Development of one-equation transition/turbulence models

This paper reports on the development of a unified one-equation model for the prediction of transitional and turbulent flows. An eddy viscosity--transport equation for nonturbulent fluctuation growth based on that proposed by Warren and Hassan is combined with the Spalart-Allmaras one-equation model for turbulent fluctuation growth. Blending of the two equations is accomplished through a multidimensional intermittency function based on the work of Dhawan and Narasimha. The model predicts both the onset and extent of transition. Low-speed test cases include transitional flow over a flat plate, a single element airfoil, and a multi-element airfoil in landing configuration. High-speed test cases include transitional Mach 3.5 flow over a 5{degree} cone and Mach 6 flow over a flared-cone configuration. Results are compared with experimental data, and the grid-dependence of selected predictions is analyzed

State of the world’s plants and fungi 2020

Kew’s State of the World’s Plants and Fungi project provides assessments of our current knowledge of the diversity of plants and fungi on Earth, the global threats that they face, and the policies to safeguard them. Produced in conjunction with an international scientific symposium, Kew’s State of the World’s Plants and Fungi sets an important international standard from which we can annually track trends in the global status of plant and fungal diversity

STUDY OF CFD VARIATION ON TRANSPORT CONFIGURATIONS FROM THE SECOND DRAG-PREDICTION WORKSHOP

This paper describes and analyzes a series of nearly 90 CFD test cases performed as a contribution to the second Drag Prediction Workshop, held in association with the AIAA in June 2003. Two configurations are included: DLR-F6 wing-body and wing-body-nacelle-pylon. The ability of CFD to predict the drag, lift, and pitching moment from experiment -- including the \delta " arising from the addition of the nacelle and pylon -- is assessed. In general, at a fixed angle of attack CFD overpredicts lift, but predicts the CL reasonably well. At low lift levels (CL < 0:3), CD is 20{30 drag counts (30{45%) high. At the target lift coe cient of CL =0:5, CD is overpredicted by between 11{ 16 counts. However, the primary contribution of this paper is not so much the assessment of CFD against experiment, but rather a detailed assessment and analysis of CFD variation. The series of test cases are designed to determine the sensitivity/variability of CFD to a variety of factors, including grid, turbulence model, transition, code, and viscous model. Using medium-level grids (6{11 million points) at the target lift coefficient, the maximum variation in drag due to different grids is 5{11 drag counts, due to code is 5{10 counts, due to turbulence model is 7{15 counts, due to transition is 10{11 counts, and due to viscous model is 4{5 counts. Other speci c variations are described in the paper