GENERAL INFORMATION
-------------------

1. Dataset Title: 
	
		Delft Parametric Flutter Margin (PFM) Test Data Archive


2. Authorship: 

	Name and email:  
		Stefan de Boer, s.deboer-2@tudelft.nl, ORCID: 0000-0002-6155-4790 (1)
		Moti Karpel, karpel@technion.ac.il (2)
		Jurij Sodja, j.sodja@tudelft.nl, ORCID: 0000-0001-8347-1438 (1)
	Institution:  
		1) Technische Universiteit Delft (TU Delft) Faculteit Lucht- en Ruimtevaarttechniek
		2) Technion—Israel Institute of Technology



DESCRIPTION
-----------

1. Abstract: 
	
		The dataset corresponds to the supplementary data for the paper titled 'Safe Flutter Determination for Wings Undergoing Large Deflections' (link: https://arc.aiaa.org/eprint/HDIFICQ9BW3BMFT2ZAAM/full/10.2514/6.2023-0379) and the MSc thesis entitled 'Safe Flutter Determination for Wings Undergoing Large Deflections' (link: http://resolver.tudelft.nl/uuid:b0e12214-ca2a-4dde-8499-955d2da08937). 
		
		The dataset contains wind tunnel test data acquired for the validation of a new flutter test version of the Parametric Flutter Margin (PFM) method, specifically applied to wings undergoing large deflections. The PFM method adds a stabilising parameter, such as a stabilising mass, to the model such that the flutter velocity is increased. To demonstrate the method a wind tunnel test campaign was performed at TU Delft using the Delft Pazy Wing which can exhibit large nonlinear deflection. The wing was equipped with a flutter pod consisting of a shaker and stabilising mass that was placed at the mid-span position at the leading edge of the wing. During the test campaign, three test series were performed. The first identified the flutter boundary through direct flutter tests, with the flutter onset and offset velocities being determined by actually hitting flutter that turned into a Limit Cycle Oscillation (LCO). The second and third test series were the PFM measurements, where both Single Input Single Output (SISO) and Multiple Input Multiple Output (MIMO) PFM were applied to obtain the nominal flutter boundaries without actually hitting flutter.  


2. Keywords:

	Flutter--Aerodynamic
	Parametric Flutter Margin
	Wind tunnel testing
	MIMO systems
	Aeroelasticity
	Delft Pazy Wing
	 

3. Date of data collection:

	September 2022


4. Date of dataset publication:

	See 4TU.ResearchData citation metadata


5. Funding: 

	This work is part of the MSc thesis entitled 'Safe Flutter Determination for Wings Undergoing Large Deflections' performed at TU Delft.



ACCESS INFORMATION
------------------

1. License of the dataset:

	The data files (.mat) found in this repository are licensed under the Creative Commons Attribution 4.0 International License (**CC-BY-4.0**). A copy of the license can be found in the **LICENSES/** directory. See also http://creativecommons.org/licenses/by/4.0/

	The MATLAB code scripts (.m files) found in this repository are licensed under an Apache license version 2.0 (**Apache 2.0**). A copy of the license can be found in the **LICENSES/** directory. See also https://www.apache.org/licenses/LICENSE-2.0.txt


2. Dataset DOI: 

	https://doi.org/10.4121/21656672



VERSIONING AND PROVENANCE
-------------------------

1. Last modification date:

	January 2023


2. Was data derived from another source? If yes, which source?

	The data was not derived from any other source



METHODOLOGICAL INFORMATION
--------------------------

1. Description of data collection methods:

	- The dataset corresponds to Frequency Response Functions (FRFs) obtained from exciting a stabilising mass in a micro-shaker system and measuring the respective response.	

	- The data was acquired using a Siemens Simcenter SCADAS Mobile Data Recorder and Simcenter TestLab 2021.2 (see Simcenter SCADAS Mobile and SCADAS Recorder, Siemens - Community support, 2022 https://community.sw.siemens.com/s/article/simcenter-scadas-mobile-and-scadas-recorder [accessed on 9 October 2022]). The recorder captured the full aeroelastic system response and generated the required FRFs for the PFM method from the measured accelerations seen by the moving mass and the stabilising mass.  

	- The shaker was provided with a continuous random signal having a frequency content in the range between 1 and 30 Hz for a duration of 52 s per measurement. At every testing condition, the measurement was repeated three times to obtain an averaged FRF thereby increasing the signal-to-noise ratio.  


2. Methods for processing the data: 

	- Raw FRFs were smoothed using Gaussian Filter.  

	- Smoothed FRFs were used to assemble the PFM transfer matrix (see equation 2.10 and 5.3 in http://resolver.tudelft.nl/uuid:b0e12214-ca2a-4dde-8499-955d2da08937 or equation 10 and 18 in https://arc.aiaa.org/eprint/HDIFICQ9BW3BMFT2ZAAM/full/10.2514/6.2023-0379) from which eigenvalues can be calculated to derive the flutter margin.

        

3. Instrument- or software- specific information (incl. software version) needed to interpret the data:

	- Data analysis code were written in MATLAB R2020b.

	- For analysis of mode shape data the Siemens Simcenter TestLab 2021.2 was used.



FILE OVERVIEW
-------------

Repository Structure:

	- Correction_Factors
	|
	|	Description: contains 2 sub-directories.
	|
	|
	|__ Shaker_Force
	|		|
	|		|	Description: contains .mat files for horizontal and vertical
	|		|                orientation. Two measurements were taken for each
	|		|				 orientation. They are indicated with 1 or 2.
	|		|				 
	|		|				 FRF of forced measured using acceleration 
	|		|				 of moving mass over force measured using
	|		|				 impedance head force cell
	|		|
	|		|
	|		|__ Files following the convention:
	|				Shaker_Force_FRF_<orientation>_<N>.mat
	|					- <orientation>: horizontal or vertical
	|					- <N>: 1 or 2 (two measurements were taken for each
	|					   	   orientation)
	|
	|__ Shaker_Force_LSV
			|
			|	Description: scontains .mat files for horizontal and vertical
			|                orientation. For each orientation two measurements were taken.
			|				 One with the accelerometer cable attached and one without the cable.
			|				 The cable is for the accelerometer placed on top of the permanent magnet.
			|				 Indcated by cable or no_cable.
			|				 
			|				 FRF of forced measured using acceleration 
			|				 of moving mass over force measured using
			|				 impedance head force cell
			|
			|__ Files following the convention:
			|		FRF_cable_<orientation>.mat
			|			- <orientation>: horizontal or vertical
			|
			|__ Files following the convention:
					FRF_no_cable_<orientation>.mat
						- <orientation>: horizontal or vertical

	- Data_Analysis
	|
	|	Description:
	|	Folder containing MATLAB code scripts. The filepaths used within the 
	|	MATLAB code scripts are based on the top-level folder structure (i.e., 
	|	one folder above the *Data_Analysis* folder).
	|
	|__ Calculate_Correction_Factors.m : calculates shaker force correction factor, 
	|									 called by Create_Smooth_FRF.m
	|
	|__ Compare_Eigenvectors_Smooth_raw.m : creates eigenvector evolution plots in 
	|									    AIAA size.
	|
	|__ Compare_Eigenvalues_Smooth_raw.m : creates eigenvalue evolution plots in 
	|									   AIAA size for set velocities. Created 
	|									   for lambda_1 and lambda_2, called by
	|									   FRF_Data_Analysis_Middle_LE_shroud.m
	|
	|__ Create_Smooth_FRF.m : applies all required scaling and correction factors 
	|						  and smooths the obtained FRFs using a gaussian filter. 
	|
	|__ FRF_Data_Analysis_Middle_LE_shroud.m : main code that reads smoothed FRFs;
	|										   creates transfer function matrix;  
	|										   performs interpolation to find 
	|										   magnitude at phase cross-over; and
	|										   plots eigenvalue evolution, 
	|										   eigenvector evolution and MIMO 
	|										   PFM results. More information on creation of 
	|										   matrix and corresponding results see paper.
	|
	|__ Plot_Coherence.m : 	plots coherence plots for AoA = 2 degrees at 21 m/s in AIAA size			
	|
	|__ Plot_eigenvector_evolution.m : creates a single plot with all eigenvector 
	|								   evolutions (for <alpha>=0,2,4,6 degrees) at 
	|								   20 m/s and at flutter onset velocities
	|
	|__ Plot_MIMO_and_SISO_results.m : plots MIMO and SISO PFM results in a single plot  
	|
	|__ Plot_Results_SISO_lower_gain.m : applies all required scaling and correction
										 factors to SISO FRFs measured with lower gain.
										 Plots comparison of FRFs with test gain 
										 (Gain 1) and lower gain (Gain 2)

	
	- Figures
	|
	|	Description:
	|	Folder containing file structure required for plotting. For better understanding
	|	of location of stored figures, file path in Data_Analysis files will need to
	|	be respecified.

	- LICENSES
	|
	|	Description:
	|	Folder containing the license text for the .mat files (**CC-BY-4.0**) 
	|   and for the code scripts in .m format (**Apache 2.0**).
	|
	|__	CC-BY-4.0.txt
	|
	|__	Apache-License-v2.0.txt

	- Middle_LE_Shroud_FRF_data
	|
	|	Description:
	|	Folder containing the raw unprocessed FRF measurement data. The raw unporcessed
	|	FRF data is found in the subfolders named according to each AoA 
	|	(*AoA_<alpha>*, with <alpha> = 0,2,4,6 [degrees]).
	|
	|__ AoA_<alpha>: each sub-directory contains the raw unprocessed FRF data corresponding to
	|		|		AoA = <alpha> with <alpha> = 0,2,4,6 [degrees]
	|	    |
	|		|__ files following name convention:
	|		|		AoA_<alpha>_<v1>_<v2>ms_<ax1>_FRF_<ax2>.mat
	|		|   		- <alpha>: AoA in degrees (0,2,4,6)
	|		|			- <v1>_<v2>: velocity range dependent on set <alpha> 
	|		|						(see **Column Names**). Units are m/s.
	|		|			- <v1>:  22 to 24 for AoA=0 degrees
	|		|					 21 and 23 for AoA=2 degrees
	|		|					 18 and 21 for AoA=4 degrees
	|		|			- <v2>:  5 ms for AoA=0 degrees
	|		|					 5 ms for AoA=2 degrees
	|		|					 5 ms for AoA=4 degrees
	|		|			- <ax1>: excitation direction x and z for AoA=0,2,4 degrees  
	|		|			- <ax2>: response direction x, y, z for AoA=0,2,4 degrees  
	|		|
	|		|__ files following name convention:
	|		   		AoA_<alpha>_<v>ms_<ax1>_FRF_<ax2>.mat
	|		    		- <alpha>: AoA in degrees (0,2,4,6)
	|		 			- <v>:  velocity dependent on set <alpha> 
	|							(see **Column Names**). Units are m/s.
	|							20-25 ms for AoA=0 degrees
	|							19-23 ms for AoA=2 degrees
	|							18-23 ms for AoA=4 degrees
	|							16-21 ms for AoA=6 degrees
	|					- <ax1>: excitation direction x and z for AoA=0,2,4,6 degrees  
	|					- <ax2>: response direction x, y, z for AoA=0,2,4,6 degrees  
	|		
	|	**Column Names**
	|		
	|	First column: Frequency.
	|	All other columns: single decimal velocity (<v1>_<v2>) or single velocity
	|	(<v>) with response direction (<ax2>) and excitation directio
	|	(<ax1>). For single velocity, first all responses due to x-excitation 
	|	are given, after which all response due to z-excitation are given.
	|	For example for <alpha>=0 the columns are: ["Freq", "20_x/x", 
	|			"20_y/x", "20_z/x", "20_x/z", "20_y/z", "20_z/z", "21_x/x", 
	|			"21_y/x", "21_z/x", "21_x/z", "21_y/z", "21_z/z", "22_x/x", 
	|			"22_y/x", "22_z/x", "22_x/z", "22_y/z", "22_z/z", "22_5_x/x", 
	|			"22_5_y/x", "22_5_z/x", "22_5_x/z", "22_5_y/z", "22_5_z/z",
	|			"23_x/x", "23_y/x", "23_z/x", "23_x/z", "23_y/z", "23_z/z", 
	|			"23_5_x/x", "23_5_y/x", "23_5_z/x", "23_5_x/z", "23_5_y/z", 
	|			"23_5_z/z", "24_x/x", "24_y/x", "24_z/x", "24_x/z", "24_y/z", 
	|			"24_z/z", "24_5_x/x", "24_5_y/x", "24_5_z/x", "24_5_x/z", 
	|			"24_5_y/z", "24_5_z/z", "25_x/x", "25_y/x", "25_z/x", "25_x/z", 
	|			"25_y/z", "25_z/z"]
	|		
	|__ Coherences
	|	
	|	Description: contains coherences. File names are of the form
	|			     Coherence_AoA_2_21ms_<ax1>_<ax2>.mat for AoA=2 degrees, 
	|			     velocity=21 m/s, <ax1>=x,z and <ax2>=x,z
	|
	|
	|__ Lower_Gain_half
	|
	|	Description: contains all the FRFs corresponding to Gain 2. File names 
	|                are of the form AoA_0_<v>ms_z_FRF_<ax2>.mat here <v> is the
	|                velocity ith <v>=22-24 m/s; and <ax2> is the response
	|                direction x, y, z
	|
	|__ Matlab_Analysis_Files
		
		Description: contains unprocessed .mat files where each file is an array 
					 with the columns corresponding to the FRFs at different 
					 velocities, and the rows correspond to different frequencies 
					 (see **Column Names** for full naming scheme) 
					 The files follow the naming convention: 
					 Middle_LE_shroud_AoA_<alpha>.mat where 
	                 <alpha> = 0,2,4,6 [degrees]

	- Middle_LE_Smooth_FRF
	|
	|	Description:
	|	Folder containing the processed (raw and smoothed) FRFs in .mat format. 
	|	Two types of files can be found for each Angle Of Attack (AoA) in degrees
	|
	|__ Smooth_FRF_AoA_<alpha>.mat, with <alpha> = 0,2,4,6 [degrees]  
	|
	|__ Raw_FRF_AoA_<alpha>.mat, with <alpha> = 0,2,4,6 [degrees] 
		
	