The idea of 3-D printing works extremely well because it cuts down on very complex, high precision manufacturing methods that may not be amenable to mass production
An Indian scientist with Lockheed Martin Advanced Technology Laboratories, Shahrukh Tarapore, inspired by the maple seed has designed the unmanned aerial vehicle named Samarai.
The idea of 3-D printing works extremely well because it cuts down on very complex, high precision manufacturing methods that may not be amenable to mass production. Such UAVs have been used by the military for reconnaissance functions, or biological/agricultural studies, insect behaviour, weather forecasting and monitoring, to name but a few of hundreds possible applications.
The ink-jet printing that we all know well, is in a way precursor to 3-D printing of objects that can be manufactured at very high speeds, with precision and with full reproducibility.
The design is made on a workstation with advanced graphics using CAM/CAD software that is capable of analysing the product slice by slice and provide the input to the actual printer which builds up the layer using either some kind of processed paper or polymer powder that can solidify or get ‘cured’ at room temperature. This process has been around for more than three decades, but such laboratories are today combining far greater precision and faster output than ever before.
Researchers first built a computer-aided design (CAD) model of the original Samarai, fully parameterized in several dimensions—wing twist and feather angle—of known importance to mono-wing flight.
Initially, printing took nearly 12 hours; but refining the CAD model and optimizing the orientation of the part during printing substantially reduced printing times to approximately five hours, with further possible improvement.
The team again turned to the natural world for a solution. This time the butterfly's fine, semi-permeable wing—known as a gossamer wing—provided inspiration for a new parameter in the Samarai wing design.
The team added model parameters to hollow out sections of the airframe much like a four-pane window frame with the glass removed. The new design led to a 25 pc reduction in the weight of the wing and required less material and shorter print time.
To aid in model design and parameter selection, the team used computational fluid dynamics (CFD) simulations of the airframe built with a combination of in house models and the OpenFOAM CFD software package.
The original CAD model was used in a multi-scale methodology that leveraged CFD predictions of aerodynamic behaviour coupled to a multi-body dynamics solver to produce simulated flight dynamics for the vehicle. An efficient adaptive sampling methodology sampled the parameter space of flight conditions to minimize the required number of CFD simulations.
Today, these simulations compute the rotations per minute and propeller motion required to reach a near-hover regimen. As model parameters are varied, expected behaviour does not appear to be monotonic.
This speaks to the complexities of mono-wing flight dynamics, including its interaction with the environment. The team will continue to leverage the complement of simulation and empirical analysis using 3D printing to further understand the Samarai's flight dynamics.
(Max Babi is a metallurgist and tech enthusiast. The views expressed by the author are his own and not of CIOL)