A method for reducing drag, comprising: forming a smooth surface on a first portion of a physical object; forming periodic riblets on a second portion of the physical object; forming a smooth surface on a third portion of the physical object; and generating a flow over the periodic riblets of the second portion (1300 of the physical object and over the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; wherein: the second portion of the physical object is adjacent to and between the first and third portions (120, 140) of the physical object; each peak of each riblet of the periodic riblets of the second portion of the physical object is located above a plane of the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; each valley between adjacent riblets of the periodic riblets of the second portion of the physical object is located below the plane of the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; and a length of each riblet of the periodic riblets of the second portion runs parallel to a direction of the flow, the first, second and third portions (120, 130, 140) alternating in the direction of the flow, wherein: the first portion of the physical object further comprises a first transition surface located below the plane of smooth surface of the first portion; an angle between the first 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 155 degrees; the second portion of the physical object further comprises a second transition surface located above the plane of the smooth surface of the first portion, wherein the second transition surface intersects the smooth surface of the first portion such that an edge of the transition surface is created along the smooth surface of the first portion; and an angle between the second transition surface of the second 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 155 degrees. forming a smooth surface on a first portion of a physical object; forming periodic riblets on a second portion of the physical object; forming a smooth surface on a third portion of the physical object; and generating a flow over the periodic riblets of the second portion (1300 of the physical object and over the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; wherein: the second portion of the physical object is adjacent to and between the first and third portions (120, 140) of the physical object; each peak of each riblet of the periodic riblets of the second portion of the physical object is located above a plane of the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; each valley between adjacent riblets of the periodic riblets of the second portion of the physical object is located below the plane of the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; and a length of each riblet of the periodic riblets of the second portion runs parallel to a direction of the flow, the first, second and third portions (120, 130, 140) alternating in the direction of the flow, the second portion of the physical object is adjacent to and between the first and third portions (120, 140) of the physical object; each peak of each riblet of the periodic riblets of the second portion of the physical object is located above a plane of the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; each valley between adjacent riblets of the periodic riblets of the second portion of the physical object is located below the plane of the smooth surfaces (122, 142) of the first and third portions (120, 140) of the physical object; and a length of each riblet of the periodic riblets of the second portion runs parallel to a direction of the flow, the first, second and third portions (120, 130, 140) alternating in the direction of the flow, the first portion of the physical object further comprises a first transition surface located below the plane of smooth surface of the first portion; an angle between the first 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 155 degrees; the second portion of the physical object further comprises a second transition surface located above the plane of the smooth surface of the first portion, wherein the second transition surface intersects the smooth surface of the first portion such that an edge of the transition surface is created along the smooth surface of the first portion; and an angle between the second transition surface of the second 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 155 degrees.