| Popis: |
The 24th International Towing Tank Conference (ITTC) has initiated an inter-laboratory test of a 5.720 m length model that is geometrically similar to David Taylor Model Basin (DTMB) model 5415, a pre-design version of the U. S. Navy surface ship combatant DDG-51. Resistance, sinkage, and trim measurements were completed during the last week of August 2009 on DTMB Carriage #1. Test results include an uncertainty analysis. Since the test program was initiated, the uncertainty analysis procedures were revised by the 25th ITTC for consistency with the ISO Guide to the Expression of Uncertainty in Measurement (ISO GUM 1995). This paper describes the analysis by the ISO GUM. All measurement results are traceable to NIST (National Institute of Standards and Technology). These results are for a test conducted on a single day over a Froude number, Fr, range of 0.10 to 0.41 and 9 different velocities. Only resistance results are reported here. A total of 12 repeat runs were performed at Fr = 0.10, 0.28, and 0.41. The variation in results is quite large in comparison to the uncertainty estimate at a single run condition. The uncertainty from Type A method as computed from the standard deviation of the time series was the largest uncertainty component in resistance from the drag block gages. For example at Fr = 0.41, the residuary resistance coefficient was CR = 0.003721 ±0.000041 (±1.11 %) with about ±0.000031 (±0.83 %) from the block gage measurement. A 4th-order polynomial approximates the experimental data quite well with a correlation of coefficient of 0.999. The fitted value at Fr = 0.41 is CR = 0.00366 ±0.00012 (±3.3 %). The curve fitted value is considered to be the best estimate of the uncertainty when combined with the measured value. For the most part, the resistance coefficients are in agreement with previous results within the uncertainty of the estimates. |
