Engineering topics

Wilcox, F. A.

Publications and source records attributed to Wilcox, F. A..

11 records

NASA NTRS1975

Reynolds number effects on boattail drag of exhaust nozzles from wind tunnel and flight tests

A family of nacelle mounted high angle boattail nozzles was tested to investigate Reynolds number effects on drag. The nozzles were flown on a modified F-106B and mounted on scale models of an F-106 in a wind tunnel. A 19- to 1-range of Reynolds number was covered as a result of the large size differences between models and by flying over a range of altitude. In flight the nozzles were mounted behind J-85 turbojet engines. Jet boundary simulators and a powered turbojet engine simulator were used on the wind tunnel models. Data were taken at Mach numbers of 0.6 and 0.9. Boattail drag was found to be affected by Reynolds number. The effect is a complex relationship dependent upon boundary layer thickness and nozzle boattail shape. As Reynolds number was increased from the lowest values obtained with scale models, boattail drag first increased to a maximum at the lowest flight Reynolds number and then decreased.

Wilcox, F. A.↗

NASA NTRS1974

Reynolds number effects on boattail drag of exhaust nozzles from wind tunnel and flight tests

A family of nacelle-mounted high-angle boattail nozzles was tested to investigate Reynolds number effects on drag. The nozzles were flown on a modified F-106B and mounted on scale models of an F-106 in a wind tunnel. A 19-to-1 range of Reynolds number was covered as a result of the large size differences between models and by flying over a range of altitude. In flight the nozzles were mounted behind J-85 turbojet engines. Jet boundary simulators and a powered turbojet engine simulator were used on the wind tunnel models. Data were taken at Mach numbers of 0.6 and 0.9. Boattail drag was found to be affected by Reynolds number. The effect is a complex relationship dependent upon boundary layer thickness and nozzle boattail shape. As Reynolds number was increased from the lowest values obtained with scale models, boattail drag first increased to a maximum at the lowest flight Reynolds number and then decreased.

Wilcox, F. A.↗

NASA NTRS1974

Reynolds number effects on boattail drag of exhaust nozzles from wind tunnel and flight tests

A family of nacelle mounted high angle boattail nozzles was tested to investigate Reynolds number effects on drag. The nozzles were flown on a modified F-106B and mounted on scale models of a F-106 in a wind tunnel. A 19- to 1-range of Reynolds number was covered as a result of the large size differences between models and by flying over a range of altitude. In flight, the nozzles were mounted behind J-85 turbojet engines. Jet boundary simulators and a powered turbojet engine simulator were used on the wind tunnel models. Data were taken at Mach numbers of 0.6 and 0.9. Boattail drag was found to be affected by boattail number. The effect is a complex relationship dependent upon boundary layer thickness and nozzle boattail shape. As Reynolds number was increased from the lowest values obtained with scale models, boattail drag first increased to a maximum at the lowest flight Reynolds number and then decreased.

Wilcox, F. A.↗

NASA NTRS1973

Comparison of ground and flight test results using a modified F106B aircraft

A F106 aircraft was modified by installing two additional underwing nacelles housing afterburning J85 engines to study exhaust nozzles in flight at Mach numbers up to 1.3. Installation effects were determined for several nozzles by comparing flight and wind-tunnel data. The effect is to decrease boattail drag and delay its drag rise Mach number to about 0.98. A study of Reynolds number effects, carried out at subsonic speeds with afterburning turbofan engines showed boattail drag to be sensitive to Reynolds number. In flight, drag was highest at the lowest Reynolds number, and decreased as the Re number was increased. Static and flyover noise measurements showed that, except for special cases, noise levels at takeoff (M = 0.4) were higher than predicted from static data.

Wilcox, F. A.↗

NASA NTRS1973

Comparison of ground and flight test results using a modified F106B aircraft

Two aft underwing nacelles housing afterburning J85 engines were added to an F106 to study exhaust nozzles in flight at Mach numbers up to 1.3. Installation effects were determined for several nozzles by comparing flight data to data from an isolated wind tunnel model. Reynolds number effects were studied at subsonic flight speeds for nozzles intended for use with afterburning turbofan engines. A wide range of Reynolds number was obtained by flying the F106 over a range of altitude and by using 5 and 22% wind tunnel models of the F106. A contoured nozzle had a boattail drag as low as that of a longer circular arc nozzle over the Reynolds number range studied.

Wilcox, F. A.↗

NASA NTRS1971