1. Explain why pipe diameter rather than pipe length is the proper characteristic scale for Reynolds number in a pipe.
2. You have a block of steel 10cm x 10cm x 4cm. You drill 81 holes through the 4cm dimension of the block. The holes are on a 9x9 square grid with 1 cm spacing. The diameter of each hole is 1mm.
a- Determine the porosity and permeability of the block.
b- In a second block, you drill a single larger-diameter hole, so that the porosity is the same as your first block. What is the diameter of the hole? What is the permeability of the second block?