Cd of the cylinder at the limits of compressibility, according to Gowen &amp; Perkins (NACA TN 2960). The lower black curves draw the classical Cd of the cylinder versus its Reynolds (see the blue curve of [Comparison_Cx_sphere_and_cylinder.png] .The red curves show what happens to the Cd of the cylinder when, in order to increase the Reynolds, the flow velocity is increased beyond M 0.3: the flow feels the effects of compressibility of the air, which causes the Cd to grow vertiginously, thus increasing a little bit more the Reynolds, but it's especially the Cd that takes off!
<a href="//commons.wikimedia.org/wiki/User:Bernard_de_Go_Mars" title="User:Bernard de Go Mars">Bernard de Go Mars</a>
<span class="int-own-work" lang="en">Own work</span>