Модель осредненной молекулярной вязкости для турбулентных течений неньютоновских жидкостей

A novel turbulence model for flows of viscoplastic fluid is presented. It is based on the Reynolds-Averaged approach. A closed model for the averaged viscosity that takes into account its nonlinear dependence on the fluctuating rate of deformation tensor is proposed. Test calculations were performed for power-law fluid and Herschel–Bulkley fluid flows in a straight round pipe. Numerical data obtained with the use of the proposed model are compared with the results of direct numerical simulations. The proposed model adequately describes the reduction in the turbulent transport of momentum with decreasing power-law index and with increasing yield stress of the fluidВ статье представлена модель турбулентности для вязкопластических жидкостей. С использованием процедуры осреднения по Рейнольдсу разработана модель осредненной молекулярной вязкости для неньютоновских сред, учитывающая нелинейную зависимость от флуктуирующего тензора скоростей деформации. В качестве базовой модели турбулентности использована двух- параметрическая дифференциальная модель турбулентности. Тестовые расчеты выполнены для течений степенной жидкости и жидкости Гершеля–Балкли в прямой круглой трубе. Получен- ные расчетные данные сопоставлялись с результатами прямого численного моделирования. Предложенная модель позволяет правильно описать снижение турбулентного переноса импульса с уменьшением степени среды и с увеличением предельного напряжени

Cross-Correlation Earthquake Precursors in the Hydrogeochemical and Geoacoustic Signals for the Kamchatka Peninsula

We propose a new type of earthquake precursor based on the analysis of correlation dynamics between geophysical signals of different nature. The precursor is found using a two-parameter cross-correlation function introduced within the framework of flicker-noise spectroscopy, a general statistical physics approach to the analysis of time series. We consider an example of cross-correlation analysis for water salinity time series, an integral characteristic of the chemical composition of groundwater, and geoacoustic emissions recorded at the G-1 borehole on the Kamchatka peninsula in the time frame from 2001 to 2003, which is characterized by a sequence of three groups of significant seismic events. We found that cross-correlation precursors took place 27, 31, and 35 days ahead of the strongest earthquakes for each group of seismic events, respectively. At the same time, precursory anomalies in the signals themselves were observed only in the geoacoustic emissions for one group of earthquakes.Comment: 21 pages, 5 figures, 1 table; to be published in "Acta Geophysica". arXiv admin note: substantial text overlap with arXiv:1101.147

Модель осредненной молекулярной вязкости для турбулентных течений неньютоновских жидкостей

A novel turbulence model for flows of viscoplastic fluid is presented. It is based on the Reynolds-Averaged approach. A closed model for the averaged viscosity that takes into account its nonlinear dependence on the fluctuating rate of deformation tensor is proposed. Test calculations were performed for power-law fluid and Herschel–Bulkley fluid flows in a straight round pipe. Numerical data obtained with the use of the proposed model are compared with the results of direct numerical simulations. The proposed model adequately describes the reduction in the turbulent transport of momentum with decreasing power-law index and with increasing yield stress of the fluidВ статье представлена модель турбулентности для вязкопластических жидкостей. С использованием процедуры осреднения по Рейнольдсу разработана модель осредненной молекулярной вязкости для неньютоновских сред, учитывающая нелинейную зависимость от флуктуирующего тензора скоростей деформации. В качестве базовой модели турбулентности использована двух- параметрическая дифференциальная модель турбулентности. Тестовые расчеты выполнены для течений степенной жидкости и жидкости Гершеля–Балкли в прямой круглой трубе. Получен- ные расчетные данные сопоставлялись с результатами прямого численного моделирования. Предложенная модель позволяет правильно описать снижение турбулентного переноса импульса с уменьшением степени среды и с увеличением предельного напряжени

Measurement of spin correlation between top and antitop quarks produced in ppˉp\bar{p} collisions at s=1.96\sqrt{s} = 1.96 TeV

We present a measurement of the correlation between the spins of t and tbar quarks produced in proton-antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb$^{-1}$. The measured value of the correlation coefficient in the off-diagonal basis, $O_{off} = 0.89 \pm 0.22$ (stat + syst), is in agreement with the standard model prediction, and represents evidence for a top-antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.We present a measurement of the correlation between the spins of t and t¯ quarks produced in proton–antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb−1 . The measured value of the correlation coefficient in the off-diagonal basis, Ooff=0.89±0.22(stat+syst) , is in agreement with the standard model prediction, and represents evidence for a top–antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.We present a measurement of the correlation between the spins of t and tbar quarks produced in proton-antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb$^{-1}$. The measured value of the correlation coefficient in the off-diagonal basis, $O_{off} = 0.89 \pm 0.22$ (stat + syst), is in agreement with the standard model prediction, and represents evidence for a top-antitop quark spin correlation difference from zero at a level of 4.2 standard deviations