An official website of the United States government
This study investigates the aerodynamic performance of different flying sensors inspired by dandelion seeds, using COMSOL Multiphysics CFD simulation. Dandelion seeds are well known for their ability to remain suspended in the air for extended periods due to their lightweight structure, higher porosity, high drag, and the formation of a separated vortex ring (SVR) above the seed. Mimicking this behavior, five 2D and one 3D geometry were developed and analyzed first through steady-state simulations to explore how different design geometries influence passive flight performance. The primary aim is to identify an optimized structure that can achieve slower descent when realized from an altitude by drones for remote sensing. Steady-state results showed that although the drag coefficient generally decreased with increase in Reynolds numbers, porosity did not exhibit a constant trend across all designs. In some cases, geometries with lower porosity outperformed more porous ones. This may be due to their structural differences. SVR was observed in all designs. However, the distance between these SVR and geometry’s surface was small. While steady-state results give a fair indication of the aerodynamic behavior and relative performances of the various geometries, there are limitations. To address this, transient drop tests, currently under verification, will give a better understanding of the performances of these designs from which the best will be selected.
more »
« less
This content will become publicly available on July 16, 2026
Heat Transfer Effects on Aerodynamic Performance of Bioinspired Passive Flyers
This study aimed to investigate the aerodynamic and thermal behavior of dandelion diaspore analogs to explore the effect of coloration on the overall flow field. To do so, computational fluid dynamics simulations were performed on simplified porous disk models across varying absorptivities under steady-state and transient conditions. By coupling heat transfer and fluid dynamics, the simulations captured the influence of thermal gradients on stable vortex ring formation and overall drag forces. Results showed that increased surface temperature, caused by higher absorptivity, enhanced buoyancy forces, disrupted vortex ring formation, and elevated drag coefficients. Conversely, white-colored analogs exhibited lower thermal loading and reduced aerodynamic resistance. While the current model employed a rigid, porous disk approximation, it provides valuable insights into the effects on the fluid flow of unmanned, dandelion-inspired micro aerial vehicles (MAVs).
more »
« less
- Award ID(s):
- 2430771
- PAR ID:
- 10637154
- Publisher / Repository:
- American Institute of Aeronautics and Astronautics
- Date Published:
- ISBN:
- 978-1-62410-738-2
- Format(s):
- Medium: X
- Location:
- Las Vegas, Nevada
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We employ a novel computational modelling framework to perform high-fidelity direct numerical simulations of aero-structural interactions in bat-inspired membrane wings. The wing of a bat consists of an elastic membrane supported by a highly articulated skeleton, enabling localised control over wing movement and deformation during flight. By modelling these complex deformations, along with realistic wing movements and interactions with the surrounding airflow, we expect to gain new insights into the performance of these unique wings. Our model achieves a high degree of realism by incorporating experimental measurements of the skeleton’s joint movements to guide the fluid–structure interaction simulations. The simulations reveal that different segments of the wing undergo distinct aeroelastic deformations, impacting the flow dynamics and aerodynamic loads. Specifically, the simulations show significant variations in the effectiveness of the wing in generating lift, drag and thrust forces across different segments and regions of the wing. We employ a force partitioning method to analyse the causality of pressure loads over the wing, demonstrating that vortex-induced pressure forces are dominant while added-mass contributions to aerodynamic loads are minimal. This approach also elucidates the role of various flow structures in shaping pressure distributions. Finally, we compare the fully articulated, flexible bat wing with equivalent stiff wings derived from the same kinematics, demonstrating the critical impact of wing articulation and deformation on aerodynamic efficiency.more » « less
-
Abstract Rings and gaps are ubiquitous in protoplanetary disks. Larger dust grains will concentrate in gaseous rings more compactly due to stronger aerodynamic drag. However, the effects of dust concentration on the ring’s thermal structure have not been explored. Using MCRT simulations, we self-consistently construct ring models by iterating the ring’s thermal structure, hydrostatic equilibrium, and dust concentration. We set up rings with two dust populations having different settling and radial concentration due to their different sizes. We find two mechanisms that can lead to temperature dips around the ring. When the disk is optically thick, the temperature drops outside the ring, which is the shadowing effect found in previous studies adopting a single-dust population in the disk. When the disk is optically thin, a second mechanism due to excess cooling of big grains is found. Big grains cool more efficiently, which leads to a moderate temperature dip within the ring where big dust resides. This dip is close to the center of the ring. Such a temperature dip within the ring can lead to particle pileup outside the ring and feedback to the dust distribution and thermal structure. We couple the MCRT calculations with a 1D dust evolution model and show that the ring evolves to a different shape and may even separate to several rings. Overall, dust concentration within rings has moderate effects on the disk’s thermal structure, and a self-consistent model is crucial not only for protoplanetary disk observations but also for planetesimal and planet formation studies.more » « less
-
The coupled interaction between an unsteady vortical flow and dynamics of an aerodynamic structure is a canonical problem for which analytical studies have been typically restricted to either static or prescribed structural motions. The present effort extends beyond these restrictions to include a Joukowski airfoil on elastic supports and its aeroelastic influence on the incident vortex, where it is assumed that all vorticity in the flow field can be represented by a collection of line vortices. An analytical model for the vortex motion and the unsteady fluid forces on the airfoil is derived from inviscid potential flow, and the evolution of the unsteady airfoil wake is governed by the Brown and Michael equation. The aerodynamic sound generated by the aeroelastic interaction of an incident vortex, shed Brown-Michael vortices, and the moving airfoil is estimated for low-Mach-number flows using the Powell-Howe acoustic analogy.more » « less
-
The drag force on a spherical intruder in dense granular shear flows is studied using discrete element method simulations. Three regimes of the intruder dynamics are observed depending on the magnitude of the drag force (or the corresponding intruder velocity) and the flow inertial number: a fluctuation-dominated regime for small drag forces; a viscous regime for intermediate drag forces; and an inertial (cavity formation) regime for large drag forces. The transition from the viscous regime (linear force-velocity relation) to the inertial regime (quadratic force-velocity relation) depends further on the inertial number. Despite these distinct intruder dynamics, we find a quantitative similarity between the intruder drag in granular shear flows and the Stokesian drag on a sphere in a viscous fluid for intruder Reynolds numbers spanning five orders of magnitude. Beyond this first-order description, a modified Stokes drag model is developed that accounts for the secondary dependence of the drag coefficient on the inertial number and the intruder size and density ratios. When the drag model is coupled with a segregation force model for intruders in dense granular flows, it is possible to predict the velocity of gravity-driven segregation of an intruder particle in shear flow simulations.more » « less
