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Book part
Publication date: 12 July 2021

Geok Teng Leong, Charles Hin Joo Bong, Fang Yenn Teo and Aminuddin Ab. Ghani

This study explores the concept of hydraulic flushing gate with an automated control system as a flow control structure of the urban storm water system. The research team…

Abstract

This study explores the concept of hydraulic flushing gate with an automated control system as a flow control structure of the urban storm water system. The research team has implemented a flush gate with the automated control system to the flow of the water in a drainage channel. The flow control structure was used to determine the effectiveness of such design by applying the concept of virtually on a real-world drainage system at Jalan Astana, Kuching. Computer representations of the existing drainage system and flow control structure were built using EPA SWMM 5.0 model. The series of flow control structure was proven to hold the runoff from 10-year storm. The modelling result shows that there is 25.9% of flow reduction at outlet node. As a modification of the existing drainage system in the urban area involves high construction cost, by installing a flow control structure in the drainage system is an innovative way to control the flow of the water.

Details

Water Management and Sustainability in Asia
Type: Book
ISBN: 978-1-80071-114-3

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Article
Publication date: 4 September 2017

Heribert Bieler

Aerodynamics drives the aircraft performance and, thus, influences fuel consumption and environmental compatibility. Further, optimization of aerodynamic shapes is an…

Abstract

Purpose

Aerodynamics drives the aircraft performance and, thus, influences fuel consumption and environmental compatibility. Further, optimization of aerodynamic shapes is an ongoing design activity in industrial offices; this will lead to incremental improvements. More significant step changes in performance are not expected from pure passive shape design. However, active flow control is a key technology, which has the potential to realize a drastic step change in performance. Flow control targets two major goals: low speed performance enhancements mainly for start and landing phase via control of separation and drag reduction at high speed conditions via skin friction and shock wave control.

Design/methodology/approach

This paper highlights flow control concepts and Airbus involvements for both items. To mature flow control systematically, local applications of separation control technology are of major importance for Airbus. In parallel, but at lower maturity level, investigations are ongoing to reduce the turbulent skin friction at cruise. A popular concept to delay separation at low speed conditions is the implementation of jet actuation control systems flush mounted to the wall of aerodynamic components.

Findings

In 2006, DLR (in collaboration with universities Berlin, Braunschweig and industrial partner Airbus) started to study active flow control for separation delay towards application. Based on basic proof of concepts (achieved in national projects), further flow control hardware developments and wind tunnel and lab testing took place in European funded projects.

Originality/value

Significant lift enhancements were realized via flow control applied to the wing leading edge and the flap.

Details

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

Keywords

Content available
Article
Publication date: 15 February 2021

Qi Sun, Fang Sun, Cai Liang, Chao Yu and Yamin Zhang

Beijing rail transit can actively control the density of rail transit passenger flow, ensure travel facilities and provide a safe and comfortable riding atmosphere for…

Abstract

Purpose

Beijing rail transit can actively control the density of rail transit passenger flow, ensure travel facilities and provide a safe and comfortable riding atmosphere for rail transit passengers during the epidemic. The purpose of this paper is to efficiently monitor the flow of rail passengers, the first method is to regulate the flow of passengers by means of a coordinated connection between the stations of the railway line; the second method is to objectively distribute the inbound traffic quotas between stations to achieve the aim of accurate and reasonable control according to the actual number of people entering the station.

Design/methodology/approach

This paper analyzes the rules of rail transit passenger flow and updates the passenger flow prediction model in time according to the characteristics of passenger flow during the epidemic to solve the above-mentioned problems. Big data system analysis restores and refines the time and space distribution of the finely expected passenger flow and the train service plan of each route. Get information on the passenger travel chain from arriving, boarding, transferring, getting off and leaving, as well as the full load rate of each train.

Findings

A series of digital flow control models, based on the time and space composition of passengers on trains with congested sections, has been designed and developed to scientifically calculate the number of passengers entering the station and provide an operational basis for operating companies to accurately control flow.

Originality/value

This study can analyze the section where the highest full load occurs, the composition of passengers in this section and when and where passengers board the train, based on the measured train full load rate data. Then, this paper combines the full load rate control index to perform reverse deduction to calculate the inbound volume time-sharing indicators of each station and redistribute the time-sharing indicators for each station according to the actual situation of the inbound volume of each line during the epidemic. Finally, form the specified full load rate index digital time-sharing passenger flow control scheme.

Details

Smart and Resilient Transport, vol. 3 no. 1
Type: Research Article
ISSN: 2632-0487

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Article
Publication date: 3 April 2018

Wai Yin Mok

Concurrency is a desirable property that enhances workflow efficiency. The purpose of this paper is to propose six polynomial-time algorithms that collectively maximize…

Abstract

Purpose

Concurrency is a desirable property that enhances workflow efficiency. The purpose of this paper is to propose six polynomial-time algorithms that collectively maximize control flow concurrency for Business Process Model and Notation (BPMN) workflow models. The proposed algorithms perform model-level transformations on a BPMN model during the design phase of the model, thereby improving the workflow model’s execution efficiency.

Design/methodology/approach

The approach is similar to source code optimization, which solely works with syntactic means. The first step makes implicit synchronizations of interdependent concurrent control flows explicit by adding parallel gateways. After that, every control flow can proceed asynchronously. The next step then generates an equivalent sequence of execution hierarchies for every control flow such that they collectively provide maximum concurrency for the control flow. As a whole, the proposed algorithms add a valuable feature to a BPMN modeling tool to maximize control flow concurrency.

Findings

In addition, this paper introduces the concept of control flow independence, which is a user-determined semantic property of BPMN models that cannot be obtained by any syntactic means. But, if control flow independence holds in a BPMN model, the model’s determinism is guaranteed. As a result, the proposed algorithms output a model that can be proved to be equivalent to the original model.

Originality/value

This paper adds value to BPMN modeling tools by providing polynomial-time algorithms that collectively maximize control flow concurrency in a BPMN model during the design phase of the model. As a result, the model’s execution efficiency will increase. Similar to source code optimization, these algorithms perform model-level transformations on a BPMN model through syntactic means; and the transformations performed to each control flow are guaranteed to be equivalent to the control flow. Furthermore, a case study on a real-life new employee preparation process is provided to demonstrate the proposed algorithms’ usefulness on increasing the process’s execution efficiency.

Details

Business Process Management Journal, vol. 24 no. 2
Type: Research Article
ISSN: 1463-7154

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Article
Publication date: 24 May 2013

A.S. Zymaris, D.I. Papadimitriou, E.M. Papoutsis‐Kiachagias, K.C. Giannakoglou and C. Othmer

The purpose of this paper is to propose the use of the continuous adjoint method as a tool to identify the appropriate location and “type” (suction or blowing) of steady…

Abstract

Purpose

The purpose of this paper is to propose the use of the continuous adjoint method as a tool to identify the appropriate location and “type” (suction or blowing) of steady jets used in active flow control systems.

Design/methodology/approach

The method is based on continuous adjoint and covers both internal and external aerodynamics. The adjoint equations, including the adjoint to the SpalartAllmaras turbulence model and their boundary conditions are formulated. At the cost of solving the flow and adjoint equations just once, the sensitivity derivatives of the objective function with respect to hypothetical (normal) jet velocities at all wall nodes are computed. Comparisons of the computed sensitivities with finite differences and parametric studies to assess the present method are included.

Findings

Though the sensitivities are computed for zero jet velocities, they adequately support decision making on: the recommended location of jet(s), at boundary nodes with high absolute valued sensitivities; and the selection between suction or blowing jets, based on the sign of the computed sensitivities. Regarding adjoint methods, two important findings of this work are: the role of the adjoint pressure which proves to be an excellent sensor in flow control problems; and the prediction accuracy of the proposed adjoint method compared to the commonly made assumption of “frozen turbulence”.

Originality/value

First use of the continuous adjoint method using full differentiation of the turbulence model, in flow control optimization. A low‐cost design tool for recommending some of the most important jet characteristics.

Details

Engineering Computations, vol. 30 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 11 October 2018

Wienczyslaw Stalewski and Andrzej Krzysiak

The purpose of this study is to develop the concept of self-adapting system which would be able to control a flow on the wing-high-lift system and protect the flow against…

Abstract

Purpose

The purpose of this study is to develop the concept of self-adapting system which would be able to control a flow on the wing-high-lift system and protect the flow against strong separation.

Design/methodology/approach

The self-adapting system has been developed based on computational approach. The computational studies have been conducted using the URANS solver. The experimental investigations have been conducted to verify the computational results.

Findings

The developed solution is controlled by closed-loop-control (CLC) system. As flow actuators, the main-wing trailing-edge nozzles are proposed. Based on signals received from the pressure sensors located at the flap trailing edge, the CLC algorithm changes the amount of air blown from the nozzles. The results of computational simulations confirmed good effectiveness and reliability of the developed system. These results have been partially confirmed by experimental investigations.

Research limitations/implications

The presented research on an improvement of the effectiveness of high-lift systems of modern aircraft was conducted on the relatively lower level of the technology readiness. However, despite this limitation, the results of presented studies can provide a basis for developing innovative self-adaptive aerodynamic systems that potentially may be implemented in future aircrafts.

Practical implications

The studies on autonomous flow-separation control systems, operating in a closed feedback loop, are a great hope for significant advances in modern aeronautical engineering, also in the UAV area. The results of the presented studies can provide a basis for developing innovative self-adaptive aerodynamic systems at a higher level of technological readiness.

Originality/value

The presented approach is especially original and valuable in relation to the innovative concept of high-lift system supported by air-jets blown form the main-wing-trailing-edge nozzles; the effective and reliable flow sensors are the pressure sensors located at the flap trailing edge, and the effective and robust algorithm controlling the self-adapting aerodynamic system – original especially in respect to a strategy of deactivation of flow actuators.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 3
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 29 April 2014

Wei Wang, Spiridon Siouris and Ning Qin

The purpose of this article is to present numerical investigations of flow control with piezoelectric actuators on a backward facing step (BFS) and fluidic vortex…

Abstract

Purpose

The purpose of this article is to present numerical investigations of flow control with piezoelectric actuators on a backward facing step (BFS) and fluidic vortex generators on a NACA0015 aerofoil for the reattachment and separation control through the manipulation of the Reynolds stresses.

Design/methodology/approach

The unsteady flow phenomena associated with both devices are simulated using Spalart–Allmaras-based hybrid Reynolds averaged Navier-Stokes (RANS)/large eddy simulation (LES) models (detached eddy simulation (DES), delayed detached eddy simulation (DDES) and improved delayed detached eddy simulation (IDDES)), using an in-house computational fluid dynamics (CFD) solver. Results from these computations are compared with experimental observations, enabling their reliable assessment through the detailed investigation of the Reynolds stresses and also the separation and reattachment.

Findings

All the hybrid RANS/LES methods investigated in this article predict reasonable results for the BFS case, while only IDDES captures the separation point as measured in the experiments. The oscillating surface flow control method by piezoelectric actuators applied to the BFS case demonstrates that the Reynolds stresses in the controlled case decrease, and that a slightly nearer reattachment is achieved for the given actuation. The fluidic vortex generators on the surface of the NACA0015 case force the separated flow to fully reattach on the wing. Although skin friction is increased, there is a significant decrease in Reynolds stresses and an increase in lift to drag ratio.

Originality/value

The value of this article lies in the assessment of the hybrid RANS/LES models in terms of separation and reattachment for the cases of the backward-facing step and NACA0015 wing, and their further application in active flow control.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 3
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 1997

N. Saxena, C. Precious, A. Carr and S. Adams

Well designed stable reflow ovens andwave machines can be operated at low rates of the inerting gas. One problem is that at the lowestflow rate settings changes in room…

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Abstract

Well designed stable reflow ovens and wave machines can be operated at low rates of the inerting gas. One problem is that at the lowest flow rate settings changes in room draughts and in external venting conditions can affect the internal oxygen levels unless the flow rates are altered. The internal oxygen levels can drift or suddenly alter. This generally means that the ovens are operated at higher flows than necessary in order to ensure steady operations below some desired oxygen level without excessive operator intervention. A closed‐loop control system using the output of internal oxygen meters to vary the flow rates set by mass flow meters is one way to ensure steady operation. One such system — NITRAPILOT™ control system—has been developed by BOC Gases as a stand alone system that can be added to existing equipment. The results of small‐scale and production level testing on this system are described in the present paper. Reduced flow rates can be achieved for stable set point oxygen levels at critical locations. An equally significant benefit, particularly when used in conjunction with data logging, is that the system assists in statistical process control since it ensures, monitors and logs compliance with process recipes without operator intervention.

Details

Soldering & Surface Mount Technology, vol. 9 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 March 2021

S. D. Farahani and Amir Hossein Rabiee

In this study, for the first time, the efficacy of control rods for full suppression of vortex-induced vibrations (VIV) and galloping of an elastically supported rigid…

Abstract

Purpose)

In this study, for the first time, the efficacy of control rods for full suppression of vortex-induced vibrations (VIV) and galloping of an elastically supported rigid square cylinder that vibrates freely in the cross-flow direction is investigated.

Design/methodology/approach

To this aim, two small control rods are placed at constant angles of ± 45° relative to the horizontal axis and then the influence of diameter and spacing ratios on the oscillation and hydrodynamic response along with the vortex structure behind the cylinder is evaluated in the form of nine different cases in both VIV and galloping regions.

Findings

The performed simulations show that using the configuration presented in this study results in full VIV suppression for the spacing ratios G/D = 0.5, 1 and 1.5 at the diameter ratios d/D = 0.1, 0.2 and 0.3 (D: diameter of square cylinder, G: distance between rods and cylinder, d: diameter of rods). On the contrary, a perfect attenuation of galloping is only achieved at the largest diameter (d/D = 0.3) and the smallest spacing ratio (G/D = 0.5). In general, for both VIV and galloping regions, with increasing diameter ratio and decreasing spacing ratio, the effect of the control rods wake in the vortex street of square cylinder gradually increases. This trend carries on to the point where the vortex shedding is completely suppressed and only the symmetric wake of control rods is observed.

Originality/value

So far, the effect of rod control on VIV of a square cylinder and its amplitude of oscillations has not been investigated.

Details

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

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Article
Publication date: 6 November 2018

Sang Ho Kim and Yohan An

This paper aims to investigate the impact of the separation between control and cash flow rights (control-ownership disparity) on the earnings management practices of…

Abstract

Purpose

This paper aims to investigate the impact of the separation between control and cash flow rights (control-ownership disparity) on the earnings management practices of Chinese firms. The notable features of Chinese firms are those of concentrated ownership and the severe disparity that exists between the control and cash flow rights of controlling shareholders.

Design/methodology/approach

This study measures the level of Chinese firms’ earnings management by adopting two different methods of measurement: accrual-based earnings management (AEM) and real activity earnings management (REM). The authors also consider the possible trade-off effects between these two types of measurements. The data set in this study encompasses over 2,000 Chinese firms, using data from 2003 to 2015.

Findings

The results indicate that controlling shareholders are more likely to engage in AEM as their cash flow rights are more concentrated, while they are less likely to use REM as the disparity of control-cash flow rights increases. Further, this inverse relationship between REM and control-cash flow rights disparity becomes more pronounced in the case of a low cash flow rights group. As REM generally causes distortions in firms’ operations, it is possible that the controlling shareholders are more likely to constrain the use of REM as the disparity is perceived to grow. This result may indicate a reduced agency problem between controlling and minority shareholders due to the developing and/or existing ownership dispersions, which are mainly driven by recent reforms applied to Chinese capital markets. However, we do not entirely exclude the possibility of other types of expropriations by the controlling shareholders. It appears that the controlling shareholders are still able to exert a significant level of control, even following a substantial ownership dispersion, and they may seek alternative expropriation methods, including but not limited to intercorporate loan or related party transactions as the disparity of control-cash flow rights increases.

Originality/value

Although the Chinese economy is experiencing a series of reforms to infuse market forces into capital markets, little has been known about the effects of ownership-control disparity in Chinese firms. Our findings highlight the importance of the country specific context in this vein of research.

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