Department Seminar of Almog Greenberg - Towards Active Hydrodynamic Sensing
SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Wednesday December 20.12.2023 at 14:00
ZOOM SEMINAR
Towards Active Hydrodynamic Sensing
Almog Greenberg
M.Sc. student under the supervision of Prof. Alexander Liberzon
Turbulence Structure Laboratory
School of Mechanical Engineering, Tel Aviv University, Israel
This study explores the feasibility of active hydrodynamic sensing, i.e., the ability to detect and identify the upstream object based on hydrodynamic disturbances using controlled motion inspired by the fish's mechano-sensory organ called the Lateral Line system.
We use sensitive differential pressure sensors (0.1-20 Pa) distributed along a NACA 0012 hydrofoil located in the wake of an upstream cylinder that produces a Karman Vortex Street (KVS). Additionally, we add periodic pitching at the prescribed frequency and angle of attack amplitude to enhance our ability to detect vortices from the surrounding environment. We have developed an experimental system of an open flume, enabling variable Reynolds numbers in different laminar regimes and offering optical access for Particle Image Velocimetry (PIV) measurements in the flow field.
This is a feasibility study supported by the theoretical analysis of Prof. Gregory Zilman and computational fluid dynamics (CFD) in a similar range of Reynolds numbers. Specifically, we focus on the interplay between the hydrofoil and the stable KVS. We discern contributions from the uniform stream and hydrofoil pitching motion by analyzing the hydrofoil's differential pressure signal. CFD simulations help to reduce the number of experiments and explain interplay features such as differential pressure changes with angle of attack, phase shifts between vortices, and hydrofoil pitching amplitude. Results are compared with particle image velocimetry (PIV) flow fields, validating adherence to theory and CFD assumptions. PIV also guides the selection of an optimal cylinder size for generating KVS, considering open flume wall effects within specified parameters.
The results indicate the feasibility of sensing the flow state of a stagnant fluid versus uniform flow at different angles of attack versus the wake of an upstream cylinder, which is a non-trivial hydrodynamic sensing task. Furthermore, we demonstrate that even in noisy signals, we can distinguish between the pressure due to the pitching foil only and the pressure due to the KVS approaching the hydrofoil. We have yet to explore the different pitching amplitudes and frequencies. We are encouraged by the theoretical analysis that shows the direction of future research by controlling the pitching oscillating frequency relative to the periodicity of incoming KVS.
This research opens the way for detecting the surrounding environment using active hydrodynamic sensing based on differential pressure sensors. It has important implications for developing new technologies for environmental monitoring, underwater exploration, and oceanography.
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https://tau-ac-il.zoom.us/j/86497933118
