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Parallel computing in water network analysis and leakage minimization

JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT-ASCE 2000年第4期126卷 251-260页

作者： Alonso, JM Alvarruiz, F Guerrero, D Hernández, V Ruiz, PA Vidal, AM Martínez, F Vercher, J Ulanicki, B Univ Politecn Valencia Dept Sistemas Informat & Computac Parallel Comp Grp Valencia 46022 Spain Univ Politecn Valencia Dept Ingn Hidraul & Med Ambiente Valencia 46022 Spain De Montfort Univ Leicester LE1 9BH Leics England

In this paper a parallel computing based software demonstrator for the simulation and leakage minimization of water networks is presented. This demonstrator, based on the EPANET package, tackles three different types of problems making use of parallel computing. First, the solution of the hydraulic problem is treated by means of the gradient method. The key point in the parallelization of the method is the solution of the underlying linear systems, which is carried out by means of a multifrontal Choleski method. Second, the water quality simulation problem is approached by using the discrete volume element method. The application of parallel computing is based on dividing the water network in several parts using the multilevel recursive bisection graph partitioning algorithm. Finally, the problem of leakage minimization using pressure reducing valves is approached. This results in the formulation of an optimization problem for each time step, which is solved by means of sequential quadratic programming. Because these subproblems are independent of each other, they can be solved in parallel.

关键词： sequential quadratic programming pressure reducing valves PARALLEL PROCESSING (COMPUTERS) parallelization Network analysis

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Ply angle optimization of nonuniform composite beams subject to aeroelastic constraints

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AIAA JOURNAL 2000年第10期38卷 1992-1994页

作者： Evrard, T Butler, R Hughes, SW Banerjee, JR Univ Bath Dept Mech Engn Bath BA2 7AY Avon England Univ Bath Dept Mech Engn Bath BA2 7AY Avon England City Univ London Dept Aeronaut & Mech Engn London EC1V 0HB England

Studies the effect of both ply angle variation and the position of lumped massed on flutter speed for uniform thickness wind-tunnel models. Parametric study for uniform thickness beam; Optimization of nonuniform thick... 详细信息

关键词： Shear Layers Unswept Wings sequential quadratic programming Shear Deformation Young's Modulus Critical Loading Aspect Ratio Swept Wing Airspeed Aerodynamic Force

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Optimization-based inverse simulation of a helicopter slalom maneuver

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2000年第2期23卷 289-297页

作者： Celi, R Univ Maryland Alfred Gessow Rotorcraft Ctr Dept Aerosp Engn College Pk MD 20742 USA

An inverse simulation methodology based on numerical optimization is presented. The methodology is applied to a simplified version of the slalom maneuver in the ADS-33D helicopter handling qualities specification. The inverse simulation is formulated as an optimization problem with trajectory. and dynamic constraints, pilot inputs as design variables, and an objective function that depends on the specific problem being solved. A maximum speed solution is described. The results show that numerical optimization is a reliable and flexible tool for inverse simulation, both when the required trajectory is prescribed explicitly and when it is defined indirectly through geometric and dynamic constraints. When the trajectory is defined indirectly, there is not a single acceptable trajectory but rather an entire family with noticeable differences in the helicopter dynamics and in the required pilot inputs. Even when the trajectory is prescribed explicitly, multiple solutions exist. For handling qualities studies, the multiple solutions may provide an indication of tbe amount of scatter in pilot ratings to be expected for a given aircraft and a given maneuver. However, if the inverse simulation is used for simulation validation, then additional constraints may have to be placed on the solution to make it unique.

关键词： Helicopters Pilot Handling Qualities sequential Linear programming sequential quadratic programming Numerical Optimization Trajectory Optimization Empennage Helicopter Dynamics Aircraft Dynamics

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Bilevel integrated system synthesis with response surfaces

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AIAA JOURNAL 2000年第8期38卷 1479-1485页

作者： Kodiyalam, S Sobieszczanski-Sobieski, J Lockheed Martin Space Syst Co Ctr Adv Technol Sunnyvale CA 94089 USA NASA Langley Res Ctr Hampton VA 23681 USA

Two variants of the BLISS method are proposed for multidisciplinary design optimization (MDO). These variants utilize experimental design methods and response surfaces to reduce the number of expensive system analysis required for solution of the MDO problem. BLISS is an MDO method for decomposition-based optimization of engineering systems that involves system optimization with a relatively small number of design variables and a number of subsystem optimizations that could each have a large number of local variables. In BLISS, the optimum sensitivity analysis data are used to relate the subsystem optimization solutions with the system optimizations. Instead, with the proposed variants, polynomial response surface approximations using either the system analysis or the subsystem optimization results are used. Additionally, the response surface construction process is well suited for computing in a concurrent processing environment. The proposed variants are implemented and evaluated on a conceptual-level aircraft and ship design problem.

关键词： Sensitivity Analysis MDO Concurrent Processing Computing Black Box Aspect Ratio Surface Modeling Aerodynamics Analysis of Variance sequential quadratic programming

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Automated design of a three-dimensional subsonic diffuser

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JOURNAL OF PROPULSION AND POWER 2000年第6期16卷 1132-1140页

作者： Zhang, WL Knight, DD Smith, D Rutgers State Univ Dept Mech & Aerosp Engn New Brunswick NJ 08903 USA Rutgers State Univ Dept Comp Sci New Brunswick NJ 08903 USA

A novel methodology is developed to integrate state-of-the-art computational fluid dynamics analysis, NURBS, and optimization theory to reduce total pressure distortion and sustain total pressure recovery within a curved three-dimensional subsonic S-duct diffuser by automated redesign of the diffuser shape. Two independent design variables are used. The change of the surface shape is assumed to be Gaussian. GASP with the modified Baldwin-Lomax turbulence model (Baldwin, B. S., and Lomax, ii., "Thin Layer Approximation and Algebraic Model for Separated Turbulent Flows," AIAA Paper 78-257, 1978) is employed for the flowfield prediction and proved to give good agreement with the experimental surface pressure for the baseline S-duct diffuser geometry. The automated design optimization is performed with a gradient-based method to minimize the total pressure distortion based on the two design variables. The best configuration obtained reduced distortion by typically 70% while keeping the total recovery essentially the same. The results indicate that the mechanism responsible for improved diffuser performance is the suppression of detrimental secondary Rows by changing the surface shape to redirect the flow.

关键词： Subsonic Diffusers Baldwin Lomax Turbulence Model Internal Flows Vortex Generators Static Pressure Boundary Layer Separation Vortices sequential quadratic programming Lagrange Multipliers Surface Streamlines

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Visual aircraft identification as a pursuit-evasion game

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2000年第4期23卷 701-708页

作者： Raivio, T Ehtamo, H Aalto Univ Syst Anal Lab FIN-02015 Espoo Finland

A new computational decomposition scheme is applied to a pursuit-evasion game that describes the visual identification of a foreign intruder aircraft in three dimensions. The intruder is assumed to minimize its distance to the state border at the time of identification, whereas the identifying aircraft wishes to intercept the intruder as far away inland as possible. The identification occurs when the identifier reaches the intruder's velocity and attitude within a given distance from it. The computational scheme decomposes the minimaximization of the payoff into two sequences of optimal control problems that can be solved using discretization and nonlinear programming techniques.

关键词： Aircrafts Nonlinear programming Optimal Control Aerodynamic Properties Air Brakes Dynamic Pressure Heading Angle sequential quadratic programming Constellations Open Loop

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Optimal estimation of roughness in open-channel flows

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JOURNAL OF HYDRAULIC ENGINEERING-ASCE 2000年第4期126卷 299-303页

作者： Ramesh, R Datta, B Bhallamudi, SM Narayana, A Indian Inst Technol Dept Civil Engn Kanpur 208016 Uttar Pradesh India

The inverse problem of estimating the open-channel flow roughness is solved using an embedded optimization model. Measurement data for flow depths and discharges at several locations and times are used as inputs to the optimization model. The nonlinear optimization model embeds the finite-difference approximations of the governing equations for unsteady flow in an open channel as equality constraints. The sequential quadratic programming Algorithm is used to solve the optimization model. The performance of the proposed parameter estimation model is evaluated for different scenarios of data availability and noise in flow measurement data. Solution results for illustrative problems indicate the potential applicability of the proposed model.

关键词： unsteady flow Open channel flow sequential quadratic programming roughness Open channels Noise indium model measurement Inverse method finite-difference approximation

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Uniform convergence and mesh independence of Newton's method for discretized variational problems

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SIAM JOURNAL ON CONTROL AND OPTIMIZATION 2000年第3期39卷 961-980页

作者： Dontchev, AL Hager, WW Veliov, VM Amer Math Soc Ann Arbor MI 48107 USA Univ Florida Dept Math Gainesville FL 32611 USA Vienna Tech Univ A-1040 Vienna Austria Bulgarian Acad Sci Inst Math & Informat BU-1113 Sofia Bulgaria

In an abstract framework, we study local convergence properties of Newton's method for a sequence of generalized equations which models a discretized variational inequality. We identify conditions under which the method is locally quadratically convergent, uniformly in the discretization. Moreover, we show that the distance between the Newton sequence for the continuous problem and the Newton sequence for the discretized problem is bounded by the norm of a residual. As an application, we present mesh-independence results for an optimal control problem with control constraints.

关键词： Newton's method variational inequality optimal control sequential quadratic programming discrete approximation mesh independence

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Response surface approximations: Noise, error repair, and modeling errors

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AIAA JOURNAL 2000年第12期38卷 2336-2343页

作者： Papila, M Haftka, RT Univ Florida Dept Aerosp Engn Mech & Engn Sci Gainesville FL 32611 USA

In the past few Sears there has been interest in using response surface techniques to create surrogates to computer simulations. Response surface techniques allow detection and correction of errors as well as filtering out numerical noise, but these techniques introduce additional modeling errors. Methods of reducing both noise and modeling errors are explored. It is also demonstrated that repairing designs with large errors is preferable to eliminating these designs from consideration. Response surface approximations for a high-speed civil transport wing weight equation created from the results of a large number of structural optimizations are used for demonstration. It is shown that the statistical tools available for response surface techniques are effective for error detection and for filtering out noise. Once the noise is reduced, modeling errors can also be reduced by increasing the order of the approximation.

关键词： High Speed Civil Transport Structural Optimization Structural Response Fuselages Aerodynamic Simulation sequential quadratic programming sequential Linear programming Shape Functions Sweep Angle Central Composite Designs

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Degenerate nonlinear programming with a quadratic growth condition

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SIAM JOURNAL ON OPTIMIZATION 2000年第4期10卷 1116-1135页

作者： Anitescu, M Univ Pittsburgh Dept Math Pittsburgh PA 15213 USA

We show that the quadratic growth condition and the Mangasarian-Fromovitz constraint qualification (MFCQ) imply that local minima of nonlinear programs are isolated stationary points. As a result, when started sufficiently close to such points, an L-infinity exact penalty sequential quadratic programming algorithm will induce at least R-linear convergence of the iterates to such a local minimum. We construct an example of a degenerate nonlinear program with a unique local minimum satisfying the quadratic growth and the MFCQ but for which no positive semidefinite augmented Lagrangian exists. We present numerical results obtained using several nonlinear programming packages on this example and discuss its implications for some algorithms.

关键词： nonlinear programming quadratic growth sequential quadratic programming degeneracy

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