Hydrodynamic coefficients of a vertical circular cylinder

1990 ◽  
Vol 17 (3) ◽  
pp. 302-310 ◽  
Author(s):  
Michael Isaacson ◽  
Thomas Mathai ◽  
Carol Mihelcic
Keyword(s):  
Circular Cylinder ◽  
High Frequency ◽  
Closed Form Solution ◽  
Added Mass ◽  
Offshore Structures ◽  
Form Solution ◽  
Ocean Engineering ◽  
Radiation Problem ◽  
The Vertical Distribution ◽  
Linear Radiation

The added mass and the damping coefficient of a large surface-piercing circular cylinder extending to the seabed and undergoing horizontal oscillations are described. A closed-form solution to the corresponding linear radiation problem is obtained by the use of eigenfunction expansions. Attention is given to the vertical distribution of these coefficients and to their high-frequency asymptotic behaviour. Comparisons are made with experimental measurements. The application to typical offshore structures is discussed. Key words: added mass, cylinders, damping, hydrodynamics, ocean engineering.

Potential Flow Solution for Crossflow Impingement of a Slot Jet on a Circular Cylinder

1976 ◽  
Vol 98 (2) ◽  
pp. 249-255 ◽  
Author(s):  
H. Miyazaki ◽  
E. M. Sparrow
Keyword(s):  
Boundary Layer ◽  
Nusselt Number ◽  
Circular Cylinder ◽  
Potential Flow ◽  
Closed Form Solution ◽  
Form Solution ◽  
Stream Velocity ◽  
Cylinder Surface ◽  
Stagnation Region ◽  
Flow Solution

A closed-form solution has been obtained for the potential flow about a circular cylinder situated in an impinging slot jet. Among other results, the potential flow solution yields the free stream velocity for the boundary layer adjacent to the cylinder surface. A basic feature of the solution is the division of the flow field into subdomains, thereby making it possible to employ harmonic functions that are appropriate to each such subdomain. The boundary conditions on the free streamline and the conditions of continuity between the subdomains are satisfied by a combination of least squares and point matching constraints. Numerical evaluation of the solution was carried out for cylinder diameters greater or equal to the nozzle width and for a range of dimensionless separation distances between the nozzle and the impingement surface. Results are presented for the velocity and pressure distributions on the cylinder surface, for the position of the free streamline, and for the velocity gradients at the stagnation point. The latter serve as input information to the Nusselt number and skin friction expressions that are given by boundary layer theory. Comparisons were made with available experimental results for the pressure distribution, velocity gradient, and Nusselt number, and good agreement was found to prevail in the stagnation region.

Nonmodal Solution of Spherical Shells With Cutouts Excited by High-Frequency Axisymmetric Forces

1970 ◽  
Vol 37 (4) ◽  
pp. 977-983 ◽  
Author(s):  
M. C. Junger
Keyword(s):  
Boundary Conditions ◽  
High Frequency ◽  
Near Field ◽  
Closed Form Solution ◽  
Radial Force ◽  
Form Solution ◽  
Mode Shapes ◽  
High Frequency Response ◽  
Circular Cutout ◽  
Line Loads

A closed-form solution is obtained for the high-frequency response of a thin spherical shell embodying a circular cutout and excited axisymmetrically by a concentrated radial force. The solution is constructed by combining the shell response to the radial exciting force with its response to radial, tangential, and moment line loads applied along the cutout boundary, these line loads being selected to match the boundary conditions. Concise expressions for the shell response are obtained by applying the Sommerfeld-Watson transformation to the slowly converging high-frequency modal series which is thereby reduced to only two terms, viz., an exponentially decaying near-field and a standing or propagating-wave field. These two terms are in the nature of the creeping waves commonly used to formulate electromagnetic or acoustic diffracted wave fields in the short-wavelength limit. The method is illustrated for the simple case of a circular cutout with a clamped boundary, but lends itself to more complicated boundary conditions, viz., intersecting shells or wave guides. The natural frequencies and mode shapes are found from a single, characteristic equation involving trigonometric functions.

scholarly journals The Chow-Lin method extended to dynamic models with autocorrelated residuals

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Aurélien Poissonnier
Keyword(s):  
Closed Form ◽  
Capital Stock ◽  
High Frequency ◽  
Dynamic Models ◽  
Closed Form Solution ◽  
Dynamic Structure ◽  
Form Solution ◽  
Static Models ◽  
Temporal Disaggregation ◽  
Communication Equipment

AbstractI provide a closed-form solution to temporal disaggregation or interpolation models which is both general in terms of dynamic structure of the model (lags of the high-frequency variable) and flexible in terms of autocorrelation of its residual. As for static models, I show that assuming autocorrelated residuals in dynamic models is practically convenient. To illustrate the potential of the solution proposed, I provide an example for quarterly non-financial corporations’ capital stock in computers and communication equipment.

scholarly journals Added Mass and Damping of a Vibrating Rod in Confined Viscous Fluids

1976 ◽  
Vol 43 (2) ◽  
pp. 325-329 ◽  
Author(s):  
S. S. Chen ◽  
M. W. Wambsganss ◽  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Cylindrical Shell ◽  
Closed Form Solution ◽  
Added Mass ◽  
Form Solution ◽  
Viscous Fluids ◽  
Series Of Experiments ◽  
Theoretical Results ◽  
Good Agreement

This paper presents an analytical and experimental study of a cylindrical rod vibrating in a viscous fluid enclosed by a rigid, concentric cylindrical shell. A closed-form solution for the added mass and damping coefficient is obtained and a series of experiments with cantilevered rods vibrating in various viscous fluids is performed. Experimental data and theoretical results are in good agreement.

The Axially Loaded Circular Cylinder

1962 ◽  
Vol 29 (2) ◽  
pp. 318-320
Author(s):  
H. D. Conway
Keyword(s):  
Exact Solution ◽  
Fourier Transform ◽  
Circular Cylinder ◽  
Closed Form ◽  
Cross Sections ◽  
Closed Form Solution ◽  
Form Solution ◽  
Concentrated Force ◽  
Transform Method ◽  
Fourier Transform Method

Commencing with Kelvin’s closed-form solution to the problem of a concentrated force acting at a given point in an indefinitely extended solid, a Fourier transform method is used to obtain an exact solution for the case when the force acts along the axis of a circular cylinder. Numerical values are obtained for the maximum direct stress on cross sections at various distances from the force. These are then compared with the corresponding stresses from the solution for an infinitely long strip, and in both cases it is observed that the stresses are practically uniform on cross sections greater than a diameter or width from the point of application of the load.

Influence of added mass on ice impacts

1988 ◽  
Vol 15 (4) ◽  
pp. 698-708 ◽  
Author(s):  
Michael Isaacson ◽  
Kwok Fai Cheung
Keyword(s):  
Contact Point ◽  
Added Mass ◽  
Offshore Structures ◽  
Impact Model ◽  
Ocean Engineering ◽  
Offshore Structure ◽  
Proposed Model ◽  
Impact Problems ◽  
Ice Impacts ◽  
The Impact

The present paper applies potential theory to describe the variation of the added mass of an iceberg and its coupling effects on an offshore structure for various separation distances up to the point of contact. The strengths and weaknesses of the proposed model are discussed together with its practical application in ice mass impact problems. An impact model based on dynamic analysis is developed to calculate the impact force and response of a structure for head-on collisions. Both the contact-point added mass estimated in the present study and the traditionally assumed far-field added mass are used in the impact model separately. The results are compared and the crucial roles played by the ambient fluid during impact are discussed. Key words: added mass, hydrodynamics, ice impact, ocean engineering, offshore structures.

High frequency hydrodynamic coefficients of vertical cylinders

1992 ◽  
Vol 19 (4) ◽  
pp. 606-615
Author(s):  
Michael Isaacson ◽  
Thomas Mathai
Keyword(s):  
High Frequency ◽  
Scattering Problem ◽  
Offshore Structures ◽  
Short Wave ◽  
Alternative Methods ◽  
Local Form ◽  
Ocean Engineering ◽  
Damping Coefficients ◽  
Added Masses ◽  
Vertical Cylinders

Alternative methods of calculating high frequency added masses and damping coefficients of vertical cylinders of arbitrary section are described. Damping coefficients are calculated by a short-wave approximation relating to the local form of waves generated by the oscillating structure. As an alternative, they are also obtained from the exciting forces of the related scattering problem, with these forces obtained by a geometrical optics approximation. Added masses are obtained by discarding the propagating mode and using only the evanescent modes which are free of irregular frequencies. They are also obtained by an application of the Kramers–Kronig relations, which require the infinite frequency added masses and the damping coefficients at all frequencies. Numerical results obtained by the various methods are compared with corresponding analytical results for vertical circular and elliptic cylinders. The practical application of the proposed approach is indicated. Key words: added mass, cylinders, damping, hydrodynamics, ocean engineering, offshore structures, waves.

Nonlinear wave forces on a circular cylinder

1989 ◽  
Vol 16 (2) ◽  
pp. 182-187 ◽  
Author(s):  
Michael Isaacson ◽  
Qi-Hua Zuo
Keyword(s):  
Circular Cylinder ◽  
Nonlinear Wave ◽  
Perturbation Methods ◽  
Wave Force ◽  
Offshore Structures ◽  
Wave Forces ◽  
Ocean Engineering ◽  
Time Stepping ◽  
Wave Effects ◽  
Accuracy And Stability

Nonlinear wave forces on a surface-piercing vertical circular cylinder are considered using a time-stepping method previously developed which is based on Green's theorem. Possible improvements in the efficiency, accuracy, and stability of the method are considered. Results based on this method are compared with those obtained previously using perturbation methods as well as with experimental results. It is found that the time-stepping method adopted here is quite reasonable. Wave force coefficients are given as functions of the governing parameters of the problem and the importance of nonlinear wave effects on the forces is assessed. Key words: hydrodynamics, ocean engineering, offshore structures, waves, wave forces.

Nonlinear Vertical Vibration of Tension Leg Platforms with Homotopy Analysis Method

2015 ◽  
Vol 7 (3) ◽  
pp. 357-368 ◽  
Author(s):  
Arash Reza ◽  
Hamid M. Sedighi
Keyword(s):  
Differential Equation ◽  
Homotopy Analysis Method ◽  
Equations Of Motion ◽  
Closed Form Solution ◽  
Added Mass ◽  
Form Solution ◽  
Analysis Method ◽  
Homotopy Analysis ◽  
Mass Coefficient ◽  
Added Mass Coefficient

AbstractOne of the useful methods for offshore oil exploration in the deep regions is the use of tension leg platforms (TLP). The effective mass fluctuating of the structure which due to its vibration can be noted as one of the important issues about these platforms. With this description, dynamic analysis of these structures will play a significant role in their design. Differential equations of motion of such systems are nonlinear and providing a useful method for its analysis is very important. Also, the amount of added mass coefficient has a direct effect on the level of nonlinearity of partial differential equation of these systems. In this study, Homotopy analysis method has been used for closed form solution of the governing differential equation. Linear springs have been used for modeling the stiffness of this system and the effects of torsion, bending and damping of water have been ignored. In the study of obtained results, the effect of added mass coefficient has been investigated. The results show that increasing of this coefficient decreases the bottom amplitude of fluctuations and the system frequency. The obtained results from this method are in good agreement with the published results on the valid articles.

Influence of hydrodynamic effects on iceberg collisions

1990 ◽  
Vol 17 (3) ◽  
pp. 329-337 ◽  
Author(s):  
Michael Isaacson ◽  
Kevin McTaggart
Keyword(s):  
Added Mass ◽  
Offshore Structures ◽  
Ocean Engineering ◽  
Iceberg Drift ◽  
Added Masses ◽  
Waves And Currents ◽  
Fixed Structure ◽  
Wave Induced ◽  
Hydrodynamic Effects ◽  
Selection Of

This paper examines various hydrodynamic effects which should be considered when analyzing iceberg collisions with a fixed structure. Iceberg added mass is among the hydrodynamic parameters that must be known to evaluate collision severity. Effective added mass is shown to vary with collision duration and recommendations are made for the selection of added masses to be used in iceberg collision design. Iceberg impact velocities are influenced by waves and currents, which can both be significantly influenced by the presence of a large structure. Wave-driven iceberg drift motions are shown to be more sensitive than current-driven motions to the presence of a structure. The contribution of wave-induced oscillatory motions to impact velocity is also discussed. Key words: added mass, hydrodynamics, ice impact, icebergs, ocean engineering, offshore structures.

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