Probe¶

Introduction¶

Probes are sampling locations placed inside the fluid domain which record the time-evolution of local flow properties at a specific point. A probe may remain fixed in space, follow the motion of the fluid as a tracer, or move along a prescribed trajectory.

During runtime, probe data can be referenced by global variables when the Data Source is set to probe, enabling use in control logic or event triggers. For post-processing, the recorded time history for each probe is written to an individual output text file. These files are particularly useful for temporal or path-based analysis, including lifeline tracking, spectral analysis, mixing characterization, or exposure-based metrics.

Download Sample File: Probe Prescribed Motion

Property Grid¶

`General`¶

Initial Location

m | This is the initial location of the probe. Fixed probes will not move from this location. Fluid tracer probes will move from this location according to the fluid velocity. Prescribed motion probes will be displaced relative to this initial location.

Start Time

s | This is the time at which the probe will enter the system and start recording data.

Probe Option

This setting controls how the probe position evolves during the simulation.

Fixed: The probe remains at its initial location for the duration of the run. This mode is appropriate for stationary instrumentation such as dissolved oxygen sensors, pH probes, or level indicators.

Download Sample File: Probe Fixed

Fluid Tracer: The probe behaves as a massless tracer and moves according to the local fluid velocity field. This option is useful for representing entities that are carried by the flow, such as suspended cells or particles.

Download Sample File: Probe Fluid Tracer

Prescribed Motion

The probe follows a user-defined displacement controlled by a UDF. This mode is suitable for tracking equipment or interfaces with known motion, such as impeller blades, baffles, or free surfaces.

Displacement X UDF: m | This UDF defines the probe position relative to the initial x-location as a function of time. This is a System UDF.
Displacement Y UDF: m | This UDF defines the probe position relative to the initial y-location as a function of time. This is a System UDF.
Displacement Z UDF: m | This UDF defines the probe position relative to the initial z-location as a function of time. This is a System UDF.

Download Sample File: Probe Displacement

`Display Attributes`¶

Visible

This controls whether the object is displayed in the 3D viewing panel.

Hidden

The object is not displayed in the 3D view.

Shown

The object is displayed in the 3D view.

Mode

This controls how the object is rendered.

Wire

This renders the object as a wireframe.

Color: This sets the color of the wireframe.
Width: This adjusts the line width used to render the wireframe.

Shaded

This renders the object as a shaded surface.

Material: This sets the surface material. Available options are Aluminum, Steel, Chrome, Plastic, and Glass.
Color: This sets the surface color.
Opacity: When glass is selected, this sets surface opacity.

Probe Data¶

The time-evolving data from each probe will be recorded in tab-separated ASCII .txt files. Each probe will have a unique output file with a file name linked to the dynamic name of the probe.

The data printed to the ASCII data files will be the combined selections of the Probes/Planes Output Controls and Volume Output Controls. A preview of the data printed to each output file is listed in the Statistics Output Data preview panel. The ASCII .txt are appended with updated data at the Statistics Output Write Interval.

In addition to the ASCII files, the position and velocity of the probes will be printed to a binary .vtp file. The .vtp files are used for rendering and visualization within M-Star Post. These visualization files are printed at both the Plane/Probe Output Write Interval and the Volume Output Write Interval, allowing for concurrent animation of probe and fluid/particle dynamics on 2D and 3D renderings.

More information about the .vtp file structure, see the Visualization Toolkit.

Static Probe Toolbar¶

Context-Specific Toolbar Forms	Description
Move	The Move form enables three-dimensional rigid body transform of object through free drag or point-to-point snapping.
Rotate	The Rotate form enables three-dimensional rotation of geometry.
Help	The Help command launches the M-Star reference documentation in your web browser.