Surface-piercing Propeller Research Articles

Investigating the growth of surface crack and high cycle fatigue in surface-piercing propeller

In this study, the progress of surface crack and high cycle fatigue of the surface piercing propellers (SPPs) are investigated numerically using the finite element method. The cyclic load is calculated from the hydrodynamic pressure on the blade by simulating the fluid around the blade using the computational fluid dynamics software STAR-CCM+. The initial cracks are assumed to be created near the blade root. The fatigue life is calculated from the Paris-Erdogan equation. The results show that the crack close to the root has a shorter life and the stresses at the crack front depend on the blade-water interaction duration.

Optimal section design of surface piercing propeller using artificial neural networks algorithm

ABSTRACT Section optimisation of a surface piercing propeller (SPP) with the combination of artificial neural networks and NSGA II algorithm is investigated in this research. The blade section have a sharp leading edge and thick trailing edge. The geometry of this propeller is mostly designed experimentally, and comprehensive studies have not been performed to examine its parameters. In this regard, the propeller's parametric geometry is designed based on the cubic B-spline method. The SPP was first fabricated and tested, and the simulated data of the tested propeller were verified. Then, limited data were extracted according to a verified CFD model based on which the ANN was trained. The ANN results indicated the mean square error of the trained network is 3e-9, 1e-7, and 1e-7 for training, validation, and test data, respectively. comparing the optimisation and experimental results showed a relative error amounting to 3.5% in thrust and 4.24% in torque.

Improving hydrodynamic performance of surface piercing propeller through trailing-edge optimization

Automated optimization is increasingly used in engineering applications. In this study, RANS-based CFD, the NSGA II algorithm, and Kriging were used to optimize a section of a marine surface piercing Propeller (SPP) set. The hydrodynamic performance of the SPP is also determined using the CFD tool. The optimization process involves the NSGA II algorithm in combination with the Kriging method. The optimized geometry is simulated using the CFD tool. Then, the obtained results are added to the initial population and the optimization is repeated in the next iteration. Thus, fewer simulations were required because the addition of the data with the surrogate method was accompanied by a good distribution, using surface methods for the replacement of the main part in the required calculations. As shown, the trailing edge optimization can improve Kt in J = 1 by almost 10.5%, and Kq changes by almost 12%, so this method can be used as an optimization package for similar problems.

Position parameters optimization of surface piercing propeller by artificial neural network

Improving the performance of surface-piercing propellers is achieved by investigating the influential factors. In this study, Artificial Neural Network is used to identify nonlinear models for estimating various phenomena. Non-Dominated Sorting Genetic Algorithm II is considered as an optimization tool. In this study, in order to optimize the position parameters, including the immersion ratio, angle of attack, and yaw angle, data from experimental tests at the HYDROTECH center of IUST were collected as the initial data field for the generation of training data by the artificial neural network, then experimental tests were implemented in the position of the Non-Dominated Sorting Genetic Algorithm II proposed as the output, and the results were compared. The Artificial Neural Network results showed that the mean error of the trained verified and test data is 7.5e−5, 1e−4, and 1e−4, respectively. Comparing the experimental and optimization results, the thrust coefficient showed a relative error of 9.7%, while the torque coefficient showed a relative error of 7.5%, this algorithm can be used as a cost-effective, time-saving method for a similar problem.

Investigating the Effects of Blockage Ratio on the Performance of a Surface-piercing Propeller in Free Surface Water Tunnel Tests

This paper investigates the effect of the immersion ratio parameter on the hydrodynamic performance of three surface-piercing propellers with diameters of 0.125, 0.132 and 0.140m at different advancing speeds. Experimental tests have been carried out in the free surface water tunnel of the Babol Noshirvani University of Technology. The results showed that the maximum thrust coefficient of three propellers occurs in the velocity range of 3-3.5 m/s. This interval represents the transition area of the three propellers. Also, the effect of the blockage ratio on the hydrodynamic coefficients of three propellers relative to the advance coefficient has been studied. By increasing the immersion depth raises the propeller's wet surface and increases the thrust and torque hydrodynamic coefficients. However, growing the propeller's diameter to 0.140m causes the effect of the blockage ratio parameter by increasing the immersion and the propeller's torque experiences a decreasing trend. Therefore, maximum propeller efficiency value with diameter 0.140m in immersion ratio 0.60 and 0.70, incresing 38% and 44%, respectively; relative to other proepllers. Also, the curve of the efficiency gradient of three propellers in the optimum immersion ratio of 0.40 compared to the advancing coefficient shows that the maximum efficiency gradient occurs in the range of 0.7 to 0.9.

Effect of Aeration Flow Rate on Improvement of Surface-Piercing Propellers Performance

The Surface-Piercing propeller blades move in and out of the water with each rotation to reduce the immersion depth from the free surface to the shaft axis . The main challenge facing surface piercing propellers, however, is their lower efficiency at lower advance velocity, compared to other propulsion systems. To improve the performance of the propeller, an aeration mechanism was used at low advance velocities so that air was blown to the surface behind the propeller. Experimental studies were carried out on a propeller model in the Hydrotech laboratory of the Iran University of Science and Technology, and the effect of the injected air velocity ratio was evaluated at different immersion ratios. Based on the results obtained, it was concluded that an increase in the injected air velocity ratio could only promote thrust enhancement under specific conditions. For immersion ratios of 0.85 and more, as well as advance coefficients of 0.6 and more, a change in the velocity ratio of the injected air could not lead to an improvement in thrust. The best performance was identified with an immersion ratio of 0.4 and an advance coefficient of 0.4, while thrust performance at below or above of this condition declined .

The study on the scaling effects in the surface piercing propeller

Surface Piercing Propellers (SPPs) are widely used in high-speed crafts. These types of propellers can work at high rotational speeds and in a turbulent environment with high efficiency. One of the most widely used methods in estimating the performance of conventional marine propellers is the use of model testing in towing tank or cavitation tunnel. These propellers' open water hydrodynamic performance can be checked in a laboratory test before being made at full scale. According to the lack of similarity between the model and the full scale in this type of propeller, the flow regime is not the same as the scale values of the model, which leads to the difference in the hydrodynamic characteristics estimate. Many scaling techniques have been created to correct the measured thrust and torque values in model scale for conventional propellers. But, SPPs operate in two different phases, and traditional scaling approaches may not be applied to these types of propellers. For this purpose, four scales of a 5-bladed SPP with available experimental data were investigated using RANS equations and applying the VOF function to the free surface. The sliding mesh technique and the K-omega turbulence model are used in grid discretization and calculation of the Reynolds stress. The numerical method was validated by the cavitation tunnel test, and the effects of scale checked by numerical estimates and conventional methods. The results of scale effects indicate that traditional approaches are unsuitable for SPPs. In detail, an examination of the pressure and shear components of the hydrodynamic coefficients shows that they are affected by the pressure component induced by ventilation pattern. Finally, the thrust, torque coefficient, and efficiency were studied by changing the Different variables and presented the results.

Experimental evaluation of the effect of positioning and operating parameters on the performance of a surface-piercing propeller

Today, surface-piercing propellers have been recognized as a suitable choice for higher speeds. Yet, the development of design algorithms for such has been challenged by insufficient knowledge about the parameters affecting their performance. For this reason, developing experimental data and studying the influence of various parameters on their performance is crucial. Aiming to develop experimental knowledge of these propellers, this study investigates the impact of position parameters and Froude Number on model test results of a custom-designed propeller. Moreover, ventilation wake development at different Froude numbers was studied. The experimental results pointed to the favorable impact of increased immersion ratio on propeller's thrust, a positive impact of increasing the inclination angle by 6° on higher thrust and efficiency in the advance direction, and a slight increase of thrust with higher yaw angles up to 10°. The propeller's lateral forces were also extracted in different positions and operational conditions to identify the propeller's behavior and design the required shaft and supports. Finally, regression equations for projecting hydrodynamic coefficients used at the design phase were compared and verified by the experimental results. The results pointed to the insufficient precision of this model for estimating the hydrodynamic coefficients affecting the propeller.

Experimental and numerical investigation of hydrodynamic performance of a new surface piercing propeller family

Today, passenger and racing boats increasingly utilize surface-piercing propellers. This type of propeller operates in two distinct phases of water and air simultaneously. As a result, this propeller type has additional characteristics that must be investigated separately from conventional propellers. A new family of surface piercing propellers was investigated using experimental and numerical methods. The family consisted of five propeller models with varying geometric features operating at an immersion ratio of 0.7. Experiments were conducted in the Sharif University of Technology's hydrodynamic group's cavitation tunnel. Additionally, using Star-CCM + software, the numerical simulation was performed using the RANS method for implicit unsteady flow with a sliding mesh technique in free surface conditions. The results indicate that by increasing the pitch ratio from 1.074 to 1.61, the critical advance coefficient value, which is in the range of 0.4–0.6, moves to 0.8–1 interval. Also, the efficiency enhances by 14% while raising the pitch ratio. The amplitude of force and moment fluctuation components increases at higher than 0.5 values of the advance coefficient by increasing pitch ratios. The expanded area grows proportional to an increased number of blades and as a result, the thrust and torque coefficients increase, but the efficiency does not improve significantly. Furthermore, the fluctuation amplitude of forces and moments applied to the key blade increases up to the critical advance coefficient in all models and then decreases for above critical values.

Regression Modeling of surface piercing propeller performance based on trailing edge geometrical parameters using CFD method

The geometry of the surface piercing propeller has been designed experimentally, and no comprehensive studies are available to identify the influential parameters to attain systematic formulations. This study aims to evaluate the feasibility of presenting systematic relations between the geometric parameters of the blade section and its hydrodynamic characteristics through combined methods of computational fluid dynamics and design of experiments. In this regard, the propeller's parametric geometry is designed based on the cubic B-spline method. Hence, a series of SPPs with different trailing edges is generated according to the coordinates of control points based on the D-optimal response surface methodology. The propeller performance was investigated using URANS numerical simulation method in accordance with the VOF method and sliding mesh technique.ANOVA analyses of the quadratic regression models of hydrodynamic coefficients in terms of edge height (Y) and protrusion length (X), based on a 95% confidence interval, indicate these models have prediction adequacy of more than 90%. The main factor (X) is the only significant factor in both models. Increasing it will reduce the hydrodynamic coefficients. As a result, trailing edge variations can significantly affect torque and thrust coefficients by up to 40%, while efficiency changes are about 7%.

Numerical Investigation of the Effect of Trailing Edge Shape on Surface-Piercing Propeller Performance

One of the main challenges in the development of surface-piercing propellers is to identify the effects of geometric parameters on the performance. The main geometric difference between SPP and conventional propellers is its blade section shape. The blade section is of super cavity type with a sharp leading edge and thick trailing edge. The geometry of this propeller is mostly designed experimentally, and comprehensive studies have not been performed to examine its parameters. Therefore, this research aims to investigate the effect of trailing edge shape on ventilation cavity development and SPP performance. The performance of a series of HL-tx propellers consisting of 6 propellers with different trailing edge shapes has been studied numerically. Numerical simulation of geometries was performed using URANS method coupled with the VOF method to capture the interface of fluids. The sliding mesh technique was also used to simulate the rotation of SPPs in transition mode. The results of the simulation method are in good agreement with the experimental data. As the results indicated, there was a 40% change in thrust and torque coefficients due to the trailing edge shape changes, which is a significant effect. However, changes in efficiency are about 7%. Meanwhile, the results revealed SPPs with a larger angle to the chord line and shorter height have better performance and ventilation cover behind the blade.

Performance improvement of surface piercing propeller at low advance coefficients by aeration

Surface piercing propeller (SPP) is a type of super-cavitating propellers which with ventilation on the blades have suitable performance at water-air interface. These propellers provide perfect ventilation behind the blade, which effectively controls cavitation/aeriation and improves trust performance at operational condition. Even if at high speeds the SPPs have higher efficiency compared to the conventional propellers and water jets, the main challenge is their lower efficiency than other propulsion systems, at a lower speed which can affects the starting phase of high-speed crafts. In fact, there is a lack of research in studies on these propellers which concern the improvement of their performance at low speed. In the present studies, an aeration mechanism is investigated so that air is injected upstream in order to improve performance of the propeller. The design of the experiment (DOE) is carried out on a SPP model to perform performance tests in open water conditions using the SPP flow loop mechanism at Hydrotech (Institute of Applied Hydrodynamics and Marine Technologies, Iran University of Science and Technology). The effects of the horizontal distances (α) and vertical distances (β) between the ventilation point and the location of the propeller are presented in the form of non-dimensional ventilation immersion ratios β/α. For different propeller immersion ratios, ventilation immersion ratios and advance coefficients, the thrust coefficient for different cases was measured and compared to unventilated conditions. The achievements of the present research are different performance curves about thrust coefficient which illustrate a good correlation between propeller performance and aeration at different propeller immersion ratios. The maximum thrust coefficient improvement is around 100% which can achieve at I=0.25, β/α=0.05 and J=0.4. As propeller immersion ratio I increases, region with improved performance shifts towards higher values of advance coefficient J.

Numerical study of the parameters affecting the formation and growth of ventilation in a surface-piercing propeller

The surface-piercing propellers (SPPs) are a specific type of supercavitating propellers that have higher efficiencies at high advance speeds. The SPPs operate on a free surface, so due to the ventilation and air suction into the water, the pressure of the suction surface of the blade approaches atmospheric pressure. Given the importance of better understanding this phenomenon, in this research, the formation and development of ventilation in an SPP5.74 5-blade SPP is numerically investigated by defining proper geometrical and physical parameters. The finite volume method (FVM) has been implemented to numerical modeling and simulating the free surface carried out by the volume of fluid (VOF) two-phase model. The numerical results have compared with the experimental data with similar conditions due to validating the simulation. Also, the simulations were carried out in six different advance coefficients ranges from 0.44 to 0.94. In the results section, different parameters are introduced, including the length and thickness of the ventilation zone, the influence of the advance coefficient on the physics of the ventilation phenomenon have been evaluated in various propeller radius ratios. The results show that in the suction surface and the points where ventilation starts, the pressure tends to the atmospheric pressure, by reducing the advance coefficient, the thickness, and the length of the ventilation zone increase, in this condition, the ventilation zone moves towards the leading edge. In constant advance coefficients, increasing the radius ratio reduces the thickness and the length of the ventilation zone. In high radius ratios and near the tip of the blade, the ventilation is limited to the trailing edge. Moreover, the analysis of the pressure coefficients shows that in the ventilation zone, the pressure coefficient is zero, while in the other areas, it ranges from 0 to 1. With larger advance coefficients, the areas with the zero pressure coefficient tend towards the trailing edge.

A review on the Surface-Piercing Propeller: Challenges and opportunities

The application of surface-piercing propeller (SPP) has been widely used in high-speed crafts due to possessing many favorable features. Due to the information gaps in the design of SPP, researchers have made great efforts to conduct hydrodynamic analysis of these propulsion systems. Despite the previous studies, there is still a considerable shortage in literature. In this article, a comprehensive review has been carried out on the experimental, theoretical, and experimental–theoretical studies in the field of SPP to introduce the strengths, limitations, and gaps in the previous research. The results of previous studies have also been presented in the form of benchmarking tables and statistical figures. Investigations have proved the inability of the numerical methods to simulate SPP. In recent years, the most precise methods of analyzing complex flows around SPP have been the computational fluid dynamics methods. The most suitable computational fluid dynamics method is the Reynolds-averaged Navier–Stokes method. Moreover, despite the heavy costs of experiments, the experimental approach is still the most reliable way of understanding the flow phenomena, studying the time-dependent dynamic behavior of propellers, and determining the hydrodynamic coefficients of thrust and torque. It can also serve to develop the numerical methods for comparing the results and reducing the errors of semi-experimental equations. Therefore, one of the primary objectives of future studies will be the comprehensive experimental analysis of various propeller blade profiles considering the effect of the variations of the trailing edge angle and the effects of the parameters influencing SPP, especially the shaft inclination angle.

Numerical investigation on the effect of shaft inclination angle on hydrodynamic characteristics of a surface-piercing propeller

The global demand for fast sea transportation has led to an ongoing development of high-speed vessels and surface-piercing propeller, as a high performance propulsor, has played an important role in this development. However, the complexity of the two-phase flow field around the propeller has made its numerical analysis enough challenging. The performance of surface-piercing propeller depends on propeller geometric parameters and flow conditions at propeller disk. Among these parameters, shaft inclination angle is a key parameter which significantly affects the flow conditions at propeller disk. In this paper, RANS computations were applied to investigate the unsteady flow around an optimized surface-pricing propeller in various shaft inclination angles. Likewise, the homogeneous Eulerian multiphase model was employed along with Volume of Fluid model to solve the two-phase flow field equations. Rotational motion of the propeller was simulated by CFX sliding mesh technique. The effect of shaft inclination angle on the hydrodynamic coefficients of the propeller and the behavior of the fluid flow around the propeller key blade are among the principal objectives clarified in this study. As the results indicated, the propeller thrust and torque coefficients were gone up with an increase in the shaft inclination angle. Moreover, as the shaft inclination angle increases, the maximum thrust and torque coefficients of the key blade take place at the lower rotation angles. Additionally, it was revealed that the effect of shaft inclination angle on the torque coefficient of the key blade depends on the angular position of the key blade. Furthermore, the flow patterns around the propeller were predicted in different shaft inclination angles. In order to verify the accuracy of the numerical method used in this paper, numerical simulations were run on SPP-841B propeller with available experimental data. The comparison between the simulated and measured SPP-841B open characteristics as well as the ventilation pattern of the key blade indicates a reasonable agreement with the experimental data.

Boundary element method development for modeling of two-phase flow around the surface piercing propeller with regard to cross-flow effect

Boundary element method development for modeling of two-phase flow around the surface piercing propeller with regard to cross-flow effect

Hydrodynamic characteristic curves and behavior of flow around a surface-piercing propeller using computational fluid dynamics based on FVM

In this study, unsteady Reynolds-Averaged Navier-Stokes computations based on a finite volume method was used to investigate the behavior of fluid flow around an optimized surface-piercing propeller (special blade section) operating at immersion ratio of 0.3. Sliding mesh technique was applied to simulate rotational motion of the propeller. Homogenous Eulerian multiphase model including volume of fluid method was employed to solve two-phase flow field equations. As the results showed, the highest thrust and efficiency of the key blade achieved at the regions near the rotation angle of 180°. Additionally, total thrust of the blade section (0.7R) was decreased with increase of advance coefficient. In a specified advance coefficient, from rotation angle of 90°–180°, total thrust of the blade section was increased and maximum local thrust occurred at a location close to the leading edge whereas from rotation angle of 180°–270°, total thrust of the blade section was dropped and maximum local thrust position got away from the leading edge. To validate the numerical results, experimental data of SPP-841B propeller was used. Comparison between numerically simulated results, measured open water characteristics of SPP-841B and ventilation pattern of the key blade revealed an acceptable level of conformity.

Numerical Analysis on the Effect of Artificial Ventilated Pipe Diameter on Hydrodynamic Performance of a Surface-Piercing Propeller

Under the condition of large water immersion, surface-piercing propellers are inclined to be heavy loaded. In order to improve the hydrodynamic performance of the surface-piercing propeller, the installation of a vent pipe in front of a propeller disc is more widely used in the propulsion device of high speed planning crafts. Based on computational fluid dynamics (CFD) method, this paper studied the influence of diverse vent pipe diameters on hydrodynamic performance of the surface-piercing propeller under full water immersion conditions. The numerical results show that, with the increase of vent pipe diameters, the thrust and torque of the surface-piercing propeller decrease after ventilation, and the efficiency of the propeller increases rapidly; the low pressure area near the back root of the blade becomes smaller and smaller gradually; and the peak of periodic vibration of thrust and torque can be effectively reduced. The numerical results demonstrate that the installation of artificial vent pipe effectively improves the hydrodynamic performance of surface piercing propeller in the field of high speed crafts, and the increase of artificial vent pipe diameter plays an active role in the propulsion efficiency of the surface-piercing propeller.

Numerical investigation of the immersion ratio effects on ventilation phenomenon and also the performance of a surface piercing propeller

Surface Piercing Propellers (SPP) show high efficiency at high advance speeds. Regarding operational conditions, this kind of propellers generate an air layer when entering the water due to the rotation of the propeller; this phenomenon is called ventilation. The ventilation phenomenon divided into some mechanism with respect to air cavity length on the propeller surface; among them are partially ventilation mechanism and fully ventilation mechanism which has great importance. In this study, using numerical simulation, we have investigated ventilation patterns and also the performance of a five-blade SPP propeller (SPP 5.74) at immersion ratio of 33, 40, 50and 70% respectively. We used Sliding Mesh Technique for modeling. Also, we applied the volume of fluid method to simulate the open surface pattern. To validate numerical results, the four-blade propeller, 841-B was simulated, and then the results of thrust and torque coefficients compared with Olofsson experimental results and validated accordingly. The findings indicate that the maximum value for thrust and torque coefficient would occur at immersion ratio of 70% and the maximum propeller efficiency occurs at immersion ratio of 33% and advance coefficient of 1.1; Moreover, the critical advance coefficient (at the partially and the fully ventilation boundary) increases by a reduction in immersion ratio, so that critical advance coefficients are 0.6 and 0.76, respectively at immersion ratios of 70 and 33%. Meanwhile, as advance coefficient increases, length of ventilation zone will decrease, and consequently the propeller will be laid on partial ventilation zone.

Experimental study of immersion ratio and shaft inclination angle in the performance of a surface-piercing propeller

Abstract. Surface-piercing propellers have been widely used in light and high-speed vessels because of their superior performance. Experimental study of these propellers is one of the most reliable and accurate ways which can provide details about the performance and effect of different design parameters on the performance of the surface-piercing propellers. In this research, a five-blade surface-piercing propeller was tested in the free surface water tunnel of Babol Noshirvani University of Technology in order to expand the available experimental data and database for future engineering designs. The effects of immersion ratio and shaft inclination angle on the propeller's efficiency and hydrodynamic coefficients were examined. A free surface water tunnel and a calibrated dynamometer with the measurability of the thrust forces and the torque of a propeller were used for this purpose. Comparing the obtained results with the existing semi-experimental equations shows that the equations presented in various geometric conditions are not accurate enough, and developing the existing database is necessary. The details of the obtained results showed that the hydrodynamic coefficients of the thrust and torque increased by increasing the immersion ratio, but the coefficient of hydrodynamic thrust and efficiency reduced. The results also indicated that the coefficient of torque increased by increasing the shaft inclination angle. The highest efficiency of the propeller was achieved in the range of 40 %–50 % immersion ratios at all angles of shaft inclination. For all immersion ratios, the maximum and minimum efficiencies were obtained at 0 and 15 shaft inclination angles, respectively. The best efficiency of the propeller was at 50 % immersion ratio and zero shaft inclination angle.