{"id":822,"date":"2020-03-04T10:00:18","date_gmt":"2020-03-04T09:00:18","guid":{"rendered":"http:\/\/yvcharron.com\/?page_id=822"},"modified":"2020-12-20T11:57:52","modified_gmt":"2020-12-20T10:57:52","slug":"three-dimension-structures-type-2","status":"publish","type":"page","link":"https:\/\/yvcharron.com\/index.php\/three-dimension-structures-type-2\/","title":{"rendered":"Three Dimension Structures – Two oscillating waves – 3D_2"},"content":{"rendered":"\n

Keywords: structured surfaces three-dimension structures two-orthogonal waves flow drag reduction turbulent turbulence<\/p>\n\n\n\n

Adding a normal wave to the transverse wave<\/strong><\/h2>\n\n\n\n

Two dimension structured\nsurfaces<\/strong> have shown the capability to provide a flow drag\nreduction of the order of 10 %. This flow drag reduction is lower in the case\nof riblets with a triangle shape (5 to 6%) and larger in the case of riblets\nwith a knife blade shape (10 to 12%). These performances were calculated with a\nRANS code and found in line with experiments carried out in the past by\nnumerous workers. See web page on \u201c2D structured surfaces\u201d.<\/p>\n\n\n\n

http:\/\/yvcharron.com\/index.php\/two-dimension-structures\/<\/a><\/p>\n\n\n\n

A three dimension structure surface – Type 1<\/strong> including two flow drag reduction mechanisms has been analysed. These mechanisms are: a 2D structured surface associated with a transverse oscillating flow (wave). The resulting flow drag reduction is of the order of 20% at the optimum condition. These performances were determined with a LES code. See web page on \u201c3D structured surfaces \u2013 Type 1\u201d.<\/p>\n\n\n\n

_http:\/\/yvcharron.com\/index.php\/three-dimension-structured-surfaces-type-1\/<\/a><\/p>\n\n\n\n

A new shape of 3D structured surface (Type 2)<\/strong> is proposed to provide a greater flow drag reduction. This type 2 includes two orthogonal oscillating waves<\/strong>, one parallel to the structured surface (as per type 1) and a new one normal to the structured surface and oriented in the flow direction. As very little calculation has been performed with this type of 3D structured surface, a phenomenological analysis is provided below to explain the mode of operation of the different types of riblets: 2D longitudinal riblets and 3D riblets, types 1 and 2.<\/p>\n\n\n\n

\"Principle<\/figure><\/div>\n\n\n\n
FOR MORE DETAILS : ______ a_3_3_Surf Struc 3DTypeTwoOrtWav_Ang_2007<\/a>T\u00e9l\u00e9charger<\/a><\/div>\n\n\n\n

Potential of the integration of a third flow drag reduction mechanism<\/strong><\/h2>\n\n\n\n

A LES Code<\/strong> could establish the mechanism of drag reduction provided by a plate oscillating transversely to the main flow direction. The maximum flow drag reduction was obtained for a dimensionless period of 100<\/strong>. In this specific case, the drag reduction tends to increase with the amplitude of the oscillation, disregarding the energy required to move the plate.<\/p>\n\n\n\n

2D\nriblets of the knife blade type provide a maximum drag reduction of the order\nof 10 %. The same result was found with RANS and LES codes (see corresponding\nWeb site pages).<\/p>\n\n\n\n

3D <\/strong>structured surfaces (Type 1) combining the above two flow drag reduction mechanisms (2D riblets and transposed transverse flow oscillation) provide a drag reduction of the order of 20 % according to the LES code validated with the oscillating plate and 2D riblets. The maximum drag reduction was achieved for a dimensionless period of 100 and a maximum angle of the transverse oscillation of the order of 10 degrees.<\/p>\n\n\n\n

It is anticipated that further drag reduction could be obtained by adding a second oscillating wave oriented in the flow direction and orthogonal to the transverse wave<\/strong>. This second wave (normal wave) could be of a sine wave type with a frequency equal to twice the transverse wave frequency<\/strong>. This normal wave would provide a riblet height increase at the crests of the transverse wave and a riblet height decrease at the inflexion points of the transverse wave. This should provide several advantages:<\/p>\n\n\n\n