Effect of Reduced Frequency and Mach Number on Damping Characteristics of SACCON UCAV

2022 ◽  
Author(s):  
Farhan Ullah ◽  
Adnan Maqsood ◽  
Dan Xie ◽  
Hongyi Xu
Keyword(s):  
Mach Number ◽  
Damping Characteristics ◽  
Reduced Frequency

Study of the aerodynamics of in-plane motion

2001 ◽  
Vol 215 (2) ◽  
pp. 89-104
Author(s):  
S T Shaw ◽  
N Qin
Keyword(s):  
Mach Number ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Transfer Operator ◽  
Unsteady Aerodynamics ◽  
Equation Model ◽  
Step Change ◽  
Phase Lag ◽  
Reduced Frequency ◽  
Advance Ratio

A computational analysis is performed of the unsteady aerodynamics associated with the blade sections of helicopter rotors in forward flight. The unsteady flow is studied through solutions of the two- dimensional Reynolds averaged Navier-Stokes equations together with a strongly coupled two-equation model of turbulence. Two motions are studied. The first motion is that of an aerofoil subjected to harmonic in-plane oscillations. The influence of advance ratio and reduced frequency is investigated. It is shown that, in the absence of shock waves, the flow is periodic with a reduced frequency equal to that of the forcing motion. However, the flow development lags behind the forcing motion. Furthermore, for constant reduced frequency the phase lag is independent of advance ratio. In addition to harmonic motion, the aerodynamic response to a step change in Mach number is investigated. Using an assumed form of the response of lift coefficient to a step change in Mach number, a lift transfer operator for step changes in Mach number is obtained in the Laplace domain. An analytical expression for the response to harmonic Mach number oscillations is then obtained from the transfer operator. The resulting formulation for the aerodynamic response confirms that the lag between the forcing motion and the aerodynamic response is independent of advance ratio.

Numerical Simulation of Unsteady Aerodynamic Loads over an Aerofoil in Transonic Flow

2013 ◽  
Vol 644 ◽  
pp. 275-278 ◽  
Author(s):  
Yu Qian ◽  
Jun Li Yang ◽  
Xiao Jun Xiang ◽  
Ming Qiang Chen
Keyword(s):  
Mach Number ◽  
Euler Equations ◽  
Unsteady Aerodynamics ◽  
Angle Of Incidence ◽  
Periodic Motions ◽  
Aerodynamic Loads ◽  
Unsteady Aerodynamic ◽  
Reduced Frequency ◽  
Sinusoidal Motion ◽  
Naca 0012

The unsteady aerodynamic loads are the basic of the aeroelasitc. This paper focuses on the computation of the unsteady aerodynamic loads for forced periodic motions under high subsonic Mach numbers. The flow is modeled using the Euler equations and an unsteady time-domain solver is used for the computation of aerodynamic loads for forced periodic motions. The Euler equations are discretized on curvilinear multi-block body conforming girds using a cell-centred finite volume method. The implicit dual-time method proposed by Jameson is used for time-accurate calculations. Rigid body motions were treated by moving the mesh rigidly in response to the applied sinusoidal motion. For NACA 0012 airfoil, a validation of the unsteady aerodynamics loads is first considered. Furthermore, a study for understanding the influence of motion parameters, the Mach number, mean angle of incidence, reduced frequency, amplitude, was also conducted. A reverse of the trend of hysteretic loops can be observed with the increasing of the Mach number. Nonlinear hysteretic loops are turned up when increasing the amplitude and the reduced frequency during the applied pitch sinusoidal motion.

scholarly journals Physics of Vibrating Airfoils at Low Reduced Frequency

2013 ◽  
Author(s):  
Almudena Vega ◽  
Roque Corral
Keyword(s):  
Mach Number ◽  
Acoustic Waves ◽  
Unsteady Aerodynamics ◽  
Low Pressure ◽  
Travelling Wave ◽  
Navier Stokes ◽  
Influence Coefficient ◽  
Reduced Frequency ◽  
Influence Coefficients ◽  
Key Aspects

The unsteady aerodynamics of low pressure turbine vibrating airfoils in flap mode is studied in detail using a frequency domain linearized Navier-Stokes solver. Both the travelling-wave and influence coefficient formulations of the problem are used to highlight key aspects of the physics and understand different trends such as the effect of reduced frequency and Mach number. The study is focused in the low-reduced frequency regime which is of paramount relevance for the design of aeronautical low-pressure turbines and compressors. It is concluded that the effect of the Mach number on the unsteady pressure phase can be neglected in first approximation and that the unsteadiness of the vibrating and adjacent airfoils is driven by vortex shedding mechanisms. Finally a simple model to estimate the work-per-cycle as a function of the reduced frequency and Mach Number is provided. The edge-wise and torsion modes are presented in less detail but it is shown that acoustic waves are essential to explain its behaviour. The non-dimensional work-per-cycle of the edge-wise mode shows a large dependence with the Mach number while in the torsion mode a large number of airfoils is needed to reconstruct the work-per-cycle departing from the influence coefficients.

ABOUT CONSTRUCTION OF FLAT BODIES WITH INCREASED CRITICAL MACH NUMBER

2016 ◽  
Vol 47 (6) ◽  
pp. 563-579
Author(s):  
Sergey Alexandrovich Takovitskii
Keyword(s):  
Mach Number ◽  
Critical Mach Number
Sign in / Sign up

Export Citation Format

Share Document