Propeller Forces Research Articles

Ship hydrodynamic performance analysis and model construction based on CFD method

Abstract CFD method has the advantages of high forecast accuracy, wide applicability, strong stability of calculation results, and low cost, and nowadays it has been widely used in various fields. The CFD method has many advantages when applied to ship hydrodynamic performance analysis, specifically to ship hydrodynamic performance prediction, problem mechanism research, and performance optimization. Based on this, this paper utilizes the CFD method to carry out a model analysis of ship hydrodynamic performance. By analyzing the propeller efficiency, the reasoning force and torque of the double propeller in the symmetric case are decreased. However, the efficiency is improved by 1.4% compared with the asymmetric case, which shows that the method adopted in this paper can effectively improve the ship hydrodynamic force. Through the above research, we aim to provide a certain reference for the improvement of ship hydrodynamic performance.

Vibration Characteristic Research of 100 m New Polar Exploration Cruise Based on Finite Element Modeling

Luxury cruise ships are high-end passenger ships with facilities on board for the leisure and entertainment of passengers, so the comfort of luxury cruise ships is a matter of great concern. In this paper, a finite element model of a new polar exploration cruise ship is established, and the wet modes of the whole ship are calculated using the virtual mass method and compared with the principal frequencies of the excitation forces to initially verify the rationality of the design of the structural vibration characteristics of the whole ship. The admittance matrix of the vibration velocity to excitation force was calculated by a frequency response analysis, and the vibration velocities at the stern plate and main engine foundations were tested during sailing. Then, the obtained propeller and main engine excitation forces were loaded into the finite element model; the vibration velocities of each compartment were calculated and compared with the compartment vibration velocity test values. The errors were within the engineering allowable range, verifying the accuracy of the excitation forces. The propeller and main engine excitation forces were loaded separately on the finite element model to calculate the vibration velocity of each cabin, and the contribution of the two excitation sources to the vibration velocity of each cabin was analyzed. It was found that the contribution of the excitation source to the cabin response was related to the relative position between the cabin and the excitation source. When the cabin was located in the cabin adjacent to or directly above a certain excitation source, the contribution of the excitation source to the cabin response was greater. When the cabin was farther away from both excitation sources, the contribution of the propeller excitation was greater. This provides a targeted reference for the preliminary vibration assessment and later vibration control of the new polar expedition cruise ship.

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

The accurate and efficient prediction of vessel maneuvering characteristics in calm water and in waves using numerical methods is challenging. The objective of this work is to demonstrate the use of a Gaussian Process Regression based data-driven propeller and rudder model for vessel maneuvering in both calm water and in waves. The data-driven propeller and rudder model is trained with CFD simulations of the discretized propeller and rudder operating in the behind condition at different forward speeds, drift angles, and rudder angles. The data-driven propeller and rudder model enables the accurate calculation of maneuvering performance with low computational expense. This work describes the process for training and implementing the data-driven propeller and rudder model in a CFD package. The calm water zigzag and turning circle maneuvering characteristics for the ONR Tumblehome are evaluated and are compared to archival experiments. Furthermore, the maneuvering characteristics are evaluated in regular waves with several different wave conditions. In addition to demonstrating the accurate and efficient calculation of maneuvering performance, this work provides a multi-fidelity database of propeller and rudder forces at different forward speeds and drift angles, which can be used to train future data-driven propeller and rudder models.

Photoresponsive CHA-Integrated Self-Propelling 3D DNA Walking Amplifier within the Concentration Localization Effect of DNA Molecular Framework Enables Highly Efficient Fluorescence Bioimaging.

While three-dimensional (3D) DNA walking amplifiers hold considerable promise in the construction of advanced DNA-based fluorescent biosensors for bioimaging, they encounter certain difficulties such as inadequate sensitivity, premature activation, the need for exogenous propelling forces, and low reaction rates. In this contribution, a variety of profitable solutions have been explored. First, a catalytic hairpin assembly (CHA)-achieved nonenzymatic isothermal nucleic acid amplification is integrated to enhance sensitivity. Subsequently, one DNA component is simply functionalized with a photocleavage-bond to conduct a photoresponsive manner, whereby the target recognition occurs only when the biosensor is exposed to an external ultraviolet light source, overcoming premature activation during biodelivery. Furthermore, a special self-propelling walking mechanism is implemented by reducing biothiols to MnO2 nanosheets, thereby propelling forces that are self-supplied to a Mn2+-reliant DNAzyme. By carrying the biosensing system with a DNA molecular framework to induce a unique concentration localization effect, the nucleic acid contact reaction rate is notably elevated by 6 times. Following these, an ultrasensitive in vitro detection performance with a limit of detection down to 2.89 fM is verified for a cancer-correlated microRNA biomarker (miRNA-21). Of particular importance, our multiple concepts combined 3D DNA walking amplifier that enables highly efficient fluorescence bioimaging in live cells and even bodies, exhibiting a favorable application prospect in disease analysis.

Excitation force on a pump-jet propeller: The clocking effect of pre-swirl stator

The impact of the clocking effect of the pre-swirl stator on the excitation force of a pump-jet propeller is investigated in this paper. The clocking effect, a common concept in fluid machinery, is applied and extended to the relative circumferential position between the pre-swirl stator and the submarine hull in this paper. The research is conducted using computational fluid dynamics (CFD) and water tunnel experiments. The CFD results demonstrate that the clocking effect exerts a negligible influence on the steady performance of the pump-jet. However, the excitation force of the rotor is greatly influenced by it. This is due to the fact that the stator, when positioned at various clocking positions, generates different wakes that change the amplitude and phase distribution of the rotor strips’ excitation force. Furthermore, the experimental results demonstrate that the influence of the clocking effect on the duct vibration and the noise radiated by the pump-jet should not be ignored, the trend of which is consistent with that of the excitation force obtained by CFD, thereby establishing a clear correlation between the excitation force and the vibration and noise level. This paper is of guiding significance for the low-noise design of submarine pump-jets.

Ballistic and thermal characterisation of greener composite solid propellants based on phase stabilized ammonium nitrate

Several representatives of a new class of "greener" propellants, comprising polyurethanes (based on recycled PET) as the binder, phase stabilized ammonium nitrate (PSAN) as the eco-friendly oxidizer, and triethylene glycol dinitrate (TEGDN) as the energetic plasticizer, together with aluminium-magnesium alloy as fuel and iron oxide powder (α-Fe2O3) as the catalyst, were prepared and investigated through specific analytical tools. Besides morphological and compositional investigations, the thermal behaviour and ballistic properties of the propellants were determined, and compared to those of consecrated propellants compositions, based on ammonium perchlorate. The calorimetric tests were used to measure the heat of combustion and specific volume. Impact and friction sensitivities were also measured. The ballistic tests carried out in closed bomb and the original data processing approach used allowed, in addition to the propellant force and covolume, the identification of a critical parameter such as the power index from Vieille's law of the burning rate.

Study on flocculation performance and mechanism of cationic polyacrylamide on montmorillonite: Insights from experiments and molecular simulations

To achieve efficient flocculation of fine montmorillonite particles, molecular simulation and flocculation test were investigated to explore the influence of cationic monomer on the performance of cationic polyacrylamide (CPAM) flocculating montmorillonite particles. Three cationic monomers including methylacryloxyethyl trimethyl ammonium chloride (DMC), acrylamide propyl trimethyl ammonium chloride (ATMAC), and methylacrylamide propyl trimethyl ammonium chloride (MAPTAC) were copolymerized with acrylamide (AM) to produce CPAM copolymers. The simulation results suggested the electrostatic interaction was the primary internal propelling force for the stable adsorption of three distinct CPAM copolymers on the montmorillonite/water interface, followed by hydrogen bonding. Flocculation test indicated that CPAM has better flocculation effect on fine montmorillonite particles only when it has strong electrostatic adsorption and bridging capacity. This research establishes a theoretical foundation for the structural design of new flocculants for fine clay minerals.

Investigation on Lateral Vibration Transmission Control of a Shaft-hull System with a Piezoelectric Actuator Support

A piezoelectric actuator support (PAS) is proposed to suppress lateral vibration transmission from the shaft to the hull of underwater vehicles subjected to the excitation of propeller forces. The PAS consists of eight rhombic structures with embedded piezoelectric actuators and is arranged between the stern bearing housing and the hull. The dynamic model of the shaft-PAS-hull system is developed to analyze the characteristics of power flow through the PAS. The suppression performance of acoustic radiation of the hull is analyzed to verify the effectiveness of the PAS. Numerical results have shown that the PAS is able to suppress the transmission of lateral vibration induced by the propeller forces and accordingly reduce the hull vibration as well as sound radiation.

Effect of Tip Clearance on the Cavitation Performance of High-Speed Pump-Jet Propeller

To investigate the impact of tip clearance variation on the cavitation performance of a high-speed pump-jet propeller, Fluent software was employed for simulation calculations. The study utilized the RNG k-ε turbulence model and ZGB cavitation, conducting three-dimensional numerical simulations under both steady and transient conditions. A pump-jet propeller with a rated speed of 20,000 r/min was used to set three kinds of clearance for simulation, and the simulation proved to be reliable by comparison with the experiment. Initially, the analysis examined the effect of tip clearance on cavitation characteristics and cavitation volume under steady-state conditions, while also studying the distribution patterns of cavitation. Subsequently, the radial force and pressure pulsation of the jet propeller are analyzed by FFT processing, aiming at the influence of tip clearance on the structural strength of the pump-jet propeller. Under the design conditions, the smaller tip clearance shows better performance, while the larger tip clearance shows stronger anti-cavitation ability than the smaller clearance. In addition, the greater the tip clearance, the greater the radial force and pressure pulsation, which will adversely affect the pump-jet structure. The research results provide some references for further research on the effect of high-speed pump-jet propeller structures on performance.

Indirect measurement of propeller fluctuating forces using an inverse analysis: Numerical and experimental studies

The propeller fluctuating force is being recognized as the dominant source of underwater radiated noise, its accurate acquisition is thus necessitated for a reliable acoustic-structure analysis and optimization of marine ships. However, such dynamic operational forces are frequently impossible or expensive to directly measure due to various practical challenges. To alleviate this limitation, this paper presents an inverse method for the indirect estimation of propeller forces using measured shafting vibration responses. The force reconstruction procedure is constructed based on the state-space model of the propeller–shafting system, which can be derived by a data-driven subspace identification algorithm in conjunction with either the numerical or experimental models of the system. To ensure the robustness of the inverse analysis in the presence of inevitable measurement noise, a modified regularization strategy based on homotopy continuation is introduced. The effectiveness of the proposed algorithm is demonstrated through numerical simulations and experimental investigations. The obtained results demonstrate the potential feasibility of indirect measurement for accurately identifying propeller fluctuating forces in the time domain.

Vibro-acoustic responses of a hull due to structural and acoustic excitations from a propeller

The vibro-acoustic responses of a submerged hull under propeller force are investigated. The propeller force is generated by propeller vibration and transmitted from the propeller to the hull via the shaft and fluid, namely, the structural and acoustic excitations from the propeller. Evaluating the effect of each excitation on the hull is important for the noise control of a vessel. This paper presents a technique using the finite element method and the coupling method based on the frequency response function to model a complex vessel comprising a three-dimensional propeller, shaft, and hull, to separate structural and acoustic excitations from the propeller and to load the hull. The results show that the structural excitation from the propeller is the primary way to excite the hull. When a hull is subjected to structural and acoustic excitations simultaneously, the phase difference between the sound radiation from the hull due to structural excitation and that due to acoustic excitation determine whether the sound radiation from the hull increases or decreases. In general, the phase difference is in-phase for longitudinal cases and out-of-phase for transverse cases.

Influence of Interpolation Scheme on the Accuracy of Overset Method for Computing Rudder-Propeller Interaction

Abstract The overset method and associated interpolation schemes are usually thoroughly verified only on synthetic or academic test cases for which conclusions might not directly translate to real engineering problems. In the present work, an overset grid method is used to simulate a rudder-propeller flow, for which a comprehensive verification and validation study is performed. Three overset-related interpolation schemes (first order inverse distance, second order nearest cell gradient and third order least squares) are tested to quantify and qualify numerical errors on integral quantities, mass imbalance, flow features and rudder pressure distributions. The performance overhead is also measured to help make accuracy versus performance balance decisions. Rigorous solution verification is performed to estimate time and space Discretization, iterative and statistical uncertainties. Validation of the propeller-rudder flow against experimental data is also done. The results show that, while the choice of interpolation scheme has minimal impact on time-averaged integral quantities (like propeller and rudder forces), they do influence the smoothness of the time signals, with the first order scheme resulting in large intensity high-frequency temporal oscillations. Lower order interpolation methods also produce more interpolation artifacts in fringe cells, which are then convected downstream. Mass imbalance is also affected by the interpolation scheme, with higher order schemes such as the third order least squares approach resulting in an order of magnitude lower flux errors. The limitations of first order schemes do not, however, result in significant lower computational overhead, with the second order nearest cell gradient being even cheaper than the inverse distance scheme in the tested implementation. Lastly, validation shows promising results with rudder forces within 10% of the experiments.

Stochastic propeller force and moment reconstruction at a shaft end based on an improved Kalman filter

Measuring the unsteady hydrodynamic excitation of a marine propeller at a shaft end accurately from multiple directions is crucial for minimizing the unwanted vibration and noise of ships. Due to the synchronous loading of high static thrust and torque, an innovative piezoelectric multicomponent balance embedded into a hollow shaft end is designed. However, complex coupling between the balance and shaft structure is formed. This leads to crosstalk disturbance and a modal dynamic amplification effect on all measuring channels. To overcome this, an improved Kalman filter algorithm based on the subspace modal identification (SMI) method is established, thus allowing us to reconstruct and locate equivalent unsteady excitations accurately in multiple directions with response-only networks. The effectiveness of proposed framework is test on a simulated nonrotating shaft end system with twelve force and three acceleration response channels. The selection of the smoothing delay parameter and whether crosstalk is considered are two main factors that influence the reconstruction accuracy.

Aerodynamic Analysis of Conventional and Boundary Layer Ingesting Propellers

Abstract The boundary layer ingestion (BLI) concept has emerged as a novel technology for reducing aircraft fuel consumption. Several studies designed BLI-fans for aircraft. BLI-propellers, although, have still received little attention, and the choice of open-rotors or ducted propellers is still an open question regarding the best performance. The blade design is also challenging because the BLI-propulsors ingest a nonuniform flow. These aspects emphasize further investigation of unducted and ducted BLI-propulsors and the use of optimization frameworks, coupled with computational fluid dynamics simulations, to design the propeller to adapt to the incoming flow. This paper uses a multi-objective NSGA-II optimization framework, coupled with three-dimensional RANS simulations and radial basis function (RBF) metamodeling, used for the design and optimization of three propeller configurations at cruise conditions: (a) conventional propeller operating in the freestream, (b) unducted BLI-propeller, and (c) ducted BLI-propeller, both ingesting the airframe boundary layer. The optimization results showed a significant increase in chord and a decrease in the blade angles in the BLI configurations, emphasizing that these geometric parameters optimization highly affects the BLI-blade design. The unducted BLI-propeller needs approximately 40% less shaft power than the conventional propeller to generate the same amount of propeller force. The ducted BLI-propeller needs even less power, 47%. The duct contributes to the tip vortex weakening, recovering the swirl, and turning into propeller force, as noticed from 80% of the blade span to the tip. However, the unducted and ducted BLI-configurations presented a higher backward force, 26% and 46%, respectively, compared to the conventional propeller, which can be detrimental and narrow the use of these configurations.

CFD investigation on the hydrodynamic loads and motions when ship maneuvers in regular and irregular waves

To explore and predict the ship maneuverability in the regular and irregular waves, the zigzag tests, the turning tests, and the course-keeping tests for the model-scale S175 containership under various wave conditions are simulated. The simulations are performed using a structured overset Unsteady Reynolds Averaged Navier-Stokes (URANS) solver with a moving grid. A body force method is adopted to predict the propeller forces. The simulation results are validated by the free-running experiments with satisfactory accuracy, which indicates that the present simulation strategy is effective and reliable. The hydrodynamic loads on the hull and the rudder together with the ship motion characteristics during the maneuvers in waves are obtained. It is concluded that the ship motions and hydrodynamic loads increase with the increase of the wavelength when the wave height is kept constant. The variation trends and magnitudes for low-frequency components of the self-propulsion factors in waves are similar to those in the calm water condition except obvious high-frequency fluctuations due to the wave effect. For the zigzag tests under the long-crested and short-crested irregular waves, the time histories of the yaw and rudder angle are similar. For the turning tests, the amplitude of roll motion in waves is much larger compared with that of the zigzag tests under the same wave condition, and the drift of the trajectory due to the wave is obvious. The current course keeping simulation can be an alternative tool to predict course keeping maneuvers in waves. Furthermore, flow visualizations are presented for providing a better understanding of the wave effect on free-running ship maneuvers.

Establishing the True Dynamic Bending Moment of Propeller Shaft Using a Single Bridge of Strain Gauge

The measurement of shaft bending (whirling) moment can be performed via a telemetry system including strain gauges which can obtain the bending stress. By using a single bridge of strain gauge, it was possible to obtain only the nominal bending moment. However, in case of the propeller shaft vibration measurement, the true dynamic bending moment is needed to evaluate the effect of propeller forces on the stability of the bearings. To deal with this, typically two bridges of strain gauge at 90 degrees are needed. This research presents a novel reliability assessment method in establishing the true dynamic bending moment using only one bridge of strain gauge. This is achieved by using the actual bending stress measured by strain gauge combined with its own phase lag stress at an angle of 90 degrees. To validate this technique, the experiments were performed under the rapid turning transient states during a sea trial of a 50,000 DWT oil/chemical tanker. As a result, great fluctuations in propeller force were detected, resulting in a non-uniform oil film in the bearings. The displacement sensor was also installed and confirmed the established true dynamic bending moment.

Framework for data-driven propeller and rudder modeling for ship maneuvering

The maneuvering characteristics of a vessel must be understood for safe and efficient operation in the ocean environment. During a maneuver, the propeller and rudder can operate in off-design conditions. Computational Fluid Dynamics is a useful tool to capture flow effects like viscous separation, but it is too costly to perform a large number of maneuvering simulations with a discretized propeller. The propeller has much smaller time and length scales compared to the maneuver, which drives up the computational cost when the propeller is discretized. Body-force propeller models provide a less expensive means of modeling a maneuvering vessel with CFD, but many propeller models can be inaccurate when the propeller operates off-design. This work develops a framework for a data-driven propeller and rudder model which is trained with high-fidelity simulations of the propeller and deflected rudder operating in the wake of the hull. The dimensionless velocity and oblique flow angle are used as features for the propeller and rudder model. The uncertainty of the data-driven model is dependent upon the error inherent in the training and validation data as well as the uncertainty induced by using a surrogate model to determine the response surface. The underlying uncertainties are examined. The calculated propeller and rudder forces from the data-driven model are compared to the experimental forces. The turning circle characteristics of the KRISO Container ship at model scale are examined with the implemented data-driven propeller and rudder model. The accuracy of the method used to train the model is maintained and the computational cost of modeling a maneuvering vessel is dramatically reduced compared to using a discretized propeller.

Data driven control based on Deep Q-Network algorithm for heading control and path following of a ship in calm water and waves

A reinforcement learning algorithm based on Deep Q-Networks (DQN) is used for the path following and heading control of a ship in calm water and waves. The rudder action of the ship is selected based on the developed DQN model. The spatial positions, linear velocities, yaw rate, Heading Error (HE) and Cross Track Error (CTE) represent the state-space, and a set of rudder angles represents the action space of the DQN model. The state space variables are in continuous space and action spaces are in discrete space. The decaying ϵ-greedy method is used for the exploration. Reward functions are modeled such that the agent will try to reduce the Cross Track Error and the Heading Error. Based on the literature available, the L7 model of a KVLCC2 tanker is used for testing the algorithm. The vessel dynamics are represented using a 3DoF maneuvering model that includes hydrodynamic, propeller, rudder and wave forces. The wave disturbances are calculated from the second-order mean drift forces . The environment is assumed to have the Markov property. The CTE and HE are calculated based on the Line of Sight (LOS) Algorithm. The effect of Pre-trained weights on different heading actions is investigated based on the exploration threshold. The DQN is trained and tested for heading control and path-following in calm water and different wave headings.

ANALISIS GAYA DORONG (THRUST) PROPELLER PADA PESAWAT MODEL REMOTE CONTROL (UAV)

Unmanned aircraft or known as UAV (Unmanned Aerial Vehicle) is an aircraft technology that is controlled ly by the operator using Control. The thrust is determined according to the needs of the aircraft itself. This study uses a thrust test stand that uses a mass measuring device as a measuring force, using a brushless motor and 3 different types of propellers, namely propeller two with a size of 8 x 4 inches and 10 x 7 inches, three propellers with a size of 6 x 3 inc to determine the optimal thrust for missions flying -controlled model aircraft (UAV). After testing, it was found that the smallest thrust force of the 6x3 inch blade type propeller, on this type of propeller only 3,874 N of thrust is produced at 100% throttle percentage and uses a 3 cell battery. While the greatest thrust generated from the propeller with a type of two when 10x7 inches, on this propeller and using a 4 cell battery can produce a Thrust of 13,194 N with a percentage of full throttle or 100%. The thrust required for the aircraft to fly cruising in the air is 0.806 N, while the thrust required for the aircraft to take off is 6.513 N.Keywords: Control Model Aircraft, Propeller, Thrust

Changes in Propeller Shaft Behavior by Fluctuating Propeller Forces during Ship Turning

It is known that a ship’s shafting system can be adversely affected by hull deformation, variations in the engine power, the propeller load, and eccentric propeller thrusts, thereby increasingly affecting the behavior of the shaft’s movement. A deformed shafting system may also lead to a potential risk of bearing damage by causing a change in the local load of the rear part of the after-stern tube bearing of the propeller shaft. With this concern, a series of previous studies were focused on optimizing the effects of hull deformation by securing a proper level of propulsion shaft stability and optimizing the relative inclination angle and oil film retention based on a quasi-static state, that is, Rules for the Classification of Steel Ships and experiences of shipyards. However, despite our efforts to resolve this issue, marine accidents involving stern tube bearing damage have continued to occur under relatively unattended ship motions in a transient state, that is, a quasi-static state that can possibly cause sudden stern flow field changes. Therefore, to improve the stability of the propulsion shaft, it is necessary to understand ship motions and the conditions of shafting systems in a dynamic state and a transient state when the system is designed. From this point of view, this study investigated the effect of changes in eccentric propeller forces on the motion of the propeller shaft in a representative transient state of a 50,000 deadweight tonnage tanker by means of the strain gauge method and a displacement sensor. The research findings demonstrate that propeller thrust fluctuations have a direct effect on the shaft stability by significant changes in the shaft motion that can lead to unbalanced supporting loads on the stern tube bearing. These results clearly reproduce the cause of damage to the ship in which the accident occurred at a reliable level and will be a reference for establishing pragmatic guidelines for preventing damage to similar ships in the future.