Effect of Nano-Titanium Dioxide Contained in Titania-Polyurea Coating on Marina Biofouling and Drag Reduction

2020 ◽  
Vol 16 (10) ◽  
pp. 1530-1541
Author(s):  
Yuanzhe Li ◽  
Yissue Woo ◽  
Manoj Sekar ◽  
Srikanth Narasimalu ◽  
ZhiLi Dong
Keyword(s):  
Titanium Dioxide ◽  
Drag Reduction ◽  
Surface Characterization ◽  
Reduction Rate ◽  
Spray Coating ◽  
Key Factors ◽  
Marine Animals ◽  
Nano Titanium Dioxide ◽  
Marine Worms ◽  
Riblet Surface

Marine structures often suffer from biofouling, which may lead to macrofouling by marine animals like marine worms and barnacles, weighing down the structures and increasing the drag. This paper analyses the effect of the newly fabricated biological anti-adhesion Titania-Polyurea spray coating, which can effectively reduce biofouling from enriching on the surface. Through the surface characterization, bioassays and micro-channel drag-reduction test, the antibacterial effect caused by the nano-titanium dioxide is systematically studied. Compared to the different weight percentages of nano-TiO2 in the coating system, the photocatalytic activity, riblet surface structure and hydrophobic wettability are supposed to be the key factors to reduce the flow resistance at a drag reduction rate of 3.0% and further enhance the anti-biofouling performance under dark conditions.

Experimental Study on Drag-Reduction Effect of a New Sinusoidal Riblet

2012 ◽  
Author(s):  
Monami Sasamori ◽  
Kaoru Iwamoto ◽  
Akira Murata
Keyword(s):  
Experimental Study ◽  
Drag Reduction ◽  
Flat Surface ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Reduction Rate ◽  
Physical Mechanisms ◽  
Image Velocimetry ◽  
Reduction Effect ◽  
Riblet Surface

An experimental study of a new three-dimensional (3-D) riblet has been carried out. The lateral spacing of our 3-D riblet surface is sinusoidally varied in the streamwise direction (see Fig. 3). In the comparison of the optimal two-dimensional (2-D) blade riblet which shows 9.9% drag reduction rate [1], the riblet height, thickness and averaged lateral spacing are respectively 0.83, 5 and 2.5 times larger than those of the optimal 2-D riblet in wall units. The net drag reduction rate of 11.7% has been confirmed in a low-speed wind channel at the bulk Reynolds number of 3400. The flow structure over the 3-D riblet mounted a wall was also analyzed in the velocity field by using 2-D Particle Image Velocimetry and was compared with the corresponding flow over the flat surface in an attempt to identify the physical mechanisms for the drag reduction. The normal turbulent intensities on the present riblet are almost same as those of the flat surface, whereas the Reynolds shear stress is much decreased, and especially becomes negative near the riblet height. These are different phenomena from those of all the previous riblets [1–7].

scholarly journals Investigation of the Turbulent Drag Reduction Mechanism of a Kind of Microstructure on Riblet Surface

Micromachines ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 59
Author(s):  
Mingrui Ao ◽  
Miaocao Wang ◽  
Fulong Zhu
Keyword(s):  
Drag Reduction ◽  
Three Dimensional ◽  
Reduction Rate ◽  
Water Area ◽  
Reduction Mechanism ◽  
Surface Drag ◽  
Groove Surface ◽  
Turbulent Drag ◽  
Micro Structures ◽  
Riblet Surface

With the k-ε renormalization group turbulence model, the drag reduction mechanism of three- dimensional spherical crown microstructure of different protruding heights distributing on the groove surface was studied in this paper. These spherical crown microstructures were divided into two categories according to the positive and negative of protruding height. The positive spherical crown micro-structures can destroy a large number of vortexes on the groove surface, which increases relative friction between water flow and the groove surface. With decreasing the vertical height of the spherical crown microstructure, the number of rupture vortexes gradually decreases. Due to the still water area causes by the blocking effect of the spherical crown microstructure, it was found that the shear stress on the groove surface can be reduced, which can form the entire drag reduction state. In another case, the spherical crown microstructures protrude in the negative direction, vortexes can be generated inside the spherical crown, it was found that these vortexes can effectively reduce the resistance in terms of pressure and friction. In a small volume, it was shown that the surface drag reduction rate of spherical crown microstructures protrudes in negative directions can be the same as high as 24.8%.

Preparation of Photocatalytic Decorative Concrete Based on Nano-Titanium Dioxide Adsorbed by Clay Brick from Building Waste and Its Application in Pavement Structure of Railway Freight Yard

2020 ◽  
Vol 15 (2) ◽  
pp. 250-256
Author(s):  
Ruiping Liu ◽  
Jia Mao ◽  
Xiangyu Li
Keyword(s):  
Titanium Dioxide ◽  
Surface Layer ◽  
Reduction Rate ◽  
Concrete Surface ◽  
Liaoning Province ◽  
Photocatalytic Efficiency ◽  
Clay Brick ◽  
Railway Freight ◽  
Pavement Structure ◽  
Nano Titanium Dioxide

In this paper, based on the clay brick of building waste, nano-titanium dioxide photocatalytic decorative concrete was prepared, and its application in the pavement structure of a railway freight yard was studied. The results show that the loading capacity of nano-titanium dioxide on clay sand carrier is better than that on zeolite sand. With the increase of powder content, the photocatalytic efficiency of decorative concrete surface decreases, but the degree of reduction is small. Compared with laboratory conditions, the reduction rate of NOX in surface layer of decorative concrete under natural curing condition is lower. The photocatalytic efficiency did not decrease significantly at 90 days. Cement cementing could greatly improve the bonding effect of nano-titanium dioxide, which made the photocatalytic activity of decorative concrete surface layer have good durability. In this paper, decorative concrete is applied to the pavement engineering of a railway container yard in Liaoning Province. The pavement structure combination design, cement concrete pavement thickness design, pavement panel design and joint design are analyzed.

Drag Reduction Performance Analysis of Chlamys nobilis Ribbed Surface

2019 ◽  
Vol 53 (1) ◽  
pp. 43-52
Author(s):  
Binying Hu ◽  
Xiuqin Bai ◽  
Yifeng Fu ◽  
Chengqing Yuan
Keyword(s):  
Drag Reduction ◽  
Simulation Analysis ◽  
Reduction Rate ◽  
Physical Structure ◽  
Living Condition ◽  
Chlamys Nobilis ◽  
Ship Hulls ◽  
Biological Adhesion ◽  
Reduction Effect ◽  
Riblet Surface

AbstractConsidering the fact that the living condition of the shell is similar to the significant defiled environment of a ship, it is selected as a bionic object to study drag reduction for ship hulls. Previous studies have demonstrated that the special physical structure of the shell surface results in preventing biological adhesion. In order to improve ship operation efficiency, collaborative research on the physical structure was first carried out by studying the drag reduction performance of the actual Chlamys nobilis surface among the antifouling ranges of the structural dimensions without simplification. Thereafter, the drag reduction mechanism was analyzed by simulation analysis of the surface structures on the antifouling region of the C. nobilis surface. Simulation results demonstrated that a pair of counter-rotating vortices appeared at the tip of the bionic riblet surface. The secondary vortex, induced by the counter-rotating vortices, was the main reason for the drag reduction effect of the bionic riblet surface. Moreover, analysis of the drag reduction performance indicated that the maximum drag reduction rate could reach up to 8.53% at the speed of 3 m/s. This study reveals the drag reduction effect of the C. nobilis surface, which will provide a reference for combining drag reduction and antifouling.

A comparative study on the efficacy of different probes to predict the photo-activity of nano-titanium dioxide toward biomolecules

RSC Advances ◽  
2015 ◽  
Vol 5 (109) ◽  
pp. 89559-89568 ◽  
Author(s):  
A. Marucco ◽  
E. Carella ◽  
I. Fenoglio
Keyword(s):  
Titanium Dioxide ◽  
Comparative Study ◽  
Systematic Study ◽  
Living Organisms ◽  
Nano Titanium Dioxide

A systematic study has been performed to select cell-free tests able to predict the photo-activity of nano-TiO2 in living organisms.

scholarly journals Soil-aged nano titanium dioxide effects on full-grown carrot: Dose and surface-coating dependent improvements on growth and nutrient quality

2021 ◽  
Vol 774 ◽  
pp. 145699
Author(s):  
Yi Wang ◽  
Chaoyi Deng ◽  
Keni Cota-Ruiz ◽  
Jose R. Peralta-Videa ◽  
Jose A. Hernandez-Viezcas ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Surface Coating ◽  
Nutrient Quality ◽  
Nano Titanium Dioxide

scholarly journals Global effect of local skin friction drag reduction in spatially developing turbulent boundary layer

2016 ◽  
Vol 805 ◽  
pp. 303-321 ◽  
Author(s):  
A. Stroh ◽  
Y. Hasegawa ◽  
P. Schlatter ◽  
B. Frohnapfel
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Drag Reduction ◽  
Control Region ◽  
Reduction Rate ◽  
Wall Turbulence ◽  
Local Skin ◽  
Control Schemes ◽  
Local Skin Friction ◽  
Friction Drag Reduction

A numerical investigation of two locally applied drag-reducing control schemes is carried out in the configuration of a spatially developing turbulent boundary layer (TBL). One control is designed to damp near-wall turbulence and the other induces constant mass flux in the wall-normal direction. Both control schemes yield similar local drag reduction rates within the control region. However, the flow development downstream of the control significantly differs: persistent drag reduction is found for the uniform blowing case, whereas drag increase is found for the turbulence damping case. In order to account for this difference, the formulation of a global drag reduction rate is suggested. It represents the reduction of the streamwise force exerted by the fluid on a plate of finite length. Furthermore, it is shown that the far-downstream development of the TBL after the control region can be described by a single quantity, namely a streamwise shift of the uncontrolled boundary layer, i.e. a changed virtual origin. Based on this result, a simple model is developed that allows the local drag reduction rate to be related to the global one without the need to conduct expensive simulations or measurements far downstream of the control region.

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