Platform Studies
Wednesday 10th November 2010, 1600hrs–1730hrs
Chaired by Jerry Bradshaw Interference Striation Pattern of Underwater Target Radiated Noise in Shallow Water Waveguide: Theoretical Analysis and Experiment Results Professor Qihu Li, Institute of Acoustics, Chinese Academy of Sciences, China Ming Li; Xiaoping Huang, Institute of Acoustics, Chinese Academy of Sciences, China Waveguide invariant in shallow water has been an important topic over the past three decades. The interference phenomena of direct wave of radiated noise of underwater target and reflection wave from sea surface and sea bottom can be considered as a typical case of shallow water waveguide. The interference striation pattern of direct wave and its reflection is the effective and comprehensive figure for better understanding the essence of shallow water waveguide invariant. The theoretical analysis of interference phenomena generated by direct wave of radiated noise of underwater target and its reflection wave from sea surface and sea bottom is presented in this paper. It is shown that the interference wave resulted by sea surface reflection will produce striation pattern centered at high frequency band. But the interference of nulling frequency resulted by sea bottom reflection may be at low frequency or high frequency, it strongly depends on the acoustic behavior of sea bottom. The relationship between main parameters of interference striation pattern and target, receiver, and environment is derived. It is shown that the interference striation have the shape of hyperbolic curve. The equation set of the hyperbolic curve and its asymptotic line is presented. The at sea experiment carried out in South China sea shows some interesting results. A part of data processing results are illustrated in this paper. The results expressed in this paper show that the interference striation pattern can be used, in some conditions, as a potential means for target recognition. Maneuvering Propulsor: Application to Undersea Vehicles Dr. Stephen Huyer, Naval Undersea Warfare Center (Division Newport), United States Computational and experimental studies have demonstrated a method to generate vehicle maneuvering forces from a propulsor alone. This concept has significant relevance toward increased maneuverability for both unmanned undersea vehicles and torpedoes. Both ducted and open, pre-swirl propulsors were configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and pre-swirl the flow into the propulsor when generating a roll moment to counter the torque produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to both generate a mean stator side force and subsequently vary the inflow axial velocity and swirl that is ingested into the rotor. The rotor then generates side force in response to the inflow. Computational concept studies and recent experiments for a simplified propulsor unit demonstrated side force coefficients on the order of 0.1 for the ducted configuration and 0.3 for an open propulsor. In the case of the latter, this translates to 50% larger forces than can be generated by conventional control surfaces on 21” Unmanned Undersea Vehicles. This paper will present a summary of results from the computations and validation experiments demonstrating the effectiveness of this method. Next, an open and ducted propulsor utilizing this technology was designed specifically for the NUWC Light vehicle. Fully viscous 3-D (Reynolds Averaged Navier-Stokes, RANS) computations were used to predict the stator forces, velocity field and rotor response. The RANS inflow was then computed and used as velocity boundary conditions during rotor blade design using potential flow methods. Blade parameters including blade number, rake, skew and a combination of the two were varied to characterize their effects and optimized to minimize unsteady forces and maximize side forces. RANS was used to then validate the final propulsor design. Final results of this design will be presented. Modular Hoistable Masts for Conventional Submarines Mr. Bernhard Krueger, Gabler Maschinenbau GmbH, Germany The sensor equipment being installed on hoistable masts, plays a key role in the capabilities of submarines. In order to be more flexible and modular with respect to the equipment, GABLER offers new types of hoistable masts with the possibility of interchanging the payload (sensors) much easier. Two Gabler hoistable masts solution will be highlighted:
The first is the so-called standard mast, which generally is a rectangular shaft guided hoistable mast. A number of different shaft sizes takes account of housing various sensors of different sizes, but in one same shaft size it is possible to incorporate diverse sensors of comparable sizes. This makes it easy and cost effective to install different sensor types e.g. in sister ships to increase the overall capability range of a flotilla, or to change the sensors over the live span of a boat;
The second solution is GABLERs Modular Multi-Purpose Mast TRIPLE M. This system features a containerised solution for integrating new, unconventional sensors and effectors in a hoistable mast. This system not only extends the range of possible sensors far beyond the existing equipment of submarines, but also allows for mission oriented modularity, as the modules can be interchanged rapidly due to standardized interfaces.
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