how to use sim cfd (to your advantage): a primer for computational fluid dynamics
TRANSCRIPT
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How to Use Sim CFD (to Your
Advantage)
- A Primer for Computational
Fluid Dynamics
Jim Swain Dave Graves
Synergis Autodesk
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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.
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Applications Consultant for
Synergis
Simulation user:
Designer
Generalist
Jim Swain
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Channel Enablement Executive
for Autodesk
Simulation user:
Designer
Simulation Generalist
CFD Specialist
Dave Graves
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When is simulation traditionally performed?
Completed design performance verification
Failure analysis
When to Apply Simulation Tools?
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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?
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CFD Workflow – The 3048 Meter View
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Open the (simplified) model in Inventor.
Simulation tab
Autodesk CFD 2016 > Active Model Assessment Tool
Inventor to CFD
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Active Model Assessment Tool
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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
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Prepare the model geometry
Apply materials
Apply boundary conditions
Apply initial conditions
Apply mesh settings
Apply analysis settings
Setup
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Prepare the model geometry
Setup
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Setup
Apply materials
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Setup
Apply boundary conditions
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Setup
Apply initial conditions
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Setup
Apply meshing
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Solve
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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
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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
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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
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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.
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© 2014 Autodesk Autodesk Technical Academy 2014
Model Complexity
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© 2014 Autodesk Autodesk Technical Academy 2014
Revit GeometryWhen Using Windows: Leverage Level of Detail (Coarse vs Fine)
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© 2014 Autodesk Autodesk Technical Academy 2014
Outcome:
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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
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© 2014 Autodesk Autodesk Technical Academy 2014
Furniture
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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:
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© 2014 Autodesk Autodesk Technical Academy 2014
General Geometry ConcernsFinding 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.
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Simplify tools in Inventor
Shrinkwrap
Simply
Delete Face (Direct Edit)
SimStudio
General Simplifying Tools
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Automatic Model Diagnostics and RepairEasily find and fix geometry integrity issues before they affect your mesh
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Rapid Model Defeaturing and SimplificationRun simulations faster by eliminating unnecessary detail
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Intuitive Simulation Feature CreationCreate sim-specific features like 2D shells, caps, etc.
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© 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 MeshingAutomated Surface Wrapper
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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?
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Questions?
Thank you!
Conclusion