Abstract:In order to support the future thermal control and energy conservation design for the Mars rover, numerical studies on natural convection in CO 2 enclosures on Mars' surface were conducted for both horizontal and vertical enclosures. The parameters are as follows: the atmospheric pressure was 1000 Pa, the gravitational acceleration was 3.62 m/s 2 , and the Prandtl number was 0.77. The heat flux, temperature, and velocity fields of the CO 2 enclosures were obtained with the aspect ratio ranging from 5.56 to 200 and the Grashof number ranging from 430 to 2.6 × 10 4 . It was found that natural convection formed more easily in the horizontal enclosures than that in the vertical enclosures when the enclosures had same thickness. With the increasing thickness of the enclosures, Rayleigh-Bénard convections formed in the horizontal enclosures, while only single-cell convections formed in the vertical enclosures. The heat flux through the horizontal enclosures was greater than that through the vertical enclosures with the same thickness when natural convection formed. The maximum difference between them reached 35.26%, which was illustrated by the field synergy principle. A hysteresis phenomenon of the natural convection dominating the heat transfer was found in the vertical enclosure on Mars' surface. New values for the critical Grashof number and correlations for the average Nusselt number for both the horizontal and vertical CO 2 enclosures on Mars' surface were also developed.

No abstract

The rear plan is one of the key factors that affect the separation of air flow at the vehicle rear.It has important theoretical guidance and engineering significance to study the influence of the rear plan on wake flow field for the early development and design of vehicle shape.Based on a simplified SUV model, the drag coefficients of the models with different rear plans are calculated. The velocity separation, pressure distribution and energy dissipation of air flow at the vehicle rear are compared and analyzed,demonstrating that the rear plan has influence on air separation and the formation of wake vortex at the vehicle rear.It is found that with the decrease of the rear plan, the separation of the air flow at the vehicle rear becomes weaker, the wake vortex gets smaller, and the drag coefficient reduces.