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AePW-2 Overview
About
The aeroelastic prediction workshop series is intended to provide an open forum, to encourage transparent discussion of results and processes, to promote best practices and collaborations, and to develop analysis guidelines and lessons learned.
The 2nd AIAA Aeroelastic Prediction Workshop (AePW-2) extends the benchmarking effort to aeroelastic flutter solutions. The configuration chosen for the next workshop is the Benchmark Supercritical Wing (BSCW). The primary analysis condition has been chosen such that the influence of separated flow is considered to be minimal, yet a shock is still present. This is a step back in flow complexity from the BSCW cases for AePW-1.
The goal in moving to the lower transonic Mach number is to have analysis teams progress through unforced system analyses, forced oscillation solutions and flutter analyses. Revisiting the AePW-1 analysis condition is included in AePW-2 as an optional case, also extending it to include flutter solutions.
Latest from AePW-2
Telecons 1st Thursday of the month. Next telecon: Feb 9th, 2017
Country
Dial-in #s:
USA:
844-467-4685
Sweden:
0200-883-437
Israel:
1-80-921-2892
Switzerland:
0 800 740 336 OR 0800 345 605
Italy:
800 977 597
Germany:
0 800 320 2291 OR 0800 589 1850
Brazil:
800 020 3462
UK:
0 800 358 8173 OR 0800 279 4867
France:
0 800 949 765 OR 0805 101 207
Canada:
844 467 4685
Turkey:
001 720 259 7012 (NOT toll free)
Japan:
0066 3386 1015
India:
1800 266 0338
Passcode #: (ALL) 5398949869
WebEx Information:
1. Go to webex
2. If requested, enter your name and email address.
3. If a password is required, enter the meeting password: aepw2014!
4. Click "Join".
Deadline for paper submittal to AIAA for Aviation conference: May 15, 2016
Deadline for submitting updated results: Feb 28, 2016
2nd Aeroelastic Prediction Workshop held in association with 2016 SciTech meeting
The second AIAA Aeroelastic Prediction Workshop (AePW-2) was held on Jan 2-3, 2016, in association with the 2016 SciTech conference. The workshop, sponsored by the AIAA Structural Dynamics Technical Committee, had 47 attendees and 15 analysis teams contributing. The major focus of the workshop was flutter onset prediction at two conditions. At one condition, the experimental data exists; at the other condition there is no experimental data making it a blind prediction. For these predictions, CFD-based simulations require time-accurate coupled fluid-structure solutions.
A discussion panel regarding AePW-2 was also held on Tuesday during the SciTech meeting to brief the broader aerospace community and allow continued discussion of technical issues and the path forward regarding computational and experimental aeroelasticity.
While findings of the workshop are still under development, there are some technical findings that can be shared at this preliminary stage. The first issue that was highlighted at the workshop and discussion panel is the critical importance of time-convergence of these unsteady coupled simulations. This is a major change from AePW-1 and is a direct result of lessons learned from the first workshop. Predictions of flutter were highly influenced by the analysis team’s ability to distinguish between numerical damping- introduced by chosen temporal parameters and other computational aspects- and physical damping.
A second issue that was discussed was the process by which flutter predictions are generated. The consensus opinion of workshop analysis teams is that the process generally employed in using the currently available CFD frameworks is unscientific and inefficient. While the process can possibly be used successfully, there must be a better way.
In the workshop follow-up activities, detailed data comparisons will be performed as well as some re-analyses. The issues of primary focus that will be examined in performing the workshop data comparisons are the importance of capturing phase relationships between wing motion and load responses, the suitability of different fidelity simulations to capture separated flow, and the roles of the upper and lower wing surfaces and aft load distribution on the flutter predictions.
Workshop Analysis Commitment Deadline: October 1, 2015
Comparison of Case 1 Results: Steady integrated coefficients (Lift, Drag, Pitching Moment) (and add a link to the page that you made in #4 above)
October Analysts Telecon
Comparison of Case 1 Results: Frequency Response Functions (Pressure coefficients due to forced pitching excitation at 10 Hz)
Experimental Data for BSCW Posted!
Experimental Data to use for this this workshop has been posted here!
Analysts Information for BSCW Posted!
Information for analysts to use for this this workshop has been posted here!
More about BSCW
Planned Workshop Simulations
Workshop simulations will include three types of data, involving three types of computations. Steady data will be generated at a fixed Mach number and angle of attack combination. The steady data will be compared using pressure coefficients and integrated loads. Forced pitching oscillation data will be generated at a set of specified frequencies.
For each of the cases, the dynamic data type is listed in the AePW-2 Test Cases table. For each simulation, comparing the unforced system rigid solution is also desired. There is experimental data to compare to each of these rigid wing solutions. Analysis input parameters are given in the Analysis Parameters table. Please note that the test medium is not air- it is a different heavy gas for each of the two tests due to facility modifications to the Transonic Dynamics Tunnel that occurred in 1996. Differences between the two experiments are listed in the Experiment Differences table.
Configuration and Background Information
The Benchmark Supercritical Wing (BSCW) was chosen as the configuration for the workshop. The model has geometric simplicity, and the test conditions are such that the flow field has demonstrated complexities. The test conditions for the workshop have been chosen to capture increasing complexities. The flow conditions used for AePW-1 were challenging. Shock-induced separated flow dominates the upper surface and the aft portion of the lower surface at the Mach 0.85, 5° angle of attack cases that were simulated. Separation assessment was performed on the experimental data for the OTT test. Using these results as a guide, cases just outside of the separated flow regime will be emphasized for AePW-2. Steady and forced oscillation analyses will be conducted at Mach 0.7, 3° angle of attack; unforced (steady) and flutter analyses will be conducted at Mach 0.74, 0° angle of attack. An optional case, Case 3, will be re-analysis of the AePW-1 case (Mach 0.85, 5° angle of attack), encouraging the application of higher fidelity tools and detailing spatial and temporal convergence issues.
Wind Tunnel Model: The Benchmark SuperCritical Wing (BSCW) was tested in the NASA Langley Transonic Dynamics Tunnel (TDT) in two test entries. The most recent test served as the basis for AePW-1; testing was performed on the oscillating turntable (OTT) which provided forced pitch oscillation data. A prior test was performed on a flexible mount system, denoted the pitch and plunge apparatus (PAPA). Aeroelastic testing was performed for the model on the PAPA, where the mount system provides low-frequency flexible modes that emulate a plunge mode and a pitch mode. The PAPA data consists of steady data and unsteady data at flutter points. Data from both tests will be utilized for comparison with simulation data in AePW-2.
The BSCW airfoil is a NASA SC(2)-0414. The airfoil designation indicates that it was part of the 2nd generation of designed supercritical airfoils, with a design normal force coefficient of 0.4 and a 14% thickness to chord ratio. The planform is rectangular with a wing tip cap shaped as a tip of revolution. The PAPA test was conducted with several flow transition strip configurations; only data using the 35 grit will be used for these comparisons. For the OTT test, the boundary layer transition was fixed at 7.5% chord using size 30 grit. All cases has transition grit on both the upper and lower wing surfaces.
The wing was designed with the goal of being rigid; the spanwise first bending mode of the wing itself has a frequency of 24.1 Hz. The flexible modes that will be modeled in the current effort are provided through the flexible mount system.
The models instrumentation consists of chord-wise rows of in-situ unsteady pressure transducers; for the PAPA test, there were populated rows at the 60% and 95% span stations. For the OTT test, the 95% span station row was not populated with transducers.
Previous Computations and Results Summary The BSCW case served as a semi-blind test case for AePW-1. There were very small plot of some of the data previously published, but in insufficient detail to be truly useful to the analysis teams. Eight teams performed analyses of the BSCW; they used Reynolds-Averaged Navier-Stokes flow solvers exercised assuming that the wing had a rigid structure. Both steady-state and forced oscillation computations were performed by each team, with some teams choosing to perform time-accurate simulations even for the unforced system case. The results of these calculations were compared with each other and with the experimental data. The steady-state results from the computations capture many of the flow features of a classical supercritical airfoil pressure distribution. The most dominant feature of the oscillatory results is the upper surface shock dynamics. Substantial variations were observed among the computational solutions as well as differences relative to the experimental data. Follow-on studies have included hybrid RANS-LES simulations.
