DIRECTION_ARROWS_SEQUENCE
Direction Field Arrow Sequence

DIRECTION_ARROWS_SEQUENCE is a MATLAB routine which makes velocity direction arrow plots using a single XY coordinate file, and a sequence of UV velocity datasets, stored as TABLE files (except that no "#" comment lines are allowed).

The program is mainly a preprocessor for MATLAB's quiver routine. It reads the (X,Y) coordinates of a set of points from an "XY" file, and the corresponding horizontal and vertical velocities from a "UV" file.

It then makes a few settings, computes the direction field from the velocity field, calls quiver to plot the arrows, and also traces out the convex hull of the points, which is presumably the boundary of the region. The resulting image is displayed, and saved to a PNG file.

In addition, the program assumes that the user actually has a sequence of UV datasets, with "consecutive" names, each of which is to be plotted. The program automatically reads each such dataset and creates the sequence of PNG files. It is easy to take such a sequence and make an animation.

Related Data and Programs:

DIRECTION_ARROWS is a MATLAB program which will display the direction field for a single set of UV data.

DIRECTION_ARROWS_GRID is a MATLAB program which reads files of node and velocity data, and, using interpolation, creates a velocity direction plot with arrows place on a uniform grid of the user's specification.

DIRECTION_ARROWS_SEQUENCE2 is a MATLAB program which handles the case where each data file contains both XY and UV values.

FREE_FEM_STOKES is a MATLAB program which computes the pressure and velocity for a Stokes flow. The velocity vectors can be plotted using DIRECTION_ARROWS.

TABLE is a format used for the input files to this program.

VECTOR_MAGNITUDE_GRID is a MATLAB program which reads node and velocity data from a file, and using an interpolating function, is able to display a contour plot of the vector magnitude field.

VECTOR_PLOT is a FORTRAN90 program which can read an XY file and a UV file and plot the velocity and velocity direction fields.

VELOCITY_ARROWS_GRID2 is a MATLAB program which reads a single file of node and velocity data, and using interpolation is able to display a velocity vector field along any uniform grid of points specified by the user.

VELOCITY_ARROWS_SEQUENCE is a MATLAB program which plots the velocity field.

Source Code:

• direction_arrows_sequence.m, the source code;
• file_exist.m, is true if a file exists;
• file_name_ext_swap.m, changes the extension on a file name;
• file_name_inc.m, increments a file name;

Examples and Tests:

INOUT models 2D flow in a box, with inlet at one side and outlet on the other. The following files are available:

• inout_xy.txt, the coordinatees of nodes.
• inout_uv001.txt, a set of velocity data.
• inout_uv002.txt, a set of velocity data.
• inout_uv003.txt, a set of velocity data.
• inout_uv004.txt, a set of velocity data.
• inout_uv005.txt, a set of velocity data.
• inout_uv006.txt, a set of velocity data.
• inout_uv007.txt, a set of velocity data.
• inout_uv008.txt, a set of velocity data.

The command

direction_arrows_sequence ( 'inout_xy.txt', 'inout_uv001.txt', 1.0 )

• inout_uv001.png, a plot of velocity direction data.
• inout_uv002.png, a plot of velocity direction data.
• inout_uv003.png, a plot of velocity direction data.
• inout_uv004.png, a plot of velocity direction data.
• inout_uv005.png, a plot of velocity direction data.
• inout_uv006.png, a plot of velocity direction data.
• inout_uv007.png, a plot of velocity direction data.
• inout_uv008.png, a plot of velocity direction data.

You can go up one level to the MATLAB source codes.