FAQ/ How to Set the Calculation Time Step¶
How do I set the computational time step for a simulation?
Does it need to be set up by the user through trial and error?
Or is it automatically set to the appropriate value?
response¶
The calculation time step is automatically set by DioVISTA and adjusted to the appropriate value.
DioVISTA sets the calculation time step to meet the CFL requirement. The CFL condition is the condition under which the calculation in the explicit simulation is stable.
The coarser (larger) the time step, the shorter the calculation time.
If the time step can be increased, DioVISTA gradually increases it by 2x, 4x, 8x, and so on.
Conversely, if the time step needs to be reduced, gradually reduce it by 1/2x, 1/4x, and 1/8x.
The model of DioVISTA and the initial value of the time step are shown in the table.
For example、..., for a flood model 0.25, 0.5, 1, 2, 4, ... This can be one of the second values.
That is, it takes a value of 2n times the initial value of the time step.
Table: Initial values of the model and time steps
| model | Initial Time Step (s) |
|---|---|
| Spillage model | 64 |
| River model | 16 |
| Flood Model | 1 |
| Levee Failure Model | 1 |
| Drainage Basin Model | 1 |
| Drainage station model | 1 |
| Full Sync | 1 |
Before Version 3.4.4
Prior to version 3.4.4, the initial values of the time step were:
| モデル | 時間ステップの初期値 (s) |
|---|---|
| 流出モデル | 60 |
| 河川モデル | 10 |
| 氾濫モデル | 1 |
| 破堤モデル | 1 |
| 遊水地モデル | 1 |
| 排水機場モデル | 1 |
| 全体同期 | 1 |
Related item¶
- FAQ/ I want to specify the calculation time step width
- Technical Reference/ Flood Model/ CFL Conditions
- Technical Reference/ River Model/ CFL Conditions