Airfoil

About: Airfoil is a research topic. Over the lifetime, 24696 publications have been published within this topic receiving 337709 citations. The topic is also known as: aerofoil & wing section.

Low Reynolds Number Vehicles

Abstract: : Recent interest in a wide variety of low Reynolds number configurations has focused attention on the design and evaluation of efficient airfoil sections at chord Reynolds numbers from about 100,000 to about 1,000, 000. These configurations include remotely piloted vehicles (RPV's) at high altitudes, sailplanes, ultra-light man-carrying/man-powered aircraft, mini-RPVs at low altitudes and wind turbines/propellers. A study is presented of the present status and future possibility of airfoil design and evaluation at subcritical speeds to meet the needs for these applications. Although the design and evaluation techniques for airfoil sections above chord Reynolds numbers of 500,000 is reasonably well developed, serious problems related to boundary layer separations and transition have been encountered below RC = 500,000. Presently available design and analysis methods need to improve their criteria for laminar separation, transition, and turbulent separation. Improved mathematical models of these complex phenomena require additional, very careful experimental studies. Because of the sensitivity of the low Reynolds number airfoil boundary layer to free stream and surface-generated disturbances, definitive experiments are very difficult. Also the physical quantities measured (i.e., pressure difference and drag forces etc.) are very small and the accuracy of such measurements depends on the method used. The results from numerous experimental studies are presented to illustrate the type of difficulties encountered.

Two-Dimensional Wind Tunnel and Computational Investigation of a Microtab Modified Airfoil

Abstract: *† ‡ A computational and wind tunnel investigation into the effectiveness of a microtab-based aerodynamic load control system is presented. The microtab-based load control concept consists of a small tab, with a deployment height on the order of 1% of chord, which emerges approximately perpendicular to a lifting surface in the vicinity of the trailing edge. Lift mitigation is achieved by deploying the tabs on the upper (suction) surface of a lifting surface. Similarly, lift enhancement can be attained by tab deployment on the lower (pressure) surface of a lifting surface. A sensitivity analysis using Reynolds-averaged NavierStokes methods was conducted to determine optimal sizing and positioning of the tabs for active load control at a chord Reynolds number of 1.0 million for the S809 baseline airfoil. These numerical simulations provide insight into the flow phenomena that govern this promising load control system and guided tab placement during the wind tunnel study of the S809 airfoil. The numerical and experimental results are largely in agreement and demonstrate that load control through microtabs is viable. Future efforts will include a study of the unsteady load variations that occur during tab deployment and retraction, and three-dimensional issues involving spanwise tab placement and tab gaps.

LES Prediction of Wall-Pressure Fluctuations and Noise of a Low-Speed Airfoil

Abstract: This paper discusses the prediction of wall-pressure fluctuations and noise of a low-speed flow past a thin cambered airfoil using large-eddy simulation (LES). The results are compared with experimental measurements made in an open-jet anechoic wind-tunnel at Ecole Centrale de Lyon. To account for the effect of the jet on airfoil loading, a Reynolds-averaged Navier-Stokes calculation is first conducted in the full wind-tunnel configuration, and the mean velocities from this calculation are used to define the boundary conditions for the LES in a smaller domain within the potential core of the jet. The LES flow field is characterized by an attached laminar boundary layer on the pressure side of the airfoil and a transitional and turbulent boundary layer on the suction side, in agreement with experimental observations. An analysis of the unsteady surface pressure field shows reasonable agreement with the experiment in terms of frequency spectra and spanwise coherence in the trailing-edge region. In the nose ...

Navier-Stokes Airfoil Computations with e Transition Prediction Including Transitional Flow Regions

Abstract: The e ow around laminar airfoils is computed using a Navier ‐Stokes method coupled to a transition prediction method based on thee N approach. Applying point transition at the predicted transition location produces a strong viscous/inviscid interaction region that prevents the coupled system from converging, whereas the introduction of transitional e ow regions resolves that problem. The emphasis is not placed on the development of new transitional e ow models but primarily on producing convergence, applying modie ed, available models. A comprehensive computational study is performed in a strong adverse and zero pressure gradient airfoil e ow region, as the transitional lengths differ considerably for the different models. A conventional model, which is applicable in e ow regions wheretransition is predicted well upstream of laminar separation, is proposed, together with a special transitional length model fore owswheretheboundary layerstays laminarup to separation. Thee owsovertheDoAL3 and the NLF(1)-0416 laminar airfoils are investigated. The coupled Navier ‐Stokes and e N methods are shown to produce converged results. Furthermore, the values for lift and drag are in excellent agreement with the free transition measurements.

Aerodynamic and Aeroacoustic Optimization of Rotorcraft Airfoils via a Parallel Genetic Algorithm

Abstract: A parallel genetic algorithm (GA) methodology was developed to generate a family of two-dimensional airfoil designs that address rotorcraft aerodynamic and aeroacoustic concerns The GA operated on 20 design variables, whichconstitutedthecontrolpointsforasplinerepresentingtheairfoilsurfaceTheGAtookadvantageofavailable computer resources by operating in either serial mode, where the GA and function evaluations were run on the same processor or “ manager/worker” parallel mode, where the GA runs on the manager processor and function evaluations areconducted independently on separate workerprocessors The multiple objectives of this work were to minimizethedrag and overall noiseof the airfoil Constraintswereplaced on liftcoefe cient, moment coefe cient, andboundary-layerconvergenceTheaerodynamicanalysiscodeXFOILprovidedpressureandsheardistributions in addition to liftand drag predictions Theaeroacousticanalysis code, WOPWOP, provided thicknessand loading noise predictions The airfoils comprising the resulting Pareto-optimal set exhibited favorable performance when compared with typical rotorcraft airfoils under identical design conditions using the same analysis routines The relationship between the quality of results and the analyses used in the optimization is also discussed The new airfoil shapes could provide starting points for further investigation