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Article
Publication date: 7 June 2019

Zhen Chen, Zhengqi Gu and Zhonggang Wang

This paper aims to propose a precise turbulence model for vehicle aerodynamics, especially for vehicle window buffeting noise.

Abstract

Purpose

This paper aims to propose a precise turbulence model for vehicle aerodynamics, especially for vehicle window buffeting noise.

Design/methodology/approach

Aiming at the fact that commonly used turbulence models cannot precisely predict laminar-turbulent transition, a transition-code-based improvement is introduced. This improvement includes the introduction of total stress limitation (TSL) and separation-sensitive model. They are integrated into low Reynolds number (LRN) k-ε model to concern transport properties of total stress and precisely capture boundary layer separations. As a result, the ability of LRN k-ε model to predict the transition is improved. Combined with the constructing scheme of constrained large-eddy simulation (CLES) model, a modified LRN CLES model is achieved. Several typical flows and relevant experimental results are introduced to validate this model. Finally, the modified LRN CLES model is used to acquire detailed flow structures and noise signature of a simplified vehicle window. Then, experimental validations are conducted.

Findings

Current results indicate that the modified LRN CLES model is capable of achieving acceptable accuracy in prediction of various types of transition at various Reynolds numbers. And, the ability of this model to simulate the vehicle window buffeting noise is greater than commonly used models.

Originality/value

Based on the TSL idea and separation-sensitive model, a modified LRN CLES model concerning the laminar-turbulent transition for the vehicle window buffeting noise is first proposed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 9
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 19 July 2019

Sha Zhang, Zhengqi Gu, Wenguang Wu, Ledian Zheng, Jun Liu and Shanbin Yin

The purpose of this paper is to develop a numerical model used for calculating the nonlinearities of large-scale hydro-pneumatic suspension (HPS) and investigating the…

Abstract

Purpose

The purpose of this paper is to develop a numerical model used for calculating the nonlinearities of large-scale hydro-pneumatic suspension (HPS) and investigating the effects of variations in flow path and operational parameter on suspension damping response.

Design/methodology/approach

To parameterization nonlinearities of the suspension, the author developed a two-phase flow model of a large-scale HPS based on computational fluid dynamics and volume of fluid method. Considerable effort was made to verify the nonlinearities by field measurements carried out on an off-highway mining dump truck. The investigation of effects of variations in flow path and operational parameter on damping characteristics highlights the necessity of the numerical simulation.

Findings

The two-phase flow model can represent the gas-oil interaction and simulate the suspension operational movement conveniently. Transient numerical simulation results can be used to model the nonlinearities of large-scale HPS accurately. A new phenomenon was discovered that the pressure in rebound chamber presents reduction trend during compression stroke in special cases. It has never been reported before.

Originality/value

Developed a two-phase flow model of a large-scale HPS, which can manage the gas-oil interaction and capture the complex flow field structure in it. The paper is the first study to model the nonlinearities of a large-scale HPS used in off-highway mining dump truck through transient numerical simulation. Compared with previous researches, such a research not only gives new insight and thorough understanding into the suspension internal fluid structure but also can give good guiding opinions to the optimal design of HPS.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 12 September 2018

Shuya Li, Zhengqi Gu, Taiming Huang, Zhen Chen and Jun Liu

The purpose of this paper is to develop a two-way coupling approach for investigating the aerodynamic stability of vehicles under the combined effect of crosswind and road…

Abstract

Purpose

The purpose of this paper is to develop a two-way coupling approach for investigating the aerodynamic stability of vehicles under the combined effect of crosswind and road adhesion.

Design/methodology/approach

The author develops a new two-way coupling approach, which couples large eddy simulation with multi-body dynamics (MBD), to investigate the crosswind stability on three different adhesion roads: ideal road, dry road and wet road. The comparison of the results obtained using the traditional one-way coupling approach and the new two-way coupling approach is also done to assess the necessity to use the proposed coupling technique on low adhesion roads, and the combined effect of crosswind and road adhesion on vehicle stability is analyzed.

Findings

The results suggest that the lower the road adhesion is, the larger deviation a vehicle generates, the more necessary to conduct the two-way coupling simulation. The combined effect of the crosswind and road adhesion can decrease a vehicle’s lateral motion on a high adhesion road after the disappearing of the crosswind. But on a low adhesion road, the vehicle tends to be unstable for its large head wind angle. The vehicle stability in crosswind on a low adhesion road needs more attention, and the investigation should consider the coupling of aerodynamics and vehicle dynamics and the combined effect of crosswind and road adhesion.

Originality/value

Developing a new two-way coupling approach which can capture the complex vehicle structures and the road adhesion with MBD model and the completed fluid filed structure with CFD model. The present study might be the first study considering the coupling of crosswind and low adhesion road. The proposed two-way coupling approach will be useful for researchers who study vehicle crosswind stability.

Details

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

Keywords

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Article
Publication date: 2 November 2015

Tien Phuc Dang, Zhengqi Gu and Zhen Chen

The purpose of this paper is to gain a better understanding of the flow field structure around the race car in two cases: stationary wheel and rotating wheel. In addition…

Abstract

Purpose

The purpose of this paper is to gain a better understanding of the flow field structure around the race car in two cases: stationary wheel and rotating wheel. In addition, this paper also illustrates and clarifies the influence of wheel rotation on the aerodynamic characteristics around the race car.

Design/methodology/approach

The author uses steady Reynolds-Averaged Navier-Stokes (RANS) equations with the Realizable k-ε model to study model open-wheel race car. Two cases are considered, a rotating wheel and stationary wheel.

Findings

The results obtained from the study are presented graphically, pressure, velocity distribution, the flow field structure, lift coefficient (Cl) and drag coefficient (Cd) for two cases and the significant influence of rotating case on flow field structure around wheel and aerodynamic characteristics of race car. The decreases in Cd and Cl values in the rotating case for the race car are 16.83 and 13.25 per cent, respectively, when compared to the stationary case.

Originality/value

Understanding the flow field structures and aerodynamic characteristics around the race car in two cases by the steady RANS equations with the Realizable k-ε turbulence model.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 25 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 31 August 2010

John Hassard, Jonathan Morris, Jackie Sheehan and Xiao Yuxin

The purpose of this paper is to examine how the Chinese economic reform process has engendered significant changes in the structure and management of work organizations…

Abstract

Purpose

The purpose of this paper is to examine how the Chinese economic reform process has engendered significant changes in the structure and management of work organizations. Central to this process has been the “marketization” of state‐owned enterprises (SOEs). The paper reviews the attempts to reform SOEs as conducted, primarily, under the modern enterprise system (MES) and group company system (GCS) programmes.

Design/methodology/approach

The paper analyses institutional issues relating to organizational restructuring, describes the evolution of the SOE “problem” in China, and discusses case evidence of enterprise reform in one of the largest SOE‐dominated industries, iron and steel. Qualitative field data, collected regularly (mostly yearly) since 1995, were derived from in‐depth interviews with executives of ten large SOEs that have restructured as part of MES and GCS programmes.

Findings

It is suggested that the historic reluctance of SOEs to embrace reform stems from three main factors – the opaque nature of property rights, the failure of ministries to produce a firm strategy for channelling surplus labour and the inability of government agencies to offer a sense of managerial autonomy to SOE executives. Recent policies designed to overcome these problems together with kindred ones for separating government functions from business operations in the drive to prepare SOEs for global markets are described. It can be argued that China's preference for gradual reform reflects the wider reform context where economic restructuring has not been accompanied by a greater expression of political democracy.

Originality/value

The paper's findings offer insights from a major longitudinal field study of two of the main programmes of China's reform period.

Details

Journal of Organizational Change Management, vol. 23 no. 5
Type: Research Article
ISSN: 0953-4814

Keywords

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