Summary 1.The flower of Brassica napus L. appears to be typically zoophilous (suited to animal pollination) because of its visually attractive petals, robust stigma and nectaries. Pollination by wind is feasible, however, and its likely effectiveness is not immediately foreseeable because of the complexity of interactions between objects and windborne particles. 2. Computational fluid dynamics (CFD) and wind-tunnel experiments were used to investigate the aerodynamic interactions between the flower and a windborne suspension of its pollen. 3. The flower's petals handicapped wind pollination by reducing the target efficiency of the upwind-facing stigma. For downwind-facing flowers, pollen reception was negligible. 4. Several aspects of the plant's architecture (floral structure, pollen cohesiveness, inflorescence structure) are uncompromisingly zoophilous. Estimates of the amount of wind pollination suggest that it is unlikely to be important for the long-distance dispersal of B. napus genes such as those from genetically modified varieties. 5. This study illustrates how CFD may become a powerful tool in future analyses of wind pollination.
Summary1. Under natural selection for sexual success, the reproductive organs of plants should evolve to become highly effective pollen receptors. Among wind-pollinated plants, larger reproductive structures appear counter-adapted to accumulate pollen by impaction on their windward surfaces, because airborne particles are less able to penetrate the thicker boundary layer of larger targets. Therefore, it has been proposed that wind-pollinated plants with pollen receptors on relatively large structures, like some grasses (family Poaceae), are architecturally adapted to create downstream vortices in which airborne pollen recirculates before accumulating on leeward surfaces. From this basis, the striking diversity among the grasses in the architecture of their flowering stems has been attributed in part to the existence of these contrasting mechanisms for effecting pollen receipt, namely impact collection and recirculatory collection. 2. We investigated the relative importance of impact and recirculatory collection in grasses by analysing a model system in silico using Computational Fluid Dynamics and by conducting in vivo experiments, both in a wind tunnel and outdoors, using two grass species with compact inflorescences, Alopecurus pratensis and Anthoxanthum odoratum. 3. Irrespective of the experimental approach, we found that although pollen recirculated in the leeward eddies of inflorescences, over 95% of the accumulated pollen was collected by windward surfaces. 4. In A. pratensis, the collection efficiency (proportion of oncoming pollen collected) was between 5% and 20%, depending on wind speed in the range 0AE5-1AE9 m s )1 and these levels conform to those predicted by a mechanistic model of impact collection.5. Our results demonstrate that grass species with larger inflorescences are, like those with smaller inflorescences, primarily impact collectors of airborne pollen, which suggests that dissimilar reproductive morphology among species cannot be attributed to differentiation in the mode of pollen capture and, instead, requires reference to other factors, such as the need to produce, protect and disperse seeds of different sizes in different environments.
In many pine species (Family Pinaceae), ovulate cones structurally resemble a turbine, which has been widely interpreted as an adaptation for improving pollination by producing complex aerodynamic effects. We tested the turbine interpretation by quantifying patterns of pollen accumulation on ovulate cones in a wind tunnel and by using simulation models based on computational fluid dynamics. We used computer-aided design and computed tomography to create computational fluid dynamics model cones. We studied three species: Pinus radiata, Pinus sylvestris, and Cedrus libani. Irrespective of the approach or species studied, we found no evidence that turbine-like aerodynamics made a significant contribution to pollen accumulation, which instead occurred primarily by simple impaction. Consequently, we suggest alternative adaptive interpretations for the structure of ovulate cones.aerodynamics ͉ computational fluid dynamics ͉ computed tomography ͉ wind pollination
The paper describes recent progress on numerical simulation of soft body impact onto a fibre reinforced composite wing leading edge structure. The work is based on the application of non-linear explicit finite element analysis to simulate the response of composite wing structures under soft body impact loads. Soft body impactors such as gelatine (substitute bird) or ice (hailstones) are highly deformable on impact and flow over the structure spreading the impact load. Therefore, first benchmark simulations were carried out for soft body impact onto a rigid target. Soft body impactor was modeled using the Arbitrary Lagrangian-Eulerian (ALE) method. The results obtained using this impact model for different velocity were compared to the experimental test results in terms of local pressure, including Hugoniot and stagnation pressures, and global load to validate the accuracy of the model. Then, the impact of soft body onto a composite wing structures was described. A composite failure model which includes ply damage and interplay delamination model has been used to predict impact damage in the structure modeled using shell elements. The simulation tool predicts the impact damage in leading edge structure.
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