Class notes
Introduction to Computational Fluid Dynamics
- Course
- Institution
Introductory course to the software and governing theory of computational fluid dynamics (CFD)
[Show more]
Seller
Follow
pluckysugar
Content preview
Loughborough University20TTC102
Introduction to Computational Fluid Dynamics
Notes
1
, Lecture 1 - Introduction
What is Computational Fluid Dynamics?
• Solving discretised versions of the governing equations of fluid dynamics.
• In the last ~25 years CFD has gone from a research subject to a widely used design tool.
• Running computer simulations can solve time and money.
• Huge amount of data can be extracted and presented from CFD.
How does it work? – Finite Volume Method:
• You may be familiar with ‘Control Volume Analysis’
• Apply ‘Conservation’ laws to a defined volumed of fluid.
• Finite volume (FV) CFD can be thought of as extending this to a mesh or grid of cells.
Finite Volume Method:
• Properties such as velocity are stored in each cell.
• They are updated according to how much flows in and out of neighbouring cells.
• These flows or fluxes are determined by the cell values.
• So, we must iterate to find a solution.
2
,Initial and Boundary Conditions:
• Iterative procedure means we must start with an initial guess – known as Initial Conditions.
• We must also know what happens at the edge of the grid – these flows must be user specified
and are known as Boundary Conditions.
• These can often be confused – make sure you know which is which (and where to find them
in a CFD package)
Post-Processing – What does CFD give us?
• This is the name given to the job of taking the stored result in the memory of the computer
and making sense of it.
• Modern CFD packages can produce a wide variety of line plots, contours, vectors and
isosurfaces.
• Animations an also be produced.
Post-Processing – Contour Plot:
• A value is stored for each cell – a colour can be assigned to a value range and then the colours
displayed on the mesh.
Post-Processing – Vector Plot:
• The previous slide showed colours to represent just one component of velocity. Use an arrow
to show direction + magnitude.
• Streamlines are used to show flow direction. They show the path that would be taken by a
very light particle in the flow. Here they are combined with a surface contour of pressure on
an aircraft.
Post-Processing – Line Plot:
• Picking a line through the simulation can be used to show how a property varies in one
direction.
• Useful for comparing with experimental data for example.
Post-Processing – Isosurfaces:
• An isosurface is a surface made up of points which all have the same value.
• This can be used to show 3D details in a flow.
• Can be coloured by temperature.
3
, Post-Processing – Derived Properties:
• CFD solutions can also be visualised by plotting derived properties of the flow.
• In reality, the flow field is defined as using the three instantaneous velocity components, but
other properties can be defined based on this.
• These properties can be plotted in CFD and used to gain extra understanding of the flow.
• Another example of a derived property is vorticity. Which can be derived by taking
derivatives in space of the velocity field.
• One way to visualise this is by plotting derivatives of the ‘Q-criterion’ which is related to
vorticity – this shows the location and shape of vortex cores.
Processed Data:
• Knowing the value of properties in each cell means we can process data to find more
information.
• E.g., pressure is calculated in each cell
o For a cell next to a solid surface, we can use this to find the force exerted on the
surface.
o This can be summed for all cells next to a wall.
o Gives us drag, lift or even pitching moment.
• Other information can be found in a similar way.
• ‘Derived’ properties can be found.
• Gives us details that experiments cannot.
Integration with other simulation methods:
• A current area of research and development in CFD is to couple fluid dynamics predictions
with other physics – E.g., vehicle handling model for cross wind stability prediction.
Steps to produce CFD results:
1. Define Geometry
2. Mesh Geometry
3. Choose equations and models
4. Specify boundary conditions
5. Run
6. Analyse results
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller pluckysugar. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.18. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
64438 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now