The diameter of a cylinder is the distance between two points on the cylinder’s surface that are farthest from each other and lie on a line passing through the center of the cylinder. In other words, the diameter is a straight line segment that passes through the center of the circular cross-section of the cylinder and touches the cylinder’s surface at two opposite points. For a perfect cylinder (one with perfectly parallel and congruent circular bases), the diameter is consistent across the entire length of the cylinder. It is often denoted as “D” and is used to describe the size and dimensions of the cylinder.
- d is the diameter of the cylinder.
- 𝜇∞ is the dynamic viscosity
- 𝜌∞ is the density of the fluid
- V∞ is the free-stream velocity of the fluid