A hydrodynamic performance orientated CRP numerical design/analysis procedure is presented with a coupling approach. The proposed method couples a Lifting- Surface Method (LSM) applied to the CRP, with a steady RANS solver applied to the global flow-field, in order to account for the interactions between the two blade rows and the vehicle body. The LSM designs the CRP, and predicts the pressures, forces and moments of the CRP. The impact of the CRP on wake field is modelled by converting the pressure forces on blades to radial distributed body force inside the flow domain. And the steady RANS solver determines the total velocity and pressure. Then the effective wake is evaluated and provided to the LSM for next round of design and analysis. The iterative process between the LSM and the steady RANS solver is repeated until a converged result is achieved. Finally, an unsteady RANS solver is applied to compute the accurate CRP performance after making CRP geometry which matches to the converged effective wake. Numerical design and analysis are carried out for a set of CRP utilized for a high-speed underwater vehicle. Validations of results from the current numerical method with those measured in model tests are presented. The design example and its numerical validation results indicate that the numerical design/analysis procedure is capable of producing smooth CRP's blade geometries and predicting CRP's self-propulsion performance accurately.

1. INTRODUCTION

The contra-rotating propeller (CRP) is a combination propulsor in which the forward and aft propeller rotate in opposite directions. CRPs can provide higher efficiencies and are also torque balanced, which is important for vessels needing accurate attitude control. Therefore, CRPs have been widely applied as main thrusters in revolution-body-shape underwater vehicles, such as AUVs and torpedoes. And the design and analysis of the CRP behind the underwater vehicle is critical to the power, velocity, noise and vibration of the vehicle.

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