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During hypersonic reentry, a spacecraft experiences several different fluid flow regimes, which usually require the application of different software frameworks to simulate the respective regimes. This study aims to evaluate the hyStrath library for predicting aerodynamic lift and drag coefficients of complex three-dimensional (3D) geometries during hypersonic Mars reentry, using flight data of the Viking 1 mission as reference. A range of altitudes (h = 30 − 140 km) and Mach numbers (M = 13 − 24) where flight data is available is considered, covering the rarefied, transitional, and continuum fluid flow regimes. The hyStrath library contains a set of modified solvers and state-of-the-art thermophysical and chemistry models within the framework of OpenFOAM, dedicated to modeling high-enthalpy hypersonic flow problems. Depending on the flow regime, the computational fluid dynamics solver hy2Foam or direct-simulation Monte Carlo solver dsmcFoam+ are employed in the study. Because hyStrath is based on OpenFOAM, it allows the use of an unstructured adaptive mesh refinement approach for arbitrary geometries. We obtain excellent results throughout all investigated flow regimes and Mach numbers with an average deviation of 1.5% and 2% from the measured lift and drag coefficients, respectively. The applicability of the framework for accurately modeling both rarefied and continuum Mars reentry problems of complex 3D geometries such as the Viking capsule is demonstrated. [ABSTRACT FROM AUTHOR]

Computational rhinology is a specialized branch of biomechanics leveraging engineering techniques for mathematical modelling and simulation to complement the medical field of rhinology. Computational rhinology has already contributed significantly to advancing our understanding of the nasal function, including airflow patterns, mucosal cooling, particle deposition, and drug delivery, and is foreseen as a crucial element in, e.g., the development of virtual surgery as a clinical, patient-specific decision support tool. The current paper delves into the field of computational rhinology from a nasal airflow perspective, highlighting the use of computational fluid dynamics to enhance diagnostics and treatment of breathing disorders. This paper consists of three distinct parts—an introduction to and review of the field of computational rhinology, a review of the published literature on in vitro and in silico studies of nasal airflow, and the presentation and analysis of previously unpublished high-fidelity CFD simulation data of in silico rhinomanometry. While the two first parts of this paper summarize the current status and challenges in the application of computational tools in rhinology, the last part addresses the gross disagreement commonly observed when comparing in silico and in vivo rhinomanometry results. It is concluded that this discrepancy cannot readily be explained by CFD model deficiencies caused by poor choice of turbulence model, insufficient spatial or temporal resolution, or neglecting transient effects. Hence, alternative explanations such as nasal cavity compliance or drag effects due to nasal hair should be investigated. [ABSTRACT FROM AUTHOR]

To reduce the drag of underwater vehicles during navigation, this paper proposes a skin imbricated with bionic placoid scale based on micro-Stewart mechanism. The skin is composed of bionic shark placoid scales and Stewart structure with multi-dimensional motion characteristics, which can well simulate the multi-dimensional oscillation motion of shark scales during swimming. A co-simulation platform of computational fluid dynamics and multi-body dynamics is established to investigate the impact of oscillating parameters (heave and pitch) on the drag reduction performance of the skin. The novel skin shows a remarkable drag reduction performance, with a relative drag reduction rate over 20% (up to 33%) in the range of Re = 105 ∼ 106. It is found that the oscillation motion generated by the placoid scales can cause the fluid inside the skin to spray upward, which can increase the thickness of the fluid boundary layer, revealing the drag reduction mechanism of the skin to some extent. Moreover, the pitching motion of the placoid scale is more effective in drag reduction than the heaving motion in the condition of Re = 105. It is expected that applying this skin to underwater vehicles can achieve satisfactory drag reduction effects. [ABSTRACT FROM AUTHOR]

This study focused on the effects of longitudinal and lateral spacing on the aerodynamic drag characteristics of the whole team and each member in speed skating team pursuit competition (SSTPC). To further understand the effect of formation spacing on the aerodynamic drag distribution on the skater body surface, a combination of experiments and numerical simulations was performed. Three identical mannequins were used to conduct wind tunnel tests and the results were compared with computational fluid dynamics (CFD) simulation results obtained using a 3D digital model of the mannequin. The results showed that, as the longitudinal spacing decreased, greater drag reduction was gained by the whole team and three members (leading, middle, and last). When the longitudinal spacing was 1.05 L (L refers to body length), the whole team and the three members had drag reduction of 31.5%, 10.1%, 42.1%, and 42.3%, respectively. After each 0.1 L increase in longitudinal spacing, the whole team and the leading, middle, and last skaters lost 2.0%, 1.8%, 2.3%, and 1.8% of their drag reduction, respectively. When the leading skater moved laterally to 0.2 W (W refers to body width), the whole team and the last skater achieved an additional drag reduction of 0.7% and 4.2%, respectively. The CFD simulation results further revealed that the body surface drag distribution trend of the leading skater was similar to that of the isolated skater, with the largest proportion of drag being located on the calves. The drag on the torsos, thighs and calves of the middle and last skaters was significantly smaller than that on the corresponding parts of the isolated skater, and its proportion was comparable. [ABSTRACT FROM AUTHOR]

This paper presents a computational fluid dynamics (CFD) study investigating the aerodynamic effects of a retractable flap on a passenger vehicle. The predominant aim of the study is to evaluate the impact of the flap's deployment on the vehicle's aerodynamic performance, specifically focusing on improving the overall braking efficiency by increasing the aerodynamic drag. The CFD simulations were conducted using the ANSYS, by employing a validated turbulence model and a detailed vehicle geometry. The CFD results demonstrated that the deployment of the retractable flap resulted in noticeable changes in the vehicle's aerodynamics. The flap's presence altered the flow field around the vehicle, increasing the overall aerodynamic drag. Also, the flap's angle significantly affected the aerodynamic performance, with certain angles resulting in more favourable flow patterns and reduced drag coefficients. [ABSTRACT FROM AUTHOR]

A non-pneumatic tire, in which the tire pressure is replaced by an elastic support body, is called an airless tire with elastic support (ALTES). In this study, the differences in the aerodynamic characteristics between ALTES and pneumatic tire (PT) were comparatively investigated using URANS simulations based on the DrivAer model. It was found that the vehicle body drag coefficient of the vehicle equipped with ALTES was reduced by 27% compared to that of the vehicle equipped with PT and had a significant drag-reduction effect. The drag coefficient and moment coefficient of the ALTES wheels are 2 and 3.5 times those of the PT wheels, respectively, which offset the drag-reduction benefits. The drag coefficient and aerodynamic power loss of vehicles equipped with ALTES were 97–102% and 108.5%–114% of those of vehicles equipped with PT. It is reasonable and necessary to evaluate the aerodynamic performance of ALTES based on the aerodynamic power loss. By suppressing the wheel ventilation flow and reducing the wheel drag, the aerodynamic wheel cover can reduce the aerodynamic power loss of a vehicle equipped with ALTES by 12%, and the vehicle aerodynamic performance is comparable to that of a PT. • The aerodynamic performance of a non-pneumatic tire should take into account both drag and ventilation moment. • Non-pneumatic tires have a significant drag-reduction effect on the vehicle body. • Both of the drag and ventilation moment of non-pneumatic tires are higher than those of pneumatic tires. • The bluff-body shape and open-ventilated characteristics of non-pneumatic tires result in a higher level of aerodynamic loss. • Non-pneumatic tires equipped with an aerodynamic wheel cover can overcome their aerodynamic performance disadvantages. [ABSTRACT FROM AUTHOR]