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A loose group of individuals working on a task differs from an effective team on nine factors: clearly defined goals, priorities, roles and responsibilities, self-awareness, leadership, group dynamics, communications, content, and infrastructure. Ways to eliminate barriers and speed formation of effective teams could be based on those factors. (Contains 23 references.) (SK)

This paper presents the findings of an investigation on the use of several blade-tip configurations (modified by the addition of various end plates at the blade tip) for passive noise control in industrial fans. Utilizing an experimental technique developed to investigate noise sources along the radius of the blades, together with cross-correlation and coherence analyses of the near field and far field, the modified blade-tip configurations are shown to reduce the rotor-only aeroacoustic signature of the fan as a direct consequence of changes induced in tip-leakage flow behavior. These changes in the nature of flow mechanisms in the region of the blade tip are correlated with the spanwise noise sources, and their role in the creation of overall acoustic emissions is thus clarified. The tip-leakage flow structures are analyzed to identify their contribution to overall noise and interaction with other noise sources. Coherence spectra are also analyzed to investigate the relevance of the noise sources. The cross-correlations reveal distinctive acoustic signatures that are described in detail The methodology has been demonstrated to be effective in identifying (i) the blade-tip configuration with the best acoustic performance, and (ii) other significant noise sources along the blade span. The modified tip configurations are shown to have a significant effect on the multiple vortex behavior of leakage flow, especially with respect to the near-wall fluid-flow paths on both blade surfaces. The reduction in fan acoustic emissions is assessed and correlated with the control of tip-leakage flows achieved by the modified blade tips. [DOI: 10.1115/1.4000462]

In this paper, the use of DIY transducers is proposed to detect the pressure instabilities in a low-speed industrial axial fan. The authors aim is to detect rotating stall, a well-studied aerodynamic instability with a typical frequency that can be even lower than 10 Hz in low-speed industrial fans. Pressure transducers and piezoelectric sensors, such as microphones, in turbomachinery are used respectively in the near and far field as standard methods to perform time-resolved pressure measurements. Other classes of sensors, such as electret microphones, may be not suited for pressure measurements, especially in the ultrasound region because their cut-off frequency is about 20 Hz. In this study, the authors use a low-cost DIY technology, as alternative technology to stall detection, in comparison with a high precision piezoelectric sensor. The authors performed the pressure measurements using a dynamic transducer, a piezoresistive transducer, and a piezoelectric high sensitivity sensor that provides the measurement baseline. They implemented and set-up a measurement chain to identify the typical rotating stall pattern in low-speed axial fans. The results have been validated with respect to the state-of-the-art acoustic control techniques described in literature. The signals acquired using the two technologies are discussed using a combination of spectral and time-domain space reconstruction. The acoustic patterns obtained through the phase space reconstruction show that the DIY dynamic sensor is a good candidate solution for the rotating stall acoustic analysis. [ABSTRACT FROM AUTHOR]

Tunnel ventilation fans are subjected to pressure pulses as a consequence of trains passing the ventilation shafts within which they are installed. These pressure pulses alter the volume flow rate through a ventilation fan, and consequently the static pressure field around fan blades. Today’s trains typically travel through railway tunnels faster than has been the historic norm. Additionally, platform screen doors are now a standard feature of metro systems. Both result in the trains involved inducing larger pressure pulses than industrial fan designers have traditionally assumed. Although tunnel ventilation fan in-service failures are rare, engineers increasingly associate those failures with new or renovated tunnel systems with larger pressure pulses. Consequently, we require insight into the aerodynamic and mechanical consequences that occur with subjecting a tunnel ventilation fan to a pressure pulse. In the research reported in this paper, the authors model the pressure pulse induced by a train in a tunnel system as a rapidly changing fan volume flow rate. The authors computed the fan operating point by means of a large eddy simulation with a one-equation sub-grid scale turbulence model. The authors undertook the computation using the open source computational fluid dynamic code OpenFOAM. An analysis of the computational results provides an insight into the effects of turbulent structures that develop within the fan blade passage. The analysis indicates that a pressure pulse too brief to drive a tunnel ventilation fan into stall still results a doubling of the unsteady aerodynamic and mechanical forces to which the blade is subjected. A doubling of unsteady mechanical forces as a consequence of a pressure pulse constitutes an increase significant enough to contribute to the tunnel ventilation fan’s in-service mechanical failure. [ABSTRACT FROM PUBLISHER]

Stall-induced vibration places fundamental limitations on industrial fan performance and remains a persistent problem in the development of industrial fans and compressors. In this paper, we present an experimental programme that utilised two strategies to study rotating stall recovery patterns in an industrial fan. The experimental facility incorporated a fan with both variable pitch in motion blades and a variable speed drive. The facility enabled us first, to study the evolution of unsteady pressure signals on the fan casing whilst varying fan blade pitch and then to examine varying fan rotational speed. Consequently, we were able to recover a fan from stall either by varying blade pitch at constant speed, or by varying speed at constant blade pitch. We also studied the physical flow phenomena associated with stall recovery by cross-correlating signals from circumferentially offset high frequency response pressure transducers and then analysed the cross-spectra. This enabled us to gain insight into the transient fluid flow behaviour associated with stall recovery in the studied industrial fan class. The transient fluid flow behaviour associated with stall recovery by varying blade pitch was indicative of both a mild and progressive transition. In contrast, stall recovery by varying fan speed occurred more suddenly. In comparison with the variable pitch transition, the variable speed transition was more indicative of recovery from mild surge. From this we may conclude that stall recovery via variable speed resulted in significantly higher unsteady mechanical stress induced in fan rotating components than recovery via variable pitch. Higher bending stresses in the fan blades are more likely to result in mechanical failure, and therefore we may conclude that the studied fan is more ‘stall tolerant’ when one operates it as a variable pitch fan rather than as a variable speed fan. [ABSTRACT FROM PUBLISHER]

Taking inspiration from previous biomimetic studies on the performance of humpback whale flippers, this paper reports a programme of work to design a ‘whale-fan’ that incorporates a sinusoidal leading-edge blade profile that mimics the tubercles on humpback whales flippers. Previous researchers have used two-dimensional cascades of aerofoils to study the effects of a sinusoidal profile on aerofoil lift and drag performance. The research was primarily concerned with elucidating the fluid-flow mechanisms induced by the sinusoidal profile and the impact of those mechanisms on aerofoil performance. The results indicate that a sinusoidal leading-edge profile has improved lift recovery post-stall and, thus, is inherently more aerodynamically resistant to the effect of stall.The reported research focuses on the application of previous research conducted with infinite span cascades of aerofoils to the design and optimisation of a finite span aerofoil. The paper presents the assumptions when developing a three-dimensional aerofoil-design methodology that correlates the sinusoidal profile of the blade-leading edge with the desired vorticity distribution at the trailing edge. The authors apply the developed methodology to the design of a fan blade’s tip region to control separation at the trailing edge. The paper presents numerically derived whale-fan performance characteristics and compares them with both numerically and experimentally derived performance characteristics of the baseline fan. [ABSTRACT FROM PUBLISHER]

Induced draft fans extract coal-fired boiler exhaust gases in the form of a two-phase flow with a dispersed solid phase made of unburnt coal and fly ash; consequently fan blades are subject to erosion causing material wear at the leading edge, trailing edge, and blade surface. Erosion results in blade material loss, a reduction of blade chord, and effective camber that together degrade aerodynamic performance. This paper presents a numerical study of the erosive process in an induced draft fan carried out by simulating the particle laden flow using an original finite element Eulerian-Lagrangian solver. The particle trajectories are calculated using a particle cloud tracking technique that considers drifting near wall and an algebraic erosion model. The numerical study clarifies the influence of fan operation to the determination of the erosion regimes and patterns. In particular, the study investigates the role played by the size and mass distribution of the particles by considering a real composition of the flying ashes in the exhaust flow from a coal-fired boiler. The results illustrate the critical blade areas and erosion rates as given by the particle dynamics of different sizes. A specific analysis of the material wear at the blade leading edge is also given. [ABSTRACT FROM AUTHOR]

Taking a lead from the humpback whale flukes, characterized by a series of bumps that result in a sinusoidal-like leading edge, this paper reports on a three-dimensional numerical study of sinusoidal leading edges on cambered airfoil profiles. The turbulent flow around the cambered airfoil with the sinusoidal leading edge was computed at different angles of attack with the open source solver OpenFOAM, using two different eddy viscosity models integrated to the wall. The reported research focused on the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters. For these reasons a comparison with a symmetric airfoil is provided. The research was primarily concerned with the elucidation of the fluid flow mechanisms induced by the bumps and the impact of those mechanisms on airfoil performance, on both symmetric and cambered profiles. The bumps on the leading edge influenced the aerodynamic performance of the airfoil, and the lift curves were found to feature an early recovery in post-stall for the symmetric profile with an additional gain in lift for the cambered profile. The bumps drove the fluid dynamic on the suction side of the airfoil, which in turn resulted in the capability to control the separation at the trailing edge in coincidence with the peak of the sinusoid at the leading edge. [ABSTRACT FROM AUTHOR]

In this paper we discuss a computational method focused on the prediction of unsteady aerodynamics, adequate for industrial turbomachinery. Here we focus on a single rotor device selected from a new family of large tunnel ventilation axial flow fans. The flow field in the fan was simulated using the open source code OPENFOAM, with a large-eddy simulation (LES) approach. The sub-grid scale (SGS) closure relied on a one-equation model, that requires us to solve a differential transport equation for the modeled SGS turbulent kinetic energy. The use of such closure was here considered as a remedial strategy in LES of high-Reynolds industrial flows, being able to tackle the otherwise insufficient resolution of turbulence spectrum. The results show that LES of the fan allows to predict the pressure rise capability of the fan and to reproduce the most relevant flow features, such as three-dimensional separation and secondary flows. [ABSTRACT FROM AUTHOR]

Because aerodynamic stall is a major potential cause of mechanical failure in axial fans, effective stall-warning techniques have had wide application for many years. The study assesses the application of stall-detection to a class of heavy-duty fans for induced draft service in coal-fired power plants. With a multi-MW installed power, this class of fans operates at constant rotational speed, utilising variable-pitch in motion blades to adjust fan duty point. This load modulation system, in the presence of blade erosion or fouling, could result in fans becoming prone to stall as a consequence of the reduced pressure capacity. This article reports on a novel methodology, first proposed for the early detection of stall in low-speed axial-flow fans for tunnel ventilation. With respect to the original concept, which was based on the analysis of hydrodynamic pressure as measured on the fan ducting, the investigation demonstrates the potential of processing far-field pressure signals in identifying stall pre-cursors, and in so doing, establishing the stall incipience. This acoustic stall-detection system is characterised in a laboratory environment exploring the fan operating envelope. Time-resolved pressure measurements are carried out with pre-polarised pressure transducers fitted into (a) the fan casing over the fan blades (near field) and (b) in the inlet plenum 1 diameter upstream of the fan rotor (far field). The evolution of the rotating stall for the fan under scrutiny is first presented. The rationale of the signal processing technique is given, together with a sensitivity study on its metrical parameters. Finally, the signal visualization technique is used to compare the patterns related to the presence of stall in the pressure signals recorded in the near- and the far field. [ABSTRACT FROM PUBLISHER]

This paper presents a fully reversible blade parametric design methodology. The blades are for application in jet fans that ventilate and provide emergency smoke control in road tunnels. The blade design variables are tip solidity, twist, and camber distribution. The authors base the design methodology on a sensitivity analysis which they derived from a response sulfate approximation. They construct the latter using a computational analysis of four experimental cases which they generated using an experimental design approach. The sensitivity analysis calculates a rank and a weight for each design variable that affects the jet-fan performance parameters thrust and efficiency, and thus facilitates insight into each variable's relative importance. Finally, the authors present a redesign of" an existing reversible jet-fan blade by following the design guidelines which they obtained from the sensitivity analysis. The authors study the aerodynamic characteristics of the redesigned blade and compare it to that of the base- line design configuration. They then manufacture a redesigned blade prototype. Finally, the authors present thrust and power measurements for both the baseline jet fan, and the baseline jet .fan when fitted with a redesigned blade. [ABSTRACT FROM AUTHOR]

There are controversial requirements involved in developing numerical methodologies in order to compute the flow in industrial fans. The full resolution of turbulence spectrumin such high-Reynolds number flow configurations entails unreasonably expensive computational costs. The authors applied the study to a large unidirectional axial flow fan unit for tunnel ventilation to operate in the forward direction under ambient conditions. This delivered cooling air to the tunnel under routine operation, or hot gases at 400°C under emergency conditions in the event of a tunnel fire. The simulations were carried out using the open source code OpenFOAM, within which they implemented a very large eddy simulation (VLES) based on one-equation SGS model to solve a transport equation for the modelled (subgrid) turbulent kinetic energy. This subgrid turbulence model improvement is a remedial strategy in VLES of high-Reynolds number industrial flows which are able to tackle the turbulence spectrum's well-known insufficient resolution. TheVLES of the industrial fan permits detecting the unsteady topology of the rotor flow. This paper explores the evolution of secondary flow phenomena and speculates on its influence on the actual load capability when operating at peakpressure condition. Predicted noise emissions, in terms of sound pressure level spectra, are also compared with experimental results and found to agree within the uncertainty of the measurements. [ABSTRACT FROM AUTHOR]

The paper describes a stalldetection criterion based on the use of symmetrised dot pattern (SDP) visual waveform analysis and the stallwarning methodology based on a recently developed analysis. The experimental study explores the capability of the SDP technique to detect the stall incipience and evolution in the presence of low signal-to-noise ratios, that is, a noisy working environment. Moreover, the investigation presents a systematic analysis on the probe position's influence with respect to the fan section. As such, the SDP technique in combination with an acoustic measurement is able to create a visual pattern that one can use to detect stall from potentially any location around the fan/duct system. [ABSTRACT FROM AUTHOR]

In this study, the airborne noise generated by an axial fan installed in a draft-cooled unit is studied. The fan is tested without, and with three different blade-tip end-plates. The standard end-plate geometric has a constant thickness (TF) while the others two end-plates (TFvte and TFmvb) are designed to deliber¬ately control the swirl level of the blade tip leakage vortex. Results have proven that these end-plates reduce the tip-leakage flow and vortex formation, which in turn has a favourable impact on the axial fan noise signature in standardised airways. This study uses both free-field standardised airways, and to reproduce installation effects an induced draft configuration over a set of tube banks to distort the axial fan inflow. The paper discusses far-field noise measurements in terms of spectral analysis and directivity for the different end-plate configurations. Although installation effects alter the noise signature of the tested rotors, the TFmvb end-plate design outperforms the other rotors, as a conse¬quence of the high control of the tip flow, resulting also in lower harmonic tones. [ABSTRACT FROM AUTHOR]

This paper describes work aimed at establishing the ability of a tunnel ventilation fan to operate without risk of mechanical failure in the event of aerodynamic stall. The research establishes the aerodynamic characteristics of a typical tunnel ventilation fan when operated in both stable and stalled aerodynamic conditions, with and without an anti-stall stabilisation ring, with and without a "nonstalling" blade angle and at full, half, and one quarter design speed. It also measures the fan's peak stress, thus facilitating an analysis of the implications of the experimental results for mechanical design methodology. The paper concludes by presenting three different strategies for tunnel ventilation fan selection in applications where the selected fan will most likely stall. The first strategy selects a fan with a low-blade angle that is nonstalling. The second strategy selects a fan with a high-pressure developing capability. The third strategy selects a fan with a fitted stabilisation ring. Tunnel ventilation system designers each have their favoured fan selection strategy. However, all three strategies can produce system designs within which a tunnel ventilation fan performs reliably in-service. The paper considers the advantages and disadvantages of each selection strategy and considered the strengths and weaknesses of each. [ABSTRACT FROM AUTHOR]

This paper describes research involving an in-service failure of a "variable pitch in motion" fan's blade bearing. Variable pitch in motion fans rotate at a constant speed, with the changing blade angle varying the load. A pitch-change mechanism facilitates the change in blade angle. A blade bearing supports each blade enabling it to rotate. The author observed that as the fan aerodynamic stage loading progressively increased, so did the rate of blade-bearing wear. The reported research addressed two separate, but linked, needs. First, the ongoing need to increase fan pressure development capability required an increase in fan loading. This increase was within the context of an erosive operating regime which systematically reduced fan pressure development capability. The second need was to identify the root cause of blade-bearing failures. The author addressed the linked needs using a computational analysis, improving the rotor inflow aerodynamic characteristics through an analysis of the inlet box and design of inlet guide vanes to control flow nonuniformities at the fan inlet. The results of the improvement facilitated both an increase in fan-pressure-developing capability and identification of the root cause of the blade-bearing failures. [ABSTRACT FROM AUTHOR]

Tunnel ventilation fans, classically, must have the ability to both supply and extract air from a tunnel system, with the operator's choice dependent on the tunnel ventilation system's operating mode most appropriate at any given point in time. Consequently, tunnel ventilation fans must incorporate a reversible aerodynamic design which limits the maximum fan pressure rise. This paper presents three high pressure reversible fan concepts. These comprise a two-stage counter rotating fan, a single-stage high speed fan, and a two-stage fan with a single motor and impeller on each end of the motor shaft. The authors consider the relative merits of each concept. The third concept offers the most compact fan, transform, silencer, and damper package size. The authors discuss the mechanical design challenges that occur with a two-stage fan with a single motor and impeller on each end of the motor shaft. They present and consider a selectedmotor bearing arrangement and casing design formaintainability. Finally, the authors present both prototype fan and full-scale package aerodynamic and acoustic performance, before discussing the challenges presented by high temperature certification in accordance with the requirements of EN 12101-3: 2012. [ABSTRACT FROM AUTHOR]

The authors investigate the far-field noise emissions of a datum fan blade fitted with tip end-plate geometries, originally designed to control the leakage vortex swirl level. The end-plate geometries influence the tip-leakage flow, vortex formation, and swirl level. In doing so, the end-plate geometries influence the sound-power levels. After an evaluation of fan rotors' aerodynamic performance, the study compares the rotors' far-field noise signature characterised in terms of sound-power and pressure-level spectra to enable and assess the end-plate acoustic pay-off. The investigation attempts to establish a cause-and-effect relationship between the tipflow dynamics and the radiated sound fields, exploring the diverse directivity patterns. The authors found a tonal reduction, due to the enhanced blade-tip end-plates and clarified the relevance of the tip features influencing the radial distribution of the noise sources using coherence analysis. The modified multiple-vortex breakdown end-plate design was effective in reducing the broadband noise, giving an improvement in the frequency range of the turbulent noise. [ABSTRACT FROM AUTHOR]

This study investigates the causal relationship between flow aerodynamics and radiated noise in low-speed axial fans. Using blades with three distinctive tip configurations, including two that were developed with a view to reducing noise emissions, the pressure fluctuations of the exhaust flow in the near field are correlated with the noise measured in the far field in an anechoic chamber. By varying the far-field microphone's azimuthal position, the study investigates the source signatures and directivity of noise sources distributed along the blade span. Several distinctive features in the noise directivity pattern are identified and correlated with the noise sources of aerodynamic origin dissected along the blade span. Utilizing the directional far-field autospectra of the three blade configurations in combination with the near-field/far-field cross-spectra, the emission characteristics of the aerodynamic sources are analyzed and their roles with respect to the overall acoustic signature of the fan are discussed. It is apparent that the ability to decompose the output of the aerodynamic noise sources in the near field is a useful tool in designing fans to achieve desirable low-noise targets. The results confirm that the tip-flow appendages influence the noise radiation pattern for the investigated family of fans. These phenomena are linked with the control of aerodynamic noise sources related to the tip-leakage vortex and the hub corner separation. [ABSTRACT FROM AUTHOR]

This paper describes a capacitance-based tip clearance measurement system which engineers have used in the most demanding turbine test applications. The capacitance probe has survived extended use in a major European gas turbine manufacturer's hightemperature demonstrator unit, where it functioned reliably at a turbine entry temperature in excess of 1800 degrees Kelvin. This paper explores blade by blade tip clearance measurement techniques and examines probe performance under laboratory conditions in support of high-temperature installations. The paper outlines the blade by blade tip clearance measurement technique and describes the experimental facility used to study tip clearance measurement. The paper also fully describes the method used to calibrate the measurement system in order to ascertain measurement accuracy. The paper clarifies how the practical problems were overcome associated with making blade by blade tip clearance measurements in both compressor and turbine environments. Since its initial development, gas turbine development programmes have routinely used the clearance measurement system. The inherent robustness of the system has resulted in reliable in-service measurement of clearance in real world applications. [ABSTRACT FROM AUTHOR]

This paper reports on quantitative tests of passive techniques for rotor-tip noise control in low-speed axial flow fans, based on blade-tip modifications involving the addition of antivortex appendages as end-plates. The end-plate thickness chordwise distribution is determined to control the chordwise evolution of the leakage vortex rotation number. The results confirm that the new end-plate configurations provide a mechanism by which leakage vortex bursting can be avoided. As such, the modified rotors represent an effective means of passive control of vortex breakdown. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including noise mechanisms of air movement fan, gearless one-motor contra-rotating fan, and the conceptual design of reversible axial tunnel ventilation fans in high pressure.

This study assesses the effectiveness of modified blade-tip configurations in achieving passive noise control in industrial fans. The concepts developed here, which are based on the addition of end-plates at the fan-blade tip, are shown to have a beneficial effect on the fan aeroacoustic signature as a result of the changes they induce in tip-leakage-flow behavior. The aerodynamic merits of the proposed blade-tip concepts are investigated by experimental and computational studies in a fully ducted configuration. The flow mechanisms in the blade-tip region are correlated with the specific end-plate design features, and their role in the creation of overall acoustic emissions is clarified. The tip-leakage flows of the fans are analyzed in terms of vortex structure, chordwise leakage flow, and loading distribution. Rotor losses are also investigated. The modifications to blade-tip geometry are found to have marked effects on the multiple vortex behaviors of leakage flow as a result of changes in the near-wall fluid flow paths on both blade surfaces. The improvements in rotor efficiency are assessed and correlated with the control of tip-leakage flows produced by the modified tip end-plates. [ABSTRACT FROM AUTHOR]

Purpose - This study seeks to propose that executives need to be prepared to adopt roles as a mechanism for rotating leadership if those groups of which they are a part are to perform to their full potential. Design/methodology/approach - A validated framework provides insight into the leadership roles executives can adopt when part of formal, informal and temporary groups. The methodology adopted is qualitative, focusing on the application of previously developed frameworks. Findings - Adopting a role is found to enable the rotation of leadership within a group, which in turn facilitates development of the group. Research limitations/implications - A one-organisation intensive case study of a multinational engineering company engaged in the design, development and manufacture of rotating turbomachinery provides the platform for the research. The frameworks will require validating in organisations of different demographic profiles. Practical implications - The concepts advanced and implications discussed provide an insight into the role-based nature of leadership. The practical steps individual executives can take to adopt a role, and in so doing develop the group of which they are a part, are highlighted. Originality/value - This paper is an investigation into, and study of, the process by which executives adopt roles as a mechanism for rotating leadership within a group. In so doing, it is suggested that executives contribute more positively to the development of the groups of which they are a part by being more adaptive and responsive to changes in their surrounding context. [ABSTRACT FROM AUTHOR]

This paper presents an experimental technique developed to assess the performance of a family of axial fans for compact cooling units. It is used to study fan rotor noise sources to enable the effectiveness of design modifications to be assessed. By varying the radial positions of a near field microphone, correlations with a far field microphone are used to study noise source signatures along the blade span. The correlations reveal distinctive acoustic signatures that are described in detail. The methodology has been shown to be effective in identifying: (i) the blade tip feature with the best acoustic performance; and (ii) other significant noise sources along the blade span. [ABSTRACT FROM AUTHOR]

This article reports on the use of modified blade-tip configurations designed with a view to passive noise control in low-speed fans for compact cooling units. The addition of endplates at the tip of a datum fan blade is shown to have a positive influence on the fan's rotor-only aero-acoustic signature. The aerodynamic effects of the modified blade tips are experimentally tested in a fully ducted configuration in the near field and far field using a correlation technique. The nature of the flow mechanisms in the blade-tip region are correlated with the specific endplate design features and their role in the creation of overall acoustic emissions is clarified. The noise emitted by the fans is analysed in terms of coherent vortex structures, tip-leakage flow, and noise sources. Differences in human perception of the noise emitted to the environment are also investigated using a dot-pattern visualization. The study concludes that the modified tip configurations have a marked effect on tip-leakage vortex formation by altering the near-wall fluid paths on blade surfaces. The reduction in rotor noise emission is correlated with the control of tip-leakage flows produced by the tip end-plates. [ABSTRACT FROM AUTHOR]

The application of improved blade tip geometries is studied with the aim of identifying an effective design concept for industrial fan passive noise control. The concept developed optimizes a datum blade by means of profiled endplates at the tip, reducing fan noise by changing the tip leakage flow behaviour. Experimental and computational investigations have been carried out on a family of axial fans, in fully ducted configuration, to establish the aerodynamic merits of the proposed blade tip design concept. The flow mechanisms in the fan tip region are correlated to specific blade design features that promote a reduction of the fan aero-acoustic signature in both tonal and broadband noise components. The tip vortical flow structures are characterized, and their role in creation of overall stage acoustic emissions clarified. The reported research identifies modification of tip geometry as markedly affecting the multiple vortex behaviour of blade tip leakage flow by altering the near-wall fluid flow paths on both blade surfaces. Blade tip endplates were also demonstrated to influence the rotor loss behaviour in the blade tip region. Improvement of rotor efficiency was correlated to the control of tip leakage flows. [ABSTRACT FROM AUTHOR]

Purpose- This monograph seeks to summarise the key influences of a role-based perspective on leadership when making decisions as to how organisational resources can best be deployed. Design/methodology/approach--Application of new frameworks provides insight into the leadership roles executives can adopt when part of formal, informal and temporary groups within the organisation's senior management team and those parts of the organisation for which they are responsible. The methodology adopted is qualitative, focusing on application of previously developed frameworks. Findings Adoption of an appropriate leadership role, and the timely switch from one role to another as circumstances change, are found to facilitate improvement in the ability of executives to mobilise organisational resources, and in so doing effectively address the challenges with which the organisation is faced. Research limitations/implications --A one-organisation intensive case study of a multinational engineering company engaged in the design, development and manufacture of rotating turbomachinery provides the platform for the research. The research intent is to validate two frameworks in a different organisation of a similar demographic profile to those in which the frameworks were developed. The frameworks will require validating in organisations of different demographic profiles. Practical implications- The concepts advanced, and implications discussed, provide an insight into the role-based nature of leadership. The practical steps individual executives can take to develop their ability to adopt different leadership roles are highlighted. Originality/value--This monograph is an investigation into, and study of the contribution of theory that provides insight into, the process by which executives effectively mobilise organisational resources. This differs from the original contributions to theory, which focused on methodology, data gathering and validation in contrast with the current study that is focused on practical application. [ABSTRACT FROM AUTHOR]

Purpose--The research described in this article seeks to address the question of the extent to which a role-based perspective can provide insight into the distributed and networked form of leadership. Design/methodology/approach--A model provides insight into the distributed and networked form of leadership, and the roles that executives can adopt in formal, informal or temporary groups within the organisation's overall senior management team. The methodology adopted is qualitative, focusing on inquiry-based learning which enabled the authors to gather data on those aspects of the social structure within which they were embedded that related specifically to the leadership roles available to executives and the networks they formed. Findings--Generically applicable links between leadership roles are identified that provides structure to the task accomplishment networks within groups executives form when discharging their leadership responsibilities. Characterising leadership in terms of role, and the task networks that executives form, is found to facilitate improvement in the speed with which groups gain productive contributions from their members. Research limitations/implications--A case study of three demographically similar multinational engineering companies engaged in the design, development and manufacture of rotating turbo-machinery provides the platform for the research. The concepts advanced will require validating in other organisations of different demographic profiles. Practical implications--The concepts advanced, and implications discussed, provide an insight into the distributed and networked form of leadership. The practical steps individual executives can take to contribute to the speed with which groups gain productive contributions from their members are highlighted. Originality/value--This article attempts to assist executives within a senior management team to better adapt and coordinate their behaviour with other executives. In so doing, it is suggested that executives contribute more positively to the development of groups and the speed with which the groups of which they are a part gain productive contributions from their members. [ABSTRACT FROM AUTHOR]

This monograph summarizes the key influences of leadership behavior on the transformation process associated with creation of an effective and high performing team. It clarifies the key factors that are relevant to a team at each stage of the transformation process and the leadership roles that each team member can play. The role of an organization's senior management is considered both in terms of the impact it has on the transformation process within specific teams and in terms of creating the necessary organizational environment to make effective teams the norm. Some reasons why senior management behavior is often perceived as inconsistent and unhelpful are explored. Specific recommendations are made to help senior managers to adapt their behavior, and in so doing become more context-sensitive to the needs of the environment as it changes. Some tools and techniques are presented that have been found in practice to help senior managers adapt their behavior to that most appropriate at a given time, and to create the organizational infrastructure needed to make effective teams the organizational norm rather than the exception. A case study is presented illustrating the networked nature of leadership and the culture change associated with making effective teams "the way we do things around here." [ABSTRACT FROM AUTHOR]