How to Use Sim CFD (to your advantage): A Primer for Computational Fluid Dynamics

How to Use Sim CFD (to Your
Advantage)
- A Primer for Computational
Fluid Dynamics
Jim Swain Dave Graves
Synergis Autodesk

How to Use CFD
• When to apply simulation tools in a product development project.
• See a basic CFD workflow for consumer electronics cooling.
• Discuss basic CFD considerations for building design.
• See tools to prepare Inventor models for simulation.
We will be using Autodesk CFD 2016 and related products.

 Applications Consultant for
Synergis
 Simulation user:
 Designer
 Generalist
Jim Swain

 Channel Enablement Executive
for Autodesk
 Simulation user:
 Designer
 Simulation Generalist
 CFD Specialist
Dave Graves

 When is simulation traditionally performed?
 Completed design performance verification
 Failure analysis
When to Apply Simulation Tools?

 When can it save the most money???
 Early in the concept phase!!!
 Why?
 Parts haven’t been spec’d, or ordered
 Rough designs = less simplification time
 Comparing concepts for relative improvements
 Avoids “does it match our test lab results?”
When Should We Apply Simulation Tools?

CFD Workflow – The 3048 Meter View

 Open the (simplified) model in Inventor.
 Simulation tab
 Autodesk CFD 2016 > Active Model Assessment Tool
Inventor to CFD

 Setup the Analysis
 Prepare the model geometry
 Apply materials
 Apply boundary conditions
 Apply initial conditions
 Apply mesh settings
 Apply analysis settings
 Run the Analysis
 Explore the Results
Overall Workflow

 Apply materials
 Apply mesh settings
 Apply analysis settings
Setup

Setup

 Change to the Results tab
 Probably will have to hide the
outer shell.
 Don’t hide the working fluid!!!
 Can start checking results right
after the first iteration is complete.
Analysis Results

Mechanical Ventilation
 HVAC: Factories, Datacenters,
Hospital Rooms, Office Spaces,
Laboratories, Clean Rooms
 Smoke Extraction
 Chemical Spill Control
 Thermal Comfort
 Solar Loading
 Condensation on Windows
Typical AEC Models Studied with Simulation CFD
External Flow
 Wind Loading
 Smoke/Exhaust
 Flow control on
environment: Fences, walls,
courtyards
Natural Ventilation
 Passive building comfort
studies
 Large Atriums
 Condensation
 Internal/External
combinations

Sometimes it is better to start over!
 Architectural drawings are overly complex for CFD Simulations
 Start cleaning the geometry with the basic building geometry:
1. Open VG (Visual Graphics)
2. Turn off all layers
3. Turn on Walls, Floors, Roofs, Ceilings, Windows
4. Start your clean up there
5. Modify Geometry – Test Launch – Inspect Model – Test Mesh
Repeat 5 until geometry is satisfactory
Elements hidden from the active 3D view in Revit are not transferred into
Autodesk Simulation CFD.
Leveraging your Revit model in Simulation CFD

Model Complexity
Well-formed geometry with an appropriate level of detail is essential for an efficient AEC
simulation.
Architectural geometric models often include features that span a wide range of length scales.
Consider the effect and relevance of small geometric features on the overall simulation.
A detail item that is 1/8” long embedded in a 10,000 square foot interior space will require
mesh elements that are significantly smaller than the surrounding air volume. If the item is
included, the resulting model size is much larger due to the large element count, and run-
times are much longer as well.
• Remove or simplify small features on furniture or detailing.
• Either exclude or substitute features such as small diameter tubing, rounds, fillets, holes, handles, and
railings with a simpler representation.
Remove as necessary to
maintain simulation efficiency.

© 2014 Autodesk Autodesk Technical Academy 2014
Model Complexity

Revit Geometry
When Using Windows: Leverage Level of Detail (Coarse vs Fine)

Outcome:

Diffusers
Sidewall Slot DiffusersCeiling Supply
Most diffusers are built from scratch
Build the model with volumes, don’t use surfaces!
Customer have to build their own libraries in Revit

Furniture

Model Integrity
Inspect closely for interferences and small gaps.
The following techniques references Revit commands, but the strategy can be applied to any
CAD tool.
Ensure walls, floors, and ceilings meet cleanly. Avoid small overlaps or gaps.
• This prevents a high concentration of very small elements where these features meet.
• Causes meshing failure and poor results.
• To review details of the construction, use the Thin Lines view option.
• To ensure walls are cleanly lined up, use the Join and Align commands.
• Small interferences and gaps between structural elements (such columns and beams) and neighboring
geometry should also be considered
In the image, small interferences exist between structure and cladding around the outside of the
column and beams:

General Geometry Concerns
Finding Leaks
1. Create a volume around the entire model with the
External Volume Geometry tool in Autodesk Simulation
CFD.
2. Assign a solid material to all parts in the model. Assign
Air to the surrounding volume.
3. On the Solve dialog, click Results quantities, and enable
Stream Function. (This enables nodal aspect ratio as an
output quantity.)
4. To generate the mesh, set the number of iterations to 0
on the Control tab of the Solve dialog,, and click Solve.
5. After the mesh is complete, create an Iso Surface, and
show Nodal Aspect Ratio. The regions with the highest
Nodal Aspect Ratio are often the gaps.
Note: If this doesn’t mesh then you have major geometry
issues.

 Simplify tools in Inventor
 Shrinkwrap
 Simply
 Delete Face (Direct Edit)
 SimStudio
General Simplifying Tools

Automatic Model Diagnostics and Repair
Easily find and fix geometry integrity issues before they affect your mesh

Rapid Model Defeaturing and Simplification
Run simulations faster by eliminating unnecessary detail

Intuitive Simulation Feature Creation
Create sim-specific features like 2D shells, caps, etc.

© 2015 Autodesk, Inc. ATA 2015: Evolve to Drive Adoption
 Wrap almost any solid or surface geometry
 Creates a CFD volume mesh
CFD 2016 – Geometry and Meshing
Automated Surface Wrapper

 Early!!!
 Initial concept development
 Why: Verify design feasibility.
 Who: Project Engineer, Analyst
 Conceptual models
 Component development
 Why: Early design verification.
 Who: Project Engineer, Analyst
 Production models
Recap - When to Apply Simulation Tools?

 Questions?
 Thank you!
Conclusion

How to Use Sim CFD (to your advantage): A Primer for Computational Fluid Dynamics

More Related Content

Viewers also liked (12)

Similar to How to Use Sim CFD (to your advantage): A Primer for Computational Fluid Dynamics (20)

More from Synergis Engineering Design Solutions (20)

Recently uploaded (20)

How to Use Sim CFD (to your advantage): A Primer for Computational Fluid Dynamics