundary condition on the right boundary.
Applying heat transfer coefficient on top surface
Apply \click (green box on left in the Loads section)
Convection \click
On Lines \click
Box \click (green box at left)
Draw a box around the top edge of the model to pick the lines along the top edge.
OK \click (green box on left)
Enter h of 150 for VALI and fluid temperature of 25 for VAL2I
OK \click (grey box on top)
The convection boundary condition was applied to lines which are solid model features. We must transfer this boundary condition to the FE model itself.
to transfer the bc to the FE model:
sbctran \ret (grey box on top)
Now to see the boundary condition:
PlotCtrls \click (blue menu top)
Symbols \click
Surface Load Symbols \click
select "Convect FilmCoef"
Show pres and convect as \click
select "Arrows" \click
OK \click
Applying heat flux on the circular hole surface
First let's zoom in to magnify the circular hole
PlotCtrls \click (blue menu top)
Pan, Zoom, Rotate \click
Box Zoom \click
Draw a box around the hole by getting the left top corner of box by clicking left mouse button and dragging. At final corner of zoom box click the left mouse button again.
Apply \click (green box on left in the Loads section)
Heat flux \click
On lines \click
Use mouse to pick at 4 diametrically opposite points on the edge of the circle. This will select the four lines which make up the circle.
OK \click
Enter the heat flux of 100 for VALI
OK \click (grey box on top)
The heat flux boundary condition was applied to lines which are solid model features. We must transfer these to the FE model. To do this
sbctran \ret (grey box on top)
PlotCtrls \click (blue menu top)
Symbols \click
Surface Load Symbols \click
select "Heat Fluxes"
Show pres and convect as \click
select "Arrows" \click
OK \click
Fit \click (blue zoom box on right)
We do not do any thing to the bottom edge of our model because it is an adiabatic surface by default.
Again this is a good place to save the model.
To obtain a FEM solution
Current LS \click (green box on left in the Solve area)
Close \click (blue summary window) OK \click (green "Solve Current Load Step" window)
Wait for the solution (takes but a few seconds).
Close \click (yellow info window)
Finish \click (green box on left)
This finishes the solution phase of the problem
Postprocessing
This is where you get all the nice colored plots !!!
General Postproc \click
Plot results \click
Nodal Solu \click (in the contour plot area)
OK \click
This should give you a nice contour plot of the temperature field in the composite slab. You can ignore the yellow warning message if one comes up. Notice how the contour lines are perpendicular to the bottom edge of the model indicating zero temperature gradient and hence a zero heat flux on that surface. Also notice the non-zero gradient of the contour lines on the edges of the circular hole indicating the presence of the heat inflow.
Finish \click
File \click (blue menu top)
Exit \click
Save Everything \click
OK \click
THIS CONCLUDES THE STEADY STATE SLAB PROBLEM
A Steady State Composite Slab
In order to demonstrate solution of thermal problems using ANSYS two conduction problems will be illustrated. The first one is the steady state solution of the temperature field in a composite slab with a hole in one of the slabs. The geometry and boundary conditions under consideration are illustrated in the figure shown below.
ANSYS Commands for the Steady State Problem
/units,si \ret (in the grey box)
/title,Steady state slab problem \ret (also in grey box)
Preprocessor \click Element Type \click
Add/Edit/Delete \click
Add \click
Thermal Solid \click (in library of element types - left box)
Quad 4node 55 \click
OK \click
Close \click
plane55 will produce either quadrilateral or triangular elements for thermal analysis
Material props \click (green menu box on left)
Isotropic \click
Type in a number to identify the material
OK \click
Enter Thermal Conductivity value KXX = 20
Same procedure will be used to enter values of other properties when necessary
OK \click
Repeat the process to enter the KXX value for the second material in the problem
Go to the section labeled Modeling
Create \click
Rectangle \click ( in the Areas section )
By Dimensions \click
Enter dimensions X1,Y1 and X2,Y2 for the left bottom corner and right top corner of the 1st rectangular area respectively.
OK \click
Create \click
Rectangle \click ( in the Areas section )
By Dimensions \click
Enter dimensions X1,Y1 and X2,Y2 for the left bottom corner and right top corner of the 2nd rectangular area respectively.
OK \click
Plot \click (Blue menu on top)
Areas \click
This produces a plot of the two areas you just created and fills the entire view screen with them.
Create \click
Circle \click ( in the Areas section )
By Dimensions \click
Enter the circle radius as RAD1
OK \click
This creates a circle at the left corner of our first rectangle. We want to cut a hole in the rectangle. So we must move this circle from the left bottom corner to the center of the 1st rectangle.
Move/modify \click
Areas \click
Pick the circular are with the mouse
OK \click (green box on the left )
Enter the x and y offsets to place the circular area in the center of our 1st rectangular box.
Plot \click (blue menu on top)
Replot \click
Now we must subtract the circular area from the first rectangle to create the circular hole.
Operate \click (green menu on left)
Subtract \click
Areas \click
Enter 1 (green box on top, used to be grey)
OK \click (green menu on left )
Enter 3 (green box on top)
OK \click (green menu on left)
This should result in a circular hole in area 1.
The two rectangular areas that we created are not joined in any way. We must therefore glue them, letting ANSYS know that they are in contact, to make it one big composite slab.
Operate \click
Glue \click
Areas \click
Pick all \click (green box on left)
OK \click (green box on left)
This will renumber the areas. Now Area 1 is the rectangular area with the hole and Area 2 is the other rectangular area.
It is good to save your work often. To do this
File \click (blue menu on top)
Save as Jobname.db \click
Now we must mesh our model. To do this
Shape & size \click (in the meshing region in the green box on the left)
Global, Other \click
Enter the maximum edge length that you want to allow (I have chosen 1cm, 0.01m). Enter this in the EDGMX field.
OK \click
Mesh \click
Areas, Free \click
Pick all \click (green box on left)
OK \click
Plot \click (Blue menu on top)
Elements \click
This produces a plot of the two areas and the elements created by the meshing procedure.
We have not yet specified the material properties for the two rectangles. These properties are usually assigned to the elements. Now that we have nodes and elements we can go ahead and do that.
Select \click (blue menu on top)
Entities \click
Areas \click (in the blue menu which pops up)
OK \click
This opens up a green box on top.
Enter 1 \ret
OK \click (green box on the left)
Select \click (blue menu on top)
Entities \click
Elements \click (in the blue menu which pops up)
Click on the box which says By Num and select Attached to
Areas \click (top half of menu)
OK \click (bottom of blue menu)
Now ANSYS is pretending to only know about Area 1 and the elements attached to it. If you go:
Plot \click (blue menu top)
Replot \click
You should see:
Now enter
mpchg,1,all \ret (in grey box top-left)
This sets properties corresponding to material 1 defined earlier to the selected elements. Again, ANSYS only knows about the elements we selected above. It does not know about the elements in the second rectangle.
Since we are done with this piece, we must now select everything so ANSYS "remembers" about the rest of the model.
Select \click
Everything \click
Repeat above procedure to select elements attached to area 2 (rectangle on the right side) and set the properties to those of material number 2 defined earlier. Be sure to "select everything" once you have finished.
Let's look at what we did:
PlotCtrls \click (blue menu on top)
Numbering \click
Elem / Attrib numbering \click
select "Material numbers"
OK \click
This should give you a color plot showing the areas and elements. Each element contains a number which refers to the material numbers we just set for each piece. The different material types are also denoted by the different colors.
We have now completed creating a geometric model of our composite slab with a hole and also meshed it for finite element analysis. Note the procedure used to assign different material properties to different regions of the model.
FINISH \click \click (top right corner of screen) This finishes the preprocessing
Once again it is wise to save the model to a file.
We now proceed to apply the boundary conditions and obtain a steady state solution. Note: All geometry boundaries are adiabatic by default in ANSYS. So if you wish to apply symmetry or zero heat flux boundary conditions at any face of your model you have to do nothing to that face. To go to the solution phase of the problem
Solution \click (green box on left)
Applying temperature boundary conditions
Apply \click (green box on left in the Loads section) Temperature \click
On nodes \click
Box \click (green box at left)
Draw a box around the left edge of the model to pick these nodes.
OK \click (green box on left)
Enter the temperature 200
OK \click (grey box on top)
Repeat above procedure to apply the temperature boundary condition on the right boundary.
Applying heat transfer coefficient on top surface
Apply \click (green box on left in the Loads section)
Convection \click
On Lines \click
Box \click (green box at left)
Draw a box around the top edge of the model to pick the lines along the top edge.
OK \click (green box on left)
Enter h of 150 for VALI and fluid temperature of 25 for VAL2I
OK \click (grey box on top)
The convection boundary condition was applied to lines which are solid model features. We must transfer this boundary condition to the FE model itself.
to transfer the bc to the FE model:
sbctran \ret (grey box on top)
Now to see the boundary condition:
PlotCtrls \click (blue menu top)
Symbols \click
Surface Load Symbols \click
select "Convect FilmCoef"
Show pres and convect as \click
select "Arrows" \click
OK \click
Applying heat flux on the circular hole surface
First let's zoom in to magnify the circular hole
PlotCtrls \click (blue menu top)
Pan, Zoom, Rotate \click
Box Zoom \click
Draw a box around the hole by getting the left top corner of box by clicking left mouse button and dragging. At final corner of zoom box click the left mouse button again.
Apply \click (green box on left in the Loads section) Heat flux \click
On lines \click
Use mouse to pick at 4 diametrically opposite points on the edge of the circle. This will select the four lines which make up the circle.
OK \click
Enter the heat flux of 100 for VALI
OK \click (grey box on top)
The heat flux boundary condition was applied to lines which are solid model features. We must transfer these to the FE model. To do this
sbctran \ret (grey box on top)
PlotCtrls \click (blue menu top)
Symbols \click
Surface Load Symbols \click
select "Heat Fluxes"
Show pres and convect as \click
select "Arrows" \click
OK \click
Fit \click (blue zoom box on right)
We do not do any thing to the bottom edge of our model because it is an adiabatic surface by default.
Again this is a good place to save the model.
To obtain a FEM solution
Current LS \click (green box on left in the Solve area)
Close \click (blue summary window) OK \click (green "Solve Current Load Step" window)
Wait for the solution (takes but a few seconds).
Close \click (yellow info window)
Finish \click (green box on left) This finishes the solution phase of the problem
Postprocessing
This is where you get all the nice colored plots !!!
General Postproc \click
Plot results \click
Nodal Solu \click (in the contour plot area)
OK \click
This should give you a nice contour plot of the temperature field in the composite slab. You can ignore the yellow warning message if one comes up. Notice how the contour lines are perpendicular to the bottom edge of the model indicating zero temperature gradient and hence a zero heat flux on that surface. Also notice the non-zero gradient of the contour lines on the edges of the circular hole indicating the presence of the heat inflow.
Finish \click
File \click (blue menu top)
Exit \click
Save Everything \click
OK \click
THIS CONCLUDES THE STEADY STATE SLAB PROBLEM
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Lesson 3, Transient Conduction |