SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 26 - DECEMBER 30, 2005

01 AERONAUTICS (GENERAL)

Includes general research topics related to manned and unmanned aircraft and the problems of flight within the Earth's atmosphere.

Also includes manufacturing, maintenance, and repair of aircraft.

For specific topics in aeronautics, see categories 02 through 09.

For information related to space vehicles see 12 Astronautics.

20050244446 Lawrence Livermore National Lab., Livermore, CA USA

March 2001 Working Group Meeting on Heavy Vehicle Aerodynamic Drag: Presentations and Summary of Comments and Conclusions

McCallen, R.; Greenman, R.; Flowers, D.; Dunn, T.; Owens, J.; May 14, 2001; 218 pp.; In English Report No.(s): DE2005-15013289; UCRL-ID-143848; No Copyright; Avail.: National Technical Information Service (NTIS)

A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory on March 28 and 29, 2001. The purpose of the meeting was to present and discuss technical details on the experimental and computational work in progress and future project plans. Due to the large participation from industry and other research organizations, a large portion of the meeting (all of the first day and part of the second day) was devoted to the presentation and discussion of industry's perspective and work being done by other organizations on the demonstration of commercial software and the demonstration of a drag reduction device. This report contains the technical presentations (viewgraphs) delivered at the meeting, briefly summarizes the comments and conclusions, and outlines the future action items. NTIS

Aerodynamic Drag; Drag Reduction

20050245240 Wichita State Univ., Wichita, KS, USA

Computational Study of Large Droplet Breakup in the Vicinity of an Airfoil

Tan, J.; Papadakis, M.; Sampath, M. K.; Oct. 2005; 76 pp.; In English Report No.(s): PB2006-101517; No Copyright; Avail.: National Technical Information Service (NTIS)

A study was conducted to assess the effects of aerodynamic forces on the behavior of water droplets traversing near an airfoil. The analysis was performed using the Taylor Analogy Breakup (TAB) model, which can simulate droplet oscillation and distortion.

In general, the TAB model is capable of modeling droplet breakup with an acceptable level of accuracy, but its application is limited to vibrational and bag breakup modes only. The model does not rely on a unique critical value (e.g., Weber number of 13.0) to determine breakup. Instead, droplet breakup occurs when the lateral radius of the distorted droplet exceeds the half-radius of an undisturbed droplet. Although the actual breakup modes near an airfoil are unknown, it is believed that the validations of the TAB model with the experimental data collated from investigations conducted with horizontal and vertical tunnels were appropriate for assessing droplet breakup near the airfoil because the flow fields in these tunnels were similar to those found near the airfoils used in the present study.

Before the parametric droplet breakup studies, the sensitivity of droplet breakup to the resolution of the computational mesh and the initial droplet release location was assessed. The findings from this sensitivity study were used in the computation of droplet breakup in the flow field of the following two-dimensional airfoils: two NACA0012 airfoils with chord lengths of 3 and 20 ft and a three-element, high-lift airfoil with chord length of 20 ft. Water droplets with diameters of 100, 500, and 1000 im were released at about 5 chords upstream of each airfoil.

The simulations showed that breakup generally occurred in regions with severe pressure gradient. It was also found that droplets that broke up near a wall surface did not have sufficient time to completely disintegrate before hitting the wall. This was the case with droplet diameters of 500 and 1000 im near the leading edge of the 20-ft chord NACA0012 airfoil and the leading edges of the slat and flap elements of the high-lift airfoil. NTIS

Aircraft Icing; Airfoils; Computational Fluid Dynamics; Drop Size; Drops (Liquids); Wind Tunnel Tests

Source: NASA.