A collaborative platform for integrating and optimising Computational Fluid Dynamics analysis requests

A Virtual Integration Platform (VIP) is described which provides support for the integration of Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) analysis tools into an environment that supports the use of these tools in a distributed collaborative manner. The VIP has evolved through previous EU research conducted within the VRShips-ROPAX 2000 (VRShips) project and the current version discussed here was developed predominantly within the VIRTUE project but also within the SAFEDOR project. The VIP is described with respect to the support it provides to designers and analysts in coordinating and optimising CFD analysis requests. Two case studies are provided that illustrate the application of the VIP within HSVA: the use of a panel code for the evaluation of geometry variations in order to improve propeller efficiency; and, the use of a dedicated maritime RANS code (FreSCo) to improve the wake distribution for the VIRTUE tanker. A discussion is included detailing the background, application and results from the use of the VIP within these two case studies as well as how the platform was of benefit during the development and a consideration of how it can benefit HSVA in the future

NUMERICAL SIMULATION OF THE CAVITATING FLOW AROUND MARINE CO-ROTATING TANDEM PROPELLERS

In the present paper, a numerical simulation has been carried out to determine the hydrodynamic characteristics in cavitating viscous flow of the conventional INSEAN E779A propeller in single and tandem configuration by using Singhal et al. cavitation model implemented in FLUENT Software. Firstly, calculations have been carried out on single E779A propeller in non-cavitating and cavitating flows. The computed performances have shown good agreement with experimental data. Next, the numerical approach has been applied in loaded conditions to the case of tandem propeller configurations with respectively 0.2 and 0.6 axial displacement. Results reveal that cavitation is qualitatively well predicted and the cavitation area is rather more pronounced on the fore propeller. Te use of tandem co-rotating propeller in loaded conditions is highlighted

Numerical prediction of propeller induced hull pressure pulses and noise

An operating marine propeller is one of the major sources inducing hull pressure pulses, onboard noise and vibration as well as underwater radiated noise. There are rising concerns of environmental impacts and comfort and welfare of passengers and crews due to these negative effects. Cavitation is a significant source of these effects, but it is typically inevitable if only the hydrodynamic efficiency of the propeller is optimized. To reduce the noise and the pressure pulses caused by the cavitation, a trade-off of the hydrodynamic efficiency should be made to design and optimize a propeller that possess both high hydrodynamic performance and low noise and hull pressure pulse generation. More accurate predictions are needed to identify the best trade-off between a high efficiency propeller design and a low pressure pulse and noise one.The study focuses on the numerical prediction of hull pressure pulses and radiated underwater noise using viscous CFD including the opensource package OpenFOAM and commercial package Star-CCM+. Numerical predictions are performed regarding different experimental configurations for determining hull pressure pulses and ship noise, including propellers mounted on inclined shafts and propellers operating behind ship hulls, under different scales and scaling laws with different operating conditions and Reynolds numbers.Non-cavitating propeller induced pressure pulses are generally lower in levels and rich in blade passing frequency comparing to cavitating conditions, with blade tip clearance as a major impact factor. For cavitating conditions the rate of cavity growth/shrinkage is found to play the dominating role generating pressure fluctuations. For certain model scale configurations, numerical predictions with ordinary approaches predict massive sheet cavity on propeller blades leading to pressure pulse prediction discrepancies comparing to experimental observations and measurements. These can be significantly improved by a developed bridged model considering laminar to turbulence transition. Tip vortex cavitation bursting is a common phenomenon found on propellers operating behind the ship hull and generating significant levels of pressure pulses. The phenomenon is numerically predicted with investigations of its generation mechanisms in relation to the propeller inflow, convex shaped sheet cavitation closure line and traveling re-entrant jet underneath the sheet cavity.Propeller induced noise prediction was studied using approaches focused on the FWH (Ffowcs Williams-Hawkings) acoustic analogy with incompressible input on permeable/porous data surface (PDS). \ua0Studies show this combination between incompressible input and FWH acoustic analogy can be erroneous, though using certain PDS placements and closer receivers the error can be reduced

Hydrodynamic Design Structural Analysis and Optimization of Marine Propeller Blade

There are many problems to be addressed in the design of marine propeller blade. Among these, the foremost is the efficiency of the propeller. The design of ship propeller involves a number of competing variables including the rake, pitch distribution and blade surface area. The propeller design also aims at achieving high propulsive efficiency at low levels of noise and vibration with reduced cavitation. All of these factors affect vessels top speed, fuel efficiency, and handling. A thorough understanding of propeller dynamics is necessary to design an efficient and reliable propeller blade. Numerical models are commonly used for the dynamic characterization of propeller blades, due to the difficulties of performing full-scale measurements. In contrast, the current research focuses on the hydrodynamic design of a Wageningen B-series four bladed propeller used for marine applications. The analyses presented in this thesis have been divided into three main phases. In the first phase, the hydrodynamic design of Wageningen B-series four bladed marine propeller is carried out, to determine the suitability and applicability of propeller blade for underwater conditions is done by 1) Open water characteristics determination, 2) Cavitation inception point determination for metallic propeller blade. The prevailing conditions applied for evaluating these hydrodynamic characteristics are taken from reference and validated with standard series data. In the second phase of the research, Strength determination of both metallic and composite propeller (E-glass epoxy material) are determined in terms of its stress and free vibration characteristics. Numerical analyses are carried out using suitable numerical methods for the deflection calculations and to determine the stress distribution in the blade foot and the blades at operational load conditions. A modal vibrational analysis for prediction of vibration response was also conducted for the blade, because the composite blades tend to deform more than that of metallic one and the deformation can be used in the analysis of hydrodynamic performance. Experiments are performed to compare the results with that obtained from the numerical analysis. In the last phase Structural optimization of composite propeller was done both for non-hybrid and hybrid composites, (comprises a series of combination of Glass fiber reinforced plastic and Carbon reinforced plastic GFRP & CFRP), using the mid-surface as reference and meshed with shell elements to find out the optimum ply stacking sequence for Interlaminar shear stresses and deflection minimization and operational efficiency improvement of composite propeller blade compared to metallic one. The obtained final stacking sequence of the composite propeller was evaluated by varying the number of layers in steps the Interlaminar shear stresses are calculated, and the results are compared with the metallic propeller. The following basic data are used for analysis and the main points performed during the works are given below. 1. The open water characteristics are predicted computationally on the basis of a validated small sized propeller where the delivered power (PD), the advanced coefficient (Vga), and the propeller revolution (N) are known. 2. The cavitation inception point for the metallic propeller is determined which can be used for structural analysis. 3. The Aluminum propeller blade is replaced with E-glass epoxy material blade and structural analyses for both the materials are carried out. 4. An optimum stacking sequence for composite material blade varied with non-hybrid and hybrid materials are determined. 5. Finally, a comparison has been made with metallic and composite materials in terms of their strength behavior

Numerical Study of Kaplan Propeller by Using CFD: Effect of Angle and Blade Diameter Variations

Efficient propeller performance contributes to better overall ship performance and speed. A well-designed propeller can optimize thrust generation, leading to improved maneuverability, responsiveness, and acceleration. It enables ships to maintain higher speeds while using less power, enhancing their competitiveness in the maritime industry. In this study, the Kaplan series propeller was analyzed by using Computational Fluid Dynamics (CFD). By modifying the angle of attack on the Kaplan propeller with 3, 4, and 5 blades, the distribution of the surface pressure, generated thrust, and torque value were easily identified and analyzed. The result shows that the change in the angle of attack influenced the pressure distribution on the back and face side of the propeller. The angle of attack is increased, and the pressure surface distribution also tends to increase. It has also affected the efficiency of the propeller performance which is expressed by the values of thrust propeller and torque. The more efficient the propeller performance, the less power it requires to produce the desired thrust

Numerical Prediction of Propeller Induced Hull Pressure Pulses

Ship propeller induced pressure pulses is one of the major sources of both onboard noise and vibration as well as underwater radiated noise. The need for accurate pressure pulse prediction is increasing due to rising concerns of environmental impacts and comfort and welfare of passengers and crews. More accurate pressure pulse prediction is needed to be able to reduce the margin between high efficiency propeller design and low pressure pulse propeller design.Experimental approaches are used for pressure pulse assessments in the final verification stage where models are produced, but they are limited in early design work. Potential flow based methods have been used for early estimation of pressure pulses, but due to the complexity of the pressure pulse generation mechanisms, including interaction between hull and propeller and various types of cavitation, viscous numerical methods are being developing as a complement to potential flow method and a faster and cheaper alternative of experimental testing. This thesis deals with the numerical prediction of marine propeller induced pressure pulses adapted from typical experimental procedures, including both model scale and full scale marine propellers operating in open-water conditions and behind hull conditions with non-cavitating and cavitating flows. Simulations were conducted using open-source package OpenFOAM and commercial package Star-CCM+ with Reynolds-Averaged Navier-Stokes (RANS) method.Studied cases show that for propellers in behind conditions, the present RANS approach can provide good accuracy regarding 1 st and 2 nd order BPF (Blade Passing Frequency) hull pressure pulses early in design stage. Higher order BPF pressure pulses were also predicted reasonably well, and different mechanisms inducing higher order BPF pressure pulses, including small tip clearance, transient cavitation appearance and sheet cavitation closure and its interaction with tip vortex cavitation, are outlined in the thesis. For model scale propellers operating under nearly uniform inflows, sheet cavitation is often over-predicted and an improved cavitation mass transfer model is proposed which take laminar separation as an additional inception criteria. Studies regarding mesh resolutions and scaling effects are also included in certain cases

Analysis of the Effect of Changes in Pitch Ratio and Number of Blades on Cavitation on CPP

Cavitation is a detrimental phenomenon to ship operations because it causes many losses. It caused some effects i.e decreased propeller efficiency, damaged propeller material, lower ship speed, vibration, and extreme noises. In that regard, this research conducts cavitation analysis on controllable pitch propeller (CPP) by varying number of blade i.e. 3, 4 and 5 blades; diameter i.e. 30, 40 cm and 50 cm; also pitch i.e 0.4, 0.6 and 0.8.  The research method is carried out by the author in this study by conducting a simulation method based on the CFD approach. The simulation process consists of 3 stage-post processor, solver manager, and post-processor. From the simulation based on the CFD approach result, it was found that propeller rotation has an effect on the pressure ratio value. As the propeller rotation increase, the value of the pressure ratio will increase as well. The value of the pressure ratio in propeller design affects the cavitation area that occurs in the propeller. The percentage of the cavitation area on the propeller has an increasing tendency with the number of blades, rotation, and pitch. On the propeller with diameter 300 mm, 3 blades, pitch 0.8 at rotation 125 rpm no indication of cavitation, then it increases to 1.41% at rotation 175 rpm and keeps getting higher at rotation 225 to be 4.22% from total propeller expanding area. Whereas at rotation 225 rpm and pitch 0.4 is 3.38 %, then it becomes 3.85 % at pitch 0.6, which is getting bigger at pitch 0.8 that is 4.22 %

CFD results on hydrodynamic performances of a marine propeller

In this work, the commercial Computational Fluid Dynamics (CFD), ANSYS-Fluent V.14.5 has been used to illustrate the effects of rudder and blade pitch on hydrodynamic performances of a propeller. At first, the characteristic curves of a container ship propeller are computed. Then, effects of rudder on hydrodynamic performances of the propeller in the both cases of the propeller with and without rudder have been investigated. The relationships between the blade pitch angle and the hydrodynamic performances of the selected referent propeller in this work having designed conditions as diameter of 3.65 m; speed of 200 rpm; average pitch of 2.459 m and the boss ratio of 0.1730. Using CFD, the characteristic curves of the marine propeller, pressure distribution, velocity distribution around propeller and the efficiency of the propeller have been shown. From the obtained results, the effects of rudder and blade pitch angle on hydrodynamic performances of the propeller have been evaluated

A Calibration Study with CFD Methodology for Self-Propulsion Simulations at Ship Scale

This paper summarises the main findings from the full-scale Computational Fluid Dynamics (CFD) analyses conducted at SINTEF Ocean on the case of MV REGAL, which is one of the benchmark vessels studied in the ongoing joint industry project JoRes. The numerical approach is described in detail, and comparative results are presented regarding the propeller open water characteristics, ship towing resistance, and ship self-propulsion performance. The focus of numerical investigations is on the assessment of the existing simulation best practises applied to a ship-scale case in a blind simulation exercise and the performance thereof with different turbulence modelling methods. The results are compared directly with full-scale performance predictions based on model tests conducted at SINTEF Ocean and sea trials data obtained in the JoRes project.publishedVersio