Prediction Of Hydrodynamic Performance Research Articles

Prediction of steady hydrodynamic performance of pump jet propulsion based on free wake vortex model

Due to mutual interference between various components, the transitional motion of fluid particles in the flow field of pump jet propulsion becomes more complex and variable. Additionally, the vortex structure at the wake can undergo severe contraction and deformation. To further improve the accuracy of predicting the hydrodynamic performance of pump jet propulsion, this paper proposes a time-varying, space-varying, and induced velocity-varying free wake numerical calculation model based on potential flow theory. A set of hydrodynamic performance prediction methods that consider the interference of the free wake model is also established. Furthermore, a velocity smoothing model based on time reversal is constructed based on the distribution pattern of numerical singularity points during the induced velocity calculation process, which enhances the robustness of the calculation program. By comparing and analyzing the numerical calculation results with experimental results, including pressure, circulation distribution, and hydrodynamic performance, the accuracy of the free wake model proposed in this paper is verified. The results also demonstrate that the free wake model proposed in this paper can effectively improve the prediction accuracy of the hydrodynamic performance of the pump jet propulsion.

Numerical Prediction of Hydrodynamic Performance of a Bulk Carrier Using CFD

Numerical Prediction of Hydrodynamic Performance of a Bulk Carrier Using CFD

Numerical Prediction of Hydrodynamic Performance of a Bulk Carrier Using CFD

Numerical Prediction of Hydrodynamic Performance of a Bulk Carrier Using CFD

Fast prediction method of propeller hydrodynamic performance based on SPF-LSTM

In order to realize fast and accurate prediction of hydrodynamic performance of UUV propeller, a hydrodynamic performance prediction model based on SPF-LSTM neural network was proposed in this paper, which combined with real propeller flow test and CFD numerical simulation technology. The model comprehensively considered the test data of real paddle and the simulation data based on CFD numerical simulation, and adopted the Sample penalty factor (SPF) to optimize the initial weight of the model, adjust the sensitivity of the model to different samples, and further improve the prediction accuracy. The experimental results show that the prediction results of this model are in good agreement with the test data of real propeller, and the calculation period is very short and the efficiency is high, which meets the requirement of real-time and accurate prediction of the open water performance of propeller.

The Prediction of Hydrodynamic Performance of Pinisi Ship

Pinisi ships are famous for their toughness across the ocean. The uniqueness of Pinisi is shipbuilding methods that are different without design engineering. The conditions present pinisi for tourist ships, problems have arisen recently, namely the number of Pinisi ship accidents. The main cause is bad water and technical factors. To improve safety and comfort, the aspect that needs to be studied hydrodynamic characteristics. The subject ship uses three samples of Pinisi ships produced by the Tanah Beru traditional shipyard. The hydrodynamic performance to be analyzed is hydrostatics, stability, resistance and ship motion, with several methods according to the respective standard to be analyzed. The shape of the pinisi hull is a rounded hull small coefficient block, and the largest change in hydrostatic parameters occurs at a draft of 0 meters to 0.25 meters. The resistance at a speed of 0-7 knots is relatively the same at every speed increase, but at speeds > 7 knots there is a change. RAO analysis for roll motion at a wave frequency of 1.5 – 1.75 rad/s for heading 90 degrees and for 45 degrees 3.65-3.80 rad/s. Heave motion occurs at a frequency of 4.25 rad/s – 4.4 rad/s with a wave direction of 0 degrees and a heading of 90 degrees smaller than the direction of the wave of 0 degrees. Evaluation of the stability arm, for variation KG critical, failed in 5/4H dan 1H in with B/T 3.43 to B/ T 5.00, while for the initial metacentric height parameter, all conditions still passed the criteria.

Multi-fidelity model and reduced-order method for comprehensive hydrodynamic performance optimization and prediction of JBC ship

The multi-fidelity Co-Kriging surrogate model can be applied to combine the accuracy advantage of high-fidelity sample evaluation with the efficiency advantage of low-fidelity sample evaluation. In this paper, the hull form optimization process for resistance and wake performance of a Japan bulk carrier (JBC) hull at design speed is given in detail, where the evaluation results from medium and coarse grids are regarded as the high- and low-fidelity data, respectively. 60 high-fidelity hydrodynamic evaluations have been done to construct the Kriging model, while the Co-Kriging model uses 30 high-fidelity and 60 low-fidelity evaluations with a 25% reduction of the total computation time. The optimization results show that, for the total drag, the Kriging-based optimal hull has a 4.57% reduction, while the Co-Kriging-based optimal hull has 5.67%; for the axial wake fraction reduction at the propeller disk, the Kriging-based optimal hull has a 7.20% reduction, while the Co-Kriging-based optimal hull has 10.37%. Furthermore, in the latter stage of hull form optimization, dimensionality reduction field learning can be performed to fully use the viscous-flow-based calculation results. An accurate and efficient viscous-flow-based wake field learning method is proposed based on the Kriging model and the Proper Orthogonal Decomposition (POD) method with qualitative and quantitative error analysis, which can guide the sensitivity analysis of the design variables, the selection of the design variables and spaces, and new flow field prediction for comprehensive hull form performance optimization.

Numerical study on transient four-quadrant hydrodynamic performance of cycloidal propellers

Aiming to investigate the transient four-quadrant hydrodynamics on blades under the circumferential motion of the steering center, an efficient three-dimensional (3D) model with half blades was established in this paper. The 3D model with half blades accounts for the hydrodynamic loss induced by the complicated mechanical structure, predicting the hydrodynamic performance of the high-load cycloidal propeller with high accuracy. On this basis, the open water manoeuvering performance of the cycloidal propellers in fully azimuth angle was simulated by Reynolds-averaged Navier-Stokes (RANS) solver, and the hydrodynamic loads and flow field characteristics were analyzed in detail. The research shows that the variation of azimuth angle φ induces the rapid response of hydrodynamic loads, which directly affects the direction of ship motion. Compared with φ = 0°, the increase in the azimuth angle of the steering center will enhance the negative impact of the inflow velocity on the wake flow field and the internal flow field within the blades. Additionally, the non-uniform flow in the main thrust direction leads to a significant increase in the undesired net lateral force. Our primary findings revealed in present paper should contribute to accurate prediction of hydrodynamic performance for high-load cycloidal propellers during maneuvering process.

Effects of transition turbulence modeling on the hydrodynamic performance prediction of a rim-driven thruster under different duct designs

The rim-driven thruster (RDT) is an innovative marine propulsion device. During the design process, scale models of RDTs are frequently used and also smaller sized units used in Underwater Remotely Operated Vehicles (ROVs) or Autonomous Underwater Vehicles (AUVs) are often likely to operate under conditions where the boundary layer on the surface of the propeller makes a transition from a laminar to a turbulent regime. Accurately resolving this transitional boundary layer can help improve the performance prediction of RDTs. Studies addressing this are scarce and hence the present work investigates the influence of transition turbulence modeling on the hydrodynamic performance prediction of an RDT with different duct configurations by means of computational fluid dynamics (CFD). The turbulence models employed in this study are the two-equation SST k−ω model and the four-equation γ−Reθ transition model. For this purpose, three duct designs are considered, notably two modified 19A and 37 ducts, and one symmetric duct design often seen in RDT designs. Numerical calculations are performed using ANSYS Fluent 19.1 whilst a verification and validation study is firstly carried out to ensure the accuracy of the numerical model. The results demonstrate that the γ−Reθ transition model can better capture the transitional flow on the blade’s surface, and substantial discrepancies are observed between both turbulence models with regard to the streamline patterns near the blades on the one hand and skin friction profiles on the other. The torque calculated using the transition model better fits the experimental data, suggesting that it is more suitable to estimate the RDT performance. Three RDT duct designs are simulated which enable different ways to guide the incoming flow and it is shown that they have an important influence on the propeller performance. The results of the open water performance of the three different duct profiles are presented and compared, along with detailed analyses of the flow fields.

Hydrodynamic numerical simulation and prediction of bionic fish based on computational fluid dynamics and multilayer perceptron

This paper proposes a prediction strategy for the hydrodynamic performance of bionic fish. The major challenges are meshing and building prediction model. The NACA0012 airfoil is used to replace the fish driven by the body and/or caudal fin (BCF), and a two-dimensional swimming geometric model is constructed. The geometric model is divided into hybrid meshes using the overset mesh method. The classical traveling wave model is studied using Matlab, and an improved self-propelled motion model is established. The hydrodynamic performance of the self-propelled model is numerically simulated based on computational fluid dynamics (CFD). In this strategy, the geometric model and the self-propelled motion model are integrated with user defined functions (UDF). The influences of the parameters such as inflow velocity, frequency, wavelength, and head fluctuation amplitude on the motion performance are studied. The results show that when inflow velocity is uniform, the self-propelled motion will eventually reach a quasi-steady state. According to the numerical simulation results, a hydrodynamic performance prediction model is established based on multilayer perceptron (MLP). The model is used to predict the performance of the optimized traveling wave parameters, and the error is within 3. The accuracy and generalization ability of the MLP prediction model is verified.

Prediction of steady hydrodynamic performance of pump jet propulsor considering vessel body influence

The actual working environment of a pump jet propulsor is formed under the joint action of the vessel and thruster. The disturbance created by the pump jet propulsor changes the flow field of the vessel body. And this changing flow field environment in turn affects the hydrodynamic performance of the pump jet propulsor. Therefore, a steady-state substitution relationship is formed between two systems. In this study, the vessel was regarded as a three-dimensional non-lifting body in an ideal fluid. A numerical model of the induced velocity field of the vessel by an arbitrary surface panel method was established. The resulting velocity field was combined with a numerical model for pump jet propulsor performance prediction, which accounts for the interaction between the vessel and the pump jet propulsor according to induced velocity. A method for the prediction of hydrodynamic performance of pump jet propulsor is thereby realised considering vessel body influence.

Comparison of computational methods for hydrodynamic performance prediction of oscillating marine propulsors

The biomimicry of fish fins has been suggested as an efficient and low-noise approach to propulsion for remotely operated and autonomous underwater vehicles. Propulsion of this type is achieved through the use of fin-like propulsors that undergo oscillatory motions. Two computational approaches of differing fidelity and computational space/time requirements have been used to calculate thrust and efficiency of oscillating marine propulsors in order to determine the region where each method is most appropriate for design applications. The higher fidelity and computational cost method is an unsteady Navier–Stokes approach. The lower fidelity and computational cost method is a lifting-surface potential flow method supplemented with strip theory to account for viscous effects. In comparison with two-dimensional experimental results, both methods were able to accurately capture magnitudes and trends in light to moderate thrust conditions (CT<0.7) assuming no dynamic stall occurs. Under these operating conditions, computational savings for three-dimensional analysis on the order of 5,000 processor-hours are achieved by using the lower fidelity method, making it the more appropriate choice for design applications. At high thrust conditions (CT>0.7) and in conditions where dynamic stall effects are prevalent (αmax>20∘, low Strouhal numbers), the higher fidelity method is required to achieve sufficient predictive accuracy.

Prediction of hydrodynamic performance of pump jet propulsor considering the effect of gap flow model

There is a strong gap flow exists between the pump rotor tip and the inside of the duct of the pump jet propulsor. To predict the hydrodynamic performance of a pump jet propulsor more accurately, considering the influence of fluid viscosity in the gap area, a gap flow model suitable for a pump jet propulsor is proposed. Through an analysis of the hydrodynamic performance of the pump jet propulsor, it is determined that it is optimal for the gap height to be 0.98–1.0 times of the complete gap height, Additionally, it is verified that the flux coefficient (CQ) range of 0.8–0.84, which can accurately simulate the energy loss of the fluid at the gap flow, is reasonable. Moreover, through a comparative analysis of the hydrodynamic performance, pressure, and circulation distribution of the pump jet propulsor, it is found that, when the influence of the gap flow model is considered, the wall pressure and circulation distribution of the rotor blade and duct are more consistent with the calculation results of viscous flow. In addition, the introduction of the gap flow model only improves the prediction accuracy of the hydrodynamic performance of the pump jet propulsor.

Machine learning-based performance analysis of two-axial-groove hydrodynamic journal bearings

The precise prediction of a rotor against instability is needed for avoiding the degradation or failure of the system’s performance due to the parametric variabilities of a bearing system. In general, the design of the journal bearing is framed based on the deterministic theoretical analysis. To map the precise prediction of hydrodynamic performance, it is needed to include the uncertain effect of input parameters on the output behavior of the journal bearing. This paper presents the uncertain hydrodynamic analysis of a two-axial-groove journal bearing including randomness in bearing oil viscosity and supply pressure. To simulate the uncertainty in the input parameters, the Monte Carlo simulation is carried out. A support vector machine is employed as a metamodel to increase the computational efficiency. Both individual and compound effects of uncertainties in the input parameters are studied to quantify their effect on the steady-state and dynamic characteristics of the bearing.

Hydrodynamic Performance Prediction of Stepped Planing Craft Using CFD and ANNs

In the present paper, the hydrodynamic performance of stepped planing craft is investigated by computational fluid dynamics (CFD) analysis. For this purpose, the hydrodynamic resistances of without step, one-step, and two-step hulls of Cougar planing craft are evaluated under different distances of the second step and LCG from aft, weight loadings, and Froude numbers (Fr). Our CFD results are appropriately validated against our conducted experimental test in National Iranians Marine Laboratory (NIMALA), Tehran, Iran. Then, the hydrodynamic resistance of intended planing crafts under various geometrical and physical conditions is predicted using artificial neural networks (ANNs). CFD analysis shows two different trends in the growth rate of resistance to weight ratio. So that, using steps for planing craft increases the resistance to weight ratio at lower Fr and decreases it at higher Fr. Additionally, by the increase of the distance between two steps, the resistance to weight ratio is decreased and the porpoising phenomenon is delayed. Furthermore, we obtained the maximum mean square error of ANNs output in the prediction of resistance to weight ratio equal to 0.0027. Finally, the predictive equation is suggested for the resistance to weight ratio of stepped planing craft according to weights and bias of designed ANNs.

Numerical Prediction of Hydrodynamic Performance of Planing Trimaran with a Wave-Piercing Bow

The central hull is the most important structure in the planing trimaran. In order to gain insight into the relationship between hydrodynamic performance and main hull shape, experimental tests and numerical simulations were carried out for volume Froude Number (FrΔ) ranging from 1.31 to 4.98. Dynamic sinkage and trim in the Dynamic Fluid Body Interaction (DFBI) six-degree-of-freedom model were considered. A validation study carried out by comparison of experimental test results with numerical results showed good consistency. To analyze the process of tunnel penetration and pressure change at the bottom of the boat, numerical simulation results for free surface, bottom streamline, and pressure distribution around the hull are given. A large triangular high-pressure area was observed in the front of the main hull for all volume Froude numbers. Consequently, the central drainage body, in reference to the profile of single planing craft with distinctive resistance performance, was redesigned into a wave-piercing shape. Total resistance, sinkage, and trim angle of the new model were then predicted by numerical method. The results show that the central drainage body has a significant impact on the hydrodynamic performance of the planing trimaran. Furthermore, the wave-piercing shaped main hull has a drag reduction effect.

A reliable simulation for hydrodynamic performance prediction of surface-piercing propellers using URANS method

Surface Piercing Propellers (SPPs) are a particular kind of propellers which are partially submerged operating at the interface of air and water. They are more efficient than submerged propellers for the propulsion system of high-speed crafts because of larger propeller diameter, replacing cavitation with ventilation, decreasing the torque and higher efficiency. This study presents a reliable numerical simulation to predict SPP performance using Unsteady Reynolds-Averaged Navier–Stokes (URANS) method. A numerical study on 841-B SPP is performed in open water condition. The free surface is modeled by Volume of Fluid (VOF) approach and the sliding mesh technique is implemented to model the propeller rotational motion. The sliding mesh allows capturing the process of water entry and water exit of blades. The propeller hydrodynamic characteristics, the ventilation pattern and the time history of blade loads are validated through the comparison with available experimental data. For the studied case, it was found that the common grid independence study approach is not sufficient. The grid should be elaborately generated fine enough based on the flow pattern and turbulence modeling parameters in regions near the blade's tip, trailing and leading edges and over the suction side. Details of URANS simulations including optimal time-step size based on propeller revolution rate and the required number of propeller revolutions for periodical results are presented and discussed.

Comparative Analysis of Hydrodynamic Performance of Propeller Under Different Turbulence Models

In order to study the applicability of different turbulence models in the prediction of propeller hydrodynamic performance, computational fluid dynamics software CFX was used to simulate the thrust coefficient, torque coefficient and efficiency of VP1304 propeller under specific viscous flow field conditions by using k - ε models, k - ω models, SST models and RSM models respectively. The prediction results from the four turbulence models are compared with the experimental data of controlled pitch propeller VP1304 published by SVA Potsdam. It is concluded that the simulation prediction of performance due to the RSM model is the most accurate, Merits and demerits of RSM model is analyzed.

Improved Hydrodynamic Analysis of 3-D Hydrofoil and Marine Propeller Using the Potential Panel Method Based on B-Spline Scheme

In this paper, the hydrodynamic performance of lift-body marine propellers and hydrofoils is analyzed using a B-spline potential-based panel method. The potential panel method, based on a combination of two singularity elements, is proposed, and a B-spline curve interpolation method is integrated with the interpolation of the corner points and collocation points to ensure accuracy and continuity of the interpolation points. The B-spline interpolation is used for the distribution of the singularity elements on a complex surface to ensure continuity of the results for the intensity of the singular points and to reduce the possibility of abrupt changes in the surface velocity potential to a certain extent. A conventional cubic spline method is also implemented as a comparison of the proposed method. The surface pressure coefficient and lift the performance of 2-D and 3-D hydrofoils of sweepback and dihedral type with different aspect ratios are analyzed to verify the rationality and feasibility of the present method. The surface pressure distribution and coefficients of thrust and torque are calculated for different marine propellers and compared with the experimental data. A parametric study on the propeller wake model was carried out. The validated results show that it is practical to improve the accuracy of hydrodynamic performance prediction using the improved potential panel method proposed.

Study of the hydrodynamic performance prediction method for a horizontal-axis tidal current turbine with coupled rotation and surging motion

For the fast prediction of the hydrodynamic characteristics of a floating horizontal-axis tidal current turbine (HATT) with coupled rotation and surging motion, this study applies the CFD method to simulate the coupled rotation and surging motion, and obtains the axial force and axial torque coefficients at different current velocities. According to the CFD simulation data, the constant force, damping, and added mass coefficients can be obtained by least-squares fitting. The approximate calculation formulas of the axial force and axial torque coefficients of a turbine with coupled rotation and surging motion are summarized by analyzing the constant force, damping, and added mass coefficients under different surge frequencies and amplitudes, turbine rotation speeds, and current velocities. The results demonstrate the following: 1) the frequency and amplitude of the surge have little impact on the damping coefficient, which is positively proportional to the tip speed ratio; 2) when predicting the hydrodynamic load of a turbine with coupled rotation and surging motion, the added mass coefficient can be neglected, and only the influence of the constant terms of the constant force and the damping coefficients are needed. The approximate calculation formula obtained in this study can effectively predict the hydrodynamic load of the HATT.

Review and historical overview of experimental facilities used in hull coating hydrodynamic tests

The prediction of hydrodynamic performance of hull coatings with different surface conditions is a challenging task. Moreover, with the emergence of new prototype coatings that are relatively smooth in terms of roughness characteristics, the accurate estimation of their drag is particularly important, as this will enable a good grading of drag reducing benefits of coatings. In the context of coating studies, the experimental methods are considered as the backbone and results obtained from experimental facilities with the required performance will enable accurate scaling of test results to full-scale ship results. Although numerical simulations like computational fluid dynamics have acquired the level of accuracy good enough to replace some of the systematic model testing used for ship design optimization, it is still not evident whether the simulations will be able to replicate the physical reality such as coating type, its roughness and biofilms accurate enough to enable predictions of the power requirements for ships. Therefore, this article gives insight into various coating hydrodynamic testing facilities and methods that are capable of measuring drag characteristics of coatings. The work highlights the details of each method and identifies the concepts and parameters needed to describe, implement and analyze hydrodynamic coating drag measurements. This article also summarizes the merits and demerits of each type of facility based on reports and studies reported in open literature. Finally, the authors propose a recommendation that can be incorporated into the design of the new hydrodynamic facility.