Publications
71 results found
Gayen B, Griffiths RW, Hughes GO, 2014, Stability transitions and turbulence in horizontal convection, JOURNAL OF FLUID MECHANICS, Vol: 751, Pages: 698-724, ISSN: 0022-1120
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- Citations: 44
Stewart KD, Saenz JA, Hogg AM, et al., 2014, Effect of topographic barriers on the rates of available potential energy conversion of the oceans, OCEAN MODELLING, Vol: 76, Pages: 31-42, ISSN: 1463-5003
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- Citations: 11
McIntosh A, Hughes G, Pye J, 2014, Use of an air curtain to reduce heat loss from an inclined open-ended cavity
The use of an air curtain directed across the aperture of an inclined open-ended cavity is examined as a method to reduce convective losses from a heated cavity. Computational fluid dynamics (CFD) simulations were conducted in two-dimensions for a range of air curtain velocities and axial cavity orientations. The greatest relative reduction in convective losses with an air curtain resulted when the cavity aperture plane was vertical (i.e. horizontal cavity axis). For cavities whose axis was inclined to the horizontal, convective losses could still be lowered with an air curtain, but reduced jet velocities were required for optimum performance.
Gayen B, Hughes GO, Griffiths RW, 2013, Completing the Mechanical Energy Pathways in Turbulent Rayleigh-Bénard Convection, Physical Review Letters, Vol: 111, ISSN: 1079-7114
A new, more complete view of the mechanical energy budget for Rayleigh-Bénard convection is developed and examined using three-dimensional numerical simulations at large Rayleigh numbers and Prandtl number of 1. The driving role of available potential energy is highlighted. The relative magnitudes of different energy conversions or pathways change significantly over the range of Rayleigh numbers Ra ~ 10(7)-10(13). At Ra < 10(7) small-scale turbulent motions are energized directly from available potential energy via turbulent buoyancy flux and kinetic energy is dissipated at comparable rates by both the large- and small-scale motions. In contrast, at Ra ≥ 10(10) most of the available potential energy goes into kinetic energy of the large-scale flow, which undergoes shear instabilities that sustain small-scale turbulence. The irreversible mixing is largely confined to the unstable boundary layer, its rate exactly equal to the generation of available potential energy by the boundary fluxes, and mixing efficiency is 50%.
Hughes GO, Gayen B, Griffiths RW, 2013, Available potential energy in Rayleigh-Benard convection, JOURNAL OF FLUID MECHANICS, Vol: 729, ISSN: 0022-1120
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- Citations: 26
Griffiths RW, Hughes GO, Gayen B, 2013, Horizontal convection dynamics: insights from transient adjustment, JOURNAL OF FLUID MECHANICS, Vol: 726, Pages: 559-595, ISSN: 0022-1120
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- Citations: 26
Gayen B, Griffiths RW, Hughes GO, et al., 2013, Energetics of horizontal convection, JOURNAL OF FLUID MECHANICS, Vol: 716, ISSN: 0022-1120
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- Citations: 45
Stewart KD, Hughes GO, Griffiths RW, 2012, The Role of Turbulent Mixing in an Overturning Circulation Maintained by Surface Buoyancy Forcing, JOURNAL OF PHYSICAL OCEANOGRAPHY, Vol: 42, Pages: 1907-1922, ISSN: 0022-3670
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- Citations: 14
Saenz JA, Hogg AM, Hughes GO, et al., 2012, Mechanical power input from buoyancy and wind to the circulation in an ocean model, GEOPHYSICAL RESEARCH LETTERS, Vol: 39, ISSN: 0094-8276
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- Citations: 24
Gayen B, Griffiths RW, Hughes GO, et al., 2012, Direct numerical simulation of horizontal convection driven by differential heating
A numerical study based on three-dimensional direct numerical simulations are performed to investigate horizontal thermal convection in a long channel at a large Rayleigh number, Ra. Differential thermal forcing is applied at the bottom boundary over two equal regions. The steady-state circulation is achieved after the net heat flux from the boundary becomes zero. A stable thermocline forms above the cooled base and is advected over the heated part of the base, confining small-scale three-dimensional convection to the heated base and end wall region. At the endwall a narrow turbulent plume rises through the full depth of the channel. The less energetic return flow is downward in the interior, upon which eddy motions are imposed. This work, for the first time, focuses on the three dimensional instabilities and structures of the flow. The conversions of mechanical energy are examined in different regions of the flow (boundary layer, plume and interior) and help to understand overall circulation dynamics.
Stewart KD, Hughes GO, Griffiths RW, 2011, When do marginal seas and topographic sills modify the ocean density structure?, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol: 116, ISSN: 2169-9275
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- Citations: 10
Paitoonsurikarn S, Lovegrove K, Hughes G, et al., 2011, Numerical Investigation of Natural Convection Loss From Cavity Receivers in Solar Dish Applications, JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 133, ISSN: 0199-6231
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- Citations: 57
Griffiths RW, Maher N, Hughes GO, 2011, Ocean stratification under oscillatory surface buoyancy forcing, Journal of Marine Research, Vol: 69, Pages: 523-543, ISSN: 0022-2402
Laboratory experiments with overturning circulation driven by oscillatory heat fluxes at one boundary are used to explore implications, for the ocean stratification, of a cyclic fluctuation in sea-surface buoyancy forcing. Fluctuations having a range of periods spanning the timescale for global recycling of the ocean volume through the thermocline are considered, with emphasis on inter-hemispheric 'see-saw' oscillations. Episodic sinking of dense water in the oceans is represented by convection in a channel with a base that is cooled over a central region and subjected to oscillatory heating near both ends, while providing a constant total heat input. For this simplified system the time-average interior temperature is found to be insensitive to the forcing period, but does vary with oscillation amplitude, whereas the interior fluctuations increase with forcing period. The circulation and density field are significantly different from those given by a steady forcing equal to the time-average of the actual oscillatory forcing, even for high-frequency oscillations. The results indicate that the overall stratification lies between that expected from the strongest phase of deep sinking and that given by symmetric sinking in both hemispheres. Glacial cycles are predicted to involve significant temperature fluctuations in the abyssal ocean. However, they are too short for the ocean to remain in quasi-equilibrium with the changing boundary conditions.
Coman MA, Griffiths RW, Hughes GO, 2010, The sensitivity of convection from a horizontal boundary to the distribution of heating, JOURNAL OF FLUID MECHANICS, Vol: 647, Pages: 71-90, ISSN: 0022-1120
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- Citations: 8
Hughes GO, Hogg AM, Griffiths RW, 2009, Available Potential Energy and Irreversible Mixing in the Meridional Overturning Circulation, JOURNAL OF PHYSICAL OCEANOGRAPHY, Vol: 39, Pages: 3130-3146, ISSN: 0022-3670
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- Citations: 77
Prastowo T, Griffiths RW, Hughes GO, et al., 2009, Effects of topography on the cumulative mixing efficiency in exchange flows, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol: 114, ISSN: 2169-9275
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- Citations: 12
Prastowo T, Griffiths RW, Hughes GO, et al., 2008, Mixing efficiency in controlled exchange flows, JOURNAL OF FLUID MECHANICS, Vol: 600, Pages: 235-244, ISSN: 0022-1120
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- Citations: 19
Hughes GO, Griffiths RW, 2008, Horizontal convection, ANNUAL REVIEW OF FLUID MECHANICS, Vol: 40, Pages: 185-208, ISSN: 0066-4189
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- Citations: 133
O'Byrne MJ, Griffiths RW, Hughes GO, 2007, Wake flows in coastal oceans: An experimental study of topographic effects, Pages: 954-960
We consider the effects of coastal topography on the wake of an idealised headland model in a laboratory flume. Under a range of Reynolds numbers relevant to coastal oceans, we find that coherent eddies interact strongly with the headland shear layer and wake, affecting the width of the shear layer and the length of the wake. A preliminary investigation of turbulence statistics indicates that topography upstream of a headland can lead to a wider shear layer, a headland wake that extends further downstream, and enhanced horizontal diffusion out of the wake relative to the case with unperturbed oncoming flow.
Hughes GO, Griffiths RW, Mullarney JC, et al., 2007, A theoretical model for horizontal convection at high Rayleigh number, JOURNAL OF FLUID MECHANICS, Vol: 581, Pages: 251-276, ISSN: 0022-1120
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- Citations: 34
Mullarney JC, Griffiths RW, O Hughes G, 2007, The role of freshwater fluxes in the thermohaline circulation: Insights from a laboratory analogue, DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, Vol: 54, Pages: 1-21, ISSN: 0967-0637
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- Citations: 7
Coman MA, Griffiths RW, Hughes GO, 2006, Sandstrom's experiments revisited, JOURNAL OF MARINE RESEARCH, Vol: 64, Pages: 783-796, ISSN: 0022-2402
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- Citations: 24
Coman MA, Hughes GO, Kerr RC, et al., 2006, The effect of a barrier on laminar convection in a box with differentially heated endwalls, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, Vol: 49, Pages: 2903-2911, ISSN: 0017-9310
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- Citations: 2
Hogg AM, Hughes GO, 2006, Shear flow and viscosity in single-layer hydraulics, JOURNAL OF FLUID MECHANICS, Vol: 548, Pages: 431-443, ISSN: 0022-1120
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- Citations: 3
Mullarney JC, Griffiths RW, Hughes GO, 2006, The effects of geothermal heating on the ocean overturning circulation, GEOPHYSICAL RESEARCH LETTERS, Vol: 33, ISSN: 0094-8276
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- Citations: 13
Hughes GO, Griffiths RW, 2006, A simple convective model of the global overturning circulation, including effects of entrainment into sinking regions, OCEAN MODELLING, Vol: 12, Pages: 46-79, ISSN: 1463-5003
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- Citations: 69
Mullarney JC, Griffiths RW, Hughes GO, 2004, Convection driven by differential heating at a horizontal boundary, JOURNAL OF FLUID MECHANICS, Vol: 516, Pages: 181-209, ISSN: 0022-1120
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- Citations: 87
Taumoefolau T, Paitoonsurikarn S, Hughes G, et al., 2004, Experimental investigation of natural convection heat loss from a model solar concentrator cavity receiver, JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 126, Pages: 801-807, ISSN: 0199-6231
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- Citations: 126
Wong ABD, Griffiths RW, Hughes GO, 2001, Shear layers driven by turbulent plumes, JOURNAL OF FLUID MECHANICS, Vol: 434, Pages: 209-241, ISSN: 0022-1120
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- Citations: 17
Henley RW, Hughes GO, 2000, Underground fumaroles: "Excess heat" effects in vein formation, ECONOMIC GEOLOGY AND THE BULLETIN OF THE SOCIETY OF ECONOMIC GEOLOGISTS, Vol: 95, Pages: 453-466, ISSN: 0361-0128
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- Citations: 46
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