Search results

1 – 10 of over 49000
Article
Publication date: 18 September 2019

Shiyu Feng, Chenchen Wang, Xiaotian Peng, Yan Yan, Yang Deng and Jun Chen

The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of…

Abstract

Purpose

The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of pressure relief process under various plenum compartment pressures and Mach numbers.

Design/methodology/approach

Under various plenum compartment pressures and Mach numbers, the effect of the area and aspect ratio on the discharge and force characteristics of the PRD are numerically investigated via a three-dimensional steady Reynolds-averaged Navier–Stokes equations solver based on structured grid technology.

Findings

When the aspect ratio remains constant, the discharge coefficient CD, thrust coefficient CT and moment coefficient CM are not affected by the PRD. When the area is constant, the aspect ratio dramatically impacts the discharge and force characteristics because the aspect ratio increases, the discharge coefficient CD of the PRD decreases, and the thrust coefficient CT and the moment coefficient CM both increase. When the aspect ratio is 2, the discharge coefficient CD decreases by 14.7 per cent, the thrust coefficient CT increases by 10-15 per cent, and the moment coefficient CM increases by 10-23 per cent compared with when the aspect ratio is 1.

Practical implications

This study provides detailed data and conclusions for nacelle PRD researchers and actual engineering applications.

Originality/value

On the basis of considering the influence of operating conditions on the discharge and force characteristics of the nacelle PRD, the impact of geometric parameters, including the area and aspect ratio on the discharge and force characteristics is comprehensively considered.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 2
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 3 April 2018

Faicel Hammami, Nader Ben-Cheikh, Brahim Ben-Beya and Basma Souayeh

This paper aims to analyze the effect of aspect ratio A and aspect velocity ratio a on the bifurcation occurrence phenomena in lid-driven cavity by using finite volume…

Abstract

Purpose

This paper aims to analyze the effect of aspect ratio A and aspect velocity ratio a on the bifurcation occurrence phenomena in lid-driven cavity by using finite volume method (FVM) and multigrid acceleration. This study has been performed for certain pertinent parameters; a wide range of the Reynolds number values has been adopted, and aspect ratios ranging from 0.25 to 1 and various velocity ratios from 0.25 to 0.825 have been considered in this investigation. Results show that the transition to the unsteady regime follows the classical scheme of Hopf bifurcation, giving rise to a perfectly periodic state. Flow periodicity has been verified through time history plots for the velocity component and phase-space trajectories as a function of Reynolds number. Velocity profile for special case of a square cavity (A = 1) was found to be in good agreement between current numerical results and published ones. Flow characteristics inside the cavity have been presented and discussed in terms of streamlines and vorticity contours at a fixed Reynolds number (Re = 5,000) for various aspect ratios (a = 0).

Design/methodology/approach

The numerical method is based on the FVM and multigrid acceleration.

Findings

Computations have been investigated for several Reynolds numbers and aspect ratios A (0.25, 0.5, 0.75, 0.825 and 1). Besides, various velocity ratios (a = 0.25, 0.5, 0.75 and 0.825) at fixed aspect ratios (A = 0.25, 0.5 and 0.75) were considered. It is observed that the transition to the unsteady regime follows the classical scheme of Hopf bifurcation, giving rise to a perfectly periodic state. Flow periodicity is verified through time history plots for velocity components and phase-space trajectories.

Originality/value

The bifurcations between steady and unsteady states are investigated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 20 June 2019

Ze-Xiang Wu, Hui Ji, Jian Han and Chuang Yu

Current modellings of granular collapse are lack of considering the effect of soil density. This paper aims to present a numerical method to analyse the collapse of…

Abstract

Purpose

Current modellings of granular collapse are lack of considering the effect of soil density. This paper aims to present a numerical method to analyse the collapse of granular column based on the critical-state soil mechanics.

Design/methodology/approach

In the proposed method, a simple critical-state based constitutive model is first adopted and implemented into a finite element code using the coupled Eulerian–Lagrangian technique for large deformation analysis. Simulations of column collapse with various aspect ratios are then conducted for a given initial soil density. The effect of aspect ratio on the final size of deposit morphology, dynamical collapse profiles and the stable region is discussed comparing to experimental results. Moreover, complementary simulations with various initial soil densities on each aspect ratio are conducted.

Findings

Simulations show that a lower value of initial density leads to a lower final deposit height and a longer run-out distance. The simulated evolutions of kinetic energy and collapsing profile with time by the proposed numerical approach also show clearly a soil density-dependent collapse process.

Practical implications

To the end, this study can improve the understanding of column collapse in different aspect ratios and soil densities, and provide a computational tool for the analysis of real scale granular flow.

Originality/value

The originality of this paper is proposed in a numerical approach to model granular column collapse considering the influences of aspect ratio and initial void ratio. The proposed approach is based on the finite element platform with coupled Eulerian–Lagrangian technique for large deformation analysis and implementing the critical-state based model accounting for the effect of soil density.

Details

Engineering Computations, vol. 36 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 12 June 2009

S.Z. Shuja, B.S. Yilbas and S.M.A. Khan

The purpose of this paper is to consider flow over heat generating bodies in an open‐ends cavity, which finds applications in electronics cooling and industrial…

Abstract

Purpose

The purpose of this paper is to consider flow over heat generating bodies in an open‐ends cavity, which finds applications in electronics cooling and industrial processing. Heat transfer rates depend on the flow situation in the cavity, which is influenced by the cavity inlet and exit port locations, heat transferring body size and its orientation in the cavity, and the cavity size. Consequently, modeling of flow over heat transferring bodies in an open‐ends cavity and examination of the effect of the aspect ratio and orientation of the heat transferring bodies on the flow field and heat transfer rates becomes essential.

Design/methodology/approach

The flow over heat generating solid blocks situated in an open‐ends cavity is considered and the effects of blocks' orientations and aspect ratios on flow field as well as heat transfer rates are examined. A numerical scheme using a control volume approach is introduced to predict flow field in the cavity and heat transfer rates from the blocks.

Findings

It is found that complex flow structure is generated in the cavity due to the aspect ratios and orientations of the blocks. This, in turn, influences significantly heat transfer rates from the blocks in the cavity.

Research limitations/implications

Surface areas of blocks are kept the same and aspect ratio is varied such that the surface area of each block remains the same in the simulations. In addition, Steady flow situation is considered for governing equations of flow and heat transfer in the cavity. However, for the future study transient heating and flow situations can be considered while varying the surface araes of the blocks. This will provide useful information on the circulations in the cavity and the enhancement of heat transfer due to the complex flow structure.

Practical implications

In practice, cooling effectiveness can be improved through changing the aspects ratio of the heat generating bodies in the cavity.

Originality/value

The findings are original and will be useful for the scientists and the design engineers working the specific area of heat transfer and fluid flow.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 2 October 2017

M. Tahani, M. Masdari and M. Kazemi

This paper aims to analyze the influence of the changings in geometrical parameters on the aerodynamic performance of the control canard projectiles.

Abstract

Purpose

This paper aims to analyze the influence of the changings in geometrical parameters on the aerodynamic performance of the control canard projectiles.

Design/methodology/approach

Because of the mentioned point, the range of projectiles increment has a considerable importance, and the design algorithm of a control canard projectile was first written. Then, were studied the effects of canard geometric parameters such as aspect ratio, taper ratio and deflectable nose on lift to drag coefficient ratio, static margin based on the slender body theory and cross section flow.

Findings

The code results show that aspect ratio increment, results in an increase in lift-to-drag ratio of the missile, but increase in canard taper ratio results in increasing of lift-to-drag ratio at 1° angle of attack, while during increasing the canard taper ratio up to 0.67 at 4° angle of attack, lift to drag first reaches to maximum and then decreases. Also, static margin decreases with canard taper ratio and aspect ratio increment. The developed results for this type of missile were compared with same experimental and computational fluid dynamic (CFD) results and appreciated agreement with other results at angles of attack between 0° and 6°.

Practical implications

To design a control canard missile, the effect of each geometric parameter of canard needs to be estimated. For this purpose, the suitable algorithm is used. In this paper, the effects of canard geometric parameters, such as aspect ratio, taper ratio and deflectable nose on lift-to-drag coefficient ratio and static margin, were studied with help of the slender body theory and cross-section flow.

Originality/value

The contribution of this paper is to predict the aerodynamic characteristics for the control canard missile. In this study, the effect of the design parameter on aerodynamic characteristics can be estimated, and the effect of geometrical characteristics has been analyzed with a suitable algorithm. Also, the best lift-to-drag coefficient for the NASA Tandem Control Missile at Mach 1.75 was selected at various angles of attack. The developed results for this type of missile were compared with same experimental and CFD results.

Details

Aircraft Engineering and Aerospace Technology, vol. 89 no. 6
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 19 October 2018

Mohsen Izadi, Rasul Mohebbi, A. Chamkha and Ioan Pop

The purpose of this paper is to consider natural convection of a nanofluid inside of a C-shaped cavity using Lattice Boltzmann method (LBM).

Abstract

Purpose

The purpose of this paper is to consider natural convection of a nanofluid inside of a C-shaped cavity using Lattice Boltzmann method (LBM).

Design/methodology/approach

Effects of some geometry and flow parameters consisting of the aspect ratio of the cavity, aspect ratio of the heat source; Rayleigh number (Ra = 103 − 106) have been investigated. The validity of the method is checked by comparing the present results with ones from the previously published work.

Findings

The results demonstrate that for Ra = 103, the aspect ratio of the heat source has more influence on the average Nusselt number in contrast to the case of Ra = 106. Contrary to the fact that the average Nusselt number increases non-linearly more than twice because of the increase of the aspect ratio of the enclosure at Ra = 103, the average Nusselt number has a linear relation with the aspect ratio for of Ra = 106. Therefore, upon increasing the Rayleigh number, the efficiency of the aspect ratio of the cavity on the thermal convection, gradually diminishes.

Originality/value

The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 3 August 2021

Rui Wang, Chunlan Liu, Yong Wei and Yudong Su

This paper aims to study the sensitivity enhancement effect of the gold nanorod on fiber surface plasmon resonance (SPR) sensor. It proposes modeling the sensing effects…

94

Abstract

Purpose

This paper aims to study the sensitivity enhancement effect of the gold nanorod on fiber surface plasmon resonance (SPR) sensor. It proposes modeling the sensing effects of fiber SPR sensor decorated with metal nanoparticles. By using simulation and experiment, the sensitivity enhancement effect of the gold nanorod was studied and demonstrated.

Design/methodology/approach

The paper opted for an exploratory study using simulation approach of finite-difference time-domain. Specifically, the effect of ratios and aspect ratios of gold nanorod on sensing performance are investigated theoretically. Based on the mathematical models, the validation experiments by using the gold nanorod with the aspect ratios of 5.1 were done to verify the sensitivity enhancement effect of the gold nanorod.

Findings

In conclusion, it is evident that with the increases of the aspect ratios, the sensing sensitivity of the refractive index increases first, then gradually stabilizes or decreases. After parameter optimization, the ratios and aspect ratios of gold nanorod are chosen to be 8 nm and 12.5, respectively, which makes the optimal refractive index sensitivity of 4465.53 nm/RIU be realized. In addition, the validation experiments by using the gold nanorod with the aspect ratios of 5.1 verify the sensitivity enhancement effect of the gold nanorods.

Originality/value

This paper proposes and demonstrates a new method for the sensitivity enhancement of fiber SPR sensor. After parameter optimization, the maximum sensitivity of 4465.53 nm/RIU was achieved by using 8 nm gold nanorods with the aspect ratios of 12.5. To verify the sensitivity enhancement of the gold nanorods, the authors also did the validation experiments. The testing results indicated that after the decoration of the gold nanorods, the sensitivity of the sensing probe increases from 2190.57 nm/RIU to 2693.24 nm/RIU, which demonstrates the sensitivity enhancement effect of the gold nanorods.

Details

Sensor Review, vol. 41 no. 4
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 1 December 2003

Prodip Kumar Das, Shohel Mahmud, Syeda Humaira Tasnim and A.K.M. Sadrul Islam

A numerical simulation has been carried out to investigate the buoyancy induced flow and heat transfer characteristics inside a wavy walled enclosure. The enclosure…

Abstract

A numerical simulation has been carried out to investigate the buoyancy induced flow and heat transfer characteristics inside a wavy walled enclosure. The enclosure consists of two parallel wavy and two straight walls. The top and the bottom walls are wavy and kept isothermal. Two straight‐vertical sidewalls are considered adiabatic. Governing equations are discretized using the control volume based finite‐volume method with collocated variable arrangement. Simulation was carried out for a range of surface waviness ratios, λ=0.00‐0.25; aspect ratios, A=0.25‐0.5; and Rayleigh numbers Ra=100‐107 for a fluid having Prandtl number equal to 1.0. Results are presented in the form of local and global Nusselt number distributions, streamlines, and isothermal lines for different values of surface waviness and aspect ratios. For a special case of λ=0 and A=1.0, the average Nusselt number distribution is compared with available reference. The results suggest that natural convection heat transfer is changed considerably when surface waviness changes and also depends on the aspect ratio of the domain. In addition to the heat transfer results, the heat transfer irreversibility in terms of Bejan number (Be) was measured. For a set of selected values of the parameters (λ, A, and Ra), a contour of the Bejan number is presented at the end of this paper.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 13 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 April 1957

Karl L. Sanders

IN the present paper an attempt has been made to determine the optimum aspect ratio, wing loading and fuel load ratio under certain specified design conditions. Aeroplanes…

Abstract

IN the present paper an attempt has been made to determine the optimum aspect ratio, wing loading and fuel load ratio under certain specified design conditions. Aeroplanes with turbojet as well as with airscrew propulsion have been considered.

Details

Aircraft Engineering and Aerospace Technology, vol. 29 no. 4
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 22 September 2020

Yazhou Mao, Yang Jianxi, Jinchen Ji, Wenjing Xu and Quanyuan Guo

Currently, there is a lack of fast and highly accurate on analytical solution of Reynolds equation for evaluating the characteristics of surface textured bearing. This…

Abstract

Purpose

Currently, there is a lack of fast and highly accurate on analytical solution of Reynolds equation for evaluating the characteristics of surface textured bearing. This paper aims to develop such an analytical solution of Reynolds equation for an effective analysis of the characteristics of surface textured bearings.

Design/methodology/approach

By using the separation of variables method and mean eigenvalue method, the analytical solution is constructed. The CFD simulations and experimental results are used to validate the correctness of the analytical solution.

Findings

The analytical solution can accurately evaluate the characteristics of textured bearings. It is found that the larger the eccentricity ratio and aspect ratio, the greater the oil film force. It also found that the smaller the eccentricity ratio, the larger the Sommerfeld number S. When eccentricity ratio e = 0.65, the attitude angles of different oil boundaries are same. The effect of different aspect ratios on dynamic stiffness and damping coefficient generally follows a same trend. It is numerically shown that the critical speed of rotor-bearing is 3500 rpm.

Originality/value

The analytical solution provides a simple yet effective way to study the characteristics of surface textured bearings.

Details

Industrial Lubrication and Tribology, vol. 72 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

1 – 10 of over 49000