Details

Introduction to TwinMesh

Hello, this is Ertan Taskin from Ozen Engineering, Inc. In this video, I'll be discussing the TwinMesh software, its features, applications, and providing a tutorial. TwinMesh is an automatic high-quality grid generation tool for rotary positive displacement machines. Note that the simulation is not performed in TwinMesh; rather, it establishes the grid structure.

Simulation Workflow

The simulation workflow is as follows:

The grid for the machine is generated with TwinMesh.
The stator grid is integrated into the model using an additional tool such as ANSYS.
Preprocessing and simulation can be conducted using either CFX or Fluent.
The results can be post-processed with either CFD-Post or ANSYS.

Features of TwinMesh

Automatic tracking for 2D or 3D structures.
Easy geometry scaling, capable of handling very small gap sizes.
User control over mesh size, resolution, boundary layers, and local refinements.

Additional details and features of TwinMesh can be found in the reference recording.

Sample 2D Application: LobPump

Let's go through a sample 2D application of a LobPump:

Open TwinMesh and select the type of machine for mesh generation, such as LobPump, Internal Gear Pump, or Screw Compressors.
Import the geometry file for the LobPump 2D rotor.
Define boundary definitions for the rotor wall curves.
Set the geometry of the rotor with a pitch angle of 60 degrees and a rotor length of 1 mm.
Create a small gap of 0.1 mm to allow for computational cells to resolve the boundary layer.
Generate interfaces between the lobes and proceed with mesh generation.
Check mesh quality, ensuring a minimum angle greater than 18 degrees.
Export the generated mesh and open the solver setup in CFX.

Simulation Setup

In the simulation setup:

Define the rotational speed and pressure conditions.
Select the solver method and number of processes.
Export the mesh and open the solver to start the run.

Post-Processing

After the simulation completes, bring the solution into CFD-Post for detailed post-processing activities. You can examine:

Flow field changes.
Pressure distribution.
Operation of the machine on a cross-sectional plane.

Thank you for watching. We will see you in the next video. Goodbye!

Transcript

[This was auto-generated. There may be mispellings.]

Hello, this is Ertan Taskin from OZEN Engineering, and in this video, I'll be talking about the TwinMesh software, its features and applications, as well as a tutorial. TwinMesh is an automatic, high-quality grid generation tool for rotary positive displacement machines.

The simulation is not performed in TwinMesh; rather, the grid structure is established. The simulation workflow is as follows, from left to right: the grid for the machine is generated with TwinMesh, and then the stator grid is brought into the model with an additional tool such as NSYS Machine.

Preprocessing and simulation can be done either with CFX or Fluent, and the results can be post-processed with either CFD Post or NSYT. The grid can be generated for many types of machines and applications. TwinMesh features automatic tracking between meshes for 2D or 3D structures.

After mesh generation, ready-to-run input files can be exported easily to ANSYS CFD. The software also includes easy geometry scaling and can handle small gap sizes, typical for these kinds of pumps. Users can fully control mesh size, mesh resolution, boundary layers, and local refinements.

Many additional details and features of TwinMesh can be found in this reference recording. Let's go through a sample 2D application of LobPump. When we open TwinMesh, the pop-up screen asks for the type of machine we will generate the mesh for.

We can choose from LobPump, Internal Gear Pump, Screw Compressors, and more by scrolling left to right. For this project, we will do the LobPump. Import Geometry, and for this example, we will do LobPump 2D rotor. This brings us to two morphing structures.

With the control key and the left mouse button, we can select a portion of the rotor, and then with the right click, we can select all the connected curves. We can group these so that when we select again with the control, we can select everything at once.

Similarly, for the other rotor, then make the group. Let's define the boundary definitions for this one. Right-click boundary definition, rotor wall curve. This one, rotor wall curves are one; this one, rotor wall curves are two. Different colors represent that they are two different rotors.

Let's go to geometry and define the geometry of the rotor with a length of per pitch angle of 60 and with a rotor length of one millimeter. Since this is a 2D geometry, there's basically no length in the z direction. We'll take that to the power of 2, 25mm. We've finished the test.

If I want to rotate one and define the number of levels, this is three. But since it's typically mostly a circular feature, it's relatively easy to create it on the screen. Similarly, what we can do on the R2 side, define the number of lobes.

The facing radius is the same, 120. But in this time, we don't see it immediately on the screen because we have to create a new axis position for this one. So R1, or this lobe, and R2, the other lobe, are separated from each other with a 180-millimeter distance.

Now we have a casing that appears for R 2. We can quickly take a look at how the lobe operation is looking. So I'll actually demonstrate up to which angles we will go. As you see, we reached the 60 value, which was the pitch angle that we described.

So for 120 degrees of rotation, if you will, we define 60 motions. It's typically one-to-one, though. We should have done 120 rotations. But for the sake of this tutorial, let's consider 60. Back to the original state.

So I'm going to demonstrate to you that now with the casing and the rotor features, they are pretty much right there tangentially. They are perfectly symmetrical to each other. But we can create a small gap, which can be done fairly easily here in the scale value. Right?

So let's create a gap of 0.1 millimeters. When I hit somewhere on the screen, you see how they are separated from each other. That's pretty much 0.1 millimeters. And we can roughly measure this. As you see, that is so. And why do we need this?

Because we need to put enough computational cells to resolve the boundary layer between the stator and the rotor. That's why we need a clearance. So we can put computational cells there. We will do very similarly on the other side. Let me demonstrate here, too.

Let's come to rotor 2. And the scale value is called 0. 1. And as you see, they are also separated. Now, let's create the interfaces. Right-click the geometry and generate the current interface. See, it proceeds and it creates the interface between these two lobes, particularly in this position.

And we will continue to do the same thing for all the other positions. That's why we're going to come here, generate all interfaces. And after a few minutes, all the interfaces are generated. We can even take a look at how the interface is actually moving with the motion of the rotors.

Let's also select check all interfaces. I can just perform a similar operation. So we will move on to the mesh generation. Let's click mesh generation and put the maximum element size as 4.2 millimeters. First element height, inner is one; outer is also one.

Number of elements radially, 15. Number of nodes on the rotor, 15. Number of nodes on the rotor, 15. Number of nodes on the interface, 43. You can definitely play with these numbers and see how they are impacting the overall mesh quality.

Number of elements in the Z direction, let's keep it simple. So let's make this one right click on mesh generation and choose generate on the current mesh. Current meaning on the corresponding mesh. And we're going to go on the corresponding position of the rotors. As you see, it was very quick.

The mesh is generated for this particular position. If I zoom in, you will see how the mesh squeezes in and in the smaller regions, particularly on the interface as well as on the smaller gaps that we generated. There are plenty of cells there. Now let's check the mesh quality.

In order to check the mesh quality, we can select this button. And there are a few parameters that we can consider. This minimum angle is automatically presented here. And minimum angle greater than 18 degrees is recommended. And for this particular mesh, it is already satisfied.

Since this first mesh seems to be fine, let's generate all the other meshes very similarly. Generate all meshes. And we can see that the mesh is already satisfied. And we can see the mesh is generated for different positions. So for all the positions, the mesh is generated.

And we can see that the mesh is generated for different positions. Let's keep this as a CFX and this is not a 3D problem. Let's make it 2D. And for the fluid model, let's consider incompressible with cavitation.

So far, we have created the mesh or the grid structure of the rotating machine with TwinMesh. But we have the stator that should be attached to the geometry. So that could have been done previously with a different meshing software.

And we can actually come here and select the corresponding file and add to the problem over here. Right-click import stator mesh, and that is the corresponding stator, and the unit is meters. Except save the project, and I am going to keep the new project name as it is.

Let's define the other features, such as the rotational speed, revolution speed of R1, speed 0. Then we have standardization of the revolution that we are going to describe in the X direction. We have to do another thing out here. Let's make this 400. And that pressure is 1 bar.

We're not going to play with the temperature here. Other pressure is 3 bars, and number of timesteps per run, maximum coefficient loads. Let's increase this for the sake of the quality of the calculations. And start method. Instead of serial, we're going to select Intel NPR local.

And depending on the availability, we can increase the number of processes. Let's keep it as two for this case. In order to export the generated mesh, let's come to File, Export, All Files. So before clicking OK here, let's select Open the Solver Setup after the export.

So it's going to open the CFX3 to us automatically. And there you go, CFX3 window popped up. And as you see on the screen, the corresponding geometry is brought up with all the details and the boundary conditions and locations as they are all described. Let's save the setup CFX file. New project.

Okay. And then let's open the solver. Yes. And we will start the run. And okay. So let's see what happens. It's going to take some time to reach the convergence. So let's see what happens after the simulation completed.

We can bring the solution to CFD post or inside to perform detailed post-processing activities. In this case, I brought the solution into CFD post, and we can definitely do multiple things, such as looking at how the lobes are operating on a cross-sectional plane.

Similarly, we can bring the vectors and perform similar post-processing activities when the machine operates. Okay. So we can see that the flow field changes. We can definitely take a look at the pressure distribution, etc. And with that, this demonstration video is concluded.

Thank you for watching. And we will see you in the next video. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye. Bye.

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