Hydrodynamic Performance of an S-SWATH Ship in Calm Water and Waves

2014 ◽  
Author(s):  
Peng Qian ◽  
Hong Yi ◽  
Yinghui Li
Keyword(s):  
Stokes Equations ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Ride Quality ◽  
Navier Stokes Equations ◽  
High Speeds ◽  
Calm Water ◽  
Superconductivity Theory ◽  
Simulation Results ◽  
Yaw Angle

An unconventional SWATH (Small-Waterplane-Area-Twin-Hull) ship is introduced, named S-SWATH, which is a catamaran with twin hulls that are slightly curved in an S-form and arranged at a mean yaw angle but mirror symmetric to their common longitudinal center plane. Based on the “shallow-channel superconductivity” theory, proposed by Chen and Sharma, in this paper a more accurate viscous flow theory, solving the Reynolds-averaged Navier–Stokes equations (or RANS equations), is used to study the hydrodynamic performance of the S-SWATH ship. The simulation results of calm-water resistance and motions in waves are presented. In comparison with a benchmark conventional SWATH ship, which features a typical torpedo-shaped body, the simulation results prove the effectiveness of the S-shape design. On one hand, the S-SWATH ship inherits the major advantages of SWATH ships, such as the superior ride quality, acceptable acceleration levels for human habitability and therefore comfort and overall superior seakeeping characteristics. On the other hand, the S-SWATH ship has much less low-speed drag than its conventional SWATH counterpart, and comparable total drag at high speeds.

Numerical Solution of 3-D Water Entry Problems With a Constrained Interpolation Profile Method

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Qingyong Yang ◽  
Wei Qiu
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Type Equation ◽  
Water Entry ◽  
Navier Stokes ◽  
Time Step ◽  
Constrained Interpolation ◽  
Navier Stokes Equations ◽  
Highly Nonlinear ◽  
Calm Water

This paper presents the numerical solutions of slamming problems for 3D bodies entering calm water with vertical and oblique velocities. The highly nonlinear water entry problems are governed by the Navier-Stokes equations and were solved by a constrained interpolation profile (CIP)-based finite difference method on a fixed Cartesian grid. In the computation, the 3D CIP method was employed for the advection calculations and a pressure-based algorithm was applied for the nonadvection calculations. The solid body and the free surface interfaces were captured by density functions. For the pressure computation, a Poisson-type equation was solved at each time step by using the conjugate gradient iterative method. Validation studies were carried out for a 3D wedge, a cusped body vertically entering calm water, and the oblique entry of a sphere into calm water. The predicted hydrodynamic forces on the wedge, the cusped body, and the sphere were compared with experimental data.

Numerical Simulation Study on the Concentration Field in an Oscillatory Flow Reactor with Conic Ring Baffles

2013 ◽  
Vol 378 ◽  
pp. 418-423
Author(s):  
Gang Liu ◽  
Jia Wu ◽  
Wei Li
Keyword(s):  
Numerical Simulation ◽  
Oscillatory Flow ◽  
Flow Reactor ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Concentration Field ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbulent Diffusion Coefficient ◽  
Simulation Results

The three-dimensional construct of concentration field in an oscillatory flow reactor (OFR) containing periodically spaced conic ring baffles was investigated by numerical simulation employing Reynolds-averaged Navier-Stokes equations. The computation covered a range of Oscillatory Reynolds number (Reo) from 623.32 to 3116.58 at Strouhal number (St) 0.995 and 1.99. The contour of concentration field showed that the concentration in the most part of the channel is relative uniform and a small retention area is found below the conic ring baffles, which means a region of relative poor mixing. In addition, the turbulent diffusion coefficient calculated from the simulation results implied the greater oscillatory amplitude and oscillatory frequency superimposed to the fluid, the stronger is the turbulence intensity.

scholarly journals Calculations of the Hydrodynamic Characteristics of a Ducted Propeller Operating in Oblique Flow

2017 ◽  
Vol 10 (20) ◽  
pp. 31
Author(s):  
Hassan Ghassemi ◽  
Sohrab Majdfar ◽  
Hamid Forouzan
Keyword(s):  
Stokes Equations ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Numerical Code ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Navier Stokes Equations ◽  
Oblique Flow ◽  
Ducted Propeller ◽  
Acceptable Agreement

The purpose of this paper is to calculate the hydrodynamic performance of a ducted propeller (hereafter Duct_P) at oblique flows. e numerical code based on the solution of the Reynolds-averaged Navier– Stokes equations (RANSE) applies to the Kaplan propeller with 19A duct. e shear-stress transport (SST)-k-ω turbulence model is used for the present results. Open-water hydrodynamic results are compared with experimental data showing a relatively acceptable agreement. Two oblique flow angles selected to analyze in this paper are 10 and 20 degrees. Numerical results of the pressure distribution and hydrodynamic performance are presented and discussed. 

The Validity of the Compressible Reynolds Equation for Gas Lubricated Textured Parallel Slider Bearings

2012 ◽  
Author(s):  
Mingfeng Qiu ◽  
Brian Bailey ◽  
Rob Stoll ◽  
Bart Raeymaekers
Keyword(s):  
Gas Flow ◽  
Reynolds Equation ◽  
Stokes Equations ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Slider Bearings ◽  
Simplifying Assumptions ◽  
Simulation Results

The Navier-Stokes and compressible Reynolds equations are solved for gas lubricated textured parallel slider bearings under hydrodynamic lubrication for a range of realistic texture geometry parameters and operating conditions. The simplifying assumptions inherent in the Reynolds equation are validated by comparing simulation results to the solution of the Navier-Stokes equations. Using the Reynolds equation to describe shear driven gas flow in textured parallel slider bearings is justified for the range of parameters considered.

Hydrodynamic Performance of Autonomous Underwater Gliders with Active Twin Undulatory Wings of Different Aspect Ratios

2020 ◽  
Vol 8 (7) ◽  
pp. 476 ◽  
Author(s):  
Yongcheng Li ◽  
Jianxin Hu ◽  
Qiuzhuo Zhao ◽  
Ziying Pan ◽  
Zheng Ma
Keyword(s):  
Linear Growth ◽  
Stokes Equations ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Immersed Boundary ◽  
Underwater Glider ◽  
Navier Stokes Equations ◽  
Underwater Gliders ◽  
Aspect Ratios ◽  
Autonomous Underwater Glider

The propulsive performance of a bio-inspired autonomous underwater glider (AUG) with active twin undulatory wings undergoing undulatory motion was investigated by numerically solving the viscous incompressible Navier–Stokes equations, coupled with the immersed boundary method. The aspect ratio (AR) effects of the undulatory wings were studied. The simulation results showed that with the increase of AR, the thrust force generated by the active twin undulatory wings showed a linear growth, while the propulsion efficiency of the AUG increased to the peak and then decreased. The optimum magnitude of AR around 2 was obtained in the current study. The vortex structures in the wake of the active twin wings are also presented and discussed. The conclusions acquired here could provide guidance for the new conceptual design of bio-inspired AUGs.

Perturbation theory and numerical modelling of weakly and moderately nonlinear dynamics of the incompressible Richtmyer–Meshkov instability

2014 ◽  
Vol 751 ◽  
pp. 432-479 ◽  
Author(s):  
A. L. Velikovich ◽  
M. Herrmann ◽  
S. I. Abarzhi
Keyword(s):  
Perturbation Theory ◽  
Stokes Equations ◽  
Early Time ◽  
Inviscid Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Comput Phys ◽  
Acceleration And Deceleration ◽  
Simulation Results ◽  
The Impact

AbstractA study of incompressible two-dimensional (2D) Richtmyer–Meshkov instability (RMI) by means of high-order perturbation theory and numerical simulations is reported. Nonlinear corrections to Richtmyer’s impulsive formula for the RMI bubble and spike growth rates have been calculated for arbitrary Atwood number and an explicit formula has been obtained for it in the Boussinesq limit. Conditions for early-time acceleration and deceleration of the bubble and the spike have been elucidated. Theoretical time histories of the interface curvature at the bubble and spike tip and the profiles of vertical and horizontal velocities have been calculated and favourably compared to simulation results. In our simulations we have solved 2D unsteady Navier–Stokes equations for immiscible incompressible fluids using the finite volume fractional step flow solver NGA developed by Desjardins et al. (J. Comput. Phys., vol. 227, 2008, pp. 7125–7159) coupled to the level set based interface solver LIT (Herrmann, J. Comput. Phys., vol. 227, 2008, pp. 2674–2706). We study the impact of small amounts of viscosity on the flow dynamics and compare simulation results to theory to discuss the influence of the theory’s ideal inviscid flow assumption.

Numerical analysis on effects of blade number on hydrodynamic performance of low-pitch marine cycloidal propeller

2019 ◽  
Vol 234 (2) ◽  
pp. 490-501
Author(s):  
Mohammad Bakhtiari ◽  
Hassan Ghassemi
Keyword(s):  
Numerical Method ◽  
Stokes Equations ◽  
Thrust Force ◽  
Circular Disk ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Thrust Coefficient ◽  
Navier Stokes Equations ◽  
Blade Number ◽  
Marine Propulsion

Marine cycloidal propeller, as a special type of marine propulsion system, is used for ships that require high maneuverability, such as tugs and ferries. In a marine cycloidal propeller, the thrust force is generated by rotation of a circular disk with a number of lifting blades fitted on the periphery of the disk, so that the propeller axis of rotation is perpendicular to the direction of thrust force. Each blade pitches about its own axis, and the thrust magnitude and direction can be adjusted by controlling the pitching angle of the blades. Therefore, the propulsion and maneuvering units are combined together and no separate rudder is needed to maneuver the ship. Two configurations of marine cycloidal propeller have been studied and developed based on propeller pitch: low-pitch propeller (designed for advance coefficient less than one, means λ < 1) and high-pitch propeller (designed for λ > 1). Low-pitch marine cycloidal propellers are used in applications with low-speed maneuvering requirements, such as tugboats and minesweepers. In this study, the effects of blade number on hydrodynamic performance of low-pitch marine cycloidal propeller with pure cycloidal motion of the blades are investigated. The turbulent flow around marine cycloidal propeller is solved using a 2.5D numerical method based on unsteady Reynolds-averaged Navier–Stokes equations with shear-stress transport k–ω turbulent model. The presented numerical method was validated against experimental data and showed good agreement. The results showed that the thrust coefficient of marine cycloidal propeller generally decreases by increasing the blade number, whereas the torque coefficient increases. Consequently, the hydrodynamic efficiency of marine cycloidal propeller drops as the blade number increases.

Numerical Study on the Effect of Tandem Spacing on Flow Induced Motions of Two Cylinders With Passive Turbulence Control

2015 ◽  
Author(s):  
Lin Ding ◽  
Li Zhang ◽  
Chunmei Wu ◽  
EunSoo Kim ◽  
Michael M. Bernitsas
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbulence Control ◽  
Frequency Responses ◽  
Simulation Results ◽  
Passive Turbulence Control ◽  
Reynolds Average

The effect of tandem spacing on the flow induced motions (FIM) of two circular cylinders with passive turbulence control is investigated using two-dimensional Unsteady Reynolds-Average Navier-Stokes equations with the Spalart-Allmaras turbulence model. Results are compared to experiments in the range of Reynolds number of 30,000<Re<100,000. The center-to-center spacing between the two cylinders is varied from 2 to 6 diameters. Simulation results predict well all ranges of FIM including VIV and galloping and match well with experimental measurements. For the upstream cylinder, the amplitude and frequency responses are not considerably influenced by the downstream cylinder when the spacing is greater than 2D. For the downstream cylinder, a rising amplitude trend in the VIV upper branch can be observed in all cases as is typical of flows in the TrSL3 regime. The galloping branch merges with the VIV upper branch for spacing greater than 3D. Vortex structures show significant variation in different flow regimes in accordance with experimental observations. High-resolution post-processing shows that the interaction between the wakes of cylinders result in various types of FIM.

PANS Study of the Flow Around an Oscillating, Simplified Truck Cabin With Flow Control

2017 ◽  
Author(s):  
G. Minelli ◽  
S. Krajnović ◽  
B. Basara
Keyword(s):  
Flow Control ◽  
Stokes Equations ◽  
Numerical Study ◽  
Active Flow Control ◽  
Synthetic Jet ◽  
Navier Stokes ◽  
Dynamic Configuration ◽  
Navier Stokes Equations ◽  
Recirculation Bubble ◽  
Yaw Angle

This work presents an application of the Partially-Averaged Navier-Stokes equations for an external vehicle flow. In particular, the flow around a generic truck cabin is simulated. The PANS method is first validated against experiments and resolved LES on two static cases. As a consequence, PANS is used to study the effect of an active flow control (AFC) on a dynamic oscillating configuration. The oscillation of the model represents a more realistic ground vehicle flow, where gusts (of different nature) define the unsteadiness of the incoming flow. In the numerical study, the model is forced to oscillate with a yaw angle 10° > β > −10° and a non-dimensional frequency St = fW/Uinf = 0.1. The effect of the periodic motion of the model is compared with the quasi-steady flow condition. At a later stage, the dynamic configuration is actuated by means of a synthetic jet boundary condition. Overall, the effect of the actuation is beneficial. The actuation of the AFC decreases drag, stabilises the flow and reduces the size of the side recirculation bubble.

Computation of Slamming Forces on 3-D Bodies With a CIP Method

2010 ◽  
Author(s):  
Qingyong Yang ◽  
Wei Qiu
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Type Equation ◽  
Navier Stokes ◽  
Cip Method ◽  
Time Step ◽  
Constrained Interpolation ◽  
Navier Stokes Equations ◽  
Highly Nonlinear ◽  
Calm Water

This paper presents the numerical solutions of slamming problems for 3D bodies entering calm water. The highly nonlinear water entry problems are governed by the Navier-Stokes equations and were solved by a Constrained Interpolation Profile (CIP)-based finite difference method on a fixed Cartesian grid. In the computation, the 3D CIP method was employed for the advection calculations and a pressured-based algorithm was applied for non-advection calculations. The solid body and the free surface interfaces were captured by density functions. For the pressure computation, a Poisson-type equation was solved at each time step by the Conjugate Gradient iterative method. Validation studies were carried out for a 3D wedge entering calm water and the entry of a sphere into calm water at both vertical and horizontal velocities. The predicted hydrodynamic forces on the wedge and the sphere were compared with experimental data.

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