Meshing has a significant role when it comes to the engineering simulation process. Creating a high-quality mesh is one of the most critical factors that should be considered to ensure simulation accuracy.
WHAT IS MESHING?
Meshing is the process in which the continuous geometric space of an object is broken down into thousands or more of shapes to properly define the physical shape of the object. The more detailed a mesh is, the more accurate the 3D CAD model will be, allowing for high fidelity simulations. Meshing, also known as mesh generation, is the process of generating a two-dimensional and three-dimensional grid; it is dividing complex geometries into elements that can be used to discretize a domain. Since meshing typically consumes a significant portion of the time in acquiring simulation results, advanced automated meshing tools can provide faster and more accurate solutions.
WHY IS MESHING IMPORTANT?
Creating the most appropriate mesh is the foundation of engineering simulations. The mesh influences the accuracy, convergence, and speed of the simulation. Computers cannot solve simulations on the CAD model’s actual geometry shape as the governing equations cannot be applied to an arbitrary shape. Mesh elements allow governing equations to be solved on predictably shaped and mathematically defined volumes. Typically, the equations solved on these meshes are partial differential equations. Due to the iterative nature of these calculations, obtaining a solution to these equations is not practical by hand, and so computational methods such as Computational Fluid Dynamics (CFD) are employed.
WHAT ARE THE DIFFERENT TYPES OF MESHING?
Creating the most appropriate mesh is the foundation of engineering simulations. Ansys Meshing appropriately adapts to the type of solutions that will be used in the project and sets the respective criteria to create the best suited mesh. For a quick analysis or for the new and infrequent user, a usable mesh can be created in a few short steps. Where possible, Ansys Meshing automatically takes advantage of the available cores in the computer to use parallel processing and significantly reduces the time it takes to create a mesh.
BEST PRACTICES FOR SIMULATING FLUID MODELS
1. USE GEOMETRY WRAPPING TO CREATE WATERTIGHT FLUID MODELS
The geometries that design engineers send to analysis engineers are rarely clean enough to import into a fluids modeling program. Fixing these gaps and leaks in the geometry can traditionally take hours, even days.
Therefore, you (as the analysis engineer) should use a CFD software that can wrap a surface mesh around discontinuous geometry. This automated meshing capability will quickly fill in all the gaps, leaving more time for simulation and results analysis.
2. COMBINE OVERLAPPING GEOMETRY TO QUICKLY CREATE A FLOW BOUNDARY
To perform a fluid analysis, an inverse fluid volume needs to be created. You can create a fluid volume by wrapping a box around watertight geometry and combining all the overlapping faces between the solids into one face.
This resolves the intersections between the box and source geometry. The volume can then be extracted and imported into a fluids model.
You can use the “share topology” function to create the flow geometry using Ansys SpaceClaim. With Fluent’s “surface mesh” operation, you can extract the flow volume from the void between the boundaries in the geometry.
3. CONFORMALLY CONNECT MESHES TOGETHER TO AVOID GAPS
You can reduce computational times by creating fluids models with coarse meshes for large areas and finer meshes for more detailed geometries. The challenge then becomes linking these disparate meshes into a continuous mesh or sacrificing accuracy by creating non-conformal (mismatching) mesh interfaces.
Conformally linking meshes is a tedious job. It typically requires cleaning up the geometry and manually correcting the meshes so everything fits nicely together.
How do you leverage different meshing approaches and element types in a single mesh?
The concept of subdividing a geometry into multiple meshed bodies to leverage strengths of different meshing approaches has existed for a long time. The process of connecting different meshes (whether conformal or not) had varying levels of automation available to the user. Past approaches, even when automated, were often limited to element type variation on a global level. This resulted in conformal and non-conformal connections between large separately meshed regions.
Recent updates to Fluent Meshing take the concept of “The right mesh for the right” job to the next level by introducing Mosaic Meshing. Ansys Fluent’s Mosaic-enabled meshing technology can automatically generate different mesh and element types in different localized or global regions and link these grids conformally. This approach currently results in a poly-hexcore mesh leveraging the following element types as needed:
- Hexcore (Hex Elements with Cut-Cell Refinement)
- Polyhedral Elements
- Wall Inflation (Inflated Poly and Prisms)
It automatically blends between these element types to give you a mesh which is optimized for accuracy and meshing speed. The resulting mesh will have an inflated boundary layer near the walls and a hexahedral core in the fluid free stream. The two regions (near wall and free stream) will then be blended with a layer of polyhedra. This novel approach means a user is be able to quickly obtain a highly robust, high quality mesh optimized for accurate and stable solutions.
For more information about how Ansys Software can benefit you, contact us.