Investigation of the Uncertainty of a Validation Experiment Due to Uncertainty in Its Boundary Conditions

Abstract

Elements contributing to uncertainty in experimental repeatability are quantified for data acqui- sition in a bank of cylinders. The cylinder bank resembles the lower plenum of a high temperature reactor with cylinders arranged on equilateral triangles with a pitch to diameter ratio of 1.7. The 3-D as-built geometry was measured by imaging reflections off the internal surfaces of the facility. This information is useful for building CFD grids for Validation studies. Time-averaged Particle Image Velocimetry (PIV) measurements were acquired daily over several months along with the pressure drop between two cylinders. The atmospheric pressure was measured along with the data set. The PIV data and pressure drop were correlated with atmospheric conditions and changes in experimental setup. It was found that atmospheric conditions play little role in the channel velocity, but impact the pressure drop significantly. The adjustments made to the experiment setup did not change the results. However, in some cases, the wake behind a cylinder was shifted significantly from one day to the next. These changes did not correlate with ambient pressure, room temperature, nor tear down/rebuilds of the facility.