An IBIS program is a collection of commands that initialize the IBIS immersed boundary/fluid dynamics calculations. The commands describe the fluid dynamics variables, the immersed boundary initial locations, the elastic properties of immersed boudaries, and control the execution and output of the simulation.
Every IBIS program contains several types of executable statements. The first set of statements is required and define the basic computational parameters such as the physical domain, computational domain and timestep. These statements also define the output control such as the frequency of output, the type of output and output filenames.
The remaining types of statements define the attributes of the simulation, the properties of the domain, and most importantly, the entities and their elastic link attributes.
Next we describe the language statements based on their types. Then we give a concise synopsis of each language element. Finally, we give numerous examples and in which we explain each line of the IBIS program.