Go to Common Results Node Settings for links to information about these sections: Data, Expression, Title, Quality, and Inherit Style.
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To get the length of the streamlines, use an Export>Plot node. In its Settings window, select the Only export starting points and endpoints check box to include one row with the starting point, the endpoint, and the length of the streamline for each streamline.
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The Selection section is available for some datasets when you select On selected boundaries from the Positioning list under Streamline Positioning.
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From the Arrow distribution list, choose Equal arc length (the default) to distribute the arrows uniformly over the streamlines’ arc length, Equal time to distribute the arrows using the weight function dt/darc, or Equal inverse time to distribute the arrows using the weight function darc/dt.
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Select the Number of arrows check box to enter a number for the total number of arrows, on all streamlines, that are plotted. By default, the COMSOL Multiphysics software provides a reasonable number of arrows.
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Specify a value in the Local time field (default: 0) for the local integration time along the streamlines for which the arrows are plotted. It is possible for integration times to be negative: For a starting point in the interior of a domain, streamlines are integrated both forward and backward in time unless you clear the Allow backward time integration check box in the Advanced section.
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You can move the arrows along the local time by moving the slider. You can also create this effect using a player animation in an Animation node under Export, using a Streamline sequence type.
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In the Extra release times field, enter any additional times for releasing arrows, or click the Range button () to define the extra release times. By default, there are no extra times.
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From the Arrow length list, choose Normalized (the default), Logarithmic, or Proportional to make the arrows’ sizes depend on the magnitude of the plotted quantity, if desired. If you choose Logarithmic, the length of the arrows is proportional to the natural logarithm of the magnitude of the quantity they represent. This makes arrows representing small values relatively larger. The value in the Range quotient field (default: 100) determines the ratio between the smallest and largest values in the range of values for the logarithmic arrow length.
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Use the slider, or select the Scale factor check box and enter a scale factor in the associated text field if you want to use another scaling than the one used by default.
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Specify a value in the Local time field (default: 0) for the local integration time along the streamlines for which the points are plotted. It is possible for integration times to be negative: For a starting point in the interior of a domain, streamlines are integrated both forward and backward in time unless you clear the Allow backward time integration check box in the Advanced section.
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You can move the points along the local time by moving the slider. You can also create this effect using a player animation in an Animation node under Export, using a Streamline sequence type.
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In the Extra release times field, enter any additional times for releasing points, or click the Range button () to define the extra release times. By default, there are no extra times.
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Select or enter an expression for the points’ radii in the Point radius expression field (SI unit: m). By default, the radius is scaled automatically. To enter a scale factor for the radius, select the Radius scale factor check box and enter a scale factor in the corresponding text field.
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Select the Fixed size check box if you want to display the points with a fixed onscreen size.
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The Integration tolerance field default is 0.01 for 3D and 0.001 for 2D. Edit to specify how accurately streamlines are computed.
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The Maximum streamline length field makes it possible to control the length of streamlines. Edit the default (Inf) to control the streamlines’ length. Enter the value as a fraction of the mean bounding box’s size. When the Allow backward time integration check box is selected (the default), the maximum length refers to the sum of the lengths of the forward and backward parts.
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The Maximum number of integration steps field makes sure that the integration does not continue indefinitely. Edit the default (5000) to control when the computation stops.
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The Maximum integration time field sets an upper time limit for the integration. The default is infinity (inf).
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The Stationary point stop tolerance can be adjusted to make sure the integration stops near a stationary point in the field. The default is 0.01.
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The Loop tolerance field default is 0.01. This is a fraction of the mean of the lengths of the bounding box of the geometry. If a streamline gets closer to its starting point than this distance, the streamline snaps to its starting point and is plotted as a connected loop. See also Method 5: Creating Streamlines with Variable Density and Magnitude Controlled.
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Select the Allow backward time integration check box to integrate points from the starting points both in the direction of the vector field and in the opposite direction. This check box is selected by default.
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Select the Normalize vector field check box if required. The vector field is normalized pointwise: For each point where the field was evaluated, the vector is replaced by a unit vector in the same direction. If you apply normalization, the speed along the streamline changes. This change means that the other settings in the Advanced section (for example, maximum number of integration steps and maximum integration time) are interpreted differently.
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The Selection section is made available for some datasets when On selected boundaries is selected from the Positioning list under Streamline Positioning.
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Under Selection, select the boundaries from which the streamlines start. By selecting in the Graphics window and using the tools in the Selection section, select the boundaries for the starting positions for the streamlines.
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Enter the Number of streamlines (the default is 20). This number is a suggestion for how many streamlines are generated, but there is no guarantee that you get exactly the specified number of streamlines. The reason is that the streamline starting points are placed in a regular grid on the selected boundaries.
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Enter x and y (2D) or x, y, and z (3D) coordinates (SI unit: m). Also use a scalar value to represent a fixed value for some of the coordinates.
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Enter the number of Points (the default is 20).
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From the Along curve or surface list, select None. The starting points are then distributed semirandomly but deterministically. You can also choose a Cut Line, Cut Plane, Parameterized Curve or Parameterized Surface dataset, if applicable, to restrict the streamline start positions to a cut line, cut plane, parametric curve, or parametric surface.
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Enter the Separating distance between the streamlines (the default is 0.05).
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The Advanced parameters list defaults to Automatic. If required, select Manual to edit these parameters: Boundary element refinement, Fraction of streamline length to ignore, Starting distance factor, Terminating distance factor, or First starting point.
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Edit the Boundary element refinement if streamlines do not behave as expected near boundaries on a coarse mesh — try increasing this number. It is a measurement of the density of points on the boundaries used to set up the structure and is used to measure distances between streamlines. Refining the mesh in the problematic area can also resolve the problem.
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Edit the value in the Fraction of streamlines to ignore field (a fraction 0–1; default value: 0.5) when a streamline is close to itself, typically for spiraling streamlines. This number controls how big part of the streamline, starting from its starting point, that the streamline itself is allowed to get close to, and it might in some cases be useful in order to get a less cluttered streamline plot.
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The Starting distance factor is a factor multiplied with the distance specified in the Separating distance field (as a fraction of the mean of the lengths of the bounding box of the geometry — the default value is 0.05). It sets the minimum distance between streamlines and the starting point for the next streamline.
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The Terminating distance factor is a factor multiplied with the distance specified in the Separating distance field. It sets the minimum distance between any pair of streamlines. Thus, this distance is the minimal distance under which the integration of a streamline stops.
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By default the First starting point list defaults to Automatic, and it sets the starting point for the first streamline. It is selected in the element where the highest value of the velocity of the specified vector field occurs. If required, select Manual instead to override the default and enter x and y coordinates.
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For 2D models, enter a Density (the default is 20). This value is roughly the number of streamlines. Prior to streamline generation, the software computes a rough estimate of the total flow of the flow field in the model, divides this value with the specified Density setting, and uses the resulting value as the flow between each pair of adjacent streamlines.
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For 3D models, enter the Min (minimum) distance and Max (maximum) distance between streamlines (the default Min distance is 0.05 and the default Max distance is 0.15). These distances are specified as fractions of the mean of the lengths of the bounding box of the geometry. The minimum velocity in the model is mapped to the minimum distance and the maximum velocity to the maximum distance. Thus every point on a streamline and on the boundary has a separating distance associated with it. Given a set of streamlines, the starting point for the next streamline is selected using these separating distances.
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If required, from the Advanced parameters list, select Manual to set advanced parameters as described in Method 4: Creating Streamlines with Uniform Density.
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It has used a predetermined amount of “time” for integrating (control this parameter with the Maximum integration time field).
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