Numerical method for predicting unsteady aerodynamic loadings causedby control surface motions in subsonic flow

Unsteady aerodynamic characteristics of an oscillating cascade composed of DCA (Double Circular Arc airfoil) blades were studied both experimentally and numerically. The test cascade was operated in high subsonic flow fields with incidence angles up to 5 degrees. Above 3 degrees of the incidence, a separation bubble was produced at the leading edge. The principal concern of the present study was placed on the influence of the separated region on the vibration instability of the cascade blades. The experiment was conducted in a linear cascade wind tunnel in which seven DCA blades were equipped. The central one could be oscillated in a pitching mode. The influence coefficient method was adopted for the measurement, where the unsteady aerodynamic moments were measured on the central blade and neighboring ones. For the numerical analysis, a quasi 3-D N-S code with k–ε turbulence model was developed. The experimental and numerical results complemented each other to obtain detailed understanding of the unsteady aerodynamic behavior of the cascade. It was found that the separation bubble at the leading edge governed the vibration characteristics of blades through the oscillation of the separation bubble itself on the blade surfaces. From the results of parametric studies, the phase shift of the oscillation of the separation bubble was found to be a key factor for determining the unsteady aerodynamic characteristics of the oscillating blades.

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

Volume 2: Fora ◽

10.1115/fedsm2006-98482 ◽

2006 ◽

Cited By ~ 1

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.

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CFD Validation of Interaction of Fin Trailing Vortex with Downstream Control Surface in High Subsonic Flow

54th AIAA Aerospace Sciences Meeting ◽

10.2514/6.2016-1546 ◽

2016 ◽

Cited By ~ 2

Author(s):

James DeSpirito

Keyword(s):

Subsonic Flow ◽

Control Surface ◽

Cfd Validation ◽

Downstream Control ◽

High Subsonic Flow

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Aerodynamic Characteristics of an Airfoil with Boundary Layer Ingestion in Subsonic Flow

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.670-671.609 ◽

2014 ◽

Vol 670-671 ◽

pp. 609-612 ◽

Cited By ~ 1

Author(s):

Jiang Hao Wu ◽

Xue Mei Li

Keyword(s):

Boundary Layer ◽

Numerical Method ◽

Mass Flow ◽

Small Angle ◽

Subsonic Flow ◽

Angle Of Attack ◽

Aerodynamic Characteristics ◽

Pitching Moment ◽

Flow Ratio ◽

Mass Flow Ratio

The influence of boundary layer ingestion (BLI) on the aerodynamics of airfoil RAE2822 in subsonic is investigated by numerical method. Based on the calculation, it is found that the mass flow ratio (MFR), intake height, cowl length and intake position in the chord can affect on the lift, drag and pitching moment remarkable. Considering a maximum lift-over-drag, intake position in the chord should be rearward as possible with a certain high MFR at a small angle of attack and a considerable intake height. There is a proper MFR which makes drag lowest.

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A Two-Dimensional Aerofoil with a Control Surface Oscillating at Low Frequency in High Subsonic Flow

Aeronautical Quarterly ◽

10.1017/s0001925900006971 ◽

1974 ◽

Vol 25 (3) ◽

pp. 186-198 ◽

Cited By ~ 1

Author(s):

D Nixon

Keyword(s):

Subsonic Flow ◽

Deflection Angle ◽

Low Frequency ◽

Frequency Parameter ◽

Control Surface ◽

Two Dimensional ◽

Subcritical Flow ◽

Surface Stiffness ◽

Aerodynamic Derivatives ◽

Surface Deflection

SummaryThe aerodynamic derivatives for a two-dimensional aerofoil with an oscillating control surface in a high subcritical flow are calculated using the method of Nixon. The aerofoil is assumed to be symmetric and at zero incidence with a zero mean control surface deflection angle. With the exception of the control surface stiffness derivative the magnitudes of the aerodynamic derivatives are greater than the corresponding linear values by between 15–35 per cent; the greatest difference occurs for low values of the frequency parameter. The magnitude of the control surface stiffness derivative is less than the corresponding linear value by the order 10–15 per cent.

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The High Subsonic Flow Around a Two-Dimensional Aerofoil with a Trailing Edge Control Surface

Aeronautical Quarterly ◽

10.1017/s0001925900006685 ◽

1973 ◽

Vol 24 (4) ◽

pp. 273-283 ◽

Cited By ~ 1

Author(s):

D Nixon

Keyword(s):

Linear Theory ◽

Subsonic Flow ◽

Lift Coefficient ◽

Integral Equation Method ◽

Control Surface ◽

Two Dimensional ◽

Front Part ◽

Trailing Edge ◽

Moment Coefficient ◽

Standard Linear

SummaryThe effect of the operation of a 15 per cent trailing edge control surface on the flow around a two-dimensional aerofoil in a high subsonic shock-free condition is investigated using the integral equation method developed by Nixon and Hancock. The effect of retaining the non-linearities in the transonic potential equation is to increase considerably the magnitude of the pressures over the front part of the aerofoil in comparison with the pressure found using a modified linearised theory in which significant second-order terms in the boundary conditions are retained. The magnitude of the lift coefficient and the pitching moment coefficient are increased by 10-15 per cent over the values found using the modified linear theory, and by 20 per cent over the values found using standard linear theory. However, the magnitude of the hinge-moment coefficient is decreased by the order of 20 per cent compared with the modified linear values and by 30 per cent when compared to the standard linear values.

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Wind Tunnel Wall Effects in a Linear Oscillating Cascade

Journal of Turbomachinery ◽

10.1115/1.2929199 ◽

1993 ◽

Vol 115 (1) ◽

pp. 147-156 ◽

Cited By ~ 14

Author(s):

D. H. Buffum ◽

S. Fleeter

Keyword(s):

Wind Tunnel ◽

Phase Angle ◽

Detrimental Effect ◽

Subsonic Flow ◽

Poor Correlation ◽

Tunnel Wall ◽

Unsteady Aerodynamic ◽

Unsteady Surface Pressure ◽

Good For ◽

Interblade Phase Angle

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity—the airfoil-to-airfoil variation in unsteady surface pressure—is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.

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