People involved at OAB: Bedogni, Londrillo
The research activity in numerical astrophysics has been active in the following fields:
a) N-body code for galaxy merging numerical simulations. A new N-body code, based on the multipole scheme recently proposed by W.Dehnen (2000, ApJL 536, L36), has been inplemented in F90 and parallelized under MPI. The code represents a substantial improvement over existing tree-codes (e.g. the Gadget package), and assures a gain of at least a factor five in cpu time. The main numerical results based on this code will be presented at the INAF-CINECA Conference (Bologna July 4-5 2002).
b) Vlasov equation on a grid for astrophysical plasmas. A four-dimensional (two space + two velocity components) code integrating the electromagnetic Vlasov equation for charged particles on a grid has been developed and tested. The code is based on upwind, high order schemes both in space and velocity coordinates. Results have been presented at the Meudon Conference on Space Plasma Phenomena (Meudon, June 18-29 2001).
c) Three-dimensional MHD code for relativistic flows. A previously developed MHD code based on upwind, higher order WENO schemes (P. Londrillo and L. Del Zanna, ApJ 2000) has been extended to the relativistic regime, to cope with high energy astrophysical phenomena in radio jets. Results will be presented at the cited Bologna Conference.
Three dimensional MHD code for turbulence in RFP (Reversed field pinch) in laboratory plasmas. The code is based on spectral algorithms, and takes full account of toroidal geometry, compressibility effects and kinetic transport phenomena. The code is under scrutiny, and has been proposed in the frame of a collaboration activity with the Calabria Physics Department, to study relaxation and anomalous transport in weakly collisional plasmas.
d) The computation of the flow around a rigid object has been extended to the case of a cylinder in order to compare the behaviour of the drag with those of other computations carried out by different authors in numerical hydrodynamics literature.
The results above described have been applied to the investigation of protogalactic and protostellar formation. The effects of a variable drag are included in a one-dimensional code to follow the gravitational collapse of one and more clouds during a process of protogalactic and protostellar formation. In the same context, also the evolution of SN remnants interacting with clouds in the interstellar medium, both for Type I and Type II supernovae, has been computed, focusing in particular on the physical properties (e.g., kinetic energy, drag, mass loss by the cloud) of the turbulent wake behind the cloud.