CFD is predicting what will happen, quantitatively, when fluids flow, often with the complications of:

• simultaneous flow of heat,
  [*]mass transfer (eg perspiration, dissolution),
  [*]phase change (eg melting, freezing, boiling),
• chemical reaction (eg combustion, rusting),
  [*]mechanical movement (eg of pistons, fans, rudders),
  [*]stresses in and displacement of immersed or surrounding solids.

Knowing how fluids will flow, and what will be their quantitative effects on the solids with which they are in contact, assists:-

• building-services engineers and architects to provide comfortable and safe human environments;
• power-plant designers to attain maximum efficiency, and reduce release of pollutants;
• chemical engineers to maximize the yields from their reactors and processing equipment;
• land-, air- and marine-vehicle designers to achieve maximum performance, at least cost;
• risk-and-hazard analysts, and safety engineers, to predict how much damage to structures, equipment, human beings, animals and vegetation will be caused by fires, explosions and blast waves.

CFD-based flow simulations enable:-

• metropolitan authorities need to determine where pollutant-emitting industrial plant may be safely located, and under what conditions motor-vehicle access must be restricted so as to preserve air quality;

• meteorologists and oceanographers to foretell winds and water currents; - hydrologists and others concerned with ground-water to forecast the effects of changes to ground-surface cover, of the creation of dams and aquaducts on the quantity and quality of water supplies;

• petroleum engineers to design optimum oil-recovery strategies, and the equipment for putting them into practice;

• ... and so on.

Within a few years, it is to be expected, surgeons will conduct operations which may affect the flow of fluids within the human body (blood, urine, air, the fluid within the brain) only after their probable effects have been predicted by CFD methods