A software system for immersed boundary and interface simulations

Availability and Requirements

WARNING: IBIS and this webpage are in the alpha development stage.

IBIS for Sun operating systems is available for download here.

The package is designed to run on SGI workstations that have OpenGL. For full functionality, IBIS requires the following freeware, which can be provided with the IBIS software package.

Example: Ciliated Tenticle

To produce a simulation similar to the cilliated tenticle simulation demonstrated on the IBIS index page, a user is required to write a short IBIS program the defines the initial conditions, properties of the fluid, and properties of the immersed boundary. The user is also required to write a short FORTRAN subroutine to specify the motion of the immersed boundaries.

The IBIS package contains a set of programs that are designed to make it simple to perform an immersed boundary simulation. Once the IBIS and FORTRAN programs have been written, to execute the software, the user is required to type only a few commands at the prompt.

With these short programs and instructions, IBIS will produce data to create this animation.

To analyze and visualize the data in more detail, IBIS includes a graphical user interface to study the details of the simulation called ibisview. This program allows one to see animations of the data, line plots that include velocities, immersed boundary positions, force fields, and scalar quantities like pressure fields.

Example: Aerosol transport in branched bronchi

lung simulation
IBIS is being used to study the flow and aerosol transport properties in a model of a segment of bronchial tissues. This simulation is part of a modeling effort to understand how high frequency ventilation works. This mixing is an important process in ventilation and drug delivery, but we have a only a poor understanding of how it is accomplished.

The IBIS file required to create this simulation uses polynomials to define the boundary of the bronchi, and reads particle positions from a user specified file. The first and second columns of this file define the initial positions of the particles, and the third number assigns the particles a color. The flow in this simulation was generated by a sinusoidally oscillating cone that is defined in a short FORTRAN subroutine.

With these short programs and instructions, IBIS will produce data to create the animation shown on the left. The animation continuously loops, and there is a five second delay between successive loops. Notice the preferential flow into the right branch, the mixing of the aerosol particles and the distance those particles travel.

Applications of the Immersed Boundary Method

IBIS Programming Language

The IBIS programming language is a tool that was designed to allow users to easily set the parameters that are needed for an immersed boundary simulation. These parameters include the domain, the initial positions of the immersed boundaries, the properties of the elastic links of the immersed boundaries, and the viscosity, density and initial fluid velocities.

The IBIS programming language has less than 50 key words, and each word has a small set of modifiers. Each of these key words specifies a unique property for the simulation.

The IBIS preprocessor interpretes the initial data, makes the numerical software, and graphically displays the initial positions of the immersed boundaries.

IBIS Numerical Software

The IBIS numerical software is written in FORTRAN. It takes the parameters set by the user, and calculates the evolution of the system. The IBIS package has been designed specifically to allow the user to avoid the internal working of the immersed boundary method, and the numerical software. For those problems that require forcing of all or part of the the immersed boundary, an interface to a user defined FORTRAN subroutine has been provided. In this interface, the immersed boundary and fluid data is passed to the user in a managable format, and can then be manipulated as needed.

IBISVIEW Visualization Interface

The IBIS graphics tool is called ibisview. The interface provides the user with point and click access to the data computed by IBIS. The data has two basic modes, color plots and line plots. The color plots are used to animate the simulations, and the line plots are used to study the data in more detail. With a point and click, ibisview can be used to see animations, to zoom-in to see detailed interface positioning and velocities, or to see the flow field on large or small scales.

IBIS Manual

The IBIS manual describes the software package, the IBIS programming language and the ibisview graphical interface.


This software is made available "as is" without any assurance that it will work for your purposes. The software may in fact have defects, so use the software at your own risk.