Adjoint Method for Shape Optimization in Real-Gas Flow Applications

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
M. Pini ◽  
G. Persico ◽  
D. Pasquale ◽  
S. Rebay
Keyword(s):  
Shape Optimization ◽  
Gas Flow ◽  
Adjoint Method ◽  
Descent Method ◽  
Steepest Descent Method ◽  
Outlet Section ◽  
Optimization Approach ◽  
Optimization Strategy ◽  
Real Gas ◽  
Turbine Cascades

An adjoint-based shape optimization approach for supersonic turbine cascades is proposed for application to organic Rankine cycle (ORC) turbines. The algorithm is based on an inviscid discrete adjoint method and encompasses a fast look-up table (LuT) approach to accurately deal with real-gas flows. The turbine geometry is defined by adopting state-of-the-art parameterization techniques (NURBS), enabling to handle both global and local control of the shape of interest. A preconditioned steepest descent method has been chosen as gradient-based optimization algorithm to efficiently search for the nearest minimum. The potential of the optimization approach is first verified by application on the redesign of an existing converging–diverging turbine nozzle operating in thermodynamic regions characterized by relevant real-gas effects. A significant efficiency improvement and a more uniform flow at the blade outlet section are achieved, with expected beneficial effects on the aerodynamics of the downstream rotor. The optimized configuration is also assessed by means of high-fidelity turbulent simulations, which point out the capability of the present inviscid approach in optimizing supersonic turbine cascades with very limited computational burdens. Finally, the newly developed real-gas adjoint method is compared against adjoints based on ideal equations of state on the same design problem. Results show that the performance gain obtained by a fully real-gas optimization strategy is by far higher than that achieved with simplified approaches in case of ORC turbines. This proves the relevance of including accurate thermodynamic models in all steps of ORC turbine design.

scholarly journals Optimization of Open Boundary Conditions in a 3D Internal Tidal Model with the Adjoint Method around Hawaii

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Anzhou Cao ◽  
Haibo Chen ◽  
Jicai Zhang ◽  
Xianqing Lv
Keyword(s):  
Boundary Conditions ◽  
Adjoint Method ◽  
Internal Tide ◽  
Descent Method ◽  
Steepest Descent Method ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Tidal Model ◽  
Open Boundaries ◽  
Surface Manifestation

Based on the theory of inverse problem, the optimization of open boundary conditions (OBCs) in a 3D internal tidal model is investigated with the adjoint method. Fourier coefficients ofM2internal tide on four open boundaries, which are regarded as OBCs, are inverted simultaneously. During the optimization, the steepest descent method is used to minimize cost function. The reasonability and feasibility of the model are tested by twin experiments (TEs). In TE1, OBCs on four open boundaries are successfully inverted by using independent point (IP) strategy, suggesting that IP strategy is useful in parameter estimation. Results of TE2 indicate that the model is effective even by assimilating inaccurate “observations.” Based on conclusions of TEs, theM2internal tide around Hawaii is simulated by assimilating T/P data in practical experiment. The simulated cochart shows good agreement with that obtained from the Oregon State University tidal model and T/P observations. Careful inspection shows that the major difference between simulated results and OSU model results is short-scale fluctuations superposed on coamplitude lines, which can be treated as the surface manifestation modulated by the internal tide. The computed surface manifestation along T/P tracks is comparable to the estimation in previous work.

Robust Adjoint-Based Shape Optimization of Supersonic Turbomachinery Cascades

2014 ◽  
Author(s):  
M. Pini ◽  
G. Persico ◽  
V. Dossena
Keyword(s):  
Shape Optimization ◽  
Optimization Technique ◽  
Operating Conditions ◽  
Point Problem ◽  
Outlet Section ◽  
Optimization Approach ◽  
Turbine Cascade ◽  
Optimal Point ◽  
Novel Approach ◽  
Wide Range

An adjoint-based shape optimization approach for supersonic turbine cascade is proposed. The algorithm is based on a discrete adjoint method, state-of-the-art parametrization techniques (NURBS) and a preconditioned steepest descent optimizer to search the optimal point. The potential of the optimization approach is verified on two different design problems. Initially the design methodology is applied to the re-design of an existing supersonic turbine cascade operating at nominal conditions, with the aim of obtaining a more uniform flow at blade outlet section. Then, an original extension of the algorithm for treating off-design conditions is envisaged. The method combines a standard multi-point optimization technique with an uncertainty quantification algorithm to assess the design points and the weights of the multi-point problem. The capability of the novel approach in providing robust designs is finally investigated by maximizing the performances of the same baseline configuration working under a relatively wide range of operating conditions. In both tests remarkable outcomes are achieved in terms of improvement of blade performances and computational efficiency.

scholarly journals A Discrete Adjoint Method for Two-Phase Condensing Flows Applied to the Shape Optimization of Turbine Cascades

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
M. Pini ◽  
L. Azzini ◽  
S. Vitale ◽  
P. Colonna
Keyword(s):  
Shape Optimization ◽  
Adjoint Method ◽  
Volume Fraction ◽  
Liquid Volume ◽  
Two Phase ◽  
Discrete Adjoint ◽  
First Case ◽  
Discrete Adjoint Method ◽  
Condensing Flows ◽  
Turbine Cascades

Abstract This paper presents a fully turbulent two-phase discrete adjoint method for metastable condensing flows targeted to turbomachinery applications. The method is based on a duality preserving algorithm and implemented in the open-source CFD tool SU2. The optimization framework is applied to the shape optimization of two canonical steam turbine cascades, commonly referred to as White cascade and Dykas cascade. The optimization were carried out by minimizing either the liquid volume fraction downstream of the cascade or the total entropy generation due viscous effects and heat transfer. In the first case, the amount of condensate turned out to be reduced by as much as 24%, but without reduction of the generated entropy, while the opposite resulted in the second case. The outcomes demonstrate the capability and computational efficiency of adjoint-based automated design for the shape optimization of turbomachinery operating with phase change flow.

Real gas flow fields about three dimensional configurations

1983 ◽  
Author(s):  
A. BALAKRISHNAN ◽  
C. LOMBARD ◽  
W.C. DAVY
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Flow Fields ◽  
Real Gas

Solution of inverse coefficient problem for fractional anomalous diffusion equation

2012 ◽  
Vol 9 (2) ◽  
pp. 65-70
Author(s):  
E.V. Karachurina ◽  
S.Yu. Lukashchuk
Keyword(s):  
Anomalous Diffusion ◽  
Fractional Derivatives ◽  
Descent Method ◽  
Extremum Problem ◽  
Steepest Descent Method ◽  
Coefficient Problem ◽  
Caputo Fractional Derivatives ◽  
Inverse Coefficient Problem ◽  
Residual Functional ◽  
Inverse Coefficient

An inverse coefficient problem is considered for time-fractional anomalous diffusion equations with the Riemann-Liouville and Caputo fractional derivatives. A numerical algorithm is proposed for identification of anomalous diffusivity which is considered as a function of concentration. The algorithm is based on transformation of inverse coefficient problem to extremum problem for the residual functional. The steepest descent method is used for numerical solving of this extremum problem. Necessary expressions for calculating gradient of residual functional are presented. The efficiency of the proposed algorithm is illustrated by several test examples.

A Joint Multicast Optimization Approach for QoS Provisioning in Optical Label Switching (OLS) Networks

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Yassine Khlifi ◽  
Majid Alotaibi
Keyword(s):  
Traffic Management ◽  
Network Performance ◽  
Data Transfer ◽  
Optimization Approach ◽  
Optimization Strategy ◽  
Wavelength Converter ◽  
Label Switching ◽  
Link Capacity ◽  
Two Stages ◽  
Logical Topology

AbstractOptical label switching is introduced for ensuring fast data transfer, quality of service (QoS) support, and better resource management. However, the important issue is how to optimize resource usage and satisfy traffic constraints for improving network performance and design. This paper proposes a dynamic approach that optimizes the resource in terms of link capacity and FDL (fiber delay line) buffering as well as a wavelength converter. The proposed approach decreases the resources usage and guarantees QoS support for various traffic demands. The optimization strategy consists of two stages: path building and traffic management. The path building assures logical topology making using the cumulative cost of available resource and traffic requirements including unicast and multicast. The traffic management solves the resource formulation problem during the traffic transfer by guaranteeing the required loss and blocking delay. Simulation work is conducted for validating the proposed approach and evaluating its performances and effectiveness. Simulation results show that our proposal minimizes effectively the use of link capacity of lightpath and light-tree. Moreover, our approach optimizes the use of buffering capacity and wavelength converter and guarantees QoS support according to traffic requirements.

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