#rotating component

Computational Fluid Dynamics (CFD) is a perfect tool for studying rotating components. A glance at such disparate machines such as pumps, table fans, axial fans for electronic cooling and hair dryers, shows that they all have one thing in common: rotating components.

Engineers who design equipment with rotating components need to analyze and understand the behavior of those components if they want to improve performance. For example; if the blades of the table fan are in the wrong shape or if they’re incorrectly oriented, the fan may generate little to no air.

CFD helps engineers study many of the issues involved in rotating component behavior. It provides a way to save a great deal of time and money in obtaining the necessary information, and assists engineers in designing better quality rotating equipment.

The use of CFD makes it possible to eliminate expensive physical prototypes, and find serious flaws much earlier in the design process. Starting with CFD basics, this article will give engineers an overview of how users of HiTech CFD can solve typical problems.

Several different approaches can be used to study flow in and around rotating equipment. In the majority of rotating machinery fluid-flow analyses, engineers model the flow in a steady-state manner. The term “steady-state” refers to a solution that does not vary with time.

A very simplified approach called Single Rotating Reference Frame, which assumes that the entire fluid domain or region rotates with the rotor or impeller, can be used to study the flow around the impeller blades. However, because this doesn’t consider any effects of the pump casing on the flow, it is insufficient for analyzing a full pump system.

To study the whole flow pattern and see the effects of the stationary pump casing, baffles, and other internal parts, users need more comprehensive methods, such as Multiple Rotating Reference Frame, also a steady-state approach, the engineer assigns zero revolutions per minute (RPM) to nonrotating components, called stators, and fixed RPMs to the rotating components, called rotors. With this method, users can consider more than one rotor, each rotating with a different RPM.

The Sliding Mesh method is a transient approach that is useful for rotating flow problems requiring a time-accurate solution for computing the unsteady flow field. It requires a very large number of time steps to arrive at the transient solution, making the process time-consuming as well as computationally demanding, and may turn out to be impractical on desktop computers.

HiTech CFD Simulation uses both the single and multiple rotating reference frame approaches to solve rotating flow problems. Overall, the program employs configuration-based fluid-flow analysis coupled to SolidWorks software assembly configurations to enable a wide variety of “what if” scenarios. Every flow study either creates a new configuration or can link to an existing SolidWorks software configuration. The software aims to solve the majority of possible rotating equipment problems, and to do so quickly. For the sake of speed, HiTech CFD Simulation does not use the transient approach.