Jeremy Phillips - Academia.edu (original) (raw)
Papers by Jeremy Phillips
<p>Debris flow, locally known as huaycos, impact the east p... more <p>Debris flow, locally known as huaycos, impact the east part of the metropolitan city of Lima, capital of Peru. However, after many extreme events such as the one related to the 2017 “Coastal Niño” or the one in 1987, there is a lack of historical data and sufficiently accurate monitoring systems.</p><p> </p><p>The fact that this area is densely populated presents obvious challenges, from social and physical perspectives, but also some opportunities. We present our experience using open source & low cost rain gauges on previously unmonitored microwatershed, as part of a broader watershed-level monitoring system enhancement by SENAMHI (National Meteorological and Hydrological Service). We also present our experience on linking monitoring systems, debris flow modelling and community based risk management towards developing operational EWS.</p>
Frontiers in Marine Science
Journal of Volcanology and Geothermal Research
Aeroacoustic jet noise theory describes the relationship between acoustic signals and jet operati... more Aeroacoustic jet noise theory describes the relationship between acoustic signals and jet operating parameters. Based on empirical aeroacoustic relationships, a link between peak frequency and amplitude and jet diameter and velocity has been used by volcano acousticians to return the operating parameters of column generating volcanic eruptions. There are however significant differences between the nozzle geometries and structures of flows studied in the aeroacoustic literature and flows emitted from volcanic vents. These differences raise questions as to the validity of applying engineering relationships to volcanic eruptions. Combining particle image velocimetry and acoustic data we investigated the flow structures, acoustic signals and dominant source locations of jet flows emitted from three simple nozzle geometries (convergent, straight and divergent). Flows from the straight and divergent nozzles exited in a more developed flow regime than those emitted from convergent nozzles. While for the convergent nozzles dominant sound sources were located within the jet flow, the dominant signals from the straight and divergent nozzles were located in the region of the nozzle exit. Consequently, for the straight and divergent nozzles it was not possible to differentiate between signals generated by the jet flow and those generated by internal sound sources without beamforming analysis. In order to better replicate the volcanic case and in contrast to studies for industrial applications, our experimental test section was not engineered to minimise internal noise. Without acoustic treatment such as screens, choke plates and paddles, jet noise signals were contaminated by signals generated within the test rig and so, even for the convergent nozzles, the aeroacoustic relationships derived from engineering studies could not be used to retrieve the jet operating parameters. Our results indicate that in the volcanic case, the raw acoustic spectra will contain signals generated by both in-conduit and above-vent processes. Therefore inversions for volcanic jet parameters such as mass eruption rate from standard aeroacoustic relationships may be unreliable.
Scientific reports, Jan 2, 2018
Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, includ... more Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, including international air traffic. For recent major eruptions, information on the volcanic ash plume has been combined with relatively coarse-resolution meteorological model output to provide simulations of regional ash dispersal, with reasonable success on the scale of hundreds of kilometres. However, to predict and mitigate these impacts locally, significant improvements in modelling capability are required. Here, we present results from a dynamic meteorological-ash-dispersion model configured with sufficient resolution to represent local topographic and convectively-forced flows. We focus on an archetypal volcanic setting, Soufrière, St Vincent, and use the exceptional historical records of the 1902 and 1979 eruptions to challenge our simulations. We find that the evolution and characteristics of ash deposition on St Vincent and nearby islands can be accurately simulated when the wind she...
Global Environmental Change
This paper provides an example of how communities can adapt to extreme forms of environmental cha... more This paper provides an example of how communities can adapt to extreme forms of environmental change and uncertainty over the longer term. We analyse the interactions between scientists, communities and risk managers and examine the interpretation and communication of uncertain scientific information during a long-lived volcanic eruption in Tungurahua, Ecuador. This is complemented with a detailed study of the eruptions of 2006 and 2014, which exemplifies the complexity of interactions during periods of heightened volcanic activity. Our study describes how a 'shadow network' has developed outside of, but in interaction with, the formal risk management institutions in Ecuador, improving decision-making in response to heightened volcanic activity. The findings suggest that the interactions have facilitated important adaptations in the scientific advisory response during eruptions (near-real-time interpretation of the volcanic hazards), in hazard communication, and in the evacuation processes. Improved communication between stakeholders and the establishment of thresholds for evacuations have created an effective voluntary evacuation system unique to Tungurahua, allowing people to continue to maintain their livelihoods during heightened volcanic activity and associated periods of uncertainty. Understanding how shadow networks act to minimise the negative consequences of volcanic activity provides valuable insights for increasing societal resilience to other types of hazards.
Proceedings in Applied Mathematics Mechanics, 2008
Journal of Volcanology and Geothermal Research, May 1, 2007
The model of gas segregation in volcanic systems developed by Menand and Phillips [Menand, T., Ph... more The model of gas segregation in volcanic systems developed by Menand and Phillips [Menand, T., Phillips, J.C., 2007. Gas segregation in dykes and sills. J. Volcanol. Geotherm. Res. 159, 393-408] show that non-vertical elements of the plumbing systems, such as dykes and sills, act as strong gas segregators and can explain the persistent degassing displayed by many basaltic volcanoes as well as their associated eruptive characteristics. However, this model is based on laboratory experiments carried out at low volumetric gas fractions b 10%. We present additional laboratory experiments which show that the processes governing gas segregation at high volumetric gas fractions are identical to those occurring at low gas fractions, except that higher gas fractions lead to an increase of the viscosity of the bubbly fluid and thus increase the time scales associated with gas segregation. We show that the theory developed by Menand and Phillips [Menand, T., Phillips, J.C., 2007. Gas segregation in dykes and sills. J. Volcanol. Geotherm. Res. 159, 393-408], originally valid at low volumetric gas fractions, can be extended to high gas fractions, at least as high as 40% by volume.
Journal of Volcanology and Geothermal Research, 2016
This study compares and evaluates one-dimensional (1D) and three-28 dimensional (3D) numerical mo... more This study compares and evaluates one-dimensional (1D) and three-28 dimensional (3D) numerical models of volcanic eruption columns in a set of different 29 inter-comparison exercises. The exercises were designed as a blind test in which a set 30 of common input parameters was given for two reference eruptions, representing a 31 strong and a weak eruption column under different meteorological conditions. 32 Comparing the results of the different models allows us to evaluate their capabilities 33 and target areas for future improvement. Despite their different formulations, the 1D 34 and 3D models provide reasonably consistent predictions of some of the key global 35 descriptors of the volcanic plumes. Variability in plume height, estimated from the 36 standard deviation of model predictions, is within ~20% for the weak plume and 37 ~1 0% for the strong plume. Predictions of neutral buoyancy level are also in 38 reasonably good agreement among the different models, with a standard deviation 39 ranging from 9 to 19% (the latter for the weak plume in a windy atmosphere). 40 Overall, these discrepancies are in the range of observational uncertainty of column 41 height. However, there are important differences amongst models in terms of local 42 properties along the plume axis, particularly for the strong plume. Our analysis 43 suggests that the simplified treatment of entrainment in 1D models is adequate to 44 resolve the general behaviour of the weak plume. However, it is inadequate to capture 45 complex features of the strong plume, such as large vortices, partial column collapse, 46 or gravitational fountaining that strongly enhance entrainment in the lower 47 atmosphere. We conclude that there is a need to more accurately quantify entrainment 48 rates, improve the representation of plume radius, and incorporate the effects of 49 column instability in future versions of 1D volcanic plume models.
6Th Internat Conf on Air Distribution in Rooms Roomvent98, 1998
Bull Volcanol, 2002
Nature does not respect the boundaries imposed by the human division of science into traditional ... more Nature does not respect the boundaries imposed by the human division of science into traditional disciplines. It is therefore hardly surprising that major insights in the earth sciences are often achieved by scientists who disregard those same boundaries. The Earth offers a range of awe-inspiring phenomena of beautiful complexity that cannot fail to fascinate those scientists who have retained their youthful open-mindedness and curiosity. Bradford Sturtevant was such a scientist, who brought his expertise as an aeronautical engineer to the study of volcanic eruptions and earthquake dynamics with a characteristic enthusiasm, energy and insight.
Journal of Geophysical Research, 2005
Proceedings. Biological sciences / The Royal Society, Nov 7, 2015
Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidat... more Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have e...
We will discuss the 2D finite-time collapse under gravity of a monodisperse granular column which... more We will discuss the 2D finite-time collapse under gravity of a monodisperse granular column which is one particle deep. Both laboratory experiments and discrete element modelling of such a configuration have been carried out. The final shape of the granular pile -- in particular the final height and the typical runout in the spreading direction - is investigated as a function of the initial aspect ratio a = H/W of the granular column (H being the initial height and W the initial length of the column in the spreading direction). Very good agreement is found between the numerical simulations and experimental data opening up the possibility of examining the dynamics of this fascinating transient flow in detail.
Bulletin of Volcanology, 2015
Mathematical models of natural processes can be used as inversion tools to predict unobserved pro... more Mathematical models of natural processes can be used as inversion tools to predict unobserved properties from measured quantities. Uncertainty in observations and model formulation impact on the efficacy of inverse modelling. We present a general methodology, history matching, that can be used to investigate the effect of observational and model uncertainty on inverse modelling studies. We demonstrate history matching on an integral model of volcanic plumes that is used to estimate source conditions from observations of the rise height of plumes during the eruptions of Eyjafjallajökull, Iceland, in 2010 and Grímsvötn, Iceland, in 2011. Sources of uncertainty are identified and quantified, and propagated through the integral plume model. A preliminary sensitivity analysis is performed to identify the uncertain model parameters that strongly influence model predictions. Model predictions are assessed against observations through an implausibility measure that rules out model inputs that are considered implausible given the quantified uncertainty. We demonstrate that the source mass flux at the volcano can be estimated from plume height observations, but the magmatic temperature, exit velocity and exsolved gas mass fraction cannot be accurately determined. Uncertainty in plume height observations and Editorial responsibility: C. Bonadonna
Bulletin of Volcanology, 2015
Spatial variations in the thickness and grain-size characteristics of tephra fall deposits imply ... more Spatial variations in the thickness and grain-size characteristics of tephra fall deposits imply that tephra depositional processes cannot be fully captured by models of single-particle sedimentation from the base of the eruption plume. Here, we document a secondary thickness maximum in a ∼9.75 ka tephra fall deposit from Chaitén volcano, Chile (Cha1 eruption). This secondary thickness maximum is notably coarser-grained than documented historical examples, being dominated by medium-grained ash, and an origin via particle aggregation is therefore unlikely. In the region of secondary thickening, we propose that high levels of atmospheric turbulence accelerated particles held within the mid-to lower-troposphere (0 to ∼6 km) towards the ground surface. We suggest that this enhancement in vertical atmospheric mixing was driven by the breaking of lee waves, generated by winds passing over elevated topography beneath the eruption plume. Lower atmospheric circulation patterns may exert a significant control on the dispersal and deposition of tephra from eruption plumes across all spatial scales, particularly in areas of complex topography.
In order to develop a detailed understanding of the dynamics of gas puffing (gas release as a ser... more In order to develop a detailed understanding of the dynamics of gas puffing (gas release as a series of distinct pulses) and more sustained degassing (steady plumes of gas) during persistent volcanic degassing, measurements of gas mass flux are required in the vicinity of the volcanic vent. Masaya volcano (Nicaragua), a persistently degassing system, is an ideal location for measuring
<p>Debris flow, locally known as huaycos, impact the east p... more <p>Debris flow, locally known as huaycos, impact the east part of the metropolitan city of Lima, capital of Peru. However, after many extreme events such as the one related to the 2017 “Coastal Niño” or the one in 1987, there is a lack of historical data and sufficiently accurate monitoring systems.</p><p> </p><p>The fact that this area is densely populated presents obvious challenges, from social and physical perspectives, but also some opportunities. We present our experience using open source & low cost rain gauges on previously unmonitored microwatershed, as part of a broader watershed-level monitoring system enhancement by SENAMHI (National Meteorological and Hydrological Service). We also present our experience on linking monitoring systems, debris flow modelling and community based risk management towards developing operational EWS.</p>
Frontiers in Marine Science
Journal of Volcanology and Geothermal Research
Aeroacoustic jet noise theory describes the relationship between acoustic signals and jet operati... more Aeroacoustic jet noise theory describes the relationship between acoustic signals and jet operating parameters. Based on empirical aeroacoustic relationships, a link between peak frequency and amplitude and jet diameter and velocity has been used by volcano acousticians to return the operating parameters of column generating volcanic eruptions. There are however significant differences between the nozzle geometries and structures of flows studied in the aeroacoustic literature and flows emitted from volcanic vents. These differences raise questions as to the validity of applying engineering relationships to volcanic eruptions. Combining particle image velocimetry and acoustic data we investigated the flow structures, acoustic signals and dominant source locations of jet flows emitted from three simple nozzle geometries (convergent, straight and divergent). Flows from the straight and divergent nozzles exited in a more developed flow regime than those emitted from convergent nozzles. While for the convergent nozzles dominant sound sources were located within the jet flow, the dominant signals from the straight and divergent nozzles were located in the region of the nozzle exit. Consequently, for the straight and divergent nozzles it was not possible to differentiate between signals generated by the jet flow and those generated by internal sound sources without beamforming analysis. In order to better replicate the volcanic case and in contrast to studies for industrial applications, our experimental test section was not engineered to minimise internal noise. Without acoustic treatment such as screens, choke plates and paddles, jet noise signals were contaminated by signals generated within the test rig and so, even for the convergent nozzles, the aeroacoustic relationships derived from engineering studies could not be used to retrieve the jet operating parameters. Our results indicate that in the volcanic case, the raw acoustic spectra will contain signals generated by both in-conduit and above-vent processes. Therefore inversions for volcanic jet parameters such as mass eruption rate from standard aeroacoustic relationships may be unreliable.
Scientific reports, Jan 2, 2018
Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, includ... more Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, including international air traffic. For recent major eruptions, information on the volcanic ash plume has been combined with relatively coarse-resolution meteorological model output to provide simulations of regional ash dispersal, with reasonable success on the scale of hundreds of kilometres. However, to predict and mitigate these impacts locally, significant improvements in modelling capability are required. Here, we present results from a dynamic meteorological-ash-dispersion model configured with sufficient resolution to represent local topographic and convectively-forced flows. We focus on an archetypal volcanic setting, Soufrière, St Vincent, and use the exceptional historical records of the 1902 and 1979 eruptions to challenge our simulations. We find that the evolution and characteristics of ash deposition on St Vincent and nearby islands can be accurately simulated when the wind she...
Global Environmental Change
This paper provides an example of how communities can adapt to extreme forms of environmental cha... more This paper provides an example of how communities can adapt to extreme forms of environmental change and uncertainty over the longer term. We analyse the interactions between scientists, communities and risk managers and examine the interpretation and communication of uncertain scientific information during a long-lived volcanic eruption in Tungurahua, Ecuador. This is complemented with a detailed study of the eruptions of 2006 and 2014, which exemplifies the complexity of interactions during periods of heightened volcanic activity. Our study describes how a 'shadow network' has developed outside of, but in interaction with, the formal risk management institutions in Ecuador, improving decision-making in response to heightened volcanic activity. The findings suggest that the interactions have facilitated important adaptations in the scientific advisory response during eruptions (near-real-time interpretation of the volcanic hazards), in hazard communication, and in the evacuation processes. Improved communication between stakeholders and the establishment of thresholds for evacuations have created an effective voluntary evacuation system unique to Tungurahua, allowing people to continue to maintain their livelihoods during heightened volcanic activity and associated periods of uncertainty. Understanding how shadow networks act to minimise the negative consequences of volcanic activity provides valuable insights for increasing societal resilience to other types of hazards.
Proceedings in Applied Mathematics Mechanics, 2008
Journal of Volcanology and Geothermal Research, May 1, 2007
The model of gas segregation in volcanic systems developed by Menand and Phillips [Menand, T., Ph... more The model of gas segregation in volcanic systems developed by Menand and Phillips [Menand, T., Phillips, J.C., 2007. Gas segregation in dykes and sills. J. Volcanol. Geotherm. Res. 159, 393-408] show that non-vertical elements of the plumbing systems, such as dykes and sills, act as strong gas segregators and can explain the persistent degassing displayed by many basaltic volcanoes as well as their associated eruptive characteristics. However, this model is based on laboratory experiments carried out at low volumetric gas fractions b 10%. We present additional laboratory experiments which show that the processes governing gas segregation at high volumetric gas fractions are identical to those occurring at low gas fractions, except that higher gas fractions lead to an increase of the viscosity of the bubbly fluid and thus increase the time scales associated with gas segregation. We show that the theory developed by Menand and Phillips [Menand, T., Phillips, J.C., 2007. Gas segregation in dykes and sills. J. Volcanol. Geotherm. Res. 159, 393-408], originally valid at low volumetric gas fractions, can be extended to high gas fractions, at least as high as 40% by volume.
Journal of Volcanology and Geothermal Research, 2016
This study compares and evaluates one-dimensional (1D) and three-28 dimensional (3D) numerical mo... more This study compares and evaluates one-dimensional (1D) and three-28 dimensional (3D) numerical models of volcanic eruption columns in a set of different 29 inter-comparison exercises. The exercises were designed as a blind test in which a set 30 of common input parameters was given for two reference eruptions, representing a 31 strong and a weak eruption column under different meteorological conditions. 32 Comparing the results of the different models allows us to evaluate their capabilities 33 and target areas for future improvement. Despite their different formulations, the 1D 34 and 3D models provide reasonably consistent predictions of some of the key global 35 descriptors of the volcanic plumes. Variability in plume height, estimated from the 36 standard deviation of model predictions, is within ~20% for the weak plume and 37 ~1 0% for the strong plume. Predictions of neutral buoyancy level are also in 38 reasonably good agreement among the different models, with a standard deviation 39 ranging from 9 to 19% (the latter for the weak plume in a windy atmosphere). 40 Overall, these discrepancies are in the range of observational uncertainty of column 41 height. However, there are important differences amongst models in terms of local 42 properties along the plume axis, particularly for the strong plume. Our analysis 43 suggests that the simplified treatment of entrainment in 1D models is adequate to 44 resolve the general behaviour of the weak plume. However, it is inadequate to capture 45 complex features of the strong plume, such as large vortices, partial column collapse, 46 or gravitational fountaining that strongly enhance entrainment in the lower 47 atmosphere. We conclude that there is a need to more accurately quantify entrainment 48 rates, improve the representation of plume radius, and incorporate the effects of 49 column instability in future versions of 1D volcanic plume models.
6Th Internat Conf on Air Distribution in Rooms Roomvent98, 1998
Bull Volcanol, 2002
Nature does not respect the boundaries imposed by the human division of science into traditional ... more Nature does not respect the boundaries imposed by the human division of science into traditional disciplines. It is therefore hardly surprising that major insights in the earth sciences are often achieved by scientists who disregard those same boundaries. The Earth offers a range of awe-inspiring phenomena of beautiful complexity that cannot fail to fascinate those scientists who have retained their youthful open-mindedness and curiosity. Bradford Sturtevant was such a scientist, who brought his expertise as an aeronautical engineer to the study of volcanic eruptions and earthquake dynamics with a characteristic enthusiasm, energy and insight.
Journal of Geophysical Research, 2005
Proceedings. Biological sciences / The Royal Society, Nov 7, 2015
Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidat... more Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have e...
We will discuss the 2D finite-time collapse under gravity of a monodisperse granular column which... more We will discuss the 2D finite-time collapse under gravity of a monodisperse granular column which is one particle deep. Both laboratory experiments and discrete element modelling of such a configuration have been carried out. The final shape of the granular pile -- in particular the final height and the typical runout in the spreading direction - is investigated as a function of the initial aspect ratio a = H/W of the granular column (H being the initial height and W the initial length of the column in the spreading direction). Very good agreement is found between the numerical simulations and experimental data opening up the possibility of examining the dynamics of this fascinating transient flow in detail.
Bulletin of Volcanology, 2015
Mathematical models of natural processes can be used as inversion tools to predict unobserved pro... more Mathematical models of natural processes can be used as inversion tools to predict unobserved properties from measured quantities. Uncertainty in observations and model formulation impact on the efficacy of inverse modelling. We present a general methodology, history matching, that can be used to investigate the effect of observational and model uncertainty on inverse modelling studies. We demonstrate history matching on an integral model of volcanic plumes that is used to estimate source conditions from observations of the rise height of plumes during the eruptions of Eyjafjallajökull, Iceland, in 2010 and Grímsvötn, Iceland, in 2011. Sources of uncertainty are identified and quantified, and propagated through the integral plume model. A preliminary sensitivity analysis is performed to identify the uncertain model parameters that strongly influence model predictions. Model predictions are assessed against observations through an implausibility measure that rules out model inputs that are considered implausible given the quantified uncertainty. We demonstrate that the source mass flux at the volcano can be estimated from plume height observations, but the magmatic temperature, exit velocity and exsolved gas mass fraction cannot be accurately determined. Uncertainty in plume height observations and Editorial responsibility: C. Bonadonna
Bulletin of Volcanology, 2015
Spatial variations in the thickness and grain-size characteristics of tephra fall deposits imply ... more Spatial variations in the thickness and grain-size characteristics of tephra fall deposits imply that tephra depositional processes cannot be fully captured by models of single-particle sedimentation from the base of the eruption plume. Here, we document a secondary thickness maximum in a ∼9.75 ka tephra fall deposit from Chaitén volcano, Chile (Cha1 eruption). This secondary thickness maximum is notably coarser-grained than documented historical examples, being dominated by medium-grained ash, and an origin via particle aggregation is therefore unlikely. In the region of secondary thickening, we propose that high levels of atmospheric turbulence accelerated particles held within the mid-to lower-troposphere (0 to ∼6 km) towards the ground surface. We suggest that this enhancement in vertical atmospheric mixing was driven by the breaking of lee waves, generated by winds passing over elevated topography beneath the eruption plume. Lower atmospheric circulation patterns may exert a significant control on the dispersal and deposition of tephra from eruption plumes across all spatial scales, particularly in areas of complex topography.
In order to develop a detailed understanding of the dynamics of gas puffing (gas release as a ser... more In order to develop a detailed understanding of the dynamics of gas puffing (gas release as a series of distinct pulses) and more sustained degassing (steady plumes of gas) during persistent volcanic degassing, measurements of gas mass flux are required in the vicinity of the volcanic vent. Masaya volcano (Nicaragua), a persistently degassing system, is an ideal location for measuring