Active Flow Control : Plasma Actuators
The interaction of a rotating conical flow with a solid surface generates a centrifugal instability. This occurs in the flow over the wings of certain types of aircraft at high angles of attack. Efforts at our laboratory have detected such structures using near-surface flow diagnostics, and shown that they can be effectively alleviated using passive flow control near the surface. Their alleviation removes the narrowband spectral peak at the nominal location of vertical fins on these aircraft. This project explores the substitution of active flow control techniques that remain conformal to the surface and are only powered during high angle of attack operation. The occurrence of the phenomenon and its 15-dB alleviation with geometric fences are shown on a rounded-edge 42-degree swept, cropped delta wing at 25 degrees angle of attack. The feasibility and power requirements for the plasma actuator are estimated in this paper. The generation of counter-rotating vortices using a double dielectric barrier discharge actuator is demonstrated.
Active Noise Control : Acoustic Liners
The present work explores the feasibility of controlling the acoustic impedance of a resonant type acoustic liner. This will be accomplished by translating one perforate over another of the same porosity creating a totally new perforate that had an intermediate porosity. This type of adjustable perforate created a variable orifice perforate whose orifices were non-circular. This arrangement also forms a stepped geometry in the transverse direction, referred to here as a stepped oval orifice. The key objective of the present study is to quantify the degree of attenuation control that can be achieved by using such a concept on the buried septum in a two-degree-of-freedom acoustic liner. Different orifice shapes with the same area will also be examined to determine if highly non-circular orifices had a significant impact on the impedance.
Instabilities in Microjets
In this project, high speed imaging techniques were used to map instabilities at different pressure ratios for different micronozzles.Testing was done with micronozzles of different diameter of the order of 50-1000 micrometers. Desired pressure ratios were achieved with a driver pressure pump (max: 5bar) upstream of the nozzle and a vacuum pump downstream of the nozzle. Different kinds of instabilities were measured, including some anomalous instabilities that are the topic of current research.
Tomo-PIV for turbulence statistics of flow through a contraction
In this project, I assisted a PhD student studying turbulence statistics in developing an experimental facility for tomographic Particle Image Velocimetry. In general terms, Tomographic PIV allows us to map velocity vectors using a Lagrangian Approach in three dimensions. Unlike PIV and Stereo-PIV, Tomo-PIV requires a reconstruction of 3D particle distribution using DaVis' proprietory reconstruction algorithm(MART) prior to 3D cross-correlation. The usage of MART narrows down the tolerances in calibration of the multiple views making this a very challenging velocimetry technique.Data has been acquired and is pending approval for publication.
Spectator Views of the Technique:
Development of a Turnkey Impedance Tube using the 2 microphone method.
Impedance in acoustics is the measure of the opposition that a system presents to acoustic flow resulting of an acoustic pressure applied to the system. It indicates how much sound pressure is generated by the vibration of molecules of a particular acoustic medium at a given frequency. The knowledge of the impedance of a material is essential for the design and development of acoustic materials. In this special project, a low-cost turnkey square impedance tube was developed for measurement of surface impedance and absorption coefficient using the two microphone method. The tube was designed to satisfy the driving requirements for experiments to be conducted in the coming semesters and was developed using in-house prototyping tools and facilities. Development of the tube involved the design and development of the tube hardware as well as software for data processing. The measurement capabilities of the tube have been qualitatively verified using baseline ‘impedance tube controller’ software used at GTRI-ATAS and using theoretical predictions for rigid wall boundary condition.
DIY: Build your own Pedicab
Senior year of high school, I built my own pedicab. Its electric, made of bamboo and allows you to regenerate electricity while travelling.
Pedal Powered Generator for passengers to use (should have done a market survey before building this...
Walk and Recharge Shoes
This walk and recharge shoes module based on a rack and pinion design allows users to harvest passive human energy while walking. The cost of this module is less than $10 and is capable of charging an iPhone from 10%-90% in 6 hours of continuous use.
Labourdial was an online laborer indexing software designed specifically for connecting day-laborers with clients directly. The system indexes and ranks laborers, sorts according to user demands and demographics and ensures minimum wage. I started Labourdial as a startup project and was successful in gaining good traction in subsections of Delhi. Labourdial was one of my main projects as a finalist of the coveted Thiel Fellowship. Currently, labourdial is inoperational.