Experimental Study on the Fabrication of Drag Reducing Riblet Surfaces by Using DLP Technique

Nature and living organisms provide an abundance of creative designs that can be used to solve many technical and engineering problems. Fast swimming shark skin is covered with low drag microstructures which is a good source of inspiration from nature for numerous engineering applications. The main objective of this research is to explore the abilities of additive manufacturing methods and to use 3D printing technology to fabricate drag-reducing riblet surfaces. Thus, the shark skin imitated riblet surfaces have been designed and fabricated in micron scale by using a yellow resin specially-formulated for 3D printers and the DLP technique. Then, a closed channel made of Plexiglas with its bottom surface covered with a riblet surface has been designed and constructed to evaluate the ability of these surfaces in reducing the pressure drop. An engineering system including a pump, rotameter, water tank, connecting tubes, differential pressure transmitter, power supply and monitor has been installed to measure the amount of pressure drop across the channel for various riblet surfaces. The tests have been performed for different Reynolds numbers and various riblet surfaces, and the pressure drop results have been compared with empirical data for a channel with simple sample. The findings indicate the ability of riblet surfaces in reducing the pressure drop across the channel.