Drawing contour lines on the edges of contour plots

Hi
I have drawn a velocity contour plot, but i cannot draw the contour lines which will make the edges of the contour more bold. I see there are contour iso lines but they are not getting placed exactly on the edges of the contour plots. What should i do?

Hi

Any comments on this please?

I’m guessing you’ll need to be more specific about your data and what you’re attempting to achieve.

Hi, thanks I have drawn the contour plots but i want to thicken the edges of the contour plot with black lines. Attched is the picture without thickening the edges


I want to make the edges more bold and more visible.