# Why are there no coefficients of drag for cubes and cones of low Reynolds numbers

I am currently reading ''Fluid Mechanics-Fundamentals and Applications'' by Yunus A.Cengel and John M.Cimbala.

I am currently reading about drag coefficients in chapter 11 and how it talks about the drag coefficient being inversely proportional to the Reynolds number when the Reynolds number is <1. So for a sphere it show that $$C_d=\frac{24}{Re}$$, which I gather from the experimental observation and linear region of the graph of drag coefficient plotted against Reynolds number.

The book also outline several other coefficient of drags for a semi-sphere and a flat circle disc where are respectively $$C_d=\frac{22.2}{Re}$$ and $$C_d=\frac{20.4}{Re}$$(fluid flow against the flat side of the plate).

My question is tho, why is there no coefficients of drags for a cube or a cone? I have searched google for any experimental evidence and have come up with nothing. Yet there seem to be coefficients of drag for these geometries for high Reynolds numbers.

Is is easier to obtain the coefficients of drag for the geometries with higher Reynolds number or is it just that know one has ever carried out the experiment?

Would it be possible to compare a ratio of surface areas of a cone to a sphere to my a eligible assumption on the coefficient of drag for say a cone, if the cone has the same size diameter as a sphere? Like a proportionality constant so to speak.

• – Alex Trounev Feb 5 '19 at 18:24