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Holistic Optical Metrology for Aero-Elastic Research

Periodic Reporting for period 1 - HOMER (Holistic Optical Metrology for Aero-Elastic Research)

Reporting period: 2018-09-01 to 2020-02-29

The HOMER project tackles experimental upstream research challenges related to shaping aviation towards a safer, greener and smarter future. In order to make significant steps towards reduced fuel consumption and emissions it is necessary to implement novel technologies and breakthrough design changes using flexible light-weight structures and more thrust efficient and smarter propulsion techniques. HOMER supports the experimental validation of such design changes by developing advanced optical metrology techniques for testing in (industrial) wind tunnels and achieving breakthrough research on aerodynamics and aero-elasticity in order to increase the understanding of unsteady flows around air vehicles and wings, the related load distributions and induced dynamical forces around and within the exposed structures. Furthermore HOMER will produce benchmark experimental data sets which are ideally suited for comparison with and validation of advanced coupled CFD-FEM/CSM codes which are recently under fast development for flows coping with the problems of unsteady Fluid Structure Interaction (FSI).
In WP1 the Kick-Off Meeting of the whole consortium took place on September 13-14, 2018 at DLR Göttingen together with the PO and AB, the HOMER Teamsite https://teamsites-extranet.dlr.de/as/homer/SitePages/Home.aspx for restricted access to the consortium members, the PO and the AB members for internal exchange of documents has been created, the WPC (Work Package Committee) and the PCC (Project Coordination Committee) WebEx/Telcon Meetings have been held regularly (almost every 3 months). A full HOMÈR consortium meeting has been organized on July 25th, 2019 in Munich.The HOMER Webpage describing the project aims along the different objectives resp. Work Packages and publishing first results to external visitors at https://www.dlr.de/as/en/homer has been maintained.
In WP2 the assessment and validation of uncertainty quantification and performance measures of experimental measurement methods used in the WPs 3, 4 and 5 are under development. Data assimilation approaches allowing e.g. to determine pressure and loads distributions from particle tracks are developed and assessed by benchmark tests with synthetic and real experiments. A datasets on a fluid-structure interaction configuration has been generated numerically mimicking the experimental conditions of Task 3.1 and serve as benchmark test data including uncertainty quantification. This simulation data is used as ground truth for an international challenge on LPT and DA linked to a Workshop on WP 2 (http://cfdforpiv.dlr.de) and as well for the HOMER partners. Further work is dedicated to approaches aiming at improving the modelling of fluid flows, of structural dynamics, and also of models targeting their coupled dynamics. The final objective of these works is to provide more reliable models, complying with experimental data, to investigate complex fluid and fluid-structure phenomena.
In WP3 the assessment and validation of the HOMER experimental methodology, optical surface deformation measurement and velocimetry-based surface-pressure measurement techniques, have been achieved under experimental conditions. WP3 contains four tasks that address these aspects in different conditions. A turbulent boundary layer interacting with an actuated flexible surface panel has been investigated. Furthermore, small- and large-scale experiments in water- and wind tunnels, using simultaneous volumetric flow and model displacement measurements, on rigid and flexible wing models have been prepared and performed. Additionally, CFD simulations and structural analysis are used to support the design of the final experiments
In WP4 complete hydro- and aeroelasticity problems at low to moderate Reynolds numbers (1000 < Re < 2x10⁵) are under experimental investigation. Simultaneous measurements and subsequent computations of the three components of the Collar triangle are and will be performed, with the objective of fully resolving the unsteady dynamics of moving, flapping and/or deforming wings and surface panels. Of particular interest are the response, self-sustained motions and deformations of immersed bodies depending on their constitutive material and structure.
In WP5 the fluid structure interaction (FSI) of oscillating and deformable airfoil models at cruise flight and off-design Mach numbers are under investigation by using sophisticated optical imaging techniques (2D/3D PIV/PTV, PSP, Schlieren, Deformation). To accomplish this goal, five tasks were defined within this WP. Here, in total three 2D rigid wings of the same geometry (OAT15A), but with different degrees-of freedom for flutter analysis and with a flow control device, and one flexible wing (Jedelsky) are investigated in three independent transonic wind tunnel tests.
The overall development of concepts and methodologies within HOMER will result in an integrated and combined optical metrology approach allowing for the full characterization of the unsteady (non-linearly) interacting “multi-physics” problems related to FSI under experimental conditions. For several experiments within HOMER it will be possible to fully close the Collar triangle of forces based on the time-resolved 3D flow field and model deformation measurements and using calibrated structural FEM models. This is a ground-breaking, fundamental and necessary precondition for addressing realistic aero-elastic problems encountered in innovative light-weight flight vehicle designs during related wind tunnel model testing and corresponding validation and verification steps. The overall approach is not available on the market and unique in terms of its non-intrusive character, combination, scalability and accuracy. At the end of the HOMER project the experimental approaches will be ready for testing in industrial scale wind tunnels and other aerodynamic and- elastic test facilities.
The HOMER project is aiming at establishing methods for experimental proof-of-principle and delivers data for their foundational scientific underpinnings supporting innovative coupling of CFD-CSM codes and related MDO design tool developments specifically with respect to FSI problems and phenomena. The corresponding research activities and development of analysis tools based on advanced optical metrology for fluid flows and surface motions and deformations making leading-edge science and technology research more collaborative between the branches of “structures” and “aerodynamics”. The project realizes experiments that support the validation needs of coupled CFD-CSM tool developments, enhance the physical knowledge about FSI phenomena and range from the assessment of the method (turbulent flow over a deforming surface) to relevant (non-linear) problems in aeronautics (transonic buffeting) and flapping flight mechanics. The developed experimental measurement systems will also become commercially available to interested research and industry inside and outside the aeronautical and transport industry which is secured through the involvement of the company participant LaVision.
The HOMER consortium partners are involved in various current and upcoming research and development projects in cooperation with relevant industrial partners from aviation, aerospace engineering, ground transportation and wind energy. This frame work is ideally suited to promote and disseminate the knowledge gained within the HOMER project.
HOMER Project Flow Chart