Wednesday, October 13, 2010

What is Computational Fluid Dynamics (CFD)?














1. Definition of CFD


CFD stands for Computational Fluid Dynamics. It means predicting physical fluid flows and heat transfer using computational methods. 

Fluid flows are encountered in virtually all areas of industry, especially during the manufacturing and operation of various machinery and components that we encounter. For example, the automotive sector includes a whole world of different fluid and heat transfer mechanisms, such as cooling, combustion, ventilation and aerodynamics. Understanding how all these fluid and heat transfer mechanisms work is important for engineers and scientists to improve the operation of the mechanism and reduce its impact on the environment. Using CFD software, they are able to build a virtual prototype of a product design they wish to analyze and get data and images allowing them to predict the performance of that design.

2. Where is CFD used?

CFD is used in an extremely wide range of industries. Any industrial process that involves fluid flow and/or heat transfer can benefit from CFD analysis. Below is list of industrial and academic areas where CFD is commonly used.

  • Aerospace: Aerodynamics, wing design, missiles, passenger cabin
  • Automotive: Internal combustion, underbody, passenger comfort
  • Biology: Study of insect and bird flight
  • Biomedical: Heart valves, blood flow, filters, inhalers
  • Building: Clean rooms, ventilation, heating and cooling
  • Civil Engineering: Design of bridges, building exteriors, large structures
  • Chemical Process: Static mixing, separation, reactions
  • Electrical: Equipment cooling
  • Environmental: Pollutant and effluent control, fire management, shore protection
  • Marine: Wind and wave loading, sloshing, propulsion
  • Mechanical: Pumps, fans, heat exchangers
  • Meteorology: Weather prediction
  • Oceanography: Flows in rivers, estuaries, oceans
  • Power Generation: Boilers, combustors, furnaces, pressure vessels, nuclear
  • Sports Equipment: Cycling helmets, swimming goggles, golf balls
  • Turbomachinery: Turbines, blade cooling, compressors, torque convertors

3. How is CFD used?

Within the list of industries and applications listed above, CFD can include any of the following phenomena and flow regimes:

  • Laminar/turbulent flow
  • Subsonic/Transonic/Supersonic/Hypersonic flows
  • Newtonian/Non-Newtonian fluid
  • Multiple fluids, mixing and phase changes/mass transfer
  • Solid/fluid heat transfer, convection and thermal radiation
  • Combustion of gas, liquids and solids
  • Distributed resistances (porous media)
  • Fluid-Structure interaction
  • Aeroacoustics and noise prediction
  • Free-surface flows, surface tension effects
  • Time varying (transient) effects and moving boundaries
  • Electromagnetic, electrostatic, electrochemical and other effects
  • Casting, solidification and melting
4. What is the basic CFD process?
 
Pre-processing
1. Geometry/CAD/Solid model definition of domain
2. Surface cleanup/preparation
3. Volume mesh generation
4. Definition of boundaries and conditions
5. Physical property settings
6. Numerical controls

Solving
7. Perform computation using STAR-CCM+

Post-processing
8. Analysis of CFD results
9. Export results/Improve analysis   


5. How can CFD help me?

Improved product quality
Increasing product quality is a strategic objective of every company involved in product design or manufacture. Despite the fact that improvements in product quality are notoriously hard-won, increased product quality is the most frequently achieved benefit of using CD-adapco’s CFD technology.

Reduction in the number of physical prototypes
The traditional product development process is built upon on an iterative “design-build-test” principle in which the influence of successive design changes is quantified by experimentation on a physical mock-up of the product. Increasingly, CFD is being used to replace some of these physical tests, reducing the number of physical prototypes required in the product development process and replacing a number of ‘design-build-test’ iterations with much quicker ‘design-simulate’ iterations.

A faster time to market
A faster-time-to-market is an obvious benefit of reducing the amount of physical prototyping required to bring a product to fruition, but also a direct benefit of the availability of CFD simulation data early in the design process. This allows designers to rapidly eliminate poor design variants, allowing them to focus their efforts on a smaller number of potentially more productive designs.
Fewer field failures and avoided product recalls
Although product recalls are rare, when they do occur, the cost can be enormous, in direct financial terms (the cost of executing the recall, performing repairs, providing replacements and compensating consumers), but more importantly in terms of lost reputation. CD-adapco’s clients indicate that they have reported fewer product failures as a result of applying CFD.
Increased satisfaction of external customers
Customer satisfaction is the bigger picture. While the benefits of CFD listed above might help to increase margins and satisfy internal customers, the biggest benefit of any process improvement occurs when it makes a tangible difference to the end user of the product.
Multiple benefits
Realised individually, any of the benefits described above is likely to yield significant bottom-line benefits for an organization that successfully adopts CFD or CAE technology. However, the real benefit of CFD simulation is that even if you are seeking to realise a single specific benefit, the ancillary benefits of increased engineering insight will inevitably lead to a better overall product. 

- Source cd-adapco



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