In this article, we have numerically studied the phenomenon of laminar mixed convection in a ventilated square cavity. The vertical walls of the cavity are subjected to a temperature gradient while the horizontal walls are constrained as adiabatic. We used the finite volume method to discretize the system of non-dimensional equations and a purely implicit scheme for the temporal discretization. The results were presented in the form of hydrodynamic and thermal fields for different values ​​of the Richardson number with the number of Reynolds constant. We found that the increase of the Richardson number with a fixed Reynolds number Re=100 allows us to visualize the evolution of the system and to appreciate the efficiency of the bottom ventilation.
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 ( 3 7 10 10 Ra < < ), the flow intensifies. The results are shown in terms of streamlines and isotherms during their transient evolution.
A two-dimensional numerical study of natural convection in a tunnel whose plane is sinusoidal with an opening on the horizontal ceiling is presented. In this work, we study the thermoconvective instabilities of air in a tunnel closed at both ends and heated by the floor. The study was carried out for different cases of geometry by varying the thickness of the sinusoid and the height of the tunnel. In order to create a transverse movement of the air, we heated the floor to the temperature f T and kept the horizontal ceiling at the temperature g T such that g f T T < . This work has a lot of scope of application ranging from geothermal flow to the civil engineering like ventilation in the case of tunnels and thermal comfort of buildings. The Navier Stokes equations that model this problem have been solved using the numerical method with simplifying assumptions such as the Boussinesq hypothesis. And finally an interpretation of the results of the simulations has been made taking into account the variation of the form factors such as the amplitude of the sinusoid for Rayleigh number 4 6 2 10 7 10 a R × ≤ ≤ × and Prendtl number P r = 0.71.
In this work, we numerically study laminar flows in forced convection in a U -shaped channel. Our study was based on a finite volume method by the fluent code carried out for a Reynolds number varying in the range 100<Re<700, and the Rayleigh number Ra=105 and Prandtl number Pr=0.72. As a function of the Reynolds number, the results obtained are presented in the form of the thermal and dynamic field, the variation of the Nusselt number and the variation of the speed and average temperature at the outlet of the channel as a function of Re also. We see a significant improvement in heat exchange along all the walls of the channel as the number increases Re.
In this article, we study the influence of the Rayleigh number on the natural convection of air between two square cavities. The internal cavity is subjected to a constant flow of heat while the external cavity is kept at a constant temperature. This temperature difference leads to a decrease in the density that represents the motor of the movement. Especially since the information on pressure is not sufficient, we have used the formalism vorticity current function to eliminate the pressure term in the equation of movement. Adimensionnals equations transfers were solved using the finite volume. In order to examine the heat transfer between the cavity and the fluid, we have used Rayleigh values ranging from 103 ≤ Ra ≤ 106 and Prandtl Pr = 0.7. The results obtained have shown from Rayleigh number Ra = 103, the isotherms line are quasicircular and bicellular current lines of high intensity on both sides of the median axis. When we increase the Rayleigh number from Ra = 104 through Ra =105 to Ra = 106, we have noticed that the isotherms tend to decrease and split. This results in the formation of small oscillations in the middle of the internal cavity. For the current lines, we have noticed the formation of secondary cells in the upper cavity and low movement in the horizontal cavity.
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