Contribution to runoff erosion of earthen channels

The purpose of the experimental study is to investigate the effect of earthen channel geometry on erosion by runoff. After the construction of an experimental setup, four geometric shapes were tested; the circle, the triangle, the sinus and the trapeze. These four forms were dug in agricultural sandy-loam soil. For all experiments, and for each geometric shape, discharge, slope inclination, time, and slope length were varied. Experimental results have shown that the geometry of earthen channels plays an important role in sedimentary dynamics. In addition, it was noted that for slopes less than 20%, the sinusoidal geometric shape allowed to have the minimum of sediment exported. For upper slopes, the minimum amount of soil exported, was obtained with the triangle. The analysis of the experimental results allowed us to see that the variation of the mass of soil exported as a function of the discharge, the slope inclination, the time and the slope length, followed power functions with respective exponents of 2.49, 0.88, -1.27, and -1.53

Forced Heat Transfer Convection in a Porous Channel with an Oriented Confined Jet

The present study is an analysis of the forced convection heat transfer in porous channel with an oriented jet at the inlet with uniform velocity and temperature distributions. The upper wall is insulated when the bottom one is kept at constant temperature higher than that of the fluid at the entrance. The dynamic field is analysed by the Brinkman-Forchheimer extended Darcy model and the thermal field is traduced by the energy one equation model. The numerical solution of the governing equations is obtained by using the finite volume method. The results mainly concern the effect of Reynolds number, jet angle and thermal conductivity ratio on the flow structure and local and average Nusselt numbers evolutions

New approach to estimate the shear stress and the force of raindrops and their effect on erodibility of agricultural soils

The objective of this work was to the study the erosive force of raindrops and the shear stress on the soil erodibility of disturbed and saturated agricultural soil. A mathematical development was used to determine a new approach to the shear stress. The soil erodibility is calculated using the WEPP (water erosion prediction project) model. To realize this work, an experimental study was led in a laboratory using the rainfall simulator. The soil tray used in this study has a length of 2 m, width of 50 cm and a depth of 15 cm and the slope was adjusted with a system. The soils used were sandy and silty agricultural soils. The results show that the relationship between the erosive force of raindrops and the shear stress on the soil erodibility increased respectively as a power and linear function with an important coeffiient of determination. As regards the relationships between soil erodibility and the mean raindrop diameter, the evolution is represented by a power function with high coeffiient of determination

Forced Heat Transfer Convection in a Porous Channel with an Oriented Confined Jet

The present study is an analysis of the forced convection heat transfer in porous channel with an oriented jet at the inlet with uniform velocity and temperature distributions. The upper wall is insulated when the bottom one is kept at constant temperature higher than that of the fluid at the entrance. The dynamic field is analysed by the Brinkman-Forchheimer extended Darcy model and the thermal field is traduced by the energy one equation model. The numerical solution of the governing equations is obtained by using the finite volume method. The results mainly concern the effect of Reynolds number, jet angle and thermal conductivity ratio on the flow structure and local and average Nusselt numbers evolutions

Forced Heat Transfer Convection in a Porous Channel with an Oriented Confined Jet

The present study is an analysis of the forced convection heat transfer in porous channel with an oriented jet at the inlet with uniform velocity and temperature distributions. The upper wall is insulated when the bottom one is kept at constant temperature higher than that of the fluid at the entrance. The dynamic field is analysed by the Brinkman-Forchheimer extended Darcy model and the thermal field is traduced by the energy one equation model. The numerical solution of the governing equations is obtained by using the finite volume method. The results mainly concern the effect of Reynolds number, jet angle and thermal conductivity ratio on the flow structure and local and average Nusselt numbers evolutions

Comparison between Two Local Thermal Non Equilibrium Criteria in Forced Convection through a Porous Channel

Two criteria are used and compared to investigate the local thermal equilibrium assumption in a forced convection through a porous channel. The first criterion is based on the maximum local temperature difference between the solid and fluid phases, while the second is based on the average of the local differences between the temperature of the solid phase and the fluid phase. For this purpose, the momentum and energy equations based on the Darcy-Brinkman-Forchheimer and the local thermal non equilibrium models are solved numerically using the finite volume method. The analysis focused on searching thermophysical parameters ranges which validate local thermal equilibrium hypothesis. Thus, by using the two criteria, the obtained results mainly revealed that this local thermal equilibrium assumption is verified for low thermal conductivity ratio and Reynolds number values and for high interstitial Biot number and porosity, while it is unfavorably affected by the high values of Prandtl number. However, it is also found that the parameters ranges corresponding to the local equilibrium validity depends on the selected local thermal non equilibrium criterion

Effects of interstitial exchange parameters on the thermal field in a porous channel with heat generation and local thermal non equilibrium

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.The main objective of this work is to examine the effect of both the solid heat generation ratio, the Biot number and the thermal conductivities ratio on the temperature distributions of both fluid and solid phases and also on the local thermal non equilibrium condition as function of the transverse position and for different section of a porous channel by moving from the inlet to the outlet. The dynamic field in the channel is calculated using the Darcy-Brinkman model and the thermal field is described by the two temperature equations model, which takes into account the local thermal non equilibrium between the two phases by including the interstitial heat transfer between the fluid and solid phases. The results which emerged from this study mainly revealed that the temperature difference profiles of the two phases change along the channel except for high values of Biot number and conductivity ratio, where they remain almost constant far from the inlet. Moreover, the local thermal equilibrium is fully achieved in the entire channel when the Biot number is high and the conductivity ratio is low, while, conversely, the local thermal non equilibrium is strongly pronounced on the whole field for small values of interstitial Biot number and conductivity ratio.dc201

INFLUENCE OF THE GEOMETRICAL SHAPE OF AGRICULTURAL FURROW (GROOVES) ON THE SEDIMENT TRANSPORT

SUMMARY In this experimental work, it is shown that the geometric shape of the farming grooves could play an important role in sediment dynamics. From these results, it appears that, for slopes less than 40%, the grooves with a sinus shape export the least sediment mass. For steeper slopes, agricultural furrows in a circle lead to the minimum of sediment transport. The rheological behaviour of the solid discharge depends also strongly on the geometry of the grooves

Les solutions multiples en convection naturelle instationnaire dans une enceinte fermée: influence de l'angle d'inclinaison

Dans cette étude, nous étudions numériquement la convection naturelle instationnaire dans une cavité carréefermée, dont les parois horizontales sont adiabatiques et les parois verticales sont chauffées à la demi-hauteur inférieure, et refroidies dans leur partie supérieure de la cavité. Nous étudions deux cavités inclinées correspondant à un angle de 0 et 45 degrés. L’écoulement est laminaire et bidimensionnel. Les équations de transfert adimensionnelles exprimées en terme de vorticité et de fonction de courant, ont été résolues avec la méthode implicite des directions alternées à laquelle on a associé la méthode de l’élimination de GAUSS. Nous analysons les effets du nombre de Rayleigh et de l’inclinaison sur les routes vers le chaos qu’emprunte le système