CFD Online Discussion Forums - How to Create a Multiple Point Vortice Vector Field

I want to create a vector field with multiple point vortices in a checkerboard arrangement with alternating rotational directions. I have written a code in python to create a single point vortex in the middle of my grid (see below) but would like to know how to go about creating this multiple point vector field.

Code:

  from math import *

from pylab import *

# Set limits and number of points in grid

xmax = 10

xmin = -xmax

NX = 30

ymax = 10

ymin = -ymax

NY = 30

# Make grid and calculate vector components

x1 = linspace(xmin, xmax, NX)

y1 = linspace(ymin, ymax, NY)

X1, Y1 = meshgrid(x1, y1)

S21 = -(X1)**2 - (Y1)**2 # This is the radius squared

Bx1 = -Y1/S21

By1 = +X1/S21

figure()

QP = quiver(X1,Y1,Bx1,By1)

quiverkey(QP, 0.85, 1.05, 1.0, '1 mT', labelpos='N')

# Set the left, right, bottom, top limits of axes

dx = (xmax - xmin)/(NX-1)

dy = (ymax - ymin)/(NY-1)

axis([xmin-dx, xmax+dx, ymin-dy, ymax+dy])

show()

end

Thanks in advance!