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Background: The importance of high-quality health information for patient safety has been established in the literature, yet the impact of the professionals who are the custodians of health information is absent. Objectives: This article presents the results of a systematic literature review examining the impact of the Health Information Management (HIM) profession on patient safety. Methods: A PRISMA approach was adopted for the review of selected databases and specific journals. Titles identified as relating to HIM and patient quality were screened using Covidence® by title and abstract, followed by full text. The quality of selected articles was assessed and thematically analysed. Results: Analysis of the 8 included articles found that the key themes from the non-empirical research were data quality, information governance, corporate governance, skills and knowledge required for HIM professionals. Discussion: Most publications focussed on HIM professional involvement in maintaining standards for data quality and health records, but not the professional qualifications themselves. Conclusions: There are links between patient safety and health records, and between health records and HIM professional work. More empirical research is needed to demonstrate how qualified HIM professionals contribute to patient safety.

Aerofoils operating in a turbulent floware an efficient source of noise radiation by scattering vorticity into sound at the leading edge. Much work has been undertaken demonstrating the effectiveness by which serrations, or undulations, introduced onto the leading edge, can substantially reduce broadband leading edge interaction noise. However, most of this work is focused on sinusoidal leading edge serration profiles. In this paper, a family of serration profiles are proposed that are capable of providing significantly greater noise reductions than single-wavelength serrations at optimal conditions. This new family of profiles will be shown to reduce interaction noise through a fundamentally different noise reduction mechanism than conventional single-wavelength profiles. Unlike single-wavelength profiles, which produce a single compact dominant source region per serration wavelength, these new profiles are designed to produce two or more dominant compact sources per serration wavelength of roughly the same source strength, that are separated in the streamwise direction. Since these sources are arranged to be closer together than the turbulence length-scale, they are highly coherent and, at certain frequencies, radiate exactly 180º out of phase leading to very high levels of noise reduction in the far field. The experimental noise reduction spectra are compared against an analytic model obtained as a solution of the acoustic wave equation using the Wiener-Hopf technique. These are shown to be unable to capture the main features of the noise reduction spectra. A simple model has therefore been developed to explain the noise reduction mechanism for these new profiles, based on interference between a sources distributed along the leading edge. Good qualitative agreement is obtained with the experimental results.

Data availability: Data will be made available on request. Copyright © 2022 The Author(s). This paper is a predominantly experimental study into the use of porosity located downstream of an aerofoil leading edge for the reduction of turbulence interaction noise. Locating the porosity downstream of the leading edge has been shown to be beneficial in reducing the aerodynamic performance penalty compared with locating it directly at the leading edge [1], where most of the lift is generated. Noise measurements on a flat plate with downstream porosity are compared against the case of two flat plates in a tandem configuration. In both cases, the noise reduction spectra exhibit peaks of strong noise reduction at non-dimensional frequencies of fld/Uc = n, where ld is the distance between the leading edge and the downstream edge, Uc is the convection velocity and n is an integer. To explain this behaviour requires a mechanism to be present in which a phase shift of 180◦ is introduced in the interaction process. In the paper we argue that the origin of this phase shift is due to secondary vorticity generated at the leading edge. Another key finding of this paper is that overall noise reductions are due to an effective shortening of the chord in which most of the radiation is produced by the section of the flat plate upstream of the porous section, leading to generally weaker radiation. Neither of these mechanisms have been reported previously in the literature. The paper concludes with noise measurements on a thin aerofoil with downstream porosity included, in which overall noise reductions of up to 2.8 dB are achieved. EPSRC (EP/V00686X/1) QUADPORS project; Royal Academy of Engineering (RF\201819 \ 18 \ 194); EPSRC DTP EP/N509620/1; Christ’s College, University of Cambridge; EPSRC Early Career Fellowship EP/P015980/1; Oscar Propulsion; Rolls-Royce.

Background Children with overweight or obesity are at greatly increased risk of experiencing obesity in adulthood but for reasons generally unknown some attain a healthier adult weight. This qualitative study investigated individual, social and environmental factors that might explain diverging body mass index (BMI) trajectories. This knowledge could underpin interventions to promote healthy weight. Methods This 2016 study included participants from three adult follow-ups of children who (when 7–15 years) participated in the 1985 Australian Schools Health and Fitness Survey and provided BMI data at each time point. Trajectory-based group modelling identified five BMI trajectories: stable below average, stable average, increasing from average, increasing from very high and decreasing from very high. Between six and 12 participants (38–46 years) from each BMI trajectory group were interviewed (n = 50; 60% women). Thematic analysis guided by a social-ecological framework explored individual, social and environmental influences on diet and physical activity within the work setting. Results A distinct approach to healthy behaviour was principally identified in the stable and decreasing BMI groups – we term this approach “health identity” (exemplified by “I love having a healthy lifestyle”). This concept was predominant in the stable or decreasing BMI groups when participants explained why work colleagues seemingly did not influence their health behaviour. Participants in the stable and decreasing BMI groups also more commonly reported, bringing home-prepared lunches to work, working or being educated in a health-related field, having a physically active job or situating physical activity within and around work – the latter three factors were common among those who appeared to have a more distinct “health identity”. Alcohol, workplace food culture (e.g. morning teas), and work-related stress appeared to influence weight-related behaviours, but generally these factors were similarly discussed across all trajectory groups. Conclusion Work-related factors may influence weight or weight-related behaviours, irrespective of BMI trajectory, but the concept of an individual’s “health identity” may help to explain divergent BMI trajectories. “Health identity” and its influence on health behaviour warrants further exploratory work. Electronic supplementary material The online version of this article (10.1186/s40608-019-0239-3) contains supplementary material, which is available to authorized users.

This work investigates the effects of a moving flame front on the thermoacoustic oscillations in nonuniform combustors considering both the cavity and intrinsic resonant feedbacks. This theoretical...

Objective: Our aim was to systematically review qualitative evidence regarding the experiences and perceptions of General Practitioners and the factors influencing retention in remote areas of Canada and Australia. The objectives were to identify gaps and inform policy to improve retention of remote doctors, which should in turn reduce health inequalities for remote communities. Design: Meta-aggregation of qualitative studies of General Practitioners and general practice registrars who had worked in a remote area of Australia or Canada for a minimum of 1 year and/or were intending to stay remote long term in their current placement. Results: Six synthesised findings were identified: peer and professional support, organisational support, uniqueness of remote lifestyle and work, burnout and time off, personal family issues and cultural and gender issues. Conclusions: Long-term retention of doctors in remote areas of Australia and Canada is influenced by a range of negative and positive perceptions, and experiences with key factors being professional, organisational and personal. All 6 synthesised findings span a spectrum of policy domains and service responsibilities, and therefore, a central coordinating body could be well placed to implement a multifactorial retention strategy.

This chapter provides a brief history of health records development through the ages, from ancient Mesopotamian clay tablets through to today's electronic health record. An understanding of where we have come from informs future direction and enhances knowledge. While the content and method has evolved, the need to document health information has been consistent for over 4000 years. The central premise has always been to support quality health care through quality information. This chapter will explore the link between health records and patient safety.

We present a constructive procedure for the calculation of 2-D potential flows in periodic domains with multiple boundaries per period window. The solution requires two steps: (i) a conformal mapping from a canonical circular domain to the physical target domain, and (ii) the construction of the complex potential inside the circular domain. All singly periodic domains may be classified into three distinct types: unbounded in two directions, unbounded in one direction, and bounded. In each case, we relate the target periodic domain to a canonical circular domain via conformal mapping and present the functional form of prototypical conformal maps for each type of target domain. We then present solutions for a range of potential flow phenomena including flow singularities, moving boundaries, uniform flows, straining flows and circulatory flows. By phrasing the solutions in terms of the transcendental Schottky--Klein prime function, the ensuing solutions are valid for an arbitrary number of obstacles per period window. Moreover, our solutions are exact and do not require any asymptotic approximations., Comment: 29 pages; 7 figures; submitted to TCFD in Dec 2019

This paper presents a rapid numerical method for predicting the aerodynamic noise generated by foam-like porous aerofoils. In such situations, particularly for high-frequency noise sources, Darcy’s law may be unsuitable for describing the pressure jump across the aerofoil. Therefore, an inertial Forchheimer correction is introduced. This results in a non-linear boundary condition relating the pressure jump across the material to the fluid displacement. We aim to provide a quick, semi-analytical model that incorporates such non-linear effects without requiring a full turbulent simulation. The numerical scheme implemented is based on local Mathieu function expansions, leading to a semi-analytical boundary spectral method that is well-suited to both linear and non-linear boundary conditions (including boundary conditions more general than the Forchheimer correction). In the latter case, Newton’s method is employed to solve the resulting non-linear system of equations for the unknown coefficients. Whilst the physical model is simplified to consider just the scattering by a thin porous aerofoil with no background flow, when the non-linear inertial correction is included good agreement is seen between the model predictions and both experimental results and large eddy simulations. It is found that for sufficiently low-permeability materials, the effects of inertia can outweigh the noise attenuation effects of viscosity. This helps explain the discrepancy between experimental results and previous (linear) low-fidelity numerical simulations or analytical predictions, which typically overestimate the noise reduction capabilities of porous aerofoils.

This paper is predominantly an experimental study into the reduction of turbulence - aerofoil interaction noise by the introduction of aerofoil porosity. In this paper we study three scenarios applied to flat plates: (a) when the flat plate is fully porous, (b) when the flat plate is partially porous from the leading edge and (c) when porosity is introduced downstream of the leading edge. This paper shows that the noise reduction spectra collapse when plotted against non-dimensional frequency fl/U, where l is the length of porous section and U is the flow velocity. Narrow band measurements on a partially porous aerofoil have shown that its noise reduction spectra is characterised by a number of narrow peaks. This paper proposes two main mechanisms for explaining this behaviour. The noise reduction mechanisms are validated against noise reductions measured on a realistic aerofoil at relatively low angles of attack. One of the key findings of this paper is that, by using only a single row of holes downstream of the aerofoil leading edge one can obtain significant levels of noise reduction. This use of downstream porosity is specifically shown to be capable of providing low-frequency noise reductions without increasing the radiated noise at higher frequencies.

We present a solution for the scattered field caused by an incident wave interacting with an infinite cascade of blades with complex boundary conditions. This extends previous studies by allowing the blades to be compliant, porous or satisfying a generalised impedance condition. Beginning with the convected wave equation, we employ Fourier transforms to obtain an integral equation amenable to the Wiener--Hopf method. This Wiener--Hopf system is solved using a method that avoids the factorisation of matrix functions. The Fourier transform is inverted to obtain an expression for the acoustic potential function that is valid throughout the entire domain. We observe that the principal effect of complex boundary conditions is to perturb the zeros of the Wiener--Hopf kernel, which correspond to the duct modes in the inter-blade region. We focus efforts on understanding the role of porosity, and present a range of results on sound transmission and generation. The behaviour of the duct modes is discussed in detail in order to explain the physical mechanisms behind the associated noise reductions. In particular, we show that cut-on duct modes do not exist for arbitrary porosity coefficients. Conversely, the acoustic modes are unchanged by modifications to the boundary conditions. Consequently, we observe that even modest values of porosity can result in reductions in the sound power level of $5$ dB for the first mode and $20$ dB for the second mode. The solution is essentially analytic (the only numerical requirements are matrix inversion and root finding) and is therefore extremely rapid to compute., 40 pages

Background Fathers’ attitudes and actions can positively or negatively affect mothers’ intentions to breastfeed, breastfeeding duration and exclusivity. In-depth information about fathers’ perspectives on breastfeeding are largely absent in the literature about infant feeding. The objective of this research was to investigate how fathers view breastfeeding. Methods This mixed method study recruited Tasmanian fathers with children

When the pressure fluctuations caused by turbulence vorticity in the boundary layer are scattered by a sharp trailing edge, acoustic energy is generated and propagated to the far field. This trailing edge noise is emitted from aircraft wings, turbomachinery blades, wind turbine blades, helicopter blades, etc. Being dominant at high frequencies, this trailing-edge noise is a key element that annoys human hearing. This article covers virtually the entire landscape of modern research into trailing-edge noise including theoretical developments, numerical simulations, wind tunnel experiments, and applications of trailing-edge noise. The theoretical approach includes Green’s function formulations, Wiener–Hopf methods that solve the mixed boundary-value problem, Howe’s and Amiet’s models that relate the wall pressure spectrum to acoustic radiation. Recent analytical developments for poroelasticity and serrations are also included. We discuss a hierarchy of numerical approaches that range from semi-empirical schemes that estimate the wall pressure spectrum using mean-flow and turbulence statistics to high-fidelity unsteady flow simulations such as Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) that resolve the sound generation and scattering process based on the first-principles flow physics. Wind tunnel experimental research that provided benchmark data for numerical simulations and unravel flow physics is reviewed. In each theoretical, numerical, and experimental approach, noise control methods for mitigating trailing-edge noise are discussed. Finally, highlights of practical applications of trailing-edge noise prediction and reduction to wind turbine noise, fan noise, and rotorcraft noise are given. The current challenges in each approach are summarized with a look toward the future developments. The review could be useful as a primer for new researchers or as a reference point to the state of the art for experienced professionals.

This paper investigates the effects of finite flat porous extensions to semi-infinite impermeable flat plates in an attempt to control trailing-edge noise through bio-inspired adaptations. Specifically the problem of sound generated by a gust convecting in uniform mean steady flow scattering off the trailing edge and permeable-impermeable junction is considered. This setup supposes that any realistic trailing-edge adaptation to a blade would be sufficiently small so that the turbulent boundary layer encapsulates both the porous edge and the permeable-impermeable junction, and therefore the interaction of acoustics generated at these two discontinuous boundaries is important. The acoustic problem is tackled analytically through use of the Wiener-Hopf method. A two-dimensional matrix Wiener-Hopf problem arises due to the two interaction points (the trailing edge and the permeable-impermeable junction). This paper discusses a new iterative method for solving this matrix Wiener-Hopf equation which extends to further two-dimensional problems in particular those involving analytic terms that exponentially grow in the upper or lower half planes. This method is an extension of the commonly used "pole removal" technique and avoids the needs for full matrix factorisation. Convergence of this iterative method to an exact solution is shown to be particularly fast when terms neglected in the second step are formally smaller than all other terms retained. The final acoustic solution highlights the effects of the permeable-impermeable junction on the generated noise, in particular how this junction affects the far-field noise generated by high-frequency gusts by creating an interference to typical trailing-edge scattering. This effect results in partially porous plates predicting a lower noise reduction than fully porous plates when compared to fully impermeable plates., LaTeX, 20 pp., 19 graphics in 6 figures

This paper presents a generalization of a recent iterative approach to solving a class of 2 × 2 matrix Wiener–Hopf equations involving exponential factors. We extend the method to square matrices of arbitrary dimension n , as arise in mixed boundary value problems with n junctions. To demonstrate the method, we consider the classical problem of scattering a plane wave by a set of collinear plates. The results are compared to other known methods. We describe an effective implementation using a spectral method to compute the required Cauchy transforms. The approach is ideally suited to obtaining far-field directivity patterns of utility to applications. Convergence in iteration is fastest for large wavenumbers, but remains practical at modest wavenumbers to achieve a high degree of accuracy. This article is part of the theme issue ‘Modelling of dynamic phenomena and localization in structured media (part 2)’.

Aeroacoustics continues to be a subject of active research now nearly 70 years since its genesis in the 1950s at the dawn of the jet age. Although fundamentally a branch of fluid mechanics, aeroacoustics has grown into a discipline of its own right with well-defined scientific and technological missions, namely, modelling both the generation and outward propagation of sound, and more critically developing novel noise-reduction techniques. Given the ongoing expansion of civil aviation set against the introduction of ever more stringent regulations on aviation noise, it is imperative to reduce aircraft noise even further. Moreover, unexplored noise sources from diverse areas, such as that generated by flow over unmanned aerial vehicles, wind turbines and the forthcoming urban air mobility vehicles, present further challenges.

This paper presents a new approach to solving acoustic scattering problems: the Unified Transform method. This spectral, boundary-based collocation method can be readily applied to acoustic scattering by disjoint two-dimensional structures, and, for the purposes of this paper, is illustrated in the case of multiple flat plates, which also addresses the additional difficulty of mathematical singularities in the scattered field due to diffraction at sharp edges. Fluid-structure interaction may also be incorporated into the method, such as plate elasticity, which when applied to aerofoil trailing edges, is known to reduce aerodynamic noise. While a range of examples are illustrated to show the versatility of the method, attention is in particular given to the scattering of quadrupole sources by rigid plates with finite elastic extensions. It is seen that whilst a fully elastic plate is most beneficial acoustically, plates with only small extensions can considerably reduce the far-field sound power versus a fully rigid plate.

This paper employs the unified transform to present a boundary-based spectral collocation method suitable for solving acoustic scattering problems. The method is suitable for both interior and exterior scattering problems, and may be extended to three dimensions. A number of simple two-dimensional examples are presented to illustrate the versatility of this method, and, upon comparison with other spectral methods, or boundary-based methods the approach presented in this paper is shown to be very competitive.

ObjectiveTo investigate mothers’ infant feeding experiences (breastfeeding/formula milk feeding) with the aim of understanding how women experience cessation of exclusive breastfeeding.DesignMultimethod, qualitative study; questionnaire, focus groups and interviews.SettingNorthern and Southern Tasmania, Australia.Participants127 mothers of childbearing age from a broad sociodemographic context completed a questionnaire and participated in 22 focus groups or 19 interviews across Tasmania, 2011–2013.ResultsMothers view breastfeeding as ‘natural’ and ‘best’ and formula milk as ‘wrong’ and ‘unnatural’. In an effort to avoid formula and prolong exclusive breastfeeding, mothers will endure multiple issues (eg, pain, low milk supply, mastitis, public shaming) and make use of various forms of social and physical capital; resources such as father/partner support, expressing breast milk, bottles and dummies. The cessation of exclusive breastfeeding was frequently experienced as unexpected and ‘devastating’, leaving mothers with ‘breastfeeding grief’ (a prolonged sense of loss and failure).Conclusions and implicationsFor many mothers, the cessation of exclusive breastfeeding results in lingering feelings of grief and failure making it harmful to women’s emotional well-being. Reframing breastfeeding as a family practice where fathers/partners are incorporated as breastfeeding partners has the potential to help women negotiate and prolong breastfeeding. Proactive counselling and debriefing are needed to assist women who are managing feelings of ‘breastfeeding grief’.

Body mass index (BMI) trajectories that improve over the lifecourse result in better cardiometabolic profiles, but only a small proportion of children of an unhealthy weight show improving BMI trajectories. This study aimed to examine the childhood factors related to diverging BMI trajectories from childhood into adulthood using data from the Childhood Determinants of Adult Health study. A convergent parallel mixed methods design was used. Quantitative data (n = 2206) came from the first (2004–06) and second (2009–11) adult follow-ups of 8498 Australian children (7–15 years) assessed in 1985. Using BMI z-scores, group-based trajectory modelling identified five trajectory groups: Persistently Low, Persistently Average, High Decreasing, Average Increasing and High Increasing. Qualitative data (n = 50) were collected from a sub-group (2016; 38–46 years). Semi-structured interviews with 6–12 participants from each BMI trajectory group focused on individual, social and environmental influences on weight, diet and physical activity across the lifecourse. Log multinomial regression modelling estimated relative risks of trajectory group membership across childhood demographic, behavioural, health, parental and school factors. Qualitative data were thematically analysed using a constant comparative approach. Childhood factors influenced BMI trajectories. Paternal education, main language spoken, alcohol and self-rated health were significant quantitative childhood predictors of BMI trajectory. A distinct ‘legacy effect’ of parental lifestyle influences during childhood was apparent among interview participants in the Stable and High Decreasing groups, a strong and mostly positive concept discussed by both men and women in these groups and persisting despite phases of unhealthy behaviours. In contrast, the ‘legacy effect’ was much weaker in the two Increasing BMI groups. This study is the first to simultaneously identify important quantitative and qualitative childhood factors related to divergent BMI trajectories, and to observe a legacy effect of parents' lifestyle behaviours on divergent BMI trajectories. This work provides direction for further exploration of the factors driving divergent BMI trajectories.

The Kutta condition is applied to aerofoils with sharp trailing edges to allow for viscous effects to be considered within a simplified system of equations that are inviscid. This paper discusses in detail the inclusion of an unsteady Kutta condition at a sharp trailing edge during gust–aerofoil interaction and illustrates how the analytic solution for the far-field noise generated by this interaction changes if the unsteady Kutta condition is neglected, or more precisely, if the unsteady pressure is permitted to be singular at the trailing edge. The analytic solution, both with and without the unsteady Kutta condition, is compared with numerical results that have no imposed unsteady Kutta condition. Importantly the results agree well only when the unsteady Kutta condition is neglected in the analytic solution. This paper highlights where the far-field acoustics are most affected by neglecting the unsteady Kutta condition for a variety of singularities that can occur in the unsteady pressure at the trailing edge and shows that results permitting different behaviour in the unsteady surface pressure at the trailing edge could give significantly different far-field noise predictions, even though the surface pressure elsewhere along the aerofoil surface agrees with benchmark solutions.

An asymptotic model is constructed to analyse the interaction of turbulence generated far upstream with a thin elliptic-nosed solid body in uniform flow. The leading-edge stagnation point causes significant deformation of incident vorticity, and hence our analysis focuses on the region of size scaling with the nose radius close to the stagnation point. Rapid distortion theory is used to separate the flow field generated by a single unsteady gust perturbation into a convective non-acoustic part, containing the evolution of the upstream vortical disturbance, and an acoustic part generated by the interaction of the vorticity with the solid surface, as is typical in gust–aerofoil interaction theory. Using single-frequency gust response solutions, along with a von Kármán energy spectrum, we find the turbulent pressure spectrum generated by homogeneous isotropic turbulence incident from far upstream. Both high- and low-frequency gusts are considered to allow approximations to be found for the turbulent pressure spectra close to the leading edge, and far from the body close to the incident stagnation streamline. Good agreement is shown between the asymptotic results for the near- and far-field leading-edge turbulent pressure spectra and recent experimental findings.

Background: The eastern Indonesian province of Nusa Tenggara Timur (NTT) has an infant mortality rate of 45 per 1000, higher than the national average (28/1000). Exclusive breastfeeding, important for improving newborn and infant survival, is encouraged among hospitalized infants in Kupang, the provincial capital of NTT. However, barriers to hospitalized infants receiving breast milk may exist. Objectives: This study explored the barriers and enablers to exclusive breastfeeding among sick and low birth weight hospitalized infants in Kupang, NTT. The attitudes and cultural beliefs of health workers and mothers regarding the use of donor breast milk (DBM) were also explored. Methods: A mixed-methods study using a convergent parallel design was conducted. A convenience sample of 74 mothers of hospitalized infants and 8 hospital staff participated in semi-structured interviews. Facility observational data were also collected. Analysis was conducted using Davis’s barrier analysis method. Results: Of the 73 questionnaires analyzed, we found that 39.7% of mothers retrospectively reported exclusively breastfeeding and 37% of mothers expressed breast milk. Expressing was associated with maternal reported exclusive breastfeeding χ2 (1, N = 73) = 6.82, P = .009. Staff supported breastfeeding for sick infants, yet mothers could only access infants during set nursery visiting hours. No mothers used DBM, and most mothers and staff found the concept distasteful. Conclusions: Increasing mothers’ opportunities for contact with infants is the first step to increasing exclusive breastfeeding rates among hospitalized infants in Kupang. This will facilitate mothers to express their breast milk, improve the acceptability of DBM, and enhance the feasibility of establishing a DBM bank.

This paper presents an analytic solution for gust–aerofoil interaction noise for flat plates with spanwise-varying periodic leading edges in uniform mean flow. The solution is obtained by solving the linear inviscid equations via separation of variables and the Wiener–Hopf technique, and is suitable for calculating the far-field noise generated by any leading edge with a single-valued piecewise linear periodic spanwise geometry. Acoustic results for homogeneous isotropic turbulent flow are calculated by integrating the single-gust solution over a wavenumber spectrum. The far-sound pressure level is calculated for five test-case geometries; sawtooth serration, slitted $v$-root, slitted $u$-root, chopped peak and square wave, and compared to experimental measurements. Good agreement is seen over a range of frequencies and tip-to-root ratios (varying the sharpness of the serration). The analytic solution is then used to calculate the propagating pressure along the leading edge of the serration for fixed spanwise wavenumbers, i.e. only the contribution to the surface pressure which propagates to the far field. Using these results, two primary mechanisms for noise reduction are discussed; tip and root interference, and a redistribution of energy from cuton modes to cutoff modes. A secondary noise-reduction mechanism due to nonlinear features is also discussed and seen to be particularly important for leading edges with very narrow slits.

"Ground effect" refers to the enhanced performance enjoyed by fliers or swimmers operating close to the ground. We derive a number of exact solutions for this phenomenon, thereby elucidating the underlying physical mechanisms involved in ground effect. Unlike previous analytic studies, our solutions are not restricted to particular parameter regimes such as "weak" or "extreme" ground effect, and do not even require thin aerofoil theory. Moreover, the solutions are valid for a hitherto intractable range of flow phenomena including point vortices, uniform and straining flows, unsteady motions of the wing, and the Kutta condition. We model the ground effect as the potential flow past a wing inclined above a flat wall. The solution of the model requires two steps: firstly, a coordinate transformation between the physical domain and a concentric annulus, and secondly, the solution of the potential flow problem inside the annulus. We show that both steps can be solved by introducing a new special function which is straightforward to compute. Moreover, the ensuing solutions are simple to express and offer new insight into the mathematical structure of ground effect. In order to identify the missing physics in our potential flow model, we compare our solutions against new experimental data. The experiments show that boundary layer separation on the wing and wall occurs at small angles of attack, and we suggest ways in which our model could be extended to account for these effects., Comment: Main body: 10 pages & 3 figures; supplementary material: 6 pages & 5 figures. Submitted to JFM Rapids

Leading- and trailing-edge serrations have been widely used to reduce the leading- and trailing-edge noise in applications such as contra-rotating fans and large wind turbines. Recent studies show that these two noise problems can be modelled analytically using the Wiener-Hopf method. However, the resulting models involve infinite-interval integrals that cannot be evaluated analytically, and consequently implementing them poses practical difficulty. This paper develops easily-implementable noise prediction models for flat plates with serrated leading and trailing edges, respectively. By exploiting the fact that high-order modes are cut-off and adjacent modes do not interfere in the far field except at sufficiently high frequencies, an infinite-interval integral involving two infinite sums is approximated by a single straightforward sum. Numerical comparison shows that the resulting models serve as excellent approximations to the original models. Good agreement is also achieved when the leading-edge model predictions are compared with experimental results for sawtooth serrations of various root-to-tip amplitudes. Importantly, the models developed in this paper can be evaluated robustly in a very efficient manner. For example, a typical far-field noise spectrum can be calculated within milliseconds for both the trailing- and leading-edge noise models on a standard desktop computer. Due to their efficiency and ease of numerical implementation, these models are expected to be of particular importance in applications where a numerical optimization is likely to be needed., Comment: 24 pages, 10 figures