Dispersal and germination of winged seeds of Brandisia hancei,a shrub in karst regions of China

Brandisia hancei(Paulowniaceae)is a widely distributed shrub in karst regions in southwestern China.Its seeds have a membranous wing,and they mature just before the rainy season begins.To assess the effect of the wing on seed dispersal and germination of B.hancei,we measured the dispersal distance at varying wind speeds and release heights,falling duration from different release heights,floating duration on still water,rates of imbibition of water,and drying and soil adherence to seeds.Germination experiments were conducted on intact and de-winged seeds immediately after harvest.The wing increased the falling duration in still air and the floating ability on water.Dispersal distance of winged and de-winged seeds did not differ at a wind speed of 2.8 m s1,but at 3.6 and 4.0 m s1 dispersal distances were greater for de-winged than for winged seeds.Seed wing had little effect of absorption and retention of water,but significantly increased soil adherence to the seeds.Mature seeds were non-dormant and germinated to over 90%with a mean germination time of about 10 days.By combining the environmental conditions in karst habitat with the seed traits of B.hancei,we conclude that dispersal and germination of winged seeds are adapted to the precipitation seasonality in heterogeneous habitats absence of soil.

Gust response of an elasto-flexible morphing wing using fluid–structure interaction simulations

Small and micro unmanned aircraft are the focus of scientific interest due to their wide range of applications.They often operate in a highly unstable flight environment where the application of new morphing wing technologies offers the opportunity to improve flight characteristics.The investigated concept comprises port and starboard adjustable wings,and an adaptive elastoflexible membrane serves as the lifting surface.The focus is on the benefits of the deforming membrane during the impact of a one-minus-cosine type gust.At a low Reynolds number of Re=264000,the morphing wing model is investigated numerically by unsteady fluid-structure interaction simulations.First,the numerical results are validated by experimental data from force and moment,flow field,and deformation measurements.Second,with the rigid wing as the baseline,the flexible case is investigated,focusing on the advantages of the elastic membrane.For all configurations studied,the maximum amplitude of the lift coefficient under gust load shows good agreement between the experimental and numerical results.During the decay of the gust,they differ more the higher the aspect ratio of the wing.When considering the flow field,the main differences are due to the separation behavior on the upper side of the wing.The flow reattaches earlier in the experiments than in the simulations,which explains the higher lift values observed in the former.Only at one intermediate configuration does the lift amplitude of the rigid configuration exceeds that of the flexible by about 12%,with the elastic membrane resulting in a smaller and more uniform peak load,which is also evident in the wing loading and hence in the root bending moment.

Influence of membrane wing active deformation on the aerodynamic performance of an aircraft model

The aerodynamic performance of a simplified aircraft model with a pair of actively deformed membrane wings is investigated experimentally in this work. The active deformation is achieved with Macro fiber composite(MFC) actuators, which are attached to the upper surface of the wings and occupied 13.7% of the wing surface area. Wind tunnel experiments are conducted to evaluate the influence of membrane active deformation on the aerodynamic performance of the aircraft. The results show that the membrane deforms and vibrates under the actuation which can effectively suppress the leading-edge separation and facilitate the reattachment. Therefore, compared with the rigid wing model, the lift coefficient of the actively deformed membrane wing model is enhanced remarkably from the angle of attack of 7° to 22°. The stall angle is delayed by 2°, and a maximum lift coefficient enhancement of 32.5% is reached, which shows a wide potential application in improving the aerodynamic performance of modern aircraft.

Application and Improvements of the Wing Deformation Capture with Simulation for Flapping Micro Aerial Vehicle

Wing deformation capture with simulation is a mixed experimental-numerical approach whereby the wing deformation during flapping is captured using high-speed cameras and used as an input for the numerical solver.This is an alternative approach compared to pure experiment or full fluid structure interaction simulation.This study is an update to the previous paper by Tay et al.,which aims to address the previous limitations.We show through thrust and vorticity contour plots that this approach can simulate Flapping Micro Aerial Vehiclex(FMAVs)with reasonable accuracy.Next,we use this approach to explain the thrust improvement when an additional rib is added to the original membrane wing,which is due to longer duration for the new wing to open during the fling stage.Lastly,by decreasing the number of points and frames per cycle on the wing,we can simplify and shorten the digitization process.These results show that this approach is an accurate and practical alternative which can be applied to general bio-inspired research.

Aerodynamic analysis of a generic wing featuring an elasto-flexible lifting surface

A three-dimensional-membrane-type wing is investigated applying fluid-structure-interaction computations and complementary experiments.An analysis for three Reynolds numbers is conducted at various angles of attack.The computations are performed by means of the TAU-Code and the FEM Carat++solver.Wind-tunnel tests are carried out for performance analysis and to estimate the accuracy of the computations.In the results,the advantages of an elasto-flexible-lifting-surface concept are highlighted by comparing the formvariable surface to its rigid counterpart.The flexibility of the material and its adaptivity to the freestream allow the membrane to adjust its shape to the pressure distribution.For positive angles of attack,the airfoil’s camber increases resulting in an increase in the wing lifting capacity.Furthermore,the stall onset is postponed to higher angles of attack and the abrupt decrease in the lift is replaced by a gradual loss of it.