Waveform Flush Inlet Mitigates Vortex Shedding
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Solution Overview
Problem
Vortex shedding across air inlets of aircraft engines during low-flow or no-flow states leads to pressure oscillations, causing hardware fatigue and degradation due to the 'Coke Bottle Effect', which existing technologies fail to adequately mitigate.
Innovation Solution
The implementation of flush-mounted fluid inlet devices with an inlet mouth featuring a waveform plan-view profile and an oblique inlet ramp with undulating curvature, which reduces coherent shedding by aligning recessed channels and raised landings with the spatial frequency of the waveform profile, thereby minimizing pressure oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a flow control valve is used to modulate airflow through the inlet during low-flow or no-flow states, then auxiliary air intake can be reduced or stopped, but vortex shedding and pressure oscillations occur across the inlet face
Solution Approach 1:
The inlet face is given a waveform plan-view profile with curved undulations instead of a flat surface. This curvature disrupts the coherent vortex shedding that occurs with conventional flat inlets during low-flow or no-flow states, thereby reducing pressure oscillations while maintaining the ability to modulate air intake
Solution Approach 2:
The waveform profile adds a transverse dimension to the inlet face geometry, creating raised crests and recessed troughs that extend across the inlet. This dimensional modification breaks up the uniform flow pattern that causes vortex shedding, converting coherent oscillations into distributed, less harmful flow patterns
2Productivity
If air flow is restricted or eliminated during low-flow or no-flow states, then auxiliary air intake is reduced, but amplified resonant pressure waves form due to the Coke Bottle Effect
Solution Approach 1:
The waveform profile with its curved crests and troughs disrupts the formation of coherent resonant pressure waves by creating distributed flow separation and reattachment patterns across the inlet face, thereby reducing the amplitude of pressure oscillations that would otherwise resonate in the duct cavity
Solution Approach 2:
The waveform profile transforms the harmful coherent vortex shedding and resonant pressure waves into beneficial distributed, low-amplitude flow patterns. The crests and troughs act as flow control features that intentionally create turbulence and flow separation to prevent the formation of large-scale coherent structures that cause damage
3Ease of manufacture
If a conventional flat inlet face is used, then manufacturing is simple, but coherent vortex shedding causes pressure oscillations that peak when frequency aligns with duct cavity natural frequency
Solution Approach 1:
The waveform profile introduces controlled curvature and undulations to the inlet face, which can be manufactured using modern成形 techniques such as hydroforming, stamping, or additive manufacturing. These curvatures are designed to disrupt vortex shedding patterns, reducing pressure oscillations and hardware fatigue while remaining manufacturable
Solution Approach 2:
The waveform profile parameters (amplitude, wavelength, frequency) are optimized to achieve effective vortex shedding disruption. By adjusting these geometric parameters, the inlet can be tuned to prevent resonance with duct cavity natural frequencies across various operating conditions, reducing hardware fatigue without compromising manufacturability
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
The solution effectively mitigates unwanted pressure oscillations, reducing hardware fatigue and degradation during low-flow and no-flow states, while maintaining aerodynamic performance and noise reduction.
Implementation Method 1
a vortex may shed across the face of the air inlet... This coherent shedding may cause pressure oscillations in the inlet duct
Implementation Method 2
amplified resonant pressure waves can form in what is colloquially known as the 'Coke Bottle Effect'. This coherent shedding may cause pressure oscillations in the inlet duct; these pressure oscillations may peak when the frequency of the shedding aligns with the natural frequency of the duct cavity
Data Source
AI summary
Presented are flush-mounted fluid inlets, methods for making/using such fluid inlets, and aircraft equipped with flush-mounted air inlets for engine intake/cooling, bleed air flow, etc. A fluid inlet device is presented for improving vehicle aerodynamic performance. The fluid inlet device includes an inlet base that rigidly mounts to the vehicle, laying substantially flush with a washed outer surface across which fluid flows. The inlet base has a mouth that fluidly couples with a vehicle duct. Two sidewalls are attached to the inlet base, extending between leading and trailing edges of the inlet mouth. An inlet ramp, which is interposed between and attached to the sidewalls, projects inward at an oblique angle from the mouth's leading edge. A highlight is attached to the inlet base, projecting forward from the trailing edge towards the leading edge of the mouth. The highlight has a waveform plan-view profile and undulating outer surface.