Experimental study of granular surface flows via a fast camera: a continuous description

Depth averaged conservation equations are written for granular surface flows. Their application to the study of steady surface flows in a rotating drum allows to find experimentally the constitutive relations needed to close these equations from measurements of the velocity profile in the flowing layer at the center of the drum and from the flowing layer thickness and the static/flowing boundary profiles. The velocity varies linearly with depth, with a gradient independent of both the flowing layer thickness and the static/flowing boundary local slope. The first two closure relations relating the flow rate and the momentum flux to the flowing layer thickness and the slope are then deduced. Measurements of the profile of the flowing layer thickness and the static/flowing boundary in the whole drum explicitly give the last relation concerning the force acting on the flowing layer. Finally, these closure relations are compared to existing continuous models of surface flows.Comment: 20 pages, 11 figures, submitted to Phys. FLuid

Breeding Forages to Cope with Environmental Challenges in the Light of Climate Change and Resource Limitations.

Projected climate change and increased pressure for adopting more sustainable agricultural practices calls for new approaches in breeding forage crops for the future. In the cool temperate regions of Europe they may benefit from a warmer and prolonged growing season, even though new stresses may emerge during autumn and winter, whereas further south risk of drought will increase. In addition, forage crops have to be able to use both nutrients and water more efficiently in the future in order to maximize production per unit area. Examples are given how perennial forage crops can be adapted to the projected envi-ronmental conditions in Europe through breeding. In the Nordic region the focus is on identifying traits that are important for high yields under changed overwin-tering conditions, as well as management practices. In maritime, oceanic Europe the focus is on forage grass and legume root systems for ecosystem service, nutri-ent and water use, and the advantages and potential for Festulolium, including its role in ruminant nutrition. In temperate and southern Europe, the aim is to develop varieties able to survive long drought periods and to recover rapidly following autumn rains, as well as improving adapted legume species to reduce the use of synthetic fertilizers, the environmental impacts of ruminant production systems and their dependency on external protein-rich feeds. Forage production systems, commonly found in areas less suited to grain production, can contribute significantly to future food security if the adaptation of forage crops to the future environmental challenges is successful