[TIMESTEPS] Section

Purpose

In former versions, the main time step was fixed to 10s. It has turned out that this time step can be too large for certain cases which causes troubles in form of numerical instabilities. Therefore, ENVI-met provides now a dynamic adaptation of the main time step. The criteria for time step selection is the height of the sun.

Smaller time steps are normally required when the solar input is high, whereas bigger ones can be used in the morning or evening. The solar height is divided into 3 intervals, defined by 2 boundary values of the sun height heightA and heightB.

The intervals are:

  • Interval 1 (class 0 timestep): Sun height < heightA
  • Interval 2 (class 1 timestep): heightA⇐ Sun height < heightB
  • Interval 3 (class 2 timestep): heightB ⇐ Sun height

You can assign individual time steps to each of the intervals. Normally, the time step for interval 3 should be the smallest as this time interval is active when the sun height is at its maximum. Also, you can change the boundary values for switching between the interval. Both can be achieved in the ENVI-guide.

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