Acoustic Liner Impedance Eduction via 3D CFD and 2D Iterative Simulation
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Solution Overview
Problem
Existing methods struggle to accurately determine the acoustic impedance of complex liners, which is crucial for noise reduction in modern aircraft engines, as standard empirical methods fail to measure impedance effectively for complex geometries.
Innovation Solution
A computer-implemented method is developed to determine acoustic impedance by creating a 3D computer-based model of a liner, performing digital experiments, and iteratively modifying impedance values in a 2D simulation until a matching transfer function is achieved, using computational fluid dynamics and acoustic impedance boundary conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard empirical methods are used to measure acoustic impedance, then the measurement process is simple, but the accuracy fails for complex liner geometries
Solution Approach 1:
The patent creates a virtual copy of the physical liner through computational fluid dynamics (CFD) modeling. The 3D liner geometry is digitized and simulated numerically, allowing acoustic impedance to be calculated from the computational model rather than through physical measurement. This virtual copy enables accurate impedance determination for complex geometries that are difficult to measure empirically.
Solution Approach 2:
The patent replaces the mechanical/physical measurement system with a computational system. Instead of using physical microphones and measurement equipment in an anechoic chamber, the system uses numerical simulations to compute acoustic pressure and velocity fields, thereby determining impedance through calculation rather than physical measurement.
2Productivity
If physical testing is performed to determine acoustic impedance, then direct measurement is obtained, but time and resource consumption increase
Solution Approach 1:
The patent creates a virtual replica of the liner through CAD modeling and CFD simulation. By performing the acoustic impedance measurement on this digital copy rather than the physical liner, the process eliminates the need for time-consuming physical testing while maintaining measurement accuracy. The virtual model can be tested repeatedly without additional time cost.
Solution Approach 2:
The patent performs preliminary digital modeling and simulation to determine acoustic impedance before physical testing would be required. The computational model is prepared in advance, allowing impedance values to be obtained through simulation rather than requiring subsequent physical measurement campaigns, thereby saving time and resources.
3Manufacturing precision
If complex 3D liner geometries are modeled, then accurate representation is achieved, but computational complexity increases
Solution Approach 1:
The patent segments the complex 3D liner geometry into manageable computational elements through meshing. The liner is divided into discrete cells or elements that can be processed numerically, allowing complex geometries to be handled by breaking them down into simpler computational components that the CFD solver can process efficiently.
Solution Approach 2:
The patent creates a digital copy of the complex liner geometry through CAD modeling, where the 3D shape is represented using computational algorithms and mesh data. This digital representation preserves geometric accuracy while enabling numerical analysis through standardized computational methods, separating the complexity of the geometry from the computational processing 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 method allows for the accurate calculation of acoustic impedance for complex liners, reducing the need for physical testing and providing a reliable noise reduction solution for modern aircraft engines.
Implementation Method 1
performing a digital experiment of the liner in an environment using the defined 3D computer-based model of the liner. Results of performing the digital experiment include a reference transfer function
Implementation Method 2
using computational fluid dynamics and acoustic impedance boundary conditions
Implementation Method 3
the liner is represented in the generated 2D model of the environment by an acoustic impedance boundary condition with an impedance value where the impedance value is defined by a resistance value, a reactance value, and a non-linear coefficient value
Data Source
AI summary
Embodiments determine acoustic impedance of liners. An embodiment defines a three-dimensional (3D) computer-based model of a liner and performs a digital experiment of the liner in an environment using the defined model. Results of performing the digital experiment include a reference transfer function. A two-dimensional (2D) model of the environment is generated where the liner is represented by an acoustic impedance boundary condition with an impedance value defined by a resistance value, reactance value, and non-linear coefficient. Iteratively, the impedance value is modified and a 2D simulation is performed using the generated 2D model of the environment with the acoustic impedance boundary condition with the modified impedance value, until a transfer function resulting from performing the 2D simulation matches the reference transfer function. The modified impedance value used in performing the 2D simulation resulting in the transfer function matching the reference transfer function is acoustic impedance of the liner.