Experimental investigation of wall-pressure fluctuations on a fully appended submarine model at high Reynolds numbers

TL;DR

This study delivers a high-Reynolds-number experimental dataset of wall-pressure fluctuations on a fully appended SUBOFF submarine model, covering baseline straight-ahead, yaw/pitch maneuvers, and a novel vortex control baffle (VCB) device. Using advanced signal-processing—dynamic transfer-function correction for pinhole microphones and Wiener filtering for background noise—the work reveals that appendages are the dominant source of flow noise, with unstable horseshoe vortex dynamics at the sail-hull junction driving large localized fluctuations. The VCB experimentally validates a source-based flow-control approach, achieving a global reduction in $p'_{rms}$ (≈$35.16\%$ at the stern and ≈$14\%$ mid-body) by disrupting the coherent HSV at its origin, while maneuvers induce strong crossflow effects and non-monotonic spectral responses that challenge axisymmetric assumptions. Together, the dataset and VCB demonstration provide a critical benchmark for validating high-fidelity CFD/LES and guide design strategies for quieter, next-generation submarines.

Abstract

This paper addresses a critical gap in hydroacoustics through a systematic wind tunnel investigation of wall-pressure fluctuations on the fully appended DARPA SUBOFF model at operationally relevant Reynolds numbers ranging from $5.6 \times 10^{6}$ to $1.4 \times 10^{7}$. The experimental campaign encompasses baseline straight-ahead flow, complex maneuvering (yaw and pitch) conditions, and a first-of-its-kind assessment of a novel vortex control baffle (VCB). To ensure benchmark-quality spectral data, rigorous signal processing techniques were applied, specifically Wiener filtering for background noise suppression and dynamic transfer function correction for pinhole sensors. Key findings indicate that while spectral self-similarity holds across Reynolds numbers, the primary finding is the critical role of appendages in noise amplification. Unstable horseshoe vortex dynamics at the sail-hull junction drive localized pressure fluctuations of up to 300%, establishing this feature as a major coherent noise source. To address this, the study provides the pioneering experimental validation of the VCB. By physically suppressing horseshoe vortex formation at the sail-hull junction, the VCB achieves a global stabilization of the downstream flow, resulting in a significant 35% reduction in root-mean-square wall-pressure fluctuations at the stern and an approximately 14% reduction along the parallel mid-body. Furthermore, maneuvering conditions are shown to fundamentally reshape the pressure field, introducing substantial crossflow effects and non-monotonic spectral behaviors. This comprehensive dataset and the demonstrated efficacy of the VCB provide essential physical insights and a critical validation benchmark for the design of next-generation quiet submarines.

Figures (19)

• Figure 1: Schematic of the appended SUBOFF model experimental configuration: (a) Overall installation of the SUBOFF model in the high-speed test section of the Shanghai Jiao Tong University wind tunnel; (b) Detailed view of the geometrical information of the test model.
• Figure 2: Photographs illustrating the SUBOFF model with appendages installed in the wind tunnel test section: (a) View from upstream (looking downstream) showing the model's overall placement and the flow direction; (b) View from downstream (looking upstream) detailing the stern fins.
• Figure 3: Schematic of the arrangement of measurement points along the test model top meridian line. Square symbols denote wall-pressure fluctuation sensors.
• Figure 4: Mean pressure coefficient ($C_p$) distribution along the top meridian of the appended SUBOFF model at $Re = 1.2 \times 10^7$ (straight-ahead condition) compared with experimental data from Liu1998SUBOFFexp and WMLES from Jiang2025PoFSUBOFF.
• Figure 5: Power spectral density of wall-pressure fluctuations measured at sensor F4 (parallel mid-body, $x/L = 0.5$) on the fully-appended hull, shown for a range of Reynolds numbers ($Re$) under straight-ahead conditions.