# TIME_CUT_OUTPUT

Specifies parameters for the output of time cuts.

## Type

AcuTrace Command

## Syntax

TIME_CUT_OUTPUT {parameters}

## Qualifier

This command has no qualifier.

## Parameters

- active (boolean) [=off]
- Flag specifying if time cut output is active.
- time_cut_type or tcut_type (enumerated) [=time_series]
- Type of time cut specification.
- time_series or series
- Use a user-defined series of times.
**time_interval**- Use end points and an interval.

- time_cuts or tcuts (array) [={}]
- List of time values. Used only if time_cut_type is time_series.
- time_cut_start_time or tcut_start (real) [=0]
- Initial time cut value. Used only if time_cut_type is time_interval.
- time_cut_stop_time or tcut_stop (real) [=0]
- Final time cut value. Used only if time_cut_type is time_interval.
- time_cut_interval or tcut_interval (real) [=0]
- Interval between successive time cuts. Used only if time_cut_type is time_interval.
- flow_state_data or flow_state (boolean) [=off]
- Flag specifying whether to include the flow state in the output.
- flow_gradient_data or flow_gradient (boolean) [=off]
- Flag specifying whether to include gradients of the flow state in the output.

## Description

Particle traces are computed by AcuTrace as a series of segments. Time cut output is recorded for all active particles at the time cuts. The particle path is interpolated in time between the segment endpoints steps on either side of the time cut.

```
TIME_CUT_OUTPUT {
active = on
time_cut_type = time_series
time_cuts = { 1.1, 3.2, 7.3, 13.4 }
...
}
```

```
TIME_CUT_OUTPUT {
active = on
time_cut_type = time_interval
time_cut_start_time = 0.
time_cut_stop_time = 1000.
time_cut_interval = 10.
...
}
```

specifies that time cut output be written every 10 time units beginning at time zero and ending at time 1000. When time_cut_type equals time_interval, time cut values of time_cut_start_time and time_cut_stop_time are always used regardless of the value of time_cut_interval.

Time cuts that occur earlier than any of the particle start times or after all the particles have become inactive are ignored. It is therefore always safe to provide more than enough time cut values. If TIME_CUT_OUTPUT is the only active output type, the particle trace terminates when a time equal to the largest time cut is reached by all the particles.

The active, flow_state_data, and flow_gradient_data parameters control what information is recorded. No trace output is recorded unless active = on. By default, all particle outputs and no flow outputs are recorded when trace output is active.

Particle values are the state of the particle, that is, its position, time, particle velocity, and so on. The flow outputs are found by interpolating the AcuSolve flow field to the current position and time of the particle.

Particle outputs always include

- Seed ID
- Coordinates
- Time
- Particle velocity
- Element ID
- Element set ID
- Marker
- Particle velocity magnitude
- Trace length

They also include

- Particle mass
- Particle density
- Particle radius

if the parameter particle equals finite_mass model in the EQUATION command,

- Component values

if the parameter number_particle_components in the EQUATION command is non-zero,

- User equation values

if one or more user equations are specified by the user_equations parameter of the EQUATION command.

- Turbulence random seed

if the parameter turbulent_trace equals on in the TRACE_PARAMETERS command and

- Stretch vector
- Stretch magnitude
- Log stretch magnitude
- Stretch rate magnitude

if the parameter stretch does not equal none in the EQUATION command.

Flow state values always include

- Flow velocity
- Flow pressure
- Flow velocity magnitude
- Flow strain rate magnitude

They also include

- Flow temperature
- Flow species
- Flow eddy viscosity

if these are available in the AcuSolve database.

Flow gradient values currently include only

- Gradient of flow velocity

Note that for the massless particle motion equation, the particle and the flow velocity fields are identical except possibly for particle positions in elements next to a wall.