A Numerical Analysis of the Flow in a Carousel Wind Tunnel in Martian Atmospheric Conditions

Abstract

With new rovers landing on Mars, like the Perseverance rover in 2020, the interest in Mars has grown recent years. The atmospheric conditions on Mars result in challenging conditions due to its low density atmosphere and extremely low temperatures. With a density on Mars that is 1% of that on Earth, creating sufficient lift for vehicles to fly becomes a challenge. The low density results in low Reynolds numbers. The low temperature has an effect on the speed of sound, due to which the Mach number is significantly higher at the same flow velocity compared to Earth. Airfoil data at these conditions, low Reynolds number - high Mach number, are sparse, but crucial for design of aerial vehicles. Next to the aerodynamic conditions, dunes on Mars are formed and migrate. The parameter of interest which defines the conditions required for transportation of particles is the threshold shear velocity. This parameter has been determined by different analytical expressions. However, the outcome remains a broad range, which point out the difficulty and inaccuracy of the results. Therefore, in this document, the design of a carousel wind tunnel is investigated to determine its feasibility to perform aerodynamic and aeolian measurements. The carousel wind tunnel consists of two concentric drums, of which the inner one rotates. The carousel wind tunnel is analysed by a computational fluid dynamics analysis with the k - ω turbulence model. The results indicate that due to secondary flow effects and the wake of a test object, no accurate aerodynamic measurements can be performed. Aeolian measurements are deemed feasible, with increased accuracy at sufficiently high rotational velocities.