Nova Ray® Science – Patented Arcuate Wings
Pronounced: ärkyo͞oət, ärkyo͞oˌāt
an adjective technical
Shaped like a bow; curved:
“the arcuate sweep of a bird’s wings“
Why Arcuate Wings Are Important To The Nova Ray Design:
The Nova Ray “arcuate wing” design solves long-time industry struggles with cable drag in strong currents. The patented wing design eliminates the phenomenon known as “Dutch Roll Instability,” (1) a problem experienced by flat wing designs. Anyone who has flown an old-fashioned kite and watched it roll side-to-side has experienced this phenomenon. The Nova Ray inventors eliminated “Dutch Roll” (1) by incorporating the “arcuate” form wing, along with adding a rudder for extra stability. The result is true axis flight and stability in any currents. In fact, the faster the relative speed the more stable the Nova Ray becomes because of its arcuate wings.
The arcuate-shaped wings of the Nova Ray also counteract the lifting force of the umbilical (also described at the tether or cable). Therefore, the speed of the boat (or other vessel) or current has little effect on the operational stability of the Nova Ray. The wings increase cable use efficiency and reduce the amount of cable necessary to operate or tow at depth (see our infographics on this here).
The physical dynamics of the arcuate (bow-shaped) wing creates a stable instrumentation platform and allows for maneuverability. This increases system effectiveness in high currents and cross currents when towed or using thruster power.
The Nova Ray’s unique hydrodynamic features effectively use water flow rather than resistance to maintain operational control under changing operating modes. The patented arcuate wing is stable under tow or with the vehicle’s own thruster power.
Under thruster power, the wings operate just as a high-winged airplane would in free flight. Under tow, the arcuate wing, combined with the seamless shift in the center of rotation from the cable pull, produces a stable configuration.
The challenge with towing any device is maintaining reasonable control. Traditionally, underwater towable vehicles (UTV) and the “box like ROVs” use frames layered with flotation foam. Thrusters are then added to an already non-hydrodynamic design in order to combat currents and other hydrodynamic forces.
Nova Ray’s arcuate wing configuration is remarkably stable in turbulent currents and provides true axis flight. There is little tendency for the vehicle to rock in shifting currents. The wings, combined with other secondary control surfaces, tend to counter any destabilizing forces. The close proximity of the thrusters to the control surfaces allows for very tight maneuvering. The overall result is an ROV system that can do more and perform where other underwater systems cannot.
See the Nova Ray Engineering page for more information about the Nova Ray’s design characteristics.
Nova Ray ROV Wings/Hydrofoil Design
Instability Definitions That Affect Other ROVs:
Lateral-directional modes involve rolling and yawing motions that can result in instability affecting the quality of data collected. Motions in one of these axis almost always couples into the other so the modes are generally referred to as the “Lateral-Directional Modes”. There are three types of possible lateral-directional dynamic motion: roll subsidence mode, spiral mode, and Dutch roll mode. Nova Ray’s inventors found the perfect design to dampen or eliminate these destabilizing effects.
- Dutch roll is a type of aircraft/vehicle motion, consisting of an out-of-phase combination of “tail-wagging” and rocking from side to side. Dutch roll stability can be increased by the installation of a yaw damper. The Nova Ray is designed to compensate for this automatically.
- Spiraling – is inherent when trimmed for straight-and-level flight, without compensation will eventually develop a tightening spiral-dive. A spiral dive is not a spin; it starts with a random, increasing roll and speed. With certain designs this can lead to structural failure of the vehicles airframe as a result of excess aerodynamic/hydrodynamic loading. When the nose drops the spiral dive has begun and while in underwater vehicles this would not be catastrophic as with an aircraft, it does lead to instability. Nova Ray is designed to dampen Spiraling.
- Roll subsidence mode – is simply the damping of rolling motion. There is no direct aerodynamic moment created tending to directly restore wings-level, i.e. there is no returning “spring force/moment” proportional to roll angle. However, there is a damping moment (proportional to roll rate) created by the slewing-about of the wings. This prevents large roll rates from building up when roll-control inputs are made or it damps the roll rate (not the angle) to zero when there are no roll-control inputs. Roll mode can be improved by dihedral effects coming from design characteristics, such as high wings such as are on the Nova Ray.