Collaborative Research: Measurement and Modeling of Air Entrainment and Ash Distribution in Weak Volcanic Plumes

Portland State University, Portland OR

Investigators

Abstract

The 2010 eruption of Eyjafjallajökull volcano in Iceland resulted in weeks of air traffic disruption and more than a billion dollars of economic losses. The disruption was exacerbated by limitations in the accuracy of models used to forecast the size, location, and ash concentration of the cloud. The pre-2010 airline industry policy was to avoid any volcanic ash during flight, and existing models predicted that the plume covered much of Europe. This has provided a new challenge to forecasters, as the rate that ash is fed into the cloud cannot be accurately estimated in complex flow situations. This rate is usually determined from the height of the plume above the volcano, but it can vary significantly due to many factors, including eruptive conditions, atmospheric properties, and local wind speeds. Hence, there is a vital need to develop improved models for realistic conditions. Traditional plume models assume flow in a calm atmosphere, but plumes are significantly modified by perpendicular cross flows with varying scales of turbulence. While cross flow has been considered in some models, the accuracy is still quite crude. This study will develop an improved understanding of volcanic plumes in a stratified cross flow, which will be used to aid in forecasting the dispersal of hazardous ash clouds. Advanced experimental techniques will be used to measure the flow in a laboratory scale plume. These results will be incorporated directly into a state-of-the-art analytical model, which will more accurately quantify the ash density distribution for volcanic scales. In addition, this research will be presented to the broad public audience through small-scale, hands-on laboratory demonstrations at the Oregon Museum of Science and Industry (OMSI).