Research

Exploring and modeling acoustic levitation

Click Image for movie

Clément is building an acoustic levitator and is also working on the modeling part of it.

If you want to make your own levitator, which can be a great educational tool, you can look at these resources:

Tutorial with multiple references here: https://www.instructables.com/Acoustic-Levitator/
and a journal by Asier Marzo, Adrian Barnes and Bruce W. Drinkwater entitled “TinyLev: A multi-emitter single-axis acoustic levitator” in Review of Scientific Instruments.
You can see some of Bruce’s other cool stuff here

Superposition of Structure-borne Traveling Waves as a Tool for Wave-Driven Motion

Structure-borne travelling waves (SBTW) have been observed throughout nature in the locomotive behaviour of creatures on land with snakes and snails, and in water in the swimming modes of fish and rays. It has been shown that structure-borne travelling waves can be excited in mechanical structures to drive the motion of particles (sand, salt, etc.) and fluid on actuated surfaces of beams and plates. An effective tool for the generation of SBTW in finite structures utilizes the modal properties of the structure itself by using the superposition of standing waves with a phase offset which forms travelling waves without reflections at the boundaries. This method has been used to generate SBTW suitable for wave-driven motion in beams and plates, but the waves up to now these methods have only been driven along a single axis. This work investigates the use of superimposing SBTW that propagates orthogonally. By adjusting the excitation conditions of the constituent SBTW, the overall wavefront can be redirected to propagate in any prescribed direction. These superimposed STBW could be used to drive the motion of particulates in industrial settings for material transport applications. These SBTW can also be used to propel the active structure in two dimensions while suspended in a fluid.

Investigation and mitigation of flow induced noise in consumer electronics and hearing aid devices

Consumer electronics (CE) and hearing aid (HA) devices are integrating microphones in an increasing number of products and an increasing number of microphones per device. Some of these devices use Electret Condenser Microphones (ECMs). However, most recent CE devices implement MicroElectro Mechanical Systems (MEMS) microphones. Microphones are not only sensitive to pressure changes from acoustic disturbances but also from hydrodynamic flows and eddies (i.e. turbulence interacting with the microphone membrane). This flow-induced microphone noise occurs when these devices face real-world wind conditions. Even though wind artifacts can be managed/mitigated in the signal processing domain, the strategy for best audio quality is to address flow noise first in the physical domain to reduce caustic effects of algorithms. Although HAs and other head-worn devices may be able to shield their microphones, the physics behind the flow-induced noise phenomenon demands a better explanation. This would allow for implementing well-suited solutions.

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Cyber-Physical System integrity and security with electro-mechanical impedance

Safety critical cyber-physical systems depend highly on a complex supply chain. Industries such as the automotive, aerospace and heavy machinery count on these supply chains which span across the globe. A fundamental issue faced by such systems is ensuring the integrity of both the cyber information and the physical parts that move throughout the supply chain. Since the manufacturer and consumer are at times geographically separated, there are various challenges in ensuring that physical parts arriving from the manufacturer to the consumer are unmodified and untampered with in-transit. Any attempt of breach or counterfeiting is a grave concern for sensitive supply chains. For industries such as aerospace and automotive, this poses not only risk of intellectual property theft but also risk of system failure and loss of life due to the accidental use of poor-quality fake parts. It is difficult to guarantee the integrity and identity of physical parts as they move through a distributed supply-chain.

Impedance-Matched Multi-Axis Test (IMMAT) with Continuous Residue Interpolation (CRI) models

The Impedance-Matched Multi-Axis Test (IMMAT) is a method developed to address the problems in conventional vibration test methods. However, in this method, some uncertainties must be addressed. For instance, the number of the shakers and their respective locations during a test need to be optimized to guarantee representative results. This optimization is usually done through a finite element analysis of the structure; however, there is not always a high fidelity finite element model available for the system. This usually happens when the structure has complex boundary conditions which are difficult to model or the material properties are unknown. The same is true for legacy equipment. If this is the case, data-driven models can be developed instead. To do so, the data available from the measurements on a number of locations on the structure are used to create a model. However, conventional data-driven models are limited to measured locations; thus, an infeasible amount of testing is required to expand these models. The recently developed Continuous Residue Interpolation (CRI) method yields a predictive data-driven model of the physical dynamical system, which addresses the limitations of the conventional data-driven methods. It turns out that the technique is powerful in both replicating the available measured data and predicting the non-measured data. It seems that CRI and IMMAT are natural fits for each other, and their combination can lead to an efficient procedure for dynamic testing and the overall general field of vibration testing. This research aims to inspect the use of CRI models instead of finite element models to optimize the IMMAT configuration. This can lead to the feasibility of carrying out an environmental test on complex structures where there are no analytical models available. Therefore, by testing the structure at a select number of points, a continuous model of the system can be developed, which can then be used to carry out a virtual test on a different combination of input and output locations to find the optimal configuration for a test.

Non-reflective Traveling Waves in Finite Structures

A large part of our recent efforts have been in the understanding and generation of anechoic (non-reflective) traveling waves in finite structures. By that we mean waves that propagate in a solid finite media with no reflections at the boundaries. There as several applications to this work that can be transformative such as biomimicry of the the helicotrema in the inner ear, drag reduction or non-contact fluid mixing. For a video of an experiment result of a non reflective traveling wave in a free-free beam see here: Beam traveling wave

Single point traveling waves with an absorber

This amazing feature of the inner ear lead us to study the dynamics of a uniform beam connected to a spring-damper system as a passive absorber, in order to understand some of the observed phenomenological behaviors of the basilar membrane. The location of the spring-damper system divides the beam into two dynamic regions: one which exhibits non-reflecting traveling waves and the other with standing waves. In this work, traveling waves co-existing with standing waves in the two regions of the structure and are studied analytically, numerically, and experimentally. The results of this work are the first steps in leading us to new applications of the linear vibration absorber and a possible explanation of the functionality of the helicotrema in the cochlea.

Slat-Gap Filler for Airframe Noise Reduction

In certain flight regimes, the leading-edge slat significantly contributes to aeroacoustic noise emissions. This can be attributed to a vortex forming in the slat cove, which is largely caused by flow from the pressure side to the suction side of the wing. Preliminary studies have shown a significant reduction in aeroacoustic emissions when the slat gap is blocked, with minor impacts on aerodynamics except at extreme angles of attack. Current work focuses on developing a continuous-scanning acoustic beamforming array for source localization, as well as design and optimization of a model-scale slat-gap filler.

Vibration characterization and its effect on High Energy Laser (HEL) weapons

Who doesn’t love laser guns? We have been dreaming of these in books and movies for decades, and finally, after all this time, they have started to show up in our world. However, while the idea may be simple, the application is not.

This research program seeks to understand and describe the effects of mechanical vibration upon the laser optical train, and subsequently the effect upon the laser power delivery.