%circsource
%Circle source initial condition for angular spectrum code
%
%Call asprop.m after running this script

%Written by Robin Cleveland, Boston University
%ME720, Acoustics 2

clear all    %clear all variables
close all    %close all figure windows

%%%%%%%%%%%
%USER INPUT
%%%%%%%%%%%

%Physical parameters for source
f=2e6;     %frequency
a=1.5e-3;    %radius
c0=1500;   %sound speed

%Attenuation
alpha=2.5e-14*f.^2;  %water
alpha=0;

%Grid Size
lenx=512;
xmax=15*a;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%CALCULATIONS START FOR SOURCE CONDITION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%Rayleigh distance and wavenumber
k=2*pi*f/c0;
ka=k*a
zrayl=0.5*ka*a

%x and y spatial vectors
xvec=linspace(-xmax,xmax,lenx)';
yvec=xvec';
leny=length(yvec);

%Create spatial array with source velocity condition
rsq=(xvec.*xvec)*ones(size(yvec))+ones(size(xvec))*(yvec.*yvec); %distance from origin squared

Usxy=double(rsq<=(a*a));   %Usxy is unity for all points with radius less than a

%Plot source condition
figure(1);
imagesc(abs(Usxy));
title('Velocity Source Condition');