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GUst generators and model DesiGn for transonic wind tunnel tEsTs

Periodic Reporting for period 1 - GUDGET (GUst generators and model DesiGn for transonic wind tunnel tEsTs)

Reporting period: 2019-03-01 to 2020-08-31

GUDGET aims at providing an innovative experimental set-up for the investigation of gust loads, to be installed in the transonic facility ONERA S3Ch.
GUDGET is designing, and will manufacture, calibrate, verify and finally install in the ONERA S3Ch WT an enhanced gust generator system and an aeroelastic half-model connected to the WT side wall, with the purpose to support ONERA in the execution of a WT test campaign and gather information on the aeroelastic behaviour of the model under high amplitude gust conditions.
Regarding the Societal and Environmental Impacts, GUDGET is contributing to a higher aviation’s sustainability by developing methodologies and technologies leading to reduced environmental pollution through reduced weight. Indeed, GUDGET is contributing to provide the industry and the scientific European Community with a novel gust load prediction and simulation system that can cope with demand for increased testing productivity while maintaining the required aerospace quality standards, therefore by improving productivity and reliance on aeroelastic wind tunnel testing, with a clear impact on the enhancement of gust load prediction methods. Thanks to this advancement, the current conservatism in the prediction of gust and turbulence loads, often sizing load cases for main wing and tail surfaces' structures, will be reduced with a direct reduction of structural weight. OEMs data show that thanks to a weight reduction of 1t, potential benefit of 900t CO2 reduction per year can be achieved. This is in line with the CS2 work-programme, the ACARE Vision 2020 and the Flightpath 2050 strategy.
Overall, GUDGET objectives refer to four main categories: design; aerodynamic and aero-structural investigations; Manufacturing, procurement & instrumentation; functional validation and testing. All project objectives are pointing together towards the final and effective implementation of the new enhanced gust generator system and the WT aeroelastic half-model used to validate the reproduced turbulent environment.
Since the beginning of the project, a significant progress has been made in terms of design and analysis activities. A short overview of main results is given in the following.
Gust Generator Design:
- IBK completed all the conceptual studies and trades-off by means of unsteady and viscous CFD analysis, by identifying two different configurations of Gust Generators (GGs) for two different ranges of gust frequency, with an estimated performance suitable to reach high-amplitude gusts in the test section in transonic conditions. 3D CAD model of gust generators are currently very mature concepts, ready to achieve the conceptual review milestone. First modal and stress analysis have been performed, with first indications in terms of materials (metallic and composite) driven by considerations on manufacturability, cost, installation, and operations inside the WT.
- DREAM supported IBK with the optimization of the airfoils to be used in the two GG systems, and with dedicated CFD analysis to assess the performance of the internal channels of the gust generators with fluidic actuators.
- POLIMI and AVDES supported the design reviews with precious advices respectively on dynamic behaviour and manufacturability of the different concepts.
WT model design:
- IBK completed the conceptual studies of WT model, aileron actuation integration, and interface with WT, with the invention of a system to allow implementing rigid or elastic connection of WT model to WT interface and engaging external actuators to actuate the WT model pitch motion. These aspects, as well as the instrumentation suite on the wing, are already drafted and discussed with ONERA.
- POLIMI supported the WT model design with loads evaluation in the WT, for steady attitudes, gust conditions, and imposed (enforced) pitch motion and aileron actuation. POLIMI also performed low- and high-fidelity aeroelastic analysis to assess the clearance for flutter and stability.
- AVDES supported the design reviews with precious advices on instrumentation and manufacturability.
Actuation systems Design:
- CTEC started the design of a new fluidic actuator for GGs complying with the requirements in terms of dimensions and mass flow, completing the concept phase and currently working on a preliminary design, with looks almost complete.
- IBK performed initial studies on the integration of off-the-shelf actuators available at CTEC, for the actuation of the WT model aileron. IBK proposed the first version of double-piezo-stack configuration, then further improved and refined by CTEC. CTEC is currently finalizing the preliminary design of the piezo-actuator.
- After some discussion with ONERA on the actuation system for movable vanes, IBK is currently exploring different solutions involving very specialized actuators and service suppliers to cope with the very challenging requirements (high loads and actuation frequencies).
As mentioned, GUDGET project is targeting to design an experimental setup for the ONERA S3Ch wind tunnel focused on the generation of high amplitude gusts for gust loads measurements on a suitable wall-mounted half-model.
The main technically ambitious parts targeted by GUDGET can be summarized by the following points, each one challenging and representing a step beyond the state-of-the-art in WT systems and models design and manufacturing.
1. Possible employment of fluidic actuators in an unsteady environment, with the necessity to synchronize multiple actuators with alternative blowing with the aim to maximize the GG performance.
2. Design and manufacture of a “small” WT model, highly instrumented, with three different configurations of model-WT interfaces: pitch blocked, pitch constraint with pre-defined flexibility, enforced pitch motion.
3. Design of a high-precision aileron mechanism with the integration and direct application of small and high-performance actuators to make the system able to alleviate and control gust and turbulence loads in the bandwidth [0-100 Hz].
GUDGET is going to produce technical benefits from several points of view, by contributing to develop more comfortable and safer aircraft, lighter and more efficient aero-structures, with potential tangible improvements in terms of fuel consumption and emissions.
It is expected that GUDGET will generate impacts at several levels, namely in the three major areas of European competitiveness within the aeronautical sector, society and Environment, innovation and knowledge integration, for the applicants and their stakeholders.
In terms of European competitiveness, GUDGET is contributing to provide the industry and the scientific European Community with a novel gust load prediction and simulation system, by reducing also the cost of certification by contributing to the development of more efficient and reliable methods for gust loads calculations.