Ice-Class Propeller Strength and Integrity Evaluation Using Unified Polar ClassURI3 Rules

In advanced marine industry, the reduction in weight of hull structures for a very large object ship plays an important role as the economic efficiency is the most significant aspect. In this paper, we investigate the ultimate strength of structural ship stiffened-plates designed by International Association of Classification Societies (IACS) Common Structural Rules (CSR) methods of collapse state, by applying for ANSYS nonlinear finite element analysis (FEA). Specifically, the ultimate limit assessment methods for the outer bottom of ship structures, which have drawn a significant attention from industrial marine and offshore structures, are proposed to reduce the weight of ship structures. To solve this, we study the structures of a hypothetical Very Large Ore Carrier (VLOC) designed by pre-CSR and CSR methods. In particular, the stiffened-plates under the biaxial compression and lateral pressure loads with simply supported or/and clamped boundary condition(s), the results ultimate limit state assessment performance of Nonlinear FEA methods are shown and compared to various states.

Turbomachinery aerodynamic and aeroacoustic modelling is recognized to be one of the main areas of interest in the frame of industrial engineering, due to the large number of applications concerning the rotating fluid machines. Numerical modelling is today widely integrated in the design and development process of industrial components, as well as Computational Fluid Dynamics (CFD) is a tool well integrated into the industrial development and production life-cycles. This has been made because of two main factors: the increase in the performance of relatively cheap computing systems and the progress made by development of integrated CAE virtual environment even more oriented to design and optimization. Furthermore well established and validated CFD methodologies able to deal with the high complexity of geometries and multiphysics approaches are available and practicable within the industrial environment. Nevertheless since for many of applications such as aerodynamics, heat exchange, etc., CFD is largely used, there are still some areas where it represents a challenge, in particular for its industrial applicability. One of these areas is the Computational AeroAcoustics (CAA), whose interest is rapidly growing due to the increasing demand of quick and efficient numerical tools for the design-to-noise approach to airframe components. The major difficulty of CAA is that noise is a secondary effect of other physical phenomena, and noise prediction has to deal with highly complex topics such as turbulence modelling and transition to turbulence prediction. Moreover the sound pressure compared with the hydrodynamic pressure is several orders of magnitude smaller making its numerical prediction very difficult. The goal of the present work is to perform investigations on two rotating fluid machines: the vertical axis wind turbines (VAWT) and the high speed transonic cruise propellers. The investigations performed were focused on the aerodynamic and aeroacoustic theoretical and numerical modelling in order to achieve the numerical results that actually miss in the literature improving the know-how for two classes of problems which play a central role in the modern industry: the renewable energies and the advanced transportation systems. VAWT modelling was approached from a theoretical point of view, by the implementation of a modern unsteady aerodynamic model for non-stationary airfoil aerodynamic coefficients prediction (the Beddoes Leishman model) into a classical theory, the Double Streamtube Paraschivoiu model. The acoustic modelling of WT was approached on a general basis with the modelling of the airfoil self-generated problem. It was chosen as it is one of the most prominent noise sources for wind turbines and it represents a big challenge for CFD. The preliminary literature review pointed out how there are different airfoil self-generated noise typologies, according to the laminar/turbulent characteristics of the flow field, airfoil aerodynamic parameters and far-field flow conditions. Different CFD numerical approaches were used for the different noise generation mechanisms, including transient RANS/LES simulations with a particular focus for novel turbulence modelling methodologies, involving transitional models and Embedded LES. The acoustic pressure flow computations were performed with the Ffowcs Williams Hawkings (FW-H) acoustic analogy and pressure time signals post-processed with an in-house built acoustic tool. Deep explorations of acoustic signal noise processing, Fast Fourier Transformation techniques and noise signal corrections have been necessary in order to achieve good agreement between experimental and computational data. The reference test-case was the NACA 0012 airfoil, chosen for the wide amount of experimental data available in literature in a significant range of velocities and angles of attack. The problem of propeller aerodynamic and aeroacoustic modelling was approached with the CFD and CAA simulation of a subsonic propeller, the NACA 4-(3)(08)-03, chosen for the experimental results available in literature for the 2-bladed and 7-bladed configurations. This test-case allowed us to set up properly the numerical simulation, the CAD model and the computational grid requirements for such kind of geometries. In a second stage the attention was focused on the NASA SR2 and SR3 geometries, both in the 8-bladed configuration. Experimental data in transonic conditions for wind tunnel and flight test were available for these two geometries, and numerical simulations were performed for 5 different data sets, for asymptotic Mach numbers between 0.6 and 0.9 and rotational speeds between 6000 and 9000 rpm. Results of the simulations are compared with experiments, showing the ability of this approach to predict noise with a discrepancy within a few dB for the different simulated conditions and microphones locations. Particular attention is given to the set of corrections to be applied to acoustic experimental data in order to be consistently compared with free field CFD results. The CFD simulation strategy has been refined to perform complete aerodynamic and aeroacoustic calculations with highly competitive computational cost.

Hydrodynamic pressure is often a crucial factor in the evaluation of slope stability analysis, especially for many rainfall-triggered landslides. Nevertheless, hydrodynamic pressure is rarely considered in the traditional limit equilibrium slice method of slope stability analysis since effective and reliable hydrodynamic pressure data are often lacking in practice. Moreover, efficient methods to involve these data in slope stability analysis are an urgent need. To overcome these concerns, the flow velocity and direction system (FVDS) is employed to measure the groundwater flow velocity, which can be used to generate hydrodynamic pressure samples at different monitoring points. Based on these samples, the hydrodynamic pressure of each soil strip is estimated using artificial neural networks (ANNs). Afterward, an improved Bishop method that considers hydrodynamic pressure is proposed. The effectiveness and significance of the proposed method are illustrated with a case study, the Fanshantou landslide in Zhejiang Province, China. The safety factor before and after taking drainage countermeasures is also calculated and compared. The results indicate that hydrodynamic pressure plays an important role in the stability analysis of the Fanshantou landslide. Compared with the classical Bishop method, the improved method is shown to agree better with the actual deformation characteristics of the landslide.

Applying propeller boss cap fins (PBCF) in open B-series has been studied. PBCF is able to decrease the wake effect behind the propeller which can influence the propeller’s thrust and torque. Open propeller using PBCF is analyzed using computational fluid dynamics (CFD) which generate convergent result compared to experimental data. The solver is based on the Reynolds Averaged Navier Stokes Equation (RANSE) solutions and turbulence modeling explicit algebraic stress model (EASM). The test data was obtained from CFD simulations consisting of the open propeller and PBCF despite the experiment was done to PBCF only. All measurements were carried out from J = 0 to J = 1.0 with speeds from 0 m/s to 2.445 m/s.The results of the investigation on the B4-70 propeller with Boss cap fins convergent showed thought-provoking phenomena both on CFD and experimental work. Test results at The B4-70 Propeller without using PBCF high Pressure at J = 0.1 - 0.9, but with boss cap fins can reduce pressure at high-speed J = 0.9, so further research is needed to low-speed J = 0.1 - 0.5; Then visualization of velocity on propeller B4-70 without PBCF shows an increase in flow velocity in the boss cap fins when J = 0 to J = 0.9. The induced axial velocity in the blade propeller is the same and propeller B4-70 with PBCF decreases in speed in the boss cap fins when J = 0 to J = 0.9. However, the induce axial velocity in the blade propeller is the same. Convergent PBCF can reduce the return flow velocity in the boss cap propeller area, inversely proportional to the open propeller. Comparison of open propeller and PBCF shows that using PBCF there is an increase in the KT value at high speed of 10% to24% and a decrease in the 10KQ value on PBCF from J = 0.8 to J = 1.0 of 7% to 14%, but η_0 value at J = 0.8 to J = 1.0 increased by 3% to 8%. This Explained that the use of PBCF when the higher the value of J, greater the increase in η_0 value. Mainly, B4-70 propeller with PBCF with a converging boss cap shape with 15-degree slope exhibits increased efficiency.

Liquid storage tanks are essential facilities in lifeline and industrial systems. To ensure liquid tightness, serviceability is the prime design concern for these structures. While there have been major studies on the behavior of steel tanks, little attention has been paid to the behavior of rectangular concrete tanks. In this study, the dynamic response of concrete rectangular liquid storage tanks is investigated. In the current design practice, the response of liquid and tank structure is determined based on rigid tank wall and the lumped mass approach. However, the results of analysis show that the flexibility of tank wall increases the hydrodynamic pressures as compared to the rigid wall assumption. Also, recent studies show that the lumped added mass method leads to overly conservative results in terms of base shear and base moment. In addition, in spite of advanced analysis techniques available for dynamic analysis of liquid storage tanks such as finite element method and sequential coupling analysis procedure, there is a need to develop a simplified analysis method for practical applications. In this thesis, a simplified method using the generalized single degree of freedom (SDOF) system is proposed for seismic analysis of concrete rectangular liquid containing structures (LCS). Only the impulsive hydrodynamic pressure is considered. In the proposed method, the consistent mass approach and the effect of flexibility of tank wall on hydrodynamic pressures are considered. Different analytical methods are used to verify the proposed model in this study. The comparison of results based on the current design practice, the analytical-finite element models and full finite element model using ANSYS® shows that the proposed method is fairly accurate which can be used in the structural design of liquid containing structures. Parametric studies on seismic analysis of concrete rectangular LCS using the generalized SDOF system are carried out. Five prescribed vibration shape functions representing the first mode shape of fluid structure interaction system are used to study the effect of flexibility of tank wall and boundary conditions. The effect of flexibility of tank wall, the amplitude of hydrodynamic pressure, the added mass of liquid due to hydrodynamic pressure, the effective heights for liquid containing system and the effect of higher modes on dynamic response of LCS are investigated. In addition, the effect of variable size of tanks and liquid depth are studied. The contribution of higher modes to the dynamic response of LCS is included in the proposed model. A design procedure based on the structural model using the generalized SDOF system is proposed in this study. Design charts and tables for the added mass of liquid due to impulsive hydrodynamic pressure and the corresponding effective heights are presented. The proposed design procedure can be used for engineering design applications.

Fast-running CFD calculations of the ONR Tumblehome performing maneuvers in calm water and in waves using a Gaussian process regression propeller and rudder model

NASA’s X-57 “Maxwell” distributed electric propulsion flight demonstrator has a high-lift system that includes 12 fixed-pitch high-lift propellers located upstream of the wing leading edge for lift augmentation at low speeds. These high-lift propellers are not required at higher speeds and are folded conformally along the nacelles to reduce drag when not in operation. Aircraft performance models and flight simulations incorporate propeller performance to predict thrust, moments, and power consumption and propeller model accuracy is important in identifying safe operating regimes for this aircraft. Current high-lift propeller performance models have been verified and calibrated against numerous computational fluid dynamics analyses under a variety of flight conditions. We performed a series of full-scale wind tunnel tests at the NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel to further validate these models, to identify any adverse operating conditions for these propellers, and to assess the accuracy of the facility’s new Propeller Test Stand. The results indicate that the models accurately predicted performance and that the right-handed propeller showed lower torque and thrust for a given propeller speed compared to the left-handed version. Acoustic data support these measurements, showing higher tonal noise for the left versus right propeller. We suspect this is due to slight differences in the material properties between the early production (right) and more recent (left) blade sets leading to greater detwisting in the right-handed blades under load. Both propellers demonstrated very stable operation throughout the test including during deployment, stowing, and windmilling. Furthermore, high-speed imagery of the spinning propeller indicated no blade oscillations or instabilities for any test case. We also leveraged these images to analyze the effects of propeller loading on blade detwisting and tip position. Unfortunately, the thrust measurements varied significantly during the test due to cross-loading of the Propeller Test Stand load cell, though trends in the thrust data were still observable. The torque measurement, however, remained very precise for all test points and was used for performance comparisons. As a result of this test, we validated and improved the X-57 high-lift propeller performance models, obtained detailed propeller acoustic data and high-speed imagery, observed the propeller operating safely during a variety of dynamic events, and identified two potentially adverse, low-propeller-speed conditions which will be avoided during normal aircraft operation.

Taking the AU5-50 propeller as an example, the detailed process of propeller modeling with atlas method and PropCad is compared. By comparing the auxiliary profiles used for modeling, it is pointed out that the blade model established by PropCad has more complete features and is not restricted by the propeller type. Besides, to verify the credibility of the PropCad modeling method, simulation analysis is carried out. First, the hybrid mesh and boundary layer mesh are divide for the flow field by integrated computer engineering and manufacturing (ICEM). Second, grid independence is verified utilizing a multiple reference frame (MRF) model. In the verifying process, three widely used turbulence models are analyzed and compared under advance ratio 0.7, and the results show that the hydrodynamic coefficient error calculated by the shear stress transport (SST) k-ω model is the smallest. Third, the computational fluid dynamics (CFD) calculation model is determined. The hydrodynamic performance of the propeller at different advance ratios is analyzed, and the CFD calculation results are in good agreement with the open water test data. Finally, the fluid-solid coupling analysis of the propeller is performed, and it is verified that the stress field of the propeller meets the material strength requirement. Therefore, it is proved to be feasible to conduct propeller modeling with PropCad.

Investigating the effect of biofouling on propeller characteristics using CFD

The infrastructure of roads, bridges, tunnels, subways, etc. is grooming day by day. In the recent era, soil nailing is the developing method for slope stability, road widening projects, and constructing deep foundations. This paper suggests a new and improved helical soil nail (HN) that offers an alternative to conventional soil nail (CN). Till now pullout studies on different model nails in c-Φ soil are still rare. In addition, the stability analysis for conventional soil nails was only studied using FEM analysis, whereas for helical soil nails the estimation of stability of slope is still mysterious. So, the present study includes the behavior of conventional and helical soil nails based on both laboratory and analytical methods in c-Φ soil. The present study also incorporated the use of theoretical equations and finite element analysis (using PLAXIS 2D) for comparing the stability of different profiles of soil nails (e.g., CN and HN) in c-Φ soil, which was unique to this study. By using the finite element method (FEM) and the limit equilibrium method (LEM), a factor of safety was also estimated for both types of nails (CN and HN). According to the experimental, analytical, and numerical findings, it is clear that helical soil nails (HN) exhibit less deformation and more factor of safety than conventional soil (CN) nails under similar loading and soil conditions.

The use of advanced computational methods: finite-element analysis (FEA) and computational fluid dynamics (CFD) will be considered in this chapter. FEA is useful to model conduction heat transfer, while CFD can additionally model fluid flow. Both methods rely on modelling the actual geometry of the full machine or machine component by discretizing the individual parts into smaller mesh elements, volumes or cells over which the heat transfer or flow variables are assumed constant. Triangular and quadrilateral mesh element shapes are typically used for 2D geometries, and tetrahedral, quadrilateral pyramid, triangular prism, and hexahedral shaped cells for 3D geometries.The FEA method is often applied to individual components in the electrical machine where the heat transfer mode is by conduction, such as the slot and winding. Useful models can often be formed in 2D. 3D FEA models for a particular part can also be created but are less commonly used due to the additional time to set up and solve.CFD is mainly of use to model the fluid flow and convection from surfaces in the machine and the models are nearly always 3D in nature. Models can be created for individual components of the machine or for the full machine, although this can be very complex to put together and solve. The model may also include conduction heat transfer.

Effect of biofouling roughness on a marine propeller's performance including cavitation and underwater radiated noise (URN)

While there are power saving and high thrust capability advantages of CPP (Controllable Pitch Propeller) for ice propulsion, the introduction of CP mechanism makes the propulsion system more vulnerable when operating in heavy ice conditions. In CPP designs, the recently released IACS URI3 – “Machinery Requirements for Polar Class Ships” provides the design forces on the propeller blade resulting from propeller-ice interaction. These design forces are also the source of the spindle torques, which can be used for the determination of CPP mechanism scantlings. In this paper, ice loads formulae in URI3 for open and ducted CPP will be adopted for an existing ice CPP for its mechanism check to evaluate the rationality of the Rule. To further explore the influence from different design principles on CPP scantlings, both the maximum life time ice load and the blade failure load provided in URI3 will be applied on the existing CPP to check its mechanism strength. The detailed comparison of the strength check outcomes provides very useful information for ice CPP design.

Results of experiments in open water at the Teishinsho Ship Experiment Tank are presented for 4-bladed propeller series, designed mainly for single-screw mercantile work. Three series of propeller were tested, namely, propellers with increasing pitch, decreasing pitch and constant pitch, all other particulars remained the same.The general plan of propeller is presented in Fig. 1. All the propeller models had diameter of 0.22m, boss ratio of 0.25, expanded area ratio of 0.40, blade thickness ratio of 0.045 and aerofoil-shaped blade sections. Six pitch ratios were taken for each series, namely, 0.4, 0.6, 0 8, 1.0, 1.2 and 1.4.The tests were carried out by means of a propeller boat with built-in propeller dynamometer. The immersion of the centre of propeller shaft was equal to 0.9D. The number of revolutions was kept constant at 7.0 per sec, and the speed of advance varied. The measured results were corrected for the static pressure of water on the shaft section, the resistance of the propeller boss and for the shaft frictional loss.No-dimensional diagrams of the test results are given in Fig. 2. From these diagrams, the design diagrams for our three series of propeller were constructed according to Admiral Taylor's method, and are given in Figs. 35. Also the design diagram similar to Dr. Schmidt's form is given in Fig. 6 for the constant pitch series.From Fig. 2 and Figs. 35, it can be seen that the difference in pitch distribution usually have no marked effect upon propeller performances in open water. But, as the effect of pitch distribution will be somewhat clearer in a non-uniform flow, propeller tests over a wide slip range in a wake flow are also intended. A part of this research program is now completed, and some remarks on its results are mentioned in the last part of the paper.

As modern diesel engine design progresses toward higher burst pressure and power density, strict performance indices impose greater demands on the structural strength and reliability of crankshafts. We integrated finite element analysis and strength testing methods to achieve a lightweight crankshaft design. A comparison of the simulated results with the test data revealed that the crankshaft safety factor surpassed the permissible safety factor by 3.5 times, demonstrating significant safety redundancy in the design. We employed topology optimization techniques to create various crankshaft optimization models, yielding near-optimal solutions. Consequently, we identified the crankshaft with the best overall performance following comparative evaluations. We examined the influence of the fillet structure on the safety factor to mitigate stress concentration issues. Through multibody dynamic fatigue analysis, optimizing the crankshaft fillet resulted in a 6~7% increase in the safety factor. The minimum safety factor for the designed crankshaft was 1.6 times higher than the material permissible safety factor, which was 1.15. Utilizing the developed transient dynamics model of the lightweight crankshaft and a backpropagation genetic algorithm, we created a crankshaft fillet design tool to streamline the design process, which holds significant importance for the marine engine sector.