Tunable Mass Damper for Wind Tunnel Model Vibration Control
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Solution Overview
Problem
Wind tunnel testing in the aeronautics industry faces challenges due to experimental artifacts from support structure forces, which are not present in real-world conditions, and existing solutions like reducing dynamic pressure or increasing stiffness have undesirable effects such as scale effects or avoiding unsteady aerodynamic phenomena, limiting the accuracy and range of testing.
Innovation Solution
A tunable mass-damping apparatus with adjustable damping characteristics, using air or any fluid as a damping medium, which can be coupled to a wind tunnel model to damp vibrations by adjusting the frequency and damping coefficient, allowing for optimal damping without significant disassembly, enabling testing over a broader range of angles and speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the dynamic pressure of the wind tunnel is reduced to decrease artifact forces, then the support structure vibrations are reduced, but scale effects increase
Solution Approach 1:
A mass damper is introduced as an intermediary device between the support structure and the model. The damper includes a mass that oscillates in response to support structure vibrations and dissipates energy through a damping medium (gas or fluid), thereby reducing artifact forces without requiring reduction of dynamic pressure
Solution Approach 2:
The damping characteristics are adjusted by changing parameters of the damping medium, such as gas pressure or fluid viscosity, allowing optimization of damping performance while maintaining high dynamic pressure conditions for accurate scale modeling
2Object-affected harmful factors
If the stiffness of the support structure is increased to decrease vibrations, then the artifact forces are reduced, but the balance capacity must be increased which decreases test sensitivity
Solution Approach 1:
The mass damper serves as a mediator that reduces vibrations without requiring increased support structure stiffness. The damper's mass oscillates in opposition to support structure vibrations, and the damping medium dissipates energy, achieving vibration reduction while maintaining light balance capacity and high test sensitivity
Solution Approach 2:
The solution utilizes mechanical vibration principles by introducing a tuned mass oscillator that resonates at the same frequency as the support structure vibrations. The oscillating mass counteracts the vibrations, and energy dissipation through the damping medium reduces the amplitude without requiring stiffer support structures
3Object-affected harmful factors
If friction or viscous forces are used for damping, then vibration damping is achieved, but the damping coefficient is difficult to adjust without significant disassembly
Solution Approach 1:
The damping coefficient is adjusted by changing physical parameters of the damping medium that are easily controllable. For gas-filled dampers, gas pressure can be adjusted via valves or pressure regulators. For fluid-filled dampers, temperature or fluid viscosity can be modified. These parameter changes allow continuous damping adjustment without disassembly
Solution Approach 2:
The invention employs pneumatic (gas-filled) or hydraulic (fluid-filled) damping media whose damping characteristics can be continuously adjusted by modifying pressure or temperature conditions, providing easy operational control compared to solid friction-based dampers
4Object-affected harmful factors
If oil is used as a damping medium to provide viscous damping, then damping force is generated, but changing the damping coefficient requires changing the kind of oil which is messy and time-consuming
Solution Approach 1:
Gas-filled dampers eliminate the need for handling and changing viscous oils. Gas pressure can be adjusted quickly using valves or pressure regulators, providing continuous damping control without the mess and time consumption associated with oil changes
Solution Approach 2:
Instead of changing the damping medium itself, the damping coefficient is adjusted by changing physical parameters of the same medium (gas pressure or fluid temperature), which can be done rapidly and cleanly compared to replacing oil
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for accurate measurement of aerodynamic performance by reducing dynamic forces on the model, expanding the range of testable conditions, and potentially saving multiple test flights by achieving optimal damping settings quickly and easily.
Implementation Method 1
a mass configured to move back and forth between the pressure chambers in a substantially airtight manner and thereby to alter gas pressure within each pressure chamber
Implementation Method 2
at least one spring configured to exert a position-dependent force upon the mass
Implementation Method 3
a passageway configured to allow the gas to pass between the chambers at a controllable rate
Data Source
Figure 1~4
Figure 3
Figure 5~6
AI summary
A system, including methods and apparatus, of tuning a mass-damping apparatus to reduce dynamics forces on a wind tunnel model during wind tunnel testing. The mass-damping apparatus is coupled to a wind tunnel model and may comprise first and second pressure chambers containing a gas, a mass configured to move back and forth between the pressure chambers in a substantially airtight manner and thereby to alter gas pressure within each pressure chamber, at least one spring configured to exert a position-dependent force upon the mass, and a passageway configured to allow the gas to pass between the chambers.