Shark-skin surfaces for fluid-drag reduction in turbulent flow: a review

2010 ◽  
Vol 368 (1929) ◽  
pp. 4775-4806 ◽  
Author(s):  
Brian Dean ◽  
Bharat Bhushan
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Performance Studies ◽  
Flow Characteristics ◽  
Shark Skin ◽  
Turbulent Flow Regime ◽  
Fluid Drag ◽  
Maximum Drag Reduction ◽  
Manufacturing Techniques ◽  
Fluid Flow Characteristics

The skin of fast-swimming sharks exhibits riblet structures aligned in the direction of flow that are known to reduce skin friction drag in the turbulent-flow regime. Structures have been fabricated for study and application that replicate and improve upon the natural shape of the shark-skin riblets, providing a maximum drag reduction of nearly 10 per cent. Mechanisms of fluid drag in turbulent flow and riblet-drag reduction theories from experiment and simulation are discussed. A review of riblet-performance studies is given, and optimal riblet geometries are defined. A survey of studies experimenting with riblet-topped shark-scale replicas is also given. A method for selecting optimal riblet dimensions based on fluid-flow characteristics is detailed, and current manufacturing techniques are outlined. Due to the presence of small amounts of mucus on the skin of a shark, it is expected that the localized application of hydrophobic materials will alter the flow field around the riblets in some way beneficial to the goals of increased drag reduction.

scholarly journals Analysis of Shark Skin Riblet Surfaces for Fluid Drag Reduction in Turbulent Flow Regime

2019 ◽  
Vol 9 (1S4) ◽  
pp. 666-668
Keyword(s):  
Fluid Flow ◽  
Flow Field ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Flow System ◽  
Shark Skin ◽  
Structured Surfaces ◽  
Turbulent Flow Regime ◽  
Fluid Drag ◽  
Fluid Drag Reduction

: The integument of fast swimming shark exhibits riblet inspired micro- structured surfaces oriented in the path of flow that will help to make lesser the wall drag in the tempestuous-flow system (turbulent flow). Design have been made for study and utilization, that has been recreate and refine as same as of the shark-skin riblets, presuming an extreme drag depletion of nearly 10% (percent). Mechanism of fluid drag in tempestuous flow and riblet drag depletion theories from experiments and simulations are examined. An examination of riblet intrepratation are discussed and the stellar riblet sizes are defined. An assessment of studies experimenting with riblets-topped shark scale replicas is also discussed. A method for preferring stellar riblet dimensions based on fluid-flow attributes is briefed and current manufacturing approaches are summarized. Due to the existence of little amounts of mucus/booger membranes on the integument of the shark, it is presumed that the constrained application of aqua phobic materials will recast the flow field around the riblets in some way favorable to the goals of augmented drag depletion

scholarly journals Numerical investigation of flow characteristics over stepped spillways

2020 ◽  
Author(s):  
Aytaç Güven ◽  
Ahmed Hussein Mahmood
Keyword(s):  
Numerical Model ◽  
Turbulent Flow ◽  
Flow Characteristics ◽  
Air Entrainment ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Entrainment Velocity ◽  
Fluid Flow Characteristics ◽  
3D Package ◽  
Good Agreement

Abstract Spillways are constructed to evacuate the flood discharge safely not to let the flood wave overtop the dam body. There are different types of spillways, ogee type being the conventional one. Stepped spillway is an example of nonconventional spillways. The turbulent flow over stepped spillway was studied numerically by using the Flow-3D package. Different fluid flow characteristics such as longitudinal flow velocity, temperature distribution, density and chemical concentration can be well simulated by Flow-3D. In this study, the influence of slope changes on flow characteristics such as air entrainment, velocity distribution and dynamic pressures distribution over the stepped spillway was modelled by Flow-3D. The results from the numerical model were compared with the experimental study done by others in the literature. Two models of the stepped spillway with different discharge for each model was simulated. The turbulent flow in the experimental model was simulated by the Renormalized Group (RNG) turbulence scheme in the numerical model. A good agreement was achieved between the numerical results and the observed ones, which were exhibited in terms of graphics and statistical tables.

Controllable Adjustment of Bio-Replicated Shark Skin Drag Reduction Riblets

2013 ◽  
Vol 461 ◽  
pp. 677-680 ◽  
Author(s):  
Xin Zhang ◽  
De Yuan Zhang ◽  
Jun Feng Pan ◽  
Xiang Li ◽  
Hua Wei Chen
Keyword(s):  
Drag Reduction ◽  
Living Environment ◽  
Reduction Peak ◽  
Shark Skin ◽  
Forming Technology ◽  
Surrounding Environment ◽  
Maximum Drag Reduction ◽  
Reduction Function ◽  
Volume Swelling ◽  
3D Volume

Although natural shark shin surface morphology has excellent drag reduction performance, it exhibits maximum drag reduction just within swimming speed of the shark. That is, drag reduction function of shark skin is unadjustable to surrounding environment. To expand applications of bio-replicated shark skin, two novel controllable adjustments of shark skin drag reduction riblets including one-direction elongation and 3D volume swelling amplification, were explored. The validity and efficiency of the two approaches to change the drag reduction riblets were verified by comparison between microstructure of adjusted and original shark skin. And the translation of drag reduction peak of natural surface function from living environment to various application environments was proved by experimental measurement. By comparison, the elongating method is efficient but low drag reduction, while the swelling way can get the same drag reduction as shark skin but cost more time. So they should be performed according to the situation. As the optimal application velocity range of the imitative shark shin morphology can be expanded by both of the two methods, the application field of the biomimetic drag reduction surface fabricated by the bio-replicated forming technology was extended.

Effect of Polymer Fluid Viscoelastic Properties on the Initiation of Transition From Laminar to Turbulent Flow Regime and the Drag Reduction in the Flow Through Horizontal Pipe

2020 ◽  
Author(s):  
Mehmet Meric Hirpa ◽  
Ergun Kuru
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Flow Regime ◽  
Shear Viscosity ◽  
Viscoelastic Properties ◽  
Dynamic Pressure ◽  
Flow Loop ◽  
Horizontal Pipe ◽  
Fluid Elasticity ◽  
Turbulent Flow Regime

Abstract This study investigated the flow of viscoelastic fluids through horizontal pipeline mainly focusing on the effect of fluid elasticity on drag reduction and onset of transition to turbulent flow regime. In order to be able to see the sole effect of fluid elasticity (independent from shear viscosity), three non-Newtonian fluids having the same shear viscosity but different viscoelastic properties were tested in the horizontal flow loop. Those fluids were the dilute solutions of partially hydrolysed polyacrylamide (HPAM) and they were prepared by using three polymer grades of HPAM (i.e. 5 × 105, 8 × 106, 20 × 106 g/gmol) in different compositions. Experiments have shown that increasing fluid elasticity resulted in higher drag reduction in pipe flow. Moreover, fluid elasticity affected the onset of turbulent flow and an earlier transition to turbulent flow regime (as compared to water flow) was only observed for the flow of fluid having the highest elastic properties. So, understanding effects of fluid elasticity on flow dynamics might improve the performance of fluids engineered for hole cleaning/cuttings transport in oil and gas well drilling or proppant transport in hydraulic fracturing operations. Also, field efforts to find solutions to problems caused by excessive dynamic pressure losses encountered in drilling horizontal or extended reach wells or in transporting hydrocarbons through pipeline might benefit from the findings of this or further extended research on this subject.

Sign in / Sign up

Export Citation Format

Share Document