Investigation on Motion and Load Response of a Fpso in Regular Waves by Fully Nonlinear Method

2021 ◽  
Author(s):  
Jiale Wang ◽  
Shili Sun ◽  
Hui-Long Ren
Keyword(s):  
Regular Waves ◽  
Nonlinear Method ◽  
Fully Nonlinear ◽  
Load Response ◽  
Fully Nonlinear Method

Investigation on Heave Motion and Load Response of a FPSO in Regular Waves by Fully Nonlinear Method

2020 ◽  
Author(s):  
Jia-Le Wang ◽  
Shi-Li Sun ◽  
Hui-Long Ren
Keyword(s):  
Free Surface ◽  
Dynamic Analysis ◽  
Time Domain ◽  
Mooring System ◽  
Analysis Method ◽  
Regular Waves ◽  
Nonlinear Method ◽  
Time Step ◽  
Load Response ◽  
Heave Motion

Abstract In this paper, the full nonlinear method based on the three-dimensional potential flow theory and the dynamic analysis method of flexible components are combined to simulate the motion and load response of a FPSO in waves. On the boundary of the hull body, the coupled motions are considered in the impenetrable condition. An improved Eulerian method is adopted to trace strongly nonlinear 3-D free surface deformation. In the far field, artificial damping zone is applied to eliminate reflected wave. Rankine source method is adopted to solve the velocity potential in time domain. Hydrodynamic mesh on hull body is generated by using accumulative chord length cubic parameter spline function. After solving Poisson equation, the initial mesh on free surface becomes orthogonal. In each time step, elastic-mesh-technique (EMT) is used to optimize the mesh on free surface. Several auxiliary functions are introduced to decouple the motions and load, and then the fourth-order Runge-Kutta method is adopted to update the numerical model in time domain. For the forces of the mooring system on the hull at each time step, the dynamic equation of the flexible member is established by the dynamic analysis method based on the elastic slender rod mechanical model, and then the equation is discretized into matrix form by the finite element discretization method and solved. The coupled motion of FPSO hull and mooring system in regular waves of various frequencies in various directions is simulated, and the time domain solutions are obtained. RAO of heave motion in each wave direction is given. The load response at the midship section is analyzed.

THE RISK OF HITTING THE ZERO LOWER BOUND AND THE OPTIMAL INFLATION TARGET

2017 ◽  
Vol 22 (2) ◽  
pp. 402-425 ◽  
Author(s):  
Phuong V. Ngo
Keyword(s):  
Lower Bound ◽  
Nonlinear Function ◽  
Zero Lower Bound ◽  
Nonlinear Method ◽  
Linear Quadratic ◽  
Inflation Target ◽  
Fully Nonlinear ◽  
Optimal Target ◽  
Dynamic Stochastic ◽  
Fully Nonlinear Method

I examine the optimal inflation target in a dynamic stochastic New Keynesian model featuring an occasionally binding zero lower bound on nominal interest rate (ZLB). To this end, I first calibrate the shock needed to generate the risk of hitting the ZLB that matches the U.S. data, based on a fully nonlinear method. I then resolve the model with different inflation targets and find that the optimal target is 3.4%. In addition, the optimal inflation target is a nonlinear function of the risk of hitting the ZLB and inflation indexation. It is always greater than 2% if the risk is greater than 2.5% or if the inflation indexation is higher than 0.5. Finally, the linear–quadratic approach overestimates the true optimal inflation target. In particular, based on the benchmark calibration, it generates an optimal target of 5.5%, compared with 3.4% found by the fully nonlinear method.

scholarly journals A method for computing unsteady fully nonlinear interfacial waves

1997 ◽  
Vol 351 ◽  
pp. 223-252 ◽  
Author(s):  
JOHN GRUE ◽  
HELMER ANDRÉ FRIIS ◽  
ENOK PALM ◽  
PER OLAV RUSÅS
Keyword(s):  
Solitary Waves ◽  
Bottom Topography ◽  
The Body ◽  
Interfacial Waves ◽  
Nonlinear Method ◽  
Fully Nonlinear ◽  
Weakly Nonlinear ◽  
Taylor Series Expansions ◽  
Layer Flow ◽  
Fully Nonlinear Method

We derive a time-stepping method for unsteady fully nonlinear two-dimensional motion of a two-layer fluid. Essential parts of the method are: use of Taylor series expansions of the prognostic equations, application of spatial finite difference formulae of high order, and application of Cauchy's theorem to solve the Laplace equation, where the latter is found to be advantageous in avoiding instability. The method is computationally very efficient. The model is applied to investigate unsteady trans-critical two-layer flow over a bottom topography. We are able to simulate a set of laboratory experiments on this problem described by Melville & Helfrich (1987), finding a very good agreement between the fully nonlinear model and the experiments, where they reported bad agreement with weakly nonlinear Korteweg–de Vries theories for interfacial waves. The unsteady transcritical regime is identified. In this regime, we find that an upstream undular bore is generated when the speed of the body is less than a certain value, which somewhat exceeds the critical speed. In the remaining regime, a train of solitary waves is generated upstream. In both cases a corresponding constant level of the interface behind the body is developed. We also perform a detailed investigation of upstream generation of solitary waves by a moving body, finding that wave trains with amplitude comparable to the thickness of the thinner layer are generated. The results indicate that weakly nonlinear theories in many cases have quite limited applications in modelling unsteady transcritical two-layer flows, and that a fully nonlinear method in general is required.

scholarly journals DOES CALVO MEET ROTEMBERG AT THE ZERO LOWER BOUND?

2019 ◽  
pp. 1-22 ◽  
Author(s):  
Jianjun Miao ◽  
Phuong V. Ngo
Keyword(s):  
Lower Bound ◽  
Interest Rates ◽  
Resource Constraints ◽  
Order Approximation ◽  
Adjustment Costs ◽  
Zero Lower Bound ◽  
Nonlinear Method ◽  
The Difference ◽  
Fully Nonlinear Method ◽  
First Order Approximation

This paper compares the conventional Calvo and Rotemberg price adjustments at the zero lower bound (ZLB) on nominal interest rates. Although the two pricing mechanisms are equivalent to a first-order approximation around the zero-inflation steady state, they produce very different results, based on a fully-nonlinear method. Specifically, the nominal interest rate hits the ZLB more frequently in the Calvo model than in the Rotemberg model. At the ZLB, deflation is larger and recessions are more severe in the Calvo model. The main reason for the difference in results is that price adjustment costs show up in the resource constraints in the Rotemberg. When they are rebated to the household, the two models behave similarly.

The inverse water wave problem of bathymetry detection

2013 ◽  
Vol 714 ◽  
pp. 562-590 ◽  
Author(s):  
Vishal Vasan ◽  
Bernard Deconinck
Keyword(s):  
Numerical Solution ◽  
Water Wave ◽  
Bottom Topography ◽  
Wave Surface ◽  
Nonlinear Method ◽  
Wave Problem ◽  
Water Wave Problem ◽  
Ill Posed ◽  
Non Local ◽  
Fully Nonlinear Method

AbstractThe inverse water wave problem of bathymetry detection is the problem of deducing the bottom topography of the seabed from measurements of the water wave surface. In this paper, we present a fully nonlinear method to address this problem in the context of the Euler equations for inviscid irrotational fluid flow with no further approximation. Given the water wave height and its first two time derivatives, we demonstrate that the bottom topography may be reconstructed from the numerical solution of a set of two coupled non-local equations. Owing to the presence of growing hyperbolic functions in these equations, their numerical solution is increasingly difficult if the length scales involved are such that the water is sufficiently deep. This reflects the ill-posed nature of the inverse problem. A new method for the solution of the forward problem of determining the water wave surface at any time, given the bathymetry, is also presented.

Numerical Integration of the 3D Unsteady Euler Equations for Flutter Analysis of Axial Flow Compressors

1988 ◽  
Author(s):  
G. A. Gerolymos
Keyword(s):  
Euler Equations ◽  
Single Channel ◽  
Axial Flow ◽  
Nonlinear Method ◽  
Periodicity Condition ◽  
Flow Through ◽  
Fully Nonlinear Method ◽  
Flow Compressor ◽  
The Time Domain ◽  
Transonic Fan

In order to analyze axial-flow compressor flutter, methods are required that compute the unsteady flow through vibrating cascades. A 3D fully nonlinear method has been developed by numerically integrating the 3D unsteady Euler equations, in the time-domain. The equations are discretized in a moving grid, which conforms with the vibrating blades and are integrated using the explicit MacCormack scheme, in finite-difference formulation. The method assumes a traveling-wave assembly mode of vibration. In this manner, the flow is computed in a single channel by applying the corresponding chorochronical periodicity condition at the permeable pitchwise limits. The blade vibratory mode is an input to the method obtained by a standard finite element method structural analysis code. A number of results are presented, for a transonic fan rotor, illustrating the possibilities of the method, both in started and unstarted supersonic flow conditions.

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