Creating Streamlines

Streamline displayers render solution data on streamline derived parts in a scene. Streamline displayers are responsible for visualization only—controls for streamline integration are found on the streamline derived parts themselves.

If you have not already created one or more streamline or constrained streamline derived parts, do so using the right-click menu of the Derived Parts node. See Defining a Streamline. You select the vector field from which the streamline path is computed using the Vector Field property on the derived part (not in the scene displayer described here).

To render streamlines in a scene:

Within the Scenes node for the chosen scene, right-click the Displayers node and select New Displayer > Streamline.
Select the [streamline displayer] > Parts node and set Parts to one or more streamline or constrained streamline derived parts.
To select the quantity that you want to render on the streamlines, select the [streamline displayer] > Scalar Field node and set Function to a chosen scalar function.
If you want to render streamlines in a constant color (instead of rendering a solution quantity), select the [streamline displayer] node and set Color Mode to Constant.
Other coloring choices are available for streamlines as detailed in Displayer Properties Reference.
By default, streamlines are rendered as Tubes. To change this style, select the [streamline displayer] node and set Mode to Lines or Ribbons.

The property that controls the width of a streamline changes according to the Mode.

To control the width of a streamline, change the relevant size property:
- When Mode is Tube, set Width to a diameter.
- When Mode is Ribbons, set Width to a size.
- When Mode is Line, set Line Width to a relative value between 0.0 and 10.0.

If you want to show the direction of a streamline, you can add arrows at regular intervals along the streamline.

To add arrows along a streamline, select the [streamline displayer] > Markers node and activate Display End Point Markers.
If the streamlines are too long for the arrows to be effective, you can set Display Intermediate Markers to one of the options. See Displayer Properties Reference for details.

You can combine changes to streamline integration properties with changes to streamline rendering properties such that you obtain effects not possible with vectors alone. For example, to examine flow direction around a specific location, you can combine constrained streamlines with a constrained section plane and adjust the streamline properties so that curved arrows are rendered.

To examine flow direction around a specific portion of the simulation domain:
1. Right-click the Derived Parts node and choose New Part > Section > Constrained Plane. Define the constrained plane such that its contour loop surrounds the portion of interest.
2. Right-click the Derived Parts node and choose New Part > Constrained Streamline. Within the Edit dialog, set:
  - Seed Mode to Part Seed
  - Input Parts to the [constrained plane section] created above
  - Seed Parts to the same [constrained plane section]
  - Part U-Resolution and Part V-Resolution to values consistent with the size of the constrained plane. Start with low numbers as you can increase these values later
  - Direction to Forward
  - Display to a New Streamline Displayer (unless you have an existing one available).
3. After creating the [constrained streamline], expand its node, select the 2nd Order Integrator node and set Initial Integration Step to a small value. Set a sufficiently small value such that the streamlines are broken into smaller segments.
  You can preview the effect of property changes by selecting the [constrained streamline] node; a highlighted preview appears in the graphics window (assuming that you have a scene open).
4. To increase or decrease the number of streamlines, select the [constrained streamline] > Source Seed node and change N Grid Points to higher or lower values. If the streamline pattern misses some parts of the flow, activate Randomize.
5. Select the [scene] node that contains the streamline displayer containing the constrained streamline part.
6. Select the [streamline displayer] node and set Color Mode to Constant.
7. Select the [streamline displayer] > Color node and set Color to Black.
8. Select the [streamline displayer] > Markers node and activate Display End Point Markers.
  If you set the Initial Integration Step to a low enough value previously, the constrained streamline is now rendered as curved vectors rather than continuous lines.