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1 – 10 of over 2000
Article
Publication date: 20 February 2023

Kaiyao Zhao, Minggao Tan, Xianfang Wu, Chen Shao and Houlin Liu

The purpose of the paper is to disclose the effect of the relative position (d) between the impeller and non-vane cavity on the hydraulic performance and unsteady characteristics…

Abstract

Purpose

The purpose of the paper is to disclose the effect of the relative position (d) between the impeller and non-vane cavity on the hydraulic performance and unsteady characteristics of vortex pump.

Design/methodology/approach

Three groups of vortex pump models with different impeller installation positions were analyzed and studied by combining experimental and CFD (Computational Fluid Dynamics) numerical calculations.

Findings

The steady numerical results show that as the width (d) of the impeller moves into the non-vane cavity increases, the proportion of circulation flow in the non-vane cavity is reduced and both the pump head and efficiency are on the rise. The unsteady numerical results and the Enstrophy analysis show that the dynamic and static interference between the circulation flow and the volute tongue is the main reason for the pressure pulsation with a frequency of 2fn in the vortex pump. With the increase of the d value, the dynamic and static interference between the circulation flow and the volute tongue is enhanced. The pulsation amplitude at the volute tongue of the d = 16.5 mm model increases about six times compared with the d = 0 mm model; the distribution of the vortex core in the non-vane cavity is closely related to the position of the impeller, and the peak of the Enstrophy of the circulation flow vortex belt always appears at the top of the impeller.

Originality/value

The research results provide a theoretical foundation for the optimization and improvement of the vortex pump.

Details

Engineering Computations, vol. 40 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 18 April 2017

Lingjiu Zhou, Meng Liu, Zhengwei Wang, Demin Liu and Yongzhi Zhao

This study analyzes the blade channel vortices inside Francis runner with a particular focus on the identification of different types of vortices and their causes.

Abstract

Purpose

This study analyzes the blade channel vortices inside Francis runner with a particular focus on the identification of different types of vortices and their causes.

Design/methodology/approach

A single-flow passage of the Francis runner with refined mesh and periodic boundary conditions was used for the numerical simulation to reduce the computational resource. The steady-state Reynolds-averaged Navier–Stokes equations closed with the k-ω shear–stress transport (SST) turbulence model were solved by ANSYS CFX to determine the flow field. The vortices were identified by the second largest eigenvalue of velocity.

Findings

Four types of vortices were identified inside the runner. Three types were related to the inlet flow. The last one (Type 4) was caused by the reversed flow near the runner crown and had the lowest pressure inside the core near the runner outlet. Thus, in the blade channel vortex inception line, Type 4 vortex would appear earlier than the other three ones. Besides, the Type 4 vortex emerged from the crown and shed toward the blade-trailing edge. And its location moved from near the crown down to near the band when the unit speed increased or unit discharge decreased.

Research limitations/implications

Although the refined mesh was used and the main vortices in the Francis runner were well predicted, the current mesh is not enough to accurately predict the lowest pressure in the channel vortex core.

Practical/implications

This knowledge is instructive in the runner blade design and troubleshooting related to the channel vortex.

Originality/value

This study gives an overview of the main observed blade channel vortices and their causes, and points out the important role the reversed flow plays in the formation of blade channel vortices. This knowledge is instructive in the runner blade design and troubleshooting related to blade channel vortices.

Details

Engineering Computations, vol. 34 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 29 July 2014

Haiming Huang, Guo Huang, Xiaoliang Xu and Weijie Li

Relevant analyses are presented on the base of the compressible vortex method for simulating the development of two or three co-rotating vortices with different characteristic…

Abstract

Purpose

Relevant analyses are presented on the base of the compressible vortex method for simulating the development of two or three co-rotating vortices with different characteristic Mach numbers. The paper aims to discuss this issue.

Design/methodology/approach

In addition to having vorticity and dilatation properties, the vortex particles also carry density, enthalpy, and entropy. Taking co-rotating vortices in two-dimensional unsteady compressible flow for an example, truncation of unbounded domains via a nonreflecting boundary condition was considered in order to make the method computationally efficient.

Findings

For two identical vortices, the effect of the vortex Mach number on merging process is not evident; if two vortices have the same circulation rather than different radiuses, the vorticity and dilatation fields of the vortex under a vortex Mach number will be absorbed by the vortex under a higher vortex Mach number. For three vortices, if the original arrangement of the vortices is changed, the evolvement of the vorticity and dilatation fields is different.

Originality/value

The paper reveals new mechanism of the three co-rotating vortices by a feasible compressible vortex method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 7 March 2016

Jing Yang, Lingjiu Zhou and Zhengwei Wang

The vortex ropes in draft tube of Francis turbine always cause fluctuation and vibration, which consequently threaten the safety and stability of hydro turbines. The purpose of…

Abstract

Purpose

The vortex ropes in draft tube of Francis turbine always cause fluctuation and vibration, which consequently threaten the safety and stability of hydro turbines. The purpose of this paper is to use a cavitation flow computational method to simulate spiral vortex ropes under part load conditions and columnar vortex ropes under high-load conditions in draft tube. The unsteady cavitating flow characteristics in draft tube and its interaction with runner cavitation were analyzed.

Design/methodology/approach

The calculation method was verified by cavitation simulation around a 3D hydrofoil. The results show that the Large Eddy Simulation (LES) turbulence model with the Zwart-Gerber-Blemari cavitation model have comparative advantage in cavitation simulations whether from capture of cavity shape or prediction of pressure changes. So it was chosen to simulate the two-phase cavitation flow in Francis turbine. The boundary conditions for inlet and outlet were set to inlet total pressure and outlet static pressure. The finite volume method with the central difference was adopted to discretize the equations.

Findings

The calculated Thoma number agreed well with the experimental data. The vortex rope diameter and length increased with the cavitation development for both of the two types of vortex ropes conditions. The maximum peak-to-peak values of pressure pulsations located in the draft tube elbow part under all of the Thoma numbers conditions. Under spiral vortex rope conditions, the pressure pulsation in the same section of draft tube cone show obviously phase shift. The vortex rope affects the development of runner cavitation, which induces the symmetric and axisymmetric cavitation region in the suction side of blades for spiral and columnar vortex rope condition, respectively.

Research limitations/implications

The mesh independence had been checked only in non-cavitation flow; in addition, the mesh density did not well satisfy the requirements of LES due to the limitations of computing power. The higher mesh density on a simplified model with one blade flow path and the entire draft tube may be helpful for obtaining more precise results.

Originality/value

The spiral and columnar vortex ropes in a Francis turbine were compared and analyzed. The annular hydraulic jump appeared in the columnar vortex rope conditions has little effects on the pressure pulsations. The uneven flow field caused by spiral vortex led to the asymmetric cavitation development.

Details

Engineering Computations, vol. 33 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 22 August 2022

Gizem Karakan Günaydın

The paper aims to provide an investigation about the effect of some selected production parameters such as core yarn type, sheath sliver type and total yarn count factors on core…

Abstract

Purpose

The paper aims to provide an investigation about the effect of some selected production parameters such as core yarn type, sheath sliver type and total yarn count factors on core spun vortex yarns' evenness, imperfection and tensile properties. Hence it is aimed to contribute to the literature in vortex spinning where there are limited works related to core-spun vortex spinning.

Design/methodology/approach

The paper evaluates the effect of core yarn type, sheath sliver type and total yarn count factors on yarn evenness, imperfections, hairiness and tensile properties. Completely randomised three-factor analysis of variance (ANOVA) was conducted in order to evaluate the effect of core yarn type, sheath sliver type and linear yarn density on core spun vortex yarns' evenness, imperfection and tensile properties at significance level of 0.05. SNK tests were also performed for observing the means of each parameter. Correlation analysis was also conducted to reveal some relationships between yarn evenness and yarn tensile properties.

Findings

In this paper, significant factors related to some production parameters affecting the core-spun vortex yarns' evenness, imperfection, hairiness and tensile properties were found.

Originality/value

There are limited works related to effect of selected production parameters on yarn evenness, Imperfections and Tensile Properties of Hybrid Vortex Yarns.

Details

International Journal of Clothing Science and Technology, vol. 34 no. 6
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 20 January 2023

Nishchay Tiwari, Pawel Flaszynski, Thanushree Suresh and Oskar Szulc

The purpose of this paper is to investigate and compare the effects of rod and vane-type vortex generators for wind turbine applications. In large wind turbine rotors, an attached…

Abstract

Purpose

The purpose of this paper is to investigate and compare the effects of rod and vane-type vortex generators for wind turbine applications. In large wind turbine rotors, an attached flow at all sections along the span direction is difficult to achieve which leads to an increase in aerodynamic losses, noise generation, and fatigue stress. Therefore, flow control strategies such as vortex generators (VGs) are beneficial to improve performance.

Design/methodology/approach

The benefits of the application of rod-type vortex generators (RVGs) to control flow separation on a wind turbine airfoil are assessed numerically using computational fluid dynamics (CFD). The validation of the computational model is conducted against the experimental data available for the DU96-W-180 wind turbine airfoil equipped with 44 RVGs. In addition, a revised wind tunnel angle of attack (AoA) calibration procedure (based on CFD) is proposed that is applicable for separated flows. A comparison of the RVGs to the conventional vane-type vortex generators (VVGs) is presented for inflow velocity of 30 m/s and AoA leading to significant flow separation. A parametric evaluation of the geometric characteristics of both types of VGs is conducted to quantify the generated streamwise vortices.

Findings

The comparison of the induced flow structures and aerodynamic efficiency enhancements proves that RVGs may be used as an alternative to the more conventional VVGs applied on wind turbine blades for boundary layer separation control.

Originality/value

A new type of VG (rod) has been investigated and compared against conventional VG (vanes) for wind turbine applications.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 4 September 2017

Frank Holzäpfel

In this study, 12 potential wake vortex encounters that were reported at a major European airport have been investigated. Because almost all encounters occurred in ground…

Abstract

Purpose

In this study, 12 potential wake vortex encounters that were reported at a major European airport have been investigated. Because almost all encounters occurred in ground proximity, most pilots conducted a go-around. The primary purpose of this study is to discriminate between incidents caused by wake vortices or rather by effects like wind shear or turbulence. Detailed knowledge of real-world encounter scenarios and identification of worst-case conditions during the final approach constitute highly relevant background information to assess the standard scenario used for the definition of revised wake turbulence separations.

Design/methodology/approach

Wake vortex predictions using the probabilistic two-phase wake vortex model (P2P) are used to investigate the incidents in detail by using data from the flight data recorder, meteorological instrumentation at the airport and numerical weather prediction.

Findings

In the best documented cases, the flight tracks through the vortices could be reconstructed in good agreement with wake vortex predictions and recorded aircraft reactions. Out of the eight plausible wake vortex encounters, five were characterized by weak crosswinds below 1.5 m/s combined with tailwinds. This meteorological situation appears favourable for encounters because, on the one hand, weak crosswinds may compensate the self-induced lateral propagation of the upwind vortex, such that it may hover over the runway directly in the flight path of the following aircraft. On the other hand, tailwinds limit the propagation of the so-called end effects caused by the breakdown of lift during touchdown.

Practical implications

The installation of plate lines beyond the runway tails may improve safety by reducing the number of wake vortex encounters.

Originality/value

The conducted investigations provide high originality and value for both science and operational application.

Details

Aircraft Engineering and Aerospace Technology, vol. 89 no. 5
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 1 February 1989

Martin J. Downie and Peter Bettess

A simple discrete vortex program written in the Occam language for implementation on transputers is presented. The programming methodology and logic are described, with an…

Abstract

A simple discrete vortex program written in the Occam language for implementation on transputers is presented. The programming methodology and logic are described, with an emphasis on the use of parallel features. Listings of procedures discussed in the text are given.

Details

Engineering Computations, vol. 6 no. 2
Type: Research Article
ISSN: 0264-4401

Article
Publication date: 8 May 2018

Fernando Tejero Embuena, Piotr Doerffer, Pawel Flaszynski and Oskar Szulc

Helicopter rotor blades are usually aerodynamically limited by the severe conditions present in every revolution: strong shock wave boundary layer interaction on the advancing…

Abstract

Purpose

Helicopter rotor blades are usually aerodynamically limited by the severe conditions present in every revolution: strong shock wave boundary layer interaction on the advancing side and dynamic stall on the retreating side. Therefore, different flow control strategies might be applied to improve the aerodynamic performance.

Design/methodology/approach

The present research is focussed on the application of passive rod vortex generators (RVGs) to control the flow separation induced by strong shock waves on helicopter rotor blades. The formation and development in time of the streamwise vortices are also investigated for a channel flow.

Findings

The proposed RVGs are able to generate streamwise vortices as strong as the well-known air-jet vortex generators. It has been demonstrated a faster vortex formation for the rod type. Therefore, this flow control device is preferred for applications in which a quick vortex formation is required. Besides, RVGs were implemented on helicopters rotor blades improving their aerodynamic performance (ratio thrust/power consumption).

Originality/value

A new type of vortex generator (rod) has been investigated in several configurations (channel flow and rotor blades).

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 25 January 2021

Faezeh Nejati Barzoki, Ghanbar Ali Sheikhzadeh, Morteza Khoshvaght Aliabadi and Ali Akbar Abbasian Arani

The purpose of this paper is to investigate thermohydraulic characteristics of turbulent flow of water (4,000 = Re = 10,000) in a rectangular channel equipped with perforated…

Abstract

Purpose

The purpose of this paper is to investigate thermohydraulic characteristics of turbulent flow of water (4,000 = Re = 10,000) in a rectangular channel equipped with perforated chevron plat-fin (PCPF) with different vortex generators (VGs) shapes.

Design/methodology/approach

First, three general shapes of VGs including rectangular, triangular and half circle, are compared to each other. Then, the various shapes of rectangular VGs, (horizontal, vertical and square) and triangular VGs, (forward, backward and symmetric) are evaluated. To comprehensively evaluate the thermohydraulic performance of the PCPF with various VG shapes, the relationship between the Colburn factor and the friction factor (j/f) is presented, then a performance index (η) is applied using these factors.

Findings

Results show that the enhanced models of the PCPF, which are equipped with VGs, have higher values of j/f ratio and η as compared with the reference model (R). Further, the half-circle VG with the lowest pressure drop values (about 2.4% and 4.9%, averagely as compared with the S and ST vortex generators), shows the highest thermohydraulic performance among the proposed shapes. The maximum of performance index of 1.14 is found for the HC vortex generator at Re = 4,000. It is also found that the square and forward triangular VGs, have the best thermohydraulic performance among the rectangular and triangular VGs respectively and the highest performance index of 1.13 and 1.11 are reported for these VGs.

Originality/value

The thermohydraulic performance of the PCPF with different vortex generators VGs shapes have been investigated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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