Aerodynamic Sensitivity Analysis Methods for the Compressible Euler Equations

1991 ◽  
Vol 113 (4) ◽  
pp. 681-688 ◽  
Author(s):  
Oktay Baysal ◽  
Mohamed E. Eleshaky
Keyword(s):  
Sensitivity Analysis ◽  
Euler Equations ◽  
Analytical Approach ◽  
Direct Method ◽  
Pressure Coefficient ◽  
Mathematical Formulation ◽  
Computational Time ◽  
Algebraic Equations ◽  
Sensitivity Coefficients ◽  
Linear Algebraic Equations

A mathematical formulation is developed for aerodynamic sensitivity coefficients based on a discretized form of the compressible, two-dimensional Euler equations. A brief motivating introduction to the aerodynamic sensitivity analysis and the reasons behind an integrated flow/sensitivity analysis for design algorithms are presented. Two approaches to determine the aerodynamic sensitivity coefficients, namely, the finite difference approach, and the quasi-analytical approach are discussed with regards to their relative accuracies and involved computational efforts. In the quasi-analytical approach, the direct and the adjoint variable methods are formulated and assessed. Also, several methods to solve the system of linear algebraic equations, that arises in the quasi-analytical approach, are investigated with regards to their accuracies, computational time and memory requirements. A new flow prediction concept, which is an outcome of the direct method in the quasi-analytical approach, is developed and illustrated with an example. Surface pressure coefficient distributions of a nozzle-afterbody configuration obtained from the predicted flow-field solution are compared successfully with their corresponding values obtained from a flowfield analysis code and the experimental data.

An Efficient Algorithm for Fluid Force and its Jacobian Matrix in Journal Bearing

2005 ◽  
Vol 128 (2) ◽  
pp. 291-295 ◽  
Author(s):  
Zhonghui Xiao ◽  
Liping Wang ◽  
Tiesheng Zheng
Keyword(s):  
Efficient Algorithm ◽  
Journal Bearing ◽  
Jacobian Matrix ◽  
Direct Method ◽  
Current Method ◽  
Computational Time ◽  
Operational Characteristic ◽  
Algebraic Equations ◽  
Fluid Force ◽  
Linear Algebraic Equations

Based on the theory of variational inequality, a rapid efficient algorithm for fluid force and its Jacobian matrix in journal bearing is presented in this paper. Primarily, to solve the fluid force is transformed to solve a set of linear algebraic equations with tri-diagonal coefficient matrices. Meanwhile, an amendatory direct-method is proposed to solve the united equations about fluid forces and their Jacobian matrices, rapidly and synchronously. The Reynolds boundary condition has to be satisfied automatically during the process. Secondly, the coefficient matrices, which are involved in the previous process, can be decomposed to an assembly of a part of relative with journal motion and a part of invariable matrix, which can be prepared in advance and be referred to later repeatedly. Through these measures, many redundant operations are avoided. The numerical examples show that, under the accuracy guaranteed, the algorithm in this paper can reduce computational time remarkably, which reveals that the current method has a good operational characteristic and practicability.

ON SOFTWARE IMPROVEMENT OF IMAGE CHANNEL SUPPRESSION IN SDR RECEIVERS WITH ANALOG CONVERSION TO A LOW INTERMEDIATE FREQUENCY

2020 ◽  
pp. 45-52
Author(s):  
A. S. Yurkov
Keyword(s):  
Signal Processing ◽  
Direct Method ◽  
Digital Signal ◽  
Intermediate Frequency ◽  
Algebraic Equations ◽  
Recursive Filter ◽  
Linear Algebraic Equations ◽  
Reception Channel ◽  
Image Channel ◽  
Parasitic Phase

A method for digital signal processing in SDR receivers with analog conversion to a low intermediate frequency is proposed. In contrast to known systems, the proposed approach does not consider parasitic phase and amplitude distortions, but uses the direct method minimizing of the signal of the mirror reception channel. Generally speaking, this can be done simultaneously at several frequencies. It is shown that in computational terms, this is reduced to signal processing by an algorithm similar to a digital non-recursive filter, and to determine its coefficients, it is sufficient to solve a system of linear algebraic equations.

scholarly journals Development of a finite-element-based design sensitivity analysis for buckling and postbuckling of composite plates

1995 ◽  
Vol 1 (3) ◽  
pp. 255-274 ◽  
Author(s):  
Ruijiang Guo ◽  
Aditi Chattopadhyay
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Linear Equations ◽  
Composite Plates ◽  
Material Model ◽  
Design Sensitivity ◽  
Algebraic Equations ◽  
Sensitivity Derivatives ◽  
Analysis Technique ◽  
Linear Algebraic Equations

A finite element based sensitivity analysis procedure is developed for buckling and postbuckling of composite plates. This procedure is based on the direct differentiation approach combined with the reference volume concept. Linear elastic material model and nonlinear geometric relations are used. The sensitivity analysis technique results in a set of linear algebraic equations which are easy to solve. The procedure developed provides the sensitivity derivatives directly from the current load and responses by solving the set of linear equations. Numerical results are presented and are compared with those obtained using finite difference technique. The results show good agreement except at points near critical buckling load where discontinuities occur. The procedure is very efficient computationally.

Quasi-Analytic Sensitivity Analysis of a Unified Viscoplastic Constitutive Model for a Solder Alloy

1997 ◽  
Vol 50 (11S) ◽  
pp. S44-S49 ◽  
Author(s):  
Martin A. Eisenberg ◽  
Erhard Krempl ◽  
Luca Maciucescu
Keyword(s):  
Sensitivity Analysis ◽  
Solder Alloy ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Professional Judgment ◽  
Multidisciplinary Teams ◽  
Algebraic Equations ◽  
Linear Algebraic Equations ◽  
Engineering Alloys ◽  
High Homologous Temperature

Unified constitutive models for the consistent description of inelastic thermomechanical response of engineering alloys to widely varying control conditions are strongly nonlinear; there are numerous constants to be determined; and successful use depends critically on expert professional judgment. These circumstances are not unlike those associated with the design of complex systems dependent on successful interaction of multidisciplinary teams. Introduced in this paper is a paradigm for design of constitutive models motivated by modern system design methodologies. Specifically, a quasi-analytic sensitivity analysis is applied to a special form of a viscoplasticity-based overstress model (VBO) for the uniaxial, isothermal, high-homologous temperature mechanical response of a solder alloy. Parameter sensitivity is demonstrated via linear algebraic equations. The technique is a critical first step to application of sophisticated techniques of multidisciplinary design optimization (MDO) to constitutive modeling.

scholarly journals Flow modelling in a straight hard-walled duct with two rectangular axisymmetric narrowings

2020 ◽  
Keyword(s):  
Computational Time ◽  
Computational Domain ◽  
Algebraic Equations ◽  
Governing Equations ◽  
Order Of Accuracy ◽  
First Order ◽  
Flow Modelling ◽  
Computational Mesh ◽  
Linear Algebraic Equations ◽  
Stability Of The Solution

A method for modelling the flow in a rigid-walled duct with two narrowings has been developed. It has the second order of accuracy in the spatial and the first order of accuracy in the temporal coordinates, provides high stability of the solution, and compared to the similar methods requires much less computational time to obtain a result. According to the method, the stream function and the vorticity are introduced initially, and consequently the transition from the governing equations, as well as the initial and boundary conditions to the proper relationships for the introduced variables is performed. The obtained relationships are rewritten in a non-dimensional form. After that a computational domain and a uniform computational mesh are chosen, and the corresponding discretization of the non-dimensional relationships is performed. Finally, the linear algebraic equations obtained as a result of the discretization are solved.

Heat and mass transfer analysis in unsteady titanium dioxide nanofluid between two orthogonally moving porous coaxial disks: a numerical study

2015 ◽  
Vol 93 (3) ◽  
pp. 290-299 ◽  
Author(s):  
Muhammad Farooq Iqbal ◽  
Kashif Ali ◽  
Muhammad Ashraf
Keyword(s):  
Mass Transfer ◽  
Titanium Dioxide ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Titanium Dioxide Nanoparticles ◽  
Direct Method ◽  
Fluid Velocity ◽  
Algebraic Equations ◽  
Electrically Conducting ◽  
Linear Algebraic Equations

Study of heat and mass transfer in an unsteady hydromagnetic viscous electrically conducting incompressible water-based nanofluid (containing titanium dioxide nanoparticles) between two orthogonally moving porous coaxial disks with suction and viscous dissipation effects. A combination of iterative and a direct method is employed for solving the sparse systems of linear algebraic equations arising from the finite difference discretization of the quasi-linearized self-similar ordinary differential equations. It has been noticed that the rate of mass transfer at the disks decreases with the permeability Reynolds number; either the disks are approaching or receding. Moreover, the external magnetic field remarkably reduces the fluid velocity and therefore may be used as a controlling agent for the flow.

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