The Write control option under Simulation control gives you control over how fine granular your simulation results shall be available. This is only relevant for quasi-static or transient analysis types like the ones OPENFOAM® provides. The idea is that you specify how many time steps (real or quasi-static) shall be written to the hard disk and therefore be available for post-processing. For example, if you are simulating a transient process that takes 5 seconds simulation time, do you want to have the time steps 1,2,3,4 and 5 seconds available or also all 1.5, 2.5 and so on. There are different options how to specify this:
- Timestep: Specifies the write interval via the actual simulation time steps
- Runtime: Specifies the write interval via the computing time
- Clock time: Specifies the write interval via the real time, measured on the computing machine
- CPU time: Specifies the write interval via the real time, measured by the CPU
- Adjustable runtime: Specifies the write interval via the actual simulation time steps
The standard setting is to use the Timestep options which allows you to specify exactly which timesteps you are interested. The figure below shows an example for a steady-state simulation:
In this specific case, we are dealing with a steady-state simulation which means that the timesteps are quasi-timesteps. Therefore we simply have to make sure that the simulation runs a certain amount of iterations - the actual value of the time is not important. Here we are aiming at 100 iterations. The write control option Timestep with an interval of 100 means that we want to write every hundredth timestep. Since we are only computing 100 timesteps, this means that we are only writing the last timestep of this simulation.