摘要:

The all-at-once approach is implemented to solve an optimum airfoil design problem. The airfoil design problem is formulated as a constrained optimization problem in which flow variables and design variables arc viewed as independent and the coupling steady state Euler equation is included as a constraint, along with geometry and other constraints. In this formulation, the optimizer computes a sequence of points which tend toward feasibility and optimalily at the same lime (all-at-once). This decoupling of variables typically makes the problem less non-linear and can lead to more efficient solutions. In this paper an existing optimization algorithm is combined with an existing flow code. The problem formulation, its discretization, and the underlying solvers arc described. Implementation issues arc presented and numerical results are given which indicate that the cost of solving the design problem is appropriately six times the cost of solving a single analysis problem.

ISSN:1061-8562    

DOI:10.1080/10618569808940863

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We present through this paper some new results with our approach for optimal shape design based on a CAD-free framework for shape and unstructured mesh deformations, automatic differentiation by program for the gradient computation and mesh adaption by metric control. Automatic differentiation allows for an easy, reliable and fast discrete adjoint computation. We managed to get the Jacobian of our Navier-Stokcs solver including a k-e turbulence model and wall-laws. The CAD-free framework is shown to be particularly convenient for optimization when the mesh connectivities and the shape discretization arc variable during optimization. Using these ingredients constrained optimization for turbulent transonic flows has been investigated in both 2 and 3D.

ISSN:1061-8562    

DOI:10.1080/10618569808940864

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper wishes lo describe Evolutionary Algorithms as an effective means for the solution of the Aerofoil Design Optimisation in Aerodynamics. Firstly the basic ideas underlying Evolutionary Algorithms arc outlined. Several versions of Evolutionary Algorithms arc briefly described, focussing on their similarities and on their differences as well. Then their application to both Direct and Inverse Aerofoil Design Problem is described, and results arc given. Finally, several possible parallel models for Evolutionary Algorithms are discussed, and the results of the application of one of them to the above problem arc presented.

ISSN:1061-8562    

DOI:10.1080/10618569808940865

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A successful application of a linear controller to a two-dimensional channel flow is presented. An optimal and robust reduced-order linear feedback controller is derived by using multi-variable linear-quadratic-Gaussian synthesis, or, in modern term, H2synthesis, combined with model reduction techniques. This controller based on a reduced-model of the linearized Navier-Stokes equations is applied to suppress finite-amplitude near-wall disturbances in a channel flow at Re = 1500. The controller efficiently reduced near-wall disturbances obtaining a substantial drag reduction and eventually the flow is relaminarized

ISSN:1061-8562    

DOI:10.1080/10618569808940866

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In his paper we consider the problem of designing a feedback controller for a thermal fluid. Any practical feedback controller for a fluid flow system must incorporate some type of state estimator. Moreover, regardless of the approach, one must introduce approximations at some point in the analysis. The method presented here uses distributed parameter control theory to guide the design and approximation of practical slate estimators. Wc use finite clement techniques to approximate optimal infinite dimensional controllers based on linear quadratic Gaussian lpar;LQG) and MinMax theory for the Bonssincsq equations. These designs are then compared to full state feedback. We present several numerical experiments and we describe how these techniques can also be applied to sensor placement problems.

ISSN:1061-8562    

DOI:10.1080/10618569808940867

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We consider the nonlinear aeroelasticity problem of the interaction between a viscous, incompressible fluid and Lin elastic solid undergoing large displacement. The non-linearities of the problem formulation include the solid and fluid governing equations. as well as thc dependence of the How geometry on the solid deformation. The resulting coupling is thus two-way. We develop domain-decomposition methods for solution and sensitivity analysis of the coupled problem. The domain decomposition is in the form of a block-Gauss-Seidel-like prcconditioncr that decomposes ihc coupled-domain problem into distinct nonovcrlapping fluid and solid subdotnain problems. The preconditioner thus enables exploitation or single-domain algorithms for solid and fluid mechanics discretization and solution. On the other hand, two-way fluid-solid coupling is retained within the residuals, which is essential for correct sensitivities. Sensitivities of field quantities can be found with little additional work beyond that required for solving the coupled fluid-solid system. The methodology developed here is illustrated by the solution of a problem of viscous incompressible flow about an infinite clastic cylinder. Sensitivities of the resulting velocity and displacement fields with respect to elastic modulus and fluid viscosity are computed.

ISSN:1061-8562    

DOI:10.1080/10618569808940868

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this article we investigate computational methods for the control and stabilization of systems modeled by parabolic equations of the advection-reaction-difTusion type and by the Navier-Stokes equations for incompressible viscous fluids. For the first class of control problems wc shall discuss open loop control methods and closed loop methods a la Riccati. Concerning the second class of problems we shall consider the Dirichlet boundary control of low around cylinders and attempt to reduce the viscous drag. The results of numerical experiments will validate the computational methods described in this article.

ISSN:1061-8562    

DOI:10.1080/10618569808940869

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This article is concerned with penalty methods for solving optimal Dirichlet control problems governed by the steady-state and time-dependent Navier-Stokes equations. We present, in two different versions, the penalized methods for solving the steady-slate Dirichlet control problems. These approaches are implemented and compared numerically. We also generalize the penalty methods to the time-dependent case. Scmidiscrete and fully discrete approximations of time-dependent Dirichlet control problems are discussed and implemented. Numerical results for solving both the steady-state and the time dependent Dirichlet control problems are reported.

ISSN:1061-8562    

DOI:10.1080/10618569808940870

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We use the concept of relaxed or measure-valued solutions for control problems of turbulent flow related to Navicr-Stokes equation. Sufficient conditions guaranteeing the existence of measure solutions arc presented. Results on existence of optimal controls for Blow up time and Bolza problems for such systems are also presented. New results on relaxed necessary conditions of optimality are proved. Further it is shown that the relaxed necessary conditions reduce to classical Pontryagin type necessary conditions if measure solutions degenerate into Dirac structure. The paper is concluded with an algorithm based on the new necessary conditions for computing optimal controls.

ISSN:1061-8562    

DOI:10.1080/10618569808940871

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper is concerned with numerical solutions of optimal control problems for unsteady, viscous, incompressible flows. In general, controls can be of the distributed type (external body force) or Dirichlet type 7lpar;e.g., boundary velocity). Here, wc only consider the former case, although most of what we present is also applicable to the latter. Two different optimization objectives and associated solution methodologies are described. One involves a global-in-time functional, the other a local-in-time functional. Which method is preferred depends on the specific application. Some test computational results are presented.

ISSN:1061-8562    

DOI:10.1080/10618569808940872

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor