अनुसंधानम्

SDS Laboratory

Ongoing research project(s):

Piezo-actuated biomimetic propulsion for underwater vehicle locomotion (Rs. 42.2 lakhs) [2024 - 2026]

2. Design and prototyping of portable bridges (Rs. 15.25 lakhs) [2025-2027]

Research interests

Use of smart materials/structures for agricultural purposes
Softrobotics
Exoskeleton development

Publications

Google Scholar

FEA/CFD Simulations

FEA - ANSYS, COMSOL, FEMM
CFD - ANSYS Fluent

Novel cMUT design based on flextensional actuator concept to amplify the membrane displacement and achieve higher output pressure

Modal analysis of a stainless steel aeroelastic energy harvesting device where the heave and pitch degrees of freedom are coupled using the custom flexure hinge design.

Demonstration of quad structured mesh generation at the flexure hinge region

Static structural simulation of a hyperelastic rubber bump stopper sandwiched between the shocker mounting cap and the damper seal cover - showing the high strain zones

Analytical simulations

Software - MATLAB.
Electro-mechanical simulations.
Aeroelastic stability analysis.
Modal analysis - obtaining mode shape and natural frequencies.

This simulation shows that axial tension increases the electro-mechanical coupling of a flexible beam with piezo patches laminated at either ends. With increased axial load, the first mode shape of the doubly clamped beam changes such that more strain is introduced at the piezo patches.

This is the plot of piezoelectric power output of an electro-fluid-mechanical system undergoing aeroelastic LCO. Interestingly, an axial tension load could be used to modulate the cut-in wind speed of the device and increase power output through enhanced electro-mechanical coupling.

The sweep of RMS power as a function of resistive load for a piezo electrical transducer at different operating frequencies. The curve peaks are coincident with the assumed optimized resistance values based on loose electromechanical coupling assumption - this validates the assumption.

Flutter convergence plot used to determine the critical wind-speed (~ 4 m/s) at which my aeroelastic flexible structure becomes unstable. The Eigen solution is a complex number the imaginary part is the modal frequency and the real part is the damping.

Typical hourly energy harvesting potential for a wind-solar hybrid device on a windy, cloudy day in September, 2015. Based on wind data provided by RDU weather station.

Experimental vibration analysis

High speed camera - Photron AX 200
Accelerometers - PCB uniaxial/triaxial
Modal Impact Hammer - PCB
Electrodynamic shaker - Electro-Seis APS 113
Laser Doppler Vibrometer - Polytec OFV 5000 + OFV 503
DAQ - NI 4461/4462

Experimental fluid-structure analysis

Wind-tunnel (small)- low turbulence, subsonic 25 cm x 25 cm test section
Wind-tunnel (medium) - subsonic 81 cm x 114 cm test section
Water-tunnel - open channel, 81 cm x 61 cm test section
Instruments - Load cell, torque sensors, optical encoders, CTA probe
Data acquisition - NI DAQ + LabVIEW VI

Data Analysis

Uncertainty analysis.
Signal processing

Phase portraits of LCO in the tensioned ribbon. The top row corresponds to T = 1N, α = 5° and the bottom row corresponds to T = 2 N, α = 5°. The distinct change of the shape of the phase portrait marks operating regimes - static to LCO to chaotic.

RMS value of limit cycle oscillation displacement as a function of wind speed. The shaded region represents 1 std. deviation of uncertainty.

Predominant oscillation frequency of limit cycle oscillation as a function of wind speed. The shaded region represents 1 std. deviation of uncertainty.

Variation in resistive load voltage and LDV velocity signal properties when the system transitions from stable LCO at 8 m/s (left) to chaotic motion at 11 m/s (right).

The coefficient of power is plotted against the turbine yaw angle. The experiment shows that at ~50°, it is possible to achieve a power coefficient that is greater than that when the flow is normal to the rotor disk at 90°. This is promising for using a tethered turbine design for ocean current energy capture.

Design

Compact, modular turbine half-prototype for underwater investigation. The CAD model shows the various instrumentation housed within the polycarbonate body measuring 2 inches. The twist-on nose cone design allows for rapid changing of rotor blade geometry within the water tunnel.

More coming up!