scholarly journals The Prediction of the Performance of a Twisted Rudder

2021 ◽  
Vol 11 (15) ◽  
pp. 7098
Author(s):  
Ilryong Park ◽  
Bugeun Paik ◽  
Jongwoo Ahn ◽  
Jein Kim
Keyword(s):  
Lift Force ◽  
Twist Angle ◽  
Hydrodynamic Characteristics ◽  
Total Drag ◽  
Reference Design ◽  
Drag And Lift ◽  
Correction Step ◽  
Rudder Angle ◽  
Ship Speed ◽  
Good Agreement

A new design approach using the concept of a twisted rudder to improve rudder performances has been proposed in the current paper. A correction step was introduced to obtain the accurate inflow angles induced by the propeller. Three twisted rudders were designed with different twist angle distributions and were tested both numerically and experimentally to estimate their hydrodynamic characteristics at a relatively high ship speed. The improvement in the twisted rudders compared to a reference flat rudder was assessed in terms of total cavitation amount, drag and lift forces, and moment for each twin rudder. The total amount of surface cavitation on the final optimized twin twisted rudder at a reference design rudder angle decreased by 43% and 34.4% in the experiment and numerical prediction, respectively. The total drag force slightly increased at zero rudder angle than that for the twin flat rudder but decreased at rudder angles higher than 4° and 6° in the experiment and numerical simulation, respectively. In the experimental measurements, the final designed twin twisted rudder gained a 5.5% increase in the total lift force and a 37% decrease in the maximum rudder moment. Regarding these two performances, the numerical results corresponded to an increase of 3% and a decrease of 66.5%, respectively. In final, the present numerical and experimental results of the estimation of the twisted rudder performances showed a good agreement with each other.

scholarly journals Performance Comparison of Bow and Stern Rudder for High-Speed Supercavitating Vehicles

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Chuang Huang ◽  
Kai Luo ◽  
Kan Qin ◽  
Daijin Li ◽  
Jianjun Dang
Keyword(s):  
High Speed ◽  
Lift Force ◽  
Turbulence Models ◽  
Performance Comparison ◽  
Hydrodynamic Characteristics ◽  
Control Force ◽  
Supercavitating Vehicles ◽  
Wetted Area ◽  
Control Surfaces ◽  
Rudder Angle

To predict the hydrodynamic characteristics and supercavity shape of supercavitation flows, the numerical model including VOF, cavitation model, and turbulence models is presented and validated by a well-established empirical correlation. The numerical method is then employed to simulate the high-speed supercavitating vehicles with two different types of control surfaces: bow rudders and stern rudders. The hydrodynamic characteristics and influences on the supercavity are compared. By contrast with the stern rudder, the bow rudder with the same wetted area is capable of generating a larger control force and moment. Also, the bow rudder introduces a considerable deformation to the forepart of the supercavity, while the stern rudder provides a negligible influence on the supercavity before it. In addition, the bow rudder is fully wetted, and the lift force only changes with the rudder angle. However, the stern rudder is partly wetted; the lift force is not only determined by the rudder angle but also related to the actual wetted status.

Numerical evaluation of hydrodynamic characteristics of planing hulls by using a hybrid method

2021 ◽  
pp. 147509022199024
Author(s):  
Emre Kahramanoglu ◽  
Silvia Pennino ◽  
Huseyin Yilmaz
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Calm Water ◽  
Preliminary Design Stage ◽  
Reduction Function ◽  
Hull Forms ◽  
Good Agreement

The hydrodynamic characteristics of the planing hulls in particular at the planing regime are completely different from the conventional hull forms and the determination of these characteristics is more complicated. In the present study, calm water hydrodynamic characteristics of planing hulls are investigated using a hybrid method. The hybrid method combines the dynamic trim and sinkage from the Zarnick approach with the Savitsky method in order to calculate the total resistance of the planing hull. Since the obtained dynamic trim and sinkage values by using the original Zarnick approach are not in good agreement with experimental data, an improvement is applied to the hybrid method using a reduction function proposed by Garme. The numerical results obtained by the hybrid and improved hybrid method are compared with each other and available experimental data. The results indicate that the improved hybrid method gives better results compared to the hybrid method, especially for the dynamic trim and resistance. Although the results have some discrepancies with experimental data in terms of resistance, trim and sinkage, the improved hybrid method becomes appealing particularly for the preliminary design stage of the planing hulls.

RANS Study on Hydrodynamic Characteristics of Flapped Rudders

2018 ◽  
Author(s):  
Jialun Liu ◽  
Robert Hekkenberg ◽  
Bingqian Zhao
Keyword(s):  
Yangtze River ◽  
Area Ratio ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Coefficients ◽  
Sectional Area ◽  
The Yangtze River ◽  
Long Distance ◽  
Ansys Fluent ◽  
Rans Simulations ◽  
Rudder Angle

Ships that equipped with flapped rudders have better manoeuvring performance than ships fitted with traditional spade rudders. Moreover, this advantage is achieved without significantly affecting the ship’s resistance during normal cruising. Flapped rudders are, therefore, favourable for ships that require high manoeuvring performance and sail long distance. Nowadays, there is a trend of using twin flapped rudders on newly built inland vessels in the Yangtze River. To properly design these ships and analyse their manoeuvring performance, the hydrodynamic characteristics of the flapped rudders are required. In this paper, a RANS study is performed to analyse the impacts of the three main properties of a flapped rudder on its hydrodynamic coefficients. The target properties are the rudder profile, the flap-linkage ratio (the flapped angle relative to the rudder chord line divided by the applied rudder angle), and the flap-area ratio (the sectional area of the flap divided by the total sectional area). The RANS simulations are carried out with commercial meshing tool ANSYS Meshing and CFD solver ANSYS Fluent.

Forced oscillation experiments

1991 ◽  
Vol 334 (1634) ◽  
pp. 199-211
Keyword(s):  
Numerical Methods ◽  
Water Depth ◽  
Forced Oscillation ◽  
Vertical Plane ◽  
Forced Oscillations ◽  
Hydrodynamic Characteristics ◽  
Scale Models ◽  
Ship Speed

Forced oscillation experiments with scale models are carried out to determine hydrodynamic characteristics of ships, with respect to motions in waves or steering and manoeuvring qualities. Depending on the considered motion components, in a horizontal or vertical plane, various methods are used to induce forced oscillations which are discussed briefly. Some results of forced oscillation experiments are presented as examples of this technique and compared with calculations based on numerical methods. The comparisons include, among others, the effects of ship speed and restricted water depth.

REVIEW—Review of Flow Interference Between Two Circular Cylinders in Various Arrangements

1977 ◽  
Vol 99 (4) ◽  
pp. 618-633 ◽  
Author(s):  
M. M. Zdravkovich
Keyword(s):  
Flow Pattern ◽  
Drag Force ◽  
Lift Force ◽  
Flow Direction ◽  
Critical Survey ◽  
Tandem Arrangement ◽  
Critical Spacing ◽  
Gap Flow ◽  
Lift Forces ◽  
Drag And Lift

There are infinite numbers of possible arrangements of two parallel cylinders positioned at right angles to the approaching flow direction. Of the infinite arrangements, two distinct groups may be identified: in one group, the cylinders are in a tandem arrangement, one behind the other at any longitudinal spacing; and in the second group, the cylinders face the flow side by side at any transverse spacing. All other combinations of longitudinal and transverse spacings represent staggered arrangements. The tandem arrangement will be treated first. A critical survey of previous research revealed some “odd” features which had been observed and overlooked by various authors. The discontinuity of vortex shedding implies that a similar discontinuity should be expected for the drag force on both cylinders. The measurements of the front (gap) pressures of the downstream cylinder and the base pressures of both cylinders at various spacings reveal a discontinuous “jump” at some critical spacing. The discontinuity is caused by the abrupt change from one stable flow pattern to another at the critical spacing. A new interpretation is given for the existing data on the drag force for both cylinders. The effects of Reynolds number and surface roughness are treated in some detail. Following this, two cylinders arranged side by side to the approaching flow are considered. All the available data on measured forces are compiled together with additional measurements in the range of intermittent changes of drag and lift forces. The bistable nature of the asymmetric flow pattern around each cylinder produces two alternative values of the drag force coupled with two alternative values of the lift force. The introduction of the interference force coefficient exposes the physical origin of two different forces experienced by the cylinders when arranged side by side. Finally, the least reported arrangement of two staggered cylinders is reviewed. The various arrangements are grouped into classes according to the sign of the lift force, or whether the drag force is greater or less than that for a single cylinder. The measurements of drag and lift forces for various arrangements reveal two different regimes for the lift force. In one regime, the lift force directed toward the wake of the upstream cylinder is due to the entrainment of the flow into the fully developed wake of the upstream cylinder. The lift force in this regime reaches a maximum value when the downstream cylinder is near to the upstream wake boundary. In the second regime, at very small spacings, the lift force becomes very large due to an intense gap flow which displaces the wake of the upstream cylinder. The maximum lift force occurs with the downstream cylinder near to the horizontal axis of the upstream cylinder. A discontinuity in the lift force for some staggered arrangements is found and attributed to the bistable nature of the gap flow.

Numerical Study in Wing Tip Vortex for a Modified Commercial Boeing Aircraft

2008 ◽  
Author(s):  
Ricardo Hernandez-Rivera ◽  
Abel Hernandez-Guerrero ◽  
Cuauhtemoc Rubio-Arana ◽  
Raul Lesso-Arroyo
Keyword(s):  
Numerical Study ◽  
Tip Vortex ◽  
Total Drag ◽  
The Core ◽  
Induced Drag ◽  
Wing Tip Vortex ◽  
Drag And Lift ◽  
Wing Tips ◽  
Wing Tip ◽  
Constant Mach Number

Recent studies have shown that the use of winglets in aircrafts wing tips have been able to reduce fuel consumption by reducing the lift-induced drag caused by wing tip vortex. This paper presents a 3-D numerical study to analyze the drag and lift forces, and the behavior of the vortexes generated in the wing tips from a modified commercial Boeing aircraft 767-300/ER. This type of aircraft does not contain winglets to control the wing tip vortex, therefore, the aerodynamic effects were analyzed adding two models of winglets to the wing tip. The first one is the vortex diffuser winglet and the second one is the tip fence winglet. The analyses were made for steady state and compressible flow, for a constant Mach number. The results show that the vortex diffuser winglet gives the best results, reducing the core velocity of the wing tip vortex up to 19%, the total drag force of the aircraft up to 3.6% and it leads to a lift increase of up to 2.4% with respect to the original aircraft without winglets.

Three-Dimensional Numerical Simulation of the Flow around Two Side-by-Side Cylinders of Different Diameters

2014 ◽  
Vol 721 ◽  
pp. 199-202
Author(s):  
Zhen Xiao Bi ◽  
Zhi Han Zhu
Keyword(s):  
Numerical Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Simulation Method ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Eddy Simulation ◽  
Drag And Lift ◽  
Different Diameters

This paper presents the calculation of hydrodynamic characteristics of two side-by-side cylinders of different diameters in three dimensional incompressible uniform cross flow by using Large-eddy simulation method based on dynamical Smagorinsky-Lilly sub-grid scale model. Solution of the three dimensional N-S equations were obtained by the finite volume method. The numerical simulation focused on investigating the characteristic of the pressure distribution (drag and lift force), vorticity field and turbulence Re=. Results shows that, the asymmetry of the time –averaged velocity distribution in the flow direction behind the two cylinders is very obvious; the frequency of eddy shedding of the small cylinder is about twice of the large one. The turbulence of cylinders is more obvious.

scholarly journals Heat Transfer Enhancement and Hydrodynamic Characteristics of Nanofluid in Turbulent Flow Regime

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Mohammad Nasiri-lohesara
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Pure Water ◽  
Reynolds Numbers ◽  
Hydrodynamic Characteristics ◽  
Two Phase ◽  
Tube Heat Exchanger ◽  
Turbulent Flow Regime ◽  
Lower Slope ◽  
Good Agreement

Turbulent forced convection ofγ-Al2O3/water nanofluid in a concentric double tube heat exchanger has been investigated numerically using mixture two-phase model. Nanofluids are used as coolants flowing in the inner tube while hot pure water flows in outer tube. The studies are conducted for Reynolds numbers ranging from 20,000 to 50,000 and nanoparticle volume fractions of 2, 3, 4, and 6 percent. Results showed that nanofluid has no effects on fully developed length and average heat transfer coefficient enhances with lower slope than wall shear stress. Comparisons with experimental correlation in literature are conducted and good agreement with present numerical study is achieved.

CFD Based Investigations into Optimization of Diffuser Angle on Rear Bus Body

2016 ◽  
Vol 836 ◽  
pp. 127-131 ◽  
Author(s):  
Wawan Aries Widodo ◽  
Mutiara Nuril Karohmah
Keyword(s):  
Fluid Flow ◽  
Lift Force ◽  
Bluff Body ◽  
Cfd Simulation ◽  
Aerodynamic Forces ◽  
Wake Structure ◽  
Bus Body ◽  
Simulation Results ◽  
Drag And Lift ◽  
Diffuser Angle

Fluid flow interaction around bluff body to create aerodynamic forces including drag and lift force. The strategy to improve arodynamic forces to modify the shape of rear body. This investigation is conducted to simulate fluid flow past a bus body with variation of diffuser angle on the rear. The diffuser angle was set to 0°, 6°, 12°, and 18°, respectively. The CFD simulation results shown that diffuser on rear body bus models able to improve the aerodynamic forces and wake structure are correspond with incresing diffuser angle. The drag coefficient was reduced until 2.3% is related with diffuser angle (β) 180, also, diffuser angle (β) 120 capable to increase downforce significantly until ten times are compared with zero diffuser angle.

Sign in / Sign up

Export Citation Format

Share Document