AeroArts' projects include a wide range of topics ranging from experimental aerodynamics to aircraft design, aircraft safety and control and handling qualities.

Experimental Aerodynamics

Problem: Aerodynamic mathematical models require not only static forces and moments, but also damping forces, time-varying and nonlinear effects to reproduce dynamic motions of the aircraft. Several recent aircraft developments have been adversely affected by lack of reliable dynamic data.

Standard Solution: Computational methods are not yet mature enough to deal with dynamic, nonlinear and unsteady flows. The usual experimental approach,testing in a wind tunnel using a dynamic rig, utilizes motions that are more geared to the available motion than to the needed dynamics. For example,

• Forced oscillation wind tunnel rigs exercise a model in small perturbation oscillations
• Rotary balance wind tunnel rigs exercise a model in coning motion.

These harmonic, sinusoidal motions are severe limitations when we compare them to the actual motions of aircraft experiencing nonlinear flow phenomena.

Also, the physics of dynamic testing in wind tunnels creates some fundamental limitations . In particular,

• Scaled motions in a wind tunnel are typically ten times faster than real time, challenging the capabilities of the drive mechanisms and data acquisition systems. Flow visualization becomes a post-experiment activity using high-speed camera output in slow motion.
• For any size model, even a full-scale Micro Air Vehicle (MAV), inertia forces measured on the balance are typically hundreds of times bigger in a wind tunnel than aerodynamic forces. This leads to difficult tare determination and inherently poor 'aerodynamic-to-inertia force' ratios, i.e. poor signal-to-noise.
• The natural frequencies of the support system typically fall within the aerodynamic frequency range. This further exacerbates extraction of the data from the experimental artifacts, especially if rapid dynamic motions are of interest.

AeroArts' Approach: AeroArts' approach is to test, not in air, but in water. The main advantages of this approach for low Reynolds number testing are:

• Inertia forces are negligible compared with fluid dynamic forces. Tares are identical to, and as simple as for, a static test. The 'signal-to-noise' ratio is excellent.
• The natural aerodynamic frequencies are well separated from the support frequencies, further enhancing signal-to-noise.
• Operation is in slow motion, around one tenth of real time. Motor requirements, dynamic force and moment measurement, as well as the flow visualization, all benefit tremendously from this.
• All the other positive reasons for testing in water are preserved; low cost models, (often modified from models off the hobby shop shelf), superb flow visualization, inherent safety, and so on.