Additive Manufacturing – Computational Fluid Dynamics

When designing new products, engineers must validate their decisions based on evidence they can gather around them (see article The Skill is in the Engineer). There comes a point in the design process where a decision must be made on which concept is worth developing, be it for economic, performance or aesthetic reasons. Before the digital age, engineers relied on crude assumption-based calculations and engineering intuition. Calculations and intuition can be improved through time-consuming trial and error, however, there are significant limitations in time and cost for this approach. Relatively recently, the engineer has acquired a new set of tools to inform such decisions in a way that is more accurate, time efficient and cost-effective. Such tools are simulation based models carrying out many billions of calculations a second, e.g. Computational Fluid Dynamics – CFD.

CFD is a tool used to simulate the 3-dimensional behaviour of a fluid, subject to specific conditions in a complex physical volume. The conditions are set from the operating environment of the component carrying the fluid, whilst the structure is created by the designer to ensure the fluid is travelling as efficiently as possible within the available design space.

In the Fluid Power industry CFD has proven to be an essential tool to the design engineer. Together with Additive Manufacturing (3D Printing, AM) design, it has enabled a high rate of both complex design iterations, and validation in meeting performance targets. An example of where this was applied can be found here.

Two Fluid Pathways in Printed Valve

The image above is an example of two fluid pathways found in part of a printed valve body. The complexity of these galleries and their near-endless adjustability means design efficiency is reliant on accurate modelling and a high number of iterations. At Domin Fluid Power, CFD is a cost saving tool. Iterative design can be carried out without the time and cost of making expensive physical prototypes, and real-world conditions can be simulated in the digital domain. To that end, Domin has created various CFD models for the dynamic simulation of pumps to observe cavitation risks, as well as static simulations of valves highlighting areas of inefficiency in fluid flow. The image below shows fluid streamlines in a static CFD model of a valve body.

Fluid Streamlines in a Static CFD Model

The iteration of designs can now be rapidly validated digitally, saving time and cost compared to when this had to be done with physical bench-tests. The image above describes one such example. It is part of a study of a miniature rotary actuated valve developed at Domin. CFD modelling led to a 40% reduction in torque from flow-force optimisation around the spool whilst maintaining flow capabilities. It is with the extensive use of modelling techniques such as those shown here, that Domin fluid Power designs and develops high performance products with the flexibility and complexity of AM.

When considering alternative solutions to a problem (whether it is meeting a flow target, or managing areas of stress for fatigue), a high turnaround-rate approach is essential when holistic design is carried out by a single engineer. In this regard, CFD is a step-change enabling process (See article Evolution or Revolution?) that is readily informative to the designer on which design path is best suited to meet the specification targets.

Minature Rotary Actuated Valve