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Abstract:
Propeller operation in crashback is technically very challenging, both computationally and experimentally. Propeller 4381 was evaluated experimentally in Carderock's 36-inch (0.91 m) water tunnel. Propeller 4381 was operated in the ahead condition for comparison. Details of the flow field were measured with 3-component laser Doppler velocimetry (LDV) and 2-component particle imaging velocimetry (PIV). Propulsion performance was measured with thrust and torque transducers. Cavitation was documented photographically with a strobe light, and flow visualization was conducted with a vertical laser light sheet for observation of the recirculation region of the propeller in crashback. Results showed that highly random cavitation occurred on the propeller in crashback on the downstream side at the leading edge, which is the trailing edge for ahead. A highly unstable recirculation zone occurred with a ring vortex near the propeller tip. The maximum variation in thrust and torque as computed from the standard deviation relative to the mean load with a value of 0.25 occurred at an advance ratio of J = -0.5. The high variation in loads appeared to correlate with the maximum total kinetic energy relative to tunnel velocity in the flow at the blade tip, which was measured by LDV as 1.5. These results indicate that vibration and wear may be reduced by minimizing operation near J = - 0.5 for this propeller.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Final rept. |
| Pages: |
62 |
| Report Date: |
DEC 2004 |
| Report Number: |
A989924 |
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