Until recently, fans were designed using essentially the same methods as 50 years ago. Typically, this involved hand calculations using airfoil design methods to estimate the performance of various blade design concepts. The problem with these calculations was that they required many simplifying assumptions, thus limiting their accuracy in practical applications. The result was that most real-world designs relied upon building and testing prototypes. Prototypes, however, take a considerable period of time to build and test and are also expensive. Moreover, the point measurements used to evaluate a prototype provided little information as to why a particular design performed well or poorly. Consequently, engineers were often forced to settle for less than ideal performance because they didn't have the tools to shoot for a truly optimized design.
CFD is an effective tool for generating detailed parametric studies, making it possible to evaluate far more design alternatives than the build and test method and thereby providing opportunities for optimization. Another advantage of CFD is that it provides more complete information than physical testing, including color-coded graphics that depict flow direction and velocity in all relevant locations. This helps designers gain more insight into the reasons why a design is performing as it is, which enables rapid design improvements.