Research Papers: Flows in Complex Systems

Combined Experimental/Numerical Development of Propulsor Evaluation Capability

[+] Author and Article Information
Amanda M. Dropkin

 Naval Undersea Warfare Center, Code 8233, Building 1302/2, Newport, RI 02841Amanda.Dropkin@navy.mil

Stephen A. Huyer, Charles Henoch

 Naval Undersea Warfare Center, Code 8233, Building 1302/2, Newport, RI 02841

J. Fluids Eng 133(8), 081105 (Sep 02, 2011) (9 pages) doi:10.1115/1.4004387 History: Received September 03, 2010; Revised May 06, 2011; Published September 02, 2011; Online September 02, 2011

This paper presents a method to combine computational fluid dynamics (CFD) modeling with subscale experiments to improve full-scale propulsor performance prediction. Laboratory experiments were conducted on subscale models of the NUWC Light underwater vehicle in the 0.3048 m × 0.3048 m water tunnel located at the Naval Undersea Warfare Center in Newport, Rhode Island. This model included an operational rim-driven ducted post-swirl propulsor. Laser Doppler Velocimetry was used to measure several velocity profiles along the hull. The experimental data were used in this project to validate the CFD models constructed using the commercial CFD software package, Fluent® . Initially, axisymmetric two-dimensional simulations investigated the bare hull, hull only case, and a shrouded body without the propulsor. These models were selected to understand the axisymmetric flow development and investigate methods to best match the propulsor inflow. A variety of turbulence models were investigated and ultimately the numerical and experimental velocity profiles were found to match within 3%. Full 3D flow simulations were then conducted with an operating propulsor and compared with the corresponding subscale experimental data. Finally, simulations were conducted for full-scale tests and compared with actual open-water data. While the open-water data was limited to propulsor rpm and vehicle velocity, the operating advance ratio could be determined as well as the estimated vehicle thrust. This provided a method to utilize CFD/experiments to bridge the gap between subscale and full-scale tests. The predicted open-water advance ratio was 10.3% higher than the experimental value, as compared with the 28% difference previously found from a linear extrapolation of Reynolds number from model scale to full scale. This method was then applied to two different research propulsor geometries and led to agreement between computational and experimental advance ratios on the order of 2%.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Typical axisymmetric 2D Fluent® mesh generated using Gambit® highlighting the water tunnel model mesh

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Figure 2

Typical 3D Fluent® mesh generated using Gambit® highlighting the periodic meshes for the rotor (top) and stator (bottom) as well as highlighting the boundary layers on the hull, duct, and (rotor) blade

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Figure 3

NUWC 12" water tunnel

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Figure 4

Test model hardware of the afterbody section and rotor and stator blade rows

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Figure 5

LDV data collection locations

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Figure 6

Bare hull drag for a range of grid resolutions

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Figure 7

Axial boundary layer velocity profiles taken at the mid-body (XL-1) and afterbody region (XL-2) at freestream velocities of 2, 4 and 8 m/s comparing Fluent® solutions and experimental data

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Figure 8

TKE boundary layer profiles for the same conditions listed in Fig. 7

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Figure 9

Bare hull drag data in N for the water tunnel velocities examined

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Figure 10

Mesh of pedestal geometry

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Figure 11

Velocity profile comparison for NUWC-light geometry with operational propulsor

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Figure 12

Profile of the force produced by the subscale water tunnel numerical model at varying advance ratios

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Figure 13

Comparison of numerical and experimental propulsor reynolds numbers at self propulsion

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Figure 14

Bare hull and shrouded drag data for the Baseline and Duct 12 geometries

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Figure 15

Axial velocity profiles for the Baseline geometry



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