scholarly journals Prediction of transient loading on a propeller from an approching ice block

1970 ◽  
Vol 2 (1) ◽  
pp. 15-20 ◽  
Author(s):  
P Liu ◽  
B Colbourne ◽  
Chin Shin
Keyword(s):  
Numerical Models ◽  
Panel Method ◽  
The Body ◽  
Source Distribution ◽  
Hydrodynamic Load ◽  
Surface Panel Method ◽  
Time Step ◽  
Suction Force ◽  
Propeller Blades ◽  
Marine Engineering

An unsteady 3D surface panel method has been developed to predict hydrodynamic load fluctuations on an ice class propeller induced by continuous variation of proximity to an ice block. The low order, time domain, combined doublet and source panel method approximates the doublet and source distribution uniformly over each panel on the propeller blades. For non-lifting bodies, i.e., the hub and ice block, only sources are distributed over the body surfaces. The simulation model is contrived in such a manner that the ice block and surrounding fluid remain stationary; and at each time step, the propeller rotates and advances forward in the inertial reference frame. This numerical model is validated with previous fixed-proximity experimental measurements and good agreement is obtained. Prediction of the fluctuating hydrodynamic load is carried out as a full dynamic interaction between the ice block and the propeller. Results for this study are compared with previous fixed-proximity numerical models and experiments. The new dynamic model establishes a basis for analysis of a more realistic fluid-structure interaction, which could, in the future, include ice block acceleration due to suction force and ice block impact loading on the propeller blade and shaft. Keywords: Marine Propulsion, Panel Methods, Unsteady Loading, Ice-Propeller Interaction doi: 10.3329/jname.v2i1.2026 Journal of Naval Architecture and Marine Engineering 2(1)(2005) 15-20

Time Domain Computation of the Wave-Making Resistance of Ships

2005 ◽  
Vol 49 (02) ◽  
pp. 144-158 ◽  
Author(s):  
F. Kara ◽  
D. Vassalos
Keyword(s):  
Steady State ◽  
Time Domain ◽  
Three Dimensional ◽  
Impulse Response Function ◽  
The Body ◽  
Source Distribution ◽  
Research Centre ◽  
Surface Source ◽  
Calm Water ◽  
Marine Engineering

The Ship Stability Research Centre, Department of Naval Architecture and Marine Engineering, The Universities of Glasgow and Strathclyde, Scotland, UKA linearized three-dimensional potential flow formulation in time domain is applied to calculate wave-making resistance of ships in calm water. Steady-state perturbation potentials for resistance are obtained as the steady-state limit of the surge radiation impulse response function using the transient free surface source distribution over the body surface. Five different vessels are used to validate the present numerical approximation. The results, including steady-state wave-making resistance, sinkage force, trim moment, and wave profile along the waterline, are compared with other published numerical and experimental results.

Application of a Boundary Element Method for Wave-Body Interaction Problems Considering the Non-Linear Water Surface

2017 ◽  
Author(s):  
Daniel Ferreira González ◽  
Jonas Bechthold ◽  
Moustafa Abdel-Maksoud
Keyword(s):  
Water Surface ◽  
Three Dimensional ◽  
Free Water ◽  
Numerical Approach ◽  
Panel Method ◽  
The Body ◽  
Time Step ◽  
Non Linear ◽  
Wigley Hull ◽  
Tank Test

In this paper an existing time domain panel method, which was originally developed for propeller flow simulations, is extended by implementing the mixed Eulerian-Lagrangian approach for the computation of the non-linear free water surface. The three-dimensional panel method uses a constant source and doublet density distribution on each panel and a Dirichlet boundary condition to solve the velocity potential in every time step. Additionally, a formulation for the acceleration potential is included in order to determine the hydrodynamic forces accurately. The paper gives an overview on the governing equations and introduces the numerical approach. Validation results of the developed method are presented for the wave resistance of a submerged spheroid and a wigley hull. Additionally, the wave diffraction due to a surface piercing cylinder in regular waves is validated regarding the forces and the water surface elevation around the body. Here, the computations are compared with other numerical methods as well as tank test results. Apart from this, the paper deals with an application example showing simulations of an artificial service vessel catamaran in waves. The forces on the hull with and without forward speed are presented. The paper concludes with a discussion of the presented results and a brief outlook on further work.

scholarly journals Computation of ship responses in waves using panel method

1970 ◽  
Vol 1 (1) ◽  
pp. 35-46 ◽  
Author(s):  
MN Islam ◽  
MR Islam ◽  
MS Baree
Keyword(s):  
Green Function ◽  
Degrees Of Freedom ◽  
Velocity Potential ◽  
Panel Method ◽  
Numerical Code ◽  
Source Distribution ◽  
Forward Speed ◽  
Six Degrees Of Freedom ◽  
Marine Engineering ◽  
Speed Effect

Hydrodynamic coefficients, Forces / Moments and Motions of a ship moving with a mean forward speed in six degrees of freedom are computed using Panel Method. In this study, an existing numerical model without speed consideration was modified by incorporating the speed parameters. Appropriate Green function was used to calculate the concern velocity potential. The accuracy of the developed numerical code employing the Panel Method has been validated by comparing the result with known/published results of a series 60 ship available in the literature. Based on the results presented in the paper, it can be concluded that the developed model is able to predict the responses of the ship with forward speed effect. Keywords: Motions, Green function, 3D Source distribution.   doi: 10.3329/jname.v1i1.2037 Journal of Naval Architecture and Marine Engineering 1(2004) 35-46

NUMERICAL SOLUTIONS OF 2D AND 3D SLAMMING PROBLEMS

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
Q Yang ◽  
W Qiu
Keyword(s):  
Free Surface ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Type Equation ◽  
The Body ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Highly Nonlinear ◽  
2D And 3D

Slamming forces on 2D and 3D bodies have been computed based on a CIP method. The highly nonlinear water entry problem governed by the Navier-Stokes equations was solved by a CIP based finite difference method on a fixed Cartesian grid. In the computation, a compact upwind scheme was employed for the advection calculations and a pressure-based algorithm was applied to treat the multiple phases. The free surface and the body boundaries were captured using density functions. For the pressure calculation, a Poisson-type equation was solved at each time step by the conjugate gradient iterative method. Validation studies were carried out for 2D wedges with various deadrise angles ranging from 0 to 60 degrees at constant vertical velocity. In the cases of wedges with small deadrise angles, the compressibility of air between the bottom of the wedge and the free surface was modelled. Studies were also extended to 3D bodies, such as a sphere, a cylinder and a catamaran, entering calm water. Computed pressures, free surface elevations and hydrodynamic forces were compared with experimental data and the numerical solutions by other methods.

scholarly journals Calculation of Three-Dimensional Unteady Sheet Cavitation by a Simple Surface Panel Method

2000 ◽  
Vol 2000 (188) ◽  
pp. 91-103 ◽  
Author(s):  
Jun Ando ◽  
Takashi Kanemaru ◽  
Kunihide Ohashi ◽  
Kuniharu Nakatake
Keyword(s):  
Three Dimensional ◽  
Panel Method ◽  
Surface Panel Method ◽  
Sheet Cavitation ◽  
Simple Surface

Large-amplitude undulatory fish swimming: fluid mechanics coupled to internal mechanics

1999 ◽  
Vol 202 (23) ◽  
pp. 3431-3438 ◽  
Author(s):  
T.J. Pedley ◽  
S.J. Hill
Keyword(s):  
Vortex Ring ◽  
Large Amplitude ◽  
Muscle Activation ◽  
Bending Moment ◽  
Hydrodynamic Pressure ◽  
Moment Equation ◽  
Panel Method ◽  
The Body ◽  
Undulatory Swimming ◽  
Body Theory

The load against which the swimming muscles contract, during the undulatory swimming of a fish, is composed principally of hydrodynamic pressure forces and body inertia. In the past this has been analysed, through an equation for bending moments, for small-amplitude swimming, using Lighthill's elongated-body theory and a ‘vortex-ring panel method’, respectively, to compute the hydrodynamic forces. Those models are outlined in this review, and a summary is given of recent work on large-amplitude swimming that has (a) extended the bending moment equation to large amplitude, which involves the introduction of a new (though probably usually small) term, and (b) developed a large-amplitude vortex-ring panel method. The latter requires computation of the wake, which rolls up into concentrated vortex rings and filaments, and has a significant effect on the pressure on the body. Application is principally made to the saithe (Pollachius virens). The calculations confirm that the wave of muscle activation travels down the fish much more rapidly than the wave of bending.

Large-Amplitude Transient Motion of Two-Dimensional Floating Bodies

1979 ◽  
Vol 23 (01) ◽  
pp. 20-31
Author(s):  
R. B. Chapman
Keyword(s):  
Boundary Condition ◽  
Wave Field ◽  
Large Amplitude ◽  
The Body ◽  
Body Motion ◽  
Source Distribution ◽  
Floating Body ◽  
Two Dimensional ◽  
Body Boundary ◽  
Free Mode

A numerical method is presented for solving the transient two-dimensional flow induced by the motion of a floating body. The free-surface equations are linearized, but an exact body boundary condition permits large-amplitude motion of the body. The flow is divided into two parts: the wave field and the impulsive flow required to satisfy the instantaneous body boundary condition. The wave field is represented by a finite sum of harmonics. A nonuniform spacing of the harmonic components gives an efficient representation over specified time and space intervals. The body is represented by a source distribution over the portion of its surface under the static waterline. Two modes of body motion are discussed—a captive mode and a free mode. In the former case, the body motion is specified, and in the latter, it is calculated from the initial conditions and the inertial properties of the body. Two examples are given—water entry of a wedge in the captive mode and motion of a perturbed floating body in the free mode.

A Nonlinear Optimal Control Approach for the Vertical Take-off and Landing Aircraft

2021 ◽  
pp. 2150012
Author(s):  
G. Rigatos
Keyword(s):  
Optimal Control ◽  
Control Method ◽  
Nonlinear Optimal Control ◽  
The Body ◽  
Algebraic Riccati Equation ◽  
Control Input ◽  
Time Step ◽  
Control Approach ◽  
Vtol Aircraft ◽  
Optimal Control Approach

The paper proposes a nonlinear optimal control approach for the model of the vertical take-off and landing (VTOL) aircraft. This aerial drone receives as control input a directed thrust, as well as forces acting on its wing tips. The latter forces are not perpendicular to the body axis of the drone but are tilted by a small angle. The dynamic model of the VTOL undergoes approximate linearization with the use of Taylor series expansion around a temporary operating point which is recomputed at each iteration of the control method. For the approximately linearized model, an H-infinity feedback controller is designed. The linearization procedure relies on the computation of the Jacobian matrices of the state-space model of the VTOL aircraft. The proposed control method stands for the solution of the optimal control problem for the nonlinear and multivariable dynamics of the aerial drone, under model uncertainties and external perturbations. For the computation of the controller’s feedback gains, an algebraic Riccati equation is solved at each time-step of the control method. The new nonlinear optimal control approach achieves fast and accurate tracking for all state variables of the VTOL aircraft, under moderate variations of the control inputs. The stability properties of the control scheme are proven through Lyapunov analysis.

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