diff --git a/data/astro.md b/data/astro.md index 11d1ffa9ff13903bff36cb18fbab753fff013b78..24593782633a7215621228c2f170217919282c81 100644 --- a/data/astro.md +++ b/data/astro.md @@ -1,10 +1,10 @@ # Astronomer -Want to get started using SWIFT? Check out the on-boarding guide available -[here](onboarding.pdf). SWIFT can be used as a drop-in replacement for -Gadget-2 and initial conditions in hdf5 format for Gadget can -directly be read by SWIFT. The only difference is the parameter file -that will need to be adapted for SWIFT. +Want to get started using SWIFT? Check out the on-boarding guide +available [here](onboarding.pdf). SWIFT can be used as a replacement +for different codes and initial conditions in hdf5 format from +commonly used generators can directly be read by SWIFT. All you then +need is a parameter file adapted for SWIFT! SWIFT combines multiple numerical methods that are briefly outlined here. The whole art is to efficiently couple them to @@ -13,20 +13,19 @@ exploit modern computer architectures. ## Gravity SWIFT uses the Fast Multipole Method (FMM) to calculate gravitational -forces between nearby particles. These forces are combined with -long-range forces provided by a mesh that captures both the periodic -nature of the calculation and the expansion of the simulated universe. -SWIFT currently uses a single fixed but time-variable softening length -for all the particles. +forces between nearby particles. These forces can be combined with +long-range forces provided by a mesh that captures the periodic nature +of the calculation. SWIFT currently uses a single fixed but +time-variable softening length for all the particles. As well as this self-gravity mode, we also make many useful external potentials available, such as galaxy haloes or stratified boxes that are used in idealised problems. -Gravitational accuracy can be tuned through use of the opening angle -and the choice of a multipole order for the short-range gravity -calculation. The mesh forces are controlled by the cell size and -frequency of the update. +Besides softening, gravitational accuracy can be tuned through use of +the adaptive opening angle and the choice of a multipole order for the +short-range gravity calculation. The mesh forces are controlled by the +cell size and frequency of the update. ## Cosmology @@ -47,7 +46,7 @@ mode of operation of SWIFT!) when taking them from a different code. There are many hydrodynamics schemes implemented in SWIFT, and SWIFT is designed such that it should be simple for users to add their -own. +own variations. All the schemes can be combined with a time-step limiter inspired by the method of [Durier & Dalla Vecchia @@ -57,6 +56,17 @@ sudden injection of energy such as in feedback events. The four main modes are as follows: +### SPHENIX SPH + +This is our default Smoothed Particle Hydrodynamics scheme. It is +fully described by [Borrow +2022](http://adsabs.harvard.edu/abs/2022MNRAS.511.2367B). The core +equations use a density-energy formulation of the equations of motion. +This is combined with a variable artificial viscosity and +conduction. These are accompanied by limiters to only apply these +extra terms where they are necessary. This scheme was designed with +galaxy formation applications in mind. + ### Minimal SPH In this mode SWIFT uses the simplest energy-conserving SPH scheme that @@ -77,7 +87,10 @@ viscosity scheme with a [Balsara](https://www.ideals.illinois.edu/handle/2142/23836) switch. Note that the GADGET-2 SPH scheme is implemented to be the same as in the public release of GADGET-2. This is to enable users to -use SWIFT as a drop-in replacement for GADGET-2. +use SWIFT as a drop-in replacement for GADGET-2 and of course for +comparison exercises! + +<!-- ### Pressure-Entropy SPH @@ -109,6 +122,8 @@ diffusion but also comes at a higher computational cost. <div class="videowrapper"><iframe width="100%" height="100%" src="https://www.youtube.com/embed/sce-AWTbXFI" frameborder="0" allowfullscreen></iframe> </div> +--> + ## Subgrid models for galaxy formation SWIFT implements two main models to study galaxy formation. These are @@ -160,8 +175,7 @@ the classic method of post-processing simulations after they are run. ## Documentation and tests There is a large amount of background reading material available in the -theory directory provided with SWIFT. You will need pdflatex to build -this documentation. +theory directory provided with SWIFT. SWIFT also provides a large library of hydrodynamical test cases for you to use, the results of which are available on our developer Wiki