file

NAME

file

SYNOPSIS

          file filename [-options]

DESCRIPTION

file reads a data file that contains immersed boundary points, possibly their tether points, and possibly their link properties. This command allows IBIS to import immersed boundary data from other sources.

file requires one argument, filename, the name of the file that holds the data.

file interpretes the optional arguments:

• -A name - indicates this entity is active and provides a name
• -a angle - resting angle at the IB points
• -b bend - bending stiffness at the IB points
• -N name - provides a name for the entity
• -s stiff - inter IB point spring stiffness
• -t tether - tether spring stiffness

FILE REQUIREMENTS

The file holding the data may be in any of four file formats. The action of the preprocessor depends on which format is provided. The primary difference between the file formats is in the number of columns that the data file contains.

For all four formats, the first line of the file must contain two integers. The first integer specifies the number of columns in the file, and the second integer specifies the number of immersed boundary points in the file.

Denote the number of immersed boundary points by N.

Two column format:

In the simplest file format, the file contains exactly N+1 rows and two columns. The first row reads

          2    N

The remaining N rows hold the x and y coordinates of the immersed boundary points. These rows read

          x    y

The coordinates must be floating point numbers, but there is no restriction on their precise format.

If this format is employed, IBIS assumes that the tether points associated with each immersed boundary point are located at the same position as the immersed boundary point. The resting angle and resting length are computed so that the rest position is identical to the initial position, and the stiffnesses are assigned from the stiffness specified either with the [-options] or with spring.

Four column format:

In the next simplest file format, the file contains exactly N+1 rows. The first row reads

          4    N

The remaining N rows hold four floating point numbers, the x and y coordinates of the immersed boundary points, and the xt and yt coordinates of the tether points. These rows read

          x    y   xt   yt

The coordinates must be floating point numbers, but there is no restriction on their precise format.

If this format is employed, IBIS computes the resting angles and lengths so that the rest position is identical to the tether positions. The stiffnesses are assigned from the stiffness specified either with the [-options] or with spring.

Nine column format:

This file contains exactly N+1 rows. The first row reads

          9    N

The remaining N rows hold nine floating point numbers, forming a N by 9 array of numbers. These 9 columns individually contain (in this order);

1.

x - the x coordinate of the immersed boundary point.

2.

y - the y coordinate of the immersed boundary point.

3.

xt - the x coordinate of the tether point.

4.

yt - the y coordinate of the tether point.

5.

rest - the resting length between the current immersed boundary point and the next immersed boundary point.

6.

stiff - the stiffness of the link between the current point and the next point.

7.

theta - the resting angle formed between the previous, current and next points.

8.

bend - the bending stiffness between the previous, current and next points.

9.

teth - the link stiffness of the tether link.

The order must be

          x    y   xt   yt rest stiff theta bend teth

The coordinates must be floating point numbers, but there is no restriction on their precise format.

If this format is employed, IBIS reads and uses the data specified. The stiffnesses are assigned from the file directly, and they superscede any link attributes specified with the [-options] or with spring.

Ten column format:

This file contains exactly N+1 rows. The first row reads

          10    N

The remaining N rows holds one integer in the first column and nine floating point numbers in columns two through ten. The nine floating point numbers are identical to the nine floating point numbers defined for the nine column format. The only exception here is that they are each shifted to the right by one column. The integer contained in the first column can be arbitrary.

This format is included because it is the output format of the preprocessor file ibisdat/ibpts.dat. Therefore one could easily edit that file, (for example to change a few specific link attributes or move a few immersed boundary points) and reinsert that file into the preprocessor. This would preserve the hand editing of the file.

If this format is employed, IBIS reads and uses the data specified. The stiffnesses are assigned from the file directly, and they supercede any link attributes specified with the [-options] or with spring.

SEE ALSO

pfile, spring