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Brown, N. (2019) Highfidelity computational fluid dynamics methods for the simulation of propeller stall flutter. A time-marching aeroelastic method developed for the study of propeller flutter is presented and validated. Propeller flutter can take many forms with stall, whirl and classical flutter being the primary responses. These types of flutter require accurate capture of the non-linear aerodynamics associated with propeller blades. Stall flutter in particular needs detailed unsteady flow modelling. With the development of modern propeller designs potentially adjusting the flutter boundary and the development of faster computing power, CFD is required to ensure accurate capture of aerodynamics. Given the lack of reliable experimental stall flutter data for propellers, the method was focused on observing the correct qualitative behaviour with a comparison made between URANS and Scale-Adaptive Simulation (SAS). Greek α s m = Model amplitude of mode m of solid s (m/kg) ζ m = Damping coefficient (-) ρ = Fluid density (kg/m 3 ) ψ s m = Normalised m th mode displacement of solid s (m/kg) ψ s = Normalised displacement of solid s (m/kg) ω m = Natural frequency of mode m Ω CV = Control volume size Subscripts i, j, k = Mesh cell indices

Aeroelastic phenomena of stall flutter are the result of the negative aerodynamic damping associated with separated flow. From this basis, an investigation has been conducted to estimate the aerodynamic damping from a time-marching aeroelastic computation. An initial investigation is conducted on the NACA 0012 aerofoil section, before transition to 3D propellers and full aeroelastic calculations. Estimates of aerodynamic damping are presented, with a comparison made between URANS and SAS. Use of a suitable turbulence closure to allow for shedding of flow structures during stall is seen as critical in predicting negative damping estimations. From this investigation, it has been found that the SAS method is able to capture this for both the aerofoil and 3D test cases.

A time-marching aeroelastic method developed for the study of propeller flutter is presented and validated. Propeller flutter can take many forms with stall, whirl and classical flutter being the primary responses. These types of flutter require accurate capture of the non-linear aerodynamics associated with propeller blades. Stall flutter in particular, due to the highly detached nature of the flow, needs detailed unsteady flow modelling. With the development of modern propeller designs potentially adjusting the flutter boundary and the development of faster computing power, CFD is required to ensure accurate capture of aerodynamics. This paper focuses on the validation of the aeroelastic method using the Commander propeller blade.

Induction bending offers a rapid, cost-effective method of producing complex convoluted pipework. The resultant bends, however, typically show unwanted geometric deformations which include wall thinning at the extrados, wall thickening at the intrados, awkward transitions on going from tangent to bend, and wrinkling at the intrados surface. All forms of geometric deformation are worse depending on the tightness of the bend and the thickness of the original pipe. Predicting the final geometry of the bend is a non-trivial problem.This article first considers the use of simple analytical models to predict the final deformed geometry of induction bends in thick-walled pipe. It then goes on to compare the predicted geometry obtained from those analytical models with the outputs from empirically derived charts and computational models. The article concludes that empirically derived charts do not offer accurate predictions of wall thinning, are not currently available for intrados wall thickening, and cannot, with confidence, be extrapolated to produce accurate results for very tight bends. Numerical models are developed which predict wall thickening and thinning for any combination of outside diameter/wall thickness/bend radius combination; however, it is concluded that their limited accuracy makes their use questionable. Elastic-plastic FEA is developed which is shown to provide the most consistently accurate means of predicting both wall thickening and wall thinning, and, while not providing a comprehensive prediction of the post-bend geometry did, nevertheless, to go some way towards predicting the overall deformed geometry including transition ramps and intrados surface wrinkling.

Internationally, there is increased emphasis on the need to reduce dependency on cars and to encourage more sustainable forms of travel, including active travel. To encourage increased levels of cycling, the focus has generally been on improving cycling infrastructure and on making cycling safer. While cycling rates have increased in many countries, including Ireland, women are often less likely to cycle than men. While there are some notable exceptions to this (for example, in the Netherlands) this phenomenon of lower cycling rates amongst women is common and research shows that the differences between male and female cycling rates can be seen from an early age. This paper explores the reasons why women are less likely to cycle than men, by examining the modal choices of school-going students, and the attitudes of their parents/guardians to their modal choices. The survey was conducted in the city of Limerick in the midwestern region of Ireland. The results show multi-factorial barriers to cycling to school for girls compared to boys. Uniforms, traffic concerns, physical efforts of cycling, effects on personal appearance, and peer-influences were factors affecting girls more than boys. Male parents/guardians did not significantly differentiate by the gender of their children in relation to factors associated with cycling to school, unlike female parents/guardians who were found to be significantly less supportive of their daughters than their sons. Additionally, parents/guardians were generally more likely to afford their male children greater independence in their school travel choices. While there are many considerations that would affect students’ perceptions towards cycling, an adjustment to the school uniform policy would, at least, remove the most significant barrier for girls. Further research must be carried out to determine how to shift the perceptions of the efforts associated with cycling, especially among girls, and how to encourage female parents/guardians to better support their daughters to cycle to school.

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