Comparison of the Unsteady Loads of an Airfoil in the Pitching and Plunging Motions

2006 ◽  
Author(s):  
M. Soltani ◽  
M. Seddighi ◽  
F. Rasi
Keyword(s):  
Subsonic Flow ◽  
Free Stream ◽  
Incident Angle ◽  
Oscillation Amplitude ◽  
Stream Velocity ◽  
Frequency Oscillation ◽  
Aerodynamic Loads ◽  
Unsteady Aerodynamic ◽  
Reduced Frequency ◽  
Series Of Experiments

A series of experiments were conducted on an oscillating airfoil in subsonic flow. The model was oscillated in two types of motions, pitch and plunge, at different velocities, and reduced frequencies. In addition, steady data were acquired and examined to furnish a baseline for analysis and comparison. The imposed variables of the experiment were reduced frequency, mean incident angle, amplitude of motion, and free stream velocity as well as the surface grit roughness. The unsteady aerodynamic loads were calculated using surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces of the model. Particular emphases were placed on the effects of different type of motion on the unsteady aerodynamic loads of the airfoil at pre-stall, near stall, and post stall conditions. Variations of the aerodynamic coefficients with equivalent angle of attack for both pitching and plunging motions showed strong sensitivity to the reduced frequency, oscillation amplitude, Reynolds number, and mean angles of attack.

Unsteady Aerodynamic Interactions in a Multistage Compressor

1987 ◽  
Vol 109 (3) ◽  
pp. 420-428 ◽  
Author(s):  
V. R. Capece ◽  
S. Fleeter
Keyword(s):  
Axial Flow ◽  
Unsteady Aerodynamic ◽  
Geometric Conditions ◽  
Forcing Function ◽  
Reduced Frequency ◽  
Aerodynamic Interaction ◽  
Blade Row ◽  
Unsteady Interaction ◽  
Multistage Compressor ◽  
Series Of Experiments

The fundamental flow physics of multistage blade row interactions is experimentally investigated, with unique data obtained which quantify the unsteady harmonic aerodynamic interaction phenomena. In particular, a series of experiments is performed in a three-stage axial flow research compressor over a range of operating and geometric conditions at high reduced frequency values. The multistage unsteady interaction effects of the following on each of the three vane rows are investigated: (1) the steady vane aerodynamic loading, (2) the waveform of the aerodynamic forcing function to each vane row, including both the chordwise and traverse gust components.

scholarly journals An Improved Nonlinear Aerodynamic Derivative Model of Aircraft at High Angles of Attack

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Mi Baigang ◽  
Yu Jingyi
Keyword(s):  
Oscillation Amplitude ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Higher Order ◽  
Initial Angle ◽  
Prediction Ability ◽  
Unsteady Aerodynamic ◽  
Reduced Frequency ◽  
High Angles Of Attack ◽  
Nonlinear Aerodynamic

The classical aerodynamic derivative model is widely used in flight dynamics, but its application is extremely limited in cases with complicated nonlinear flows, especially at high angles of attack. A modified nonlinear aerodynamic derivative model for predicting unsteady aerodynamic forces and moments at a high angle of attack is developed in this study. We first extend the higher-order terms to describe the nonlinear characteristics and then introduce three more influence parameters, the initial angle of attack, the reduced frequency, and the oscillation amplitude, to correct the constant aerodynamic derivative terms that have higher-order polynomials for these values. The improved nonlinear aerodynamic derivative model was validated by using the NACA 0015 airfoil and the F-18 model. The results show that the improved model has a higher prediction ability at high angles of attack and has the ability to predict the aerodynamic characteristics of other unknown states based on known unsteady aerodynamic data, such as the initial angle of attack, reduced frequency, and oscillation amplitude.

scholarly journals Dynamic Stall Analysis of S809 Pitching Airfoil in Unsteady Free Stream Velocity

2015 ◽  
Vol 32 (2) ◽  
pp. 227-235 ◽  
Author(s):  
H. R. Karbasian ◽  
S. A. Moshizi ◽  
M. J. Maghrebi
Keyword(s):  
Free Stream ◽  
Stokes Equations ◽  
Simple Algorithm ◽  
Numerical Results ◽  
Free Stream Velocity ◽  
Dynamic Stall ◽  
Stream Velocity ◽  
Horizontal Axis Wind Turbine ◽  
Dimensional Parameter ◽  
Reduced Frequency

AbstractIn this paper, the dynamic stall of S809 airfoil that widely used in horizontal axis wind turbine, in different reduced frequencies is investigated. The simulation was carried out numerically handling Navier-Stokes equations. For this purpose, the segregated solver with SIMPLE algorithm was chosen to solve the momentum equations. The effect of turbulence on the flow field is taken into account using Shear Stress Transport (SST) K-ω turbulence model. The obtained numerical results are compared with experimental and a few numerical results. The results indicate that the K-ω SST model is in good agreement with experimental results for both steady and unsteady conditions. Furthermore, a non-dimensional parameter, relating the acceleration of unsteady free stream velocity and acceleration of pitch motion (known as reduced frequency), is also investigated. In addition, the results show that any increase in the reduced frequency increases the instantaneous aerodynamic characteristics of oscillating airfoil.

Compressible Unsteady Aerodynamic Loads on Oscillating Airfoils in a Subsonic Flow

2022 ◽  
Author(s):  
Ahmed I. El-Nadi ◽  
Nabil M. Khalifa ◽  
Haitham E. Taha
Keyword(s):  
Subsonic Flow ◽  
Aerodynamic Loads ◽  
Unsteady Aerodynamic

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.

Undulating Plate Type Propeller: The Two-Dimensional Ideal Case

1969 ◽  
Vol 13 (03) ◽  
pp. 171-177
Author(s):  
A. G. Szeless
Keyword(s):  
Free Stream ◽  
Numerical Technique ◽  
Hydrodynamic Pressure ◽  
Power Input ◽  
Stream Velocity ◽  
Two Dimensional ◽  
Propulsive Efficiency ◽  
Incompressible Ideal Fluid ◽  
Reduced Frequency ◽  
Plate Type

The motion of a two-dimensional flexible undulating plate in an incompressible ideal fluid flow is investigated. Employing an iterative numerical technique the motion of the plate and the hydrodynamic pressure distribution are found together with the resulting thrust or drag. The power input is calculated from the work of the exciting force per cycle, and the propulsive efficiency is defined in terms of thrust, free-stream velocity, and power input. For a given plate configuration in the frequency ranges studied, the propulsive efficiency is dependent on the reduced frequency only and reaches 50 percent. Plans for the continuation of this investigation are indicated.

Experimental Investigation of Velocity Profiles in the Wake of an Oscillating Airfoil

2007 ◽  
Author(s):  
M. R. Soltani ◽  
M. Mahmoudi
Keyword(s):  
Experimental Investigation ◽  
Wind Turbine ◽  
Static Pressure ◽  
Oscillation Amplitude ◽  
Great Influence ◽  
Velocity Profiles ◽  
Reduced Frequency ◽  
Vertically Aligned ◽  
Series Of Experiments ◽  
Oscillating Airfoil

A series of experiments were carried out to study the unsteady wakes behind an oscillating airfoil. The airfoil is a section of a wind turbine blade oscillating in pitch about the quarter chord axis at various reduced frequencies, oscillation amplitude and mean angles of attack. Real time velocity profiles were obtained using total and static pressure at 35 vertically aligned points behind the airfoil via two similar rakes. The rakes were located at a distance of 1.5 chord length behind the model. The results show great influence of oscillation amplitude and reduced frequency on the wake velocity profiles.

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