This is not meant to be a comprehensive presentation and interpretation of all analysis results, but rather a summary of what has been accomplished and is available to users upon request.

Airflow and particle trajectories around specific C-130 fuselage locations were first calculated by Norment and Zalosh (1974), using a potential flow panel method. This method uses an inviscid and incompressible assumption and so does not account for the aircraft boundary layer. The boundary layer has been computed to be 3.5" at fuselage station (FS) 350 (Whitten, 1960). Both of the locations analyzed were on the side of the aircraft, at FS 177 and FS 307. (Current side apertures on the NCAR C-130 are between FS 277 and FS 350). Greater than 20% enhancement of unit density particles between about 20 and 300 microns in size were predicted at FS 277 at 10" away from the fuselage. At 18" from the fuselage, such enhancements were still predicted for particles 50 to 200 microns in size. Farther back at FS 350, 100 to 300 micron particles were actually shadowed at distances less than 14" from the fuselage, meaning that they never reach this area. Similar results can be estimated from King (1974).

Norment's code was implemented at NCAR in the early 1990s and was first used for the King Air and Electra aircraft (Twohy and Rogers, 1993). For the C-130, airflow was calculated at fuselage station 245 (just aft of the door) and fuselage station 300 (second window port), in a vertical plane along the aircraft centerline and in a horizontal plane at the widest point of the fuselage. Results are also available for locations near and ahead of the aircraft nose. Particle trajectories were analyzed near the nose (for the community aerosol inlet), but not for the other fuselage locations. Airflow and particle trajectories were calculated for multiple locations below the C-130 wing, including near the PMS canisters on the wingtip. The wingpod itself was modeled separately, with the PMS canisters. The code generating these results is no longer being used at RAF, but the output data are available upon request.

More recently, the CFD package Fluent was used to calculate airflow around the C-130 wing, the wingpod and a special instrument mount plate on the pod. The wing and pod were not modeled together as one unit, however, and were never critically compared to the early potential flow results. (The potential flow assumptions are not required for Fluent). These computations were done by a post-doc who is no longer at NCAR, and we are currently working to retrieve these results.

References

King, W. D., 1984: Air flow and particle trajectories around aircraft fuselages.I: Theory. J. Atmos. Ocean. Tech., 1, pp. 5-13.

Norment, H. and R. Zalosh, 1974: Effects of airplane flow fields on hydrometeor concentration measurements. Allied Research Associates, AFCRL TR-74-0602.

Twohy, C.H. and D. Rogers, 1993: Airflow and water drop trajectories at instrument sampling points around the Beechcraft King Air and Lockheed Electra. J. Atmos. Oceanic Technol., 10, pp. 566-578.

Whitten, R. P., 1960: An investigation of some aerodynamic factors affecting meteorological instrument readings on a C130A research aircraft. Allied Research Associates, AFRD TN-60-454.