Features:

~ FLOWVIZ ~
A Flow Visualization programm by Thomas Lidy

Features:

This is what you are able to do with this programm:

visualize pressure, vorticity or speed of a flow field
show an arrow plot of the flow field (with selectable arrow size)
show streamlines along the flow field
zoom into the data
user interaction: set streamlines per mouse click
open multiple output windows (to easily compare different kinds of visualization)
adjust the output window size as you like it
select colors of streamlines and pressure/vorticity data
select streamline integration method (Euler, Runge-Kutta)
adjust the streamline placement parameters (d.sep, d.test)

Installation:

Unpack all files into a directory of your choice. You will need Windows as your operating system.

Start the programm with the file FlowViz.exe.
You will additionally need data files in order to be able to visualize a flow field :-)

The standard data files (which were used while writing the application) are
- c_block.gri (the grid file)
- c_block.00000.dat (the flow data file)
which are supposed to be in the sub-directory /data.

Application Description:

This is a Screenshot of the FlowViz application:
(The parameters of the application are described below.)

The screen is mainly divided into 4 sections:
- the option bar on the top
- the information bar on the left
- the status bar on the bottom
- and the main area, where you can create several visualization windows.

After selecting the options click 'Draw in new window' on the option bar to create a new window, on which your options will be applied. If you just click 'Draw' the current window will be repainted with the current options.

Detailled description of the options you can choose:

Select the background:
Pressure, vorticity or flow speed of the field can be shown behind.
The according colours for positive and negative regions are shown on the information bar.
Grid points:
The grid points of the original data set are shown as white pixels. If there are a lot of grid points, large parts of the window will be white. Each pixel which is not white, is consequently being interpolated.
Streamlines:
The "separating streamline algorithm" is applied with the parameters d.sep and d.test, and the chosen streamline colour.
Also, the current integration method and the current value of dt are applied (see below).
Streamline color:
The color for the streamlines which will be drawn with the above algorithm can be changed here. This is also the color, which will be user in 'user streamline placing' mode (see below).
Simply click into the coloured region to change the colour.
Arrow plot:
This option will draw arrows which show the flow direction in evenly spaced positions.
Arrow size:
The size of the arrows in pixels.
Streamline options:
d.sep: the distance of one streamline to another, given in pixels.
d.test: percentage of d.sep, indicating the region of the streamline distance, which can be entered by another streamline.
1/dt: the integration parameter dt can be set here: for example a value of 100 means dt = 0.01 (1/100).
The higher 1/dt is, the more accurate the calculation will be, however the longer the calculation of a streamline will take.
Mouse functions:
- position info: Whenever this option is on, the status bar shows information about the flow data at the current pixel position in the drawing window.
- set streamline: enables 'user streamline placing' mode. Click with the left mouse button anywhere in the drawing window to set an additional streamline.
- zooming: A very powerful option: You can zoom into the flow field as deep as you like. See below for a detailled description.
Draw window:
Select the width and the height of the drawing window (before creating a new window).
If you select 'aspect ratio', the window will have the same width/height relation as the grid of the flow field has. (not yet implemented)
Integration Method: (in the Menu Bar)
You can change the integration algorithm, which is used in streamline calculation: Euler or Runge-Kutta 2.
Pressure, vorticity or flow speed colours:
You can also change the colours for the background visualization option: Depending of what is selected above you can change the colour for the positive and/or negative region of pressure, vorticity or flow speed.

Zooming:

If zooming is selected in the Mouse options, you can arbitrarily zoom into the flow field. That means, you can enlarge details which you are interested in.

To zoom in
... press the left mouse button at the start position of your desired zoom region (and hold down the button)
... move the mouse cursor to the end position of the zoom region (indicating a rectangle)
... and release the left button.

The window will immediately redraw - with the parameters which you've selected first - showing the selected zoom region.
The information bar on the left will show you the selected zoom section in small as an orientiation. (not yet implemented)

To zoom out
... just press the right mouse button anywhere in the drawing window.

The window will redraw in the original size, showing the whole flow field.

Example Images:

Arrow Plot (arrow size 10), background: pressure (red: positive, blue: negative)

Arrow Plot (arrow size 20), background: flow speed

Flow field with streamlines. d.sep = 6, d.test = 50 %; background: flow speed

Flow field with streamlines. d.sep = 10, d.test = 90 %; background: flow speed

Flow field with streamlines. d.sep = 15, d.test = 50 %; background: flow speed (other color)

Flow field with green streamlines - zoomed. (background: flow speed)

Visualizing pressure (color coding shown at legend) + some user placed streamlines.

Visualizing vorticity with a strong zoom around to block.

Flow field with streamlines - slightly zoomed. d.sep = 15, d.test = 60 %; background: pressure

Same as above - stronger zooming shows much more details.

Flow field with streamlines. Integration method: Euler. d.sep = 30, d.test = 60 %, dt = 0.02; background: flow speed

Same as above. Integration method: Runge-Kutta-2.

User placed streamlines - Euler vs. Runge-Kutta-2; dt = 1/10. (background: pressure)
The red streamlines were placed with Euler, some blue streamlines were placed with RK2 on top of the red ones.

Known Issues:

There are some drawing problems with the child windows.
To avoid most of them, the child windows are created at a fixed position in the white area.
Unfortunatly, when creating multiple child windows, additional windows will be created behind the 1st window!
So you will have to move away the 1st window - but be careful: Moving the window over one of the 3 bars will introduce new trouble ...

Also, with some (?!) window sizes, there is a debug error message (or crash) when closing the child window. Better keep the default window width & height.

Limitations:

File names currently hardcoded. No File Dialog!
User set streamlines are not redrawn when window is moved or repainted (i.e. they are lost).