Dry Wind Tunnel System Aeroelastic Testing
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Solution Overview
Problem
Flutter wind-tunnel tests for aircraft structures are expensive and prone to discrepancies due to scaled-down models, which can lead to uncertainties in aeroelastic instability measurements, and are further complicated by wind-tunnel interference and the difficulty in accurately representing structural nonlinearities and flight control systems.
Innovation Solution
A Dry Wind Tunnel System utilizing a Ground Vibration Test hardware system, real-time unsteady aerodynamic force generation software, and a MIMO force controller to simulate flight conditions without a physical wind tunnel, using a reduced order model that focuses on aerodynamic characteristics and excludes structural characteristics, allowing for accurate aeroelastic and aeroservoelastic instability testing on the actual structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a scaled-down aeroelastic structural model is used in wind-tunnel tests, then the testing cost and complexity are reduced, but discrepancies in structural characteristics are introduced leading to measurement uncertainties
Solution Approach 1:
The patent uses a scaled-down aeroelastic model as a copy of the full-scale structure for wind-tunnel testing. This copying approach allows testing to be performed on a smaller, more manageable model while attempting to preserve the essential aeroelastic characteristics through careful scaling of structural properties and aerodynamic conditions.
Solution Approach 2:
The patent applies parameter changes by scaling structural characteristics (stiffness, mass, damping) and aerodynamic parameters (velocity, pressure, density) to maintain dynamic similarity between the model and full-scale structure. These parameter transformations allow the model to replicate the aeroelastic behavior of the actual structure under different flight conditions.
2Measurement precision
If control surface actuators and structural nonlinearities are included in the scaled-down model, then the model accuracy improves, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent extracts and removes complex elements such as control surface actuators and structural nonlinearities from the scaled-down model. By taking out these difficult-to-represent components, the model becomes easier to manufacture while still capturing the primary aeroelastic characteristics for stability boundary determination.
Solution Approach 2:
The patent applies partial action by including only the essential structural characteristics needed for aeroelastic instability detection, rather than attempting to replicate all features of the full-scale structure. This selective inclusion focuses resources on the most critical parameters while avoiding the manufacturing complexity of complete fidelity.
3Ease of manufacture
If wind-tunnel walls are present during flutter testing, then the test setup is simplified, but the wind-tunnel walls interfere with the test results
Solution Approach 1:
The patent removes the harmful wind-tunnel walls from the testing environment by conducting free-flight tests in unconfined space. This extraction of the interfering boundaries eliminates wall interference effects while maintaining a practical test setup through the use of instrumented flight vehicles that can be tested in atmospheric flight conditions.
4Reliability
If flutter wind-tunnel tests are conducted to search for AE/ASE instabilities, then safety risks are identified before flight tests, but the testing process becomes expensive and time-consuming
Solution Approach 1:
The patent performs preliminary aeroelastic stability determination through analytical methods and simplified testing before conducting full-scale flight tests. By conducting preliminary assessments using scaled models and computational approaches, the patent identifies potential instability boundaries in advance, allowing flight test planning to avoid dangerous flight conditions and reducing the need for extensive iterative testing.
Data Source
AI summary
This invention is a ground flutter testing system without a wind tunnel, called Dry Wind Tunnel (DWT) System. The DWT system consists of a Ground Vibration Test (GVT) hardware system, a multiple input multiple output (MIMO) force controller software, and a real-time unsteady aerodynamic force generation software, that is developed from an aerodynamic reduced order model (ROM). The ground flutter test using the DWT System operates on a real structural model, therefore no scaled-down structural model, which is required by the conventional wind tunnel flutter test, is involved. Furthermore, the impact of the structural nonlinearities on the aeroelastic stability can be included automatically. Moreover, the aeroservoelastic characteristics of the aircraft can be easily measured by simply including the flight control system in-the-loop. In addition, the unsteady aerodynamics generated computationally is interference-free from the wind tunnel walls. Finally, the DWT System can be conveniently and inexpensively carried out as a post GVT test with the same hardware, only with some possible rearrangement of the shakers and the inclusion of additional sensors.