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TECHNICAL PAPERS

# Statistical Approach for Estimating Intervals of Certification or Biases of Facilities or Measurement Systems Including Uncertainties

[+] Author and Article Information
F. Stern, J. Shao, J. Longo

IIHR Hydroscience and Engineering,  The University of Iowa, Iowa City, IA 52242

A. Olivieri

INSEAN, Italian Ship Model Basin, Rome, Italy

T. Ratcliffe

NSWC/CD, David Taylor Model Basin, Bethesda, MD

J. Fluids Eng 127(3), 604-610 (Feb 10, 2005) (7 pages) doi:10.1115/1.1906269 History: Received April 08, 2003; Revised February 10, 2005

## Abstract

A statistical approach for estimating intervals of certification or biases of facilities or measurement systems including uncertainties is set forth based on $M×N$-order level testing, which is defined as $M$ repetitions of the same $N$-order level experiment in $M$ different facilities or in the same facility with $M$ different measurement systems. In the absence of reference values, the mean facility or measurement system is used for assessing intervals of certification or biases. Certification or biases of facilities or measurement systems are defined as processes for assessing probabilistic confidence intervals for facilities or measurement systems for specific tests, data reduction equations, conditions, procedures, and uncertainty analysis. Similarly, subgroup analysis is performed for isolating and assessing levels of differences due to use of different model sizes (scale effects) or measurement systems. An example is provided for towing tank facilities for resistance tests using standard uncertainty analysis procedures based on an international collaboration between three facilities. Although the number of facilities are at a minimum, the results demonstrate the usefulness of an approach and support recommendation of future collaborations between more facilities. Knowledge of intervals of certification or biases is important for design, accrediting facilities or measurement systems, and CFD validation.

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## Figures

Figure 1

M×N-order level testing

Figure 2

Estimating intervals of certification or biases of facilities using mean as reference value: facility i certified at UDi and facility j with facility bias UFBj

Figure 3

Surface-combatant model ships (a) DTMB model 5415 (b) INSEAN model 2340A (c) IIHR model 5512

Figure 4

Individual facility residuary resistance results and mean facility residuary resistance and individual facility uncertainty bands at Fr=0.1, 0.28, and 0.41.

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