US 12,270,424 B2
Staggered periodic riblets
Brian R. Smith, Colleyville, TX (US); Patrick J. Yagle, Fort Worth, TX (US); and Paul Douglas McClure, Fort Worth, TX (US)
Assigned to Lockheed Martin Corporation, Bethesda, MD (US)
Filed by Lockheed Martin Corporation, Bethesda, MD (US)
Filed on Aug. 21, 2019, as Appl. No. 16/547,378.
Prior Publication US 2021/0231141 A1, Jul. 29, 2021
Int. Cl. F15D 1/00 (2006.01); B64C 21/10 (2006.01)
CPC F15D 1/004 (2013.01) [B64C 21/10 (2013.01); B64C 2230/26 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A method for reducing drag, comprising:
forming first periodic riblets on a smooth surface of a physical object:
forming second periodic riblets on the smooth surface of the physical object; and generating a flow over the first and second periodic riblets of the physical object:
wherein:
each first periodic riblet comprises a first transition region at a first end of each first periodic riblet and a second transition region at a second end of each first periodic riblet:
each second periodic riblet comprises a first transition region at a first end of each second periodic riblet and a second transition region at a second end of each second periodic riblet:
each second transition region at the second end of each first periodic riblet overlaps each first transition region at the first end of each second periodic riblet:
a length of each riblet of the first and second periodic riblets runs parallel to a direction of the flow:
a maximum height of each riblet of first and second periodic riblets is less than 0.002 inches:
a maximum width of each riblet of the first and second periodic riblets is less than 0.004 inches;
the length of each first and second riblet that runs parallel to the direction of flow is within a range of 8 to 100 times longer than the maximum height of each respective riblet; and
generating a constant cross-sectional area through the first and second periodic riblets as measured above the smooth surface of the physical object by compensating a decreasing volume of a trailing edge of the first and second periodic riblets with an increasing volume of the neighboring first and second periodic riblets.