Computational Studies for the Development of a Hybrid UAV/UUV

Abstract

The development of a hybrid unmanned aerial and underwater vehicle (UAV/UUV) for transit to a shallow water zone is described. The computational fluid dynamics study is focused on the aerodynamic characteristics of the vehicle during the glide phase, the thrust production for underwater propulsion, and predicting the forces on the vehicle during the landing phase of the operation. The effect of size, position, and camber of the front fins acting as canards on the pitch stability of the vehicle is investigated. The hydrodynamic thrust of the flapping fins for underwater propulsion shows that a vehicle speed of 1kt can be achieved. The trajectory and the computed forces and moments using coupled 6-dof simulations during the landing phase of the vehicle provide confidence that the fin and the vehicle will survive a water landing.

Design and demonstration of a seabird-inspired fixed-wing hybrid UAV-UUV system

“…Wing structural sizing was performed by assuming a worst-case scenario whereby the vehicle plunges into the water nose first. A detailed analysis such as the numerical simulations by the Naval Research Laboratory [13] would be needed to accurately design the airframe structure to efficiently handle the landing loads. However, the object of this work was to demonstrate the viability of this vehicle operational approach.…”

“…The plunge dive analysis was done at 7.72 m s −1 , which was the half the estimated stall speed of the aircraft. Applying equation (13) to the wing gave a maximum estimated impact load of 2.2 kN per unit span, or about 3.2 kN total. These loads roughly correspond to the results from the numerical solver used by the Naval Research Lab [13].…”

“…Applying equation (13) to the wing gave a maximum estimated impact load of 2.2 kN per unit span, or about 3.2 kN total. These loads roughly correspond to the results from the numerical solver used by the Naval Research Lab [13]. To alleviate landing loads of a nosefirst landing, a strip of Kevlar was used to along the leading edge to absorb impact energy of the landing.…”

“…It is also a single-use vehicle [12]. Similarly, the third is a flapping fin vehicle that can also be dropped from an aircraft [13]. None of these designs are capable of returning to their original domain and continuing operations.…”

Swimming performance of a hybrid unmanned air-underwater vehicle

“…Flimmer fin geometry compared with previous actively controlledcurvature fins developed at the Naval Research Laboratory. (a) Flimmer prototype showing the fixed wing and four fins (two wing mounted, and two fore body mounted), and (b) swimming-only Flimmer-S prototype showing 4-fin tandem configuration.fins with the vehicle drag using the computational solver predicts that the Flimmer-S can achieve a terminal speed of 0.66 m/s (1.3 knots) when the fins are flapping at 0.8 Hz(Figure 4)[18].Measurement of Flimmer-S speed in experiments demonstrates a steady-state forward speed of 0.60-0.70 m/s (1.2-1.4 knots) as shown inFigure 5. This value is in the range of what computations predict, within 8%.…”