Streamlines
Streamlines are a fine tool to study the characteristics of the air flow. They represent a composition of curves that are tangent to the velocity vector (see above), showing the direction in which a massless fluid element will travel at any point in time (see explanation at https://www.grc.nasa.gov/WWW/k-12/airplane/stream.html).
The colours visualise the speed of the particles moving through the wind tunnel. The associated velocities are explained in the panel.
For a vivid visualisation of the air flow, activate the Streamlines Animation in the panel or on the Results menu. You can then watch the fluid particles flowing around the model and examine their speeds and directions.
The graphical settings of the streamlines are controlled in a separate section of the panel. You can access it by clicking Streamlines Settings in the panel or on the Options menu, pointing to Streamlines.
Control Points Source
The streamlines refer to control points that are created automatically. You can modify the number of points with the slider.
By default, the control points are located within a 3D Box. It is possible to select a different type of source from the list (see image to the left), but those options are only relevant for specific evaluations.
When the Show Manipulator option is enabled, you can change the size and location of the 3D box graphically in the work window. The functions of the arrows correspond to those for modifying the wind tunnel (see the Chapter 'Wind Tunnel'). Click [Apply] to transfer the new settings.
Particle Animation
Use the Animation option to switch the display of the animated view of the streamlines in the work window on or off.
By default, the flow of the particles is displayed as Lines. When you select the Particles option from the list, you can examine the direction and speed of the particles around the model.
To modify the settings of the animated streamlines, click the [Animation options] button. Alternatively, open the Options menu, point to Streamlines and select Streamlines Options. The following dialog box is opened.
Streamlines
The Display streamlines when animating movement of particles option controls whether the lines are shown when the Particle type of animation has been selected (see above). Furthermore, it is possible to increase the Line thickness of the streamlines display. The Calculation of streamlines is effectuated both Downstream and Upstream by default. The former option enables you, e.g., to visualise effects of drag, the latter to display lift in detail.
Animation of Particles and Flowlines
In this section of the dialog box, you can control the Count (number), Size (thickness), Length, or Speed of the particles and streamlines utilised for the animated display. Use the slider to increase or reduce the individual parameters.
Click [Apply] to review modified settings in the animated view without closing the dialog box.