ANSYS CFX-Mesh Tutorials phần 4 ppsx

The following geometry and meshing features are illustrated: If you want to skip the geometry creation part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tut

Setting up Inflation

The velocity gradients near the pipe wall surfaces can vary significantly, so it is advisable to apply inflation in these areas

the Inflated Boundary Click on Apply in the Details View.

Generating the Volume Mesh

Finally, you can generate the volume mesh

The mesh is now complete

project

Tutorial 3: Process Injection Mixing Pipe

CFX-Mesh Tutorials © SAS IP, Inc.

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If you want to continue by working through the CFX-5 example “Tutorial 3: Flow in a Process Injection Mixing Pipe” using the newly-generated mesh, and have CFX-5.7.1 in ANSYS Workbench installed on your machine, then follow these steps:

this entry, double-click on InjectMixerMesh.gtm to open up CFX-Pre.

Simu-lation” and “Importing a Mesh”

If you do not have CFX-5.7.1 in ANSYS Workbench installed or do not want to work through the CFX-5 example, then:

Section 2: Mesh Generation

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Tutorial 4: Circular Vent

This example creates the geometry and mesh for a simple chimney stack The following geometry and meshing features are illustrated:

If you want to skip the geometry creation part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tutorials

1 Geometry Creation

Creating the Project

Creating the Solid

The geometry consists of a cylindrical pipe which is placed in the center of a cylindrical region

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the origin and with radius 10 m

If you just extruded this circle, you would get a cylinder which consisted of three faces: circular top, circular bottom and the curved cylindrical face However, you will need to apply a boundary condition in the CFD simu-lation to just half of the curved cylindrical face The only way to do that effectively is to create the cylindrical face

in two parts This means that you need to modify the circle before extruding

of the list

2 Select the Y-axis and then select the circle somewhere near where it intersects the Y-axis You should find that a point appears at the intersection

the Y-axis occurs A second construction point should appear

Split Edge at All Points.

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10 m.

com-bining them where possible, which would prevent the splits in the circle from having any effect 9

Now you will cut material from this cylinder to form the vent itself

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the origin and with radius 1 m

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5

The geometry is now complete

2 Mesh Generation

First open CFX-Mesh

Tutorial 4: Circular Vent

CFX-Mesh Tutorials © SAS IP, Inc.

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1 Switch from DesignModeler to the Project Page using the tabs at the top of the window, and click on

Generate CFX Mesh to open CFX-Mesh.

Setting up the Regions

Create the region for the wind inlet:

Create the region for the opening to the atmosphere:

Create the region for the vent opening to the atmosphere:

2 Select the small circular face at the top of the vent to apply it to This can be slightly tricky to select directly since from most viewing positions it is behind another face Either:

below As you move the cursor into this position, the black “-Z”-axis will appear (it is not shown by default) This will put the geometry into a good position for picking the required face

itself to see the small circular face at the top of the vent without it being behind another face You can now select it directly

or

and a stack of Selection Rectangles (shown below) will appear at the bottom left of the Model View.

Note that exactly how many selection rectangles there are will depend on exactly what the viewing position of your model was when you clicked over the face

rectangle representing the front face You will be able to see from the selection rectangles that this front face is outlined in red, which means that it is currently selected Click on the rectangle which represents the face which you want As you click on the rectangle, the corresponding face in the geometry will highlight You may need to experiment to get the correct face

Section 2: Mesh Generation

Setting up the Mesh

Set the Maximum Spacing:

value

Create inflated surfaces for the vent and ground surfaces:

and the bottom of the large cylinder (lowest Z-coordinate)

Create a Control in the center of the vent to refine the mesh in this region of the simulation You will use a Line Control, which refines the mesh in the region around a line

Point, Line and Triangle Controls all make use of the Point Spacing object This defines a set of spacing values, which can be applied to the various Controls as desired

to 1.15.

anything in the Model View, and then right-click in the same place and choose Edit Enter 0 0 0 to set

the coordinates of the first Point

appro-priate Point Spacing for the Control Press Apply to complete the selection.

set Transparency to 40 %.

If you ensure that the new Line Control is selected in the Tree View, and look at the vent in the Model View, you should be able to see where the Control has been created, as shown below The line itself should be clearly visible, and the two spheres at each end show the Radius of Influence

Tutorial 4: Circular Vent

CFX-Mesh Tutorials © SAS IP, Inc.

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Generating the Surface Mesh

To get a clear view of how the Control affects the mesh, it is convenient to generate just part of the surface mesh

Z-co-ordinate)

Mesh The surface mesh will be generated on just the corresponding face.

Generating the Volume Mesh

Finally, you can generate the volume mesh

Section 2: Mesh Generation

The mesh is now complete.

project

If you want to continue by working through the CFX-5 example “Tutorial 4: Flow from a Circular Vent” using the newly-generated mesh, and have CFX-5.7.1 in ANSYS Workbench installed on your machine, then follow these steps:

this entry, double-click on CircVentMesh.gtm to open up CFX-Pre.

Simu-lation” and “Importing a Mesh”

If you do not have CFX-5.7.1 in ANSYS Workbench installed or do not want to work through the CFX-5 example, then:

Tutorial 4: Circular Vent

CFX-Mesh Tutorials © SAS IP, Inc.

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Tutorial 5: Blunt Body

This example creates the geometry and mesh for a simulation of flow over a vehicle body shape Due to the symmetry of both the geometry and the flow pattern, only half of the body needs to be modeled The following geometry and meshing features are illustrated:

If you want to skip the geometry creation part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tutorials

1 Geometry Creation

Creating the Project

2 Choose New Geometry to open DesignModeler, specifying the units as meters.

Creating the Body

To create the body shape, you will create a sketch and then extrude it A Cut Material operation will then be used

to shape the rounded end of the body

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the orientation of the axes) The required dimensions are: H1 = 1.44 m, V2 = 5.22 m

which opens to the right of the word Fillet.

the right of the word Chamfer.

Tutorial 5: Blunt Body

CFX-Mesh Tutorials © SAS IP, Inc.

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7 Use Angle from the Dimensions Toolbox to specify the angle between the chamfer and the top of the sketch to be 25 degrees, as shown below If the wrong angle is displayed just after you click on the second edge, then (before you click to position the dimension) right-click and choose Alternate Angle until the

correct angle is displayed After you have selected both of the edges which form the angle, remember

to click once to position the label before typing the angle, 25 degrees, into the Dimensions box in the

Details View

shown below

The sketch is now complete, and can be extruded to form the body

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Reversed.

Section 1: Geometry Creation

The front end of the blunt body is already rounded; however, some more material needs to be cut away from it

to get the correct shape

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2

sketch This icon will always place the currently-selected object (a plane, face or sketch) in the center of the Model View, and rotate the model so that you are viewing the object perpendicularly (or, in the case

of a non-planar face, so that you get a reasonable view of it) Right-click on the Model View and drag a box over the Solid to zoom into it

approx-imately the right length After you have clicked to place the third point (at the end of the second

line), then right-click and select Open End to finish the polyline.

ensures that they will always remain the same length, so if one changes, the other one will also change

of the polyline If the wrong part of the arc is being drawn (i.e a 270 degree segment instead of a

90 segment) just before you click on the second end point, then right-click and select Reverse to

correct it

required are: V1 = 0.9725 m, R2 = 0.5 m

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The end of your blunt body should now look the same as in the picture below

Tutorial 5: Blunt Body

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Creating the Containing Box

The next step is to create the box around the blunt body to form the region for the fluid flow simulation To stop the new solid from merging with the blunt body, first you must freeze it, and you will also give it a name to identify it more easily later on

under-neath this entry In the Details View, you will now see the information relating to the body Click on the word “Solid” in this information, and change it to read “Blunt Body” Pressing Enter on the keyboard will let the name change take effect

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that the rectangle extends below the bottom of the body (below the XYPlane) The required dimensions are: V5 = 12.39 m, V6 = 17.61 m, H7 = 4.75 m, H8 = 0.25 m

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create the solid

You can now cut out the blunt body from the containing box, to leave just the region of interest for the CFD simulation

Section 1: Geometry Creation