It is some dimension that we decide is an appropriate length for indicating the relevant size of whatever it is that we are dealing with.
We often use the diameters of pipes for internal flow and cylinders or spheres for external flow.
For wing-like things, we use the chord of the wing.
For a building, it might be the width of the building on the side facing the wind.
It is some dimension that we decide is an appropriate length for indicating the relevant size of whatever it is that we are dealing with.
We often use the diameters of pipes for internal flow and cylinders or spheres for external flow.
For wing-like things, we use the chord of the wing.
For a building, it might be the width of the building on the side facing the wind.