### Why CFD?

Fluid dynamics is the science of fluid motion. Fluid flows are commonly studied in one of the 3 ways:

❶ Theoretical fluid dynamics,

❷ Experimental fluid dynamics,

❸ Numerically: Computational Fluid Dynamics.

### What is CFD?

Computational fluid dynamics, commonly shortened as CFD, is a subdivision of fluid mechanics that utilizes numerical methods and algorithms to solve and analyze problems that involve fluid flows. CFD is the science of predicting fluid flow, heat transfer, mass transfer, chemical reactions, and associated phenomena by solving mathematical equations, governing these processes using numerical approaches. CFD permits scientists and engineers to perform numerical experiments (i.e. computer simulations) in a virtual flow laboratory.

### What is a fluid flow?

Fluid flows encountered in everyday life include:

❶ Interaction of various objects with the surrounding air/water (aerospace automotive and marine applications).

❷ Complex flows in heat exchangers, chemical reactors, and furnaces.

❸ Combustion in automobile engines and other propulsion systems.

❹ Heating, ventilation and air conditioning of buildings and vehicles.

❺ Environmental hazards (air pollution, transport of contaminants).

❻ Film coating, thermoforming in material processing applications.

❼ Processes in the human body (blood flow, breathing).

CFD does not substitute the measurements entirely, but the amount of experimentation and the overall cost can be reduced significantly. Equipment and personnel are expensive and difficult to transport. CFD simulations are relatively inexpensive, and costs are likely to decrease as computers become more prevailing. CFD provides an insight into flow patterns that are difficult, expensive or impossible to study using traditional (experimental) methods. CFD simulations can be performed in a short period of time. This quick turnaround means that engineering data can be presented early in the design process. CFD permits better control over the physical process and offers the capability to isolate specific phenomena for study. Experiments only allow data to be extracted at a limited number of locations in the system (pressure and temperature probes, heat flux gauges). CFD allows the specialist to inspect a large number of locations in the region of interest and yields a comprehensive set of flow parameters for examination. CFD solutions depend upon physical representations of real-world processes (turbulence, compressibility, chemistry, multiphase flow). The CFD solutions can only be as accurate as the physical models on which they are based. The accuracy of the CFD solution is only as good as the initial/boundary conditions provided to the numerical model.