Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Computational Design Optimization Using RANS
Computational Design Optimization Using RANS
Pages 991-1001
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These optimizations include the redesign of a modern marine propeller for improved cavitation performance, redesign of a bow bulb on a surface combatant to reduce downstream vortices, and the redesign of a rudder in the wake of a propeller to reduce outboard surface cavitation. INTRODUCTION Through relentless experimental and computational field simulation (CFS)
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utilize a continuous-adjoint approach for target pressure matching of propulsor configurations using the psuedocompressible Euler equations in a rotating frame. In this work, the current computational design methodology is demonstrated on three, nontrivial hydrodynamic components.
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The discrete-adjoint variable formulation begins by combining Eq.4 from the direct differentiation method with the sensitivity derivatives in Eq.1. From this adjoins vectors may be conveniently defined such that the sensitivity of the field variables are no longer needed.
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(1998) for -performing disciplinary and multidisciplinary sensitivity analysis, Rich uses complex variables to approximate derivatives of real functions.
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RESULTS Three examples analysis exploratory hydrodynamic optimization were performed to access the sensitivity and computational design capabilities developed in UNCLE. Each is representative of typical components that have been recently redesigned for the DDG51 fleet.
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Sensitivity derivatives where obtained via the direct approach with the CTSE method used to construct all linearizations. Since this was an exploratory study, only design improvement over the original P5168 propeller was sought.
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Due to the fact that the ~rameterization of the sonar dome resulted in 24 shape design variables, and that the analysis and sensitivity analysis were performed sequentially on a single block, only two design cycles were performed. As seen via the width contours for the original and modified bow shown in Fig.
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Subsequently, drydock inspections confirmed cavitation erosion on the outboard rudder surface, while none was present on the inboard surface (Jiang 19951. Shen then conducted a computational and experimental design of the rudder twist distribution and found that by aligning the local rudder twist to the incoming propeller induced flow angles, cavitation on the outboard surface could be significantly reduced.
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Figure 13: Pressure distributions on untwisted and twisted rudders. For this design, the analyses required in the design cycles and the computation of the sensitivity derivatives where performed in parallel over 16 blocks and 4 design variables.
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1997. Newman III, J.C., Taylor III, A.C., and Burgreen, G.W., "An Unstructured Grid Approach to Sensitivity Analysis and Shape Optimization Using the Euler
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Newman III, J.C., Anderson, W.K., and Whitfield, D.L., "Multidisciplinary Sensitivity Derivatives Using Complex Variables," Mississippi State University Report MSSU-COE-ERC-98-08, 1998. Newman III, J.C., Taylor III, A.C., Barnwell, R.W., Newman, P.A., and Hou, G.J-.W., "Overview of Sensitivity Analysis and Shape Optimization for Complex Aerodynamic Configurations," J
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