Effects of the Duct Angle and Propeller Location on the Hydrodynamic Characteristics of the Ducted Propeller

Abstract

In the present study, the effect of the duct angle and propeller location on the hydrodynamic characteristics of the ducted propeller using Reynolds-Averaged Navier Stokes (RANS) method is reported. A Kaplan type propeller is selected with a 19A duct. The ducted propeller is analyzed by three turbulence models including the k-ε standard, k-ω SST and Reynolds stress model (RSM). The numerical results are compared with experimental data. The effects of the duct angle and the location of the propeller inside the propeller are presented and discussed.En el presente estudio se reporta el efecto del ángulo de ducto y la ubicación de la hélice sobre las características hidrodinámicas de la hélice con ducto, usando el método RANS (Reynolds-Average Navier Stokes). Una hélice de tipo Kaplan es seleccionada con un ducto tipo 19A. La hélice con ducto es analizada por tres modelos de turbulencia, incluyendo k-ε standard, k-ω SST y el modelo de esfuerzo de Reynolds (RSM -Reynolds Stress Model). Los resultados numéricos son comparados con datos experimentales. El efecto del ángulo de ducto y la ubicación de la hélice son presentados y discutidos. 42In recent year, considerable eff orts have been made to improve the propulsive effi ciency of the propeller on the ships. One of these propulsors is called a ducted propeller found as widespread application. Th e duct is generally used to obtain augment thrust, but it is also used to minimize cavitation and underwater noise or to protect the propeller from damage. Th ere are two types of duct, the fi rst type is called an acceleration duct or Kort nozzle and the second type is a deceleration duct. Fig. 1 shows both types of the ducted propeller. Th e Acceleration duct has a fl at surface on the outside of the curve in the inner area. Th e outer surface is high-pressure surface and the inner surface is low-pressure surface (or suction). Th e suction allows more current to be directed into the duct and thus increase the fl ow rate. Th e increased infl ow velocity causes a decrease in the thrust and torque of the propeller. At the same time, a circulation develops around the duct section resulting in an inward directed force which has a forward component, the duct thrust. Th e duct also has a drag directed aft. Th e effi ciency of the ducted propeller is therefore greater than of the open propeller (Ghose, Kogarn, 2004).In recent years, computational fl uid dynamics (CFD) have been extensively used for the analysis of marine propellers. Due to the complex shape, fl ow turbulence, fl ow separation and the possibility of cavitation, the analysis of marine propellers is a diffi cult task; however, some works have been done in the fi eld of ducted propellers. For example, (Taketani et al., 2009) presented the advanced design method of a ducted propeller which has high bollard pull performance. A nozzle section shape and a propeller have been designed according to a parametric study of the numerical simulation in order to have higher performance than a conventional ducted propeller. Th e o...

Obtaining mathematical functions of the propeller thrust and torque coefficients fluctuations at non-uniform wake flow including geometry effects

“…During recent years, Ghassemi et al worked on the different propulsor (poded propeller, ducted propeller, surface propeller and propeller with augmentation devices) numerical analysis by BEM and CFD [23][24][25], ship hullpropeller interaction [26], calculations of the sound pressure level of the marine propeller in low frequency [27], hydrodynamic characteristics of the ducted propeller and its different geometries effect [28] as well as the propeller efficiency enhancement of the blade's tip reformation [29]. Based on cited works, mathematical functions of the nonuniform wake flow entered to the propeller geometries is not well known.…”

Propeller Efficiency Enhancement by the Blade's Tip Reformation

“…They obtained possible stress locations on propeller blade working in optimized condition. Hydrodynamic characteristics of the Kort-Nozzle simulated by using different turbulence models and in order to evaluate the propulsive performance of the Kort-nozzle propeller, a Reynolds-Averaged Navier-Stokes (RANS) solver is employed [13].…”