Volcanic eruptions, black smokers, industrial explosions, fuel injectors, and bomb and meteorite impacts produce unsteady particle-laden jets, plumes and density currents. Such flows have yet to be fully described theoretically, as there is little fundamental understanding of how to relate unsteady source fluxes to flow evolution. Their complex nature requires the integration of several investigative approaches including laboratory, field and computational techniques. The ASU explosive volcanism research group (led by PI Clarke) aims to advance quantitative physical volcanology by studying unsteady particle-laden flows such as Vulcanian eruptions, base surges, lateral blasts, and shock-generating explosions. The instruments and equipment requested in this proposal will help to address several relevant scientific questions which are integral to understanding explosive eruption dynamics. Several key examples are: A. How do unsteady initial conditions control flow evolution and deposit characteristics? B. How do variations in the distribution of particle concentration and velocity within the flow influence the bulk flow behavior (column height, collapse height, runout distance, inundation area, entrainment)? C. How does entrainment of ambient fluid vary spatially and temporally during flow evolution? Are assumptions of homogenous entrainment appropriate for short duration, impulsive flows? D. What role does compressibility play in the early stages of explosive volcanic eruptions? How do leading shocks form in volcanic flows and what controls their strength and velocity? E. Do existing multiphase numerical models of explosive volcanic eruptions (which predict overall evolution, particle distribution and velocity structure) effectively capture the dynamics of simple laboratory experiments and real volcanic eruptions? In order to accomplish these goals, we will conduct and analyze scaled laboratory experiments to quantify variations in particle concentration distribution, velocity distribution, entrainment, and shock wave strength and velocity. Then, we will systematically compare laboratory data with field observations and eruption model results with the ultimate goal of providing a framework within which eruption dynamics can be predicted and field measurements can be used to constrain pre-eruptive conduit conditions and vent fluxes. Our ongoing experiments and analyses have successfully contributed to new understanding of the dynamics of volcanic flows in several ways (e.g. Clarke et al. in press; Chojnicki et al. 2006). We will continue experimental work to further understand unsteady volcanic flows (as in A-E above), in part by better visualizing and quantifying: 1) overall flow evolution using stereo video imaging; 2) interior flow structure (velocity, particle concentration) and entrainment using Particle Image Velocimetry (PIV) and Planar Laser-Induced Fluorescence (PLIF); and 3) shock wave generation using shock tube experiments and laboratory imaging and measurement techniques. These new measurements will provide additional data for comparison against real eruptions; eruptions of frequently-active volcanoes will be documented by simultaneous visual and infrared techniques (FLIR imagery). This proposal requests funding for a PLIF system (which includes one stand-alone high-speed video camera), a complete shock tube, and a FLIR imaging system. The lab already owns one PIV system which includes one high-speed video camera.
|Effective start/end date||9/1/09 → 8/31/12|
- National Science Foundation (NSF): $175,590.00