Search Results

The reproductive ontogeny of ‘Super-Dwarf’ wheat grown on the space station Mir is chronicled from the vegetative phase through flower' development. Changes in the apical meristem associated with transition from the vegetative plhase to floral initiation and development of the reproductive spike were all typical of ‘Super Dwarf’ wheat up to the point of anthesis. Filament elongation, which characteristically occurs just prior to anthesis (during floral development stage 4) and moves the anthers through the stigmatic branches thus facilitating pollination, did not occur in the flowers of spikes grown on Mir. While pollen did form in the anthers, no evidence of pollination or fertilization was observed. Analysis of pollen idlentified abnormalities; the presence of only one nucleus in the pollen as opposed to the normal trinucleate condition is likely an important factor in the sterility observed in wheat grown on Mir.

Experimental measurements of a 1:20-scale tractor-trailer configuration were obtained in the 48- by 32-Inch Subsonic Wind Tunnel at NASA Ames Research Center. The model included significant details of the underbody geometries of both the tractor and trailer. In addition, the tractor included a flow-through grill and a simplified engine block to provide an approximation of the flow through the engine compartment. The experiment was conducted at a Reynolds Number of 430,000 for yaw angles between ±14 deg. The measurements included forces and moments and static surface pressures for various underbody configurations. Simple fairings on the underbodies of the tractor and trailer both yielded a reduction in the wind-averaged drag coefficient of 0.018 (2.7%) when tested separately. A horizontal plate designed to block vertical flow in the tractor-trailer gap provided marginally higher drag reduction (0.021, or 3.2%).

The 1/8-scale Generic Conventional Model was studied experimentally in two wind tunnels at NASA Ames Research Center. The investigation was conducted at a Mach number of 0.15 over a Reynolds number range from 1 to 6 million. The experimental measurements included total and component forces and moments, surface pressures, and 3-D particle image velocimetry. Two configurations (trailer base flaps and skirts) were compared to a baseline representative of a modern tractor aero package. Details of each configuration provide insight into the complex flow field and the resulting drag reduction was found to be sensitive to Reynolds number.

Three-component Particle Image Velocimetry (3D PIV) is a fluid velocity measurement technique that has evolved from the laboratory to become a method appropriate for use in large-scale wind tunnel testing. An example application of 3D PIV in a wind tunnel test is described. The PIV technique was applied to characterize the wake of The Ground Transportation System (GTS) model developed for the Department of Energy (DOE) Heavy Vehicle Drag Reduction (HVDR) program. The test was performed in the Ames/Army 7×10 foot wind tunnel. The objective of the PIV measurements was to validate the HVDR computational fluid dynamics code. The PIV method and PIV system are described. Sample truck wake data with and without boattail attachments are shown. 3D PIV system successfully captured the effects of the boattails on the truck wake.

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California. Companion computer simulations are being performed by Sandia National Laboratories, Lawrence Livermore National Laboratory, and California Institute of Technology using state-of- the-art techniques, with the intention of implementing more complex methods in the future.

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. Experimental validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California (USC). Companion computer simulations are being performed by Sandia National Laboratories (SNL), Lawrence Livermore National Laboratory (LLNL), and California Institute of Technology (Caltech) using state-of-the-art techniques.