Graeme Keith
København, Region Hovedstaden, Danmark
8 t følgere
500+ forbindelser
Om
- Advisor in the application of quantitative methods to risk management and strategy…
Artikler af Graeme
Aktivitet
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View my verified achievement from #Archer. Organizations have long recognized the need to standardize #risk #management practices for consistency in…
View my verified achievement from #Archer. Organizations have long recognized the need to standardize #risk #management practices for consistency in…
Graeme Keith synes godt om dette
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WOW! 2024 is coming to a close! I have had my busiest year ever. More travel than ever, globally. Working on more #GRC #RFPs and buyer engagements…
WOW! 2024 is coming to a close! I have had my busiest year ever. More travel than ever, globally. Working on more #GRC #RFPs and buyer engagements…
Graeme Keith synes godt om dette
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It was a pleasure being part of the CoreStream GRC #GRC Christmas party in #London last week
It was a pleasure being part of the CoreStream GRC #GRC Christmas party in #London last week
Graeme Keith synes godt om dette
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Udgivelser
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Flow-generated pressure pulsations on oil & gas installations
Proceedings of the 17th International Congress on Sound and Vibration
Violent pressure pulsations in a pipeline system are usually the product of machinery such as reciprocating or screw compressors. Nonetheless, under certain conditions pressure pulsations vigorous enough to damage fittings and equipment may be generated by flow alone. This paper describes the mechanisms by which these phenomena may arise, how they may be modelled and the conclusions that may be drawn from these models in terms of treating phenomena or, better still, avoiding them in the first…
Violent pressure pulsations in a pipeline system are usually the product of machinery such as reciprocating or screw compressors. Nonetheless, under certain conditions pressure pulsations vigorous enough to damage fittings and equipment may be generated by flow alone. This paper describes the mechanisms by which these phenomena may arise, how they may be modelled and the conclusions that may be drawn from these models in terms of treating phenomena or, better still, avoiding them in the first place.
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Friction factor jump in honeycomb seals explained by flow-acoustic interactions
ASME GT2009-60337
In a series of experiments over flat plate honeycomb seal surfaces with deep cavities, Ha and Childs [1] have reported, under certain conditions, sudden “jumps” in the friction factor, which possibly could seriously impair honeycomb seal rotordynamic performance. This phenomenon was never fully explained before. In this study, the results have been investigated both analytically and computationally in the light of the Strouhal number dependency, and it was found that the friction factor jump…
In a series of experiments over flat plate honeycomb seal surfaces with deep cavities, Ha and Childs [1] have reported, under certain conditions, sudden “jumps” in the friction factor, which possibly could seriously impair honeycomb seal rotordynamic performance. This phenomenon was never fully explained before. In this study, the results have been investigated both analytically and computationally in the light of the Strouhal number dependency, and it was found that the friction factor jump phenomenon is nearly uniquely correlated with the Strouhal number of the flow. This lends strong credence to the hypothesis that the friction factor jump is due to a flow-acoustic interaction. Indeed, the measured friction factors were found to jump at the exact Strouhal Numbers where the energy transfer rate from the flow mode to the acoustic mode were at a maximum. CFD direct numerical simulations at the configurations of friction factor jump also demonstrate a lock-in between the acoustic and vortex shedding frequencies.
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High wavenumber acoustic radiation from a thin-walled axisymmetric cylinder
Journal of Sound and Vibration 255 (1) 129-146
The radiation from an axisymmetric thin-walled cylinder is determined by using the Geometrical Theory of Di!raction. The non-uniformities associated with this theory are corrected by using uniform asymptotic techniques, and the farfield velocity potential is calculated everywhere. The theory provides a paradigm for interpretation of geometrical features of the directivity pattern in the farfield, and the results are discussed from this perspective. Comparison is made with analytical results…
The radiation from an axisymmetric thin-walled cylinder is determined by using the Geometrical Theory of Di!raction. The non-uniformities associated with this theory are corrected by using uniform asymptotic techniques, and the farfield velocity potential is calculated everywhere. The theory provides a paradigm for interpretation of geometrical features of the directivity pattern in the farfield, and the results are discussed from this perspective. Comparison is made with analytical results obtained by using the Wiener-Hopf technique and the agreement is shown to be excellent. In particular, the uniform asymptotic techniques give the correct farfield form of the velocity potential in the principal lobe and predict the value at the peak of the principal lobe very accurately. This work provides a theoretical basis for the investigation of the radiation from asymmetric cylinder apertures, which has important applications in the noise reduction of aircraft, and which is discussed in a companion paper.
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High wavenumber acoustic radiation from a thin-walled scarfed cylinder
Journal of Sound and Vibration 255 (1) 147-160
The analysis of the radiation from an axisymmetric duct using the Geometrical Theory of Di!raction and uniform asymptotics, presented in a companion paper, is extended to an asymmetric, scarfed cylinder. The generic theory from the application to axisymmetric cylinders is briefly recapitulated and the geometrical calculations necessary for the analysis of the scarfed cylinder are presented in detail. The scarfed cylinder is used as a model for a novel technique of noise reduction in modern…
The analysis of the radiation from an axisymmetric duct using the Geometrical Theory of Di!raction and uniform asymptotics, presented in a companion paper, is extended to an asymmetric, scarfed cylinder. The generic theory from the application to axisymmetric cylinders is briefly recapitulated and the geometrical calculations necessary for the analysis of the scarfed cylinder are presented in detail. The scarfed cylinder is used as a model for a novel technique of noise reduction in modern aeroengines in which the intake is directed a little upward to try and direct noise radiation away from the ground. We do not carry out a full parameter study, but preliminary results from this work suggest the technique has significant potential noise reduction benefits.
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Practical Computational Aeroacoustics for Compact Surfaces in Low Mach Number Flows
Acta Acustica 97 14-23
Sound generation has been widely studied using numerical hybrid methods. The aim of this paper is to introduce a flexible procedure where the acoustic source data may be synthesized and stored from commercially available Computational Fluid Dynamics (CFD) codes and later used to predict radiated noise. Different applications will require either analytical or numerical methods for the radiation calculations. Attention is restricted to low Mach number flows where the noise generation is dominated…
Sound generation has been widely studied using numerical hybrid methods. The aim of this paper is to introduce a flexible procedure where the acoustic source data may be synthesized and stored from commercially available Computational Fluid Dynamics (CFD) codes and later used to predict radiated noise. Different applications will require either analytical or numerical methods for the radiation calculations. Attention is restricted to low Mach number flows where the noise generation is dominated by the interaction of the flow with a surface with at least one characteristic dimension short compared to the wavelength of interest. This makes it possible to focus on the surface source term of the Ffowcs Williams-Hawkings equation. In this paper, in order to illustrate the basic method for storing and utilizing data from the CFD analysis, the flow past a circular cylinder at a Reynolds number of Re = 1.4. 105 will be studied, where the cylinder is compact and therefore the analytical free-space Green's function may be used.
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Problems and solutions in the application of the Parabolic Wave Equation to outdoor noise propagation prediction
Proceed- ings of the Joint Baltic-Nordic Acoustical Meeting
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Rooting out causes for failure analysis
Touch Oil & Gas Review 2011
The Deepwater Horizon disaster was a terrible reminder of the consequences of equipment failure on facilities operating in challenging environments. Thankfully catastrophes on the scale of the Deepwater Horizon are rare, but equipment failure is a daily occurrence on installations around the globe. The consequences range from short unexpected downtime, to a total stop on production, from a brief burst of flaring to lasting environmental damage and from the momentary discomfiture of a worker to…
The Deepwater Horizon disaster was a terrible reminder of the consequences of equipment failure on facilities operating in challenging environments. Thankfully catastrophes on the scale of the Deepwater Horizon are rare, but equipment failure is a daily occurrence on installations around the globe. The consequences range from short unexpected downtime, to a total stop on production, from a brief burst of flaring to lasting environmental damage and from the momentary discomfiture of a worker to incapacity or death.
Whenever equipment fails to meet expectations or fails altogether, we must understand what went wrong so that we can safeguard against it ever happening again. A good explanation not only helps you prevent a failure from reoccurring it can help identify systematic weaknesses that might result in other failures. -
The use of microperforated plates to attenuate cavity resonances
Journal of the Acoustical Society of America 120 (4) 1851-1858
The use of microperforated plates to introduce damping in a closed cavity is examined. By placing a microperforated plate well inside the cavity instead of near a wall as traditionally done in room acoustics, high attenuation can be obtained for specific acoustic modes, compared with the lower attenuation that can be obtained in a broad frequency range with the conventional position of the plate. An analytical method for predicting the attenuation is presented. The method involves finding…
The use of microperforated plates to introduce damping in a closed cavity is examined. By placing a microperforated plate well inside the cavity instead of near a wall as traditionally done in room acoustics, high attenuation can be obtained for specific acoustic modes, compared with the lower attenuation that can be obtained in a broad frequency range with the conventional position of the plate. An analytical method for predicting the attenuation is presented. The method involves finding complex eigenvalues and eigenfunctions for the modified cavity and makes it possible to predict Green’s functions. The results, which are validated experimentally, show that a microperforated plate can provide substantial attenuation of modes in a cavity. One possible application of these findings is the treatment of boiler tones in heat-exchanger cavities.
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Whirl frequency dependent Alford forces in axial compressors
Proceedings of International Gas Turbine Institute
Explicit closed form expressions are derived for the whirl frequency dependence of the Alford force in an axial compressor operating in steady-state away from the onset of rotating stall. The analysis includes the compressor flow dynamics using the Moore-Greitzer approximation. By asymptotic expansion in terms of the whirl orbit amplitude, expressions for the direct and cross-coupling impedance are obtained analytically. Several components in the cross-coupling impedance are shown to change…
Explicit closed form expressions are derived for the whirl frequency dependence of the Alford force in an axial compressor operating in steady-state away from the onset of rotating stall. The analysis includes the compressor flow dynamics using the Moore-Greitzer approximation. By asymptotic expansion in terms of the whirl orbit amplitude, expressions for the direct and cross-coupling impedance are obtained analytically. Several components in the cross-coupling impedance are shown to change phase as the whirl frequency transits the rotating stall frequency. This implies that for a given compressor design the Alford force can be stabilizing or destabilizing depending on flow rate and whirl frequency. Further, the analysis shows that the coupling between mean flow quantities and rotor whirl is of second order. Thereby, the present asymptotic expansion results in a fluid-structure coupling model, which is consistent in accuracy with usual linearized rotordynamic analysis.
Andre forfattere
Fag/kurser
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Advanced Decision Analysis with Portfolio and Project Modelling
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Cambridge University, Judge Business School, Executive Education, Corporate Finance.
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Lloyd's Register Leadership Development Programme
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Petroleum Risk and Decision Analysis
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Stanford Strategic Decision and Risk Management: Strategic Portfolio Decisions
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Sprog
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English
Modersmåls- eller tosprogsfærdighed
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Danish
Modersmåls- eller tosprogsfærdighed
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Norwegian
Begrænset praktisk færdighed
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French
Begrænset praktisk færdighed
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What a great time with Kyle Martin of NAVEX today. He came to my office in #Milwaukee to record the next episode of #GRCafterHours in which we…
What a great time with Kyle Martin of NAVEX today. He came to my office in #Milwaukee to record the next episode of #GRCafterHours in which we…
Graeme Keith synes godt om dette
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'Enterprise Risk Management' are words that belong to experts, and words that seem to hold more and more weight. Well worth investigating how to do…
'Enterprise Risk Management' are words that belong to experts, and words that seem to hold more and more weight. Well worth investigating how to do…
Graeme Keith synes godt om dette
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Over the last couple of weeks, my colleagues Shelley Migliore and Graeme Keith have been sharing our vision of #QuantERM with some of the best ERM…
Over the last couple of weeks, my colleagues Shelley Migliore and Graeme Keith have been sharing our vision of #QuantERM with some of the best ERM…
Graeme Keith synes godt om dette