Virtual Riblets via Thermoacoustic Waves for Skin Friction Drag Reduction
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Solution Overview
Problem
Existing methods for reducing skin friction drag on aerodynamic surfaces, such as aircraft, using physical riblets are difficult to manufacture and maintain, and have not achieved sustained commercial applications due to durability and cost issues.
Innovation Solution
The use of pressure waves, specifically thermoacoustic sound pressure waves, is proposed to create virtual riblets on aerodynamic surfaces, reducing skin friction drag by controlling turbulent vortices without the need for physical structures, using nanostructured substrates and piezoelectric materials to generate these waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If physical riblets are manufactured on aircraft surfaces, then skin friction drag is reduced, but manufacturing difficulty and cost increase significantly
Solution Approach 1:
The patent replaces the mechanical/physical riblet structure with an acoustic field system. Pressure wave generating structures emit sound waves that create virtual riblets in the airflow, substituting a mechanical surface modification with a field-based solution that avoids manufacturing complexity while achieving the same drag reduction effect.
Solution Approach 2:
The patent creates a virtual copy of the physical riblet structure using pressure waves. Instead of manufacturing actual riblet geometries, the system generates acoustic pressure patterns that replicate the flow control effects of physical riblets, providing a simplified alternative that eliminates manufacturing challenges.
2Loss of energy
If physical riblets are applied to aerodynamic surfaces, then drag reduction is achieved, but structural durability and maintenance become problematic
Solution Approach 1:
The patent substitutes the vulnerable physical riblet structure with a durable pressure wave generation system. The acoustic field-based approach eliminates the structural weaknesses of physical riblets while maintaining the drag reduction function, improving reliability by removing the vulnerable mechanical component.
Solution Approach 2:
The patent transitions from a static physical riblet structure to a dynamic pressure wave system. The virtual riblets are created through controlled acoustic emissions that can be adjusted and maintained without physical wear, providing a more reliable and adaptable solution compared to fixed physical structures.
3Loss of energy
If physical riblets are manufactured in micron range, then drag reduction effectiveness increases, but manufacturing precision requirements become extremely high
Solution Approach 1:
The patent replaces the need for high-precision physical riblet manufacturing with an acoustic field system. The pressure wave generating structures create virtual riblets with precise control over wavelength and amplitude through acoustic parameters, eliminating the need for micron-level mechanical manufacturing precision while achieving equivalent or superior drag reduction.
Solution Approach 2:
The patent changes the control parameters from physical dimensions (requiring micron-level precision) to acoustic parameters (frequency, amplitude, wavelength). This parameter transformation allows for precise control of the virtual riblet characteristics through acoustic tuning rather than mechanical manufacturing, dramatically reducing precision 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 approach effectively reduces skin friction drag by creating a virtual riblet structure that mimics the drag-reducing effects of physical riblets without the manufacturing and maintenance challenges, providing a durable and adaptable solution for aerodynamic surfaces.
Implementation Method 1
The use of pressure waves, specifically thermoacoustic sound pressure waves, is proposed to create virtual riblets on aerodynamic surfaces
Implementation Method 2
using nanostructured substrates and piezoelectric materials to generate these waves
Implementation Method 3
The pressure wave generating structure may be configured to generate pressure waves, such as sound pressure waves, at the surface
Data Source
AI summary
A method of generating a pressure wave proximate an airflow surface and altering airflow to promote a localized lowering of skin friction over the airflow surface is described herein. A series of pressure waves may be configured to create a virtual riblet to control turbulent vortices in a boundary layer adjacent to the airflow surface creating a virtual riblet. The pressure waves may be configured to prevent disruption of the flow of air relative to at least one of a step or a gap associated with the airflow surface. The pressure wave generating system may be comprised of at least one of a thermoacoustic material, a piezoelectric material and a semiconductor material, and a microelectric circuit.