Quasi-Linear Theory of Ship Wave Resistance and CFD Analysis of Ship’s Environmental Impact

2003 ◽  
Author(s):  
Eduard Amromin ◽  
Svetlana Kovinskaya ◽  
Marina Mizina ◽  
Igor Mizine
Keyword(s):  
Environmental Impact ◽  
Linear Theory ◽  
Nonlinear Waves ◽  
Wave Amplitude ◽  
Wave Resistance ◽  
Shallow Waters ◽  
Cfd Analysis ◽  
Test Results ◽  
Ship Wave ◽  
Stokes Waves

Quasi-linear theory (QLT) introduces corrections to the Havelock integral and makes it possible to operate with realistic wave amplitudes and length into framework of linear theory. These corrections for wave amplitude and length are based on implicit employment of the model 2D problems for nonlinear waves of highest magnitude (Stokes waves). There is both description of algorithms and comparison with towing test results for diverse ships here. A substantially novel (and environmentally important) aspect of this paper is application of QLT to computation of ship wave resistance in shallow waters.

Quasi-linear theory of waves and ship wave resistance in restricted waters

2004 ◽  
Vol 31 (10) ◽  
pp. 1231-1244 ◽  
Author(s):  
Eduard Amromin ◽  
Svetlana Kovinskaya ◽  
Igor Mizine
Keyword(s):  
Linear Theory ◽  
Wave Resistance ◽  
Ship Wave

A Slender-Ship Theory of Wave Resistance

1983 ◽  
Vol 27 (01) ◽  
pp. 13-33
Author(s):  
Francis Noblesse
Keyword(s):  
Froude Number ◽  
Wave Resistance ◽  
Successive Approximations ◽  
Zeroth Order ◽  
Remarkable Effect ◽  
Ship Wave ◽  
First Order ◽  
Wigley Hull ◽  
Low Froude Number ◽  
The Waves

A new slender-ship theory of wave resistance is presented. Specifically, a sequence of explicit slender-ship wave-resistance approximations is obtained. These approximations are associated with successive approximations in a slender-ship iterative procedure for solving a new (nonlinear integro-differential) equation for the velocity potential of the flow caused by the ship. The zeroth, first, and second-order slender-ship approximations are given explicitly and examined in some detail. The zeroth-order slender-ship wave-resistance approximation, r(0) is obtained by simply taking the (disturbance) potential, ϕ, as the trivial zeroth-order slender-ship approximation ϕ(0) = 0 in the expression for the Kochin free-wave amplitude function; the classical wave-resistance formulas of Michell [1]2 and Hogner [2] correspond to particular cases of this simple approximation. The low-speed wave-resistance formulas proposed by Guevel [3], Baba [4], Maruo [5], and Kayo [6] are essentially equivalent (for most practical purposes) to the first-order slender-ship low-Froude-number approximation, rlF(1), which is a particular case of the first-order slender-ship approximation r(1): specifically, the first-order slender-ship wave-resistance approximation r(1) is obtained by approximating the potential ϕ in the expression for the Kochin function by the first-order slender-ship potential ϕ1 whereas the low-Froude-number approximation rlF(1) is associated with the zero-Froude-number limit ϕ0(1) of the potentialϕ(1). A major difference between the first-order slender-ship potential ϕ(1) and its zero-Froude-number limit ϕ0(1) resides in the waves that are included in the potential ϕ(1) but are ignored in the zero-Froude-number potential ϕ0(1). Results of calculations by C. Y. Chen for the Wigley hull show that the waves in the potential ϕ(1) have a remarkable effect upon the wave resistance, in particular causing a large phase shift of the wave-resistance curve toward higher values of the Froude number. As a result, the first-order slender-ship wave-resistance approximation in significantly better agreement with experimental data than the low-Froude-number approximation rlF(1) and the approximations r(0) and rM.

Piston-Lift Check Valve Flow Verification Using CFD

2018 ◽  
Author(s):  
Matthew Laney ◽  
Ronald Farrell
Keyword(s):  
Flow Characteristics ◽  
Check Valve ◽  
Valve Lift ◽  
Cfd Analysis ◽  
Test Results ◽  
Finite Element Software ◽  
Translational Movement ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an extension of paper PVP2017-66269, “Check Valve Flow and Disk Lift Simulation Using CFD” [1], and utilizes some of the same concepts to characterize flow through piston-lift check valves. The previous example considered a swing check valve involving rotational movement; this example considers a vertical lift piston check valve involving translational movement. Specifically, CFD was used to determine valve flow coefficients (CV) as a function of disk lift position as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The CFX application, which is part of the ANSYS suite of finite element software, was used to determine the flow characteristics. As presented in PVP2017-66269, balancing flow-induced forces on the check element and considering the disk assembly weight, the valve lift behavior can be predicted. Results from the CFX analysis were compared to recent test results of a skirted disk-piston check valve and previous test results of a standard disk-piston check valve. The results showed good agreement in most cases. This validates that flow characteristics across valves with different types of check elements at different disk lift positions can be reliably predicted using CFD analysis. It is important to note that while the test results and CFD analysis showed good agreement, it was vital that actual testing be performed in order to validate the approach. This follows the recommendation outlined in the previous paper.

scholarly journals On Offshore Propagating Diurnal Waves

2012 ◽  
Vol 69 (5) ◽  
pp. 1562-1581 ◽  
Author(s):  
Qingfang Jiang
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Linear Theory ◽  
Wave Amplitude ◽  
Trapped Waves ◽  
Stable Layer ◽  
Free Atmosphere ◽  
Heating Source ◽  
Differential Heating ◽  
Heating Profiles

Abstract Characteristics and dynamics of offshore diurnal waves induced by land–sea differential heating are examined using linear theory. Two types of heating profiles are investigated, namely a shallow heating source confined within an atmospheric boundary layer (BL) and a deep heating source located above the boundary layer. It is demonstrated that a boundary layer top inversion or a more stable layer aloft tends to partially trap diurnal waves in the BL and consequently extend perturbations well offshore. The wave amplitude decays with offshore distance due to BL friction and leakage of energy into the free atmosphere. The dependence of trapped waves on the inversion height and strength, atmosphere stratification, latitude, BL friction, and background winds is investigated. Diurnal waves generated by a deep heating source extending well above the BL are characterized by longer wavelengths, faster propagation, and substantially longer e-folding decay distances than waves induced by a BL source. For the latter, BL friction has little impact on the e-folding decay distance, as waves are mostly located in the free atmosphere rather than in a frictional BL.

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