Go With The Flow

More and more, engineers are turning to computer simulations to solve a wide range of fluid-flow issues in appliance design. CFD simulation software used to develop airflow patterns in lawn mowers lets engineers see: (a) velocity vectors colored by velocity magnitude, as well as a (b) simulation of the rotors showing velocity vectors colored by velocity magnitude, (c) static pressure profiles, (d) and turbulent kinetic-energy profiles. Cross-flow zones develop between blades in a mower housing in a simulation at Frigidaire. CFD simulation shows the velocity profile and temperature profile in the insulation and cooling air vent between a Maytag oven liner and the side panel. Just as engineers began using finite-element analysis and other analytical tools for structural design, the last several years have seen appliance design engineers turn to computer simulation to optimize fluid flow. New modeling techniques, such as Computational Fluid Dynamics (CFD), let engineers accurately model the performance of design concepts without having to build a prototype. In the past, fluid-flow issues were addressed using trial-and-error procedures, such as hand calculations or experimental methods. However, designing, building, and testing prototypes takes time and can be expensive. Moreover, techniques used to evaluate prototypes provided little information as to why a particular design performed as it did, whether good or bad. Engineers often settled for less than perfect performance because they didn't have the tools for a truly optimized design. Simulation software, nonetheless, makes it possible to evaluate many designs at lower costs and with shorter lead times, often providing more design data than physical testing. CFD is said to be the most popular software tool in appliance design because it characterizes fluid velocity, as well as pressure and temperature values throughout the solution domain, including complex geometries and boundary conditions. In fact, a designer may change the system's geometry