scholarly journals Contribution of Superhydrophobic Surfaces and Polymer Additives to Drag Reduction

2021 ◽  
Author(s):  
Taiba Kouser ◽  
Yongliang Xiong ◽  
Dan Yang
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surfaces ◽  
Polymer Additives

A drag reduction in cwm transportation with polymer additives

KSME Journal ◽  
1991 ◽  
Vol 5 (1) ◽  
pp. 53-58
Author(s):  
Seon Chang Kim ◽  
Chong Bo Kim
Keyword(s):  
Drag Reduction ◽  
Polymer Additives

scholarly journals Sustainable Drag Reduction in Turbulent Taylor-Couette Flows by Depositing Sprayable Superhydrophobic Surfaces

2015 ◽  
Vol 114 (1) ◽  
Author(s):  
Siddarth Srinivasan ◽  
Justin A. Kleingartner ◽  
Jonathan B. Gilbert ◽  
Robert E. Cohen ◽  
Andrew J. B. Milne ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surfaces ◽  
Taylor Couette

Turbulent flow over superhydrophobic surfaces with streamwise grooves

2014 ◽  
Vol 747 ◽  
pp. 186-217 ◽  
Author(s):  
S. Türk ◽  
G. Daschiel ◽  
A. Stroh ◽  
Y. Hasegawa ◽  
B. Frohnapfel
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Secondary Flow ◽  
Slip Length ◽  
Laminar Flows ◽  
Superhydrophobic Surfaces ◽  
Mean Velocity ◽  
Effective Slip Length ◽  
Effective Slip

AbstractWe investigate the effects of superhydrophobic surfaces (SHS) carrying streamwise grooves on the flow dynamics and the resultant drag reduction in a fully developed turbulent channel flow. The SHS is modelled as a flat boundary with alternating no-slip and free-slip conditions, and a series of direct numerical simulations is performed with systematically changing the spanwise periodicity of the streamwise grooves. In all computations, a constant pressure gradient condition is employed, so that the drag reduction effect is manifested by an increase of the bulk mean velocity. To capture the flow properties that are induced by the non-homogeneous boundary conditions the instantaneous turbulent flow is decomposed into the spatial-mean, coherent and random components. It is observed that the alternating no-slip and free-slip boundary conditions lead to the generation of Prandtl’s second kind of secondary flow characterized by coherent streamwise vortices. A mathematical relationship between the bulk mean velocity and different dynamical contributions, i.e. the effective slip length and additional turbulent losses over slip surfaces, reveals that the increase of the bulk mean velocity is mainly governed by the effective slip length. For a small spanwise periodicity of the streamwise grooves, the effective slip length in a turbulent flow agrees well with the analytical solution for laminar flows. Once the spanwise width of the free-slip area becomes larger than approximately 20 wall units, however, the effective slip length is significantly reduced from the laminar value due to the mixing caused by the underlying turbulence and secondary flow. Based on these results, we develop a simple model that allows estimating the gain due to a SHS in turbulent flows at practically high Reynolds numbers.

scholarly journals Research Progress on the Collaborative Drag Reduction Effect of Polymers and Surfactants

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 444 ◽  
Author(s):  
Yunqing Gu ◽  
Songwei Yu ◽  
Jiegang Mou ◽  
Denghao Wu ◽  
Shuihua Zheng
Keyword(s):  
Drag Reduction ◽  
Reynolds Numbers ◽  
Research Progress ◽  
Polymer Additives ◽  
Factors Affecting ◽  
Mechanism Model ◽  
Reduction Effect ◽  
Reduction Characteristics ◽  
Degradation Properties ◽  
Degradation Ability

Polymer additives and surfactants as drag reduction agents have been widely used in the field of fluid drag reduction. Polymer additives can reduce drag effectively with only a small amount, but they degrade easily. Surfactants have an anti-degradation ability. This paper categorizes the mechanism of drag reducing agents and the influencing factors of drag reduction characteristics. The factors affecting the degradation of polymer additives and the anti-degradation properties of surfactants are discussed. A mixture of polymer additive and surfactant has the characteristics of high shear resistance, a lower critical micelle concentration (CMC), and a good drag reduction effect at higher Reynolds numbers. Therefore, this paper focuses more on a drag reducing agent mixed with a polymer and a surfactant, including the mechanism model, drag reduction characteristics, and anti-degradation ability.

Influence of textural statistics on drag reduction by scalable, randomly rough superhydrophobic surfaces in turbulent flow

2019 ◽  
Vol 31 (4) ◽  
pp. 042107 ◽  
Author(s):  
Anoop Rajappan ◽  
Kevin Golovin ◽  
Brian Tobelmann ◽  
Venkata Pillutla ◽  
Abhijeet ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Drag Reduction ◽  
Superhydrophobic Surfaces
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