scholarly journals The Influence of Parameterisation Setup on the Constrained Adjoint Optimisation of Transonic Fan Blades

2020 ◽  
Author(s):  
Alistair John ◽  
Ning Qin ◽  
Shahrokh Shahpar
Keyword(s):  
Computational Cost ◽  
Free Form ◽  
Design Parameters ◽  
Control Parameters ◽  
Compressor Blades ◽  
Mechanical Integrity ◽  
Free Form Deformation ◽  
Transonic Fan

Abstract The power of adjoint optimisation is that the computational cost of the optimisation is almost independent of the number of design parameters. Thus, hundreds or even thousands of parameters can be used with relatively little increase in cost. But how much benefit does this provide, and is it always beneficial to increase the number of parameters? This work investigates the benefit achieved during the optimisation of transonic fan and compressor blades using various resolutions and layouts of Free Form Deformation grid. A method to constrain thickness throughout the blade span (to maintain mechanical integrity) during the optimisation is implemented and the effect of constraining thickness on the resulting blade designs demonstrated. It is shown that increasing the number of parameters generally leads to improved optimised designs, but that increasing the number of free-form parameters in the axial and circumferential directions is more beneficial than increasing the number of radial control parameters.

scholarly journals Computational Design Optimization for S-Ducts

Designs ◽  
2018 ◽  
Vol 2 (4) ◽  
pp. 36 ◽  
Author(s):  
Alessio D’Ambros ◽  
Timoleon Kipouros ◽  
Pavlos Zachos ◽  
Mark Savill ◽  
Ernesto Benini
Keyword(s):  
Design Space ◽  
Computational Design ◽  
Free Form ◽  
Design Parameters ◽  
Heuristic Optimization ◽  
Objective Functions ◽  
Pressure Losses ◽  
Optimization Study ◽  
Free Form Deformation ◽  
Computational Fluid Dynamics Cfd

In this work, we investigate the computational design of a typical S-Duct that is found in the literature. We model the design problem as a shape optimization study. The design parameters describe the 3D geometrical changes to the shape of the S-Duct and we assess the improvements to the aerodynamic behavior by considering two objective functions: the pressure losses and the swirl. The geometry management is controlled with the Free-Form Deformation (FFD) technique, the analysis of the flow is performed using steady-state computational fluid dynamics (CFD), and the exploration of the design space is achieved using the heuristic optimization algorithm Tabu Search (MOTS). The results reveal potential improvements by 14% with respect to the pressure losses and by 71% with respect to the swirl of the flow. These findings exceed by a large margin the optimality level that was achieved by other approaches in the literature. Further investigation of a range of optimum geometries is performed and reported with a detailed discussion.

Reliable FE Modeling of Chord-Wise Blade Modes in Compressor Design Process

2010 ◽  
Author(s):  
Ilya Fedorov ◽  
Jaroslaw Szwedowicz ◽  
Wolfgang Kappis ◽  
Igor Putchkov
Keyword(s):  
Design Process ◽  
Axial Compressor ◽  
Compressor Blade ◽  
Design Parameters ◽  
Concept Design ◽  
Compressor Blades ◽  
Mechanical Integrity ◽  
Resonance Frequencies ◽  
Local Flexibility ◽  
Compressor Efficiency

To meet the highest compressor efficiency and resonance free operation, the design process of a modern compressor blade requires several iterations between the aerodynamic and mechanical integrity disciplines. The 1D beam theories, usually used in the concept design process, do not consider the local flexibility of a flat, tapered and twisted geometry of an axial compressor airfoil. Therefore, chord-wise bending resonances of the compressor blade, excited by flow field upstream and downstream, cannot be predicated in a reliable manner. In the paper, firstly the sensitivity of compressor blade vibrations is analysed in terms of airfoil design parameters, rotor coupling effects, and mistuning phenomena. Owing to high bending stiffness of a welded shaft, a numerical CWB tool is developed mainly for reliable predictions of chord-wise bending resonances of the compressor blade in the design process. Finally, the tool reliability is demonstrated by a good agreement of the numerical and experimental resonance frequencies, which have been measured with the tip-timing system at the front stage of the axial compressor in the field. Regarding the measured compressor bladed disc, the numerical sensitive study is carried out to determine an impact of contact uncertainties in the blade root on the computed resonance frequencies. The paper shows how physical uncertainties of the root contact and airfoil mistuning are involved in practical manner into the design process of compressor blades. In the design process, the presented CWB tool allows for fast and reliable mitigation of chord-wise bending resonances, which requires the collective solution between the aerodynamics and mechanical integrity disciplines, as it is illustrated in this paper.

Robust Compressor Blades for Desensitizing Operational Tip Clearance Variations

2014 ◽  
Author(s):  
Pranay Seshadri ◽  
Shahrokh Shahpar ◽  
Geoffrey T. Parks
Keyword(s):  
Robust Design ◽  
Total Pressure ◽  
Pressure Rise ◽  
Side Surface ◽  
Tip Clearance ◽  
Design Parameters ◽  
Compressor Blades ◽  
Robust Designs ◽  
Multi Objective ◽  
Mean And Variance

Robust design is a multi-objective optimization framework for obtaining designs that perform favorably under uncertainty. In this paper robust design is used to redesign a highly loaded, transonic rotor blade with a desensitized tip clearance. The tip gap is initially assumed to be uncertain from 0.5 to 0.85% span, and characterized by a beta distribution. This uncertainty is then fed to a multi-objective optimizer and iterated upon. For each iteration of the optimizer, 3D-RANS computations for two different tip gaps are carried out. Once the simulations are complete, stochastic collocation is used to generate mean and variance in efficiency values, which form the two optimization objectives. Two such robust design studies are carried out: one using 3D blade engineering design parameters (axial sweep, tangential lean, re-cambering and skew) and the other utilizing suction and pressure side surface perturbations (with bumps). A design is selected from each Pareto front. These designs are robust: they exhibit a greater mean efficiency and lower variance in efficiency compared to the datum blade. Both robust designs were also observed to have significantly higher aft and reduced fore tip loading. This resulted in a weaker clearance vortex, wall jet and double leakage flow, all of which lead to reduced mixed-out losses. Interestingly, the robust designs did not show an increase in total pressure at the tip. It is believed that this is due to a trade-off between fore-loading the tip and obtaining a favorable total pressure rise and higher mixed-out losses, or aft-loading the tip, obtaining a lower pressure rise and lower mixed-out losses.

The Engagement of Hybrid Ultra High Space Division Multiplexing with Maximum Time Division Multiplexing Techniques for High-Speed Single-Mode Fiber Cable Systems

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
I. S. Amiri ◽  
P. G. Kuppusamy ◽  
Ahmed Nabih Zaki Rashed ◽  
P. Jayarajan ◽  
M. R. Thiyagupriyadharsan ◽  
...  
Keyword(s):  
Communication Systems ◽  
High Speed ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Design Parameters ◽  
Control Parameters ◽  
Data Rates ◽  
Fiber Optic Communication ◽  
High Space ◽  
Optic Communication

AbstractHigh-speed single-mode fiber-optic communication systems have been presented based on various hybrid multiplexing schemes. Refractive index step and silica-doped germanium percentage parameters are also preserved during their technological boundaries of attention. It is noticed that the connect design parameters suffer more nonlinearity with the number of connects. Two different propagation techniques have been used to investigate the transmitted data rates as a criterion to enhance system performance. The first technique is soliton propagation, where the control parameters lead to equilibrium between the pulse spreading due to dispersion and the pulse shrinking because of nonlinearity. The second technique is the MTDM technique where the parameters are adjusted to lead to minimum dispersion. Two cases are investigated: no dispersion cancellation and dispersion cancellation. The investigations are conducted over an enormous range of the set of control parameters. Thermal effects are considered through three basic quantities, namely the transmission data rates, the dispersion characteristics, and the spectral losses.

scholarly journals Optimal Pressure Boundary Control of Steady Multiscale Fluid-Structure Interaction Shell Model Derived from Koiter Equations

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 149
Author(s):  
Andrea Chierici ◽  
Leonardo Chirco ◽  
Sandro Manservisi
Keyword(s):  
Optimal Control ◽  
Solid Wall ◽  
Fluid Structure Interaction ◽  
Computational Cost ◽  
Robin Boundary Condition ◽  
Design Parameters ◽  
Fluid Structure ◽  
Control Approach ◽  
Structure Interaction ◽  
Fluid Boundary

Fluid-structure interaction (FSI) problems are of great interest, due to their applicability in science and engineering. However, the coupling between large fluid domains and small moving solid walls presents numerous numerical difficulties and, in some configurations, where the thickness of the solid wall can be neglected, one can consider membrane models, which are derived from the Koiter shell equations with a reduction of the computational cost of the algorithm. With this assumption, the FSI simulation is reduced to the fluid equations on a moving mesh together with a Robin boundary condition that is imposed on the moving solid surface. In this manuscript, we are interested in the study of inverse FSI problems that aim to achieve an objective by changing some design parameters, such as forces, boundary conditions, or geometrical domain shapes. We study the inverse FSI membrane model by using an optimal control approach that is based on Lagrange multipliers and adjoint variables. In particular, we propose a pressure boundary optimal control with the purpose to control the solid deformation by changing the pressure on a fluid boundary. We report the results of some numerical tests for two-dimensional domains to demonstrate the feasibility and robustness of our method.

Airfoil Optimization Using Area-Preserving Free-Form Deformation

2015 ◽  
Author(s):  
Stavros N. Leloudas ◽  
Giorgos A. Strofylas ◽  
Ioannis K. Nikolos
Keyword(s):  
Cross Sectional Area ◽  
Equality Constraint ◽  
Optimization Process ◽  
Free Form ◽  
Sectional Area ◽  
Cross Sectional ◽  
Airfoil Optimization ◽  
Free Form Deformation ◽  
Correction Problem ◽  
Area Preserving

Given the importance of structural integrity of aerodynamic shapes, the necessity of including a cross-sectional area equality constraint among other geometrical and aerodynamic ones arises during the optimization process of an airfoil. In this work an airfoil optimization scheme is presented, based on Area-Preserving Free-Form Deformation (AP FFD), which serves as an alternative technique for the fulfillment of a cross-sectional area equality constraint. The AP FFD is based on the idea of solving an area correction problem, where a minimum possible offset is applied on all free-to-move control points of the FFD lattice, subject to the area preservation constraint. Due to the linearity of the area constraint in each axis, the extraction of an inexpensive closed-form solution to the area preservation problem is possible by using Lagrange Multipliers. A parallel Differential Evolution (DE) algorithm serves as the optimizer, assisted by two Artificial Neural Networks as surrogates. The use of multiple surrogate models, in conjunction with the inexpensive solution to the area correction problem, render the optimization process time efficient. The application of the proposed methodology for wind turbine airfoil optimization demonstrates its applicability and effectiveness.

Shape Optimization by Free-Form Deformation: Existence Results and Numerical Solution for Stokes Flows

2013 ◽  
Vol 60 (3) ◽  
pp. 537-563 ◽  
Author(s):  
Francesco Ballarin ◽  
Andrea Manzoni ◽  
Gianluigi Rozza ◽  
Sandro Salsa
Keyword(s):  
Shape Optimization ◽  
Numerical Solution ◽  
Existence Results ◽  
Free Form ◽  
Stokes Flows ◽  
Free Form Deformation

Fully Free-Form Deformation Features (δ-F4) Incorporating Discontinuities

2004 ◽  
Author(s):  
Vincent Cheutet ◽  
Jean-Philippe Pernot ◽  
Jean-Claude Leon ◽  
Bianca Falcidieno ◽  
Franca Giannini
Keyword(s):  
Surface Deformation ◽  
Geometric Constraints ◽  
Free Form ◽  
Initial Surface ◽  
Cad Systems ◽  
Free Form Deformation ◽  
Deformation Features ◽  
Generate Surface ◽  
Prototype Software ◽  
Free Form Surfaces

To limit low-level manipulations of free-form surfaces, the concept of Fully Free Form Deformation Features (δ-F4) have been introduced. They correspond to shapes obtained by deformation of a surface area according to specified geometric constraints. In our work, we mainly focused on those features aimed at enforcing the visual effect of the so-called character lines, extensively used by designers to specify the shape of an object. Therefore, in the proposed approach, 3D lines are used to drive surface deformation over specified areas. Depending on the wished shape and reflection light effects, the insertion of character lines may generate surface tangency discontinuities. In CAD systems, such kind of discontinuities is generally created by a decomposition of the initial surface into several patches. This process can be tedious and very complex, depending on the shape of the deformation area and the desired surface continuity. Here, a method is proposed to create discontinuities on a surface, using the trimming properties of surfaces. The corresponding deformation features produce the resulting surface in a single modification step and handle simultaneously more constraints than current CAD systems. The principle of the proposed approach is based on arbitrary shaped discontinuities in the parameter domain of the surface to allow the surface exhibiting geometric discontinuities at user-prescribed points or along lines. The proposed approach is illustrated with examples obtained using our prototype software.

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