Streamlines (control panel)
The control panel Streamlines is used to adjust parameters of the stream line evaluation.
A streamline shows a trace of a heat flow through any point within the construction. For 2D project traces are produced through several points placed at the surface of selected space.
If there is vapour solution available the flow of vapour diffusion can be visualized with this evaluation alternatively.
The evaluation is performed over the calculated field of heat flux vectors (or vapour diffusion flux vectors) at all nodes of the simulation grid – these fields are available only if evaluation of secondary functions has been chosen (in General the secondary functions is active!)
The streamline will be calculated over the active vector field by executing the Runge-Kutta method. The streamline (independently from the active function always follows the active vector field) is shown colorized. Only the colorizing of the streamline corresponds to the active function (temperature, heat flux etc.) as set in the General control panel and depends on the colour table selected.
Streamline through one probe point (Slice X/Y/Z)
The position of the starting point to trace the stream is defined by the intersection of the three slice planes Slice-X / Slice-Y / Slice-Z.
Therefore the slices X,Y,Z provide crucial part of parameters required for this evaluation and must be active (even if slices itself are transparent and not visible).
Streamlines at equidistant intervals of heat stream from space boundary in 2D case
For 2-dimensional models the streamlines can be automatically drawn out of space boundaries at equal intervals of heat stream (of that space). This functionality is available for 2D projects only.
Important: Streamlines are drawn in the plane of slice Z which must be active!
After the option "Start at ... Space Boundary" is selected, the name of the space the streamlines shall be drawn from can be chosen together with the number of intervals the stream of that space boundary shall be divided into. The application calculates the heat (or vapour) stream from/to the space, subdivides it into the given number of equal intervals and draws streamlines at each such calculated start value of the stream function.
This evaluation can be executed for 2D projects or for other project types, but only if the construction is absolutely homogenous in the Z-direction and there are no space connections in this direction also. If this variant of evaluation is actually available can be verified within the streamlines control panel - if the choice option "Start at: Space Boundaries" is inactive (shown greyed) then that type of evaluation is not available in the context of actual simulation results ergo of the actual model.
| Actve, Opaque, Colorize | Decide about the visibility, colorizing and transparency of the streamline |
| Integration Step length | The factor used to determine the minimal step length of the Runge-Kutta method. Small values lead to high number of iteration steps within each fine grid cell executed by Runge-Kutta method. More such steps (i.e. at small values of integration step) result in smother, more precise, stream lines. Small number of steps (i.e. large integration steps) result in coarse steam flow representation. The value also determines the minimum distance of how close the streamline can approach the surface boundaries of construction. At areas of very low stream densities the "progress" of a streamline at each iteration step is very small also. This might require enlarging the iteration step length to receive longer streamline at limited amount of iterations (reducing computation time also). |
| Max. propagation length | This number affects the number of integration steps of the Runge-Kutta method performed from the starting point until iterations, and thus tracking the stream field, are aborted. This number is important by defining the total length of a streamline. At areas of very low stream densities the "progress" of a streamline at each iteration step is very small also. This might require enlarging the maximum propagation length to receive longer streamline leading to higher number of iterations (increasing computation time also). High values of maximum propagation length will obviously increase the computational time required to create the streamline. |
| Terminal stream density | This number defines the magnitude of stream density (modulus of flux vector) below which the tracking of the stream field by Runge-Kutta method shall be aborted. At areas of very low flux the "progress" of a streamline at each iteration step is very small also. This might require lowering the terminal density value thus reducing the number of iterations (and reducing computation time also). |
| Tube Radius | The streamline is shown as a tube to better emphasize the stream (compared to single pixel thick line). The radius is entered in units of the coordinate system - i.e. millimetres. Setting the tube radius = 0 will show it as simple line. Remark: The number of sides rendered for the tube can be adjusted within application settings. |
Start at:
| The position of staring point is defined by the intersection of the three slice planes Slice-X / Slice-Y / Slice-Z or, for 2 dimensional models, one can chose to automatically generate starting points on space boundaries at equidistant intervals of heat stream. Remark: The second option is available for 2D projects only. |
| Space Boundary | The name of the space from which the streamlines shall be drawn |
| # intervals | Number if intervals the stream function calculated at the space boundary shall be divided into thus determining the starting points for streamline generation. Remark: High number of streamlines generated will result in high graphical memory demand. It is advised to set the tube radius to 0. Remark: If the stream flows to the space and (at other section of the space boundary) from the space, the highest amount is taken and divided into intervals. To visualize the dividing line between the areas of stream loss and stream win select division at 1 interval only. |
Remark: Because streamline (the flow) exists in model's interior only it is advisable to either turn the view of the surface completely off or show it partially transparent (i.e. not opaque) or show it as wireframe only. The same applies to the visibility of slice planes X, Y, Z - these must be active to receive stream line image (starting point of tracing) but shall be made partly transparent or even completely invisible (Opacity = 0) .
Remark: When surface humidity is selected as active function (panel General), the streamline is coloured grey only, because the function of surface humidity is defined at component's surface only.
Remark: Current implementation of the solution of the initial boundary problem posed here uses Runge-Kutta method of fourth order with adaptive step control. The boundary condition of step control is set to the small, still numerically stable, error value of epsilon = 10-8 and cannot be changed by the user.
The initial-, minimal- and maximal integration steps are determined by the user (Integration Step length). The minimal step corresponds to the value entered (default 0.0001 mm). The initial step length is 10 times the minimal value. The maximal step length is 100 times the minimal value.
The maximal propagation length corresponds to the total length of the resulting streamline in millimetres. The total number of line segments constructing the streamline is limited to 100.000 segments (higher number would overwhelm the capacity of today's hardware equipment when combined with tube visualization).
Remark: Start at – Probe X/Y/Z: The position of staring point of a streamline is defined by the intersection of the three slice planes Slice-X / Slice-Y / Slice-Z.
Therefore all slice planes X, Y, und Z must be active (even if fully transparent), and the intersection of the three must be within model's interior.
If the intersection of the slices X/Y/Z (we call it the probe point) is located very close to components surface it might happen that no stream line can be started from there. Shall this (rare) situation arise you will have to shift the starting point by at least the half of the smallest size of the fine grid cells (i.e. the start thickness of the fine grid parameters, typically 0.5mm or 1mm).
Remark: Start at – Space Boundary: Produces many streamlines started at selected space boundary. The application calculates the sum of stream flowing to the space and the sum of stream leaving the space through the boundary (for exterior space, case with two spaces without powers sources one of this values is always 0). The sum with the largest modulus is divided into the number of intervals entered (maximum 200 intervals, i.e. at 0.5% of the heat stream). Along the space boundary the application repeats the calculation of the stream function and places start points for the streamline at interval boundary values calculated earlier (interpolated). To ensure, that every streamline will start each starting point is shifted towards the interior of the model by about the half thickness of the surface fine grind cell (typically 0.5mm or 1mm).
See also: Results 3D window, Active (settings), Opaque and Opacity (setting), Colorize (setting), Solid or Wireframe (setting), General (control panel), Active Function, Isolines (Isotherms), Slice X,Y,Z (control panel), Surface (control panel), HedgeHog (Arrows) (control panel)