Hello everyone,
Plinian and subplinian style explosive eruptions are aeroacoustic emittors. They radiate infrasounds. The aeroacoustic emission and spectral content is related to the physical parameters of the impulsively starting jet as well.
Aeroacoustic experimental studies suggest that turbulent jets can change their dominant aeroacoustic noise emission in response to a forcing vibration such as ground vibration or excitation by wind or as a result of changing vent geometry. This is also the basis for aeroacoustic noise reduction from the jet engines of jumbo jets.
In turn, these studies suggest that a lock-on effect, a sort of resonance may set in.
When it does entrainment is increased by up to 30% according to experimental studies on aeroacoustic forcing and turbulent jets and this, in the case of particle-laden turbulent jet flows, can influence mass distribution and particle ejection and reduce the mass loading in the turbulent and increasingly dilute jet flow.
Conversely, if aeroacoustic excitation is not at the resonance dominant frequency mode, entrainment may be reduced by up to 30% and in the case of an explosive eruption jet one may anticipate that this may result in a sudden change of style into fountain collapse. Particularly in the case where the mass flow rate is such that the eruption column is in the transitional regime, that between the stable plume and the collapsing fountain regimes.
Because an external excitation (noise intensity) of 1 in a million of the characteristic jet noise intensity may result in lock-on or the opposite, this may lead to the possibility of artificially modulating the entrainment and eruption style of some explosive éruptions.
That is to a partial external control, potentially, on the evolution of some explosive eruptions, given the means to do so (eg. 3 "jumbo jet" or "anchored missiles" arranged in a triangle around the erupting volcano, as aeroacoustic external sources of forcing).
To my knowledge this has not been studied either by doing any field tests, which is understandable or by studying this possibility using analogue particle laden jet systems in the lab with the view of applications to volcanic eruptions.
I am wondering if anyone has carried out integrated time-dependent studies of subplinian style explosive eruption jets (eg. at Sakurajima or Etna ?) with the view of assessing potential correlations between aeroacoustic emissions by the jet itself, time-dependent jet video images, radar/sodar imagery, continous volcanic gas flux monitoring (eg. DOAS), ground tremor characteristics, time-dependent wind intensity and/or obvious changes in vent shape over time ?
Looking forward to any info that may relate to this.
With best wishes and kindest regards,
Gerald
Dear Andriy,
Thank you for this link to this search engine. I shall use it.
I did not know that one.
Has anyone else looked into the potential for explosive eruption "control" ?
Cheers,
Gerald
Hi Gerald,
did you see these papers?
http://onlinelibrary.wiley.com/store/10.1029/2011JB008527/asset/jgrb16973.pdf?v=1&t=ife9z4xw&s=d7a3ed0a57dfff2dac08557e6bf97b1d0f95ecc5
http://www.sciencedirect.com/science/article/pii/S0377027310000971
Hope that helps
Federico
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