% Schematic38.m %
clear all; clc; close all;
nt= 160; t = linspace(-3*pi,3*pi,nt); nx = nt;
x = linspace(1,nx+1,nx+1); h = x(2) - x(1); 
[xx yy] = meshgrid(t,t); b = atan2(yy,xx);
z = (0.9+0.1*b.*cos(2.5*b)).*xx.^2+(1.5+0.3*b.*cos(4.2*b)).*yy.^2-60; 
hold on; sh = 16;
[c1, hh1] = contourf(1-z,[0. 0. 0.]);
set(hh1,'linecolor','k','linew',1.5); colormap([0.85 0.85 0.85])
text('Interpreter','latex', 'String','$$\Omega_t$$',...
    'position',[72.294 41.224 1131.415],'FontSize',30)
text('Interpreter','latex', 'String','$$\rho({\bf x},t)$$',...
    'position',[63.294 98.959 1131.415],'FontSize',30)
text('Interpreter','latex', 'String','$${\bf u}({\bf x},t)$$',...
    'position',[63.294 78.838 1131.415],'FontSize',30)
[c, hh] = contour(z,[0 0 0]); set(hh,'linecolor','k','linew',1.5)
axis image; axis([x(1) x(nx+1) x(1) x(nx+1)]); axis off;
set(gcf,'paperpositionmode','auto')