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

Abstract

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

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

“…The determination of the required temporal and spatial resolution was based on URANS simulations of the CRM performed by Lutz et al [19]. A temporal resolution of 1 kHz was deemed sufficient to obtain relevant information of the wake characteristics in low-speed and high-speed conditions.…”

“…A temporal resolution of 1 kHz was deemed sufficient to obtain relevant information of the wake characteristics in low-speed and high-speed conditions. The chosen spatial resolution of 1 mm is based on the integral length scales of the URANS calculations, which indicate an average length scale of 10 mm in the near-wake region [19].…”

“…Before the test campaign, steady and unsteady Reynolds-averaged Navier-Stokes (URANS) computations were performed to define the requirements for the PIV measuring technique in terms of spatial and temporal resolutions and to identify wake domains of interest [19]. The calculations served further to define the final test matrix that included TR-PIV measurements for both high-speed as well as lowspeed stall conditions.…”

Signal processing and analysis in a buffet onset wind tunnel campaign

“…The adaptor contains a pitching angle mechanism, where the angle is set to a number of predefined values: 0.5 deg increments in the range of [-5, 5] deg and 1 deg increments in the range of [5,8] deg. The half-model is a generic airliner, with a wing aspect ratio of about 8.…”

“…The half-model is a generic airliner, with a wing aspect ratio of about 8. Two wings were provided, one for accelerometer and oil paint visualizations and one with the full array of pressure instrumentation and active buffet control devices (synthetic jets), opposing the shock control bumps used in [8].…”