Computational Fluid Dynamics with Geometry-Based Methods

The accuracy of simulation results depends on the quality of the mesh used to represent the actual geometry. Historically, computational fluid dynamics (CFD) simulations have relied on mesh-based approaches.

Using a geometry-based approach has several key advantages over traditional methods. The simulation tools on 3DEXPERIENCE enable you to work faster with the same accuracy we know and love from mesh-based approaches.

What is the Mesh-Based Approach?

In a mesh-based approach, users create a computational grid around the geometry, and the volume of mesh serves as the foundation for solving fluid flow equations. While effective, this process is time-consuming and often limits agility in design iterations. When speed and accuracy are critical to keep up with product innovation, we cannot afford to lose time in the meshing phase of simulation.

What is the Geometry-Based Approach?

In the geometry-based approach, the necessary simulation features are assigned to a simulation volume that represents the region where fluid flow is to be analyzed. This method represents a significant advancement in how engineers approach fluid dynamics calculations, offering a more intuitive and efficient workflow.  The geometry-Based Method eliminates the dependency on traditional meshing by directly leveraging the CAD geometry for simulation.

How 3DEXPERIENCE Simulation Leverages the Geometry-Based Approach

The Fluid Dynamics Engineer (FMK) role on the 3DEXPERIENCE platform recently introduced a geometry-based method for defining flow volumes in fluid mechanics simulations. The Geometry Idealization Essentials app is used to create a simulation volume.

For this, an abstraction shape is defined to create a copy of the model. Thereafter, depending on the type of flow analysis, an appropriate volume is extracted to define the simulation volume.

There are three types of extracted volumes: interior, exterior, and conformal. The type depends on the geometry present and the type of fluid flow simulation.

• For internal flow analysis, the interior volume extracted should represent the fluid volume of interest inside the model.
• For external flow simulation,  an exterior volume that represents the fluid volume of interest around the model is extracted.
• If the model contains interfaces between parts that interact with any interior or exterior volumes, a conformal volume is extracted. A conformal volume extraction results in solid volumes that prioritize the overlapping interfaces based on mesh simplicity.

Steps to Setting Up a CFD Study with Geometry-Based Methods

1. Geometry Preparation
   The first step involves preparing the geometry for simulation. For internal flow analysis, this includes defining lids to close any openings in the model and creating an enclosure to specify the area for volume extraction. If a surface with holes in it is selected, the lid creation tool will close all the holes on that surface. The same technique can be used to detect leaks in enclosed volumes.
   

   Preparing the models for the geometry-based method

2. Volume Extraction
   Once the geometry is prepared, the next step is to extract the flow volumes. This can include interior volumes, exterior volumes, conformal volumes, or wrapped volumes, depending on the specific requirements of the simulation.
   

   Extracted volumes for the computational fluid dynamics study

3. Physics Separation
   After extracting the flow volumes, the physics in each volume needs to be specified. This includes assigning the simulation volume to previously extracted flow volume, defining physics domains, materials, and other aspects, such as the type of flow analysis.
   

   Defining a Simulation Volume

4. Mesh Creation
   The final step before running the simulation is to mesh the geometry. This ensures that the simulation can accurately capture the fluid dynamics within the defined volumes.
   

   A generated geometry-based mesh for an external flow study

Key Considerations for a Computational Fluid Dynamics Study

When working with CFD tools on 3DEXPERIENCE, there are a few considerations to keep in mind.

• If a model contains interfaces between parts that interact with any interior or exterior volumes, a conformal volume is extracted. A conformal volume extracts an interior fluid volume and the solid volumes of the model.
• For external analysis, the bounding geometry is defined using the Enclosure tool.  Enclosures can be a shell of a box, cylinder, or sphere around the model to represent the extent of exterior fluid volume.
  

  An external volume defined around a drone

• The Fluid Scenario setup includes defining initial conditions, boundary conditions, and any other parameters required for simulation. It is important to keep these as true-to-life as possible for accurate results.
• The app renders solid volumes in different colors so you can easily identify them in the study.

Mesh-Based vs Geometry-Based Methods

The traditional mesh-based method involves defining the location of flow volumes using parts, openings, and regions, and then creating the flow volumes during the meshing process. While this method provides access to more workflows compared to the geometry-based method, it can be more complicated to use.

The geometry-based method, on the other hand, simplifies the process by focusing on geometry preparation and volume extraction, making it a more user-friendly option. By simplifying the process workflows, this method enables engineers to perform routine fluid calculations more efficiently so that they can focus more on design improvements and innovative concepts, leading to faster time to market.

Looking to streamline your computational fluid dynamics studies with new techniques? Contact us here.