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What is CFD ?

The physical state of any fluid (gas or liquid) is governed by three fundamental principles - conservation of mass, Newton's second law and conservation of energy. Computational fluid dynamics (CFD) is the application of computers to solve the equations which are derived from the above three principles.

CFD emerged about 40 years ago in the aerospace industry, and it has since matured to become a vital tool for many industries for whom fluid flow prediction is important. CFD is now a sophisticated and powerful analysis technique which, in addition to predicting fluid behaviour, can predict important processes such as surface heat transfer, chemical reaction (such as combustion) and stresses in interacting solids. 		model building/boundary condition set-up

slice through a simple cartesian mesh (several grid lines omitted to avoid clutter)

CFD works by dividing the domain of interest into a series of small discrete volumes using a mesh or grid. The physical properties of the fluid, such as temperature or velocity, are calculated at a single point within each of these volumes as a solution to the governing equations.

The physical properties of the fluid are driven by the temperatures and velocities of immersed solid objects and the known properties of the fluid as it enters the domain of interest. Any additional heat or momentum sources can also be added to the model.

The range of applications of CFD is huge. From high speed such as aircraft and cars, to low speed such as air-flow within buildings. From small-scale such as combustion chambers, to large-scale such as the Earth's atmosphere. The fluid of interest may be for example air, water, oil or a mixture of several types.
In general, the strengths of CFD for engineering design are:
  • CFD is the only tool which can predict fluid properties in fine detail within the space of interest.
  • Hard scientific evidence for/against designs.
  • Rapid prototyping allowing relatively cheap analysis of design modifications.
  • Visually appealing presentations and animations showing features such as temperature contours and air flow speed, which are readily understood by the non-specialist.
  • Beneficial and cost-effective process when used by specialists who have the expertise to produce and interpret the results.
slice through flowfield showing temperature-coloured vectors/temperature contours

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