scholarly journals Numerical Study of Reduced Frequency Effect on Longitudinal Stability Derivatives of Airfoil under Pitching and Plunging Oscillations

2016 ◽  
Vol 8 (3) ◽  
pp. 272-280 ◽  
Author(s):  
Vahid Nasr Esfahani ◽  
Mahmoud Mani
Keyword(s):  
Numerical Study ◽  
Frequency Effect ◽  
Longitudinal Stability ◽  
Reduced Frequency ◽  
Stability Derivatives ◽  
Derivatives Of

Aerodynamic Indicial Response and Stability Derivatives of a Rotor Annulus

1988 ◽  
Vol 110 (2) ◽  
pp. 178-184
Author(s):  
V. G. Mengle
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Pressure ◽  
Body Motion ◽  
Complex Frequency ◽  
Reduced Frequency ◽  
Stability Derivatives ◽  
Parametric Studies ◽  
Force Components ◽  
Derivatives Of ◽  
Initial Impulse

The key to finding the aerodynamic forces acting on a rotor in arbitrary rigid-body motion is its response to indicial input of its individual degrees of freedom. A theory is developed to find such indicial responses for an unloaded rotor annulus moving in its own plane. New rational approximations in the complex-frequency domain are used to find the corresponding transient cascade forces for incompressible flow. The indicial response consists of an initial impulse and an oscillatory decaying part for force components parallel and perpendicular to the applied motion. The harmonic response is also found and is expressed in terms of complex “rotor-stability-derivatives,” which are essentially the direct-and cross-coupled frequency dependent damping or stiffness force coefficients. Both responses are obtained explicitly in terms of the unsteady cascade characteristics and reduced frequency or time. Parametric studies indicate lowered damping, aerodynamic spring-softening and cross-stiffness whirling forces dependent on the upstream dynamic pressure for perturbation frequencies near the rotor speed.

scholarly journals A Preliminary Study of Parameter Estimation for Fixed Wing Aircraft and High Endurability Parafoil Aerial Vehicle

2020 ◽  
Vol 12 (4) ◽  
pp. 95-109
Author(s):  
Roli JAISWAL ◽  
Om PRAKASH ◽  
Sudhir Kumar CHATURVEDI
Keyword(s):  
System Identification ◽  
Dynamic Modelling ◽  
Mathematical Tool ◽  
Longitudinal Stability ◽  
Aerial Vehicles ◽  
Stability Derivatives ◽  
Aerial Vehicle ◽  
Identification Techniques ◽  
Derivatives Of ◽  
Powered Parafoil

High Endurability Aerial vehicle includes Airship, Powered parafoil aerial vehicle (PPAV). These flying aerial vehicles have excellent endurance and durability. Nowadays, research in lighter than air technology is pacing up fast. In the past years, the design and development of high endurable flying vehicle has grown due to their application in monitoring of floods/ drought, aerial photography, transportation, surveillance in terrain prone areas, reconnaissance missions etc. System Identification is a mathematical tool applied to develop mathematical model of any physical system based on measured data. Research on System Identification of these types of vehicles is on latest trends. Dynamic modelling of these types of vehicles is more complex than fixed wing aircraft. A detail Literature review in system Identification of PPAV and fixed wing aircraft is presented aiming to provide a source of information for researchers to make vehicle fully autonomous from manual controls. Various system Identification Techniques to estimate parameters of flying aerial vehicles are discussed. Longitudinal stability derivatives of fixed wing Hansa-3 aircraft and PPAV are compared. The methodology used in this study to estimate the longitudinal stability derivatives is ML Method. The results obtained in form of stability derivatives of Hansa-3 aircraft and Powered parafoil aerial vehicle are presented in tabular form. This study will give insight of identification techniques used to estimate parameters.

Numerical study of multi-dimensional hyperbolic telegraph equations arising in nuclear material science via an efficient local meshless method

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Imtiaz Ahmad ◽  
Aly R. Seadawy ◽  
Hijaz Ahmad ◽  
Phatiphat Thounthong ◽  
Fuzhang Wang
Keyword(s):  
Meshless Method ◽  
Material Science ◽  
Numerical Study ◽  
Research Work ◽  
Time Integration ◽  
Three Dimensional ◽  
Nuclear Material ◽  
Telegraph Equations ◽  
Model Equations ◽  
Derivatives Of

Abstract This research work is to study the numerical solution of three-dimensional second-order hyperbolic telegraph equations using an efficient local meshless method based on radial basis function (RBF). The model equations are used in nuclear material science and in the modeling of vibrations of structures. The explicit time integration technique is utilized to semi-discretize the model in the time direction whereas the space derivatives of the model are discretized by the proposed local meshless procedure based on multiquadric RBF. Numerical experiments are performed with the proposed numerical scheme for rectangular and non-rectangular computational domains. The proposed method solutions are converging quickly in comparison with the different existing numerical methods in the recent literature.

scholarly journals A numerical study into the longitudinal dynamic stability of the tailless aircraft

2019 ◽  
Vol 91 (3) ◽  
pp. 428-436 ◽  
Author(s):  
Agnieszka Kwiek
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Numerical Study ◽  
Aircraft Design ◽  
Content Type ◽  
Preliminary Stage ◽  
Longitudinal Dynamic ◽  
Stability Derivatives ◽  
The Impact ◽  
Tailless Aircraft

Purpose The purpose of this research is a study into a mathematical approach of a tailless aircraft dynamic stability analysis. This research is focused on investigation of influence of elevons (elevator) on stability derivatives and consequently on the aircraft longitudinal dynamic stability. The main research question is to determine whether this impact should be taken into account on the conceptual and preliminary stage of the analysis of the longitudinal dynamic stability. Design/methodology/approach Aerodynamic coefficients and longitudinal stability derivatives were computed by Panukl (panel methods). The analysis of the dynamic stability of the tailless aircraft was made by the Matlab code and SDSA package. Findings The main result of the research is a comparison of the dynamic stability of the tailless aircraft for different approaches, with and without the impact of elevator deflection on the trim drag and stability derivatives. Research limitations/implications This paper presents research that mostly should be considered on the preliminary stage of aircraft design and dynamic stability analysis. The impact of elevons deflection on the aircraft moment of inertia has been omitted. Practical implications The results of this research will be useful for the further design of small tailless unmanned aerial vehicles (UAVs). Originality/value This research reveals that in case of the analysis of small tailless UAVs, the impact of elevons deflection on stability derivatives is bigger than the impact of a Mach number. This impact should be taken into consideration, especially for a phugoid mode.

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