Technical report | Benchmarking the AMC Cavitation Tunnel for Hydrodynamic Measurements on Submarine Models with CFD Determined Blockage Corrections

Abstract

The widely studied generic submarine hull form SUBOFF was used to benchmark the use of the Australian Maritime College's (AMC) cavitation tunnel for hydrodynamic measurements on submarine models. The measurements acquired at the AMC cavitation tunnel are a subset of those taken at the David Taylor Research Centre (DTRC), allowing direct comparison. The measurements were performed on a 1.54 m model for Reynolds numbers between 8 and 18 million. The measurements included surface pressure, skin friction, boundary layer velocities and a wake survey on the bare hull at zero degrees incidence. The large scale of the model relative to the tunnel resulted in a blockage ratio of 8.1%. The results were corrected using correction factors determined from Computational Fluid Dynamics (CFD) simulations, and displayed a high level of agreement with the DTRC results. The positive comparison showed that the AMC facility could be used for models of this size when combined with CFD based blockage corrections.

Executive Summary

The generic submarine hull form SUBOFF was used to benchmark submarine model testing in the Australian Maritime College’s (AMC) cavitation tunnel. For this series of measurements only the bare hull with and without the aft control surfaces was used.

The cavitation tunnel’s test section is 2.6 m long, with a 600 x 600 mm cross section. It can operate with flow speeds of between 2 and 12 m/s. The model was held at a constant zero degrees incidence for the duration of these measurements. The 180 mm diameter model and support foils resulted in a solid blockage ratio of 8.1%.

Measurements taken included the surface pressure and skin friction on the bare hull at a range of Reynolds numbers between 8 and 18 million. Boundary layer velocity profiles were calculated from total and static pressure probe measurements obtained using a 3D traverse at a number of locations around the aft of the bare model for a Reynolds number of 12 million. The unsteady velocity component was also calculated to obtain the turbulence intensity at these locations. Wake velocity measurements were obtained at the aft of both the bare hull and the partially appended model.

The relatively high blockage ratio necessitated a correction method to allow comparisons with measurements made at other facilities. These corrections were generated with the aid of Computational Fluid Dynamics (CFD) simulations.

The corrected measurements showed good agreement with results obtained at the David Taylor Research Centre’s (DTRC) Anechoic Flow Facility. DTRC measurements  were made with a smaller solid blockage ratio (3.5%). In general the results showed that measurements in the cavitation tunnel, with blockage corrections, are accurate and reliable for this scale of model. The wake survey results did show a small discrepancy which may warrant further investigation.

This work was conducted as part of the SEA 1000 Submerged Wakes and Propeller Hydrodynamics work package (PRP.3, deliverable 8 and HYD.8, deliverable 2).