Quick Start Tutorial
In this page, a brief introduction to Wave2000 is given that allows you to begin simulating ultrasound problems as quickly as possible. All the basic components are described, albeit briefly, which form the basis for all simulations, and thus this page provides a useful introduction to the program as a whole. Please note: the same steps can be used for Wave2500 and Wave3000 as well.
From the desktop, double click on the Wave2000 icon to start the Wave2000 program. In all instances, the program name is Wave2000.exe. If the programs display the message "You need administrator privileges to run the program", please make sure you login as an administrator and you must run the software as administrator as well.To run the software as administrator in Windows, right click on the program shortcut, e.g., Wave2000, click Compatibility tab, then check the checkbox: Run this program as an administrator, and click Apply. Once run, the Wave2000 program will display a window called "Untitled1." You may want to expand this window for more convenient viewing by clicking on the "maximize icon" associated with the "Untitled1" window.
1. Object Definition
The first part of any Wave2000 simulation is to define an object to be ultrasonically interrogated. To do this, open the Wave menu on the main menu bar, and click on Geometry. On the Geometry sub-menu, select Create Image. In the Create Image window, enter a size (in millimeters) for the dimensions of a rectangular object; a reasonable choice to start with is 20 mm for "Width" (the dimension that goes from left to right on the screen, also described as an "x" coordinate) and 15 mm for "Height" (the dimension that goes from top to bottom on the screen, also described as a "y" coordinate). Notice that the "pixels per mm" setting is set to10. Leave this value as is and also leave the "Gray Level" setting at "0" for now and select "OK." The image is defined and appears as a rectangular homogeneous gray level (monotone) image, whose gray level is equal to zero.
The above rectangular image can itself serve as a medium to demonstrate basic ultrasonic simulation with Wave2000. However, to make the problem a bit more interesting, let us insert a small circular void in the center of the rectangle. To do this, click again on Geometry menu, but this time select Add Ellipse on the Geometry sub-menu. On the Add Ellipse window, enter 10 mm for the x coordinate and 7.5 mm for the y coordinate, which corresponds to the center of the ellipse; this puts the ellipse in the center of the 20 mm x 15 mm rectangle. In the "Major Axis" and "Minor Axis", enter 1 mm and 1 mm, respectively; this defines a circle 2 mm in diameter. Finally, leave "Theta" as is (at 0 degrees), enter 255 in "Gray Level," and click on "OK." At the "Image Will Be Changed, Continue?" prompt click on "OK." A 2 mm diameter circle with gray level set to 255 appears in the center of the rectangle.
Once again, click on the Wave menu, then Geometry, and then Save Geometry. In the "File name" box, enter a name of your choice to save this file in the default "Data" folder, and then click "Save." Note that the file name you are choosing to save this image in is assumed to have a ".pcx" filename extension; thus, you may enter only the first part of the filename, e.g., "circle1" and it will be saved as "circle1.pcx." You will also note that after saving the geometry file that the "Untitled" label is still showing in the two window title bars; this is correct and will only change when the File menu Save or Save As commands are used, as described below.
2. Material Definition
The next step is to define the material properties to be used in the Wave2000 simulation. To do this, click on the Wave menu, and select Material Property. You will note that there is no information in the white data boxes on the Material Properties page. This is because no material properties have been loaded into the program yet. The material properties may be loaded through use of a library file; to do this click on "Library" and on the Material Library page click on the select column for the third material on the list (in this case Aluminum) and note that a "check mark" appears in the box next to "Aluminum." Now click on "Add to Model" at the bottom of the page (note that the "check mark" will disappear once the Add to Model button has been clicked) and then click on "OK." You have now loaded the material parameter values for Plexiglas which were stored in the Library File (named "standard.mpd") into the Wave2000 program model. These material parameter values appear on the Material Properties page under the heading "Material No.: 1." Now change the "Gray Level" setting on this page to "0", click on "Apply" and then "OK." This will close the Material Properties" page and bring you back to the main screen where the object is now displayed in pseudocolor with a matching legend showing "Aluminum." The white circle in the center of the Aluminum denotes a void region (gray level 255 is reserved for void or vacuum regions). We have now completed the material definition portion of the Wave2000 simulation process.
3. Boundary Condition
In this example, no boundary condition is used. To setup boundary condition, go to the Wave menu and select Boundary Condition. The "Boundary Condition" page appears. Click on "Add" to define a new boundary condition; the empty text box at the top of the page becomes "New." Change the name to anything else, say for example, "BC1." There are two main options with respect to specification of a particular boundary condition (besides the location of the boundary condition); they are "Longitudinal Mode Fixed" and "Shear Mode Fixed." Selection of the former constrains the longitudinal motion of the object to zero at the boundary condition edge or line; selection of the latter constrains the transverse motion of the object to zero at the boundary condition edge or line. Wave2000 allows the user to set either boundary condition constraint alone or both constraints simultaneously.
Another option that can be used in the setup of boundary conditions are "infinite boundary conditions," denoted on the Boundary Condition page as "Infinite BC." Clicking on this button brings up an Infinite Boundary Condition page. This page includes four (4) check boxes that allow an infinite boundary condition to be simulated on any number of the sides of the object. Note that an infinite boundary condition overrides regular boundary condition on that side. Infinite boundary condition on any particular side attempts to make the boundary appear as an infinite medium matched to the material just inside the boundary of the object. This infinite boundary condition is also often referred to an "absorbing boundary condition," but we feel the term infinite boundary condition is somewhat more appropriate.
4. Source Definition
To generate an acoustic wave, an ultrasound source must be defined. To do this, go again to the Wave menu and select Source Configuration. The "Source Configuration" page appears. Click on "Add" to define a new source; the empty text box at the top of the page becomes "New." Change the name to anything else, say for example, "Source1." Now in "Location" select "Left" and in "Size" enter 3 mm. Leave "Center Offset" at zero. Now look at the "Signal Parameters" section in the lower half of the page. You will observe that the "Longitudinal Mode" checkbox is "checked" and that "Sine Pulse" text appears in the "Time Function" text box adjacent to it. If these two items are not selected as described here, then click on the Longitudinal Mode checkbox and select "Sine Pulse" in the "Time Function" box from the drag-down menu list of time functions. You will also note that the "Shear Mode" checkbox is unchecked (and that "Sine Pulse" text appears in the "Time Function" text box adjacent to it); leave both of these items as they are. Now click on "Detail;" a "Time Function Configuration page appears. Enter a "2" in the "Duration (us)" text box and then click "Preview" to view a 1 MHz sine wave of unit amplitude "on" for 2 microseconds. Click on "OK" to exit the Time Function Configuration page and return to the Source Configuration page. Finally, click on "Apply" and "OK;" you have now defined for the simulation a 2 microsecond pulsed 1 MHz sine wave source 3 mm in length, which is located at the center of the left edge of the object.
5. Receiver Definition
At this point, the Wave2000 simulation could begin, but in order to demonstrate some further features of the program, we will proceed with specification of a receiver. To do this, click on the Wave menu, and select Receiver Configuration which brings up the Receiver Configuration page. Click on "Add" to define a new receiver; the empty text box at the top of the page becomes "New." Change the name to anything else, say for example, "Receiver1." Now in "Location" select "Right" and in "Size" enter 3 mm. Leave "Center Offset" at zero. You will notice that both the "Longitudinal Mode" and "Shear Mode" boxes are checked in the "Output Parameters" section indicating that the receiver will measure both longitudinal and shear (transverse) displacements at the specified location at the surface of the object. Click on "Apply" and "OK" to complete the specification of the ultrasound receiver.
6. Job Parameters
A part of any simulation is the setting of various parameters which will affect the performance of the simulation, in terms of accuracy, stability and other aspects as well. In Wave2000, this is done through a Job Parameters page. To access it, click again on the Wave menu, and select Job Parameters. A screen will appear with a list of items. For now, we will be concerned with only a few of them. Change "Resolving Wavelength (mm)" to "2", "Simulation Time (us)" to "6" and "Display Frequency" to "5". Then click on "OK."
7. Check and Save Model
Before running the simulation, it is often useful to check various details about the model. In Wave2000, this is done by accessing the Check Model or "Model Data" page. To do this, click on the Wave menu, and select Check Model. The "Model Data" page appears, detailing various aspects of the simulation model.This page provides, for example, the size in the x and y directions of the finite difference grid element, the size and number of time steps, and warnings or an error message related to the possibility of "rigid body motion" and/or memory related problems. After reviewing this data (see the User's Guide and Reference Manual for additional details on the parameters contained in the "Model Data" page), click on "OK." Finally, it is usually a good idea to save the entire model before proceeding to the next step. To do this, click on the File menu, select Save as... and at the file name text box, enter a name of your choice. You can enter the same name as you entered for the geometry file, as the extension used previously was ".pcx" and the extension used here will be ".wmd." After clicking "Save" the file is saved in the default "Data" folder, and you will notice that the filename appears now in the Windows' title bars.
8. Running the Simulation
The last step (aside from any subsequent analysis and modifications to the model) is the actual execution of the Wave2000simulation. This is the simplest part of the entire simulation procedure. To do this, click on the Wave menu, and select Run. A warning on "rigid body motion" will appear; click "OK" and the simulation begins! On the screen will be the object itself within which appears the propagating ultrasonic wave, a receiver plot corresponding to the defined receiver, and a "Process Monitor" window which provides information on the evolved time as well as controls to "Pause," "Next" and "Stop" the simulation. Try clicking on "Pause;" you will note that the "Pause" button has changed to "Run." After the simulation pauses, resume the simulation by clicking on "Run." When the "Run" button is clicked, a "Run to step" box appears that allows the user to select the step to which the simulation should run. Click on the "OK" button to make the simulation continue. The Receiver Plot and Process Monitor Windows can be moved (the Receiver Plot Window can also be resized or closed) using the mouse in order to better view the object and the ultrasound waves propagating within it. The program should continue simulating the process for the duration of time chosen earlier, in this case 6 us, after which it will stop and be ready for further operations.
Congratulations, you have just completed a Wave2000 simulation!