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I've come across the term "scrub drag" in several papers recently, but can't find a detailed definition of this phenomenon. This is specifically in reference to aircraft and seems to apply to engine positioning.

For example: "Coe observes that scrub drag in cruise could be reduced by pylon mounting the engine over the wing", from the first paper below.

The term is assumed to be known to the reader in the following papers:

A Computational Study of Engine Deflection Using a Circulation Control Wing

Conceptual Design of a Next Generation, 150 Passenger Commercial Transport

A Study on Aerodynamic Design Integration of the Supercritical Wing and Rear-Mounted Engine Configuration

The same term in the context of automotive design does not appear to apply.

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  • $\begingroup$ I'm gonna go with, drag that can't get no love from me. $\endgroup$ – Ryan Mortensen Apr 5 '19 at 4:22
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This paper seems to show it's drag caused by air disturbed by a front mounted propeller.

Page 9:

Single Pusher: This configuration reduces scrub drag as the aircraft operates in clean air. However, a motor mounted aft of the aircraft will operate in the wing/fuselage wake, which causes a decrease in propulsion efficiency.

https://www.aiaadbf.org/2016TopReports.aspx

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    $\begingroup$ That interpretation doesn't seem to match up with other statements, especially ones dealing with turbofan powered aircraft (no propellors), or with there being a difference in cruise mode as opposed to other modes of operation (engine position remains the same). It does seem to have something to do with turbulent flow. $\endgroup$ – rsbonini Mar 15 '19 at 13:15
  • $\begingroup$ It was the only reference I could find to scrub drag. $\endgroup$ – CrossRoads Mar 15 '19 at 14:39

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