Self-propulsion Characteristics Research Articles

Self-propulsion characteristics of fish-like undulating foil – a numerical investigation

ABSTRACT In this work, the propulsive characteristic of an auto-propelled 2D NACA0015 foil undergoing traveling wave motion is numerically investigated. The effects of typical motion parameters, i.e. traveling amplitude, traveling frequency (f), and geometric parameters (thickness, d) on the propulsive property of auto-propelled foil are systematically investigated. The numerical results reveal that the moving velocity of foil can be significantly enhanced by the enlargement of the traveling amplitude and traveling frequency, while it presents a sharp decrease when the foil thickness increases. As for the propulsive efficiency, the effects of a 1, f and d on the magnitude of η are similar to each other, that is, the magnitude of η will ascend to the peak value and then decrease, and there exists an optimum value corresponding to the highest magnitude of η. The flow structures in the wake of the auto-propelled foil under typical calculation conditions are also analysed.

Powering performance prediction of a semi-displacement ship retrofitted with Hull Vane

This study predicts the powering performance of a semi-displacement ship, both without and with a Hull Vane (HV). HV is an energy-saving appendage fixed at the transom bottom of the ship's hull. Although the HV is commercially known as a successful resistance-reducing device, there are no studies in the literature examining its effect on propulsion performance in detail. In this study, the effect of the HV on the propulsion performance is investigated and a practical method is proposed as an engineering application to reduce the computation time. Initially, the idealized disc model based on Blade Element Theory (BET) is preferred to create a thrust force instead of using an entire physical propeller. The dynamic motions of the ship are reflected in the computational analysis. Subsequently, the sliding mesh technique, which models the exact propeller geometry, is implemented to calculate the self-propulsion characteristics without and with HV. These computations are achieved by employing a two-phase flow solver available in OpenFOAM. This study provides a significant demonstration to clarify the effect of HV on powering performance. It not only decreases effective power by 11.41% but also increases the propulsive efficiency by 2.1%, which reduces the brake power by 14.61% in total at service speed.

Partially rotating grid method for self-propulsion calculations with a double body ship model

In this paper, partially rotating grid method for predicting self-propulsion characteristics using a double body ship model approach is presented. Partially rotating grid method combines a full-discretized temporal-domain rotating propeller approach with locally introduced non-inertial equation system to reduce overall computation time. Verification and validation of the method are performed in this paper. Numerical self-propulsion simulations are conducted for a single-screw KRISO container ship both in model and full-scale. Obtained results are analyzed in terms of integral (propulsion factors) and local (velocity field) flow characteristics with a focus on ship-propeller interaction and scale effects. To better understand propeller performance and ship-propeller interaction effects, variation of a single blade KT, KQ, and KT/KQ values during one period of rotation are analyzed. The introduced partially rotating grid method proved to accurately predict the integral and local flow characteristics while reducing overall computation time, at cost of reduced accuracy.

Numerical analysis of self-propulsion flow characteristics in model scale

In this paper, a detailed numerical analysis of global, and local flow characteristics of a self-propelled KCS model is presented. Global flow characteristics are integral values such as thrust and torque, while the local flow characteristics are represented by the velocity components. Three different numerical propeller representations are considered: fully discretized propeller, actuator disc model which models the thrust effect on the fluid flow only, and actuator disc model that models both thrust and torque effects. Verification is performed using method based on Richardson extrapolation, and the approach is validated with publicly available experimental data, both for global and local flow characteristics. A procedure for accurate prediction of global and local self-propulsion characteristics using a combination of actuator disc and discretized propeller methods is presented. The hybrid procedure was proved to provide a good agreement of global flow characteristics with experimental data. The fully discretized propeller model using overset grid showed good accuracy of predicting local flow characteristics, observed by comparing axial and in-plane velocity components behind the working propeller.

The hydrodynamic performance analysis of a submarine with new pump-jet propulsor

A new type of pump-jet propulsor (PJP) was designed and installed on the DARPA Suboff. The installation position of this new PJP is different from the traditional PJP, which gives more possibilities to improve the comprehensive performance of submarine. The duct of PJP has been automatically modeled based on pumped rotor, stator and hull shape. The rotor of PJP has been modeled as an actuator disc based on body force method coupled with the experimental open water data. The hydrodynamic performance analysis was applied on the self-propulsion point, and the self-propulsion characteristics were estimated by the thrust identity method. Moreover, the pressure and velocity distribution for different duct geometric parameters have been compared and discussed. The results indicate that the size of the duct has an impact on the generation of negative pressure zone and the wake distribution. When the geometric parameters of duct are equal to r = 0.75R, L = 3.5D and H = 0.8D, the overall performance is superior. The new pump jet destroys the circumferential correlation of the duct vortex and accelerates the dissipation of the vortex.

Effect of biofouling roughness on the full-scale powering performance of a submarine

The aim of this study is to investigate the impact of barnacle type biofouling roughness on the full-scale powering performance of a submarine in calm seas. The importance of the diversified biofouling accumulations in terms of hull location is also examined over the submarine hull by implementing homogeneous and heterogenous roughness distribution. In this study, a Reynolds Averaged Navier Stokes (RANS) based CFD model was used for predicting the effects of biofouling roughness on the self-propulsion characteristics for the full-scale submarine form. The powering performance analyses are performed with discretised propeller geometry, and the Moving Reference Frame approach is used to model the rotational motion of the propeller. A proportional-integral (PI) approach is adopted to obtain the self-propulsion point efficiently by modifying the propeller's rotational speed. First, the resistance and the self-propulsion characteristics of the model scale submarine are validated with the experimental and other numerical studies in the literature. Following this validation task, a roughness function model is employed within a CFD software's wall function to represent the rough surfaces over the submarine hull. The results showed that although roughness has a varying effect on the submarine's self-propulsion characteristics depending on the roughness distribution, it increases the hull resistance and, hence, the delivered power overall. Roughness on the forward section of the hull has a more pronounced effect on the resistance and delivered power. The study demonstrated that the presence of partial hull fouling should not be ignored, and required precautions should be taken to prevent losses in submarine performance, especially for the fouling at the forward section of the submarine.

An investigation of scale effects on the self-propulsion characteristics of a submarine

This study's main objective is to investigate the scale effect on the benchmark DARPA Suboff submarine hull form's resistance and self-propulsion characteristics. The study's secondary objective is to explore the feasibility of the 1978 ITTC performance prediction method for submarines' power prediction. In achieving both objectives, the CFD solver is utilised. Hence, the flow around the three different scales of the DARPA submarine forms and its propellers, including a full-scale one, is first solved using the steady RANS method with the k-ω SST turbulence model. Verification studies are conducted to determine the uncertainty level of the numerical computations for each scale. The hull resistance, propeller open water and self-propulsion performances are validated with the available experimental data and other numerical studies in the literature for the widely used benchmark submarine model. In the self-propulsion simulations, the propeller flow is modelled using the discretised propeller geometry with the Moving Reference Frame (MRF) approach. Also, the Proportional Integral (PI) controller is adopted to find the self-propulsion point efficiently. The scale effects on the hull resistance and its components, nominal wake fraction and self-propulsion characteristics, are explored at two different velocities. The extrapolated numerical results obtained by the 1978 ITTC procedure show that the scale ratio decrease enables better prediction of the self-propulsion characteristics compared to the full-scale CFD predictions. As well as this, the extrapolated self-propulsion characteristics using the model scale results, which are obtained by the CFD computations, are found to be in good agreement with those of the full-scale CFD results. The study, therefore, suggests that the 1978 ITTC performance prediction method can be used in some confidence to extrapolate the performance results from the model to full-scale for the submerged bodies, similar to the surface ships. This study also presents the full-scale self-propulsion characteristics of the benchmark DARPA Suboff form for the first time in the literature using the CFD tool over a realistic range of submarine forward speeds.

Prediction of Resistance and Self-Propulsion Characteristics of a Full-Scale Naval Ship by CFD-Based GEOSIM Method

Resistance and self-propulsion characteristics of a naval ship at full scale have been investigated by using Telfer’s GEOmetrically SIMilar (GEOSIM) method based on the computational fluid dynamics (CFD) approach. For this purpose, first, the resistance forces of the Office of Naval Research Tumblehome (ONRT) hull have been computed at different three model scales by using the overset mesh technique. The full-scale resistance and nominal wake fraction of the ONRT hull have been estimated by using Telfer’s GEOSIM method. Resistance and nominal wake fraction have then been compared with those of CFD at full scale. Later, the self-propulsion characteristics of the ONRT hull have been examined using Telfer’s GEOSIM method based on the CFD approach. Self-propulsion factors at the full-scale hull have been predicted by using the SST k–x turbulence model to involve 2-degrees of freedom ship motions (heave and pitch). Rotational motion of the propeller has also been simulated by using the rigid body motion technique. The results calculated by Telfer’s GEOSIM method and the 1978 International Towing Tank Conference (ITTC) extrapolation technique have been compared with each other and discussed with those of the CFD approach at full scale. It was found that the full-scale results (both resistance and self-propulsion factors) predicted by Telfer’s GEOSIM method are closer to those of the CFD approach than those of the 1978 ITTC technique. It can be noted that Telfer’s GEOSIM method is fast, robust, and reliable and can be used as an alternative to the 1978 ITTC method for predicting the self-propulsion performance of a full-scale ship. Introduction Resistance and self-propulsion characteristics of a surface ship should be known properly in the design stages. For this purpose, model tests and numerical methods are used together to determine the resistance and self-propulsion performance of a ship. However, model tests are expensive and time-consuming, and the accuracy of the International Towing Tank Conference (ITTC) extrapolation technique from model scale to full scale may not have in a satisfactory level. On the other hand, Telfer’s GEOmetrically SIMilar (GEOSIM) method based on computational fluid dynamics (CFD) can overcome these difficulties.

Effective wake estimation of KCS hull at full-scale by GEOSIM method based on CFD

In this study, the effective wake factors of a self-propelled container ship were investigated by Telfer's GEOSIM method based on CFD (Computational Fluid Dynamics). For this purpose, the self-propulsion characteristics of KCS (KRISO Container Ship) at three different model scales and full-scale were determined at Fr = 0.26 by unsteady RANS (Reynolds Averaged Navier-Stokes) solver. All scales corresponded to a wide range of Reynolds numbers. Turbulent flow around the KCS hull has been investigated by the k-ε turbulence model. Heave and pitch motions of KCS hulls have been modeled with the DFBI (Dynamic Fluid Body Interaction) method and overset mesh technique. The rotational motion of KP505 propeller has been simulated using the RBM (Rigid Body Motion) approach. The result obtained by the extrapolation of the effective wake fraction with the GEOSIM method was compared with the full-scale ones of CFD and ITTC methods. The results by the GEOSIM method are more compatible with those of full-scale CFD than the results of 1978 ITTC method. In the wake region, where viscous effects are predominant, the change of effective wake fraction with Reynolds number has been successfully represented by the GEOSIM method, thus more robust and reliable results have been found.

Experimental and Numerical Investigation of DARPA Suboff Submarine Propelled with INSEAN E1619 Propeller for Self-Propulsion

The Defense Advanced Research Projects Agency (DARPA) Suboff Submarine propelled by the Italian Ship Model Basin (INSEAN) E1619 propeller is extensively used in submarine validation studies. Although there are several numerical studies where the DARPA Suboff submarine is used in combination with E1619 propeller there are no experimental data available in open literature for the self-propulsion condition. In this article, the self-propulsion characteristics of the DARPA Suboff submarine model with INSEAN E1619 propeller obtained with experimental and numerical methods are presented and discussed by means of Taylor wake fraction, thrust deduction, hull efficiency, relative rotative efficiency, and propulsive efficiency. To experimentally investigate the submarine form, a self-propulsion experimental setup is designed and manufactured. Resistance and self-propulsion experiments are conducted in Istanbul Technical University Ata Nutku Ship Model Testing Laboratory. Resistance tests are carried out for three different speeds, and the results show good agreement with the published experimental results. Propulsion tests are conducted by using the load-varying self-propulsion test method for constant speed and seven different propeller rotation rates. Rotational speed, thrust, and torque forces at self-propulsion point are investigated. For the numerical computations a commercial Computational Fluid Dynamics (CFD) code is used. Propeller open water characteristics and nondimensional velocities behind the propeller are calculated. Self-propulsion point of the submarine and propeller assembly is also solved numerically and the results are compared with the results obtained from the experiments, and it is seen that especially the propeller rate of revolution and thrust force are predicted with very good approximation.

Penalty of hull and propeller fouling on ship self-propulsion performance

Recently, there has been an increasing interest in predicting the effect of biofouling on ship resistance using Computational Fluid Dynamics (CFD). For a better understanding of the impact of biofouling on the fuel consumption and green-house gas emissions of ships, studying the effect of biofouling on ship self-propulsion characteristics is required. In this study, an Unsteady Reynolds Averaged Navier–Stokes (URANS) based full-scale ship self-propulsion model was developed to predict the effect of biofouling on the self-propulsion characteristics of the full-scale KRISO container ship (KCS). A roughness function model was employed in the wall-function of the CFD model to represent the barnacles on the hull, rudder and propeller surfaces. A proportional-integral (PI) controller was embedded in the simulation model to find the self-propulsion point. Simulations were conducted in various configurations of the hull and/or propeller fouling. Finally, the effect of biofouling on the self-propulsion characteristics have been investigated.

Investigation of self-propulsion of DARPA Suboff by RANS method

In this study, the resistance and self-propulsion analyses of the benchmark DARPA Suboff with E1619 propeller have been done using Computational Fluid Dynamics (CFD) method. Single phase analyses have been carried out by assuming 3-D, turbulent, incompressible and steady flow, thus the governing equations (RANS Equations) have been discretized with finite volume method (FVM). First, verification and validation studies have been carried out in order to determine the optimum grid numbers for resistance analyses of bare and appended forms, and then for open water propeller analyses. The numerical studies have been done by taking the propeller-hull interaction into consideration by two methods for different velocities. First, the propeller has been modeled as an actuator disc based on body force method coupled with the experimental open water data. The propeller itself has later been modeled behind the hull with a rotating region. Performance analyses have been carried out at the self-propulsion points determined by these two methods. Self-propulsion characteristics have been estimated using thrust identity method. Finally, a comprehensive investigation of wake has been carried out by comparing the present results with those of other studies and the applicability of CFD on self-propulsion prediction of the underwater vehicles has been discussed.

Mechanism of self-propulsion in 3D-printed active granular particles

Active granular particles can harness unbiased mechanical vibrations in the environment to generate directed motion. We provide a theoretical framework that connects the geometrical shape of a three dimensional object to its self-propulsion characteristics over a vertically vibrated plate. We find that a maximally efficient propulsion is achieved for structures having tilted flexible legs forming a characteristic angle with the vertical. Our predictions are verified by experimental observations on a class of 3D printed structures with smoothly varying geometrical features.

Estimation of Resistance and Self-Propulsion Characteristics for Low L/B Twin-Skeg Container Ship by a High-Fidelity RANS Solver

Reynolds-averaged Navier-Stokes simulations together with verification and validation studies for a low L/B twin-skeg container ship are carried out using SURF version 6.44, which is a high-fidelity RANS solver for ship hydrodynamics developed at the National Maritime Research Institute: single-phase level set free surface, Spalart-Allmaras/k-co turbulence, and body-force propeller models; finite volume discretization; and parallelized by openMPW for high-performance computing. At the beginning, simulation numerical uncertainty has been quantified for resistance and self-propulsion coefficients on the basis of the standard V&V procedure recommended by the International Towing Tank Conference. Then the resistance and self-propulsion simulations are carried out at several speeds ranging from low to medium Froude numbers. The overall results are encouraging in that the solver accurately predicts resistance and self-propulsion coefficients as well as velocity distribution at the propeller plane in comparison to the available experimental data. Further sophistications in computational method, especially in estimating self-propulsion coefficients, will lead the solver to be more practical and powerful design tool.

Estimation of Resistance and Self-Propulsion Characteristics for Low L/B Twin-Skeg Container Ship by a High-Fidelity RANS Solver

Reynolds-averaged Navier-Stokes (RANS) simulations together with verification and validation studies for a low L/B twin-skeg container ship are carried out using SURF version 6.44, which is a high-fidelity RANS solver for ship hydrodynamics developed at the National Maritime Research Institute: single-phase level set free surface, Spalart-Allmaras/k-ω turbulence, and body-force propeller models; finite volume discretization; and parallelized by open MP® for high-performance computing. At the beginning, simulation numerical uncertainty has been quantified for resistance and self-propulsion coefficients on the basis of the standard V&V procedure recommended by the International Towing Tank Conference. Then the resistance and self-propulsion simulations are carried out at several speeds ranging from low to medium Froude numbers. The overall results are encouraging in that the solver accurately predicts resistance and self-propulsion coefficients as well as velocity distribution at the propeller plane in comparison to the available experimental data. Further sophistications in computational method, especially in estimating self-propulsion coefficients, will lead the solver to be more practical and powerful design tool.

CALCULATION OF PROPULSION CHARACTERISTICS OF A TANKER USING DIFFERENT PROPELLER MODELS

A viscous solver is applied to calculate the propulsion parameters of a tanker moving at a low Froude number. The propeller is represented by either a simplified actuator disk or a lifting line model and different approaches are followed to calculate the effective wake fraction and the required DHP. The sensitivity of obtained results is examined with respect to various approximations that are made to calculate the self-propulsion characteristics.