Autonomous air vehicles that can change shape during flight have been enabled through a fluid-structure interaction tool, which will be able to rapidly optimize the structural configuration for unmanned aerial vehicles while properly accounting for the interaction between air and the structure. The system will be capable of changing shape during flight, thereby optimizing performance of the vehicle through different phases of flight.

In surveillance applications, for instance, the vehicle may need to get quickly to a location and then stay there for as long as possible. During these segments, short wings are desirable in order to go fast and be more maneuverable but in cases where the vehicle loiters at one spot, long wings are desirable in order to enable low-power, high-endurance flight. This tool will enable the structural optimization of a vehicle capable of such morphing while accounting for the deformation of the wings due to the fluid-structure interaction.

One concern with morphing vehicles is striking a balance between sufficient bending stiffness and softness to enable morphing. If the wing bends too much, then the theoretical benefits of the morphing could be negated and also could lead to control issues and instabilities.

Fluid-structure interaction analyses typically require coupling between a fluid and a structural solver. This, in turn, means that the computational cost for these analyses can be very high — in the range of about tens of thousands of core hours — for a single fluid and structural configuration.

To overcome these challenges, researchers developed a process that decouples the fluid and structural solvers, which can reduce the computational cost for a single run by as much as 80 percent. The analysis of additional structural configurations can also be performed without re-analyzing the fluid due to this decoupled approach, which in turn generates additional computational cost savings, leading to multiple orders of magnitude reductions in computational cost when considering this method within an optimization framework.

While there have been advances in research in morphing aerial vehicles, what makes this system different is its look at the fluid-structure interaction during vehicle design and structural optimization instead of designing a vehicle first and then seeing what the fluid-structure interaction behavior will be. By reducing the computational cost for fluid-structure interaction analysis, structural optimization of future vertical lift vehicles can be accomplished in a much shorter time frame.

For more information, contact the U.S. Army CCDC Army Research Laboratory Public Affairs at 703-693-6477.

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This article first appeared in the October, 2020 issue of Tech Briefs Magazine.

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