About
SIMMSUS is a research code written in FORTRAN that simulates the motion of a system of interacting particles. These particles can be simulated in different scenarios and may interact through different physical mechanisms. The code was initially developed for studying the physics of magnetic spherical particles in suspensions in order to better understand the properties of magnetic fluids (ferrofluids).
Since the beggining of the development, the code was designed to consider the effects of Brownian motion, long range dipole-dipole and hydrodynamic interactions. The first physics simulated through SIMMSUS was the study of the alignment of the particles in the direction of an applied steady-state magnetic field to see wether the code was capable of capturing the behavior of the equilibrium magnetization predicted by theoretical asymptotic models available on the literature (Ivanov and Kusnetsova, 2001).
The comparison between the predictions of SIMMSUS and the asymptotic models served as a first validation of the numerical code. After this initial validation, we have implemented several additional features on the code and have used SIMMSUS to explore different physical situations regarding the behavior of magnetic fluids. Many of the studies conducted through SIMMSUS have been published in prestigious academic Journals, such as Physics of Fluids, Journal of Magnetism and Magnetic Materials, Powder Technology and Mechanics Research Communications.
In its present version SIMMSUS is capable of simulating Brownian and non-Brownian suspensions and the user can turn on/off specific physical mechanisms in order to build a customized scenario. For example the user can mix magnetic particles with non-magnetic particles, turn on/off the gravitational field, apply an oscillatory or steady-state magnetic field over the particles, apply a simple or oscillatory shear over the particles, simulate different initial configurations (ordered, random or spherical distributions), simulate mono or polydisperse particles (with the same radius or with different radius) and the list goes on.
Regarding the application of time-dependent magnetic fields, we have conducted a rigorous study on the dynamical susceptibility response of ferrofluids using SIMMSUS and have validated the dynamical solution of the rotational motion of the dipole moments of the particles provided by the code by comparing the numerical solution with an asymptotic theoretical model (Berkov et al, 2009). The code seems to predict with excellent precision the dynamical behavior of the internal structure of ferrofluids.
History of SIMMSUS
Why FORTRAN?
Nowadays few people program in FORTRAN and the fact that SIMMSUS has been written in FORTRAN may sound strange to many young programmers that are more familiar to popular languages like Python. However, it is not a secret that Physicists and Engineers have been using FORTRAN for a long time. FORTRAN is a compilable, intermediary level language that has been evolving with the processors we use to perform our calculations since the 50s. When it comes to solve problems that demand great computational effort FORTRAN seems to be one of the preferred languages among scientists. SIMMSUS deals with a great amount of heavy calculations in order to simultaneously compute multiple simulations with many particles through several time-steps solving highly complex equations. Therefore, we have chosen to write SIMMSUS in FORTRAN. Also, SIMMSUS was created to simulate problems for scientific purposes and developed in an academic enviroment. So it was created around a culture where people really like FORTRAN. Since FORTRAN is a compilable language, the performance of the solver is strongle affected by the quality of the compiler used to build the executable file (program). Therefore, we strongly recommend you to compile SIMMSUS with Intel Fortran Compiler in Linux enviroment, since this was the enviroment in which SIMMSUS was programmed and tested so far.
About the author
Prof. Rafael is a Mechanical Engineer and has a PhD in Fluid Mechanics. He has been a Professor since 2009, teaching fluid mechanics, heat transfer, continuum mechanics, hydrodynamics of magnetic fluids and related topics at the University of Brasília (UnB). His main research interests are: microhydrodynamics and rheology of complex fluids, hydrodynamics of magnetic fluids, Stokesian and Langevin dynamics applied to numerical simulations of dipolar suspensions. He has also founded the Youtube Channel Ciência e Brisa where he makes several of his courses available for anyone interested in pursuing this path to knowledge.