An Application of Mini-Computers for the Determination of Elastomeric Damping Coefficients and Other Properties

2009 ◽  
pp. 59-59-14 ◽  
Author(s):  
Donald M. Danko ◽  
James E. Svarovsky
Keyword(s):  
Damping Coefficients

Determination of the added masses and damping coefficients during coupled motions of two ships in shallow water parallel to the vertical wall

2021 ◽  
pp. 16-25
Author(s):  
В.Ю. Семенова ◽  
К.И. Баканов
Keyword(s):  
Shallow Water ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Hydrodynamic Coefficients ◽  
Damping Coefficients ◽  
Added Masses ◽  
Joint Motions ◽  
National Practice ◽  
Simultaneous Influence

В статье рассматривается определение коэффициентов демпфирования и присоединенных масс, возникающих при совместной качке двух судов в условиях мелководья параллельно вертикальной стенке на основании решения трехмерной потенциальной задачи. Определение гидродинамических коэффициентов осуществляется на основании методов интегральных уравнений и зеркальных отображений. Представленное решение в отечественной практике является новым. В статье приводятся результаты расчетов коэффициентов присоединенных масс и демпфирования, возникающих при качке двух одинаковых судов, расположенных лагом к волнению и параллельно вертикальной стенке в зависимости от изменения расстояний как между судами, так и между судами и вертикальной стенкой. Проводится исследование влияния различных фарватеров на величины гидродинамических коэффициентов, а именно: мелководного фарватера, мелководного фарватера с вертикальной стенкой, мелководного фарватера со вторым параллельно качающимся судном и мелководного фарватера с вертикальной стенкой и вторым судном. Таким образом, в работе учитывается одновременное влияния мелководья, вертикальной стенки и второго судна. Показано увеличение значений коэффициентов присоединенных масс и демпфирования при уменьшении расстояний между судами и между судами и вертикальной стенкой. Также показано значительное совместное влияние вертикальной стенки и второго судна на коэффициенты присоединенных масс и демпфирования по сравнению с другими видами стесненных фарватеров. The article discusses the determination of damping coefficients and added masses arising from the joint motions of two ships in shallow water conditions parallel to the vertical wall based on the solution of a three-dimensional potential problem. Determination of hydrodynamic coefficients is carried out on the basis of the methods of integral equations and mirror images. The solution presented in the national practice is new The article presents the results of calculating the coefficients of added masses and damping arising from the motions of two identical ships located lagged to the sea and parallel to the vertical wall, depending on the change in the distances between the ships and between the ships and the vertical wall. A study is being made of the influence of various waterways on the values ​​of hydrodynamic coefficients, namely: a shallow waterway, a shallow waterway with a vertical wall, a shallow waterway with a second parallel oscillating ship and a shallow waterway with a vertical wall and a second ship. Thus, the work takes into account the simultaneous influence of shallow water, vertical wall and the second ship. An increase in the values of the coefficients of added masses and damping with a decrease in the distances between ships and between ships and the vertical wall is shown. It also shows a significant combined effect of the vertical wall and the second ship on the added mass and damping coefficients in comparison with other types of constrained waterways.

On the harmonic oscillations of a rigid body on a free surface

1965 ◽  
Vol 21 (3) ◽  
pp. 427-451 ◽  
Author(s):  
W. D. Kim
Keyword(s):  
Integral Equation ◽  
Free Surface ◽  
Rigid Body ◽  
Potential Problem ◽  
Harmonic Oscillation ◽  
Added Mass ◽  
The Body ◽  
Rigorous Solution ◽  
Damping Coefficients

The present paper deals with the practical and rigorous solution of the potential problem associated with the harmonic oscillation of a rigid body on a free surface. The body is assumed to have the form of either an elliptical cylinder or an ellipsoid. The use of Green's function reduces the determination of the potential to the solution of an integral equation. The integral equation is solved numerically and the dependency of the hydrodynamic quantities such as added mass, added moment of inertia and damping coefficients of the rigid body on the frequency of the oscillation is established.

Technical Note: Rolling dynamic stiffness and damping characteristics of small-sized pneumatic tyres

2000 ◽  
Vol 214 (3) ◽  
pp. 243-248 ◽  
Author(s):  
V. H. Saran ◽  
V. K. Goel
Keyword(s):  
Normal Load ◽  
Dynamic Stiffness ◽  
Technical Note ◽  
Inflation Pressure ◽  
Laboratory Technique ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Stiffness And Damping

In this paper, a laboratory technique for determination of rolling dynamic stiffness and damping coefficients of small-sized, bias-ply tyres has been discussed. The effect of normal load, inflation pressure and speed on four different tyres has been reported. The results show similar trends to those reported by other investigators.

scholarly journals The initial research of dynamic parameters for composite structures containing Zeolite

2013 ◽  
Vol 12 (1) ◽  
pp. 283-290
Author(s):  
Jacek Szulej
Keyword(s):  
Composite Structures ◽  
Main Part ◽  
Time Course ◽  
Free Vibrations ◽  
Dynamic Parameters ◽  
Damping Coefficients ◽  
Modified Binder ◽  
Initial Results ◽  
Initial Research

The article aims at presenting the initial results of damping parameters of vibrations in constructions with zeolite. The initial part of the article describes the properties and application of zeolite. The influence of zeolite on concrete parameters was examined. The main part of the article displays the results of the analysis of damping parameters of vibration of three plate-beam models. The models contain modified binder in which the part of cement was replaced by zeolite (containing more than 85% of crinoptylolite). The analyses were based on the induction of vibration of models, the measurements of vibrations, the spectrum treatment of time course as well as the determination of values of damping coefficients of vibration. Hence the collation method was used. Moreover, the damping coefficients of the first three modes of free vibrations of models were determined.

Partitioning of pulmonary impedance: modeling vs. alveolar capsule approach

1993 ◽  
Vol 75 (2) ◽  
pp. 513-521 ◽  
Author(s):  
F. Petak ◽  
Z. Hantos ◽  
A. Adamicza ◽  
B. Daroczy
Keyword(s):  
Excellent Agreement ◽  
Input Impedance ◽  
Small Amplitude ◽  
Airway Resistance ◽  
Model Fitting ◽  
Damping Coefficients ◽  
Open Chest ◽  
Impedance Modeling ◽  
Isolated Lungs

Pulmonary input impedance (ZL), transfer tissue impedances (Ztti), and transfer airway impedances (Ztaw) were measured in open-chest dogs and isolated canine lungs by means of small-amplitude pseudorandom oscillations between 0.2 and 21.1 Hz. In the determination of Ztti and Ztaw, local alveolar pressures (PA) sensed in alveolar capsules were used. The global impedances of the airways (Zaw) and tissues (Zti) were estimated by fitting to the ZL data between 0.2 and 4.9 Hz (open-chest dogs) and between 0.2 and 5.9 Hz (isolated lungs) two models based on Hildebrandt's formulations (Bull. Math. Biophys. 31: 651–667, 1969), the parameters of which included airway resistance (Raw) and inertance (Iaw) and tissue damping (GL) and elastance (HL). The tissue parameters of Ztti (Gti and Hti) were also obtained from model fitting, whereas the Ztaw data were evaluated in terms of resistance (Rtaw) and inertance (Itaw). Excellent agreement was found between HL and Hti in both experimental groups and between GL and Gti in the isolated lungs (r > or = 0.999). The damping coefficients were also closely related in the open-chest dogs (r = 0.95), but Gti overestimated GL slightly (by 9%). Raw was underestimated by Rtaw (by 3–33%) and Iaw by Itaw (by 2–16%), depending on the model type and, in the excised lungs, the number of punctures in the capsules. In the case of the airway parameters, the systematic differences were accompanied by lower r values (0.535–0.935), which are explained primarily by the regional variations in PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental Determination of Roll Damping Coefficient for FPSO

2014 ◽  
Author(s):  
Oliver A. Seelis ◽  
Longbin Tao
Keyword(s):  
Experimental Determination ◽  
Cross Section ◽  
Test Data ◽  
Transfer Functions ◽  
Damping Coefficient ◽  
Roll Damping ◽  
Damping Coefficients ◽  
Decay Test ◽  
Bilge Keel

The roll damping coefficient is a crucial parameter for several design and operational aspects of FPSOs. The accurate prediction of the coefficient is not a trivial task and generally performed experimentally. A polynomial linearization of the decay test data has been widely applied in the offshore industry. However, research has indicated that for FPSOs with rectangular cross section and attached bilge keels, this methodology may lead to inaccurate damping coefficients. This paper presents a study on the experimental determination of roll damping coefficients for FPSOs, obtained by free decay tests. For this purpose model tests are executed in the towing tank of the Marine Hydrodynamic Laboratory at Newcastle University. The model is based on the design of a purposely build FPSO, as typically applied in the central North Sea sector. The cross section of the FPSO is boxed shaped with a characteristic knuckle shaped bilge. The tests are conducted using three different bilge keel arrangements. The parametric change in bilge keel size results in the variation of the flow characteristics around the bilge knuckle. The damping coefficients are then established from the decay test data using a polynomial approach, a bi-linear approach and a hyperbolic approach. A comparison between the damping evolutions obtained with the different methodologies is performed for each bilge keel configuration. Further, a numerical model of the FPSO is created using DNVs Sesam software. With the established damping coefficients, damping matrices are manually defined as an input to Sesam and roll transfer functions are numerically established. The computational determined transfer functions are then compared against the RAOs obtained from the model tests in regular waves to determine the most appropriate methodology. The damping coefficient for the bare hull is well established by all three proposed methodologies. However, with the attached bilge keels the bi-linear and the hyperbolic methodologies produce damping coefficients reflecting the experimental results more accurately than the polynomial approach, indicating that the recently developed hyperbolic method is a valid alternative, and in certain cases, is more suitable to determine the roll damping coefficient. The experimental measurements could serve as a benchmark for further research and contribute to the practical application of FPSO roll damping determination.

Determination of Fluid Damping Using Random Excitation

1985 ◽  
Vol 107 (2) ◽  
pp. 220-225 ◽  
Author(s):  
J. C. S. Yang ◽  
C. H. Marks ◽  
J. Jiang ◽  
D. Chen ◽  
A. Elahi ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Circular Cylinder ◽  
Random Excitation ◽  
Logarithmic Decrement ◽  
Random Decrement Technique ◽  
Damping Coefficients ◽  
Random Decrement ◽  
Fluid Damping ◽  
Random Decrement Method

An experimental investigation has been carried out to verify the validity of the use of the random decrement technique to determine the damping coefficients for a circular cylinder oscillating in water. Data are reported for amplitudes ranging from 0.4 diameters to 0.8 diameters, for water speeds from zero to 0.192 m/s (0.63 ft/sec), and for frequencies ranging from 0.37 Hz to 1.4 Hz. Comparison with other data, which has been reported in the literature or obtained by the authors, shows that the random decrement method yields comparable damping coefficients to those obtained using the logarithmic decrement technique for the range of variables in this experiment.

The Method of Harmonic Excitation for Determination of the Flexibility of the Support of Machine’s Rotor

2002 ◽  
Author(s):  
Jozef Rybczynski
Keyword(s):  
Rotor Dynamics ◽  
Harmonic Excitation ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Test Rig ◽  
Harmonic Force ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Made In

A series of experimental investigations were made in order to determine the set of coefficients of flexibility of construction supporting the rotor. The investigations were made on the test rig for the rotor dynamics investigation. A harmonic force of known amplitude was applied to all supports of the system to induce vibration of the system. Then the system’s reaction in the form of displacement in all connections at the same time was measured. On the bases of the experimental results a square 36-element (6×6) matrix of flexibility coefficients for each frequency of excitation was created. The matrices are the initial material to determine the modal masses, stiffness coefficients and damping coefficients in such form so that they could be the data to calculate the dynamics of the experimental rotor by means of computer programs. Moreover the experimental results are interesting information in the to analysis of the behavior of the test rig’s pedestals.

Sign in / Sign up

Export Citation Format

Share Document