I don't understand. To make a X-Y grid, loop on X and loop on Y. To make a r-θ grid, loop on r and loop on θ.
Perhaps you want to make a rectangular grid within a circle?
About Techplot.Is this a question about Fortran or about Tecplot?
Yes thank you, I have the grid. Was facing problem in plotting it.FYI, in any language, if you let ##\theta## go from 0 to ##2\pi## then the points with cartesian coordinates ##x = r \cos(\theta), y = r \sin(\theta)## will be spaced around the circle of radius ##r##.