Design thinking and innovation: synthesising concepts of knowledge co-creation in spaces of professional development

This paper explores how design thinking connects to concepts of knowledge creation and innovation. A case study of a knowledge sharing network in the social services sector is used to illustrate how design thinking supports Ba, the spaces for knowledge creation. Further exploration of the four enabling conditions for Ba resulted in delineation of two distinct types: relational and structural. Relational enablers support three groups of enabling conditions: interaction, shared values and communication. It is proposed that design thinking aligns well with relational enabling conditions for Ba to create the ideal spaces for knowledge creation. The group of structural enablers can assist or obstruct change and relate to the culture and management approaches of an organization, which may or may not be assisted by design thinking. However, to ensure that design thinking is not undermined, and innovation is achieved, the presence of an appropriate structural enabler is critical for success

Proper orthogonal decomposition analysis of a turbulent swirling self-excited premixed flame

Thermoacoustic oscillations constitute a serious threat to the integrity of combustion systems. The goal of the present work is to determine the effect of the equivalence ratio (φ), inlet flow velocity (U), and burner geometry on the characteristics of the self-excited oscillations and to reveal the dominant mechanisms. It also focuses on the data post-processing aiming at extracting information about the dynamics that are not captured through classical ensemble-averaging, and hence the Proper Orthogonal Decomposition technique is used. Experiments were conducted with a fully-premixed air/methane flame stabilized on a conical bluff body. Self-excited acoustic instabilities were induced by extending the length of the combustion chamber downstream of the bluff body. The flame was visualised using OH* chemiluminescence and OH PLIF at 5 kHz. Proper Orthogonal Decomposition (POD) and Fast Fourier Transform analysis were conducted on the imaging data. A strong effect of the chamber length was found, which primarily drove the generation of acoustic oscillation and flame-vortex interaction. Significant differences in the flame roll-up were found when either the burner geometry or the equivalence ratio was altered. Changes were detected in the frequency of oscillations, which showed a general trend to increase with φ and U and decrease with the length of the duct. Analysis of the POD modes allowed an estimate of the convection speed of the flame structures associated with the dominant frequency and it was found that this convection speed was about 1.5 U for most conditions studied

An experimental study of the effects of lobed nozzles on installed jet noise

Abstract: Jet noise remains a significant aircraft noise contributor, and for modern high-bypass-ratio aero-engines the strong interaction between the jet and aircraft wing leads to intensified installed jet noise. An experiment is carried out in this paper to study the effects of lobed nozzles on installed jet noise. It is found that the lobed nozzles, compared to round nozzles, have similar effects on installed jet noise for all the plate positions and Mach numbers tested. On the shielded side of the plate, the use of lobed nozzles leads to a noise reduction in the intermediate- and high-frequency regimes, which is thought to be due to a combination of enhanced jet mixing and more effective shielding effects by the flat plate. On the reflected side of the plate, noise reduction is only achieved in the intermediate frequency range; the little noise reduction or a slight noise increase observed in the high-frequency regime is likely due to enhanced jet mixing. On both sides of the plates, little noise reduction is achieved for the low-frequency noise due to the scattering of jet instability waves. This is likely to be caused by the fact that lobed nozzles cause negligible change to the dominant mode 0 (axisymmetric) jet instability waves. That the jet mean flow quickly becomes axisymmetric downstream of the jet exit could also play a role. Graphic abstract

Prediction of installed jet noise

A semianalytical model for installed jet noise is proposed in this paper. We argue and conclude that there exist two distinct sound source mechanisms for installed jet noise, and the model is therefore composed of two parts to account for these different sound source mechanisms. Lighthill’s acoustic analogy and a fourth-order space–time correlation model for the Lighthill stress tensor are used to model the sound induced by the equivalent turbulent quadrupole sources, while the trailing-edge scattering of near-field evanescent instability waves is modelled using Amiet’s approach. A non-zero ambient mean flow is taken into account. It is found that, when the rigid surface is not so close to the jet as to affect the turbulent flow field, the trailing-edge scattering of near-field evanescent waves dominates the low-frequency amplification of installed jet noise in the far-field. The high-frequency noise enhancement on the reflected side is due to the surface reflection effect. The model agrees well with experimental results at different observer angles, apart from deviations caused by the mean-flow refraction effect at high frequencies at low observer angles.The first author (B.L.) wishes to gratefully acknowledge the financial support co-funded by the Cambridge Commonwealth European and International Trust and the China Scholarship Council. The third author (I.N.) wishes to acknowledge the UK Turbulence Consortium (UKTC) for the high-performance computing time to carry out the LES simulation on ARCHER under EPSRC grant no. EP/L000261/1 and under a PRACE award on HERMIT

G-equation modelling of thermo-acoustic oscillations of partially-premixed flames

Numerical simulations aid combustor design to avoid and reduce thermo-acoustic oscillations. Non-linear heat release rate estimation and its modelling are essential for the prediction of saturation amplitudes of limit cycles. The heat release dynamics of flames can be approximated by a Flame Describing Function (FDF). To calculate an FDF, a wide range of forcing amplitudes and frequencies needs to be considered. For this reason, we present a computationally inexpensive level-set approach, which accounts for equivalence ratio perturbations on flames with arbitrarily-complex shapes. The influence of flame parameters and modelling approaches on flame describing functions and time delay coefficient distributions are discussed in detail. The numerically-obtained flame describing functions are compared with experimental data and used in an acoustic network model for limit cycle prediction. A reasonable agreement of the heat release gain and limit cycle frequency is achieved even with a simplistic, analytical velocity fluctuation model. However, the phase decay is over-predicted. For sophisticated flame shapes, only the realistic modelling of large-scale flow structures allows the correct phase decay predictions of the heat release rate response.This work was conducted within the EU 7th Framework Project Joint Technology Initiatives - Clean Sky (AMEL- Advanced Methods for the Prediction of Lean-burn Combustor Unsteady Phenomena), project number: JTI-CS-2013-3-SAGE- 06-009 / 641453. This work was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council

Democratic Leadership - A local story

Leadership is traditionally viewed as an individual property and researched from the perspective of behaviours, traits or characteristics that these individuals possess. Notions of democratic leadership can offer early childhood centres a more expansive conception of leadership to include children, teachers and families. This study explores the possibility of positioning all stakeholders in an early childhood centre as leaders by repositioning leadership as a jointly constructed, emergent process. Drawing on an existing feature of the kindergarten programme, that of regular excursions within the local community, connections are interwoven between children’s inquires, democratic principles and elements of place based education. Using narratives from five excursions in the local community the study experiments with Leadership-as-practice to analyse how these excursions fostered democratic and inclusive participation of children and adults. Inquiry as a form of participatory democracy is a key feature of decision-making and provides a common purpose for community excursions while encouraging leadership opportunities. The study reveals the potential of leadership-as-practice, underpinned by democratic values as an approach to leadership in early childhood organisations, enabling leader/follower roles to be blurred and learning to be co constructed during dialogue. The local community holds enormous capacity as a system to facilitate democratic leadership and promote place based learning and citizenship education. This study recognises that democratic leadership exists in tension with current neo liberal beliefs and therefore positions itself as a counter to the current market driven early childhood environment. The underlying belief of this study is that leadership can occur as a collaborative practice, emerging through day to day experiences and seeks to contribute to the slowly emerging body of research concerned with early childhood leadership.