Tunnel dryers typically employ flat double-sloped or dome-shaped collectors, which function adequately for single- rack systems but require separate components for multi- rack setups. Our innovative solution introduces an integrated trapezoidal collector that utilizes sidewalls as absorption surfaces, eliminating the need for additional units while optimizing space utilization. This study presents a comprehensive approach to designing and analyzing the trapezoidal solar collector through combined mathematical modeling and numerical simulation. Using Python's odeint library to solve thermal equations and design parameters, we identified critical interdependencies between collector components. Results demonstrate significant performance benefits: the trapezoidal design achieves 15-20% greater efficiency than conventional rectangular configurations at operational air velocities of 3.5 m/s. Under practical 900 W/m² solar irradiation, the system maintains optimal drying conditions by combining 2.5 m/s internal airflow with 4 m/s ambient wind, consistently delivering 60°C output air ideal for sensitive products like fish. The trapezoidal geometry addresses two key industry challenges - space efficiency for multi-bay systems and thermal performance optimization - by transforming sidewalls into active absorption surfaces. These findings suggest retrofitting existing tunnel dryers with trapezoidal collectors could substantially improve both energy efficiency and production throughput, particularly for temperature-sensitive food processing applications. The Python-based simulation framework further provides a valuable tool for system optimization across varying climatic and operational conditions.

The Kayanga/Geba river basin is a transboundary basin shared between Guinea, Senegal and Guinea-Bissau. It concentrates important natural resources, notably water resources on which Senegal and Guinea-Bissau are particularly dependent. The drastic reduction of these water resources due to rainfall variability and climate change has had an impact on agricultural production in the basin; hence the hydro-agricultural developments, in Senegalese territory, boost socio-economic activities by increasing productivity in both the rainy and dry seasons. The negative effects of these developments go beyond administrative boundaries. The transboundary management of this basin is a real challenge because the dams built in Senegal do not have the legal status of common dams of the OMVG whose mission is to promote cooperation between its member states. This article first analyses water control and some of the negative impacts of hydro-agricultural developments, and then the cooperation initiatives that the OMVG is trying to implement for rational and harmonious exploitation of the common resources of this basin.

The subject of natural convection heat transfer is motivated by a wide range of applications in engineering technology. The hemispherical cavity is a part of basic geometries although it is not widely studied. The effect of inclinaison on natural convection fluid motions in the gap between two eccentric hemispheres is numerically studied. The inner hemisphere is subjected to a heat flux of a constant density and the outer one is maintened isothermal. The walls separating the two hemispheres are thermally adiabatic. Equations are formulated with vorticity and stream-functions variables. It is also assumed the fluid incompressible and obeys the approximation of Boussinesq. These equations are written by using bispherical coordinates system and solved by using a finite difference method. The results show the topology of flow is strongly dependent on the inclinaison because the flow can change from a unicellular regime to a multicellular regime by varying the inclination from 0 to π. By increasing the Rayleigh number (103Ra7), the flow intensifies. The results are shown in terms of streamlines and isotherms during their transient evolution.

The Confluent and Niandouba dams were built in 1984 and 1997 respectively to better control water resources, increase agricultural production and promote local development. This article studies their evolution on the Kayanga/Geba River, a transboundary river between Guinea, Senegal and Guinea-Bissau, from its impoundment to the present day. The topographic characteristics analysed through the DTMs (Digital Terrain Models) show a flat shape for the Confluent Dam Lake and long plateaus for the Niandouba Dam Lake. The cross-sections present a variety of morphologies ranging from wide U-shaped valleys with sinuous bottoms to deep V-shaped valleys. The homogenisation and reconstruction of missing values were carried out using the regional vector method. The application of Pettitt’s statistical test on annual rainfall (1932-2019) indicates breaks of stationarity in 1967 or 1969. The post-breakage deficits range from 11.4% to 19.4%. The segmentation method corroborates the results of the Pettitt test. The variations of the surface area of the Confluent and Niandouba water bodies are linked to rainfall, evaporation and withdrawals for different uses. Their monitoring would allow for better management of available water resources but also for good planning of off-season crops.

Natural convection heat transfer in open or closed cavities takes place in different engineering areas. The hemispherical cavity is a part of basic geometries although it is not widely studied. The present paper reports the numerical study of natural convection in a closed hemispherical annulus delimited by two vertically eccentric hemispheres filled with Newtonian fluid (air in this case with Pr = 0.7) is conducted. The inner hemisphere is heated by a heat flux of constant density and the outer one is maintained isothermal. Based on the Boussinesq assumptions, the governing equations are numerically studied using unsteady natural convection formulated with vorticity and stream-function variables. These equations are written by using bispherical coordinates system and solved by using a finite difference method. The effect of the control parameters such as the Rayleigh number (103 ≤ Ra ≤ 106) or the eccentricity (e = ±0.2, ±0.5, 0) in the dynamic and thermal behaviours of the fluid is investigated.

Vegetable fibrous material is, today, increasingly used as a reinforcing element in structural or insulating composite materials. This use requires, first of all, control of the physical, hygroscopic and even thermal properties of vegetal fibers. In this context, the work presented focused on the experimental characterization of long fibers extracted from the baobab tree trunk (Adansonia Digitata L.). This study consisted in determining the density of the raw fibers and those having undergone various treatments as well as measuring their water absorption rates and moisture

In this paper we have studied the effects of the magnetic field on the flow of air (paramagnetic gas) in a rectangular parallelepiped on which two electromagnets are placed symmetrically.The analytical resolution of the Navier-Stokes equations being impossible, we resorted to a numerical modeling of the physical problem based on the method of finite volumes.The SIMPLE resolution algorithm made it easier for us to reach convergence.The results obtained from this simulation allowed to present the velocity as well as the heat transfer.The Reynolds number was in the range of 90 to 300 and the field number (Ne) from 5 to 100.The Prandtl number was set at 0, 71 (Prandtl of air).

Depositing an antireflection coating on the front surface of solar cells allows a significant reduction in reflection losses. It thus allows an increase in the efficiency of the cells. A modeling of the refractive indices and the thicknesses of an optimal antireflection coating has been proposed. Thus, the average reflective losses can be reduced to less than 8% and less than 2.4% in a large wavelength range respectively for a single-layer and double-layer anti-reflective coating types. However, the difficulty of finding these model materials (materials with the same refractive index) led us to introduce two notions: the refractive index difference and the thickness difference. These two notions allowed us to compare the reflectivity of the antireflection layer in silicon surface. Thus, the lower the refractive index difference is, the more the material resembles to the ideal material (in refractive index), and thus its reflective losses are minimal. SiNx and SiO2/TiO2 antireflection layers, in the wavelength range between 400 and 1100 nm, have reduced the average reflectivity losses to less than 9% and 2.3% respectively.

This paper attempts to analyze spatial variability, temporal trends and identify the discontinuities in the maximum and minimum temperature’s time series. This study is based on annual and monthly data from the Kolda Weather Station over a 50-year period. Our approach is essentially structured according to 3 components: first, anomaly index and cumulative sums are calculated and finally, Mann-Kendall statistical test is performed. Considering anomaly index, results highlight four categories of periods both annual and monthly scale: very hot, hot, very cold and cold for the maximums and the minimums. The analysis indicated that minimums increased significantly more than maximums. Regarding the CUSUM, results showed a downward trend for maximums and upwards for minimums on an annual and monthly basis. The dates of these breaks are 2001 and May for maximums and 1975 and February for minimums respectively at annual and monthly scale. Regarding Mann Kendall test, results show a significant downward and upwards trend respectively for maximums and minimums. On a monthly scale, we make the same observations except that the trend is not significant for minimums. It can be concluded that the strong warming experienced by the Kolda region in recent years is largely conditioned by the increase in minimum annual temperature.

A numerical study is presented on the problem of 2D natural convection in a differentially heated cavity. The equations governing this unsteady flow phenomenon were solved using the vorticity-stream function formulation of the Navier-Stokes equations and heat. The results obtained are compared with the results of the literature and make it possible to validate this approach. In this work, we studied the heat transfer in a cavity and we determined the variation of the local Nusselt number which allows obtaining the rate of thermal transfer by convection in an enclosure. We analyzed thermal fields for different Rayleigh numbers by selecting two points to visualize temperature fluctuations over time. Thus, the creation of the ascending and descending movements of the fluid inside the cavity was analyzed. We have also established temperature histograms for the graphical presentation of the temperature distribution. The modeling of the two-dimensional problem was established using a “Fortran 90” calculation code. The results also show the different vorticity contour maps in laminar flow regime. We have presented our results of numerical simulations using a visualization tool. The Rayleigh number varies in the range of 103 to 106 for a Prandtl number equal to 0.72 corresponding to air.

Spatial monitoring of climate behavior through rainfall variability is important step for the better understanding of the water resources in the river system. This paper aims to highlight rainfall variability at yearly scale and identify the various climate situations and characteristics of the study area during studied chronicle in the lower valley of the Casamance river basin. Three rainfall stations Ziguinchor, Bignona and Oussouye over the period of 55 years on average acquiring from ANACIM database (National Agency of Civil Aviation and Meteorology), have been selected for this purpose. Choice of rainfall is due to the fact that it is a key variable in West Africa in general and more specifically over the Sahel region where economies, livelihoods and food security are highly dependent on rained agriculture. To reach our objective, we have proceded through some analysis based on rupture detection testing (Pettitt, Hubert, Buishand and Lee and Heghinian test) and randomness testing (Autocorrelogram and correlation test of Rank) at the 5% significance level, while using the Khronostat software. Results show decreasing shift and randomness for all three stations the probabilities of this break are given by Lee and Heghinian test and are equal to 0.57142 for Ziguinchor, 0.354188 Bignona and 0.2846 for Oussouye. Rupture detection test indicate the same shift date established in 1967 for all stations. This study provides interesting opportunities to climate experts and water stakeholders in understanding the link between climate instability and water availability, thus contributing to the sustainable management of water resources.

In this present work, we study heat transfer in a confined environment. We have to determine the thermal and dynamics fields of the cavity while observing the effect of the Rayleigh number which depends on the characteristics of the fluid and the temperatures imposed. The behavior of boundary layers in natural convection is analyzed along this square cavity. The central halves of its vertical walls are heated at different temperatures. The left active part is at a higher temperature than the one on the right wall. The remaining inactive parts and the horizontal walls (upper and lower) are adiabatic. The thermal and dynamic modeling of two-dimensional problem was done using a calculation code Fortran 90 and a visualization software ParaView based on the finite volume method. The equations governing this phenomenon of unsteady flow have thus been solved. This allows the modeling of both air flow and heat transfer with a numerical stabilization of the solution. So, we have presented our results of numerical simulations using a visualization tool. The results show the different velocity and temperature curves, velocity vectors and isotherms in laminar flow regime.

By using a bicylindric coordinates and vorticity-stream function formalism, the authors study the natural convection in a porous medium in an enclosure delimited by portions the cylindrical enclosure. After having a dimensionnalise our equations, the space discretization is performed using a finite difference method while a purely implicit schema is adopted for the time discretization. The algebraic systems of equations of the discretization are solved by a Successive under Relaxation method (SUR). The results obtained show the dependence of the heat transfers in various porous median (several of the Darcy number).

In West Africa, there is serious asymmetry on food safety between consumers and food producers. This made that the management system of food safety in many developing countries became a top priority for authorities and decision makers. In Senegal, the government has selected the flood plain of Kayanga River to develop irrigated agriculture through rice cultivation to promote the food safety. For this, two dams (Niandouba and Confluent) have been built to reinforce water availability .The management of this hydraulic system required the better knowledge of its water resources through the dynamic of the flow. In this paper, we used Hec-ras model to compute the flow characteristics to analyze the hydraulic behavior of this system. The river reach selected, is located between the Niandouba dam and Kounkane threshold. From the DEM of this area, we have divided the river reach into 78 cross sections perpendicular to flow direction and numbered from 1 to 78. Arcgis software is used to extract the bathymetry for each cross section and the distance between two adjacent cross sections. This step allows creating the river geometry with Hec-ras. Four stream flows have successively fixed at Niandouba dam outlet as upstream boundaries. For each stream flow, Hec-ras calculate flow characteristics including: water surface profiles, energy grade line, water surface elevation, flow velocity, flow area, total surface area, volume, wetted perimeter, Froude number, top width, specif force, shear total, power total ,friction loss, head loss, conveyance total, and slope. The high, low and constant flow characteristics areas have been located. The large and narrow section sectors have also been identified allowing estimating floodplain. Certain of these flow characteristics such as the volume, total surface area…decrease from upstream to downstream. Flow velocities are substantially higher in the main channel than in the floodway. This study provides an opportunity for stakeholders to identify important elements of irrigated agriculture for investment plans in this area.

In this work, the author modeled the simultaneous transfers of heat and mass in a paraboloidal pond of retention filled with water and in a layer of fluid over the pond in unsteady regime; the interface of the pond is traveled by a forced hot air. In the water, he used the formalism vorticity-stream function to return linear and more moldable quasi-numerically the transfers equation. To solve the equations in the air which is constituted by a mixture dry air and of steam, the hypotheses of the thermal, mass and dynamic laminar limit layers are adopted. The dimensionless equations are resolved by means of the implicit and semi methods implicit method. In this work the author analyzed the regime establishment and the influence of the Reynolds number on the local values. The obtained results are calculated for numbers of Reynolds varying from 10 to 400.

The aim of our study is to describe the distribution of air temperature and its effect upon a product to dry (e.g cowpeas), processing in the drying cabin. Indeed, the selected dryer operates in indirect mode. It is like an adiabatic cupboard in a vertical position with shelves that play a role of grid supporting the products to be dried. Thus, we have described a mathematical model which describes the simulation of the thermal variations in the drying room and the drying product itself by setting the temperature and the air rate entering the dryer. This model takes into account the character of the transfer air-product globally. The resulting equations are rescaled before being solved by the method of finite differences.

Using a bi-cylindrical coordinates system and a vorticity-stream function formulation, the authors study numerically the two dimensional unsteady natural convection of a Newtonian fluid bounded by portions of cylinders. A spatial discretization based on the finite difference method is used to approximate the dimensionless equations. While a purely implicit scheme is adopted for the time discretization. The algebraic systems of equations resulting from the discretization are solved by a Successive under Relaxation (SUR) method. The authors analyzed the effects of the Rayleigh number on the dynamic of the system. The analysis of the thermal and flow field showed that for Rayleigh number greater than 5.10 6 the transfers inside the enclosure are dominated by convection.

Effects of the inclination angle fi on a two dimensional natural convection in an enclosure delimited by portions of cylinders has been analyzed numerically. The Rayleigh number and the angle of inclination are used as control parameters for flow and heat transfer. fi was varied from 0 to pi, for a range of Rayleigh number from 105 to 107. The governing equations are solved with finite difference method with a purely implicit scheme for time discretization. The algebraic systems of equations are solved by a Successive Under Relaxation (SUR) method. The results showed that if the transition from a pseudo-conductive regime to a convective one is slightly affected by fi, the thermal and dynamical fields are very different according to whether fi is superior or equal to pi/2

Nous présentons dans cet article une série de simulations menée sur un capteur solaire boîte qui a la forme d’une pyramide tronquée et renversée. Afin d’améliorer les performances thermiques, le capteur est muni d’un double vitrage et les parois latérales sont inclinées par rapport à la verticale et sont recouvertes d’un mince film d’aluminium. La variation de l’inclinaison des parois latérales a une nette influence sur la production de chaleur. Ainsi les résultats des différentes configurations sont présentés et une étude comparative a abouti au choix d’une configuration permettant d’obtenir la température la plus élevée.