1,721,111 research outputs found
Debris and hyper-concentrated flows: overview and perspective
Full text linkDebris and hyper-concentrated flows are among the most destructive of all water – related disasters. They mainly affect mountain areas in a wide range of morpho-climatic environments and in recent years have attracted more and more attention from the scientific and professional communities and concern from public awareness, due to the increasing frequency with which they occur and the death toll they claim. In this context, achieving a system of debris and hyper-concentrated flow constitutive equations is a task which has been given particular attention by scientists during the second half of the last Century.
In relation to these issues, the paper reviews the most updated and effective procedures , nowadays available, suitable to predict the triggering and mobilising processes of these phenomena and proposes a new set of mathematical models able to assess the depth of the wave and the velocities of the liquid and solid phases of both non-stratified (mature) and stratified (immature) flows following flash-floods and dam-break events , in one and two dimensional schemes. Different experimental cases of dam-break situations in a square section channel were considered for the purpose of comparing results.
These tools will allow, on one hand, to better focus what to observe in the field and, on the other hand, improve both mitigation measures and hazard mapping procedures
Performance assessment of sprinkler irrigation systems : a new indicator for spray evaporation losses
No full textPerformance assessment is an increasingly relevant concept in present-day irrigation systems. To this end some indicators have been proposed for comparing actual performance with established design criteria. Concerning sprinkler irrigation, evaluation of the jet losses due to environmental conditions can be considered an important indicator of system performance. The issue requires a full analytical description of spray flow and waste and entails both experimental and theoretical studies. In the former, it appears to be difficult to identify, and so to measure, the contribution of each parameter to the final result; in the latter, the non-linear relationships among the variables make it difficult to obtain an exhaustive analytical picture of the process. Numerous experimental and theoretical studies have been conducted recently in an attempt to gain a deeper insight into the phenomenon but much work still remains to be done. A mathematical model for irrigation sprinkler droplet ballistics, based on a simplified dynamic approach to the phenomenon, has been presented. The results compare very favourably with the kinematic results obtained by other authors using more complicated procedures. Moreover, field trials showed the model to reliably estimate spray evaporation losses caused by environmental conditions. Further analytic and experimental work is needed to gain a better understanding of the problem. Copyrigh
Sprinkler irrigation systems: state-of-the-art of kinematic analysis and quantum mechanics applied to water jets
No full textThe description of liquid jets crossing a gas is common to many scientific issues, and in particular sprinkler irrigation in the
agricultural sector is definitely one of the most challenging issues of recent years. In the thematic literature, the classic approach
has recently been challenged by the quantum one, generally more suitable to describe interactions among several objects. By
using a deeper approach, microscopic insight into the actual mechanics of single water droplets in sprinkler irrigation jets may
be carefully described and this represents the first move to find solutions for irrigation problems
- …
