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Delft3D computations can be post processed by utilizing Quickplot. More freedom is earned by loading the raw data into MatLAB. This can be done by using OpenEarth tools. Besides a MatLAB based GUI post processing program, Muppet, is developed. 

OpenEarth tools

One of the possible output files are the trim (map) files. Maps are snap shots of the computed quantities of the entire area.  In OpenEarth tools some functions are available which enable you to extract data from the map files. 

1. Make a file handle:    

Matlab function: N = vs_use(‘d:\test\trim-test.dat’)

2. Display the stored quantities:  

Matlab function: vs_disp(N)

A list of all the stored quantities is displayed in the command window. The map file is divided in different groups. Each group consists of different quantities. The number of groups depends on the type of simulation. Examples of some groups and their quantities is given below:

  • ‘map-const’: All the quantities which remain constant during the simulation are placed in this group, like: 
    • XZ: The X-coordinate of the cell centres
    • GSQS: The surface of each grid cell
  • ‘map-series’: All the hydrodynamic quantities that vary over time, like:
    • S1: Water level at each grid cell centre
    • U1: U velocity in U-point
  • Etc.

3. Extract specific data from the map file (in this example water level data):

Matlab function: WL = vs_get(N,'map-series',{timestep},'S1',{n_range m_range},'quiet')

If you want to extract the water level data for all grid cells at timestep 10 to 15, timestep should be 10:15 and m_range and n_range should both be 0.

Analyzing bar patterns

To analyze bar patterns one can use Fourier Transforms. The basic idea behind Fourier Transforms is that any function can be represented by a summation of sine and cosine functions, with different resolution. By using Fourier Transforms, one can derive the power spectrum of the pattern, which tells you the main harmonics and their contribution.

MATLAB can be used to do this operation. If you have for example a matrix ‘SED’ with sedimenatation/erosion data you can do the transform with the following code (note that you probably have to change the dx, dy, n and m for you own application):

dx = 0.1;   %grid size in x-direction
dy = 0.03; %grid size in y-direction
n = 512;    %The resolution in x-direction is divided in m bins
m = 512;    %The resolution in y-direction is divided in m bins
Trans = fft2(SED,m,n);                    
Power = Trans.*conj(Trans)/(m*n); 
Resolution_x = (0:n-1)./(n*dx);
Resolution_y = (0:m-1)./(m*dy);
Surf(Resolution_x, Resolution_y, Power,'LineStyle','none');
xlabel('Resolution in X-direction')
ylabel('Resolution in Y-direction')

An example of such a surface plot can be seen below. Each peak corresponds to a bar pattern with a certain resolution in x and y direction.

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