Influence of entrapped gas morphology at liquid–solid interface on underwater drag reduction effect

2021 ◽  
Vol 33 (12) ◽  
pp. 122111
Author(s):  
Zhe Wang ◽  
Bao Wang ◽  
Ding Weng ◽  
Caihua Wang ◽  
Na Sun ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Solid Interface ◽  
Reduction Effect

scholarly journals Noise Reduction Effect of Superhydrophobic Surfaces with Streamwise Strip of Channel Flow

2021 ◽  
Vol 11 (9) ◽  
pp. 3869
Author(s):  
Chen Niu ◽  
Yongwei Liu ◽  
Dejiang Shang ◽  
Chao Zhang
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Noise Reduction ◽  
Channel Flow ◽  
Superhydrophobic Surface ◽  
Sound Field ◽  
Flow Noise ◽  
Slip Boundary ◽  
Eddy Simulation ◽  
Reduction Effect

Superhydrophobic surface is a promising technology, but the effect of superhydrophobic surface on flow noise is still unclear. Therefore, we used alternating free-slip and no-slip boundary conditions to study the flow noise of superhydrophobic channel flows with streamwise strips. The numerical calculations of the flow and the sound field have been carried out by the methods of large eddy simulation (LES) and Lighthill analogy, respectively. Under a constant pressure gradient (CPG) condition, the average Reynolds number and the friction Reynolds number are approximately set to 4200 and 180, respectively. The influence on noise of different gas fractions (GF) and strip number in a spanwise period on channel flow have been studied. Our results show that the superhydrophobic surface has noise reduction effect in some cases. Under CPG conditions, the increase in GF increases the bulk velocity and weakens the noise reduction effect. Otherwise, the increase in strip number enhances the lateral energy exchange of the superhydrophobic surface, and results in more transverse vortices and attenuates the noise reduction effect. In our results, the best noise reduction effect is obtained as 10.7 dB under the scenario of the strip number is 4 and GF is 0.5. The best drag reduction effect is 32%, and the result is obtained under the scenario of GF is 0.8 and strip number is 1. In summary, the choice of GF and the number of strips is comprehensively considered to guarantee the performance of drag reduction and noise reduction in this work.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

Density and Drag Reduction With Hollow Glass Additives

2014 ◽  
Author(s):  
Bahri Kutlu ◽  
Evren M. Ozbayoglu ◽  
Stefan Z. Miska ◽  
Nicholas Takach ◽  
Mengjiao Yu ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Rheological Behavior ◽  
Drilling Fluid ◽  
Hydraulic Drag ◽  
Effect Of Temperature ◽  
Survival Ratio ◽  
Fluid Density ◽  
Hollow Glass ◽  
Glass Spheres ◽  
Reduction Effect

This study concentrates on the use of materials known as hollow glass spheres, also known as glass bubbles, to reduce the drilling fluid density below the base fluid density without introducing a compressible phase to the wellbore. Four types of lightweight glass spheres with different physical properties were tested for their impact on rheological behavior, density reduction effect, survival ratio at elevated pressures and hydraulic drag reduction effect when mixed with water based fluids. A Fann75 HPHT viscometer and a flow loop were used for the experiments. Results show that glass spheres successfully reduce the density of the base drilling fluid while maintaining an average of 0.93 survival ratio, the rheological behavior of the tested fluids at elevated concentrations of glass bubbles is similar to the rheological behavior of conventional drilling fluids and hydraulic drag reduction is present up to certain concentrations. All results were integrated into hydraulics calculations for a wellbore scenario that accounts for the effect of temperature and pressure on rheological properties, as well as the effect of glass bubble concentration on mud temperature distribution along the wellbore. The effect of drag reduction was also considered in the calculations.

scholarly journals A Study of Drag Reduction on Cylinders with Different V-Groove Depths on the Surface

Water ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 36
Author(s):  
Jiyang Qi ◽  
Yue Qi ◽  
Qunyan Chen ◽  
Fei Yan
Keyword(s):  
Drag Reduction ◽  
Drag Coefficient ◽  
Vortex Structure ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Groove Surface ◽  
Smooth Cylinder ◽  
Groove Structure ◽  
Reduction Effect

In this study, the drag reduction effect is studied for a cylinder with different V-groove depths on its surface using a k-ω/SST (Shear Stress Transport) turbulence model of computational fluid dynamics (CFD), while a particle image velocimetry (PIV) system is employed to analyze the wake characteristics for a smooth cylinder and a cylinder with different V-groove depths on its surface at different Reynolds numbers. The study focuses on the characteristics of the different V-groove depths on lift coefficient, drag coefficient, the velocity distribution of flow field, pressure coefficient, vortex shedding, and vortex structure. In comparison with a smooth cylinder, the lift coefficient and drag coefficient can be reduced for a cylinder with different V-groove depths on its surface, and the maximum reduction rates of lift coefficient and drag coefficient are about 34.4% and 16%, respectively. Otherwise, the vortex structure presents a complete symmetry for the smooth cylinder, however, the symmetry of the vortex structure becomes insignificant for the V-shaped groove structure with different depths. This is also an important reason for the drag reduction effect of a cylinder with a V-groove surface.

scholarly journals 710 Experimental Study on Friction Drag Reduction Effect of Flexible Tube(1)

2006 ◽  
Vol 2006 (0) ◽  
pp. _710-a_
Author(s):  
Zhigang GAO ◽  
Masatomo OHWAKI ◽  
Motoyuki ITOH ◽  
Shinji TAMANO ◽  
Kazuhiko YOKOTA
Keyword(s):  
Experimental Study ◽  
Drag Reduction ◽  
Friction Drag ◽  
Flexible Tube ◽  
Reduction Effect ◽  
Friction Drag Reduction

scholarly journals Fabrication of superhydrophobic surface by oxidation growth of flower-like nanostructure on a steel foil

RSC Advances ◽  
2017 ◽  
Vol 7 (41) ◽  
pp. 25341-25346 ◽  
Author(s):  
Rui Weng ◽  
Haifeng Zhang ◽  
Liang Yin ◽  
Wanting Rong ◽  
Zhiwen Wu ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Novel Method ◽  
Reduction Effect ◽  
Oxidation Growth

A novel method to fabricate the superhydrophobic surface with a 3D flower-like micro-nanostructure on the steel foil was presented here. The surface shows good drag reduction effect and has numerous technical applications in drag reduction field.

scholarly journals Drag Reduction Effect and Wettability of Surface with Dual-Length Micro-Pillars

2009 ◽  
Vol 4 (3) ◽  
pp. 614-622 ◽  
Author(s):  
Masato HASEGAWA ◽  
Shinjiro NITTA ◽  
Hisanori UENO
Keyword(s):  
Drag Reduction ◽  
Reduction Effect ◽  
Micro Pillars

scholarly journals An investigation on the drag reduction performance of bioinspired pipeline surfaces with transverse microgrooves

2020 ◽  
Vol 11 ◽  
pp. 24-40 ◽  
Author(s):  
Weili Liu ◽  
Hongjian Ni ◽  
Peng Wang ◽  
Yi Zhou
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Pressure Loss ◽  
Fluid Transport ◽  
Reduction Rate ◽  
Orthogonal Analysis ◽  
Maximum Drag Reduction ◽  
Reduction Effect ◽  
Save Energy ◽  
Microgrooved Surface

A novel surface morphology for pipelines using transverse microgrooves was proposed in order to reduce the pressure loss of fluid transport. Numerical simulation and experimental research efforts were undertaken to evaluate the drag reduction performance of these bionic pipelines. It was found that the vortex ‘cushioning’ and ‘driving’ effects produced by the vortexes in the microgrooves were the main reason for obtaining a drag reduction effect. The shear stress of the microgrooved surface was reduced significantly owing to the decline of the velocity gradient. Altogether, bionic pipelines achieved drag reduction effects both in a pipeline and in a concentric annulus flow model. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were obtained by an orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% could be achieved. The numerical simulation and experimental results were cross-checked and found to be consistent with each other, allowing to verify that the utilization of bionic theory to reduce the pressure loss of fluid transport is feasible. These results can provide theoretical guidance to save energy in pipeline transportations.

Drag reduction effect of crude palm oil flow by using Tween 80 in pentagon spiral pipe

2020 ◽  
Author(s):  
Yanuar ◽  
Gunawan ◽  
Angga Arianda ◽  
M. Raihan Setiawan ◽  
Whisnu Febriansyah
Keyword(s):  
Drag Reduction ◽  
Palm Oil ◽  
Tween 80 ◽  
Crude Palm Oil ◽  
Oil Flow ◽  
Reduction Effect
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