US 12,085,102 B2
Submerged periodic riblets
Brian R. Smith, Colleyville, TX (US); Patrick James 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. 16/547,304.
Prior Publication US 2021/0231142 A1, Jul. 29, 2021
Int. Cl. F15D 1/00 (2006.01); B64C 21/10 (2006.01); F03D 80/00 (2016.01); F15D 1/12 (2006.01); B62D 35/00 (2006.01); B63B 1/34 (2006.01); F42B 10/42 (2006.01)
CPC F15D 1/004 (2013.01) [B64C 21/10 (2013.01); F15D 1/12 (2013.01); B62D 35/00 (2013.01); B63B 1/34 (2013.01); B64C 2230/26 (2013.01); F03D 80/00 (2016.05); F42B 10/42 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A method for reducing drag, comprising:
forming a smooth surface on a first portion of a physical object, wherein:
the first portion of the physical object further comprises a transition surface; and
an angle between the transition surface of the first portion of the physical object and the smooth surface of the first portion of the physical object is within a range of 90 degrees to 179 degrees;
forming periodic riblets on a second portion of the physical object, wherein:
the second portion of the physical object is adjacent to the first portion of the physical object;
each riblet of the periodic riblets of the second portion of the physical object is depressed below a plane of the smooth surface of the first portion of the physical object; wherein, each riblet of the periodic riblets:
terminates in a first direction at the transition surface of the first portion of the physical object;
has a same length;
is equal in length to the smooth surface of the first portion of the physical object and is within a range of 10 to 50 times longer than a maximum height of each respective riblet;
has a maximum height less than 0.002 inches;
has a maximum width less than 0.004 inches; and
runs parallel to a flow direction;
each peak of each riblet of the periodic riblets is at a level below the plane of the smooth surface of the first portion of the physical object wherein:
a distance between each peak of each riblet of the periodic riblets is constant;
each peak of each riblet of the periodic riblets forms a 90 degree angle; and
each valley between adjacent riblets of the periodic riblets forms a 90 degree angle;
forming a smooth surface on a third portion of the physical object, wherein:
the third portion of the physical object further comprises a transition surface;
each riblet of the periodic riblets span from the first portion of the physical object to the third portion of the physical object; and
each riblet of the periodic riblets terminates in a second direction opposite the first direction at the transition surface of the third portion of the physical object;
generating a flow over the periodic riblets of the second portion of the physical object and over the smooth surface of the first portion of the physical object, wherein a length of each riblet of the periodic riblets runs parallel to a direction of the flow.