The heat-transfer program is a tool to help people understand how heat is moved from object to object. The user places various materials on a sqare grid, giving each a starting temperature. The user is then given a grapihcal representation of the temperature changes. The program can easily show, for example, that the temperature of gold changes much faster than the temperature of rubber. The numerical method used in the software is described in the reference given below. Basically, the method has the following features: second-order accurate in both space and time, stable for any size of time step, accurate in the treatment for interfaces between materials, conservative and iterative. Numerical errors undergo quick damping when the size of time step is very large. [1] W. Dai and P. R. Woodward, Numerical simulations for nonlinear heat transfer in systems of multi-materials, J. of Comput. Phys., vol.139, pp.58-78, 1998.

heat-transfer.tcl version 0.9 June 26, 1998

USAGE

heat-transfer.tcl [cmap ] [#] where cmap indicates the user wants to use a custom color map (indexed form -- use icol), and file is the filename of the color map and where # is a numerical value, stating the number of image files the user wishes to have created.

heat-transfer.tcl is an interface for a heat-transfer simulation program. The simulation was written by Wenlong Dai, and the interface was designed and written by Christopher White.

When starting the program, the user has a choice of command-line arguments. These include:
1) A number: States how many image files are desired. The higher the number, the smoother the resulting movie will be, but the more hard drive space is required; there is little speed difference however.
2) cmap : The keyword 'cmap' followed by a filename containing a colormap. The program will then use that color-map when displaying the movie. Make sure the colormap is in indexed form! Use 'icol' to create it.

After the user starts the program, they are presented with a list of materials. They must select one of these materials to be the "base" material for the simulation. Think of this as a plate where other objects of various temperatures will be placed.

Next, the main display screen will appear. This is a large square surrounded by four sliders. Each slider represents the temperature being applied to the side of the plate. The user can now add more objects to the plate.

1) Put the mouse cursor over the large square. - Notice that the arrow now becomes a pen.
2) Click and hold the left mouse button - This places the first corner of the box
3) Drag the mouse around (with the mouse button still down!) - This draws the box on the main plate. The size and shape of the box is displayed, and can be changed until the left mouse button is released.
4) Release left mouse button - Once the left mouse button is released, the box is placed, and the material list is presented again. This dialog refers to the material you just placed on the main plate.

The user may add as many objects onto the main plate as they wish.

After all desired objects have been placed, the user must click on the "Start" button located in the lower right hand corner of the main window. This will bring up a dialog box indicating that the image files are being created. Since this process is very time consuming, the user has the option of viewing the movie at any time by clicking the "Movie" button. This will call the xraz program (see REQUIREMENTS), which will display all frames that have been computed. The user may exit xraz, then click on the "Movie" button again to view more frames, since the frames are still being calculated as the movie is being shown. To stop the simulation, click the "Stop" button. When all of the images have been created, the "Stop" button changes to "Done" and is to be clicked when the user is done viewing the movie, or wants to save the script/movie.

After stopping the program, the user can either quit the program, edit the existing design, save the current movie, or save the current script used to create the movie.

FILE MENU

Under the FILE menu are 5 choices:
1) Run Script: This is used to load in a previously saved script to create the movie again. This is slower than saving the actual movie, since the movie must be recreated to be viewed again, but uses much less disk space.
2) Save Script As: This saves your current script; note that you must be finished with the design before saving, as there is no way to modify a saved script (see LIMITATIONS).
3) Open Movie: This option will display a previously saved movie. This is much faster than running a script, since the image files are already saved, but takes up much more disk space.
4) Save Movie: This option is used after you have created a movie and wish to save it. Be aware that the more frames the movie contains, the more disk space is required.
5) Quit: End the program; this is the same as the Quit button in the lower left hand corner of the main screen.

REQUIREMENTS

1) WISH8.0 In order to run this program, wish8.0 must be installed on the system. By default, the program looks in /go/local/bin/wish8.0. Edit the first line of heat-transfer.tcl to point to the location of wish8.0 on the system. Be sure to leave the first two characters of the line alone (#!).
2) RAZ/XRAZ raz and xraz must both be available on the system, and both should be in the user's PATH variable. If not, then the movie will not be shown.
3) X128 & X256 These binary programs do the actual calculations for 128x128 resolution, and 256x256 resolution respectively.

INCLUDED FILES

1) README: This file!
2) cmap_convert, creatCbar, origcmap, make-tbar: These files are used to create the colorbar when you are viewing the movie.
3) x128 x256: These are the main program which does all of the computations. While it can be run interactively, it is highly recommended that you use the heat-transfer.tcl interface instead. Some features are only available through that interface.
4) heat-transfer.tcl This is the main interface which controls the heat process. This is the only program the user will need to worry about, as it makes calls to all of the other programs.
5) xrazscript.128 & xrazscript.256 This is a configuration file used to start up xraz. Do not modify it.

LIMITATIONS/IDEAS FOR FUTURE VERSIONS

1) Once a box is drawn on the screen, its properties (size, temp, material, location) can not be changed.
2) If a box is started, and then the user changes their mind and no longer wants the box, there is no way to back out; a kludge to this is to simply set the new material to the same material and temperature as the main material. However, if the box overlapped several other boxes, this no longer works.
3) If the user closes the raz window instead of the xraz window, the heat-transfer program, as well as xraz, crashes. ALWAYS USE THE EXIT OPTION IN THE XRAZ PROGRAM! This is a bug in xraz.
4) When creating the movie files, the user may click "Movie" to view the movie up to the current point. Multiple clicks will bring up multiple copies of xraz, which is unnecessary.
5) When selecting a colormap file, the colormap MUST be in indexed form, or the colormap will fail.
6) The movie does not display in real-time; you must click the "movie" button to view the progress up to that point.
7) There are no heat/cold sources, aside from the boundary conditions.

HEAT-TRANSFER CONCEPTS

For more information on the process of heat-transfer, please see the paper: Numerical Simulations for Nonlinear Heat Transfer in a System of Multimaterials By: Wenlong Dai and Paul R. Woodward, Journal of Computational Physics, vol.139, pp.58-78, 1998.

BUG REPORTS

Please report bugs/comments/suggestions to: white@lcse.umn.edu wenlong@lcse.umn.edu

Heat-Transfer, version 0.9 Copyright 1998,ll Rights Reserved