scholarly journals Drag Reduction Mechanism of Viscoelastic Slick-Water Fracturing Fluid in Tortuous and Rough Fractures

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhiyu Liu ◽  
Fan Fan ◽  
Donghang Zhang ◽  
Yang Li ◽  
Yuan Li ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Drag Reduction ◽  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Rule ◽  
Mechanism Analysis ◽  
Reduction Mechanism ◽  
Fracturing Fluid ◽  
Factors Affecting

Slick-water can effectively reduce the flow drag of fracturing fluid. Many studies have focused on the drag reduction performance of slick-water in wellbore and perforation, but there has been little research on drag reduction characteristics in fracture flow. In this paper, a new visualization experiment system is used to simulate real fracture. The fracture surface is produced through actual triaxial hydraulic fracturing and is copied by a three-dimensional printer using resin material to maintain its shape feature. In comparing the experimental results, it was found that the main factors affecting drag reduction in a fracture are the relative molecular weight and the added concentration. Unlike the flow rule of the drag reducer in a pipeline, when the concentration is greater than 0.10%, a negative DR effect begins to appear. The influence of molecular weight is related to the flow stage; the increasing of molecular weight causes a reduction in DR effect when the flow rate is 0.24 m/s. However, the flow rate exceeds 0.5 m/s; drag reducers with higher molecular weight demonstrate better drag reduction performance. The drag reduction mechanism analysis in fractures was obtained from visualization observations, and the flow characteristics of fluid were characterized by using tracking particles. Drag reduction effect occurs mainly on the surface of the fractures in contrast to near the centre of the flow channel. This research can provide a reference for the experimental study on drag reduction in fractures and is of great significance to the optimization and improvement of drag reducing agent.

scholarly journals Analysis and Optimization of Truck Windshield Defroster

2020 ◽  
Vol 10 (16) ◽  
pp. 5671
Author(s):  
Zhilong He ◽  
Xide Qu ◽  
Lantian Ji ◽  
Weifeng Wu ◽  
Xiaolin Wang
Keyword(s):  
Main Part ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Distribution ◽  
Medium Size ◽  
Average Pressure ◽  
Factors Affecting ◽  
Guide Plate ◽  
Simulation Results ◽  
Major Factors

Frosting and fogging of automobile windshields is a common problem that emerges in daily driving. It is important and essential to quickly and completely defrost the windshield for safety purposes. In this study, a three-dimensional mathematical model was applied to investigate the flow distribution and flow characteristics on the windshield of a medium-size Model N800 truck. The simulation results were first compared with experimental data. The results showed that the simulation model could reliably predict the defrosting performance on the windshield. This model was then used to optimize the design of the defrosting duct that comprised the main part of the defroster. It was found that the guide plate and outlet position of the defrosting duct were the two major factors affecting the defrosting performance. Therefore, the guide plate was first optimized and the defrosting performance was analyzed. The results showed that the average pressure loss dropped by 21.56%, while the defrosting efficiency at the front white zone was improved to 89%. The position of the outlet of the airflow was further studied. The results showed that the defrosting efficiency at the front zone could be further improved to 99%.

scholarly journals Analysis of Unsteady Pressure Fluctuation in a Semi-Open Cutting Pump

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3657
Author(s):  
Weidong Cao ◽  
Jiayu Mao ◽  
Wei Li
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Lower Plate ◽  
Pressure Distributions ◽  
Axial Forces ◽  
Blade Frequency

In order to understand the pressure fluctuation characteristics of a semi-open cutting pump, the three-dimensional unsteady flow fields were calculated. External and internal flow characteristics of four schemes with different relative angles between the rotary cutter and the impeller were studied. The pressure fluctuations in the lower plate, the upper plate, the clearance between the rotary cutter and the fixed cutter, the first section in volute and nearby parts of the tongue were all analyzed, which are all the places that pressure distributions are greatly affected by the static and dynamic interaction, and at the same time, the force on the impeller was also analyzed. The results show that the fluctuations at different positions change periodically; the main frequency is blade frequency. The amplitude of pressure fluctuation decreases from near the rotating part to far away, from near the tongue to far from the tongue. Due to the influence of both impeller and rotary cutter, the pressure fluctuation on the lower plate is the largest. The pressure fluctuation is affected by flow rate, the larger the flow rate, the greater the pressure fluctuation. The radial and axial forces of the impeller change periodically with time, and the number of wave peaks and wave valleys is the same as the number of blades.

A tracer dispersion study of the drag-reduction effect in a turbulent pipe flow

1971 ◽  
Vol 47 (2) ◽  
pp. 209-230 ◽  
Author(s):  
A. W. Bryson ◽  
Vr. Arunachalam ◽  
G. D. Fulford
Keyword(s):  
Molecular Weight ◽  
Drag Reduction ◽  
Pipe Flow ◽  
Viscous Sublayer ◽  
Turbulent Pipe Flow ◽  
Reduction Mechanism ◽  
Response Curves ◽  
Pipe Flows ◽  
Tracer Dispersion ◽  
Reduction Effect

Remarkable differences in dispersion of a tracer material injected into turbulent pipe flows of water and water containing as little as 2·5 parts per million by weight of a soluble high-molecular-weight drag-reducing polyoxyethylene additive have been measured. Analysis of the tracer response curves in terms of a simple one-parameter model shows that the observed results are compatible with a drag-reduction mechanism based on thickening of the viscous sublayer adjoining the wall. Other experiments, reported briefly, suggest that polymer adsorption on to the wall is responsible for this thickening.

scholarly journals Numerical Simulation of Full-Scale Three-Dimensional Fluid Flow in an Oscillating Reactor

2021 ◽  
Vol 9 ◽  
Author(s):  
Houjun Gong ◽  
Mengqi Wu
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Flow Field ◽  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Full Scale ◽  
Variation Patterns ◽  
Oscillating Motion ◽  
Resistance Coefficients

Marine reactors are subjected to additional motions due to ocean conditions. These additional motions will cause large fluctuation of flow rate and change the coolant flow field, making the system unstable. Therefore, in order to understand the effect of oscillating motion on the flow characteristics, a numerical simulation of fluid flow is carried out based on a full-scale three-dimensional oscillating marine reactor. In this study, the resistance coefficients of the lattice, rod buddle and steam generator are fitted, and the distribution of flow rate, velocity as well as pressure in different regions is investigated through the standard model. After additional oscillation is introduced, the flow field in an oscillating reactor is presented and the effect of oscillating angle and elevation on the flow rate is investigated. Results show that the oscillating motion can greatly change the flow field in the reactor; most of the coolant circulates in the downcommer and lower head with only a small amount of coolant entering the core; the flow fluctuation period is consistent with the oscillating period, and the flow variation patterns under different oscillating conditions are basically the same; since the flow amplitude is related to oscillating speed, the amplitude of flow rate rises when decreasing the maximum oscillating angle; the oscillating elevation has little effect on the flow rate.

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%.

scholarly journals Hydrodynamic Flow Characteristics in an Internally Circulating Fluidized Bed Gasifier

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
J. P. Simanjuntak ◽  
K. A. Al-attab ◽  
Z. A. Zainal
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Circulating Fluidized Bed ◽  
Draft Tube ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydrodynamic Flow ◽  
Orifice Diameter ◽  
Circulation Rate ◽  
Cfd Models

In this paper, the hydrodynamic flow inside an internally circulating fluidized bed (ICFBG) was characterized using experimental and three-dimensional computational fluid dynamics (CFD) models. Eulerian-Eulerian model (EEM) incorporating the kinetic theory of granular flow was implemented in order to simulate the gas–solid flow. A full-scale plexiglass cold flow experimental model was built to verify simulation results prior to the fabrication of the gasifier. Six parameters were manipulated to achieve the optimum design geometry: fluidization flow rate of the draft tube (Qdt), aeration flow rate of the annulus (Qan), initial bed static height (Hbs), draft tube height (Hdt), draft tube diameter (Ddt), and orifice diameter (Dor). The investigated parameters showed strong effect on the particle flow characteristics in terms of the pressure difference (ΔP) and solid circulation rate (Gs). The predicted results by simulation for the optimum case were in close agreement with experimental measurements with about 5% deviation. The results show that the ICFBG operated stably with the maximum Gs value of 86.6 kg/h at Qdt of 350 LPM, Qan of 150 LPM, Hbs of 280 mm, Hdt of 320 mm, Ddt of 100 mm, and Dor of 20 mm.

Study on drag reduction mechanism of rotating disk with micro-grooves

2017 ◽  
Vol 232 (6) ◽  
pp. 660-673
Author(s):  
Suping Wen ◽  
Wenbo Wang ◽  
Jian Wang
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Flow Characteristics ◽  
Rotating Disk ◽  
Viscous Sublayer ◽  
Dual Function ◽  
Reduction Mechanism ◽  
Smooth Disk ◽  
Reduction Effect ◽  
Interaction Phenomenon

This paper presents the drag reduction mechanism of a rotating disk with micro-grooves. The flow characteristics of the micro-grooved disk at various rotating Reynolds numbers are investigated using experiments and large-eddy simulations. The results show that fluid in the gap between the disks undergoes circumferential movement, but fluid within the micro-grooves undergoes radial movement because of the dual function of wall rejection and boundary layer blockage. As a result, fluid within the micro-grooves moves very slowly and quietly. Hence, quiet and slow-moving fluid within the micro-grooves increases the thickness of the viscous sublayer and recedes mixed layer and suppresses the unstable motion. The mean relative velocity gradient of the immersed surface on the grooved disk becomes much lower than that of a smooth disk, and the contact area between the walls and the high-speed fluid is diminished. An interaction phenomenon between the micro-grooves and the gap could be discovered due to the micro-groove unenclosed structure. The interaction phenomenon makes the quiet fluid within the micro-grooves also suppresses the outside flow. Accordingly, a micro-grooved rotating disk has an obvious drag reduction effect compared with a rotating smooth disk.

Simulation of Drag Reduction Mechanism of the Wing Tip

2014 ◽  
Vol 602-605 ◽  
pp. 295-298 ◽  
Author(s):  
Xiao Lei Liu ◽  
Xue Wei Liu ◽  
Li Min Song ◽  
Dun Jin ◽  
Yuan Kai Li
Keyword(s):  
Optimal Design ◽  
Drag Reduction ◽  
Three Dimensional ◽  
Reduction Mechanism ◽  
Post Processing ◽  
Processing Software ◽  
Dimensional Simulation ◽  
Wing Tip

In this paper, the international common CFD software were installed on the flat three-dimensional optimal design wing tip and winglet wing for three-dimensional simulation, and use the results post-processing software post-processing.

Numerical Investigations on Leakage Performance of the Rotating Labyrinth Honeycomb Seal

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Jun Li ◽  
Shengru Kong ◽  
Xin Yan ◽  
Shinnosuke Obi ◽  
Zhengping Feng
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Cell Diameter ◽  
Leakage Flow ◽  
Steam Turbines ◽  
Honeycomb Seal ◽  
Leakage Flow Rate ◽  
Honeycomb Cell

Three-dimensional Reynolds-averaged Navier–Stokes (RANS) solutions from CFX were utilized to investigate the leakage flow characteristics in the labyrinth honeycomb seal of steam turbines. At first, the accuracy and reliability of the utilized RANS approach was demonstrated using the published experimental data of the honeycomb seal. It showed that the utilized numerical method has sufficient precision to predict the leakage performance in seals. Then a range of sealing clearances, cell diameters, cell depths, rotation speeds, and pressure ratios were investigated to determine how these factors affect the leakage flow rate of the labyrinth honeycomb seal. The computed leakage flow rate increased with increasing sealing clearance and pressure ratios. Furthermore, the results show that the studied labyrinth honeycomb seal has the optimum sealing performance in the case of honeycomb cell diameter equals labyrinth step width, and the ratio of the honeycomb cell depth to honeycomb cell diameter is 0.93 under the designed condition. The flow pattern of each case is also illustrated to describe the leakage flow characteristics in labyrinth honeycomb seals.

scholarly journals Numerical Research of Pump-as-Turbine Performance with Synergy Analysis

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1031
Author(s):  
Zheng Cao ◽  
Jianqiang Deng ◽  
Linkun Zhao ◽  
Lin Lu
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Operating Conditions ◽  
Field Analysis ◽  
Sensitivity Index ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Research ◽  
Hydraulic Devices

The wide use of pumps and turbines has significant value in energy conservation and utilization. In this work, a three-dimensional Computational Fluid Dynamics (CFD) model and a one-dimensional theoretical model of a Pump as Turbine (PAT) were established. On this basis, the correlation between pressure and velocity was quantitatively investigated by a proposed sensitivity index (SPV). A synergy field analysis was then applied to evaluate the flow characteristics of a pump and PAT, providing a perspective from the mechanism of the energy transfer enhancement for hydraulic devices. Moreover, the hydraulic and synergy performances of PAT were studied under various operating conditions. The results show that the minimum SPV is obtained in the impeller. With increasing flow rate, the SPV of the PAT generally increases, and the synergy angle of the impeller surface increases as well. A strong disordered synergy field is observed in regions of the blade leading edge, trailing edge, and volute tongue. The variations in efficiency and head with flow rate showed similar trends, respectively, with the synergy angle of the outlet and the mid-plane. This study provides an analytical method for quantitative evaluation of flow synergy characteristics, and it supplies a basis for further design improvement of the pump and PAT.

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