the meaning of "lumped" in "lumped drag coefficient"

Question

I'm facing problem with the meaning of this word lumped in a scientific context. For example, lumped drag coefficient. I've looked at its definition in Longman Dictionary, Oxford Dictionary and Dictionary.com but I couldn't understand its meaning. I'm not asking about its meaning from physics perspective, I'm asking about its meaning for English speakers who are not physicists. What do they understand? I know what drag and coefficient mean but with lumped, I'm not able to picture its meaning. Any suggestions

Answer 1

The definition given in Oxford Dictionary ("Put in an indiscriminate mass or group") is good.

In real life, a body is not a particle. A body will have many parts and each part will have its own drag coefficient. Imagine a cyclist riding his bike at a relatively high speed. The total drag will be the result of the drag from all parts combined. Thus, the term "lumped".

Your lumped drag coefficient is, of course, a drag coefficient. It's just that we think of all parts "lumped" together.

Answer 2

The word lumped derives from the verb to lump = "To treat as a single unit; to group together."

Imagine that there are several drag forces acting on the object, and possibly some other factors affecting the drag (such as "air density", as Jason Patterson says in the comments).

To make calculations simple, the scientists unite these forces and factors into a single coefficient. They "lump" these forces and factors, make them into a "lump", an agglomerate.