Unmanned Aerial Vehicles (UAVs)
UAVs are used extensively by military forces, and increasingly by civilian agencies, to help establish Intelligence, Surveillance and Reconnaissance (ISR) superiority, and perform hazardous cargo and utility missions. CFDRC develops multi-physics software applications and delivers expert engineering design and analytical services for UAVs and micro-UAVs.
Active Flow Control of Flexible Wings
CFDRC has developed capabilities for the analysis of active smart materials control systems and synthetic jet arrays used for active structure control of vibrations of aerospace vehicles, including micro-UAVs (MAVs). Active strengthening of the structure is achieved by attaching smart material patches into the structure, or incorporating synthetic jets on wing surfaces. The use of smart materials, such as PZT, gives an actuation system that is independent from the flight control system, with the ability of structural actuation over larger frequency band. Synthetic jet actuation enables vertical take-off and landing (VTOL) capabilities for MAVs.
CFDRC is developing multi-disciplinary simulation tools for computational study and optimal design of MAVs using active control algorithms to flex, or otherwise morph the shape of a wing surface. Our experience includes:
- Performed analysis of structural vibration modes in a flexible wing configuration
- Developed innovative coupled finite element, grid motion and deformation models to handle large deformations encountered in MAV applications
- Developed and validated a flexible flapping wing model of insect
- Developed reduced models of synthetic jets that allowed use of 20 jets to simulate MAV wing flight control
Biomimetic Micro-UAV Conceptual Design
Micro air vehicles (MAVs), which are no larger than 15 cm in any dimension, can be used to perform many important missions at an affordable cost. Wing design is critical to increasing the payload and reducing power expenditure. The wing aerodynamic performance must be optimized and weight of wing and transmission minimized. CFDRC has developed computational models to understand the fundamental physics of flexible wing structure, reducing MAV design cycle time and test expenses. Examples of our designs include:
- 2-way coupling between aerodynamics and structural dynamics to optimize Biomimetic wing designs
- Computational modeling of insect flight with analysis of flapping wings aeroelasticity
- Very low Reynolds number and viscous flow field simulation characteristic of MAV flight
- Vortex dominated unsteady flow modeling with coupled fluid-structure interaction, and multiple degree-of-freedom wing kinematics
- Multi-scale modeling for MEMS based processing and fabrication of flexible wing surfaces
Urban & Complex Terrain Wind Field Effects
To successfully use light weight UAVs in the complex and spatially varying wind fields in urban areas, studies must be undertaken to understand how best to operate the UAVs, and to determine if there are any significant operational restrictions prior to initiation of more expensive operational test and evaluation. CFDRC has developed a Multi-disciplinary Urban Simulation Environment (MUSE) that integrates air vehicle flight dynamics models with high-resolution wind and turbulence fields produced using CFD for studying the impact microscale weather and flow fields have on UAVs in an urban environment. CFDRC's simulation experience includes:
- Developed an Application Programming Interface (API) that a legacy flight vehicle application may call to query local wind and turbulence fields from a CFD database
- Applied a uniformly refined Cartesian grid system to store the pre-computed CFD velocity and turbulence fields and provide a fast spatial searching strategy
- Automated development of 3D cityscape models utilizing LIDAR-generated building- and terrain-elevation data, satellite imagery, and city plan view and building maps
- Successfully demonstrated the integration of 3D urban and terrain models with a UAV flight dynamics model to simulate realistic urban mission scenario
