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Symmetric bursting behaviors in the generalized FitzHugh-Nagumo model
, Article Biological Cybernetics ; Volume 107, Issue 4 , 2013 , Pages 465-476 ; 03401200 (ISSN) ; Fallah, H ; Razvan, M. R ; Sharif University of Technology
2013
Abstract
In the current paper, we have investigated the generalized FitzHugh-Nagumo model. We have shown that symmetric bursting behaviors of different types could be observed in this model with an appropriate recovery term. A modified version of this system is used to construct bursting activities. Furthermore, we have shown some numerical examples of delayed Hopf bifurcation and canard phenomenon in the symmetric bursting of super-Hopf/homoclinic type near its super-Hopf and homoclinic bifurcations, respectively
Canard-wing interactions in subsonic flow
, Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 37, Issue M2 , 2013 , Pages 133-147 ; 22286187 (ISSN) ; Davari, A. R ; Soltani, M. R ; Sharif University of Technology
Shiraz University
2013
Abstract
Extensive subsonic wind tunnel tests were conducted on a coplanar wing-canard configuration at various angles of attack. In these experiments, a 60° swept canard was placed upstream of a 60° swept main delta wing. This paper deals with the distribution of mean and fluctuating pressure coefficients on the upper surfaces of both the canard and the wing immersed in a variety of angles of attack. According to the results, presence of canard postpones the vortex formation and growth on the wing to higher angles of attack compared to the canard-off case. Due to the canard downwash field, the wing operates at lower effective angles of attack and therefore, its vortex breakdown is delayed. The...
Oscillations in Neuronal Dynamical Systems
, M.Sc. Thesis Sharif University of Technology ; Razvan, Mohammad Reza (Supervisor)
Abstract
Periodic orbits are one of the basic objects of interest in Dynamical systems. And methods for detecting, counting and determining the periods of periodic orbits are of great interest. In spite of this interest, periodic orbits remain difficult to detect. The most celebrated existence result is the Poincare-Bendixson theorem. Unfortunately, this theorem is false in general for higher dimensional systems. The success of fixed point theory inspired the hope that similar topological techniques could be of use in proving the existence of periodic orbits. In this Thesis we have analyzed some topological and geometrical theories which could be of use in proving the existence of periodic orbits....
Canard flow improvement in a split canard configuration
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 6 , 2015 , Pages 1076-1087 ; 09544100 (ISSN) ; Askari, F ; Soltani, M. R ; Sharif University of Technology
Abstract
Extensive low-speed wind-tunnel tests are performed to study the flow field structure over a dual-surface canard, known as split canard, in comparison to the conventional configurations. Surface pressure for both steady deflections and unsteady oscillations of the canard are measured and compared for both canard-alone and split-canard cases. The split canard shows a superior advantage at high angles of attack, where a delay in the vortex breakdown phenomena on the canard surface is observed. For the split-canard configuration, the downwash of the front canard reduces the effective angle of attack at the inboard section of the rear element which postpones formation of the leading-edge vortex....
Effects of canard position on wing surface pressure
, Article Scientia Iranica ; Volume 17, Issue 2 B , 2010 , Pages 136-145 ; 10263098 (ISSN) ; Askari, F ; Davari, A. R ; Nayebzadeh, A ; Sharif University of Technology
2010
Abstract
A series of wind tunnel tests were performed to study the effects of a canard and its position on the downstream flowfield over the wing surface. The wing surface pressure was measured for both canard-off and canard-on configurations. In addition, the canard position effects on the wing were investigated at different angles of attack. The canard was installed at three vertical positions and at two different horizontal distances from the wing apex. The results show a remarkable increase in the wing suction peak for the canard-on configurations. At low to moderate angles of attack, among the various configurations examined in the present experiments, the mid-canard configuration developed a...
Experimental Investigation of Flow Past a Delta Wing Model in Presence of a Canard in Supersonic Regime
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Application of canard next to the wing have been widely used in military industry for decades. Although it’s most application is in supersonic flying objects, It has to do it’s duty in lower air speeds too. The aim of this study was to investigate the influence on the wing due to the presence of canard in supersonic flow regime. But because of the importance of the issue, significant attempts has been conducted in subsonic flow regime. High research volume, Absence of a comprehensive theory in this branch and the local defense industry demand as a developing country on the other hand, delivers the importance and applicability of the subject. Another issue of importance is that the...
Experimental Investigation of the Effects of Canard Position on the Flowfield Over the Wing of a Model
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
The analysis results of air combat simulations explain fighters succeed at close air combat that are super maneuverable and at high angle of attack controllable. Closed-coupled delta wing/canard configurations play an important role in modern aircraft design. These configurations offer high trimmed lift, improved agility and maneuverability as well, as a potential for increased lift-to drag ratio, all of which make them attractive to study. Experiments were carried out in a subsonic closed circuit wind tunnel over a delta wing model under the influence of canard. Canard was set in two different vertical positions, high and mid, with respect to the wing location. Flowfield measurements were...
On the existence of canards in a nonlinear fluid system manifesting oscillatory behaviour
, Article International Journal of Non-Linear Mechanics ; Volume 98 , 2018 , Pages 58-63 ; 00207462 (ISSN) ; Lundberg, P ; Razvan, M. R ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In an earlier study dealing with a nonlinear fluid oscillator governed by two autonomous ODEs, the solutions were found to display some aberrant characteristics adjacent to the boundaries of the oscillatory regime in parameter space. It was argued that this behaviour indicated the presence of canards. In the present study it is formally proved that this indeed is the case, and some numerical examples illustrating the phenomenon as well as its effects are presented. © 2017 Elsevier Ltd
Canards in Complex Oscillatory Systems
, M.Sc. Thesis Sharif University of Technology ; Razvan, Mohammad Reza (Supervisor)
Abstract
Canard, first observed in Van der Pol oscillations, is a typical phenomenon in oscillatory systems. Canard is also observed in many oscillatory systems such as electrical circuits and neurons. In many fields of science and engineering there are complex oscillations that exhibit canard for certain values of parameters. These three dimensional systems exhibit complex oscillatory behavior never observed in two dimensional dynamics. Some of these systems are chaotic for certain parameter values. It seems than in oscillatory systems canards can make complex behavior. Several methods such as the singular perturbation theory have been used to study this complexity. In this project, we study canard...
Reducing wind tunnel data for flowfield study over the wing-canard configuration using neural network
, Article 42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 5 January 2004 through 8 January 2004 ; 2004 , Pages 8371-8377 ; Masdari, M ; Sharif University of Technology
2004
Abstract
The objective of this paper is study of flowfield over the wing of a coplanar and close-coupled wing-canard configuration model using neural network, in order to reduce measurement points and experiment time. The results are based on flowfield pressure and wing surface pressure measurements at difference angles of attack, no sideslip and difference angles of canard. A GRNN (General Regression Neural Network) algorithm is developed to determine the shape and trajectory of vortices over this model. This network uses the total pressure coefficients of flowfield over the wing of this model that are obtained by total pressure probe as its input. The data presented to the network are processed to...