estimate wave fetch
function [dir,fetch] = calc_fetch(nodefile,botfile,xp,yp,zadd);
DESCRIPTION:
given a SWAN mesh and bathymetry and observation point, estimate fetch for
range of wind directions
INPUT
nodefile = SWAN unstructured node file
botfile = SWAN unstructure bathymetry file (positive down)
xp = observation point x-coordinate
yp = observation point y-coordinate
zadd = [optional] add free surface height to account for tides (m)
OUTPUT:
dir = direction of wind in Cartesian coordinates
fetch = fetch for that direction in (m)
Note: if dir=45, this will provide the fetch for a SW wind
EXAMPLE USAGE
[dir,fetch] = calc_fetch('skg4.3.node','skg4.3.bot',5.3870e5,5.3506e6,-2);
Author(s):
Geoff Cowles (University of Massachusetts Dartmouth)
Revision history
==============================================================================0001 function [dir,fetch] = calc_fetch(nodefile,botfile,xp,yp,zadd); 0002 % estimate wave fetch 0003 % 0004 % function [dir,fetch] = calc_fetch(nodefile,botfile,xp,yp,zadd); 0005 % 0006 % DESCRIPTION: 0007 % given a SWAN mesh and bathymetry and observation point, estimate fetch for 0008 % range of wind directions 0009 % 0010 % INPUT 0011 % nodefile = SWAN unstructured node file 0012 % botfile = SWAN unstructure bathymetry file (positive down) 0013 % xp = observation point x-coordinate 0014 % yp = observation point y-coordinate 0015 % zadd = [optional] add free surface height to account for tides (m) 0016 % 0017 % OUTPUT: 0018 % dir = direction of wind in Cartesian coordinates 0019 % fetch = fetch for that direction in (m) 0020 % 0021 % Note: if dir=45, this will provide the fetch for a SW wind 0022 % 0023 % EXAMPLE USAGE 0024 % [dir,fetch] = calc_fetch('skg4.3.node','skg4.3.bot',5.3870e5,5.3506e6,-2); 0025 % 0026 % Author(s): 0027 % Geoff Cowles (University of Massachusetts Dartmouth) 0028 % 0029 % Revision history 0030 % 0031 %============================================================================== 0032 0033 %clear all; close all; 0034 %nodefile = 'skg4.3.node'; 0035 %elefile = 'skg4.3.ele'; 0036 %botfile = 'skg4.3.bot'; 0037 %xp = 5.3870e+05; 0038 %yp = 5.3506e+06; 0039 %zeta_max = 2.5; 0040 %zeta_min = 2.5; 0041 0042 % set number of theta-bins 0043 nbins = 32; 0044 0045 delta_zeta = 0.0; 0046 if(exist('zadd')) 0047 delta_zeta = zadd; 0048 end; 0049 0050 % warning - program is terribly unrobust 0051 % to improve robustness, search along rays until the point is found 0052 % inside a boundary or dry triangle 0053 0054 % read the node file 0055 [cnt,x,y,nmark] = textread(nodefile,'%d %f %f %d\n','headerlines',1); 0056 0057 % read the depth file 0058 [h] = textread(botfile,'%f\n','headerlines',0); 0059 0060 % add/subtract free surface amplitude 0061 h = h + delta_zeta; 0062 0063 % mark all nodes that are solid wall, open boundary, or dry 0064 drynodes = find(h < 0); 0065 nmark(drynodes) = 3; 0066 solidpts = find(nmark > 0); 0067 xdry = x(solidpts); 0068 ydry = y(solidpts); 0069 0070 % distance vector from all solidpts to point of interest 0071 dist = sqrt( (xdry-xp).^2 + (ydry-yp).^2); 0072 ang = atan2( (ydry-yp), (xdry-xp) ); 0073 0074 0075 % find the wave direction corresponding to the angle between the boundary point and POI 0076 plot(dist.*cos(ang),dist.*sin(ang),'r+'); hold on; 0077 0078 % sort the points in order of increasing angle 0079 ang = ang + pi; %convert from obs-shore to shore-obs angle 0080 0081 % for each bin find the minimum distance 0082 dtheta = 2*pi/nbins; 0083 theta_bound = 0-dtheta/2:dtheta:2*pi+dtheta/2; 0084 theta = 0:dtheta:2*pi; 0085 mind = zeros(numel(theta),1); 0086 for i=1:numel(theta) 0087 pts = find( (theta_bound(i) < ang) & (ang <= theta_bound(i+1))); 0088 if(numel(pts) > 0) 0089 mind(i) = min(dist(pts)); 0090 end; 0091 end; 0092 0093 % make sure there are no zeros 0094 for i=2:numel(theta)-1 0095 if(mind(i) == 0.); mind(i) = max(mind(i-1),mind(i+1)); end; 0096 end; 0097 if(mind(1) == 0.); mind(1) = mind(2); end; 0098 if(mind(end) == 0.); mind(end) = mind(end-1); end; 0099 0100 % smooth to account for diffraction 0101 for i=2:numel(theta)-1 0102 mind(i) = .5*(mind(i) + max(mind(i-1),mind(i+1))); 0103 end; 0104 mind(1) = .5*(mind(1) + mind(2)); 0105 mind(end) = .5*(mind(end) + mind(end-1)); 0106 0107 % force periodicity 0108 mind(end) = mind(1); 0109 0110 plot(0,0,'g+','MarkerSize',5); hold on; 0111 plot(mind.*cos(theta+pi)',mind.*sin(theta+pi)'); 0112 0113 % plot a polar 0114 figure 0115 plot(theta*180/pi,mind); 0116 xlabel('wind direction (Cartesian sense)'); 0117 ylabel('fetch (m)'); 0118 0119 % set return values 0120 dir = theta*180/pi; 0121 fetch = mind; 0122 0123