Context. Laboratory experiments have shown that the initial stage of the dust growth in the protoplanetary disk starts with low-velocity hit-and-stick collisions between sub-micron grains, before the relative impact energy becomes large enough to cause the morphological restructuring of the forming aggregates. The results of these collisions are loose aggregates characterized by fractal dimensions ≤2. Numerical studies generally model this early stage with colliding clusters made of monodisperse spherical monomers.Aims. In this paper we aimed to investigate how a more complex representation of the monodisperse monomers structure influences the morphology of the final aggregate particles in terms of fractal dimension, porosity, cross-section, and friction time. This study had also the purpose of testing the validity of the current fractal models in representing irregular particles.Methods. We used three kinds of hit-and-stick aggregation methods: two particle-cluster aggregations producing compact and extremely loose aggregates, respectively, and simplified cluster-cluster aggregation as intermediate class in terms of fluffyness and porosity. In our measures, we used two kinds of monomer shapes: spheres and elongated prolate ellipsoids with axis ratio 3:1 resembling the ones used to model interstellar dust grains.Results. We found that the monomer shape has little influence (
The influence of the monomer shape in the first stage of dust growth in the protoplanetary disk
Bertini I.
;
2009-01-01
Abstract
Context. Laboratory experiments have shown that the initial stage of the dust growth in the protoplanetary disk starts with low-velocity hit-and-stick collisions between sub-micron grains, before the relative impact energy becomes large enough to cause the morphological restructuring of the forming aggregates. The results of these collisions are loose aggregates characterized by fractal dimensions ≤2. Numerical studies generally model this early stage with colliding clusters made of monodisperse spherical monomers.Aims. In this paper we aimed to investigate how a more complex representation of the monodisperse monomers structure influences the morphology of the final aggregate particles in terms of fractal dimension, porosity, cross-section, and friction time. This study had also the purpose of testing the validity of the current fractal models in representing irregular particles.Methods. We used three kinds of hit-and-stick aggregation methods: two particle-cluster aggregations producing compact and extremely loose aggregates, respectively, and simplified cluster-cluster aggregation as intermediate class in terms of fluffyness and porosity. In our measures, we used two kinds of monomer shapes: spheres and elongated prolate ellipsoids with axis ratio 3:1 resembling the ones used to model interstellar dust grains.Results. We found that the monomer shape has little influence (I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
