Week 3 Challenge : CFD meshing on Turbocharger
AIM :
To perform the surface and volume mesh for the given turbo charger model.
OBJECTIVE :
- To check for any geometrical errors present in the given model and to do the respective topological clean up.
- To assign PIDs( Property identifier) for each of the components in the given model.
- To do the surface mesh with mesh element type as 'Tria' and mesh target lengths for each PIDs as,
- 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
- Finally, To perform the volumetric mesh in the fluid domain regions (CFD analysis) of the given model.
Tools used :
MENUBAR>Drawing Styles>Shadow - This flag turns on and off the shadow drawing style.
MENUBAR>Drawing Styles>Wire - This flag activates the wire model representation of the geometry and the FE-Model.
MENUBAR>Faces Draw>Cross Hatches - This flag activates and deactivates the visibility of Faces' cross-hatches. As this flag is activated, green isoparametric lines that lie on the visible Faces appear. If the Faces are linked Faces the color of the crosshatch is orange.
MENUBAR>Tools>Checks>Checks Manager - This function opens the Checks Manager. It is used to execute massively a number of checks.
MENUBAR>Tools>Checks>Geometry - This function locates geometrical problems of the model such as Unmeshed Macros, Unchecked Faces, Needle Faces, Collapsed Cons, Triple Cons, Overlaps and Cracks.
MENUBAR>Tools>Checks>Penetration [Intersections] - This function checks all visible shell elements, macros, solids skin (the outer area of a solid volume), thick-shells, gaskets and all combinations of them to locate any intersections. For this check, the shell elements' thickness is not taken into account. The results are reported in the 'Checks' list window that appears.
MENUBAR>Faces Draw>Single - This flag activates and deactivates the visibility of single (red) CONS.
TOPO>CONS>Project - This function projects, as CONS or 3D Curves, a number of selected 3D-curves, CONS, element edges, line elements or Hexa Box edges on a number of selected Faces, in a user controlled direction. The selection of the CONS or 3D-curves can be assisted by the 'Corner Angle', 'PID Neighbs' for line elements or 'Path'.
MENUBAR>Utilities>Delete - The Delete function of the Geometry Group can be used to delete various ANSA entities (Curves, Faces, FE-Model entities etc.).
TOPO>Hot Points>Insert - This function creates or projects Hot Points by hovering positions on CONS or 3d curves or 1d FE elements.
MENUBAR>Utilities>Transform - This function is used to Translate, Rotate, Transform, Scale, Symmetry or Mirror selected entities (Faces, Points, Elements etc). The selected entities are copied in the new position.
Symmetry: This function creates symmetric entities. At the drop down menu there are the options to use the default symmetry plane or the current working plane or select from the screen the symmetry point, axis or plane that is going to be used.
TOPO>CONS>Fill Hole - This function fills holes on Faces. The holes can be of any shape. Such internal openings can be selected individually, or automatically among the visible ones if they fall below a user specified diameter value. There is the option to create automatically 3D Curves, Points or Connection Points of the removed holes, in order to mark their shape and position for reference.
TOPO>Hot Points>Project - This function defines a new Hot Point that lies on a CONS (or a Node on a 3D-curve) as the projection of an existing Node, 3D-point, Hot Point, Weld Spot etc.
This function also defines a new Weld Spot that lies on a face as the projection of an existing node, 3D-point etc. to this face.
TOPO>Faces>New - This function defines a new surface by selecting its boundary curves and creates a corresponding face that covers the new surface. The calculated surface appears as a net.
New [COONS] -
This function defines a new multi-patch Face and Surface, using the COONS interpolation principal. This is an easy way to define a new surface by its boundary curves. After the mathematical definition is finished, the calculated surface appears as a net. A relative window gives the ability to accept or to reject the calculated surface. When only three boundary sides are selected, there is the ability to choose between two alternative definitions for the fourth generated side, one is to be straight and the other is to have a shape similar to its opposite side.
New [EXISTING SURF] -
This function defines a new Face laying on an existing surface.
New [PLANAR] -
This function defines a new planar face. The underlying surface is automatically created.
New [FITTED] -
The FITTED option is used for the definition of a non-planar Face. The created Face fits to the selected boundaries.
MENUBAR>Feature Selection>Line Options>Loop - Selects a closed loop of edges, perimeters or curves. Any internal or external perimeter is considered a loop.
MENUBAR>Feature Selection>ENT - Selects any kind of entity (the kind of entity depends on the ANSA function which is in use) one by one or multiple entities by box selection.
MENUBAR>Feature Selection>Surface Options>PID Region - If the 'PID Region' flag is activated, then by picking an element (shell or solid) of a particular PID, ANSA automatically selects all the connected visible elements, which are assigned with the particular PID.
MENUBAR>Focus>Or - Keep visible only the selected entities.
MENUBAR>Focus>And - Select one or more already visible entities, in order to also bring to visible any neighbor entities which may exist.
MENUBAR>Focus>Not - Hide one or more selected entities.
MENUBAR>Focus>!Not - Select entities that will remain visible. The selected entities temporarily (during selection) are excluded from the visible ones, but as soon as 'Enter' or the middle mouse is pressed (selections' termination) then they will only be the ones to remain visible in the graphics area.
MENUBAR>Focus>Invert - Inverts the current visibility status. This means that visible entities become non-visible and non-visible entities become visible. If one or more Parts are Locked then this function operates exclusively in the Locked Parts.
MENUBAR>Focus>All - Bring to visible all entities of the database. If the Lock flag button is active, then the function brings to visible only the entities that belong to the active locked view.
If there are numerous stored locked views, then they will be displayed as a sub-options list of the All button.
MENUBAR>Focus>Lock - This function locks the current working area view. This working area view is kept locked until the flag is turned off. There is also the ability to store different kinds of views of the same model. The status and the content of the working area influence the result of the All function.
MENUBAR>Focus>Neighb - Logical operation that brings to visible all the 1st level neighboring items attached to the already visible ones.
TOPO>Faces>Topo - This function automatically creates topological conditions between selected adjacent CONS.
TOPO>Faces>Orient - This function sets a uniform orientation direction to all visible Faces according to the orientation of the majority of the Faces. The mesh elements that will be generated, or those already existing, also obtain a uniform orientation.
MENUBAR>Lists>Properties - This function facilitates property management. A list of the properties existing in the file is available. Management windows, such as this one, provide filtering, sorting and selection capabilities on the listed entities as well as definition of new entities.
MENUBAR>Utilities>Mesh Parameters - This function opens the 'Mesh Parameters' window, where the user can define the parameters for the Reconstruction, Reshape and Fix functions.
MENUBAR>Utilities>Quality criteria - Select and set the respective quality criteria for the corresponding elements to perform the Quality Checks (Hidden Mode). Also set the general presentation settings concerning the ANSA workspace.
MESH>Perimeters>Length - This function defines the element length on selected perimeter segments or macro areas. The element length may be explicitly declared or may be declared as a factor to be multiplied by the existing element length.
MESH>Mesh Generation>CFD - This function is recommended after the user has applied the Perimeters>Spacing(Auto CFD) on the selected perimeters.
This algorithm meshes with variable element length, depending on the local curvature of the underlying CAD surface, under tight user-controlled specifications. It generated the less possible elements taking into account all small details of the geometry. This algorithm is an advanced meshing algorithm tailor made to meet CFD specs or other application areas where a variable size mesh is required.
MESH>Macros>Freeze/Un - This function locks/unlocks the selected Macro Areas and their boundary segments. In this way, the Macro Areas' condition is stabilized and no participation to functions that might alter their topology or meshing (if any) is permitted. If any function tries to alter the Macro Area, or a Macro Area's component is selected to participate to another function, a relative message appears in the text window.
MENUBAR>Utilities>Measure - This function performs various measurements according to the corresponding Selection Mode. The applied measurements can be saved and viewed at a later stage.
VOLUME MESH>Volumes>Define[Auto Detect] - This function automatically defines multiple volumes using already meshed macros or FE-model mesh.
VOLUME MESH>Volumes>List - This function enables the handling of the defined volumes in the database.
VOLUME MESH>Unstructured Mesh>Tetra CFD - The Tetra CFD algorithm is most suited for geometries of thick volumes, large domains with significant variation in length of the surface mesh (say more than 2 orders of magnitude). Most met in CFD applications.
Activate Tetra CFD and select either one or more already defined volumes or some specific solid elements.
VOLUME MESH>Volumes>Remesh - This function repeats the volume-meshing procedure with the same meshing algorithm and element type on Volume Definitions that were previously meshed.
MENUBAR>Utilities>Cut Plane>New[Default XY] - Creates cutting planes by defining one point. The plane is parallel to the global XY and passes through that point.
MENUBAR>Utilities>Cut Plane>Flip - Flips the existing cutting planes together with the cut entities.
MENUBAR>Utilities>Snapshot - Take snapshots from the drawing area or from any ANSA window. Depending on the selected option the image can be: POSTSCRIPT, RGB, TIFF, JPEG, PNG or BMP.
PROCEDURE :
Step 1 : Open the given model into ANSA by using MENUBAR>File>Open
Step 2 : Perform the geometry and penetration checks under MENUBAR>Tools>Checks>Checks Manager, which will show the respective errors in the geometry after execution.
Step 3 : Resolve all the errors shown in the check manager by fixing or deleting it. In the below image, since there is a extended surface, it should be deleted, but before that the con from circular face is projected to the curved surface using TOPO>CONS>Project so that only the extended surface gets deleted.
Step 4 : Delete the below overlapping surface by seleting the respective PID from MENUBAR>Lists>Properties
Step 5 : By choosing the three point mirror face option under Symmetry using MENUBAR>Utilities>Transform, Create the below surface.
Step 6 : Use fill hole option under TOPO>CONS>Fill Hole to fill this hole.
Step 7 : Similarly, Create new faces using TOPO>Faces>New for the surfaces that have single cons.
Step 8 : Also, delete all the penetrating and overlapping surfaces which is mostly found in the shaft rotor region.
Step 9 : After resolving all the errors, recheck the geometry of the model under MENUBAR>Tools>Checks>Checks Manager
Step 10 : After resolving all the errors that is shown in the check manager, close all the openings in the model in order to perform volumetric mesh.
Step 11 : Assign respective PIDS to the each components of the given model using MENUBAR>Lists>Properties and delete any left over PIDs.
Step 12 : Give the mesh parameters and quality criteria, with maximum and minimum target lengths for Blade stage 1,2 and shaft rotor PIDs as 0.5 and 2mm respectively. Also, give the perimeters and macros length as 1mm for those PIDs which is described in the above problem.
Step 13 : Now, perform the surface mesh on those PIDs using MESH>Mesh Generation>CFD
Step 14 : In order to perform surface mesh for other PIDs with different mesh lengths, Use freeze option under MESH>Macros>Freeze/Un, to not change the mesh lengths for existing PIDs.
Step 15 : Give the required mesh parameters and quality criteria for the impeller PID as per the problem, the perimeters and macros length as 2mm and perform the surface mesh using CFD algorithm as before. Also, freeze this PID using MESH>Macros>Freeze/Un
Step 16 : Similarly, repeat the same for the remaining unmeshed PIDs with mesh length as described in the problem.
Step 17 : In order to perform volumetric mesh for the model, first, Auto detect the volumes in the model using VOLUME MESH>Volumes>Define[Auto Detect]
Step 18 : List all volumes that was detected above using VOLUME MESH>Volumes>List. Then, Delete the volumes that are not required for flow analysis( i.e, delete the volumes which are solid domains)
Step 19 : Define the type of mesh as 'Tetre CFD' in the left over volumes using VOLUME MESH>Unstructured Mesh>Tetra CFD . Now, Perform volumetric mesh by using VOLUME MESH>Volumes>Remesh
Step 20 : To get a cross sectional view, use MENUBAR>Utilities>Cut Plane>New[Default XY] and flip it.
RESULT :
The google drive link for the file is attached below,
https://drive.google.com/file/d/1-fRAtpXRs9nnnaIT86sOTsYaJGLAlC08/view?usp=sharing
The below image show the cross sectional view of the given turbo charger with surface and volumetric mesh,
CONCLUSION :
Hence, the volumetric mesh for the fluid domain is done for the given turbocharger model with 'Tetra elements' for the volume is 6709542 and for the surface meshed 'Tria elements' of 617782.