The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
P H Diamond - One of the best experts on this subject based on the ideXlab platform.
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how shear increments affect the flow production branching ratio in csdx
Physics of Plasmas, 2018Co-Authors: P H DiamondAbstract:The coupling of turbulence-driven Azimuthal and axial flows in a linear device absent magnetic shear (Controlled Shear Decorrelation Experiment) is investigated. In particular, we examine the apportionment of Reynolds power between Azimuthal and axial flows, and how the Azimuthal flow shear affects axial flow generation and saturation by drift wave turbulence. We study the response of the energy branching ratio, i.e., ratio of axial and Azimuthal Reynolds powers, PzR/PyR, to incremental changes of Azimuthal and axial flow shears. We show that increasing Azimuthal flow shear decreases the energy branching ratio. When axial flow shear increases, this ratio first increases but then decreases to zero. The axial flow shear saturates below the threshold for parallel shear flow instability. The effects of Azimuthal flow shear on the generation and saturation of intrinsic axial flows are analyzed. Azimuthal flow shear slows down the modulational growth of the seed axial flow shear, and thus reduces intrinsic axial flow production. Azimuthal flow shear reduces both the residual Reynolds stress (of axial flow, i.e., ΠxzRes) and turbulent viscosity ( χzDW) by the same factor |⟨vy⟩′|−2Δx−2Ln−2ρs2cs2, where Δx is the distance relative to the reference point where ⟨vy⟩=0 in the plasma frame. Therefore, the stationary state axial flow shear is not affected by Azimuthal flow shear to leading order since ⟨vz⟩′∼ΠxzRes/χzDW.The coupling of turbulence-driven Azimuthal and axial flows in a linear device absent magnetic shear (Controlled Shear Decorrelation Experiment) is investigated. In particular, we examine the apportionment of Reynolds power between Azimuthal and axial flows, and how the Azimuthal flow shear affects axial flow generation and saturation by drift wave turbulence. We study the response of the energy branching ratio, i.e., ratio of axial and Azimuthal Reynolds powers, PzR/PyR, to incremental changes of Azimuthal and axial flow shears. We show that increasing Azimuthal flow shear decreases the energy branching ratio. When axial flow shear increases, this ratio first increases but then decreases to zero. The axial flow shear saturates below the threshold for parallel shear flow instability. The effects of Azimuthal flow shear on the generation and saturation of intrinsic axial flows are analyzed. Azimuthal flow shear slows down the modulational growth of the seed axial flow shear, and thus reduces intrinsic axi...
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how shear increments affect the flow production branching ratio in csdx
Physics of Plasmas, 2018Co-Authors: P H DiamondAbstract:The coupling of turbulence-driven Azimuthal and axial flows in a linear device absent magnetic shear (Controlled Shear Decorrelation Experiment) is investigated. In particular, we examine the apportionment of Reynolds power between Azimuthal and axial flows, and how the Azimuthal flow shear affects axial flow generation and saturation by drift wave turbulence. We study the response of the energy branching ratio, i.e., ratio of axial and Azimuthal Reynolds powers, PzR/PyR, to incremental changes of Azimuthal and axial flow shears. We show that increasing Azimuthal flow shear decreases the energy branching ratio. When axial flow shear increases, this ratio first increases but then decreases to zero. The axial flow shear saturates below the threshold for parallel shear flow instability. The effects of Azimuthal flow shear on the generation and saturation of intrinsic axial flows are analyzed. Azimuthal flow shear slows down the modulational growth of the seed axial flow shear, and thus reduces intrinsic axial flow production. Azimuthal flow shear reduces both the residual Reynolds stress (of axial flow, i.e., ΠxzRes) and turbulent viscosity ( χzDW) by the same factor |⟨vy⟩′|−2Δx−2Ln−2ρs2cs2, where Δx is the distance relative to the reference point where ⟨vy⟩=0 in the plasma frame. Therefore, the stationary state axial flow shear is not affected by Azimuthal flow shear to leading order since ⟨vz⟩′∼ΠxzRes/χzDW.
Yoshinori Shinohara - One of the best experts on this subject based on the ideXlab platform.
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Optimal sap flux sensor allocation for stand transpiration estimates: a non-dimensional analysis
Annals of Forest Science, 2017Co-Authors: Hikaru Komatsu, Tomonori Kume, Yoshinori ShinoharaAbstract:AbstractKey messageMeasuring between-tree variations in sap flux density rather than Azimuthal variations should be prioritized for reliable stand transpiration estimates based on sap flux methods.ContextStand transpiration (E) estimated using sap flux methods includes uncertainty induced by Azimuthal variations and between-tree variations in sap flux density (F).AimsThis study examines whether or not measuring F for two or more Azimuthal directions to cover Azimuthal variations in F leads to more reliable E estimates. This examination was done under the assumption that Azimuthal and between-tree variations in F are not systematic and when a limited number of sensors are available.MethodsWe first non-dimensionalized the theoretical framework established by a previous study and developed a general hypothesis. We then validated the hypothesis quantitatively by numerical experiments.ResultsThe non-dimensionalized theory allowed us to hypothesize that measuring F for one Azimuthal direction would reduce uncertainty in E estimates more effectively than measuring F for two or more Azimuthal directions. Results of the numerical experiments were found to support this hypothesis.ConclusionWhen the aforementioned assumptions are satisfied, allocating sensors to measure F for one Azimuthal direction to cover between-tree variations in F always leads to more reliable E estimates.
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Azimuthal and radial variations in sap flux density and effects on stand scale transpiration estimates in a japanese cedar forest
Tree Physiology, 2013Co-Authors: Yoshinori Shinohara, Hikaru Komatsu, Kenji Tsuruta, Kyoichi Otsuki, Akira Ogura, Fumikazu Noto, Toshisuke MaruyamaAbstract:Understanding radial and Azimuthal variation, and tree-to-tree variation, in sap flux density ( Fd) as sources of uncertainty is important for estimating transpiration using sap flow techniques. In a Japanese cedar ( Cryptomeria japonica D. Don.) forest, Fd was measured at several depths and aspects for 18 trees, using heat dissipation (Granier-type) sensors. We observed considerable Azimuthal variation in Fd. The coefficient of variation (CV) calculated from Fd at a depth of 0–20 m m (Fd1) and Fd at a depth of 20–40 m m (Fd2) ranged from 6.7 to 37.6% (mean = 2 8.3%) and from 19.6 to 62.5% (mean = 3 4.6%) for the Azimuthal directions. Fd at the north aspect averaged for nine trees, for which Azimuthal measurements were made, was obviously smaller than Fd at the other three aspects (i.e., west, south and east) averaged for the nine trees. Fd1 averaged for the nine trees was significantly larger than Fd2 averaged for the nine trees. The error for stand-scale transpiration (E) estimates caused by ignoring the Azimuthal variation was larger than that caused by ignoring the radial variation. The error caused by ignoring tree-to-tree variation was larger than that caused by ignoring both radial and Azimuthal variations. Thus, tree-to-tree variation in Fd would be more important than both radial and Azimuthal variations in Fd for E estimation. However, Fd for each tree should not be measured at a consistent aspect but should be measured at various aspects to make accurate E estimates and to avoid a risk of error caused by the relationship of Fd to aspect.
Hikaru Komatsu - One of the best experts on this subject based on the ideXlab platform.
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Optimal sap flux sensor allocation for stand transpiration estimates: a non-dimensional analysis
Annals of Forest Science, 2017Co-Authors: Hikaru Komatsu, Tomonori Kume, Yoshinori ShinoharaAbstract:AbstractKey messageMeasuring between-tree variations in sap flux density rather than Azimuthal variations should be prioritized for reliable stand transpiration estimates based on sap flux methods.ContextStand transpiration (E) estimated using sap flux methods includes uncertainty induced by Azimuthal variations and between-tree variations in sap flux density (F).AimsThis study examines whether or not measuring F for two or more Azimuthal directions to cover Azimuthal variations in F leads to more reliable E estimates. This examination was done under the assumption that Azimuthal and between-tree variations in F are not systematic and when a limited number of sensors are available.MethodsWe first non-dimensionalized the theoretical framework established by a previous study and developed a general hypothesis. We then validated the hypothesis quantitatively by numerical experiments.ResultsThe non-dimensionalized theory allowed us to hypothesize that measuring F for one Azimuthal direction would reduce uncertainty in E estimates more effectively than measuring F for two or more Azimuthal directions. Results of the numerical experiments were found to support this hypothesis.ConclusionWhen the aforementioned assumptions are satisfied, allocating sensors to measure F for one Azimuthal direction to cover between-tree variations in F always leads to more reliable E estimates.
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Azimuthal and radial variations in sap flux density and effects on stand scale transpiration estimates in a japanese cedar forest
Tree Physiology, 2013Co-Authors: Yoshinori Shinohara, Hikaru Komatsu, Kenji Tsuruta, Kyoichi Otsuki, Akira Ogura, Fumikazu Noto, Toshisuke MaruyamaAbstract:Understanding radial and Azimuthal variation, and tree-to-tree variation, in sap flux density ( Fd) as sources of uncertainty is important for estimating transpiration using sap flow techniques. In a Japanese cedar ( Cryptomeria japonica D. Don.) forest, Fd was measured at several depths and aspects for 18 trees, using heat dissipation (Granier-type) sensors. We observed considerable Azimuthal variation in Fd. The coefficient of variation (CV) calculated from Fd at a depth of 0–20 m m (Fd1) and Fd at a depth of 20–40 m m (Fd2) ranged from 6.7 to 37.6% (mean = 2 8.3%) and from 19.6 to 62.5% (mean = 3 4.6%) for the Azimuthal directions. Fd at the north aspect averaged for nine trees, for which Azimuthal measurements were made, was obviously smaller than Fd at the other three aspects (i.e., west, south and east) averaged for the nine trees. Fd1 averaged for the nine trees was significantly larger than Fd2 averaged for the nine trees. The error for stand-scale transpiration (E) estimates caused by ignoring the Azimuthal variation was larger than that caused by ignoring the radial variation. The error caused by ignoring tree-to-tree variation was larger than that caused by ignoring both radial and Azimuthal variations. Thus, tree-to-tree variation in Fd would be more important than both radial and Azimuthal variations in Fd for E estimation. However, Fd for each tree should not be measured at a consistent aspect but should be measured at various aspects to make accurate E estimates and to avoid a risk of error caused by the relationship of Fd to aspect.
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Azimuthal variations of sap flux density within japanese cypress xylem trunks and their effects on tree transpiration estimates
Journal of Forest Research, 2010Co-Authors: Kenji Tsuruta, Hikaru Komatsu, Tomonori Kume, Naoko Higashi, Toshihiro Umebayashi, Tomoomi Kumagai, Kyoichi OtsukiAbstract:AbstractSap flow techniques are practical tools for estimating tree transpiration. Though many previous studies using sap flow techniques did not consider Azimuthal variations of sap flux density (Fd) on xylem trunk to estimate tree transpiration, a few studies reported that ignoring the Azimuthal variations in Fd could cause large errors in tree transpiration estimates for some tree species. Therefore, examining Azimuthal variations in Fd for major plantation tree species is critical for estimating tree transpiration. Using the thermal dissipation method, we examined Azimuthal variations in Fd in six trees of Japanese cypress Chamaecyparis obtusa (Sieb. et Zucc.) Endl., which is one of the most common plantation tree species in Japan. We recorded considerable variations among Fd at four different Azimuthal directions. The Fd value for one aspect was more than 100% larger than those for the other aspects. We calculated differences between tree transpiration estimates based on Fd for one to three Azimuthal...
Ryuji Morishima - One of the best experts on this subject based on the ideXlab platform.
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Azimuthal temperature modulations of saturn s a ring caused by self gravity wakes
Icarus, 2014Co-Authors: Ryuji Morishima, Linda Spilker, Neal J TurnerAbstract:Abstract The physical temperatures of the Saturn’s A ring measured by the Cassini Composite Infrared Spectrometer (CIRS) show quadrupole Azimuthal modulations besides temperature drops in Saturn’s shadow. These Azimuthal modulations are likely to be caused by self-gravity wakes. In this paper, we develop a new thermal model in which wakes are modeled as elliptical cylinders ignoring inter-wake particles. All the heat fluxes are calculated explicitly taking into account inter-wake shadowing and heating. We apply our model to Azimuthal scans of the A ring obtained by CIRS. It is found that the Azimuthal modulation of the ring temperature is primarily caused by the Azimuthal variation of the geometric filling factor of the ring seen from the Sun. The thermal inertia estimated from the eclipse data (data only inside and near Saturn’s shadow) of the low phase scans is ∼10 J m −2 K −1 s −1/2 . With this value of the thermal inertia, the amplitude of the Azimuthal temperature modulation is overestimated in our model as compared with those observed. This is likely to be because our model ignores inter-wake particles. The bolometric reflectance of wakes is estimated to be 0.35–0.40 although lower values are required to reproduce temperatures at low solar phase angles. This apparent phase dependence of the reflectance indicates that roughness on the wake surfaces is necessary.
Neal J Turner - One of the best experts on this subject based on the ideXlab platform.
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Azimuthal temperature modulations of saturn s a ring caused by self gravity wakes
Icarus, 2014Co-Authors: Ryuji Morishima, Linda Spilker, Neal J TurnerAbstract:Abstract The physical temperatures of the Saturn’s A ring measured by the Cassini Composite Infrared Spectrometer (CIRS) show quadrupole Azimuthal modulations besides temperature drops in Saturn’s shadow. These Azimuthal modulations are likely to be caused by self-gravity wakes. In this paper, we develop a new thermal model in which wakes are modeled as elliptical cylinders ignoring inter-wake particles. All the heat fluxes are calculated explicitly taking into account inter-wake shadowing and heating. We apply our model to Azimuthal scans of the A ring obtained by CIRS. It is found that the Azimuthal modulation of the ring temperature is primarily caused by the Azimuthal variation of the geometric filling factor of the ring seen from the Sun. The thermal inertia estimated from the eclipse data (data only inside and near Saturn’s shadow) of the low phase scans is ∼10 J m −2 K −1 s −1/2 . With this value of the thermal inertia, the amplitude of the Azimuthal temperature modulation is overestimated in our model as compared with those observed. This is likely to be because our model ignores inter-wake particles. The bolometric reflectance of wakes is estimated to be 0.35–0.40 although lower values are required to reproduce temperatures at low solar phase angles. This apparent phase dependence of the reflectance indicates that roughness on the wake surfaces is necessary.
