Papers by Catriona Phillips
Ocean Engineering, Dec 1, 2020
Efficient tidal turbine designs rely upon the hydrodynamic performance of the turbine blade secti... more Efficient tidal turbine designs rely upon the hydrodynamic performance of the turbine blade sections. A significant consideration for the likely power generation capacity of a tidal turbine is the effect of biofouling on the blade performance. A turbine blade surface is susceptible to large scale macrofouling, mainly from encrusters, such as barnacles and molluscs, colonising the developing surface. This paper considers the case of when a barnacle attaches to the upper (suction) surface of the blade section. Results of experiments to investigate the unsteady flow characteristics of the blade section are presented, and the modification of the hydrodynamic performance coefficients due to the presence of a barnacle is evaluated. The barnacle has no significant effect upon the lift in steady flow and unsteady flow, but there is a very large increase in the drag. Dependent upon the degree of barnacle encrustation, the effect on a turbine blade drag may be significant and lead to a degradation of a turbine predicted performance.
A copy can be downloaded for personal non-commercial research or study, without prior permission ... more A copy can be downloaded for personal non-commercial research or study, without prior permission or charge This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the Author The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the Author When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given
Brown's Vorticity Transport Model, coupled to an additional particle transport model, is used to ... more Brown's Vorticity Transport Model, coupled to an additional particle transport model, is used to simulate the development of the dust cloud that can form around a helicopter when operating in dusty or desert conditions. The flow field around a tandem rotor configuration is simulated during the final stages of landing. The time-averaged flow field around the helicopter is characterised by the existence of two stationary points immediately adjacent to the ground plane. Almost all entrainment of dust into the flow
When referring to this work, full bibliographic details including the author, title, awarding ins... more When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given Glasgow Theses Service http://theses.gla.ac.uk/
Helicopters operating close to the ground in dusty environments tend to generate large clouds of ... more Helicopters operating close to the ground in dusty environments tend to generate large clouds of dust in the surrounding air. These clouds can obscure the pilot's view of the ground and lead to a dangerous condition known as brownout. Given the intimate relationship between the induced flow field around the rotor and the process through which the particulate matter becomes airborne and is subsequently transported, it has been speculated that the design of its rotor may influence the shape and size of the dust clouds that are produced by any particular type of helicopter. This paper presents a study of the influence of two key geometric properties of the rotor on the development of these dust clouds. A particle transport model is coupled to Brown's Vorticity Transport Model to represent the dynamics of the particulate-air system surrounding a generic helicopter rotor under various flight conditions. The number of blades on the rotor is altered, whilst keeping the solidity constant, thus altering the distribution of vorticity that is released onto the ground. In addition, the twist of the blades is varied in order to investigate the effect of the resultant changes in the distribution of induced downwash on the evolution of the dust cloud. The study suggests that, in general, the larger the number of blades, and the higher the blade twist, the less dense the dust clouds that are produced under brownout conditions. It appears thus that the characteristics of the dust clouds are indeed sensitive to the geometry of the rotor and hence that careful aerodynamic design may allow the severity of brownout to be ameliorated.
The perceived need to reduce mankind's impact on the global climate motivates towards a futur... more The perceived need to reduce mankind's impact on the global climate motivates towards a future society in which a signiflcant proportion of its energy needs will be extracted from the winds and the tides of the planet. This paper shows several examples of the application of Brown's Vorticity Transport Model, originally developed to perform simulations of helicopter aeromechanics and wake
Journal of Aircraft, 2009
A computational model is presented that can be used to simulate the development of the dust cloud... more A computational model is presented that can be used to simulate the development of the dust cloud that can be entrained into the air when a helicopter is operated close to the ground in desert or dusty conditions. The physics of this problem, and the associated pathological condition known as 'brownout' where the pilot loses situational awareness as a result of his vision being occluded by dust suspended in the flow around the helicopter, is acknowledged to be very complex. The approach advocated here involves an approximation to the full dynamics of the coupled particulate-air system. Away from the ground, the model assumes that the suspended particles remain in near equilibrium under the action of aerodynamic forces. Close to the ground, this model is replaced by an algebraic sublayer model for the saltation and entrainment process. The origin of the model in the statistical mechanics of a distribution of particles governed by aerodynamic forces allows the validity of the method to be evaluated in context by comparing the physical properties of the suspended particulates to the local properties of the flow field surrounding the helicopter. The model applies in the Eulerian frame of reference of most conventional Computational Fluid Dynamics codes and has been coupled with Brown's Vorticity Transport Model. Verification of the predictions of the coupled model against experimental data for particulate entrainment and transport in the flow around a model rotor are encouraging. An application of the coupled model to analyzing the differences in the geometry and extent of the dust clouds that are produced by single main rotor and tandem-rotor configurations as they decelerate to land has shown that the location of the ground vortex and the size of any regions of recirculatory flow, should they exist, play a primary role in governing the extent of the dust cloud that is created by the helicopter.
The formation of the dust cloud that is associated with low-level helicopter operations in desert... more The formation of the dust cloud that is associated with low-level helicopter operations in desert environ- ments has been simulated using the Vorticity Transport Model together with a coupled model to represent the entrainment and subsequent transport of particulate matter through the ∞ow. A simple thin-layer theory, supported by simulations performed using the more physically-representative numerical model, is used to
The Aeronautical Journal, 2011
Significant progress has been made to date in modelling, computationally, the formation and devel... more Significant progress has been made to date in modelling, computationally, the formation and development of the dust cloud that forms in the air surrounding the rotorcraft under brownout conditions. Modern computational methods are able to replicate not only the development of the dust cloud in appropriate operational scenarios, but also the sensitivity of the shape and density of the dust cloud to the detailed design of the rotorcraft. Results so far suggest that attempts to ameliorate brownout by aerodynamic means, for instance by modifying the rotor properties, will be frustrated to some extent by the inherent instability of the flow field that is produced by the helicopter. Nonetheless, very recent advances in understanding the fundamental mechanisms that lead to the formation of the dust cloud may allow substantial progress to be made once certain elements of the basic physics of the problem are more fully understood and better quantified.
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Papers by Catriona Phillips