• # question_answer A pipe friction test shows that, over the range of speeds used for the test, the non-dimensional friction factor $'f'$ varies inversely with Reynolds Number. From this, one can conclude that the: A) Fluid must be compressibleB) Fluid must be idealC) Pipe must be smoothD) Flow must be laminar

If $f\,\alpha \,\frac{1}{\operatorname{Re}},$ then the pipe must be smooth.