Jaime Fernández-Antón

Small Remotely Piloted Aircraft Systems (RPAS) are increasingly being developed with non-conventional geometries to enhance their performance, often drawing inspiration from nature. Among the most promising bio-inspired concepts are the wing geometries of dragonflies and the tubercles found on the ventral fins of humpback whales. Dragonflies are notable for their independent forewing and hindwing motion, which enable exceptional flight maneuvers and even gliding, a rare feature among insects. Their wings exhibit complex aerodynamics due to their undulating structure, which contributes to stability and lift generation. Similarly, the tubercles along the leading edges of whale fins have been shown to enhance lift and improve stall characteristics, particularly during high-agility maneuvers. This paper presents a computational analysis of the aerodynamic performance of non-conventional airfoils inspired by these natural features, comparing them with a conventional small RPA (INTA and ETSIAE-UPM). The results aim to highlight the potential benefits of employing bio-inspired airfoils in improving aerodynamic efficiency and flow control in small RPAS applications.

This work presents an experimental aerodynamic study of a Mars rover model, aimed at characterizing its flow behavior under Martian environmental conditions. Due to the extremely low Reynolds numbers associated with Mars’ thin atmosphere, the experiments were conducted using a scaled model of the rover manufactured via additive techniques. The study first focuses on understanding how the geometry of the rover influences the overall flow field, identifying key aerodynamic features such as separation zones, vortical structures, and flow reattachment regions driven by the complexity of the vehicle. A comprehensive investigation of the flow around the model was performed using both a hydrodynamic towing tank with dye injection for qualitative visualization, and particle image velocimetry (PIV) for quantitative flow field analysis in wind tunnel tests. After the general flow characterization, a more detailed local analysis was conducted using laser Doppler anemometry (LDA). This phase of the study targeted precise velocity measurements at specific locations corresponding to the MEDA (Mars Environmental Dynamics Analyzer) wind sensors onboard the rover. Quantitative results indicate that the central body induces a local flow acceleration of 20% to 40% relative to the free stream while severe turbulence was recorded in specific angular sectors, with velocity fluctuations reaching up to 120% for Sensor 1 and 90% for Sensor 2.

Heavy vehicles present high aerodynamic drag. This results in significant fuel consumption and, consequently, high emissions of harmful substances. This study examines the variation in aerodynamic drag in a European-type truck with different trailer configurations. Passive flow control by geometry modifications of the rear part of the trailer and active flow control using the Coanda effect were tested, with the aim of improving the aerodynamic efficiency of the vehicle. To achieve this, a modular structure of a 1:30 scaled truck was designed to enable different trailer configurations. Drag measurements were performed with a two-component external balance, and PIV tests were conducted to correlate the drag reduction with the aerodynamic changes behind the trailer. Passive control reduced drag by up to 5.7%, and active flow control reduced it by up to 12.6% compared to the unmodified base trailer. PIV flow visualization confirms that blowing effectively reduces the recirculation zone behind the trailer.

This study explores the aerodynamic behavior of bioinspired airfoils under extremely low Reynolds number conditions, simulating those found in the Martian atmosphere. Modified NACA 0018 profiles with sinusoidal leading-edge tubercles were tested to assess their influence on flow separation and overall aerodynamic performance. Experiments were carried out in a hydrodynamic towing tank using ink-based flow visualization, enabling detailed observation of the evolution of the separation point with varying angles of attack. The study focuses on comparing different tubercle configurations, analyzing how wavelength and orientation affect the aerodynamics of the airfoil. The results showed variations in flow stability and delayed separation compared to the baseline profile, indicating potential aerodynamic benefits. These findings offer valuable insights for the application of bioinspired geometries in the design of aerial platforms intended for Mars exploration and low-speed flight regimes, with special attention paid to Micro Aerial Vehicles (MAVs).

Understanding the thermal behaviour of radioisotope generators under Martian conditions is essential for the safe and efficient operation of planetary exploration rovers. This study investigates the heat transfer and flow mechanisms around a simplified full-scale model of the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) by means of Computational Fluid Dynamics (CFD) simulations performed with ANSYS Fluent 2023 R1. The model consists of a central cylindrical core and eight radial fins, operating under pure CO₂ at a pressure of approximately 600 Pa, representative of the Martian atmosphere. Four cases were simulated, varying both the reactor surface temperature (373–453 K) and the ambient temperature (248 to 173 K) to reproduce typical diurnal and seasonal scenarios on Mars. The results show the formation of a buoyancy-driven plume rising above the generator, with peak velocities between 1 and 3.5 m/s depending on the thermal load. Temperature fields reveal that the fins generate multiple localized hot spots that merge into a single vertical plume at higher elevations. The calculated dimensionless numbers (Grashof ≈ 10⁵, Rayleigh ≈ 10⁵, Reynolds ≈ 10², Prandtl ≈ 0.7, Nusselt ≈ 4) satisfy the expected range for natural convection in low-density CO₂ atmospheres, confirming the laminar regime. These results contribute to a better understanding of heat dissipation processes in Martian environments and may guide future design improvements of thermoelectric generators and passive thermal management systems for space missions.

The paper outlines an algorithm for the rapid aerodynamic evaluation of winglet geometries using the TORNADO Vortex Lattice Method. It is a very useful tool to obtain a first approximation of the aerodynamic properties and for performing an optimization of the geometry design. The TORNADO tool is used to systematically calculate the aerodynamic characteristics of various wings with wingtip devices. The fast response of the aerodynamic models allows obtaining a set of results in a remarkably short time. Therefore, the development of an algorithm to generate wing geometries with great ease and complex shapes is of vital importance for the mentioned optimization process. The basic outline of the algorithm, the equations defining the wing geometries, and the results for unconventional wingtip devices, such as blended winglets and spiroid winglets, are presented. Finally, this algorithm allows designing a procedure to study the improvement of aerodynamic properties (lift, induced drag, and moment). Some examples are included to illustrate the capabilities of the algorithm.

This article aims to highlight the importance of utilizing flow visualization techniques in the preliminary analysis of streamlined and bluff bodies, especially the potential use of visualization with ink in a water channel as a tool for a preliminary approach during fluid mechanics analysis. According to this, the study compares the results obtained using a classical flow visualization technique, ink injection in water, with those obtained through the employment of a laser-based measurement and visualization technique, called PIV, in a low-speed wind tunnel. The article briefly presents both techniques and highlights the importance of flow visualization in the analysis of aerodynamic bodies. This study focuses on flow over NACA airfoils at extremely low Reynolds numbers, which is of great interest for application in extraterrestrial atmospheres, such as on Mars. After obtaining images of the flow streamlines over the NACA 0018 airfoil, the results of both techniques were compared. The results indicated that there was good agreement between the visualization with the water channel and the PIV results, suggesting that the results obtained in the water channel represented a scientifically valid approximation and an essential complement to computational models that require experimental validation.

Flow visualization is necessary in fields such as engineering, since it allows us to know what is happening around the element being studied by means of a preliminary method, although it is relatively close to future research and computation methodology. The present project studies the interference at the anemometers of the Mars rover Perseverance, caused by the mast holding one of its cameras. After obtaining the model, manufactured by a 3D printer, it was placed inside a hydrodynamic towing tank, and red dye was added for a visual observation of the interference during the experiment. A comparison was made between the results achieved and those seen in a wind tunnel, realizing the high correlation they have. Finally, this paper promotes the use of the hydrodynamic towing tank in preliminary studies due to its low costs, considering the adequate comparison with other higher precision methodologies.

This paper presents a study based on wind tunnel research on biplane configurations. The objective of this research is to establish an experimental basis for relationships between the main geometrical parameters that define a biplane configuration (stagger, decalage, gap, and sweep angle) and the aerodynamic characteristics (C_L, C_D). This experimental study focuses on a 2D approach. This method is the first step towards dealing with the issue, and it allows the variables involved in the tests to be reduced. The biplane configuration has been compared with the monoplane configuration to analyze the viability for implementing the biplane configuration in the field of application for micro air vehicles (MAV). At present, the biplane and other unusual configurations have not been a common design for MAV; however, they do have unlimited future potential. A set of experimental tests were carried out on various biplane configurations at low Reynolds numbers, which allowed the criteria for selecting the best wing configuration to be defined. The results obtained here show that the biplane configuration provides a higher maximum lift coefficient (C_Lmax) than the planar wing (monoplane). Furthermore, it has a larger wetted surface than the planar configuration, so the parasitic drag increases for the biplane configuration. This research is focused on a drone flight regime (low Reynolds number), and in this case, the parasitic drag (profile drag) has an important role in the total drag of the airplane. This study considers whether the reduction in the induced drag due to three–dimensional configuration (biplanes, box–wings, and joined–wings) can reduce the total drag or if the increase in the parasitic drag is bigger. Additionally, the increase in lift and the decrease in parasitic drag (profile drag) will be studied to determine if they have a greater influence on the performance of the airplane than the increase in structural weight. Further research is planned to be performed on 3D prototypes, with the selected configurations, and applied to nonconventional wing planforms.