Ma, Haoyu
Research CV
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Haoyu Ma [CV]
Applied Math, BS & Physics, BS
University of North Carolina at Chapel Hill
Hi.
The following are descriptions of my research interest, research experience, and research skills.
Research Interests
Robotics,
Computer Vision,
Control and Automation.
Undergrad Research Focus
Fluid Mechanics,
Nonlinear Dynamics,
Faraday Waves,
Solid/Droplet Hydrodynamics.
Research
Experience
Current Project:
Self-propelled Solid Particles on Vibrating Fluidic Interfaces
Ma, Haoyu, Saenz, P. J.
Experiment:
When a particle is placed on a liquid surface with a density less than that of the particle, the particle submerges into the liquid and sinks.
However through this project, we have found an exotic hydrodynamic phenomenon wherein glass beads, instead of sinking, can bounce indefinitely on a vibrated interface between two liquids. Furthermore, when the vibration parameters and bead size are chosen appropriately, beads can demonstrate various bouncing modes, and most interestingly, and "walk" spontaneously on the interface--- self-propelled by resonant interaction with their own wave field.
This walking phenomenon has been previously reported for oil droplets above a vibrating bath (Couder, Y. et al. “Walking and Orbiting Droplets.” Nature), but through my project, I extend the walking phenomenon to general bouncers, either solids or fluids, in such system, which we believe will shine insights into engineering problems involving particle selections and transportations.
(A manuscript is expected to be submitted in spring 2024)
Duration: Jan 2023 - Present
Credit: Haoyu Ma, Pedro Saenz(PI)
This regime is where we observe nonlinear bouncing modes and the Period Doubling Cascade, which is a necessary pathway for a bouncer to become a walker.
This is the most interesting regime where we find the walking phenomenon for a solid particle. The walker generates subharmonic waves and propels itself to continue walking.
This regime is where the wave becomes chaotic due to strong vibrations. The waves in this this regime are called Faraday Waves. Though such waves still make particles move but it is not walking because of its highly randomness.
Bouncing Threshold
Walking Threshold
Faraday Threshold
Vertical Forcing
Simulation and Theory:
Gallery of Interesting Effects:
As walking droplets, our system also exhibits properties resembling a quantum particle, which makes it plausible for conducting hydrodynamic quantum analog. The videos below are recorded at a detuned frequency (Recording: 34.5 Hz, Vibration: 70 Hz).
Two similar-sized walking particles can form an indefinite spinning state, creating a wave field that is equivalent to that of a single particle bouncing.
More interestingly, the spinning orbit of two particles is quantized.
If you perturb such a system( for instance, poke the interface with a needle), you can adjust the radius of their spinning orbit; and the radius only take discrete values based on particle sizes and vibration strength. (Video shows the minimal orbit)
Compared to the coupled spinning state on the left, this video shows a spin state with the same two particles that are out of phase.
Such two types of spinning states share similar features. But, as you may noticed, the anti-spin state has a smaller radius of minimal orbit than that of the synchronized spinners. (Video shows the minimal orbit)
Such a spinning state is also realized with more than two particles.
Four similar-sized walking particles form a stable spinning loop and each diagonal pair of particles is synchronized while close-by pairs are unsynchronized. This is analogous to lattices.
When two walking droplets get close to each other, two droplets merge into a big droplet and fail to be sustained by the surface. This is a problem that happened to many experiments working on collective dynamics of walking droplets in which you study the behavior of multiple walkers in one bath. However, our system---solid walkers--- doesn't have the coalescence problem and can provide collision studies for the walking phenomenon.
The videos below are recorded at a high-speed (Recording: 34.5 Hz, Vibration: 70 Hz).
At lower vibrations (non-walkers), two similar-sized particles can closely pack with each other with no gap. No collisions are observed but only bouncing altogether. Above are two particles with diameters 0.72mm and 0.73mm.
When there are large differences in sizes, collisions are observed due to their geometries, which lead to either one or both to be pushed further from their collision point. Above are two particles with diameters 0.79mm and 0.53mm.
At higher accelerations, particles become more energetic and collisions frequently occur when they form a cluster.
Interestingly, clustering is not stable because regular collisions among particles will drive them apart. After they are driven apart, their wavefields tend to collect them again. Such clustering and dispersing can occur periodically.
Past Projects:
This is an overview of the shaking device, with the experiment chamber and camera setup mounted.
The labivew sends analog signal from DAQ to conditioner, then to amplifer, and reach the shaker to control the acceleration. Two accelerometers are used to give feedback to the PID controller.
Laser cutting and 3D printing.
This is an overview of the shaking device, with the experiment chamber and camera setup mounted.
Above is an air bubble bouncing on an interface formed by two liquids. The picture belows shows the setup of the experiment.
A silicone oil droplet "walks" on the same liquid bath due to constant vibration.
Above is an air bubble bouncing on an interface formed by two liquids. The picture belows shows the setup of the experiment.
More....
Experimental Vibration Table Construction for Hydrodynamic Research
Primary designer and assembler of an experimental shaking device using a Modal Shop Electrodynamic Shaker (MODEL 2110E) interfaced by Labview through NI-DAQ (USB-6343). Compared to the existing design, this shaker has fewer parts and an easier leveling mechanism. Furthermore, it can reach much higher acceleration (~15G 80Hz), which makes it suitable for high-forcing explorations.
Duration: April 2022---August 2022
Research Skills: Solidworks, LabView, NI-DAQ, Arduino, Hands-on Engineering
Credit: Jun Ikeda, Haoyu Ma, Pedro Sáenz (PI)
Vertical Dynamic Studies on Bouncing Air Bubbles below Vibrating Fluidic Interfaces
Independent research inspired by the exotic "walking" state of silicone oil droplets on a vibrated bath of the same liquid.
The project aims to investigate if a similar self-propulsion mechanism could be realized with bubbles below a liquid interface subject to vertical vibration; understanding bubbles' behaviors in this system will find applications in engineering problems involving bubble motion and control. Noticeably, this project led me to discover the "solid walker" mentioned above and gave insights into the Generalized Linear-spring Model which we used to describe such a fluidic vibrational system.
Duration: August 2022---January 2023
Research Skills: MATLAB, Highspeed Videography, 3D Printing,
Basic Manufacturing
Credit: Haoyu Ma, Pedro Sáenz (PI)
A strobed recording of an air bubble bouncing below a vibrated solid ceiling. The flow field around it enables the bubble to "sweep" the dust attached to the ceiling.
This detuned video shows how a 0.50mm bouncer transforms into a walker as vibration slowly accrosses the walking threshold. The particle's bouncing become less stable and swing left and right (imagine you want to throw a rock and you swing it left and right at the beginning to give it more inertia). After it picks up enough inertia, the particle starts to walk in a random direction.