Peering inside the 'deflagration-to-detonation transition' of explosions

Public release date: 22-Nov-2011
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Contact: Charles Blue
cblue@aip.org
301-209-3091
American Institute of Physics

Explosions of reactive gases and the associated rapid, uncontrolled release of large amounts of energy pose threats of immense destructive power to mining operations, fuel storage facilities, chemical processing plants, and many other industrial applications.

To gain a better understanding of what's going on during these explosions, US Naval Research Laboratory research physicist Alexei Poludnenko, and Elaine Oran, senior scientist for reactive flow physics, teamed up with Sandia National Laboratories' Thomas Gardiner, principal member of technical staff, to study the deflagration-to-detonation (DDT) transition, which can occur in environments ranging from experimental and industrial systems on Earth to astrophysical thermonuclear supernovae explosions.

The team will present their findings at the upcoming American Physical Society's 64th Annual DFD Meeting, on Nov. 20-22, 2011, in Baltimore, Maryland.

"Explosions are most often driven by flames propagating at relatively slow subsonic velocities," explains Poludnenko. "Under certain conditions, however, this 'slow' mode of burning can transition to a completely different regime detonation, a.k.a. the 'deflagration-to-detonation transition.' In this case, burning is driven by very fast, strong shock waves that can travel at more than 5 times the speed of sound. The power and destructive potential of such detonation-driven explosions is vastly greater than flame-driven ones. Understanding the conditions and physical mechanisms that can cause the transition between these two explosive modes is critical for developing proper preventive and protective measures in industrial settings."

Significant research efforts have been devoted to studying the deflagration-to-detonation transition, and progress has been made in understanding its role in confined systems. Importantly, it was discovered that walls and obstacles are instrumental in detonation formation. For example, burning in a closed space naturally leads to an increase in pressure and the formation of shocks that can be further amplified through reflections with walls and obstacles ultimately producing a detonation.

Walls and obstacles were clearly important in these earlier studies. But scientists also wondered if unconfined flames could be inherently susceptible to the development of detonations.

"We've used detailed computer simulations of flames in hydrogen-air and methane-air mixtures in a fully unconfined environment under atmospheric conditions to study whether detonations can indeed form in such systems," Poludnenko says.

Among their findings: A subsonic flame evolving in the presence of sufficiently intense turbulence can spontaneously form a detonation both in reactive gases on Earth as well as in the interior of the white dwarf stars providing a missing link for the current theoretical models of Type la supernovae (which are formed by the violent explosion of a white dwarf star).

This work is supported by the Naval Research Laboratory and the Air Force Office of Scientific Research. The talk, "Deflagration-to-detonation Transition in Unconfined Media," is at 5:19 p.m. on Sunday, Nov. 20, in Room 326.

Abstract: http://absimage.aps.org/image/MWS_DFD11-2011-001628.pdf

###

MORE MEETING INFORMATION

The 64th Annual DFD Meeting is hosted by the Johns Hopkins University, the University of Maryland, the University of Delaware and the George Washington University. Howard University and the U.S. Naval Academy are also participating in the organization of the meeting. It will be held at the Baltimore Convention Center, located in downtown Baltimore, Md. All meeting information, including directions to the Convention Center, is at: http://www.dfd2011.jhu.edu/index.html

USEFUL LINKS

Main Meeting Web Site: http://www.dfd2011.jhu.edu/index.html

Search Abstracts: http://meeting.aps.org/Meeting/DFD11/Content/2194

Directions and Maps: http://www.dfd2011.jhu.edu/venuemaps.html

PRESS REGISTRATION

Credentialed full-time journalists and professional freelance journalists working on assignment for major publications or media outlets are invited to attend the conference free of charge. If you are a reporter and would like to attend, please contact Charles Blue (cblue@aip.org, 301-209-3091).

SUPPORT DESK FOR REPORTERS

A media-support desk will be located in the exhibit area. Press announcements and other news will be available in the Virtual Press Room (see below).

VIRTUAL PRESS ROOM

The APS Division of Fluid Dynamics Virtual Press Room features news releases, graphics, videos, and other information to aid in covering the meeting on site and remotely. See: http://www.aps.org/units/dfd/pressroom/index.cfm

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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.

Public release date: 22-Nov-2011
[ | E-mail | Share ]

Contact: Charles Blue
cblue@aip.org
301-209-3091
American Institute of Physics

Explosions of reactive gases and the associated rapid, uncontrolled release of large amounts of energy pose threats of immense destructive power to mining operations, fuel storage facilities, chemical processing plants, and many other industrial applications.

To gain a better understanding of what's going on during these explosions, US Naval Research Laboratory research physicist Alexei Poludnenko, and Elaine Oran, senior scientist for reactive flow physics, teamed up with Sandia National Laboratories' Thomas Gardiner, principal member of technical staff, to study the deflagration-to-detonation (DDT) transition, which can occur in environments ranging from experimental and industrial systems on Earth to astrophysical thermonuclear supernovae explosions.

The team will present their findings at the upcoming American Physical Society's 64th Annual DFD Meeting, on Nov. 20-22, 2011, in Baltimore, Maryland.

"Explosions are most often driven by flames propagating at relatively slow subsonic velocities," explains Poludnenko. "Under certain conditions, however, this 'slow' mode of burning can transition to a completely different regime detonation, a.k.a. the 'deflagration-to-detonation transition.' In this case, burning is driven by very fast, strong shock waves that can travel at more than 5 times the speed of sound. The power and destructive potential of such detonation-driven explosions is vastly greater than flame-driven ones. Understanding the conditions and physical mechanisms that can cause the transition between these two explosive modes is critical for developing proper preventive and protective measures in industrial settings."

Significant research efforts have been devoted to studying the deflagration-to-detonation transition, and progress has been made in understanding its role in confined systems. Importantly, it was discovered that walls and obstacles are instrumental in detonation formation. For example, burning in a closed space naturally leads to an increase in pressure and the formation of shocks that can be further amplified through reflections with walls and obstacles ultimately producing a detonation.

Walls and obstacles were clearly important in these earlier studies. But scientists also wondered if unconfined flames could be inherently susceptible to the development of detonations.

"We've used detailed computer simulations of flames in hydrogen-air and methane-air mixtures in a fully unconfined environment under atmospheric conditions to study whether detonations can indeed form in such systems," Poludnenko says.

Among their findings: A subsonic flame evolving in the presence of sufficiently intense turbulence can spontaneously form a detonation both in reactive gases on Earth as well as in the interior of the white dwarf stars providing a missing link for the current theoretical models of Type la supernovae (which are formed by the violent explosion of a white dwarf star).

This work is supported by the Naval Research Laboratory and the Air Force Office of Scientific Research. The talk, "Deflagration-to-detonation Transition in Unconfined Media," is at 5:19 p.m. on Sunday, Nov. 20, in Room 326.

Abstract: http://absimage.aps.org/image/MWS_DFD11-2011-001628.pdf

###

MORE MEETING INFORMATION

The 64th Annual DFD Meeting is hosted by the Johns Hopkins University, the University of Maryland, the University of Delaware and the George Washington University. Howard University and the U.S. Naval Academy are also participating in the organization of the meeting. It will be held at the Baltimore Convention Center, located in downtown Baltimore, Md. All meeting information, including directions to the Convention Center, is at: http://www.dfd2011.jhu.edu/index.html

USEFUL LINKS

Main Meeting Web Site: http://www.dfd2011.jhu.edu/index.html

Search Abstracts: http://meeting.aps.org/Meeting/DFD11/Content/2194

Directions and Maps: http://www.dfd2011.jhu.edu/venuemaps.html

PRESS REGISTRATION

Credentialed full-time journalists and professional freelance journalists working on assignment for major publications or media outlets are invited to attend the conference free of charge. If you are a reporter and would like to attend, please contact Charles Blue (cblue@aip.org, 301-209-3091).

SUPPORT DESK FOR REPORTERS

A media-support desk will be located in the exhibit area. Press announcements and other news will be available in the Virtual Press Room (see below).

VIRTUAL PRESS ROOM

The APS Division of Fluid Dynamics Virtual Press Room features news releases, graphics, videos, and other information to aid in covering the meeting on site and remotely. See: http://www.aps.org/units/dfd/pressroom/index.cfm

---

[ | E-mail | Share ]

?

AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.

Source: http://www.eurekalert.org/pub_releases/2011-11/aiop-pit112211.php

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