ANSYS CFX-Mesh Tutorials phần 9 docx

To create a mesh that is appropriate for formal quantitative analysis of the airlift reactor in this tutorial, the maximum edge length should be 0.5 cm or shorter.. If you want to contin

Setting up the Regions

Create the 2D Regions:

three parts of the outside wall (highest X-coordinate), the bottom face of the reactor (lowest Y-coordinate) and the bottom part of the small hole which forms the ring sparger

used for Symmetry1

Finally, create a Composite 2D Region on the internal face which will form the draft tube In order to do this, it

is important to understand the difference between faces and 2D Regions when there are multiple solids in the geometry, and how to use the selection rectangles If you have not already done so, you are advised to work through or at least read the meshing section of Tutorial 6: Butterfly Valve and the meshing section of Tutorial 10: Heating Coil

For the Composite 2D Region which comprises the draft tube, it is appropriate to include only one side of the internal face When you come to set up the Thin Surface boundary condition in CFX-Pre, the other side of the face will then be automatically identified as the other side of the thin surface

to DraftTube.

viewing position for the selection

Tutorial 11: Airlift Reactor

CFX-Mesh Tutorials © SAS IP, Inc.

110

4 The selection rectangles will appear The 2D Regions they correspond to are (from left to right): outside

of the column, draft tube face (outside), draft tube face (inside), face from symmetry plane Click on the second one down (draft tube face, outside), to select it

Setting up the Mesh

Set the Maximum Spacing:

value

A maximum edge length of 1 cm will produce a coarse grid of about 4000-5000 nodes, suitable only for instruc-tional and demonstrative uses With the use of such a coarse mesh, the recirculation flow patterns in the reactor cannot be resolved adequately and some difficulties in convergence may be expected To create a mesh that is appropriate for formal quantitative analysis of the airlift reactor in this tutorial, the maximum edge length should

be 0.5 cm or shorter The resulting mesh will contain significantly more nodes

Because the Default Face Spacing is set to use an Angular Resolution of 30 degrees, the mesh around the

sparger is automatically refined since the sparger has a high curvature

Section 2: Mesh Generation

Generating the Volume Mesh

Finally, you can generate the volume mesh

The mesh is now complete

project

If you want to continue by working through the CFX-5 example “Tutorial 16: Gas-Liquid Flow in an Airlift Reactor” 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 BubbleColumnMesh.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 11: Airlift Reactor

CFX-Mesh Tutorials © SAS IP, Inc.

112

Tutorial 12: Room with Air Conditioning

This example creates the geometry and mesh for a room geometry, which can then be used in simulations to determine the effectiveness of an air conditioning system In the CFD simulation, the air is input through a small vent in the roof of the room

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

for Heating, Ventilation and Air Conditioning.)

Creating the Solid

The first step is to create the main solid, which is a simple box

1

at the origin and another at X = 3.0 m, Y = 3.0 m

5

Breaking the Faces to form the Boundary Conditions

The solid that you have just created has six rectangular faces Some of these faces need breaking up, so that the features such as windows, door and vents exist as separate faces of the solid This can be done by using Extrude with the Imprint Faces option

Using this option requires sketches of the correct dimensions to be created first However, when the Extrude operation takes place, you cannot choose to have the Imprint Faces action only apply at a specified face; it will apply at all faces between the sketch and the required face For this reason, the sketches cannot be created on the existing three planes since then they would always affect the faces of the solids which are co-planar with these planes This means that you need to start by creating a new plane

1

3

4

the Sketching tab to create a rectangle which has one corner at X = 0.05 m, Y = 1.3 m and another at X

= 0.15 m, Y = 1.7 m

5

7

Tutorial 12: Room with Air Conditioning

CFX-Mesh Tutorials © SAS IP, Inc.

114

Notice that in the figure above, the top face has been selected in order to show that it is in two parts.

These operations now need to be repeated to break the faces to form the windows and side vent

1

3

4

the Sketching tab to create a rectangle which has one corner at X = 1.25 m, Z = 0.75 m and another at X

= 1.75 m, Z = 1.75 m

corner at X = 2.05 m, Z = 0.15 m and another at X = 2.55 m, Z = 0.55 m

6

8

Section 1: Geometry Creation

3

4

the Sketching tab to create a rectangle which has one corner at Y = 1.25 m, Z = 0.75 m and another at Y

= 1.75 m, Z = 1.75 m

5

7

face

Tutorial 12: Room with Air Conditioning

CFX-Mesh Tutorials © SAS IP, Inc.

116

Finally, you need to break one more face to make a face for the door However, this time, the plane which contains the sketch to be extruded must be outside the geometry Otherwise, because the door reaches the edge of the room, you will find that the rectangular (unbroken) face which shares an edge with the door will be broken 1

3

4

the Sketching tab to create a rectangle which has one corner at Y = 2.3 m, Z = 0.0 m and another at Y = 3.0 m, Z = 2.0 m

5

7

Section 1: Geometry Creation

The geometry is now complete.

2 Mesh Generation

First open CFX-Mesh

Generate CFX Mesh to open CFX-Mesh.

Setting up the Regions

Create the 2D Regions:

the plane with the highest Z-coordinate

This plane has two cutout rectangular faces, and you need the one which is taller and located at a higher Z-coordinate

This plane has two cutout rectangular faces, and you need the one which is smaller and located at a lower Z-coordinate

face with the highest X-coordinate

Setting up the Mesh

Set the Maximum Spacing:

Tutorial 12: Room with Air Conditioning

CFX-Mesh Tutorials © SAS IP, Inc.

118

2 In the Details View, change Maximum Spacing to 0.25 m, and press Enter on the keyboard to set this

value

This is a coarse length scale, suitable only for tutorial purposes In order to better resolve the flow near the inlet and outlet vents, Face Spacings will be applied to these regions to refine the mesh

Setting up Inflation

It is a good idea to put inflation on the walls

except for Inlet and VentOut The Details View should show 6 Composites after you have made the

selection

Generating the Volume Mesh

Finally, you can generate the volume mesh

The mesh is now complete

project

If you want to continue by working through the CFX-5 example “Tutorial 17: Air Conditioning Simulation” 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 HVACMesh.gtm to open up CFX-Pre.

Section 2: Mesh Generation

3 Work through the CFX-5.7.1 tutorial, missing out the instructions in the sections “Creating a New 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 12: Room with Air Conditioning

CFX-Mesh Tutorials © SAS IP, Inc.

120

Tutorial 13: Can Combustor

This example creates the mesh for a can combustor, which might typically be found in a gas turbine engine The geometry is complex and consists of 5 separate solid bodies It will be imported complete from a Parasolid file The diagram above right shows the geometry schematically with part of the outer wall cut away The following geometry and meshing features are illustrated:

This tutorial requires you to have a copy of the Parasolid file Combustor.x_t If you do not already have this file,

then:

required Parasolid file)

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

1 Geometry Import

Creating the Project

Importing the Geometry

The geometry is imported complete from a Parasolid file

already got this file, refer to the introduction to this tutorial for details of where to find it.)

3

The Tree View should now show that you have 5 Parts, 5 Bodies In order to produce a single mesh that contains

all of the bodies (rather than one mesh per body), they must be combined into one part

1

that you can only select Solid Bodies in the next operation, which helps to make the selection process easier

•

bodies Once you have released the mouse button, the status bar (the bar along the bottom of the

ANSYS Workbench window) should change to show that you have selected 5 Bodies.

The Tree View should now show that you have 1 Part, 5 Bodies The geometry does not need any further

modifications

2 Mesh Generation

First open CFX-Mesh

Generate CFX Mesh to open CFX-Mesh.

Tutorial 13: Can Combustor

CFX-Mesh Tutorials © SAS IP, Inc.

122

Setting up the Regions

Create the 2D Regions:

bottom of the combustor The easiest way to select them as follows:

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 faces

below (note that the colors in your geometry may differ from the picture below)

geometry (lowest Z-coordinate), as shown below

on the main body of the combustor These introduce extra air to aid combustion

Section 2: Mesh Generation