
About Wave3000™
Wave3000™ is a standalone computer software program for computational
ultrasonics for problems that are 3D. It was produced to bring numerical simulation
to the ultrasound engineering community. This page provides some basic information
about Wave3000™ including a general Program Overview, Hardware/Software/Memory
Requirements, and a brief description of the Wave Equation that
is being simulated.
Program Overview
Wave3000™ is a standalone software package for computational ultrasonics.
It operates by solving the threedimensional (3D) viscoelastic wave equation
based on a method of finite differences. The solution is computationally intensive.
However, thanks to the ever increasing power and speed of computer hardware,
it is now possible to bring such software packages to the desktop and personal
computer of the ultrasound engineer and researcher.
Wave3000™ allows the user to compute the full viscoelastic wave solution
(both longitudinal and shear displacements) in an arbitrary threedimensional
(3D) object subjected to userspecified acoustic sources. The program, besides
simulating the complete spatial and timedependent acoustic solution, allows
the user to simulate ultrasound measurements in a variety of source and receiver
configurations. Wave3000™ will prove useful to researchers and applications
engineers in such diverse fields as nondestructive testing, materials evaluation,
geophysics, medical imaging and biological tissue characterization. The software
is useful also in basic mechanistic studies and for academic applications.
With Wave3000™ the user can compute solutions (e.g., scattered and reflected
waveforms) to virtually an unlimited variety of distinct physical problems
without ever leaving the computer keyboard.
Wave3000™ provides solutions to a broad range of 3D ultrasound problems.
The program allows the user to specify an arbitrary object which is ultrasonically
interrogated. The object is specified in several formats and is based on a
voxel representation of the object. Each voxel is associated with a specific
material through its value (in the range of 0 to 255). Note that for those
users already familiar with Wave2000® (our 2D ultrasound simulation software)
or Wave2500™(our 3Daxisymmetric ultrasound simulation software), the similarity
of the programs will be apparent in terms of many of the graphical user interfaces.
The 3D object to be simulated can be generated either internally using Wave3000™ "Geometry" routines
or externally from other programs (such as 3D images that may be obtained from
various scan modalities, for example CT or MRI slice data). Details for this
kind of data importing are found in the User Guide and Reference Manual in
the Help file.
The attractiveness of Wave3000™ is that it is very easy to generate
solutions to a wide variety of 3D ultrasound problems within a simple graphical
interface. The user has access to features designed to mimic reasonably closely
many practical situations. For example, there are source and receiver configurations
that the ultrasound engineer will notice are similar to real ultrasound experimental
configurations, for example the use of signals that characterize many standard
transducer generated waveforms. As one application, Wave3000™ may be
useful for analyzing ultrasound propagation in fluid saturated porous solids,
to explore the relationship between porosity and velocity, for example.
Wave3000™ has the potential to generate new insights and approaches
to many problems in ultrasonics. For the first time, the user has the capability
to "experiment" to his or her heart's content, without turning on a pulserreceiver
or connecting a "BNC" cable. Indeed, the simulations can "run" while the user
is word processing a document or analyzing data from an earlier simulation.
The computer can work "around the clock" (for example, by using the "Multibatch
feature") computing solutions to problems that are difficult to perform in
the laboratory or the field, but the results of the simulations can provide
important understanding and knowledge for future experiments or for data already
collected.
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Hardware, Software and Memory Requirements
Wave3000™ is designed to run on any PC that has the Windows XP, Vista, 7 or 8 operating systems installed. Minimum hardware requirements
are extremely modest (for example 15 megabytes free hard disk space and 128
megabytes memory), although we recommend 1 GB or more memory for handling the
larger simulation models. (Detailed information on memory requirements can
be found in the 'Algorithm' topic of the Wave3000® User Guide
Section of the Help file.) Minimum graphics requirements are 256 color VGA
and a compatible mouse, but of course most systems will have hardware characteristics
much higher than these minimums. As noted, Wave3000® operates best
with as much RAM memory as possible, which allows problems of increasingly
larger size to be accommodated and avoids the need for virtual (disk) memory
to be used. Note also that Wave3000® supports multiprocessor systems,
that allows the program to potentially speedup the execution of the program.
This is most effective for "large" objects; experimentation by the user will
determine when multiprocessors can lead to faster execution times. The multiprocessors
can be either actual multiproccessor systems, or multicore processors, or both.
Wave3000™ is a "memoryhungry" program; this is simply the nature of
the wave propagation problem which is being simulated. To aid the user in assessing
the memory requirements for a particular simulation model, we can provide the
following approximate relationships.
Because of the general nature of the 3D object, the memory requirements must
be computed based on the 3D dimensions. The simplest approach for approximating
memory needed is to multiply the number of finite difference grid voxels, say
N, by 42; this is the amount of memory required in bytes (plus some additional "fixed" program
overhead which can usually be neglected in comparison to the 42 x N quantity).
As an example, if an object is 2 cm x 3 cm x 4 cm and the voxel resolution
("Voxels/mm") is 10 voxels/mm, the number of voxels in this image will be 200
x 300 x 400 = 24,000,000 voxels. Now if we assume that the finite difference
grid elements generated by Wave3000™ are coincident with the number of image
voxels (i.e., Grid/Voxle = 1), then the memory required is 42 x N = 42 x 24,000,000
= 960 megabytes.
Another perspective on memory requirements can be gained by determining the
memory needed as a function of object size in terms of wavelengths. In the
example above, it was assumed that the grid size was coincident with object
voxel size, i.e., both were 0.1 mm (10 voxels/mm). For the case of a problem
in which the minimum wavelength is about 1 mm, this 0.1 mm size for the finite
difference grid element should provide a reasonably accurate solution. We may
extend this reasoning for a more generic assessment of memory requirements
as follows. Assuming that we would like to have a grid voxel element dimension
10 times less than the minimum wavelength, then that implies that 1,000 x 42
= 42,000 bytes for a cubic object 1 wavelength on a side. If one has a cubic
object which is 3 wavelengths on a side, then using the same relative grid
dimensions, Wave3000 would require about 1.1 MB of memory. One may also extend
this approximation to any number of (minimum) wavelengths to evaluate memory
requirements. Assuming a cuboid object Q wavelengths by R wavelengths by S
wavelengths in overall dimensions, and again assuming 10 grid elements per
wavelength, then the memory required for this model is approximately 42 x 10,000
x Q x R x S = 42 x Q x R x S kilobytes. It is useful to also point out that
the minimum wavelength is inversely proportional to the frequency of the source
waveform. Therefore, if a simulation with a 1 MHz source waveform requires
1 megabyte of memory, then changing to a source waveform operating at 2 MHz
will generally require eight times as much memory, or in this case 8 megabytes,
to be used. (This assumes of course that the same size object is used in both
cases.) Thus the user may want to carry out as many of his or her simulations
as possible with relatively low frequency sources, in order to reduce computational
overhead. It is important to point out that there may be instances where the
original object geometry has structural features (voxel sizes) smaller than
a grid size based on wavelength considerations alone; in this case the user
may need to manually reduce the grid size in order to maintain the structural
details present in the original image. If this is done, the memory requirements
will be larger than the calculations made in the above paragraph, and the user
should use the first expression, namely 42 x N, to evaluate the memory needed.
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Wave Equation
The specific viscoelastic wave equation that is simulated in a Wave3000™ simulation
is given by:
In the above equation, which applies in an isotropic elastic region,
ρ = material density [kg/m^3],
λ = first Lame constant [N/m^2],
μ = second Lame constant [N/m^2],
η = shear viscosity [Ns/m^2],
φ = bulk viscosity [Ns/m^2],
∇ = the gradient operator,
∇ • = the divergence operator,
∂ denotes the partial differential operator,
t = time [s],
and
w(x,y,z,t) is a threedimensional column vector whose components are the x, y and z components of displacement of the medium at location (x,y,z), that is
w = [wx(x,y,z,t) wy(x,y,z,t) wz(x,y,z,t]'
where ' denotes matrix transpose. Wave3000 solves the above equation within each homogenous cubic grid element of the object, and computes the displacement (longitudinal and shear) vectors at the intersection of each and every cubic grid element at each time step of the simulation. As noted above, the simulation explicitly satisfies the stress and displacement boundary conditions across each grid element of the simulation model. Additional information on the acoustic wave equation including the viscous loss component (i.e., the viscosity tensor) can be found in the excellent book by B. A. Auld entitled Acoustic Fields and Waves in Solids, Vols. 12, 2nd Edition, Krieger Publishing Company, Malabar, Florida, 1990.
Wave3000™ does not implement "raytracing" or other "nongeneral" methods
in simulating ultrasound measurements. Rather, it is a comprehensive engineering
software package designed to compute the full and accurate solution to
practically any 3D ultrasonic problem. Wave3000™ simulates data that
you would measure on the lab bench or in the field. In addition, it has an
easy to use graphical user interface allowing you to begin simulating complex
ultrasound problems in a matter of minutes after installing your Wave3000™ software.
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For features available in Wave3000™, you can look at Wave3000 page. For additional information, you may want to review several of our Wave3000
Examples. In addition you can download the program and obtain a free
timelimited license for program evaluation by registering
with us and logging in. Information on pricing is
also available. Please Contact Us to discuss your
intended application(s) or for any other additional information you would
like to have on Wave3000™.
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