Week 3 Challenge : CFD meshing on Turbocharger

CFD meshing on Turbocharger

Aim : CFD meshing on Turbocharger Using ANSA

Objetives:

For the given model, check for the geometrical errors to make appropriate volumes. Create and assign PIDs as shown in the video. Perform surface mesh with the given target lengths as per PIDs.

Blade stage-1 = 1 mm
Blade stage-2 = 1 mm
Impeller = 2 mm
Shaft rotor = 1 mm
Turbo casing = 5 mm
Compressor casing = 5 mm
Inlet casing cover = 5 mm

Procedure:

Topology clean up

Check for errors in geometry, by selecting geometry checks.
After selecting the checks we want to perform in geometry checks, hit execute.
After we hit execute we get errors.
The errors we got are:

Now we fix one by one
For fixing single cons we create new surface using these options:

Fixing the errors:

First errors we fix is this glitch on the surface
These glitches occur due to overlapping of the surfaces

We fix this glitch by deleting the unwanted pink surface.
This can be done by selecting delete option and selecting the surface.
Since its hard to select particular surface we want to delete, we can hide the green PID to delete the pink PID surface which we don’t want.

We now again unhide the PID we hid, now our overlapping surface is fixed.

Now we have extended surface at the bottom.

We fix this extended surface by deleting the extended surface and creating the new surface by COONS option.

Fixing the single coons:

On topside of the model we have single cons.
We cannot directly fix this by creating the surface because the surface penetrates into the model and we don’t get proper surface.
To fix this, project hot points and create small surfaces.

After creating small surfaces , now its easy to fix the single cons.

Create a new surface

We check for any topological errors present, to see the hidden errors , press ctrl + shift to see the single cons.

Now in wireframe mode we can easily see the single cons, first we fix the upper single con

Upper single con:

Hide the surfaces, to clearly the see the single cons present inside the model.

Here one surface is penetrating into another, and there is no connection between surfaces.
To fix this select intersect option.
After selecting intersect select the first surface and second surface which we want to connect.

After connecting the two surfaces delete the extended surfaces.

There is a glitched surface present, means surfaces are overlapping.

To fix this select the orange surfaces cross hatches and delete.

Now the only single con error present is in the bottom surface of the model.

It cannot be fixed by fill hole or new surface, because the surface which we get gets penetrated into the surface.

To fix this create hot points by parametrical option and create about 7 hot points on either side.

Similarly create hot points on the other side. After creating hot points create a new surface by COONs option and select alt option to see the surface we need and create.

Similarly create new surfaces on all the hot points we created.

We can now see the error is fixed.

Again check geometry for any other errors present.

There are triple and single cons.

Locate the errors, Errors can be seen easily in wireframe mode.

Press ctrl + shift to enter into wireframe mode.

We can clearly see the single con present.

To fix this use TOPO option and select the cons, now there will be triple con created.

We check for any overlaps and triple cons.

We see there are overlapped surfaces.

Delete the pink colour PID

Delete the blue surface, but if try to delete it will delete the whole surface

To fix this first we need to separate the face from the whole surface.

To do this, Use cut faces option and add cuts.

We can now see the surface is separated , now delete the surface.

Now there will be single con present at the deleted surface.

To fix this use TOPO and select cons.

Now the error is fixed.

Check for triple cons.

We still have triple con present here.

Delete the extra surface.

Check again for any single and triple cons

We find the single con here

If we delete the surface entire surface is deleted, to fix this use project Cons and project it on the face.

Now delete the extra surface created and separated by cons.

Again check for errors.

We see there is triple con present here, but this is not actually an error. So we ignore it.

Since there are no other errors present, look for open surfaces, we have two open surfaces one on the topside and other on bottom side, inlet and outlet.

We close these surfaces by creating new surface by Cons.

Outlet:

Inlet:

We have another open chamber:

We close this by creating new surface:

There is another open surface present, we close this too.

Close the bottom opening:

Check for common volume:

Since we cannot see through the shaft there is a surface present between delete that existing surface and check again:

Delete these overlapping surfaces:

After deleting the surface we have single con fix this using topo :

Now we have a common volume:

Delete the remaining overlapped surface:

ASSIGNING PIDs:

Topology correction is over, now we create PIDs.

Create new PIds and assign regions.

Turbo casing:

Impeller:

Shaft rotor:

Blade stage -1 and Blade stage -2:

Compressor casing:

Casing inlet and outlet:

Delete the empty PIds by using compress option:

After deleting the empty PIDs we only left with PIDs we need:

Surface meshing:

Surface mesh Individual PIDs:

Since outer casings and covers have same target length we mesh these all together:

Compressor casing:

Target length = 5mm

Minimum target length = 3mm

Maximum target length = 7mm

Inlet casing cover:

Target length = 5mm

Minimum target length = 3mm

Maximum target length = 7mm

Turbo casing:

Target length = 5mm

Minimum target length = 3mm

Maximum target length = 7mm

Give mesh parameter and quality criteria values:

Mesh these PIDs :

Impeller:

Target length = 2mm

Minimum target length = 1mm

Maximum target length = 3mm

Blade stage-1 and Blade stage-2:

Target length = 2mm

Minimum target length = 1mm

Maximum target length = 3mm

Rotor shaft :

Target length = 2mm

Minimum target length = 1mm

Maximum target length = 3mm

At the intersection of the two surfaces there is a transition:

We have complete surface meshing:

Volumetric meshing:

Select define and detect on whole db

After we select detect whole db.
Ansa detected volume.
Now we need to delete the volumes which we do not require.
We will mesh the volumes which are not taken by parent geometry thickness.
We will not do volumetric mesh for thickness, we mesh only the volume where fluid flows.
We keep only the volumes where fluid flows and delete others.

Fluid volumes:

PID no 24