Eccentric Rotation Spring Assembly for Wind Tunnel Model Oscillation

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Solution Overview

Problem

Conventional wind tunnel test devices with central axis rotation springs are inadequate for determining dynamic coefficients in applications with eccentric center of gravity, particularly in hypersonic flows, leading to inconsistent measurement results and limited comparability across different wind tunnel models.

Innovation Solution

A spring device with an eccentric axis of rotation is designed, featuring two spring elements subjected to bending stress, connected to a first and second connection device, allowing for dynamic coefficient determination by oscillating movements around an eccentric center of gravity, and compatible with both static and dynamic coefficient measurement systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional rotation spring with a central axis of rotation is used, then the device complexity is reduced and ease of manufacture is improved, but the adaptability for models with eccentric center of gravity deteriorates

Engineering Contradiction:

Improveadaptability for models with eccentric center of gravityVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by positioning the axis of rotation eccentrically relative to the central axis of the spring device. This asymmetric configuration allows the rotation axis to pass through or near the eccentric center of gravity of the model, enabling accurate dynamic coefficient measurements for models with non-central mass distribution, thereby resolving the adaptability limitation of conventional symmetric spring devices.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent introduces a new spatial dimension by decoupling the central axis of the spring device from the axis of rotation. Instead of aligning both axes centrally, the rotation axis is positioned at an eccentric location, creating a dimensional offset that enables the system to accommodate models with eccentric centers of gravity while maintaining structural integrity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If different wind tunnel models are used to determine dynamic coefficients around different axes of rotation, then the measurement flexibility is improved, but the comparability of measurement results deteriorates

Engineering Contradiction:

Improvecomparability of measurement resultsVSAvoidmeasurement flexibility

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent achieves universality by designing a standardized spring device with an eccentric rotation axis that can be applied to various wind tunnel models regardless of their specific geometry or center of gravity location. This universal design allows dynamic coefficients to be determined around different axes of rotation using the same type of spring device, ensuring consistency and comparability of measurement results across different models while maintaining measurement flexibility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If the axis of rotation passes through the central axis, then the manufacturing precision is improved and ease of manufacture is enhanced, but the measurement precision for eccentric center of gravity deteriorates

Engineering Contradiction:

Improvemeasurement precision for dynamic coefficientsVSAvoidmanufacturing precision

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent resolves this contradiction by intentionally introducing asymmetry through the eccentric positioning of the rotation axis. This asymmetric design prioritizes measurement precision for eccentric center of gravity models by allowing the rotation axis to align with the actual center of gravity, accepting that this requires slightly more complex manufacturing compared to perfectly symmetric configurations.

Inventive Principle:

Principle #4Asymmetry

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

Enables consistent and comparable measurement of dynamic coefficients across various applications, including those with eccentric center of gravity, by using the same test fixture with different spring devices, improving measurement accuracy and flexibility.

Implementation Method 1

at least one spring assembly with two spring elements subjected to bending stress

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP4686931A1Spring device for oscillating movements of models and wind tunnel test device with spring device

Publication Date: 2026.02.04 DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT E V

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Figure 3

AI summary

Spring device (1) for oscillating movements of models, preferably wind tunnel models, comprising a first connection device (3) for connecting to a test device (110) and a second connection device (5) for connecting to a model (120), a central axis (11) and at least one spring assembly (13) with two bending-stressed spring elements (15) which are connected at first ends (15a) to the first connection device and at second ends to the second connection device, wherein the first ends (15a) are spaced apart from each other on the first connection device (3) and the second ends (15b) are connected to a rotation axis element (17) of the second connection device (5), wherein the rotation axis element (17) forms a rotation axis (21) for a relative movement between the first and the second connection device (3, 5), wherein the rotation axis (21) is eccentric to the central axis (11).