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Aerodynamic Optimization of Transonic Airfoils and Wings by Using Shock Control Bump, Suction and Blowing with Adjoint Method
, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
Shock control bump (SCB) and suction and blowing are flow control methods used to control the shock wave/boundary layer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. A SCB uses a small local surface deformation to reduce the shock-wave strength, while suction decreases the boundary-layer thickness and blowing delays the flow separation. Here, a single-point, a multi-point, and a robust optimization method are used to find the optimum design of SCB and suction and blowing. The flow control methods are used separately or together on two transonic airfoils i.e.; RAE-2822 and NACA-64A010 for a wide range of off-design transonic Mach numbers. The RANS flow...
Development of Neutron Noise Simulator Based on the Boundary Element Method
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Aboulfazl (Supervisor)
Abstract
The present M.Sc. thesis consists of two sections including static calculation and neutron noise calculations in rectangular and hexagonal geometries. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equation is based on Boundary Element Method (BEM). The result are benchmarked against the valid results for BIBLIS-2D and IAEA -2D benchmark problem. In the second section, neutron noise calculation are performed for two types of noise sources, i.e. absorber of variable strength and Inadvertent Loading and Operation of a Fuel Assembly in an Improper Position (ILOFAIP). The...
Localization of a Postulated Noise in VVER-1000 Reactor Core Using Neutron Noise Analysis Methods
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
In this thesis, localization of a postulated noise from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. Using the discretised static equations, a 2-D 2-group static simulator (HEXDIF-2) is developed which its results are benchmarked against the well-known CITATION...
Calculation of the Scaling Factor for WWER-1000 Reactor (Boushehr)
,
M.Sc. Thesis
Sharif University of Technology
;
Vossoughi, Nasser
(Supervisor)
Development of Parallel Algorithm for Adjoint Optimization of Turbine Blade
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
This study develops an aerodynamic shape optimization code using parallel processing capability based on a gradient-based adjoint method. Calculation of the gradient of the objective function with respect to design variables is the most costly part of the gradient-based optimization algorithms. Applying adjoint methods, gradients can be calculated with solving some additional equations known as the "adjoint equations", instead of direct calculation. In this study, the blade shape optimization is performed by inverse design method and using steepest descent optimization algorithm. The objective function of inverse design problem is the desired blade surface pressure distribution. In each...
Accelerating MCNP using the Adjoint Flux
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor) ; Ayyoubzadeh, Mohsen (Co-Advisor)
Abstract
Nuclear engineering simulation requires computer codes which are capable of particle transportation and presenting valid answers. The Monte Carlo method is one of the particle transportation methods and the MCNP code is also a common and efficient code using Monte Carlo method. We usually come across statistical errors in Monte Carlo simulation for reducing which a number of methods have been presented which are called variance reduction methods. In simulating deep penetrating problems, analog Monte Carlo method is weak which leads to considerable error. The chosen variance reduction method for this study is the one which uses adjoint flux. In this study, a 3D deterministic transport code...
Three-dimensional Aerothermal Shape Optimization of Turbine Blade, Using Gradient Adjoint-based Methods
, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
The most important challenge and the most time consuming part of the gradient based optimization algorithms in the aerodynamic shape optimization problems is the evaluation of the sensitivity of the objective function with respect to the design variables. The adjoint method which has been the subject of many research in the recent three decades, is capable of computing the complete gradient information needed for optimization by solving the governing flow equations and their corresponding adjoint equations only once, regardless of the number of design parameters. In this study, the continues adjoint equations for compressible inviscid and viscous flows are derived and the formulation of...
Aerodynamic Optimization of Axial Compressors Using Adjoint Equations
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
In this study, aerodynamic shape optimization of axial compressors is considered. In order to optimization, one of the gradient based optimization algorithms, namely Adjoint method, is used. Recently, Adjoint method has been emerged as one of the reliable gradient based optimization algorithms in turbomahineries applications. Because this method is a gradient method of optimization, similar to the other entire gradient based algorithms, adjoint method also has a better convergence than non-gradient based optimization algorithms. In this work, aerodynamic shape optimization of two-dimensional cross section through a transonic axial compressor is studied. The process is considered for midspan...
Aerodynamic Shape Optimization of Airfoils Using Adjoint Equations
,
M.Sc. Thesis
Sharif University of Technology
;
Mazaheri, Karim
(Supervisor)
Abstract
Adjoint-based aerodynamic optimization has drawn much attention, recently. It is based on gradient optimization procedures and requires the sensitivities of the design variables to find the optimized shape. The advantage of this method is that it estimates the sensitivities by solving an “adjoint equation”, instead of calculating them directly. In this thesis, the method is used to design airfoil shapes both in inviscid and viscous flows. In this regard, a flow solver and an adjoint solver have been developed. First, the validity of the flow solver is tested according to credited data form papers and softwares. Then, the optimizing program is tested using some inverse design problems....
Investigation on Improving Direct Discrete Method and its Application in Adjoint Diffusion Equation Numerical Solvers
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
Numerical analysis method improvement is a topic of interest among all engineering disciplines. Regarding the fact that our ability to predict the behavior of a physical system is often limited by our computational resources, the efficiency of the employed numerical method is an important factor in the degree of approximation used in modeling. One of the recent numerical methods is the Cell Method (CM), which is also known as the Direct Discrete Method (DDM). This method combines some features of a variety of methods, especially finite volume and finite element, and gains some insight from the graph theory used in network analysis. The result is a method in which the set of equations which...
Turbine blade aerodynamic optimization on unstructured grids using a continuous adjoint method
, Article ASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012, Houston, TX, 9 November 2012 through 15 November 2012 ; Volume 1 , 2012 , Pages 425-431 ; 9780791845172 (ISBN) ; Mazaheri, K ; Irannejad, A ; Sharif University of Technology
2012
Abstract
A gradient based optimization using the continuous adjoint method for inverse design of a turbine blade cascade is presented. The advantage of the adjoint method is that the objective function gradients can be evaluated by solving the adjoint equations with coefficients depending on the flow variables. This method is particularly suitable for aerodynamic design optimization for which the number of design variables is large. Bezier polynomials are used to parameterize suction side of the turbine blade. The numerical convective fluxes of both flow and adjoint equations are computed by using a Roe-type approximate Riemann solver. An approximate linearization is applied to simplify the...
A coupled adjoint formulation for non-cooled and internally cooled turbine blade optimization
, Article Applied Thermal Engineering ; Volume 105 , 2016 , Pages 327-335 ; 13594311 (ISSN) ; Mazaheri, K ; Chaharlang Kiani, K ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Most researches on the application of the adjoint method in turbine blade design are concentrated on the aerodynamic shape optimization without considering the heat transfer to/from the blade material. In this study, the adjoint method is extended to the conjugate heat transfer problems in which the viscous flow field is coupled to heat transfer in the solid region. Introducing a new adjoint variable in the solid domain, a heat adjoint equation is derived which is coupled with the energy adjoint equation in the fluid zone at the fluid/solid interface. The detailed mathematical description associated with the derivation of the heat adjoint equation with corresponding boundary conditions are...
Entropy minimization in turbine cascade using continuous adjoint formulation
, Article Engineering Optimization ; Volume 48, Issue 2 , 2016 , Pages 213-230 ; 0305215X (ISSN) ; Mazaheri, K ; Sharif University of Technology
Taylor and Francis Ltd
Abstract
A complete continuous adjoint formulation is presented here for the optimization of the turbulent flow entropy generation rate through a turbine cascade. The adjoint method allows one to have many design variables, but still afford to compute the objective function gradient. The new adjoint system can be applied to different structured and unstructured grids as well as mixed subsonic and supersonic flows. For turbulent flow simulation, the k-ω shear-stress transport turbulence model and Roe's flux function are used. To ensure all possible shape models, a mesh-point method is used for design parameters, and an implicit smoothing function is implemented to avoid the generation of non-smoothed...
Enhanced finite difference scheme for the neutron diffusion equation using the importance function
, Article Annals of Nuclear Energy ; Volume 96 , 2016 , Pages 412-421 ; 03064549 (ISSN) ; Vosoughi, N ; Gharib, M ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Mesh point positions in Finite Difference Method (FDM) of discretization for the neutron diffusion equation can remarkably affect the averaged neutron fluxes as well as the effective multiplication factor. In this study, by aid of improving the mesh point positions, an enhanced finite difference scheme for the neutron diffusion equation is proposed based on the neutron importance function. In order to determine the neutron importance function, the adjoint (backward) neutron diffusion calculations are performed in the same procedure as for the forward calculations. Considering the neutron importance function, the mesh points can be improved through the entire reactor core. Accordingly, in...
Optimal design of multiphase composites under elastodynamic loading
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 300 , 2016 , Pages 265-293 ; 00457825 (ISSN) ; Sharif University of Technology
Elsevier
2016
Abstract
An algorithm is proposed to optimize the performance of multiphase structures (composites) under elastodynamic loading conditions. The goal is to determine the distribution of material in the structure such that the time-averaged total stored energy of structure is minimized. A penalization strategy is suggested to avoid the checkerboard instability, simultaneously to generate near 0-1 topologies. As a result of this strategy, the solutions of presented algorithm are sufficiently smooth and possess the regularity of H1 function space. A simple method for the continuum adjoint sensitivity analysis of the corresponding PDE-constrained optimization problem is presented. It is general and can be...
Thermal optimization of the continuous casting process using distributed parameter identification approach—controlling the curvature of solid-liquid interface
, Article International Journal of Advanced Manufacturing Technology ; Volume 94, Issue 1-4 , 2018 , Pages 1101-1118 ; 02683768 (ISSN) ; Sharif University of Technology
Springer London
2018
Abstract
Thermal optimization of the vertical continuous casting process is considered in the present study. The goal is to find the optimal distribution of the temperature and interfacial heat transfer coefficients corresponding to the primary and secondary cooling systems, in addition to the pulling speed, such that the solidification along the main axis of strand approaches to the unidirectional solidification mode. Unlike many thermal optimization of phase change problems in which the desirable (target) temperature, temperature gradient, or interface position are assumed to be a priori known, a desirable shape feature of the freezing interface (not its explicit position) is assumed to be known in...
Drag reduction by a multi-point optimised hybrid flow control method for two supercritical airfoils
, Article European Journal of Computational Mechanics ; Volume 25, Issue 5 , 2016 , Pages 359-387 ; 17797179 (ISSN) ; Mazaheri, K ; Sharif University of Technology
Taylor and Francis Ltd
Abstract
Shock control bump (SCB), suction and blowing are three flow control methods used to control the shock wave/boundary layer interaction to reduce the resulting wave drag in transonic flows. An SCB uses a small local surface deformation to reduce the shock wave strength, while the suction decreases the boundary layer thickness and the blowing delays the flow separation. Here, we will use a multi-point continuous adjoint optimisation scheme to find the optimum design of suction and blowing separately or together, or with the SCB, on two supercritical airfoils, i.e. RAE-5225 and RAE-2822, for a wide range of off-design transonic Mach numbers. The RANS flow equations are solved using the Roe’s...
Performance improvement of a supercritical airfoil by a multi-point optimized shock control channel
, Article Flow, Turbulence and Combustion ; 2017 , Pages 1-29 ; 13866184 (ISSN) ; Mazaheri, K ; Sharif University of Technology
Abstract
A shock control channel (SCC) is a flow control method introduced here to control the shock wave/boundarylayer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. An SCC transfers an appropriate amount of mass and momentum from downstream of the shock wave location to its upstream to decrease the pressure gradient across the shock wave and as a result the shock-wave strength is reduced. Here, a multi-point optimization method under a constant-lift-coefficient constraint is used to find the optimum design of the SCC. This flow control method is implemented on a RAE-2822 supercritical airfoil for a wide range of off-design transonic Mach numbers. The RANS flow...
Application of the adjoint optimisation of shock control bump for ONERA-M6 wing
, Article European Journal of Computational Mechanics ; Volume 26, Issue 5-6 , 2017 , Pages 557-583 ; 17797179 (ISSN) ; Mazaheri, K ; Sharif University of Technology
Abstract
This article is devoted to the numerical investigation of the shock wave/boundary layer interaction (SWBLI) as the main factor influencing the aerodynamic performance of transonic bumped airfoils and wings. The numerical analysis is conducted for the ONERA-M6 wing through a shock control bump (SCB) shape optimisation process using the adjoint optimisation method. SWBLI is analyzed for both clean and bumped airfoils and wings, and it is shown how the modified wave structure originating from upstream of the SCB reduces the wave drag, by improving the boundary layer velocity profile downstream of the shock wave. The numerical simulation of the turbulent viscous flow and a gradient-based adjoint...
Performance improvement of a supercritical airfoil by a multi-point optimized shock control channel
, Article Flow, Turbulence and Combustion ; Volume 100, Issue 3 , 2018 , Pages 675-703 ; 13866184 (ISSN) ; Mazaheri, K ; Sharif University of Technology
Springer Netherlands
2018
Abstract
A shock control channel (SCC) is a flow control method introduced here to control the shock wave/boundarylayer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. An SCC transfers an appropriate amount of mass and momentum from downstream of the shock wave location to its upstream to decrease the pressure gradient across the shock wave and as a result the shock-wave strength is reduced. Here, a multi-point optimization method under a constant-lift-coefficient constraint is used to find the optimum design of the SCC. This flow control method is implemented on a RAE-2822 supercritical airfoil for a wide range of off-design transonic Mach numbers. The RANS flow...