### 20.1.3. Basic Settings for Transient Simulations

#### 20.1.3.1. Transient Scheme

For details, see Transient Scheme in the CFX-Solver Modeling Guide.

#### 20.1.3.2. Convergence Control

You will have already specified the number of timesteps under Analysis Type. For details, see Analysis Type.

##### 20.1.3.2.1. Min. Coeff. Loops

This option determines the minimum number of iterations per timestep, and has a default value of 1.

Important: If a compressible transient flow is undertaken with only one iteration per time step, then the solution can be incorrect if the Heat Transfer option is not set to Total Energy, or if heat transfer is not included in the simulation. This is due to the CFX-Solver not extrapolating the pressure at the start of the time step in these circumstances. This means that density is not extrapolated, and so the solver cannot calculate an accurate value for the time derivative of density on the first iteration. The workaround for this problem is to either run with at least two iterations per time step, or to use the Total Energy option for Heat Transfer.

##### 20.1.3.2.2. Max. Coeff. Loops

This option determines the maximum number of iterations per timestep, and has a default value of 10. For details, see Max. Iter. Per Step in the CFX-Solver Modeling Guide.

##### 20.1.3.2.3. Fluid Timescale Control

Coefficient Loops is the only available option.

##### 20.1.3.2.4. Solid Timescale Control

To control the solid timescale for transient runs (including transient blade row runs), use the controls provided in the details view for the solid domain, on the Solver Control tab. For details, see Timescale Control for Solid Domains (Transient Cases).

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