Fluid mechanics is the study of fluids (gases and liquids) either in motion or at rest and it is divided to major disciplines: fluid statics (fluids at rest) and fluid dynamics (fluid in motion). Computational Fluid Dynamics (CFD) is one of three branches of fluid dynamics dedicated to study of fluids in motion.
Experimental and theoretical (analytical) fluid dynamics were two widely practiced branches before 1970ís and 1980ís. Theoretical fluid dynamics involves solution of differential equations while Experimental fluid dynamics involves building a physical model and testing that model in a wind tunnel or other facilities. However, with advent of digital computer, a third approach was born.
The differential equations describing fluid dynamics problems are generally a system of non-linear partial differential equations with irregular boundaries, which are often too difficult to solve without the aid of computers. Additionally, experimental fluid dynamics often has to deal with challenges such as instrumentation, intrusive measurements, testing at small scale, high cost of model and testing, long fabrication lead-time, and limited information.
CFD is computer-based simulation of predicting what will happen when fluids (gases & liquids) flow and complements experimental and analytical approaches by providing an alternative cost-effective mean of simulating real-life flow problems.
CFD has now become a leading research, educational, and design tool. It is being used to better understand physical events and processes and perform numerical experiments (analogous to wind tunnel tests). As an education tool, CFD is used to understand concepts of fluid flow and expose students to expanded range of flow problems. Most importantly, CFD has now become a design tool by providing capabilities to facilitate design optimization, reduce design bottlenecks and improve engineering performance, enhance communications, and answer what-if questions.
CFD has become an essential tool to predict fluid motion, which may include heat and mass transfer, phase change, and mechanical movement of boundaries. CFD is now routinely used to solve complex flow problems in the aerospace, automotive, chemical, electronics, environmental, biomedical industries.