Gallery of Results
In this page, we present a few results from our group's research on high speed flows, flow acoustics, and applications of aeroacoustic devices. References to published literature are also given for the interested reader.
See some interesting videos in our YouTube channel
Sreeram Barathula talks about his work in this video.
Pipe-jet noise suppression using castellations
Anureka's work showed that trailing edge castellations help attenuate pipe-jet noise significantly.
Effect of upstream length on pipe-jet noise
Dr. Kabilan's work demonstrated that by simply increasing the upstream pipe length, the propensity of the pipe-cavity system for unstable oscillations is weakened. Mode shapes inside the pipe-cavity system were also unraveled by FEM analysis.
See published article here: https://doi.org/10.1063/1.5120460 and view the accepted Article. Also view the Scilight of this article
Suppression of impingement jet noise
Dr. Abhijit showed interesting results on the effect of surface roughness on the noise emanating from impinging jets. As can be seen from the following sample results from his article in Physics of Fluids, 2014, impingement noise is suppressed with the use of rough plates.
In a further study on the noise from jets impinging on permeable plates, Abhijit was able to find substantial quietening of impingement noise using permeable plates. These effects are due to fundamental modifications in the flow instabilities brought about by the porosity of the plates. The movies in this link demonstrate this strategy.
Transonic resonance in jets
Dr. Jothi (INSA Visiting Fellow, Summer 2012) investigated transonic resonant tones in orifice and pipe jets. This study showed that under transonic flow conditions, tones significantly different from screech tones are emitted. (IJA).
Thermoacoustic refrigerator
The B.Tech project work of G. Chandrashekhar and G. Puneeth demonstrated thermoacoustic cooling of more than 10 K (seen in thermal image below). Their work was a continuation of B.Tech project of K. Sampath and M. Srikant
Twin-jet interactions
Note the fused shock-cells at small spacing (s/h = 0.5) for Ed-Ed configuration at a pressure ratio of 7.
Supersonic Free Jet Flows
Characteristics of a jet depends on its initial conditions. Notice below, the difference in the shock-structures between jets from an orifice and a pipe observed by Dr. Jothi (See Paper)
In pipe jets, the pipe length greatly influences the spectral quality of noise emitted. This is because the jet evolution depends on its initial conditions including boundary layer thickness at the nozzle/pipe exit (Initial shear layer thickness). Notice that tones gradually vanish as pipe length increases. (Ref). Similar effects using surface roughness is discussed in this paper.
Resonant devices (whistles)
In this paper, we discuss a whistle's journey from a simple toy to a modern industrial device.
A Hartmann whistle is a sound production device in which a high speed jet impinges on a cylindrical cavity closed at one end. The device emits intense tones, and controlled by the cavity length, spacing between the jet and cavity, stagnation pressure of air jet, etc.
Internal Chamfer of Hartmann whistle enhances sound emission at almost all angles as observed by Dr. Narayanan (See Paper)
Thermal Effects in Resonant devices (whistles)
Hartmann whistle also generates intense heat inside the cavity.
See below that the wooden cavity starts burning due to the heating
The sound from a Hartmann whistle can also be used to alter the shape of
liquid droplets and sprays. See pictures & article below from the work of Dr. Narayanan:
Use of Sound for Measurement (eg., Acoustic pyromtery)
Sound can also be used for measurement of temperature of hot zones and flames
(Temperature measurement in a hot-zone). Dr. Narayanan, Dr. Jothi and C.S.L.V. Rohit Sarma
(Temperature measurement in a flame by assuming a temperature profile)