Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computational fluid dynamics (CFD) is the use of applied mathematics, physics and computational software to visualize how a gas or liquid flows -- as well as how the gas or liquid affects objects as it flows past. Computational fluid dynamics is based on the Navier-Stokes equations. Computational Fluid Dynamics (CFD) plays an important role in modelling and design of positive displacement screw machines. It is used mainly to identify and quantify effects of internal flows which cannot be modelled by use of other methods. Several areas of CFD applications includes architecture, chemical and process engineering, electronics and computer, HVAC (heat, ventilation &cooling), petroleum, train design, turbo machinery etc. Its physiological applications includes cardiovascular flow (Heart, major vessels), flows in lungs and breathing passages. Computational fluid dynamics (CFD) started in the early 1970s, triggered by the availability of increasingly powerful mainframes. CFD became an acronym for the combination of physics, numerical mathematics, and, to some extent, computer sciences all employed to simulate fluid flows.