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DESIGN AND MANUFACTURE OF A WIND TUNNEL TEST HARDWARE

Final Report Summary - WINDTUNNEL (DESIGN AND MANUFACTURE OF A WIND TUNNEL TEST HARDWARE)

Executive Summary:
For transport type aircraft, gust loads are most critical for the wing’s strength design and structural fatigue. For investigating novel control approaches to gust load alleviation, experimental tests on selected technologies or reference model demonstrator have to be conducted. In the framework of SFWA Work Package 1.2. an experimental roadmap was launched by ONERA and was based on three Wind Tunnel Tests performed in the ONERA’s Meudon Center’s S3Ch transonic WT facility.
The main objective of theses works was to dispose of an experimental research tool in order to generate representative perturbations (gust load) for wind tunnel conditions up to transonic conditions. As a result of a Call For Proposal, the works under consideration were realized through a closed collaboration between ONERA and Aviation Design and there were recurrent interactions between the partners (work progress, reviews and deliveries). At the end of the project, the scientific and technical works have allowed the design, the manufacturing and the qualification of this research experimental set-up. In particular, the skills and the knowledges of Aviation Design have enabled the design and the manufacturing of innovative and optimised architectures using metal and composite technologies.
The experimental research tool is composed of two main items :
- the so called “gust generator” which enables the generation of a bidimensional gust field whose properties are actively remote controlled and whose magnitudes are significant to induce aerodynamic effects
- the bidimensional aeroelastic model which enables through several WTT the acquisition of a large and relevant database for a variety of configuration and study cases (airfoil transonic aerodynamic in presence of gust, airfoil aeroelasticity in presence of gust, control surface efficiency with gust …)

As a result, the experimental research tool composed of the gust generator and the aeroelastic model (shown here below) will be intensively investigated in 2014 during several Wind Tunnel Tests within the final objective to demonstrate the active gust load alleviation.

Project Context and Objectives:
The objective of this project was the development and the manufacturing of a research test set up for the investigation of gust loads in wind tunnel.
For transport type aircraft, gust loads are one of the most critical for strength design and fatigue loading source. This project focus on the specific case of gust loads.
In this context, R&D activities are foreseen and it is required to have wind tunnel tests on selected technologies to validate the models and analysis that will serve to design the novel control approaches.
To reach these objectives, there was a specific need to dispose of a research tool for the experimental investigation of gust load alleviation on a model demonstrator.

This research tool is composed of two main components :
• The gust load generator to be able to generate gust perturbations.
• A 2D model equipped with a movable trailing edge control surface and embedded instrumentation fro wind tunel test.

The experiments were carried out at ONERA’s Meudon Center’s S3Ch research wind tunnel (transonic continuous wind tunnel).

Project Results:
The subject of this project was the development and the manufacturing of a research test set up for the investigation of gust loads in wind tunnel.
This research tool is composed of two main components :
• The gust load generator to be able to generate gust perturbations.
• A 2D model equipped with a movable trailing edge control surface and embedded instrumentation fro wind tunel test. This model is installed on a special designed suspension system to study aeroelastic responses to the gust loads.

The experiments were carried out at ONERA’s Meudon Center’s S3Ch research wind tunnel (transonic continuous wind tunnel).

Gust Generator
The concept of the Gust Generator is to create vertical gusts in a wind tunnel by the synchronous actuation of two 2D wings located one above the other (pitch dynamic motions). The two wings are positioned at the end of the convergent of the Wind Tunnel and are fixed on the walls of the wind tunnel. Each wing is activated by two hydraulic jacks controlled by their servo valves. It allows to realize fast pitch motions with very good accuracy even at high aerodynamic loads. The CAD Model of the Gust Generator has been designed under CATIA V5 software in cooperation between Aviation Design and the ONERA.
To maximize the performances of the system (accuracy, speed and resistance), the wings were manufactured in composite materials (carbon) in the aim to make it as light as possible keeping good material properties. The main objective was to find the best compromise allowing the best dynamic performances (kinematics, low rotational inertia) of motion of the rigid wings (low mechanical deformations and high mechanical strength).

The wing model
The main objective of the wing model is to study the aeroelastic responses of the model (both structural and aerodynamic responses) to gust perturbations produced by the 2 gust generators.
The airfoil is a supercritical airfoils (supplied by the ONERA). It is fitted with a movable trailing edge control surface and a lot of sensors were integrated in the wing.

Works have been performed to design an optimized assemblage of composite and metallic structures
The global architecture of the wing has been realized in collaboration with the ONERA. Finite Element Analysis was done to estimate the static and the dynamic behaviors of the model. One objective was to define the best compromise leading to the assemblage of carbon composite skins and metallic parts : the wing model is composed with a principal steel spar with an "I" section, composite carbon skin and ribs.
The control surface is composed with a principal carbon fiber spar and both metallic and composite ribs. To ensure a correct dynamic motion and to support the aerodynamic loads, four hinges have been design in steel material.
The main complexity of this model was to handle the high density of the sensors (unsteady pressure sensors, static pressure tubes, unsteady clinometric probe, optical sensors, magnetic sensors, accelerometers,…) and to correctly integrate them into the wing without any risk of damage, bad locations or malfunctioning .

Suspension system
Because the main objective of the wing model is to study the aeroelastic responses of the model to gust perturbations, the wing model had to be installed on a special designed suspension system. This system allowes the wing to move in pitch (rotation) and is free to move vertically.
The control surface is activated by two hydraulic jacks controlled by their servo valves. It allows to realize very fast motions with very good accuracy even at high aerodynamic loads.

Wind tunnel tests
This full finished assembly was installed in the S3Ch research wind tunnel (transonic continuous wind tunnel) in January / February 2014 with the 2 gust load generators by the ONERA technicians.
As a result, the experimental research tool composed of the gust generator and the aeroelastic model will be intensively investigated in 2014 during several wind tunnel tests within the final objective to demonstrate the active gust load alleviation.


Potential Impact:
The subject of this Call was the development and the manufacturing of a research test set up for the investigation of gust loads in wind tunnel.
This project is directly involved in Smart Wing Technologies in active gust load control.

For transport type aircraft, gust loads are one of the most critical for strength design and fatigue loading source. This project focus on the specific case of gust loads.
In this context, R&D activities are foreseen and it is required to have wind tunnel tests on selected technologies to validate the models and analysis that will serve to design the novel control approaches. To reach these objectives, there was a specific need to dispose of a research tool for the experimental investigation of gust load alleviation on a model demonstrator.
Gust load control solutions will help to create new innovative wing concepts and reduce structural weight for transport type aircraft.
The impact of the wind tunnel tests will help to develop breakthrough technologies to reduce the environmental impact of air transport. 

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