Pengfei Liu - Academia.edu (original) (raw)

Papers by Pengfei Liu

23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 1, Parts A and B, 2004

To provide information on the wake characteristics of Dynamic Positioning (DP) thrusters when ope... more To provide information on the wake characteristics of Dynamic Positioning (DP) thrusters when operating with and without a nozzle under varied operating conditions, experiments were done on a ducted propeller model in a cavitation tunnel. The propeller flow field was measured ...

Journal of Offshore Mechanics and Arctic Engineering, 2005

To provide experimental data on the hydrodynamic characteristics and features of dynamic position... more To provide experimental data on the hydrodynamic characteristics and features of dynamic positioning (DP) thrusters under variable operating conditions, wake measurements were performed on a DP thruster model using 2D laser Doppler velocimetry (LDV) and stereoscopic particle image velocimetry (SPIV). These tests were performed with and without a nozzle and over a range of advance coefficient values including the bollard pull condition. In this paper, a detailed analysis of the hydrodynamic characteristics of the wake at a plane equal to a distance of 0.5 diameters downstream from the thruster, at advance coefficient values of 0, 0.4, and 0.45 are presented for both the LDV and SPIV measurements showing a comparison between the results of each technique. The effect of the duct and of changes in the advance coefficient values is presented in this paper.

The knowledge of the effects of the wakes from Dynamic Positioning (DP) thrusters and the practic... more The knowledge of the effects of the wakes from Dynamic Positioning (DP) thrusters and the practical need to describe and predict their impact is fundamental in the assessment of design loading on slipstream-submerged equipment associated with offshore floating systems. In particular, with the increasing importance and application of DP thrusters in the offshore industry, the designer as well as the operator must have more information about the momentum in the wake from the thruster. This paper presents wake measurements from cavitation tunnel tests carried out on a ducted propeller model at the Italian Ship Model Basin (INSEAN), Rome, Italy. Through these experiments, DP thruster wake velocity components at different downstream axial planes were obtained experimentally using a Stereo Particle Image Velocimetry (SPIV) system in the INSEAN cavitation tunnel, up to 15 diameters downstream. These experiments were carried out with and without the nozzle in the bollard pull condition. Thi...

… & Expo and Ship …, 2010

This paper presents results and analyses of an experimental study into the effects of geometric p... more This paper presents results and analyses of an experimental study into the effects of geometric parameters on the propulsive characteristics of puller and pusher podded propulsors in straight course open water conditions. Five geometric parameters were chosen for the current ...

International shipbuilding progress, 2001

This paper first describes procedures and methodologies to automatically produce marine propeller... more This paper first describes procedures and methodologies to automatically produce marine propeller geometry with optional auxiliary bodies such as nozzles, blockages and rudders. This process is designed and implemented for a general boundary element method (the panel method) ...

Journal of Naval Architecture and Marine Engineering

This paper describes the numerical aspects of a research program on podded propulsors, which is b... more This paper describes the numerical aspects of a research program on podded propulsors, which is being undertaken jointly by the Ocean Engineering

International shipbuilding progress, 2012

This paper presents results and analyses of an experimental study into the effects of static and ... more This paper presents results and analyses of an experimental study into the effects of static and dynamic azimuthing conditions on the propulsive characteristics of a puller podded unit in open water. The model propulsor was instrumented to measure thrust and torque of the propeller, three orthogonal forces and moments on the unit, rotational speed of the propeller, azimuthing angle and azimuthing rate. The model was first tested over a range of advance coefficients at various static azimuthing angles in the range of-180° to 180°. These tests were followed by tests in which the azimuthing angle was varied dynamically at certain azimuthing rate and propeller rotational speed. A comparative study of the performance coefficients at static and dynamic azimuthing conditions in the range of-180° to 180° is presented. The performance coefficients of the propeller and the pod unit showed a strong dependence on the propeller loading and azimuthing angle. The coefficients in static azimuthing ...

International Journal of Maritime Engineering, 2013

This paper presents the outcome of a research to evaluate the effect of size on the propulsive pe... more This paper presents the outcome of a research to evaluate the effect of size on the propulsive performance of podded propulsors in cavitating and non-cavitating open water conditions. Two cases are examined, namely: propeller-only case and pod-unit case. In the propeller-only case, a commercial propeller dynamometer is used to measure the thrust and torque of two propellers of different size at the four quadrants of propellers with varied shaft and flow speeds. Also, both propellers are tested at different tunnel pressure to study and compare the behaviour under similar cavitation conditions. In the pod-unit case, two geometrically similar but different sized pod-units are tested using two separate custom-made pod dynamometer systems in two towing tank facilities in straight-ahead and static azimuthing conditions. The study showed that the performance characteristics stabilize at lower Reynolds Number for the smaller propeller than the larger propeller. The propulsive performance of...

Marine Technology and SNAME News, 2006

Presently, the majority of podded propulsion systems are of the pulling type, because this type p... more Presently, the majority of podded propulsion systems are of the pulling type, because this type provides better hydrodynamic efficiency than the pushing type. There are several possible explanations for the better overall performance of a puller-type podded propulsor. One is related to the difference in hub taper angle. Puller and pusher propellers have opposite hub taper angles, hence different hub and blade root shape. These differences cause changes in the flow condition and possibly influence the overall performance. The current study focuses on the variation in performance of pusher and puller propellers with the same design of blade sections, but different hub taper angles. A hyperboloidal low-order source-doublet steady/unsteady time domain panel method code, PROPELLA, was modified and used to evaluate effects of hub taper angle on the open water propulsive performance of some fixed-pitch screw propellers used in podded propulsion systems. Major findings include good agreemen...

Applied Ocean Research, 2015

Experimental model tests were conducted to predict the performance of two sets of metal and plast... more Experimental model tests were conducted to predict the performance of two sets of metal and plastic bi-directional tidal turbine rotors. This test program aims to provide reliable and accurate measurement data as references for developers, designers and researchers on both model and full scale. The data set presented in this paper makes available the detailed geometry and motion parameters that are valuable for numerical tools validation. A rotor testing apparatus that was built using an off-the-shelf K&R propeller dynamometer, its configuration, testing setup , calibration of the apparatus and data acquisition are described. Comparison analysis between the metal and plastic rotors hydrodynamic performance in terms of torque, drag and derived power and drag coefficients are also presented. The results show a substantial decrease in maximum power performance for the plastic ro

Model experiments were used to evaluate CFD simulations of a high-speed planning vessel. Fluent (... more Model experiments were used to evaluate CFD simulations of a high-speed planning vessel. Fluent (v5.3) was used to simulate the flow around a planing vessel at steady speed through calm water using 3D unstructured hybrid grids with hanging node refinement. Force and moment data from the simulations were used in an iterative scheme to determine the dynamic equilibrium position of the model at selected speeds. The numerical results are compared with experimental data from model tests. The strengths and weaknesses of the numerical approach are discussed.

Volume 4: Materials Technology; Ocean Engineering, 2007

Journal of Naval Architecture and Marine Engineering, 2008

This paper describes a research program on podded propulsors that combines parallel developments ... more This paper describes a research program on podded propulsors that combines parallel developments in numerical prediction methods and experimental evaluation. Amongst the hydrodynamic issues that have been identified and addressed are questions regarding the effects of hub taper angle, pod-strut configurations, static azimuthing conditions, pod-strut interactions, gap pressure, pod gap and pod-strut geometry on podded propulsors' performance. On the experimental side, a pod dynamometer system consisting of a six-component global dynamometer and a three-component pod dynamometer were designed, manufactured and used to perform measurements on propeller thrust and torque and unit forces and moments in the three orthogonal directions in pusher and puller configurations in open water conditions. Four propellers with the same blade sections but different hub taper angles were designed and used to fit with eighteen pod-strut shells. Among the shells, two pod-strut models were based on t...

Abstract: A simple numerical procedure is established and implemented into a time domain panel me... more Abstract: A simple numerical procedure is established and implemented into a time domain panel method to predict hydrodynamic performance of marine propellers with sheet cavitation. This paper describes the numerical formulations and procedures to construct ...