scholarly journals Efficacy Analysis of Thickness and Camber Size of Cross Section of the Stator on Hydrodynamic Parameters in Linear Jet Propulsion System

2020 ◽  
Vol 2020 ◽  
pp. 1-17 ◽  
Author(s):  
Negin Donyavizadeh ◽  
Parviz Ghadimi
Keyword(s):  
Cross Section ◽  
High Speed ◽  
Pressure Coefficient ◽  
Propulsion System ◽  
Hydrodynamic Performance ◽  
Foil Thickness ◽  
Jet Propulsion ◽  
Efficacy Analysis ◽  
Ansys Cfx ◽  
Thrust And Torque

The linear jet propulsion system, unlike pump-jets which are widely used in underwater bodies, is installed inside a tunnel under the vessel and can be used for high-speed crafts, tugs, and service boats. However, this system has not received adequate attention by researchers, which is the subject of the current study. In the present paper, hydrodynamic performance of the linear jet propulsion system is numerically investigated. Accordingly, the Ansys-CFX software is utilized and RANS equations are solved using the SST turbulent model. The results of the proposed numerical model, in the form of thrust and torque coefficient as well as efficiency, are compared with available experimental data for a ducted propeller, and good compliance is achieved. Considering the importance of stator cross section on the performance of the linear jet propulsion system, the influence of thickness and camber size of the stator on linear jet propulsion systems are examined. Based on the numerical findings, it is determined that at constant advance ratio, with increasing thickness of stator, the efficiency increases. It is also observed that as the span length increases, the maximum and minimum of the pressure coefficient increase for different thicknesses. Furthermore, it is seen that positive and negative pressure coefficients decrease with an increase in foil thickness.

Numerical investigation of the effect of tip clearance on hydrodynamic performance of the linear jet propulsion system and vortex generation behind the rotor

2020 ◽  
pp. 095440622095249
Author(s):  
Negin Donyavizadeh ◽  
Parviz Ghadimi
Keyword(s):  
Leading Edge ◽  
Propulsion System ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Hydrodynamic Performance ◽  
Vortex Generation ◽  
Tip Leakage Vortex ◽  
Jet Propulsion ◽  
Tip Leakage ◽  
Thrust And Torque

Linear Jet system which has a stator in addition to a rotor combines the best elements of two existing technologies of conventional screw propellers and water jets. In designing this propulsion system, tip clearance plays an essential role, since it causes the appearance of tip vortex that leads to a further loss in efficiency and a probability of cavitation phenomenon. Due to lack of any study in this regard, it is thus necessary to study tip clearance to find the appropriate geometry for linear jet propulsion system. In the current paper, hydrodynamic performance of linear jet propulsion system is numerically investigated. Accordingly, Ansys-CFX software is utilized and RANS unsteady equations are solved using SST turbulent model. Results of the proposed numerical model, in the form of thrust and torque coefficient as well as efficiency, are compared with available experimental data for a ducted propeller. It is concluded that most of the errors at various advance ratios for thrust and torque coefficients are less than 3% and relatively good agreement is observed. Hydrodynamic investigation involves five different sizes of tip clearance (2.5 to 10% of the rotor diameter). Simulation results indicate that thrust and torque coefficients decreases about 10% and 8% respectively, at the same advance coefficient (J) with an increase in tip clearance. Effects of tip clearance on tip-separation vortex and tip leakage vortex are also examined. At about 20% of chord length from the leading edge, separation occurs. As tip clearance size increases, the tip-leakage vortex also increases. At different advance ratios and higher tip clearance, an increase in vortex and a sudden decrease in thrust is generated by the propeller. By changing the time about 0.8 of the rotor periods, the evolution of the vortex generation behind the rotor at the tip of the blade is clearly observed.

scholarly journals Utilization of Open-Source OpenFOAM Code to Examine the Hydrodynamic Characteristics of a Linear Jet Propulsion System with or without Stator in Bollard Pull Condition

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Parviz Ghadimi ◽  
Negin Donyavizadeh ◽  
Pouria Taghikhani
Keyword(s):  
High Speed ◽  
Water Jet ◽  
Propulsion System ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Propulsion Systems ◽  
Thrust Coefficient ◽  
Jet Propulsion ◽  
Marine Industry ◽  
Total Thrust

With the development of high-speed crafts, new propulsion systems are introduced into the marine industry. One of the new propulsion systems is linear jet which is similar to pump jet and has a rotor, a stator, and a duct. The main difference between this system and pump jet is the placement of linear jet system under the hull body and inside a tunnel. Since this system, like a water jet, is inside the tunnel, the design idea of this system is a combination of a water jet and pump jet. In this paper, hydrodynamic performance of linear jet propulsion system is numerically investigated. To this end, the OpenFOAM software is utilized and RANS steady equations are solved using a k - ε turbulent model. The linear jet geometry is produced by assembling a Kaplan rotor, stator with a NACA 5505 cross section, and a decelerating duct. The results of numerical solution in the form of thrust, torque coefficient, and efficiency are compared with available experimental data for a ducted propeller, and good agreement is displayed. Subsequently, the hydrodynamic parameters are computed in two conditions: with a stator and without a stator. By comparing the results, it is observed that the total thrust coefficient of the propulsion system with a stator at all advance ratios increases by at least 40%. It is further observed that addition of a stator also improves its efficiency.

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

2019 ◽  
Vol 7 (8) ◽  
pp. 240
Author(s):  
Gao ◽  
Yang ◽  
Li ◽  
Dong
Keyword(s):  
High Speed ◽  
Water Immersion ◽  
Active Role ◽  
Numerical Results ◽  
Hydrodynamic Performance ◽  
Pipe Diameter ◽  
Pressure Area ◽  
Cfd Method ◽  
Thrust And Torque ◽  
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.

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

Symmetry ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 196 ◽  
Author(s):  
Chen-Wei Chen ◽  
Ming Li
Keyword(s):  
Surface Pressure ◽  
Spline Interpolation ◽  
Pressure Coefficient ◽  
Panel Method ◽  
Hydrodynamic Performance ◽  
Surface Velocity ◽  
B Spline ◽  
Marine Propellers ◽  
Aspect Ratios ◽  
Thrust And Torque

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.

scholarly journals Influence of Various Stator Parameters on the Open-Water Performance of Pump-Jet Propulsion

2021 ◽  
Vol 9 (12) ◽  
pp. 1396
Author(s):  
Fuzheng Li ◽  
Qiaogao Huang ◽  
Guang Pan ◽  
Denghui Qin ◽  
Han Li
Keyword(s):  
Open Water ◽  
Hydrodynamic Performance ◽  
Maximum Efficiency ◽  
Sweep Angle ◽  
Jet Propulsion ◽  
Performance Variation ◽  
Lean Angle ◽  
Open Water Performance ◽  
Stagger Angle ◽  
Thrust And Torque

In order to improve the hydrodynamic performance of pump-jet propulsion (PJP) when matching stator with the rotor, the RANS method with SST k-ω turbulence model is employed to study the influence of six kinds of stator parameters, which are classified into three groups, i.e., stator solidity, stator angles and rotor–stator spacing (S). Results show that the stator solidity involves the blade number (Ns) and chord length (L), has an obvious acceleration effect at and after stator, and produces a higher thrust and torque with a slight efficiency change. Further comparing Ns and L results, we find greater distinctions between the two cases when stator solidity is greatly adjusted. Three stator angles, i.e., stagger angle (α), lean angle (γ), and sweep angle (β), are studied. The α has the biggest effect on the thrust, torque, and efficiency; meanwhile, it shifts the advance number that corresponds to maximum efficiency. The effect of γ is similar to α, but its influence is far less than α. However, there is little difference between various β cases except for off-design conditions, where the efficiency drops dramatically as β increases. The S has a slight effect on PJP performance. Even though S decreases 34% relative to the original PJP, the rotor thrust and torque increase by less than 1%. In addition, we compare torque balance locations under various parameters, and each component force is analyzed in detail to explain the reason for performance variation. The present work is conducive to future optimization in PJP design.

A Study on Various Aerodynamic Effects of Pointed Tip Blade

2015 ◽  
Author(s):  
Shrabanti Roy ◽  
Kyoungsoo Lee ◽  
Ziaul Huque ◽  
Raghava Kommalapati
Keyword(s):  
Wind Speed ◽  
Pressure Coefficient ◽  
High Wind ◽  
Wind Speeds ◽  
Ansys Cfx ◽  
Simulation Results ◽  
The Difference ◽  
Torque Values ◽  
Nrel Phase Vi ◽  
Thrust And Torque

A wind turbine blade performance depends on various parameters of which the shape of the blade is one of the most important one. In this work the shape of the tip of original NREL Phase-VI blade (S809 airfoil) has been modified to determine the changes in the blade aerodynamic performance. The chord length of new blade is kept similar to the original NREL blade up to 90% of the span. Last 10% was modified to a pointed tip at the pitch axis. This paper presents a comparative study of the effect of pointed tip on aerodynamic loads. CFD simulations were performed on both original NREL shape and pointed tip shape blades. The simulation results of pointed tip blade were compared with both experimental and simulation results of original blade. Ansys geometry modeler was used to draw the geometry and to generate the grids. Ansys CFX solver and post processor were used for simulation and calculation of the results. To predict the near wall transitional effect SST Gamma Theta turbulence model was used. Results of pressure coefficient along the chord at various blade sections of the pointed tip blade were found to be almost similar to the original NREL blade CFD results. Tangential and normal force along the span of pointed tip blade at different wind speeds showed some similarity in results compared with CFD results of original NREL blade. From the velocity contour the separation of flow with the increase of wind speed can clearly be observed. Thrust and torque effects are also observed at various wind speeds. The torque values for the pointed tip blade were found to be higher in the pre-stall and stall region but slightly lower in post-stall region. But compared to the torque values the difference in thrust at the same region is found to be negligible. Pointed tip thrust values are in better agreement at high wind speeds with respect to the experimental data. The flow separation at high wind speed is also found to be less with pointed tip blade compared to the original blade.

Effects of step configuration on hydrodynamic performance of one- and doubled-stepped planing flat plates: A numerical simulation

2019 ◽  
Vol 234 (1) ◽  
pp. 181-195 ◽  
Author(s):  
Abbas Dashtimanesh ◽  
Fatemeh Roshan ◽  
Sasan Tavakoli ◽  
Ahmadreza Kohansal ◽  
Bahare Barmala
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Critical Role ◽  
Pressure Coefficient ◽  
Numerical Data ◽  
Hydrodynamic Performance ◽  
Step Height ◽  
Hydrodynamic Characteristics ◽  
Flat Plates ◽  
Marine Vehicles

Categorized as one of high-speed marine vehicles, stepped planing hulls have the potential to reach relatively high speed in the sea by decreasing wetted surface. There were and still are some challenges in modeling of these vessels and design of ideal situation of steps. In the current study, a numerical-based method has been used to provide understanding about the effect of step height and its location on hydrodynamic characteristics of double-stepped planing plates. At the first step, one-stepped planing plate is numerically simulated. Results are compared against exiting numerical data, suggesting that results of the current numerical simulation are similar to results of previous numerical simulations. Then, double-stepped planing plates are modeled and pressure distribution, wetted length, free surface elevation and drag over lift ratio are computed. It is seen that, ventilation length behind the step and pressure coefficient are increased when step height of one- and a double-stepped planing plates are increased. It has been shown that, unlike an one-stepped planing plate, drag coefficient of a double-stepped planing plate can be increased when the step height is increased. The effects of the location of the second step on the performance of the planing plate have been explored, showing that this position plays a critical role on hydrodynamic forces. It is demonstrated that when the smallest possible lift force is produced by the middle-body, the plate shows the best performance (highest lift over drag ratio).

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