Труды сотрудников ИВМ СО РАН

/ C. J. Farrugia [et al.] // Sol. Phys. - 2012. - Vol. 281, Is. 1. - pp. 461-489, DOI 10.1007/s11207-012-0119-1. - Cited References: 53 . - 29. - ISSN 0038-0938РУБ Astronomy & Astrophysics

Аннотация: We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007-2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfv,n Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from Wind and ground-based observations: i) the dayside contribution to the cross-polar cap potential (CPCP), and ii) the shapes of the magnetopause and bow shock. For i) we find a low interplanetary electric field of 1.3 +/- 0.9 mV m(-1) and a CPCP of 37.3 +/- 20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfven wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For ii) we determine 328 magnetopause and 271 bow shock crossings made by Geotail, Cluster 1, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey. We use the same numerical approach as in Fairfield's (J. Geophys. Res. 76, 7600, 1971) empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 R-E and 14.35 R-E, respectively. When comparing with Fairfield's (1971) classic result, we find that the subsolar magnetosheath is thinner by similar to 1 R-E. This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause. The magnetopause is more flared than in Fairfield's model. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces.

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Доп.точки доступа:
Farrugia, C.J.; Harris, B.; Leitner, M.; Mostl, C.; Galvin, A.B.; Simunac, K.D.C.; Torbert, R.B.; Temmer, M.B.; Veronig, A.M.; Erkaev, N.V.; Еркаев, Николай Васильевич; Szabo, A.; Ogilvie, K.W.; Luhmann, J.G.; Osherovich, V.A.

[Text] / I. I. Ryzhkov, A. V. Minakov // Int. J. Heat Mass Transf. - 2014. - Vol. 77. - P956-969, DOI 10.1016/j.ijheatmasstransfer.2014.05.045. - Cited References: 44. - This work is supported the Krasnoyarsk Regional Foundation of Scientific and Technical Activity (Grant No. 02/13) and the Russian President Grant No. MK-6296.2013.8. . - ISSN 0017-9310. - ISSN 1879-2189РУБ Thermodynamics + Engineering, Mechanical + Mechanics

Аннотация: Laminar convective heat transfer of water-alumina nanofluid in a circular tube with uniform heat flux is investigated numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. A new expression for thermophoretic mobility is suggested on the basis of existing experimental results and theoretical concepts. It is shown that thermophoresis leads to a significant reduction of nanoparticle volume fraction in the boundary layer near the wall. The corresponding viscosity reduction causes the velocity increase near the wall and flattening of velocity profile near the tube axis to keep the mass flow rate constant. The decrease of wall shear stress leads to the decrease of the required pressure drop. The calculations for two-component model provide higher values of the local and average heat transfer coefficients in comparison with the one-component model. The difference does not exceed 10% and decreases with increasing the thermal Peclet number. The calculations for one-component model show the independence of local and average Nusselt numbers on the nanoparticle volume fraction. The results for two-component model predict the increase of Nusselt number when the thermophoretic effect becomes stronger. The effectiveness of water-alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. It is shown that the nanofluid shows better performance than the base fluid in the range of low pumping power and, correspondingly, low inlet velocity. (C) 2014 Elsevier Ltd. All rights reserved.

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Держатели документа:
[Ryzhkov, Ilya I.] SB RAS, Inst Computat Modelling, Krasnoyarsk 660036, Russia
[Minakov, Andrey V.] Siberian Fed Univ, Inst Engn Phys & Radio Elect, Krasnoyarsk 660041, Russia
ИВМ СО РАН

Доп.точки доступа:
Ryzhkov, I.I.; Рыжков, Илья Игоревич; Minakov, A.V.; Минаков, Андрей Викторович; Krasnoyarsk Regional Foundation of Scientific and Technical Activity [02/13]; Russian President Grant [MK-6296.2013.8]

[Text] / S. V. Kozlova, I. I. Ryzhkov // Eur. Phys. J. E. - 2014. - Vol. 37, Is. 9. - Ст. 87, DOI 10.1140/epje/i2014-14087-0. - Cited References: 44. - The authors are grateful to Dr. A. V. Minakov for assistance in ANSYS Fluent numerical calculations. This work is supported the Krasnoyarsk Regional Foundation of Scientific and Technical Activity (Grant 02/13). . - ISSN 1292-8941. - ISSN 1292-895XРУБ Chemistry, Physical + Materials Science, Multidisciplinary + Physics, Applied + Polymer Science

Аннотация: In this paper, laminar convective heat transfer of water-alumina nanofluid in a circular tube with uniform heat flux at the tube wall is investigated. The investigation is performed numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. Two thermal regimes at the tube wall, heating and cooling, are considered and the influence of nanoparticle migration on the heat transfer is analyzed comparatively. The intensity of thermophoresis is characterized by a new empirical model for thermophoretic mobility. It is shown that the nanoparticle volume fraction decreases (increases) in the boundary layer near the wall under heating (cooling) due to thermophoresis. The corresponding variations of nanofluid properties and flow characteristics are presented and discussed. The intensity of heat transfer for the model with thermophoresis in comparison to the model without thermophoresis is studied by plotting the dependence of the heat transfer coefficient on the Peclet number. The effectiveness of water-alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. The analysis of the results reveals that the water-alumina nanofluid shows better performance in the heating regime than in the cooling regime due to thermophoretic effect.

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Держатели документа:
[Kozlova, Sofya V.
Ryzhkov, Ilya I.] Inst Computat Modelling SB RAS, Krasnoyarsk 660036, Russia
ИВМ СО РАН

Доп.точки доступа:
Kozlova, S.V.; Ryzhkov, I.I.; Рыжков, Илья Игоревич; Krasnoyarsk Regional Foundation of Scientific and Technical Activity [02/13]