Optimal Run Time & Understanding

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Hi Barry, ok I understand now.

so taking things through one at a time.

@Get_Barried

However does timestep with a length of 1000s mean that every 1s it re-runs the simulation?

so to clarify, if time step length is 1s and the end time is 1000s then we get 1000 timesteps, that is of simulated time, not real time or clock time. So if we simulated a building for say 100s in real time this would take an age, but the simulated time would be 100 seconds.

@Get_Barried

For example, how does “Clock Time” and “Run Time” differ?

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

I find most of these to not really be much good in my use cases, I tend to use timestep if steady state, this allows me to say when I want a write in terms of iterations, if transient I tend to use adjustable runtime, this allows me to make a garanteed write at a time regardless of weather im using automated timestepping.

@Get_Barried

Ah yes the transient simulation, I was playing around with that and for my use case I did get a different result that differs from steady state results by about 5%, may I ask how does it differ from steady state flow? Is it simply just the flow type or some underlying numerical change? Isn’t any underlying numerical flow change governed by the preliminary selection of the desired turbulence models? Or if you have some documentation I can read through to get a better understanding of such I would love to read through it!

This could be many number of things, but most likely:

1. You simulate a more accurate fluid flow due to transient flows (vortex shedding for example)
2. the transient flow is not fully developed, there is a certain amount of your simulation that is kind of not relevant at the begining where the flow pattern is still developing.

Hope this helps
Darren