Creating a grid for a semicylinder

Creation of the geometry

First of all, the geometry of the semicylinder must be done with DDN. Click on "geometry" in the upper menu, select "DDN tools" and "DDN" to enter in DDN.

1- Change of design and visual parameters

Some of the design and visual parameters must be changed before beginning.

In a first time select 1-Modals & Fonts and 2-Tolerance. You must change the different values :
-1-    0.001             (enter)
-2-    0.000004      (enter)
-3-    0.001             (enter)

Validate with the mouse.

Come back to the main menu.

Note: After each manipulation you must come back to the main menu by validating with the mouse and closing all the menus opened.

Then select 15-Advanced Designand and 1-Advanced Design Modals. In this menu the following changes must be done :

- 2-Curve Tolerance : enter 0.00001 (enter)
- 6- Refinement Level : enter 10 (enter)
- 8-Display Quality : select 2-Refined
-11-Conversion Tolerances : enter 0.001 (enter)
-12- Same Point Tolerance : enter 0.0001 (enter)
-13- Same Angle Tolerance : enter 0.01 (enter)
-17- Conversion New Entity : select 1-Keep
-18-Conversion Old Entity : select 3-Delete

Validate with the mouse and come back to the main menu.

2-Points creation
Two points, representing centers of semicircles, must be created. Click on  and . Enter coordinates for first point : for example 0. (enter), 0. (enter) and 0. (enter). Then validate with the mouse. Enter coordinates for second point : for example 0. (enter), 10. (enter) and 0. (enter) and validate with the mouse.

Note :
- Coordinates are real numbers that's why it is important to put a point after the number of the coordinate (or write it with its first decimal, 2.0 for example) when it is an integer and especially if you want to use Fluent by the way.
- Lengths must be exprimed in meters.

3- Semicylinder creation

Icem possesses an especially menu to create surface of revolution  :

Click on  and . Choose 1-Axis then 2-Between two points and select the two points with the mouse. After, enter the radius of the semicylinder, for example 4.0 meters. (enter), the starting angle 0.0. (enter) and the ending angle 180.0. (enter). Then validate with the mouse.

Come back to the main menu and close menu opened. The following geometry appears when you change the angle view using mouse :

Note : You can see and move the representation of the semicylinder by selecting  and using the mouse to translate, to zoom .... When you want to come back to the DDN creation , click again on   ( this icon allows to change the the dynamic mode )

4- Isoparametric curves creation

Now, we must create  a B-spline curve on each extremity of the semicylinder in order to create the two normal surfaces :
Select  and . Select the semicylinder with the mouse and choose 2-All edges. All the edges of the semicylinder become in orange color.

5- Points and lines creation
Points and lines making up surfaces around the semicylinder must be done. Click on  and select each side of the two vertical line of the semicylinder to make appear the four points of the semicylinder.
Then click on  and select the two upper points to create the first line and then the two lower points to create the second line.

6- Backgroung surface creation

Click on  and . For the background surface of the semicylinder select the four curves delimitate by the four points with the mouse and validate.

WARNING:   You must select curves in a rotative sense.

7-Conversion of the two circles in B-spline
Now, the two semicircles of the semicylinder must be converted in B-spline by clicking on  and on the  of . Select one of the circles and validate with the mouse. Choose 1-entire surface and 1-Tolerance, enter 0.001 (enter).

Proceed to the same operation for the other semicircle and come back again to the main menu.

8- Surfaces creation

Note : Before creating these surfaces you need to hide some surfaces. Click on  and  in the blank part. Select the surface you want hidden (lateral surface and background surface  of the semicylinder) and validate. You can refresh the scheme

Now we are going to divide each circle curves into 3 parts. This operation is necessary because we need four edges to create surface. Click on  and . Select one of the curves and choose 4-Divide into N segments, enter the number of segments you want, here 3 (enter) and select 2-Delete. Redo the same operation for the second semicircle curve.

We are going now to create surfaces as in section 5. For each surface we want create (each extremity) select the four curves bordering the semidisc in a rotative sense with the mouse and validate. Surfaces are created.

9- Interior point creation

You need a point inside the domain in order to situate the interior (where the grid will be situated). Create this point (for example 0. 5. 2.) like you have already done in section 1 and come back to the main menu.

The geometry with DDN is now terminated.

10-Save the geometry
The save is automatically by clicking on  and Quit in .

Creation of the families and the reference size cells

Now we are going to create families with DDN-tetin : in "DDN tools" in the upper menu, select "DDN->tetin" to enter in DDN->tetin and select your geometry file.

1- Change of the reference cell

The size of the reference cell must be changed. Select 1-modals, 1-reference element size and enter 0.5  for example (enter).

Come back to the main menu.

2-Families Creation

Select 2-Families and 1-Family-add. Enter the different names of famililies : inlet (enter), outlet (enter), wall (enter), sym (enter), fluid (enter). Validate.

Note :
-You can choose others name for all families except FLUID family which is a name you must choose for the interior domain (also, you can choose LIVE).
- The family SYM is a symetry family but you can change it if you want.

3-Elements Selection

Choose 7-Entity-add and for each family (inlet, outlet, wall, sym) select the adequate surface with the mouse and validate twice.

Note :
- You can see the geometry by clicking on  , so you are now in DDN and you can topple over in DDN->tetin by clicking on  and .
- All surfaces must be here B-splines. If it is not the case answer "y" for yes when the question "Convert in B-spline the curve selected?" appears.

Come back to the main menu in DDN->tetin.

4- Material domain creation

Now choose 3-Domains, 1-Create material domain and the family Fluid corresponding to the interior of the geometry, here fluid. Select the interior point with the mouse, validate and enter the size of cells you want inside the geometry, for example 0.5 (enter).

Come back to the main menu.

5-Save the project

You can quit and save by choosing 10-File/Exit and 2-File.

Creation of the grid

We can now proceed to the grid. We have choose to study the tetrahedra mesher.

3-Click on "Load Cut Domain" and unselect "Run Smoother" (we are going to see what the Smoother is in a next part). Click on Accept.

Boundary conditions and save the grid

We must now create the file which can be readen by a solver for example FLUENT 5.

1- Choose "Output" in the upper menu, select "Solver" and choose  "Fluent_V5".

2- Click on "Bound conds" and put the rigth boundary conditions to the different families with "New b.c.": INLET->velicity-inlet,
OUTLET->pressure-outlet, WALL->wall, SYM->symetry.

3-Click on "Fluent_V5 input". You can save the current projet if you want. In "Domain selection", select "Cut domain1". ICEM create a fluent.msh file in the repertory ./transfer.This file can be opened with Fluent 5.

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