Engineering topics

Fancher, M. F.

Publications and source records attributed to Fancher, M. F..

4 records

NASA NTRS1990

Detecting Boundary-Layer Transition In Cold Environments

Transition-detection study conducted in Langley 0.3-Meter Transonic Cryogenic Tunnel, using specialized hot-film system designed specifically for use in cryogenic wind tunnels. Quantitative transition-location data obtained at nearly cryogenic conditions, 360 degree R (200 K) represents first definitive transition Reynolds numbers obtained in cryogenic wind tunnel. Multichannel data-acquisition system processes data from 40 hot-film sensors by use of desktop computer. Concept enables on-line determination of boundary-layer transition in such cryogenic wind tunnels as National Transonic Facility.

Johnson, C. B.↗

NASA NTRS1987

Hot-film system for transition detection in cryogenic wind tunnels

It is well known that the determination of the location of boundary-layer transition is necessary for the correct interpretation of aerodynamic data in transonic wind tunnels. In the late 1970s the Douglas Aircraft Company developed a vapor deposition hot-film system for transition detection in cryogenic wind tunnels. Tests of the hot-films in a low-speed tunnel demonstrated the ability to obtain on-line transition data with an enhanced simultaneous hot-film data acquisition system. The equipment design and specifications are described.

Johnson, Charles B.↗

NASA NTRS1987

A transition detection study using a cryogenic hot film system in the Langley 0.3-meter transonic cryogenic tunnel

A transition detection study was conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT) using a specialized hot film system designed specifically for use in cryogenic wind tunnels. The quantitative transition location data obtained at near cryogenic conditions, 360 deg R (200K) represents the first definitive transition Reynolds numbers obtained in a cryogenic wind tunnel. The model was tested at both adiabatic and nonadiabatic wall conditions with a wall-to-total temperature ratio as low as 0.47. The test results indicated an improved technique for hot-film installation and a modified data acquisition system would allow the on-line determination of the location of boundary layer transition in cryogenic wind tunnels, such as the U.S. National Transonic Facility.

Johnson, C. B.↗

NASA NTRS1982

The need for an optical transition detection system in the NTF

Methods for transition detection were studied. The very high test and model costs necessitate testing of any new configuration over a range of Reynolds numbers for correlation with data obtained in conventional tunnels. The Reynolds number variations will be carried out at constant dynamic pressure, i.e., constant aeroelastic condition, by varying test temperature. Boundary layer transition cannot be expected to occur at the full scale location at significantly less than full-scale Reynolds numbers, and transition patterns will change with varying Reynolds number. Knowledge of the location of transition on model surfaces is essential for correct interpretation of drag data. The importance of transition, the limitations of artificial transition fixing, and their relation to the NTF are reviewed. The calculated minimum roughness height to instantaneously trip transition on a model transport wing over a range of Reynolds numbers of interest is shown in the NTF.

Fancher, M. F.↗