Effects Of Airfoil Camber Research Articles

Experimental Assessment of the Poststall Performance of Two Highly Cambered Airfoils

Poststall aerodynamic data are required to design and validate propellers, rotors, and wind turbines. However, these data are scarce for (highly) cambered airfoils. This study provides poststall aerodynamic data for the E387 and the FX 63-137 airfoils, and it generates insight into the effect of airfoil camber on poststall aerodynamic behavior. Experimental lift, drag, and moment coefficients are presented for Reynolds numbers between 100,000 and 200,000 at angles of attack from −180 to 180 deg. Prestall performance is validated for the FX 63-137 airfoil, where hysteresis around stall is evident. Comparisons between the two airfoils and published results are made. The FX 63-137 produces a maximum poststall lift coefficient of 1.31 and a drag coefficient at 90 deg of 2.03, whereas the E387 generates values of 1.18 and 1.99, respectively. A geometric relationship is formulated to indicate if an airfoil should have a coefficient of drag larger than a flat plate at 90 deg, and it is found that the FX 63-137 is the only two-dimensional airfoil experimentally tested that conforms to this relationship.

The Effect of Airfoil Camber on Pressure Fluctuation in Bidirectional Axial-Flow Pump

To obtain the influence of airfoil camber on the internal pressure fluctuation of a bidirectional axial-flow pump, the unsteady Reynolds time-averaged Navier–Stokes (URANS) equation was solved to predict the internal flow structure under three airfoil camber cases. The airfoil camber was quantitatively controlled by airfoil camber angle. The pressure standard deviation was used to define the local pressure fluctuation intensity (PFI) inside the impeller and guide vane. Fast Fourier transform was applied to analyze the frequency-domain characteristics of the pressure signal near the impeller–straight pipe interface and impeller–guide vanes interface. The results were validated by the external characteristic test. Under the forward condition, the area of high PFI near the outlet and leading edge of the impeller increased with a decrease in airfoil camber angle, and that near the leading edge of the guide vanes shifted to the middle section with a decrease in airfoil camber angle. The main frequency of the pressure signal near the impeller–guide vanes interface was the blade-passing frequency (BPF), and the main frequency amplitude increased with a decrease in airfoil camber angle. Under the reverse condition, the high PFI area near the inlet and the leading edge of the impeller declined with the decrease in airfoil camber angle. The main frequency of the pressure signal near the impeller–straight pipe interface and impeller–guide vanes interface was the BPF, and the main frequency amplitude decreased with a decrease in airfoil camber angle.

Aerodynamic Analysis of a Gull-inspired Flapping Wing Glider

This paper provided a gull-inspired flapping wing micro aerial vehicle (FMAV) concept followed with aerodynamic analysis. The FMAV supposed to implement both flapping and gliding mode during the flight to enlarge the endurance. A cambered airfoil is employed for wing cross section different with the traditional flat plate. Aerodynamic analysis is proposed through 3D computational fluid dynamics (CFD) method to get the lift characteristic of two different modes. Result shows that the FMAV is able to generate the lift force up to 5 N with an angle of attack 6 degrees and flight speed 6 m/s without flapping, which proves that the FMAV is able to achieve gliding in specific circumstance. Flapping motion is able to produce a higher lift during the flight. Comparison of the lift performance under a specific condition shows that the average lift generated with flapping is 65.3% higher than gliding mode. Research also found that the effect of airfoil camber on lift generation with flapping is not always positive, further analysis is needed when employs a cambered wing in design of FMAVs.

The Effects of Airfoil Camber on Flutter Suppression Regarding Timoshenko Beam Theory

The application of Timoshenko beam theory is presented, thereby the effects of airfoil camber can be investigated analytically and numerically by considering rotary inertia and shear deformation in addition to moment of inertia, aerodynamic loading and bending/torsion coupling. Regarding a tuned blisk, the analysis is simplified to a single blade with plunge and pitch DOF. Pressure distribution of the airfoil surfaces and the resulting aerodynamic forces are calculated with ‘ANSYS/FLOTRAN’ during one-cycle time marching at several reduced frequencies. A parametric relation is then achieved by Roger’s approximation including quasi-inertia, quasi-damping, quasi-elastic and lag terms. The final aeroelastic equations are established by bending-torsion and aerodynamics-structure coupling which is solved by state space approach. This procedure is repeated at several free stream velocities until the real component of an eigenvalue equals zero. The latest velocity is the flutter speed. Following this procedure, flutter characteristics of two similar aeroleastic cases are determined considering only one difference in blade configuration; one with cambered and the other with uncambered airfoil. Comparison of these two cases shows the considerable suppression effect of airfoil camber on flutter.

Nonlinear Aeroelastic Characteristics of a Laminated Composite Wing Considering Compressible Shock Wave Effects

In this study, advanced computational analysis system for nonlinear static aeroelastic problems has been successfully developed by the composite structure (FEM)-fluid (CFD) combined method with internal iteration steps. Major focus of the present study is to investigate the static aeroelastic characteristics of laminated composite wings including the strong normal shock waves in the transonic and low-supersonic flow regions. The results importantly indicate that the effect of airfoil camber on the load distribution of laminated composite wing models can be nonlinear due to the variation of ply orientations.

The unsteady aerodynamics of a first stage stator vane row

The fundamental unsteady aerodynamics on a vane row of an axial flow research compressor stage are experimentally investigated, demonstrating the effects of airfoil camber and steady loading. In particular, the rotor wake generated unsteady surface pressure distributions on the first stage vane row are quantified over a range of operating conditions. These cambered airfoil unsteady data are correlated with predictions from a flat plate cascade inviscid flow model. At the design point, the unsteady pressure difference coefficient data exhibit good correlation with the nonseparated predictions, with the aerodynamic phase lag data exhibiting fair trendwise correlation. The quantitative phase lag differences are associated with the camber of the airfoil. An aft suction surface flow separation region is indicated by the steady state surface static pressure data as the aerodynamic loading is increased. This separation affects the increased incidence angle unsteady pressure data.

The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber

An experimental investigation was conducted to quantitatively determine the validity and applicability of state-of-the-art transverse gust cascade analyses. This was accomplished by obtaining fundamental time-variant forced response data at realistic values of key parameters in a large-scale, low-speed, single-stage research compressor. The forcing function, the velocity defect created by the rotor blade wakes, was measured with a crossed hot-wire probe. The resulting time-variant aerodynamic response was measured by means of flush mounted high response pressure transducers on both flat plate and cambered airfoil stator vane rows over a wide range of incidence angles. These dynamic data were then analyzed to determine the chordwise variation of the unsteady pressure difference in terms of a dimensionless dynamic pressure coefficient and an aerodynamic phase lag referenced to a transverse gust at the leading edge of the vanes. These dimensionless pressure difference data were all correlated with predictions obtained from a state-of-the-art compressible transverse gust, flat plate cascade analysis. Correlation of the classical flat plate unsteady data with the predictions permitted the range of validity of the analysis to be assessed in terms of incidence angle. Correlation of the cambered vane unsteady data with those for the flat plate and with the predictions allowed the effects of airfoil camber as well as the applicability of the flat plate prediction to realistic cambered airfoils to be quantitatively determined.

Closure to “Discussion of ‘The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber’” (1980, ASME J. Eng. Power, 102, p. 342)

Closure to “Discussion of ‘The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber’” (1980, ASME J. Eng. Power, 102, p. 342)

Discussion: “The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber” (Fleeter, S., Bennett, W. A., and Jay, R. L., 1980, ASME J. Eng. Power, 102, pp. 334–342)

Discussion: “The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber” (Fleeter, S., Bennett, W. A., and Jay, R. L., 1980, ASME J. Eng. Power, 102, pp. 334–342)