Variable Spring-Constant Mass Damper for Wind Tunnel Vibration Control
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Solution Overview
Problem
Wind tunnel testing of model aircraft is hindered by undesirable vibrations introduced by the support structure, which existing solutions attempt to mitigate by reducing wind tunnel dynamic pressure, increasing support stiffness, or avoiding unsteady aerodynamic phenomena, all of which have limitations such as increasing scale effects, decreasing test sensitivity, or restricting test conditions.
Innovation Solution
A tunable mass-damping apparatus with a housing, a moving mass, and temperature-dependent springs that can be adjusted to match the natural frequency of the wind tunnel support structure, allowing for real-time tuning without disassembly, using nickel-titanium alloy springs and a temperature control assembly to alter the spring constant.
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 the chance of scale effects increases
Solution Approach 1:
A mass damper is introduced as an intermediary device between the model and the support structure. The mass damper absorbs vibrations at specific frequencies through its oscillating mass and damping elements, thereby reducing artifact forces transmitted to the model without requiring reduction of wind tunnel dynamic pressure, thus avoiding scale effects
Solution Approach 2:
The natural frequency of the mass damper is tuned to match the natural frequency of the support structure by adjusting parameters such as mass, spring constant, and damping coefficient. This frequency matching enables the mass damper to effectively absorb vibrations at the problematic frequencies, reducing artifact forces while maintaining normal operating conditions
2Object-affected harmful factors
If the stiffness of the support structure is increased to decrease vibrations, then the support structure vibrations are reduced, but the balance capacity must be increased which decreases test sensitivity
Solution Approach 1:
The mass damper serves as a vibration isolation intermediary that selectively attenuates vibrations at specific frequencies while allowing other vibrations to pass through. This enables vibration reduction without increasing overall support stiffness, thereby preserving test sensitivity and balance capacity
Solution Approach 2:
Instead of statically increasing support stiffness, the system dynamically responds to vibrations through the oscillating mass of the mass damper. The dynamic system adapts to vibration frequencies, providing vibration reduction only when needed at resonant frequencies while maintaining flexibility and sensitivity for other measurements
3Adaptability or versatility
If existing mass dampers are re-tuned to new frequencies, then the mass damper can absorb vibrations at new frequencies, but the mass damper must be disassembled and reassembled which is costly and time-consuming
Solution Approach 1:
The mass damper incorporates adjustable elements such as variable spring constants or可调 damping mechanisms that allow continuous or discrete adjustment of the natural frequency without disassembly. This dynamic adjustability enables rapid retuning to match changing support structure frequencies during different test conditions
Solution Approach 2:
The design allows modification of key parameters (mass, spring constant, damping coefficient) through adjustable mechanisms rather than fixed components. This enables frequency retuning by changing parameters in place, eliminating the need for disassembly and reassembly, thereby reducing time and cost while maintaining adaptability to different frequency requirements
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 effectively reduces dynamic forces on the wind tunnel model, improving test accuracy by isolating aerodynamic performance vibrations while allowing testing under a broader range of conditions without the need for frequent reconfiguration or increased support size, thus enhancing the reliability and efficiency of wind tunnel tests.
Implementation Method 1
a spring configured to exert a position-dependent force upon the mass; the spring being characterized by a variable spring constant chosen based on a variable natural frequency of a support structure of the wind tunnel model. The variable spring constant may be established with a nickel-titanium alloy spring heated to at least one calibrated temperature that corresponds to a predetermined spring constant
Implementation Method 2
A mass-damping apparatus, or mass damper, can effectively increase the damping of a wind tunnel support system without a need for reducing wind tunnel dynamic pressure, increasing stiffness of the support, or avoiding conditions that would give rise to unsteady aerodynamic phenomena
Implementation Method 3
The natural frequency of the oscillator can be chosen to coincide with a natural frequency of an undesirable artifact vibration of the wind tunnel support, which allows coupling of the motion of the damper mass with that of the wind tunnel support
Data Source
AI summary
A tunable mass-damping apparatus may include a housing having an interior surface, an interior volume containing a fluid, and an axis. The housing may be configured to be coupled to a wind tunnel model. The apparatus may further include a mass configured to move back and forth in the interior volume along the axis. The mass may be configured to make an airtight seal with the interior surface of the housing, thereby dividing the interior volume into an upper chamber and a lower chamber. The apparatus may include a passage fluidly connecting the upper chamber and the lower chamber and a spring configured to exert a position-dependent force upon the mass. The spring may be characterized by a variable spring constant chosen based on a variable natural frequency of a support structure of the wind tunnel model. The variable spring constant may be established with a nickel-titanium alloy spring heated to at least one calibrated temperature that corresponds to a predetermined spring constant.