scholarly journals Experimental Study on Drag Reduction Characteristics of Bionic Earthworm Self-Lubrication Surface

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Guomin Liu ◽  
Xueqiao Wu ◽  
Meng Zou ◽  
Yuying Yan ◽  
Jianqiao Li
Keyword(s):  
Drag Reduction ◽  
Flow Rate ◽  
Experimental Testing ◽  
Reduction Rate ◽  
Normal Pressure ◽  
Secondary Effects ◽  
Quadratic Regression ◽  
Regression Test ◽  
Reduction Effect ◽  
Reduction Characteristics

In the present study, a coupling bionic method is used to study the drag reduction characteristics of corrugated surface with lubrication. In order to test the drag reduction features, bionic specimen was prepared inspired by earthworm surface and lubrication. Based on the reverse engineering method, nonsmooth curve of earthworm surface was extracted and the bionic corrugated sample was designed, and the position of lubrication hole was established by experimental testing. The lubricating drag reduction performance, the influence of normal pressure, the forward velocity, and the flow rate of lubricating fluid on the forward resistance of the bionic specimens were analyzed through a single factor test by using the self-developed test equipment. The model between the forward resistance and the three factors was established through the ternary quadratic regression test. The results show that the drag reduction effect is obvious, the drag reduction rate is 22.65% to 34.89%, and the forward resistance decreases with the increase of the forward velocity, increases with the increase of the normal pressure, and decreases first and then becomes stable with the increase of flow rate of lubricating fluid. There are secondary effects on forward resistance by the three factors, and the influencing order is as follows: normal pressure>flow rate of lubricating fluid>forward velocity.

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.

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.

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].

Influence of Jet Hole Configuration on Drag Reduction of Bionic Jet Surface

2013 ◽  
Vol 461 ◽  
pp. 725-730 ◽  
Author(s):  
Yun Qing Gu ◽  
Jing Ru ◽  
Zhao Gang ◽  
Zhao Yuan Li ◽  
Wen Bo Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Drag Reduction ◽  
Reduction Rate ◽  
Experimental Tests ◽  
Isosceles Triangle ◽  
Hole Configuration ◽  
Field Velocity ◽  
Jet Velocity ◽  
Reduction Characteristics

According to the jet hole configuration mode of bionic jet surface and its influence on the drag reduction, as the basic form of jet hole configuration is the isosceles triangle elements, so this was used to establish the computational model of jet hole configuration. In this case, the height and base of the triangles were considered as variable. The SST k-ω turbulence model was used to simulate and research the drag reduction characteristics of bionic jet surface in different configuration modes of jet holes at the main flow field velocity value of 20m/s and the jet velocity value of 0.4~2.0m/s. Also the influence of different configurations of height and base on drag reduction characteristics of bionic jet surface was studied, which got the optimum size of jet hole configuration. Results show that in triangle configuration elements, the drag reduction characteristics of bionic jet surface can be influenced by the jet hole of different configurations of height and base; the drag reduction of bionic jet surface reaches the peak of 32.74% at 8mm height, 11mm base, and the jet velocity value of 2.0m/s. At the same flow field velocity, the drag reduction rate results achieved by experimental tests and by numerical simulation were changing consistently and were found same, which verifies correctness of numerical simulation results.

scholarly journals Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 377 ◽  
Author(s):  
Yuanzhe Li ◽  
Zhe Cui ◽  
Qiucheng Zhu ◽  
Srikanth Narasimalu ◽  
Zhili Dong
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Chemical Etching ◽  
Flow Resistance ◽  
Reduction Rate ◽  
Low Flow ◽  
Rolling Angle ◽  
Standard Design ◽  
Reduction Effect ◽  
Nanoscale Roughness

A fluoropolyurethane-encapsulated process was designed to rapidly fabricate low-flow resistance surfaces on the zinc substrate. For the further enhancement of the drag-reduction effect, Cu2+-assisted chemical etching was introduced during the fabrication process, and its surface morphology, wettability, and flow-resistance properties in a microchannel were also studied. It is indicated that the zinc substrate with a micro-nanoscale roughness obtained by Cu2+-assisted nitric acid etching was superhydrophilic. However, after the etched zinc substrate is encapsulated with fluoropolyurethane, the superhydrophobic wettability can be obtained with a contact angle of 154.8° ± 2.5° and a rolling angle of less than 10°. As this newly fabricated surface was placed into a non-standard design microchannel, it was found that with the increase of Reynolds number, the drag-reduction rate of the superhydrophobic surface remained basically unchanged at 4.0% compared with the original zinc substrate. Furthermore, the prepared superhydrophobic surfaces exhibited outstanding reliability in most liquids.

LDV Measurement of Turbulent Pipe Flow With Traveling Wavy Elastic Wall for Drag Reduction

2019 ◽  
Author(s):  
Seiya Nakazawa ◽  
Takaaki Shimura ◽  
Akihiko Mitsuishi ◽  
Kaoru Iwamoto ◽  
Akira Murata
Keyword(s):  
Drag Reduction ◽  
Pipe Flow ◽  
Reduction Rate ◽  
Streamwise Velocity ◽  
Turbulent Pipe Flow ◽  
Deformation Control ◽  
Wall Deformation ◽  
Maximum Drag Reduction ◽  
Reduction Effect ◽  
Ldv Measurement

Abstract Drag reduction effect by traveling wavy wall deformation control in turbulent pipe flow was experimentally investigated. From the visualization, we confirmed the downstream traveling wave although it was not uniform in the circumferential direction. When the frequency is 110 Hz, the wall deformation amplitude and the wavelength indicated that the effective values for drag reduction. The wavespeed is approximately effective values for drag reduction. As a result, the maximum drag reduction rate of 6.8 % is obtained. The result of a LDV measurement shows that the mean streamwise velocity gradient decreased near the wall by the control, which leads to drag reduction.

Numerical Research about Drag-Reduction Characteristic of Riblet Structure on Aerofoil Blade of Centrifugal Fan

2013 ◽  
Vol 655-657 ◽  
pp. 105-108 ◽  
Author(s):  
Song Ling Wang ◽  
Rui Rong ◽  
Xiao Fei Hao
Keyword(s):  
Drag Reduction ◽  
Smooth Surface ◽  
Design Flow ◽  
Wall Region ◽  
Centrifugal Fan ◽  
Mean Velocity ◽  
Numerical Research ◽  
Reduction Effect ◽  
Fan Blade ◽  
Reduction Characteristics

The drag reduction characteristics of riblet structure on aerofoil blade of centrifugal fan were numerically simulated with Fluent. Riblet structure still has good drag reduction effect on the surface of aerofoil blade. The best drag reduction effect has been gotten with appropriate riblet structure size, with the greatest drag reduction efficiency of 9.65%. And under the design flow of the fan, the drag can be reduced by 2.96%. The mean velocity of near-wall region on riblet surface has a significant increase than smooth surface. Turbulent kinetic energy and turbulent intensity are lower than smooth surface obviously, the drag reduction effect of riblet structure on aerofoil blade is verified. The present results can be used to provide a valuable reference for optimization of centrifugal fan blade modification.

Non-Smooth Surface Flow Drag Reduction Characteristics of Centrifugal Pump Impeller

2016 ◽  
Vol 24 ◽  
pp. 44-56
Author(s):  
Yun Qing Gu ◽  
Zheng Zan Shi ◽  
Jie Gang Mou ◽  
Hao Shuai Wang ◽  
Pei Jian Zhou
Keyword(s):  
Drag Reduction ◽  
Centrifugal Pump ◽  
Reduction Rate ◽  
Internal Flow ◽  
Surface Flow ◽  
Flow State ◽  
Pump Impeller ◽  
Wall Boundary Layer ◽  
Reduction Characteristics ◽  
Centrifugal Pump Impeller

In order to improve the efficiency of centrifugal pump, based on the bionics principle, established non-smooth surfaces of various groove structure on the centrifugal pump impeller. The internal flow field of it was numerically simulated through RNG k-ε turbulence model. Research the drag reduction characteristics of non-smooth impeller in different groove shape and arrangement. The results showed that the biggest drag reduction rate of centrifugal pump with non-smooth blades is about 6.22%. The blades of non-smooth unit can effectively inhibit the near wall boundary layer flow state, reduce the shear stress on blades wall, reduce the internal fluid turbulent degree of centrifugal pump, so that the fluid flow in centrifugal pump impeller is more stable, improve the efficiency of centrifugal pump.

Prediction of Drag Reduction Effect of Pulsating Control in Turbulent Pipe Flow by Machine Learning

2019 ◽  
Author(s):  
Wataru Kobayashi ◽  
Takaaki Shimura ◽  
Akihiko Mitsuishi ◽  
Kaoru Iwamoto ◽  
Akira Murata
Keyword(s):  
Machine Learning ◽  
Drag Reduction ◽  
Reduction Rate ◽  
Automatic Measurement ◽  
Turbulent Pipe Flow ◽  
Working Fluid ◽  
Circulation System ◽  
Validation Data ◽  
Acceleration And Deceleration ◽  
Reduction Effect

Abstract It has been widely expected that the pulsating control can reduce friction drag in various fluid systems. In order to maximize its effect, a prediction tool of drag reduction using pulsating control is required. The present study aims at the prediction of the drag reduction rate by machine learning. Multilayer perceptron (MLP) was applied as the machine learning method. Water was used as the working fluid. First, an automatic measurement system was constructed and drag reduction effect was evaluated by an experiment with various pulsation waveforms. The flow pulsation was generated by giving periodical acceleration and deceleration by a centrifugal pump in a closed circulation system. The bulk Reynolds number Reb ranges between 3400 and 3800. Next, the experiments were performed with over 5000 kinds of waveforms to make training and validation data for MLP. Within the data, the maximum drag reduction rate of 38.6% was observed. The friction coefficient Cf decreased during the acceleration period and increased during deceleration period. Finally, the drag reduction rate was predicted in three cases with different input parameters of MLP. The relationship between pulsation waveforms and the drag reduction effect was successfully predicted.

scholarly journals Investigation on drag reduction performance of pipeline with bioinspired microgrooved surface

2019 ◽  
Author(s):  
Weili Liu ◽  
Hongjian Ni ◽  
Peng Wang ◽  
Yi Zhou
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Pressure Loss ◽  
Fluid Transport ◽  
Fluid Dynamic ◽  
Reduction Rate ◽  
Orthogonal Analysis ◽  
Maximum Drag Reduction ◽  
Reduction Effect ◽  
Microgrooved Surface

Novel surface morphology of pipeline with transverse microgrooves was proposed for reducing the pressure loss of fluid transport. Numerical simulation and experimental research efforts were undertaken to evaluate the drag reduction performance of bionic pipeline. The computational fluid dynamic calculation, using SST κ-ω turbulent model, shown that the “vortex cushioning effect” and “driving effect” produced by the vortexes in the microgrooves were the main reason for the drag reduction. The shear stress of the microgrooved surface was reduced significantly owing to the decline of the velocity gradient; then bionic pipeline achieved drag reduction effect in the pipe and concentric annulus flow. The primary and secondary order of effect on the drag reduction and optimal microgroove geometric parameters were obtained by orthogonal analysis method. The comparative experiments were conducted in a water tunnel, and a maximum drag reduction rate of 3.21% was achieved. The numerical simulation and experimental results were cross-checked and consistent with each other to verify that the utilization of bionic theory to reduce the pressure loss of fluid transport is feasible. Results can provide theoretical guidance for the energy saving of pipeline transportation.

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