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1 – 10 of over 3000
Article
Publication date: 30 August 2022

Megan Burfoot, Nicola Naismith, Ali GhaffarianHoseini and Amirhosein Ghaffarianhoseini

Informed by acoustic design standards, the built environments are designed with single reverberation times (RTs), a trade-off between long and short RTs needed for different space…

Abstract

Purpose

Informed by acoustic design standards, the built environments are designed with single reverberation times (RTs), a trade-off between long and short RTs needed for different space functions. The novel intelligent passive room acoustic technology (IPRAT) has the potential to revolutionise room acoustics, thus, it is imperative to analyse and quantify its effect. IPRAT achieves real-time room acoustic improvement by integrating passive variable acoustic technology (PVAT) and acoustic scene classification (ASC). This paper aims to compare IPRAT simulation results with the AS/NZS 2107:2016 Australian/New Zealand recommended design acoustic standards.

Design/methodology/approach

In this paper 20 classroom environments are virtually configured for the simulation, multiplying 5 classrooms with 4 aural situations typical to New Zealand classrooms. The acoustic parameters RT, sound clarity (C50) and sound strength (G) are considered and analysed in the simulation. These parameters can be used to determine the effects of improved acoustics for both teacher vocal relief and student comprehension. The IPRAT was assumed to vary RT and was represented in the simulation by six different absorption coefficient spectrums.

Findings

The optimised acoustic parameters were derived from relationships between C50, RT and G. These relationships and optimal RTs contribute a unique database to literature. IPRAT’s advantages were discerned from a comparison of “current,” “attainable” and “optimised” acoustic parameters.

Originality/value

By quantifying the effect of IPRAT, it is understood that IPRAT has the potential to satisfy the key recommendations of professional industry standards (for New Zealand namely; AS/NZS 2107:2016 recommended design acoustic standards).

Details

Smart and Sustainable Built Environment, vol. 12 no. 5
Type: Research Article
ISSN: 2046-6099

Keywords

Article
Publication date: 31 July 2019

Hui Quan, Yi Chai, Rennian Li and Jianhui Guo

The special structure of the vortex pump contributes to its complex internal flow pattern. A type of horizontal 150WX-200-20 vortex pump is taken as a research subject to deeply…

Abstract

Purpose

The special structure of the vortex pump contributes to its complex internal flow pattern. A type of horizontal 150WX-200-20 vortex pump is taken as a research subject to deeply study the progression and distribution of flow pattern in its channel. To explain the mechanism of flow in this pump, numerical analysis of the whole flow and experiment have been conducted.

Design/methodology/approach

The authors studied and analyzed the distribution and evolution of flow pattern under different flow, such as circulating-flow, through-flow and other forms. Finally, a model of flow pattern in the vortex pump has been built, which has more perfectly fit the reality.

Findings

They are through-flow affected by circulating-flow, main and subsidiary circulating-flow, vortices between vanes and other vortices (or liquid impingement) in volute. Entering the pump, part of the flow stays in vanes and turn into vortices while the other goes into the front chamber. The flow that runs into the front chamber will be divided into two parts. One part will be collected by viscosity into a vortex rope when it passing through the interface between the impeller and the vaneless chamber, which closely relates to the circulating-flow, and the rest directly goes out of the field through the diffuser. Besides, a fraction of circulating-flow joins the through-flow when it goes through the section V and leaves the pump.

Originality/value

The research results build a theoretical foundation for working out the flow mechanism of the vortex pump, improving its efficiency and optimizing its hydraulic design.

Details

Engineering Computations, vol. 36 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 19 June 2021

Richard Hann and Tor Arne Johansen

The main purpose of this paper is to investigate the effects of icing on unmanned aerial vehicles (UAVs) at low Reynolds numbers and to highlight the differences to icing on…

Abstract

Purpose

The main purpose of this paper is to investigate the effects of icing on unmanned aerial vehicles (UAVs) at low Reynolds numbers and to highlight the differences to icing on manned aircraft at high Reynolds numbers. This paper follows existing research on low Reynolds number effects on ice accretion. This study extends the focus to how variations of airspeed and chord length affect the ice accretions, and aerodynamic performance degradation is investigated.

Design/methodology/approach

A parametric study with independent variations of airspeed and chord lengths was conducted on a typical UAV airfoil (RG-15) using icing computational fluid dynamic methods. FENSAP-ICE was used to simulate ice shapes and aerodynamic performance penalties. Validation was performed with two experimental ice shapes obtained from a low-speed icing wind tunnel. Three meteorological conditions were chosen to represent the icing typologies of rime, glaze and mixed ice. A parameter study with different chord lengths and airspeeds was then conducted for rime, glaze and mixed icing conditions.

Findings

The simulation results showed that the effect of airspeed variation depended on the ice accretion regime. For rime, it led to a minor increase in ice accretion. For mixed and glaze, the impact on ice geometry and penalties was substantially larger. The variation of chord length had a substantial impact on relative ice thicknesses, ice area, ice limits and performance degradation, independent from the icing regime.

Research limitations/implications

The implications of this manuscript are relevant for highlighting the differences between icing on manned and unmanned aircraft. Unmanned aircraft are typically smaller and fly slower than manned aircraft. Although previous research has documented the influence of this on the ice accretions, this paper investigates the effect on aerodynamic performance degradation. The findings in this work show that UAVs are more sensitive to icing conditions compared to larger and faster manned aircraft. By consequence, icing conditions are more severe for UAVs.

Practical implications

Atmospheric in-flight icing is a severe risk for fixed-wing UAVs and significantly limits their operational envelope. As UAVs are typically smaller and operate at lower airspeeds compared to manned aircraft, it is important to understand how the differences in airspeed and size affect ice accretion and aerodynamic performance penalties.

Originality/value

Earlier work has described the effect of Reynolds number variations on the ice accretion characteristics for UAVs. This work is expanding on those findings by investigating the effect of airspeed and chord length on ice accretion shapes separately. In addition, this study also investigates how these parameters affect aerodynamic performance penalties (lift, drag and stall).

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 5
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 14 November 2012

Xia Yan, Kai Zhang, Mudassir Nawaz and Sanchit Rai

In reservoir history matching the least square objective function is usually used to minimize the mismatch between the predicted production data and the observations. However, as…

Abstract

In reservoir history matching the least square objective function is usually used to minimize the mismatch between the predicted production data and the observations. However, as history matching is an ill-posed inverse problem with non-unique solutions, the reservoir model after calibrating may be far from the real geology model by only matching the production data. In order to solve this problem, a regularization method for reservoir history matching is implemented, in which not only the production data is matched, but prior geological information is also used to correct and update the current reservoir model so that the updated model will be consistent with the geologic model. In this paper, the simultaneous perturbation stochastic approximation method (SPSA) coupled with fast streamline simulation provides an effective method (SLSPSA) to optimize the objective function. As a stochastic approximation algorithm, SLSPSA can guarantee the convergence of the algorithm. Compared to the gradient-based algorithms, it avoids the massive calculation and storage for adjoint or sensitivity matrix. In the calculation process of algorithm, parallel computing is implemented, which reduces the simulation time and improves the computational efficiency. The method was verified by matching an example test.

Article
Publication date: 3 May 2016

Xing Shi, Xianwen Huang, Yao Zheng and Susu Zhao

The purpose of this paper is to explore the effects of the camber on gliding and hovering performance of two-dimensional corrugated airfoils. While the flying mechanism of natural…

Abstract

Purpose

The purpose of this paper is to explore the effects of the camber on gliding and hovering performance of two-dimensional corrugated airfoils. While the flying mechanism of natural flyers remains a myth up to nowadays, the simulation serves as a minor step toward understanding the steady and unsteady aerodynamics of the dragonfly flight.

Design/methodology/approach

The lattice Boltzmann method is used to simulate the flow past the cambered corrugated dragonfly airfoil at low Reynolds numbers. For gliding flight, the maximum camber, the distance of the location of maximum camber point from the leading edge and Reynolds number are regarded as control variables; for hovering flight, the maximum camber, the flapping amplitude and trajectory are considered as control variables. Then corresponding simulations are performed to evaluate the implications of these factors.

Findings

Greater gliding ratio can be reached by increasing the maximum camber of the dragonfly wing section. When the location of the maximum camber moves backward along the wing chord, large scale flow separation can be delayed. These two effects result in better gliding performances. For hovering performances, it is found that for different flapping amplitudes along an inclined plane, the horizontal force exerted on the airfoils increases with the camber, and the drag growths first but then drops. It is also found that the elliptic flapping trajectory is most sensitive to the camber of the cambered corrugated dragonfly wing section.

Originality/value

The effects of the camber on gliding and hovering performance of the cambered dragonfly wing section are explored in detail. The data obtained can be helpful when designing micro aerial vehicles.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 7 August 2017

Peijian Zhou, Fujun Wang and Jiegang Mou

Rotating stall is an unsteady flow phenomenon that causes instabilities and low efficiency in pumps. The purpose of this paper is to investigate the rotating stall characteristics…

Abstract

Purpose

Rotating stall is an unsteady flow phenomenon that causes instabilities and low efficiency in pumps. The purpose of this paper is to investigate the rotating stall characteristics and unsteady behavior of stall cells in a centrifugal pump impeller at low flow rates.

Design/methodology/approach

A developed large eddy simulation with dynamic mixed nonlinear model is performed to evaluate the unsteady flow in a centrifugal pump impeller. The rotating stall flow field through the centrifugal pump impeller is analyzed under three typical flow rates. Frequency spectrum analysis are carried out on the series of pressure fluctuation to get the rotating stall characteristics. The size and intensity of stall cells are also analyzed using time-averaged vorticity and static pressure.

Findings

The rotating stall cell first occurs in the suction side of the blade and exhibits an obvious life cycle including decay mergence, shedding, growing and development with a low frequency. With the decrease of flow rate, the amplitude of pressure fluctuations in the impeller tends to be larger, the propagated speed of stall cells and rotating stall frequency tends to be smaller, but the number of cells remains unchanged. The size of stall cells increases as the flow rate decreases, but intensity changes is very little.

Originality/value

The rotating stall characteristics in a centrifugal pump impeller under low flow rates are presented first using a developed large eddy simulation approach.

Details

Engineering Computations, vol. 34 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 3 November 2021

Jerome de Laborderie, Cedric Babin and Fabrizio Fontaneto

The present paper aims at evaluating the lattice Boltzmann method (LBM) on a high-subsonic high-pressure compressor stage at nominal regime.

Abstract

Purpose

The present paper aims at evaluating the lattice Boltzmann method (LBM) on a high-subsonic high-pressure compressor stage at nominal regime.

Design/methodology/approach

The studied configuration corresponds to the H25 compressor operated in a closed-loop test rig at the von Karman Institute. Several operating points are simulated with LBM for two grids of successive refinements. A detailed analysis is performed on the time-averaged flow predicted by LBM, using a comparison with experimental and existing RANS data.

Findings

The finest grid is found to correctly predict the mean flow across the machine, as well as the influence of the rotor tip gap size. Going beyond time-averaged data, some flow analysis is performed to show the relevance of such a high-fidelity method applied to a compressor configuration. In particular, vortical structures and their evolution with the operating points are clearly highlighted. Spectral analyses finally hint at a proper prediction of tonal and broadband contents by LBM.

Originality/value

The application of LBM to high-speed turbomachinery flows is very recent. This paper validates one of the first LBM simulations of a high-subsonic high-pressure compressor stage.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 12 October 2018

Weiwei Wu, Xiaodiao Huang, Yuanyuan Li, Chenggang Fang and Xianhui Jiang

The screw extruder is applied in cement-three-dimensional (3D) printing. The cement paste flow in 3D printing is the typical Herschel–Bulkley fluid. To understand the flow in the…

Abstract

Purpose

The screw extruder is applied in cement-three-dimensional (3D) printing. The cement paste flow in 3D printing is the typical Herschel–Bulkley fluid. To understand the flow in the channel, the improved lattice Boltzmann method (LBM) is proposed.

Design/methodology/approach

For Herschel–Bulkley flow, an improved LBM is presented to avoid the poor stability and accuracy. The non-Newtonian effect is regard as a special forcing term. The Poiseuille flow is taken to discuss the detailed process of the method. With the method, the analytical solution and numerical solution are obtained and compared. Then, the effect of the initial yield stress on the numerical solution is both explored by the shear-thickening fluid and the shear-thinning fluid. Moreover, the variations of the relative errors under different lattice nodes and different power-law indexes are analyzed. Finally, the method is applied into the simulation of the flow in the extruder of cement-3D printing.

Findings

The results show that the improved method is effective for Herschel–Bulkley fluids, which can simulate the flow in the extruder stably and accurately.

Practical implications

The simulation can contribute to understand the cement paste flow in the screw extruder, which helps to optimize the structure of the extruder in the following periods.

Originality/value

The improve method provide a new way to analyze the flow in the extruder of cement-3D printing. Also, in the past research, LBM for Herschel–Bulkley fluid is ignored, whereas the study can provide the reference for the numerical simulation.

Details

Rapid Prototyping Journal, vol. 25 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 25 March 2024

Kalidas Das and Pinaki Ranjan Duari

Several graphs, streamlines, isotherms and 3D plots are illustrated to enlighten the noteworthy fallouts of the investigation. Embedding flow factors for velocity, induced…

10

Abstract

Purpose

Several graphs, streamlines, isotherms and 3D plots are illustrated to enlighten the noteworthy fallouts of the investigation. Embedding flow factors for velocity, induced magnetic field and temperature have been determined using parametric analysis.

Design/methodology/approach

Ternary hybrid nanofluids has outstanding hydrothermal performance compared to classical mono nanofluids and hybrid nanofluids owing to the presence of triple tiny metallic particles. Ternary hybrid nanofluids are considered as most promising candidates in solar energy, heat exchangers, electronics cooling, automotive cooling, nuclear reactors, automobile, aerospace, biomedical devices, food processing etc. In this work, a ternary hybrid nanofluid flow that contains metallic nanoparticles over a wedge under the prevalence of solar radiating heat, induced magnetic field and the shape factor of nanoparticles is considered. A ternary hybrid nanofluid is synthesized by dispersing iron oxide (Fe3O4), silver (Ag) and magnesium oxide (MgO) nanoparticles in a water (H2O) base fluid. By employing similarity transformations, we can convert the governing equations into ordinary differential equations and then solve numerically by using the Runge–Kutta–Fehlberg approach.

Findings

There is no fund for the research work.

Social implications

This kind of study may be used to improve the performance of solar collectors, solar energy and solar cells.

Originality/value

This investigation unfolds the hydrothermal changes of radiative water-based Fe3O4-Ag-MgO-H2O ternary hybrid nanofluidic transport past a static and moving wedge in the presence of solar radiating heating and induced magnetic fields. The shape factor of nanoparticles has been considered in this study.

Details

Multidiscipline Modeling in Materials and Structures, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 4 July 2016

V. Jaiganesh and K. Prakasan

The purpose of this work is to visualize the flow behaviour in critical sections of a pressurized gating system.

Abstract

Purpose

The purpose of this work is to visualize the flow behaviour in critical sections of a pressurized gating system.

Design/methodology/approach

The investigation was carried out using water models of gating system that were designed, invoking the principles of similitude. Water was used as the filling medium, and the manner of flow through various sections of the gating system and the cavity was recorded with a high-speed camera capable of capturing images up to 10,000 frames per second. This was followed by an analysis of the results obtained from each phase. Finally, computer simulations of flow were carried out using commercial software. The manner of filling as observed during experiments and that during simulation were compared so as to draw some useful conclusions on the utility of flow visualization using water models and the capability of software to predict the filling pattern during casting process. It was understood that water models are powerful aids for understanding the intricacies of flow through critical sections of the gating systems.

Findings

It was observed that water models are a reliable indicator of the mould-filling process. Further, substantial differences in the filling pattern were observed between water model experiments and filling simulation using commercial software.

Research limitations/implications

The findings are limited to horizontal plate-type castings. Also, the influence of surface roughness in the flow through the runner is not considered.

Originality/value

This work facilitates understanding of the importance of flow visualization on the quality and reliability of castings.

Details

Journal of Engineering, Design and Technology, vol. 14 no. 3
Type: Research Article
ISSN: 1726-0531

Keywords

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