Protostars and Planets VI, Heidelberg, July 15-20, 2013
A new approach to modeling collisions of protoplanetary dust aggregates
Weidling, René (TU Braunschweig - Institut für Geophysik und extraterrestrische Physik)
Kothe, Stefan (TU Braunschweig - Institut für Geophysik und extraterrestrische Physik)
Blum, Jürgen (TU Braunschweig - Institut für Geophysik und extraterrestrische Physik)
While it is commonly agreed that planets form in disks of gas and dust around young stars, the exact mechanism of their formation remains as of yet unknown. From observations we do know that the dust particles have sizes of about one micrometer initially. These have to grow to sizes of at least several kilometers in order for gravity to take over and form the final planets.
Güttler et al. (2010) used a series of laboratory experiments of collisions of dust particles to create a model predicting whether or not a collision of two dust particles of certain size and relative velocity leads to them sticking together and, thus, to growth. Zsom et al. (2010) then used this model for a growth simulation in a protoplanetary disk starting with micrometer-sized particles and ended up with particles at most one centimeter in size.
One possible reason for this is the lack of experimental data in wide areas of the parameter space. The growth model is based on classical collision models of spheres (e.g. Hertzian and JKR theory) where no experiments were available. However, even accounting for the elastic moduli of dust aggregates and their surface structure, these models fail to explain the experiments over a wider parameter range. One possible reason may be that the dust aggregates behave more like granular matter than like porous but solid bodies.
We will present an approach of modeling the elastic, plastic and adhesive forces in a collision of two dust particles. The model is based on an equation of motion where the terms describing the forces acting on the particles are of unknown order at first. We then use the measurement of collision parameters like contact time and coefficient of restitution in experiments to constrain our model and solve for the displacement of the contact area from the point of first contact.
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