Control of Buffet Phenomenon on a Transonic Swept Wing

Gansel

Waldmann

et al. 2016

Journal of Aircraft

The development of the unsteady wake of transport aircraft under stall conditions and its impact on the empennage are challenging to predict, and the flow physics is far from being understood. In the European Strategic Wind Tunnels Improved Research Potential project, time-resolved particle image velocimetry measurements on the separated wake of the NASA Common Research Model were performed in the cryogenic European Transonic Windtunnel for flight Reynolds number conditions supplemented by aerodynamic measurements for a great variety of inflow conditions. In the time-resolved particle image velocimetry measurements, both low-speed stall (M ∞ 0.25, Re 11.6∕17 million) and high-speed stall conditions (M ∞ 0.85, Re 19.8∕30 million) were considered and the frequency resolution was as high as 1 kHz, enabling a sufficient characterization of the turbulent wake spectrum. For selected high-and low-speed stall conditions, hybrid Reynolds-averaged Navier-Stokes/large-eddy simulations were performed. In the present paper, the numerical results are discussed and compared to the experiments and first evaluations of the particle image velocimetry data are presented. NomenclatureYoung modulus M ∞ = freestream Mach number q = dynamic pressure Re = Reynolds number based on the reference chord length S = wing reference area Sr = Strouhal number based on the reference chord length and freestream velocity t = time U = velocity U ∞ = freestream velocity x, y, z = Cartesian coordinates y = wall distance normalized by the viscous length scale α = angle of attack Δ = filter width in large-eddy simulations η = spanwise position normalized by the semispan of the wing ω = vorticity

mentioning

confidence: 99%

mentioning

confidence: 99%

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Prediction and Measurement of the Common Research Model Wake at Stall Conditions

Gansel

Waldmann

et al. 2016

Journal of Aircraft

“…This interaction is associated with unsteady surface pressures on the wing with the fluctuations being propagated to the wake. While for 2D airfoils the surface and wake spectra are characterized by particular frequencies, a broadband frequency spectrum can be observed for three-dimensional wings 21 . The 3D buffet phenomenon and its impact on the development of the unsteady wake towards the empennage is currently far from being understood and only very few investigations have been published 14,15,21,29 .…”

Section: Introductionmentioning

confidence: 98%

Going for Experimental and Numerical Unsteady Wake Analyses Combined with Wall Interference Assessment by Using the NASA CRM-model in ETW

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Gansel²,

Godard³

et al. 2013

Detailed experimental and accompanying numerical studies on the development of unsteady wakes past an aircraft under stall conditions are currently prepared by a consortium of research institutions and universities. The experiments will be performed in the ETW cryogenic wind tunnel on the NASA Common Research Model. Besides wake surveys using time-resolved cryo PIV measuring technique, wall interference measurements are planned. The tests scheduled for July 2013 are funded by the European Commission in the 7 th framework program. In this paper results of preparatory CFD studies and wake analyses of the CRM model, the TR-PIV measuring technique and the ETW facility are presented along with the wind tunnel model and the planned test program. Nomenclature CFD = Computational Fluid Dynamics CRM = Comon Research Model b = wing span c = reference chord c l = lift coefficient c p = pressure coefficient DES = Detached Eddy Simulation 2 DPW = Drag Prediction Workshop ESP = Electronically Scanned Pressure ESWI RP = European Strategic Wind Tunnels Improved Research Potential ETW = European Transonic Windtunnel f = frequency HTP = horizontal tail plane k = turbulence kinetic energy L = turbulence length scale L 11 = longitudinal integral length scale LES = Large Eddy Simulation LU-SGS = lower-upper symmetric Gauss-Seidel M ∞ = freestream Mach number NTF = National Transonic Facility (U)RANS = (unsteady) Reynolds-Averaged Navier-Stokes Re = Reynolds number based on the reference chord length RMS = Root Mean Square S = wing reference area St = Strouhal number T t = total temperature TR-PIV = Time-Resolved Particle Image Velocimetry U = velocity U ∞ = freestream velocity x,y,z = Cartesian coordinates y + = wall distance normalized by the viscous length scale α = angle of attack ε = dissipation rate of turbulent kinetic energy η = spanwise position normalized by the wing half span

“…Past research activities were conducted for military aircraft 16 or were not focused on the wake development. 4,14,20 Therefore, the Institute of Aerodynamics and Gas Dynamics (University of Stuttgart) together with ONERA, DLR, TsAGI, VZLU, the Von Karman Institute of Fluid Dynamics and the Institute of Thermodynamics (Academy of Sciences of the Czech Republic) initiated a measurement campaign within the framework of the European project ESW I RP (European Strategic Wind tunnels Improved Research Potential). The main objective is a better understanding of the aerodynamics in high speed and low speed stall conditions and its influence on the wake and the empennage.…”

Section: Introductionmentioning

confidence: 99%

Transonic Tail Buffet Simulations for the Common Research Model

Illi

Fingskes

31st AIAA Applied Aerodynamics Conference

et al. 2013

In advance of the ESWI RP measurement campaign in the European Transonic Wind Tunnel in 2014, numerical simulations for NASA's Common Research Model were performed using the DLR TAU code. The presented investigations are focused on the interaction between the separated flow of the main wing with the horizontal tail plane at high Mach numbers. This phenomenon, called transonic tail buffet, poses a serious risk and therefore limits the flight envelope for commercial aircraft.A mesh for the CRM was built including a high resolved tetrahedral block to reduce dissipative effects in the wake. A validation was conducted which shows excellent agreement to the results of the Drag Prediction Workshops. Based on lift polar simulations the buffet onset regime was defined and an inflow condition beyond this point was selected to perform an unsteady simulation. It is shown that a corner separation leads to a movement of the complex shock system on the upper surface of the main wing. Large vortices are shed which propagate downstream and massively influence the flow around the HTP followed by a high frequency response which is found in all integral coefficients. Nomenclatureangle of the HTP [ • ] M Mach number [−] p pressure fluctuations [N/m 2 ] q ∞ dynamic pressure [N/m 2 ] Re Reynolds number [−] xyz cartesian coordinates [m] α angle of attack [ • ] η dimensionless span coordinate [−] ν t eddy viscosity [m 2 /s] Downloaded by CORNELL UNIVERSITY on July 30, 2015 | http://arc.aiaa.org |