Effect of micro-grooves on drag reduction in Taylor–Couette flow

Xu, Baorui; Li, Hongyuan; Liu, Xiaochao; Xiang, Yaolei; Lv, Pengyu; Tan, Xiangkui; Zhao, Yaomin; Sun, Chao; Duan, Huiling

doi:10.1063/5.0145900

Cited by 6 publications

(2 citation statements)

References 45 publications

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“…The total measured torque ( T s ) consists of two components, T and T b , corresponding to the frictional resistances caused by the sides and the top/bottom ends of the cylinder, respectively. To determine T b , we used the linearization method previously employed by Greidanus et al Therefore, T is calculated by subtracting the measured T b from the measured T s , as detailed in the previous article . For each speed, the torque T s is measured for 30 s and three tests are conducted, with the torque averaged across all runs.…”

Section: Methodsmentioning

confidence: 99%

“…To determine T b , we used the linearization method previously employed by Greidanus et al 42 Therefore, T is calculated by subtracting the measured T b from the measured T s , as detailed in the previous article. 43 For each speed, the torque T s is measured for 30 s and three tests are conducted, with the torque averaged across all runs. DR is defined as…”

Section: Re R D Vmentioning

confidence: 99%

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Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips

Cao,

Liu,

Zhang

et al. 2024

ACS Appl. Mater. Interfaces

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Superhydrophobic surfaces (SHS) offer versatile applications by trapping an air layer within microstructures, while water jet impact can destabilize this air layer and deactivate the functions of the SHS. The current work presents for the first time that introducing parallel hydrophilic strips to SHS (SHS-s) can simultaneously improve both water impalement resistance and drag reduction (DR). Compared with SHS, SHS-s demonstrates a 125% increase in the enduring time against the impact of water jet with velocity of 11.9 m/s and a 97% improvement in DR at a Reynolds number of 1.4 × 10 4 . The key mechanism lies in the enhanced stability of the air layer due to air confinement by the adjacent three-phase contact lines. These lines not only impede air drainage through the surface microstructures during water jet impact, entrapping the air layer to resist water impalement, but also prevent air floating up due to buoyancy in Taylor−Couette flow, ensuring an even spread of the air layer all over the rotor, boosting DR. Moreover, failure modes of SHS under water jet impact are revealed to be related to air layer decay and surface structure destruction. This mass-producible structured surface holds the potential for widespread use in DR for hulls, autonomous underwater vehicles, and submarines.

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Section: Methodsmentioning

confidence: 99%

Section: Re R D Vmentioning

confidence: 99%

Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips

Cao,

Liu,

Zhang

et al. 2024

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

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Direct numerical simulation of Taylor–Couette flow with vertical asymmetric rough walls

Xu,

Su,

Lan

et al. 2023

J. Fluid Mech.

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Direct numerical simulations are performed to explore the effects of the rotating direction of the vertically asymmetric rough wall on the transport properties of Taylor–Couette (TC) flow, up to a Taylor number of ${Ta} = 2.39\times 10^{7}$ . It is shown that, compared with the smooth wall, the rough wall with vertical asymmetric strips can enhance the dimensionless torque ${Nu}_{\omega }$ . More importantly, at high Ta, clockwise rotation of the inner rough wall (where the fluid is sheared by the steeper slope side of the strips) results in a significantly greater torque enhancement compared to counter-clockwise rotation (where the fluid is sheared by the smaller slope side of the strips), due to the larger convective contribution to the angular velocity flux. However, the rotating direction has a negligible effect on the torque at low Ta. The larger torque enhancement caused by the clockwise rotation of the vertically asymmetric rough wall at high Ta is then explained by the stronger coupling between the rough wall and the bulk, attributed to the larger biased azimuthal velocity towards the rough wall at the mid-gap of the TC system, the increased turbulence intensity manifested by larger Reynolds stress and a thinner boundary layer, and the more significant contribution of the pressure force on the surface of the rough wall to the torque.

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Combined effect of cavitation and multi-scale texture on the bearing properties of seawater-lubricated friction pair

Wang,

Dai,

et al. 2023

Physics of Fluids

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To explore the tribological properties of a seawater-lubricated friction pair, the influence of cavitation and multi-scale texture on the load-carrying capacity is investigated under seawater lubrication conditions. In this paper, a numerical simulation method is proposed to reveal the influence mechanism of cavitation on the load-carrying capacity, and the simulation results are verified by experiments. The results show that cavitation, wedge action, and the vortex flow effect are the main mechanisms responsible for affecting the load-carrying capacity. Cavitation is not always advantageous for the load-carrying capacity. The results indicate that cavitation enhances the load-carrying capacity when the velocity is between 5 and 10 m/s. However, the cavitation effect shows a negative effect with a velocity exceeding 10 m/s. In three different scales of surface textures, the load-carrying capacity of the millimeter-scale texture is the highest, followed by the cross-scale texture and the micrometer-scale texture. The load-carrying capacity of the millimeter-scale texture is almost 10 times that of the micrometer-scale texture. Furthermore, regardless of the texture scale, a texture with a high depth-to-diameter ratio (H = 1) always exhibits a higher load-carrying capacity at low speeds (V < 10 m/s).

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Effect of micro-grooves on drag reduction in Taylor–Couette flow

Cited by 6 publications

References 45 publications

Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips

Water Impalement Resistance and Drag Reduction of the Superhydrophobic Surface with Hydrophilic Strips

Direct numerical simulation of Taylor–Couette flow with vertical asymmetric rough walls

Combined effect of cavitation and multi-scale texture on the bearing properties of seawater-lubricated friction pair

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