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Article
Publication date: 1 November 1990

Paul Etchells

ENHANCEMENTS in the cutting of materials such as composites and metals can provide manufacturers in the aerospace and aircraft industries with the improvements they require in…

Abstract

ENHANCEMENTS in the cutting of materials such as composites and metals can provide manufacturers in the aerospace and aircraft industries with the improvements they require in productivity and quality.

Details

Aircraft Engineering and Aerospace Technology, vol. 62 no. 11
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 November 1992

Paul Etchells

SINCE 1985, the use of abrasive‐entrained water jets to cut a wide variety of metallic and non‐metallic materials has rapidly expanded, creating a whole new industry and an…

Abstract

SINCE 1985, the use of abrasive‐entrained water jets to cut a wide variety of metallic and non‐metallic materials has rapidly expanded, creating a whole new industry and an ever‐expanding series of new applications. In fact, for certain materials, abrasive water jet cutting offers distinct advantages over alternative processes for cutting in two dimensions.

Details

Aircraft Engineering and Aerospace Technology, vol. 64 no. 11
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 30 December 2021

Pushkar Prakash Kamble, Subodh Chavan, Rajendra Hodgir, Gopal Gote and K.P. Karunakaran

Multi-jet deposition of the materials is a matured technology used for graphic printing and 3 D printing for a wide range of materials. The multi-jet technology is fine-tuned for…

Abstract

Purpose

Multi-jet deposition of the materials is a matured technology used for graphic printing and 3 D printing for a wide range of materials. The multi-jet technology is fine-tuned for liquids with a specific range of viscosity and surface tension. However, the use of multi-jet for low viscosity fluids like water is not very popular. This paper aims to demonstrate the technique, particularly for the water-ice 3 D printing. 3 D printed ice parts can be used as patterns for investment casting, templates for microfluidic channel fabrication, support material for polymer 3 D printing, etc.

Design/methodology/approach

Multi-jet ice 3 D printing is a novel technique for producing ice parts by selective deposition and freezing water layers. The paper confers the design, embodiment and integration of various subsystems of multi-jet ice 3 D printer. The outcomes of the machine trials are reported as case studies with elaborate details.

Findings

The prismatic geometries are realized by ice 3 D printing. The accuracy of 0.1 mm is found in the build direction. The part height tends to increase due to volumetric expansion during the phase change.

Originality/value

The present paper gives a novel architecture of the ice 3 D printer that produces the ice parts with good accuracy. The potential applications of the process are deliberated in this paper.

Details

Rapid Prototyping Journal, vol. 28 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 20 April 2015

Yexiang Xiao, Zhengwei Wang, Jidi Zeng, jintai Zheng, Jiayang Lin and Lanjin Zhang

The purpose of this paper is to experimentally and numerically investigate the interference characteristics between two ski-jump jets on the flip bucket in a large dam spillway…

Abstract

Purpose

The purpose of this paper is to experimentally and numerically investigate the interference characteristics between two ski-jump jets on the flip bucket in a large dam spillway when two floodgates are running.

Design/methodology/approach

The volume of fluid (VOF) method together with the Realizable k-ε turbulence model were used to predict the flow in two ski-jump jets and the free surface motion in a large dam spillway. The movements of the two gates were simulated using a dynamic mesh controlled by a User Defined Function (UDF). The simulations were run using the prototype dam as the field test to minimize errors due to scale effects. The simulation results are compared with field test observations.

Findings

The transient flow calculations, accurately predict the two gate discharges compared to field data with the predicted ski-jump jet interference flow pattern similar to the observed shapes. The transient simulations indicate that the main reason for the deflected nappe is the larger opening difference between the two gates as the buttress side gate closes. When both gates are running, the two ski-jump jets interfere in the flip bucket and raise the jet nappe to near the buttress to form a secondary flow on this jet nappe surface. As the gate continues to close, the nappe surface continues to rise and the surface secondary flow become stronger, which deflects the nappe over the side buttress.

Originality/value

A dynamic mesh is used to simulate the transient flow behavior of two prototype running gates. The transient flow simulation clarifies the hydraulics mechanism for how the two ski-jump jets interfere and deflect the nappe.

Details

Engineering Computations, vol. 32 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 30 September 2014

Wanyun Xue, Wenxin Huai, Zhongdong Qian, Zhonghua Yang and Yuhong Zeng

The purpose of this paper is to examine the initial mixing of wastewater discharged from submerged outfall diffusers and the influence of port configurations on wastewater…

Abstract

Purpose

The purpose of this paper is to examine the initial mixing of wastewater discharged from submerged outfall diffusers and the influence of port configurations on wastewater distribution based on computational results.

Design/methodology/approach

Marine wastewater discharges from multiport diffusers are investigated by numerically solving three-dimensional and uncompressible two-phase flow fields. A mixture model simulates this flow and the standard k-e model to resolve flow turbulence; inter-phase interactions were described in terms of relative slip velocity between phases. Computations were performed for two values of the port spacings s/H with different current Froude numbers F.

Findings

Computational results compared well with previous laboratory measurements. Numerical results reveal that for both the closely spaced (s/H=0.21) and widely spaced (s/H=3.0) ports, the normalized dilution Sn becomes independent of F; further, the length of the near field xn and the spreading layer thickness hn are functions of F. For the closely spaced ports, the wastewater discharge behaves like a line plume, the Coanda effect is obvious, quasi-bifurcation is present, horseshoe structures of the jets in the planes are rapidly produced and then squashed and elongated, and the jet trajectories based on maximum velocity precede those based on maximum concentration. For the widely spaced ports, the wastewater discharge behaves like a point plume, the Coanda effect is not obvious, bifurcation is present, horseshoe structures of the jets in the planes are gradually produced and become ellipses, and the jet trajectories based on maximum velocity are similar to those based on maximum concentration.

Originality/value

Semi-empirical equations are presented to predict major near field characteristics. These provide guidance for designing multiport diffusers and assessing environmental impact.

Details

Engineering Computations, vol. 31 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 2 March 2015

Zhanhong Wan, Saihua Huang, Zhilin Sun and Zhenjiang You

The present work is devoted to the numerical study of the stability of shallow jet. The effects of important parameters on the stability behavior for large scale shallow jets are…

Abstract

Purpose

The present work is devoted to the numerical study of the stability of shallow jet. The effects of important parameters on the stability behavior for large scale shallow jets are considered and investigated. Connections between the stability theory and observed features reported in the literature are emphasized. The paper aims to discuss these issues.

Design/methodology/approach

A linear stability analysis of shallow jet incorporating the effects of bottom topography, bed friction and viscosity has been carried out by using the shallow water stability equation derived from the depth averaged shallow water equations in conjunction with both Chézy and Manning resistance formulae. Effects of the following main factors on the stability of shallow water jets are examined: Rossby number, bottom friction number, Reynolds number, topographic parameters, base velocity profile and resistance model. Special attention has been paid to the Coriolis effects on the jet stability by limiting the rotation number in the range of Ro∈[0, 1.0].

Findings

It is found that the Rossby number may either amplify or attenuate the growth of the flow instability depending on the values of the topographic parameters. There is a regime where the near cancellation of Coriolis effects due to other relevant parameters influences is responsible for enhancement of stability. The instability can be suppressed by the bottom friction when the bottom friction number is large enough. The amplification rate may become sensitive to the relatively small Reynolds number. The stability region using the Manning formula is larger than that using the Chézy formula. The combination of these effects may stabilize or destabilize the shallow jet flow. These results of the stability analysis are compared with those from the literature.

Originality/value

Results of linear stability analysis on shallow jets along roughness bottom bed are presented. Different from the previous studies, this paper includes the effects of bottom topography, Rossby number, Reynolds number, resistance formula and bed friction. It is found that the influence of Reynolds number on the stability of the jet is notable for relative small value. Therefore, it is important to experimental investigators that the viscosity should be considered with comparison to the results from inviscid assumption. In contrast with the classical analysis, the use of multi-parameters of the base velocity and topographic profile gives an extension to the jet stability analysis. To characterize the large scale motion, besides the bottom friction as proposed in the related literature, the Reynolds number Re, Rossby number Ro, the topographic parameters and parameters controlling base velocity profile may also be important to the stability analysis of shallow jet flows.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 25 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 February 1953

Recent technical developments in the field of hydrodynamic sustentation, resulting from the unique techniques associated with the free‐body testing of self‐propelled dynamically…

Abstract

Recent technical developments in the field of hydrodynamic sustentation, resulting from the unique techniques associated with the free‐body testing of self‐propelled dynamically similar models, has resulted in a great resurgence of interest in the use of water‐based aircraft in the National Defence. This paper describes some of the more important aspects of this research and discusses possible trends in military water‐based aircraft development. In addition to the military applications of the new high‐speed hydrodynamic developments, consideration is given to the development of transonic water‐based transport designs. Since the days of the famous flying‐boat clippers, over‐ocean transport has all but succumbed to the faster landplane. It is shown that an all‐jet water‐based transport, incorporating unusual safety and performance, is now a practical and logical development.

Details

Aircraft Engineering and Aerospace Technology, vol. 25 no. 2
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 5 January 2015

Paul Stark and Udo Fritsching

The purpose of this paper is to develop a numerical model to simulate the flow field as well as the conjugate heat transfer during unsteady cooling of a flat plate with a single…

Abstract

Purpose

The purpose of this paper is to develop a numerical model to simulate the flow field as well as the conjugate heat transfer during unsteady cooling of a flat plate with a single submerged water jet. At wall temperatures above the liquid boiling point, the vapor formation process and the interaction of the vapor phase with the developing jet-flow field are included.

Design/methodology/approach

The time-dependent flow and temperature distribution during all occurring boiling phases as well as the local and temporal distribution of the heat transfer coefficient on a flat plate can be simulated.

Findings

The influence of the liquid jet flow rate (10,800=Re_d=32,400) and the nozzle distance to the plate (4=H/d=20) on the transient cooling process are analyzed. This includes the time-dependant positions of the transition regions between the boiling phases on the plate as well as the temperatures at these transition regions. Additionally, the local heat transfer rates are a direct result of the unsteady cooling simulation.

Originality/value

A single model approach is developed and utilized to simulate the unsteady cooling process of a flat plate with an impinging water jet including all occurring boiling phases.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 25 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 25 August 2021

Asif Ur Rehman and Vincenzo M. Sglavo

Recent advances in 3D printing construction elements have focused on ordinary Portland cement (OPC) concrete using polymeric binders; herein, this study aims to produce the same…

Abstract

Purpose

Recent advances in 3D printing construction elements have focused on ordinary Portland cement (OPC) concrete using polymeric binders; herein, this study aims to produce the same using pure water.

Design/methodology/approach

A binder jet printer prototype was used to fabricate specimens that are used to assess geometric and mechanical properties. Two distinct water-based binder formulations, compatible with OPC chemistry and piezoelectric jetting device, were used: pure water and water-polyvinyl alcohol (98:2 w/w) solution.

Findings

This study examines the effect of binder flow rate on dimensional accuracy. Furthermore, the changes in the mechanical properties over time with hydration have been investigated.

Practical implications

Results indicate that the increase in mechanical strength of Portland cement concrete with pure water was consistent; however, it was delayed by the water: PVA (98:2 w/w) solution. Post-curing by water vapor hardened the structure with the removal of layering native to 3DP and decreased infilling porosity by diffusion mechanism.

Originality/value

This paper has used pure water jetting for BJT of Portland cement-containing bodies.

Details

Rapid Prototyping Journal, vol. 28 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 1 March 1969

Gunnar Mouritzen

THE effect of the propulsive efficiency is analysed for all speed regions and methods for obtaining optimum propulsive efficiency for any speed and environmental conditions are…

Abstract

THE effect of the propulsive efficiency is analysed for all speed regions and methods for obtaining optimum propulsive efficiency for any speed and environmental conditions are investigated for different type vehicles. Also, the importance of the propulsive efficiency is compared to other factors such as weight of power plant, specific fuel consumption, specific power ratio, specific thrust ratio, etc. Finally, on the basis of considering all power plant factors, it is shown how to achieve optimum propulsion for any vehicle at required operating conditions.

Details

Aircraft Engineering and Aerospace Technology, vol. 41 no. 3
Type: Research Article
ISSN: 0002-2667

1 – 10 of over 4000