Search results for "Buoyancy"
showing 5 items of 35 documents
Technical Note: Sensitivity of 1-D smoke plume rise models to the inclusion of environmental wind drag
2010
Abstract. Vegetation fires emit hot gases and particles which are rapidly transported upward by the positive buoyancy generated by the combustion process. In general, the final vertical height that the smoke plumes reach is controlled by the thermodynamic stability of the atmospheric environment and the surface heat flux released by the fire. However, the presence of a strong horizontal wind can enhance the lateral entrainment and induce additional drag, particularly for small fires, impacting the smoke injection height. In this paper, we revisit the parameterization of the vertical transport of hot gases and particles emitted from vegetation fires, described in Freitas et al. (2007), to in…
Stability of Flow with Viscous Dissipation in a Horizontal Porous Layer with an Open Boundary Having a Prescribed Temperature Gradient
2010
Published version of an article in the journal: Transport in Porous Media. The original publication is available at www.springerlink.com, http://dx.doi.org/10.1007/s11242-010-9588-6 A buoyancy-induced stationary flow with viscous dissipation in a horizontal porous layer is investigated. The lower boundary surface is impermeable and subject to a uniform heat flux. The upper open boundary has a prescribed, linearly varying, temperature distribution. The buoyancy-induced basic velocity profile is parallel and non-uniform. The linear stability of this basic solution is analysed numerically by solving the disturbance equations for oblique rolls arbitrarily oriented with respect to the basic velo…
School-related stress among sixth-grade students : Associations with academic buoyancy and temperament
2019
The present study examined to what extent sixth-grade students' academic buoyancy and temperament contributed to their school-related stress. A total of 845 students rated their school-related stress at the beginning and end of the school year and their academic buoyancy at the beginning of the year. Parents rated students' effortful control and negative affectivity. The results showed that high academic buoyancy, high effortful control, and low negative affectivity at the beginning of the school year were related to lower school-related stress at the end of the school year, after controlling for gender, GPA, and previous level of stress. Effortful control and negative affectivity had no si…
On the Rifting Dynamics of Plate Divergence and Magma Accumulation at Oceanic Ridge Axes
1995
Rifting dynamics at spreading axes is governed by two processes: the large-scale plate divergence and the local magma accumulation in the crust-mantle transition layer. Both evolve simultaneously. A model is developed particularly for the situation in Iceland where a well studied rifting episode occurred in the Krafla volcanic system 1975–1984. Both the divergence and the buoyant rise of magma create tensile deviatoric stress in the axial region, but while divergence generates an altogether extensional stress field, uprising of buoyant melt produces tension only near the axis but compression of the sides. The buoyant rise is driven by the differential pressure gradient in rock and melt. The…
Temperature effects explain continental scale distribution of cyanobacterial toxins
2018
Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect…