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).

scholarly journals A Hydrodynamic Methodology And CFD Analysis For Performance Prediction Of Stepped Planing Hulls

2015 ◽  
Vol 22 (2) ◽  
pp. 23-31 ◽  
Author(s):  
Hassan Ghassemi ◽  
Mojtaba Kamarlouei ◽  
Sajad Taj Golah Veysi
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Geometrical Parameters ◽  
Cfd Analysis ◽  
Analysis Model ◽  
Marine Coatings ◽  
Resistance Reduction ◽  
Calculation Results ◽  
Fruitful Research

AbstractNowadays all efforts in planing hull research are focused on resistance reduction for achieving the highest speed in fast planing crafts. Furthermore, many fruitful research projects have been carried out on marine coatings, planing equipment, and optimization of propeller and hull form, which revolutionized industry of high - speed crafts and made them an efficient survival vehicle in coastal areas and rivers. In this paper the hydrodynamic performance of planing hulls are investigated by means of a modified Savitsky model for both non-stepped and stepped bodies. Meanwhile, in order to meet this goal reasonably, effective geometrical parameters of planing hull are investigated and then operational hydrodynamic characteristics of the craft are predicted by using a computational program. Finally, the calculation results are verified by means of a CFD-analysis model.

Pure Yaw Simulations of Fast Delft Catamaran 372 in Deep Water

2020 ◽  
Author(s):  
Suleyman Duman ◽  
Sakir Bal
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Point Of View ◽  
Hydrodynamic Performance ◽  
Marine Vehicles ◽  
Wave Interference ◽  
Force Moment ◽  
Unsteady Rans ◽  
Cfd Method ◽  
Turbulent Flow Conditions

Fast marine vehicles have become more important than ever before due to increasing need and population. In maritime sector, special ship types such as catamaran and trimaran have already been designed and/or built to the civil and naval areas of use. The hydrodynamic performance of these vessels is an interesting problem for naval architects due to the wave interference between the hulls. From this point of view, a generic high-speed catamaran hull form (Delft catamaran 372 or DC372) has been chosen for the numerical prediction of manoeuvring coefficients. To achieve this, the pure yaw captive manoeuvre simulations of the DC372 have been performed in deep water conditions at several oscillating frequencies by using CFD method. The unsteady RANS equations have been solved under incompressible, viscous and fully turbulent flow conditions. The uncertainty in the computations has been determined using proper techniques. Manoeuvring coefficients have been calculated by processing time dependent force/moment signals obtained numerically with the help of Fourier analysis. Due to the accurate grid structure used here, numerical ventilation has been prevented and wave deformations have been captured well.

Ship Hull Drag Reduction Using Bottom Air Injection

2007 ◽  
Author(s):  
Ahmad Fakhraee ◽  
Manoucher Rad ◽  
Hamid Amini ◽  
Mehdi Rishehri
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Frictional Resistance ◽  
Air Injection ◽  
Hydrodynamic Resistance ◽  
Alternative Form ◽  
Hydrodynamic Characteristics ◽  
Air Cavity ◽  
Marine Vehicles ◽  
Wetted Surface Area

Air cavity ship concept has received some interest due to its potential on viscous resistance reduction for high speed craft. Air-cavity ships (ACS) are advanced marine vehicles that use air injection at the wetted hull surfaces to improve a vessel’s hydrodynamic characteristics. Air is supplied through nozzles under a profiled bottom to generate an air cavity beneath such a ship, so that a steady air layer separates a part of the bottom from contact with water, consequently reducing hydrodynamic resistance. Resistance tests were conducted with two forms: first of which was planning catamaran hull form, and second one was an alternative form with an air cavity injection under its bottom which was tested both without any air injection and with three different air injection ranges. Dead rise angle was fixed to 23 degree during both model tests. Frictional resistance was calculated from wetted surface area and compared with total resistance. It is clear from these results that improvements in high speed planning catamarans can be realized by using bottom air injection. Drag reduction achieved on these model is within 13–23 percent.

scholarly journals Lift-to-Drag Ratio of the Application of Hydrofoil With Variation Mounted Position on High-Speed Patrol Vessel

CFD letters ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 1-9
Author(s):  
Muhammad Arif Budiyanto ◽  
Naufal Yudha Prawira ◽  
Haekal Dwiputra
Keyword(s):  
High Speed ◽  
High Performance ◽  
Hydrodynamic Performance ◽  
Comparison Result ◽  
Academic Literature ◽  
Marine Vehicles ◽  
Basic Model ◽  
Optimum Position ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The hydrofoil is one of the hydrodynamic support technologies for marine vehicles that provide a high performance and are feasible to operate. The mounting position of hydrofoils on the hull is one of the keys to improving the hydrodynamic performance, where the existing academic literature to find the optimum position of hydrodynamic is still deficient. The objective of this study is to compare the mounting locations of hydrofoil in the horizontal axis in a high-speed patrol vessel. The comparison result is based on the computational fluid dynamics where the basic model was validated using experimental data. Three mounting location cases of hydrofoils were performed i.e. middle section, stern section, and behind the stern. The result shows that the optimal hydrofoil mounting position is after the transom. In this position, the value of the lift-to-drag ratio is higher by an average of 10% - 29% compared to other positions depending on the speed of the ship.

Hydrodynamic Performance and Appendage Considerations of Wave-Piercing Planing Craft Overlapping Waves and Porpoising

2019 ◽  
Author(s):  
Sang-Won Kim ◽  
Sang-Eui Lee ◽  
Gyoung-Woo Lee ◽  
Kwang-Cheol Seo ◽  
Nobuyuki Oshima
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
High Speed ◽  
Numerical Study ◽  
Hydrodynamic Performance ◽  
Moving Mesh ◽  
Navier Stokes ◽  
Hull Form ◽  
Wave Condition ◽  
Planing Craft

Abstract This work addresses the numerical study of wave-piercing planing hull and related hydrodynamic performance as the appendages. From the half century ago, the interest in high-speed planing crafts has been advanced toward maintaining performance stably. The main reasons to make it hard are instability motion occurring from porpoising and wave condition. Porpoising is mainly due to overlap the heaving and pitching motion with certain period, which is caused by instable pressure distribution and changing longitudinal location of center of gravity. In addition, in wave condition, encountering wave disturbs going into planing mode. This paper presents numerical results of wave-piercing planing hull in porpoising and wave condition. Numerical simulation is conducted via Reynolds Averaged Navier-stokes (RANS) with moving mesh techniques (overset grid), performed at different wave condition. The results for the behaviors of wave-piercing hull form are practically presented and investigated in this study. The understanding of these phenomena is important for design of appendages of wave-piercing hull-form.

Hydrodynamic Characteristics of the Surface-Piercing Propeller for the Planing Craft

2009 ◽  
Author(s):  
Hassan Ghassemi ◽  
Roya Shademani ◽  
Abdollah Ardeshir
Keyword(s):  
Numerical Method ◽  
Weber Number ◽  
High Speed ◽  
Hydrodynamic Characteristics ◽  
Propulsive Efficiency ◽  
Planing Craft ◽  
Marine Vehicles ◽  
Pitch Ratio ◽  
Advance Ratio ◽  
Surface Piercing Propeller

Market demands for high-speed marine vehicles (HSMVs) are high in both commercial and naval branches. It is the naval architects’ task to design the hull and propulsion system to diminish drag, improve the propulsive efficiency, higher safety and better maneuverability. Surface Piercing Propellers (SPPs) may provide those possessions for the vehicles. Unlike immersed propellers, behavior of the SPPs is susceptible to immersed depth, Weber number and shaft inclination angle. This paper uses a specially practical and numerical method to predict the hydrodynamic characteristics of the SPPs. Critical advance ratio is obtained by practical formula, using Weber number and pitch ratio in the transition mode. Numerical method employs the potential based boundary element method (BEM) on the engaged surfaces. Two models of three and six bladed of the SPPs (SPP-1 and SPP-2) are selected and some results are shown.

Two-Dimensional Numerical Simulation of Vortex Shedding of Multiple Stranded Ropes

2019 ◽  
Author(s):  
Xinxin Wang ◽  
Liuyi Huang ◽  
Yanli Tang ◽  
Fenfang Zhao ◽  
Peng Sun
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Flow Distribution ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Two Dimensional ◽  
Navier Stokes Equation

Abstract The stranded rope is one of the important components of the fishery aquaculture equipment. We investigate the fluid flow through two-dimensional stranded rope by direct simulation of the Navier-Stokes equations. We show that for different kinds of stranded rope structures, there are significant differences in hydrodynamic performance. This paper established a numerical model of unsteady flow past the stranded rope based on the Navier-Stokes equation and Morison formulas to study the hydrodynamic characteristics of three-stranded rope, four-stranded rope, and seven-stranded rope, respectively. The turbulence flow was simulated using Standard k-ε model and Shear-Stress Transport k-ω (SST) model. The flow distribution strongly depends on the Reynolds number, a range of 3,900 and 30,000. With increasing Reynolds number, the alternate eddy formation and shedding were repeated behind the stranded ropes. Such parameters of hydrodynamic characteristics of multiple stranded ropes were calculated as the lift and drag coefficients, and vortex shedding frequencies. The numerical simulation results presented flow performances of different cross sections (a, b, c, d) at different Reynolds numbers. However, Reynolds number has no significant impact on the Strouhal number for the same attack angle of the stranded rope.

scholarly journals Impact of Different Nose Lengths on Flow-Field Structure around a High-Speed Train

2019 ◽  
Vol 9 (21) ◽  
pp. 4573 ◽  
Author(s):  
Xianli Li ◽  
Guang Chen ◽  
Dan Zhou ◽  
Zhengwei Chen
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Aerodynamic Force ◽  
Pressure Coefficient ◽  
Wake Flow ◽  
Maximum Pressure ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Rapid Reduction ◽  
Comparison Results

In this study, the time-averaged and instantaneous slipstream velocity, time-averaged pressure, wake flows, and aerodynamic force of a high-speed train (HST) with different nose lengths are compared and analyzed using an improved delayed detached-eddy simulation (IDDES) method. Four train models were selected, with nose lengths of 4, 7, 9, and 12 m. To verify the accuracy of the numerical simulation results, they were compared with wind tunnel test results. The comparison results show that the selection of the numerical simulation method is reasonable. The research results show that with increasing nose length, the peak values of the time-averaged slipstream velocity of the trackside position (3 m from the center of track and 0.2 m from the top of rail) and the platform position (3 m from the center of track and 0.2 m from the top of rail) decrease continuously, and show a trend of rapid reduction at first, and then a slow decrease. As the nose length increased from 4 to 12 m, the time-averaged slipstream velocity at the trackside position and platform position are decreased by 57% and 19.5%, respectively. At a height of 1.6 m from the top of the rail, ΔCP max (maximum pressure coefficient), |ΔCP min| (the absolute value of minimum pressure coefficient), and ΔCP (pressure change coefficient) decrease with increasing nose length, which is similar to the peak value of time-averaged slipstream velocity, decreasing rapidly at first and then slowly. As the nose length increased from 4 to 12 m, decreases of ΔCP max, |ΔCP min|, and ΔCP by 26.5%, 58.5%, and 44.8% were shown, respectively. Different nose lengths also have a significant impact on wake flow.

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 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.

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