Ae PW3 High Angle of Attack Working Group

Ae. PW-3: High Angle of Attack Working Group POC: Pawel. Chwalowski@nasa. gov Background Objectives • • Use current state of the art coupled CFD tools in a predictive manner (coupled: structural dynamics + unsteady aerodynamics) Apply to configuration and test conditions that challenge the range of application of the modeling (i. e. , physics are challenging) due to separated flow and dynamically separating flow Define regions of Mach number, angle of attack and structural dynamic characteristics that require different analysis methods, grid resolution and treatment, temporal resolution, etc. Examine the influence on the unsteady characteristics including flutter of in-tunnel effects, including juncture flow Initial Configuration: NASA Benchmark Supercritical Wing • • • Transonic conditions are particularly challenging for computational tools because strong shocks may introduce separated flow The equations on which many methods are based fail to include separated flow field physics Flutter can be introduced into a system due to flow separation The most critical transonic flutter cases are those in the transonic dip, where the onset condition (dynamic pressure at which flutter occurs) can drop rapidly in terms of Mach number change and angle of attack change The transonic dip points are difficult to calculate and difficult to obtain experimentally Ae. PW-1 and Ae. PW-2 Predictions Ae. PW -1 y 16” x Ae. PW -2 32” Pitch axis, forced oscillations Pitch axis, flutter cases Model planform. Dimensions are in inches. Ae. PW-1: separated flow produced a challenge for analyses, even for steady conditions Ae. PW-2: Very large variation in flutter onset predictions at separated flow conditions

Ae. PW-3: High Angle of Attack Working Group POC: Pawel. Chwalowski@nasa. gov Existing Data Mach 0. 8, Ao. A = 5° condition in R-134 a has been chosen for initial analyses challenge Separated flow assessment, using data from 1992 testing Ae. PW-3 Predictions to date at Mach 0. 8, Ao. A = 5° R-12, Flutter Points, a=0°, 1992 R-12, Mach 0. 8 Flutter Points, 1992 Experimental data, Mach 0. 8, Ao. A ~ 5◦ Current Time-Domain Calculations Current Frequency – Domain Calculations Computational and Experimental Plans • • Perform input uncertainty analyses (geometry, angle of attack, elastic axis location, analysis method parameters) Conduct additional wind tunnel testing: • • Measure the flutter boundaries including the front, bottom, and backsides of the flutter buckets Acquire global detailed subcritical data sets: o o o • • Digital image correlation measurements for static and time-accurate model motion and deformation Unsteady pressure sensitive paint for on-surface quantities Unsteady particle image velocimetry for off-body velocities Acquire repeat data points Quantify (measure) the flow environment 2