[x,y,z,v] = flow;
figure(1)
subplot(2,1,1)
p1 = patch(isosurface(x,y,z,v,0.5));
p2 = patch(isosurface(x,y,z,v,-0.5));
set(p1,'FaceColor','red');
set(p2,'FaceColor','yellow');
daspect([1,4,4])
view([-65,20])
axis tight
camlight left; 
set(gcf,'Renderer','zbuffer'); 
lighting phong

subplot(2,1,2)
colormap([0 0 0])
contourslice(x,y,z,v,[0.5],[],[],[-2:0.25:1])
daspect([1,4,4])
view([-90,0])
axis tight













