What is CFD?
• The equations governing fluid flows are a set of coupled, non-linear partial differential equations (i.e. a type of differential equation, involving an unknown function (or functions) of several independent variables and their partial derivatives with respect to those variables.)
Continuity
Momentum
• Many real problems include additional terms and/or equations, governing heat transfer, chemical species, turbulence models, etc.
• Analytic solutions are known only for a few very simple laminar flow cases.
• An alternative is to “solve” the governing equations numerically, on a computer.
• Computational Fluid Dynamics (CFD) is this process of obtaining numerical approximations to the solution of the governing fluid flow equations.
• Many modern engineering systems require a detailed knowledge of fluid flow behaviour.
• Experiments provide useful data, but are often costly and time-consuming. It can also be difficult to measure the details required:
Measurement probes may disturb the flow excessively, and/or optical access may not be convenient.
Obtaining the correct parameter scaling may be difficult.
Reproducing some flow conditions safely (eg. explosions) may be difficult.
• Empirical correlations can be useful for simple problems – or first estimates – but are usually not available or applicable for complex problems.
• Note the use of the word “approximations”: all CFD solutions have some error associated with them.
• CFD does not remove the need for experiments: numerical models need to be validated to ensure they produce reliable and accurate results.
• With the growth of available computing power it has become possible to apply CFD even to very complex flowfields, giving detailed information about the velocity field, pressure, temperature, etc.
• The key to successful use of CFD is an understanding of where the errors come from; their implications, and how to ensure they are small enough to be acceptable in a particular application.
• The main aims of this course are thus to:
Provide an overview of the processes involved in CFD
Give an understanding of some of the key concepts in CFD
Provide an understanding of how to carry out simple CFD simulations from the beginning to the end using practical sessions
CFD Applications
• Power and energy: Nuclear Reactors, Wind Turbines, Marine Current Turbines
• Environmental: Dispersion of pollutants in air or water, wind microclimate
• Building services: Ventilation of buildings, atrium design
• Automotive: Aerodynamics of cars, aeroplanes, trains
• Health and safety: Investigating the effects of fire and smoke
• Process industry: Mixing vessels, chemical reactors
• Electronics: Heat transfer within and around circuit boards
and many more!