Introduction

Dune-Ash is an interactive module which can calculates the results of a volcano eruption in Europe. The program simulates how an ash cloud emitted by a volcano would move in a certain velocity field, which is determined by the user on a graphical interface. For the simulation an advection-diffusion-equation is solved.

Program Use

In 4 easy steps you can set parameters like the volcanoes position, the wind field and the diffusion constant. After that, you get a simulation of the ash cloud in a certain period of time.

1. Step : Choose a volcano position

   First you have to set a volcano position. The volcano can be placed anywhere on the map of Europe by mouse-clicking (touching the screen). The map is only a background image, what means that the volcanoes position in not bound to any geographic features. In the calculation the volcanoes position marks the initial point of the ash cloud.

   
2. Step: Sketch a wind field

   Here, you sketch a wind field which the software calculates afterwards. When drawing the wind field, not only the direction but also the speed that you draw it with are important. The drawing speed is equivalent to the wind velocity. Next, the software will calculate a wind field (vector field) form the data given and show it on the map. This wind flied decides how fast and in which direction the ash cloud will move.

   
3. Step: Choose a diffusion coefficient

   Last, you have have to set the diffusion coefficient. It can be between 1e-4 and 1e-2 and shows how fast the ash will spread (due to random particle movement). The higher the diffusion coefficient is set, the shorter the ash cloud will stay retained with a high concentration.

   
4. Step: Simulation results

   After all parameters are set, the software will calculate the concentration of ash in every point on the map to any relevant time, using the formula displayed. On the map, you can see the movement of the ash cloud calculated.

   

Calculation of the concentration

To calculate the concentration is a partial differential equation needed, which can not be solved exactly. Because of that, computer algorithms are used to calculate an approximation solution. The map (Europe) is separated into smaller parts ( small regions ). Then, the ash concentration of these small parts is calculated. The same separation is also used for the period of time.