Computational Fluid Dynamics, or CFD, is a scientific and engineering discipline which involves the numerical solution of the equations of fluid motion using digital computers.
Multi-dimensional and time-resolved, CFD simulations make it possible to visualise, quantify and analyse fluid phenomena within or around objects (systems) of interest. CFD software can be seen as the virtual equivalent of a physical wind tunnel.
CFD deals with fluid including all combinations of physical phases, gaseous, liquid, or solid as long as they 'flow'. The energy equations may also be solved for, which makes it possible to calculate all relevant thermal values where heat transfer or chemical reactions may occur.
Starting from a geometric model of the system and information about the operating conditions, CFD simulations can be used to obtain a wide variety of data such as temperature, the distribution of pressure or of chemical concentrations inside the system.
Unlike other reduced modelling techniques, CFD is based on the numerical solution of the Navier-Stokes set of fundamental and general equations of fluid motion and heat transfer, from first-principles. These equations can be solved analytically only for simplified problems. However, using computational techniques, they can be solved to deliver three-dimensional simulations of complex fluid flow events that account accurately for topological detail and operational characteristics.
THE COMPONENTS OF CFD
CFD brings together multiple disciplines. With physics, fluid dynamics, heat transfer and combustion at its core to establish the partial differential equations and physical models, it is supported by numerical analysis to derive stable and accurate methods to solve the equations numerically.
It also harnesses both computer science and software programming to code the methods and ensure that the resulting software is optimised for complex tasks such as speed on multi-processors machines, memory usage, and varied platforms.
CFD includes a very strong visualisation element. Visualisation is used to give a physical representation to raw output data, which otherwise would be difficult to understand on its own, eg. values of pressure at different locations. It can include post-processing contour plots or streamlines, or animations of fluid motion very similar or even superior to what would be observed in a physical experiment. Such post-processing is key to extracting relevant information and insights about the problem at hand from CFD simulations.
Prime examples of applications are the simulation of the flow of air around automobiles and airplanes to study their aerodynamics. Heat exchanges in an office building or a passenger compartment, the performance of a wind turbine and its siting, or the propagation of a shock wave are all areas which can be investigated with CFD techniques.
As the notion of fluid is also generalised to all physical phases, as long as they 'flow', an engineer may also use CFD techniques to investigate multi-phase, multi-species and reactive flow problems. Examples include the combined flow of oil, water, gas, and sand particulates in a pipeline, or calculating the temperatures in an internal combustion engine, where fuel may be injected as a liquid spray to evaporate and react with the air. To see some examples of Renuda’s application of CFD, click here to read in Projects.
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