A Modal Solution for Scattering by an Arbitrary Isosceles Triangular Groove

2020 ◽  
Vol 68 (12) ◽  
pp. 8255-8259
Author(s):  
M. Bozorgi
Keyword(s):  
Modal Solution

Straked Riser Design With VIVA

2010 ◽  
Author(s):  
Dhyanjyoti Deka ◽  
Paul R. Hays ◽  
Kamaldev Raghavan ◽  
Mike Campbell
Keyword(s):  
Traveling Waves ◽  
Oil And Gas ◽  
Cross Flow ◽  
Oil And Gas Industry ◽  
Response Prediction ◽  
Design Tool ◽  
Mode Shapes ◽  
Fe Model ◽  
Viv Suppression ◽  
Modal Solution

VIVA is a vortex induced vibration (VIV) analysis software that to date has not been widely used as a design tool in the offshore oil and gas industry. VIVA employs a hydrodynamic database that has been benchmarked and calibrated against test data [1]. It offers relatively few input variables reducing the risk of user induced variability of results [2]. In addition to cross flow current induced standing wave vibration, VIVA has the capability of predicting traveling waves on a subsea riser, or a combination of standing and traveling waves. Riser boundary conditions including fixed, pinned, flex joint or SCR seabed interaction can be modeled using springs and dashpots. VIVA calculates riser natural frequencies and mode shapes and also has the flexibility to import external modal solutions. In this paper, the applicability of VIVA for the design of straked steel catenary risers (SCR) and top tensioned risers (TTR) is explored. The use of linear and rotational springs provided by VIVA to model SCR soil interaction and flex joint articulation is evaluated. Comparisons of the VIV fatigue damage output with internal and external modal solution is presented in this paper. This paper includes validation of the VIVA generated modal solution by comparing the modal frequencies and curvatures against a finite element (FE) model of the risers. Fatigue life is calculated using long term Gulf of Mexico (GoM) currents and is compared against the industry standard software SHEAR7. Three different lift curve selections in SHEAR7 are used for this comparison. The differences in riser response prediction by the two software tools are discussed in detail. The sensitivity of the VIVA predicted riser response to the absence of VIV suppression devices is presented in this paper. The riser VIV response with and without external FE generated modal input is compared and the relative merits of the two modeling approaches are discussed. Finally, the recommended approach for VIVA usage for SCR and TTR design is given.

Accelerated Multifidelity Emulator Modeling for Probabilistic Rotor Response Study

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Harok Bae ◽  
Ian M. Boyd ◽  
Emily B. Carper ◽  
Jeff Brown
Keyword(s):  
Prediction Accuracy ◽  
Point Cloud ◽  
Functional Relationship ◽  
Matrix Inversion ◽  
Numerical Examples ◽  
Computational Costs ◽  
New Approaches ◽  
Training Samples ◽  
Probabilistic Study ◽  
Modal Solution

Abstract This paper presents an efficient methodology to build a modal solution emulator for the probabilistic study of geometrically mistuned bladed rotors by using the newly developed localized-Galerkin multifidelity (LGMF) modeling and eigensolution reanalysis (ER) with the symmetric successive matrix inversion (SSMI) methods. The key idea of the mistuned blade emulator is to establish a reduced functional relationship between the stochastic geometric variations and the disturbed modal responses. The prediction accuracy of an emulator generally depends on how many training samples of modal solutions are available and how well the potential modal switching due to stochastic mistuning is captured. To reduce the computational costs of generating training samples without sacrificing accuracy, this paper introduces the collaborative framework of the new approaches of multifidelity (MF) modeling and ER. The proposed framework is demonstrated for its computational benefits with several numerical examples including the point-cloud scanned mistuned blade problem.

Coupling Sound Absorbing Materials With an Air Cavity Using Frequency Dependent Bulk Material Properties

2016 ◽  
Author(s):  
Shung H. Sung ◽  
Donald J. Nefske
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Material Properties ◽  
Complex Frequency ◽  
Air Cavity ◽  
Frequency Dependent ◽  
Absorbing Materials ◽  
Mode Method ◽  
Modal Solution ◽  
Solution Methodology

This paper presents the acoustic finite element method and the modal solution method for coupling sound absorbing materials with an air cavity to predict the sound pressure frequency response. The sound absorbing materials are represented with complex, frequency-dependent, effective mass-density and bulk-modulus properties obtained from the acoustic impedance of material samples. To couple the sound absorber cavity and air cavity, the boundary conditions at the interface between the cavities requires equality of pressure and equality of acoustic volume flow. Two modal solution methods are developed to compute the frequency response of the coupled system with frequency dependent material properties: the component mode method and the coupled mode method. The finite element and modal solution methodology is developed in a form readily adaptable for implementation in commercially available codes. The accuracy of the modal solution methodology is assessed for modeling a one-dimensional air tube terminated with absorbent material and the seats in an automobile passenger compartment.

An Exact Modal Analysis of the Static Deformation of Long Cylinders and Rings

1984 ◽  
Vol 106 (4) ◽  
pp. 348-353 ◽  
Author(s):  
H. D. Fisher
Keyword(s):  
Continuous Function ◽  
General Solution ◽  
Cross Section ◽  
Thin Shell ◽  
Present Theory ◽  
Angular Variable ◽  
Arbitrary Angle ◽  
Shell Equations ◽  
Modal Solution ◽  
Long Cylinder

This paper presents a static, modal solution of Flugge’s thin shell equations for the cases of a ring or a long cylinder in a state of plane strain. The solution derived here enables the design analyst to compute the deflection resulting from concentrated loads applied in the plane of the cross section at an arbitrary angle to the circumference of the shell and to eliminate the error which results, in certain cases, from employing a previously derived inextensional analysis. A general solution is given for the case of any number of concentrated radial, tangential, and moment loads. The method of analysis for loadings that are a continuous function of the angular variable is also illustrated via a specific example. Numerical results compare solutions obtained with the present theory with those computed by invoking the assumption of inextensional deformation.

Complex Modal Analysis of a Flat Belt Pulley System With Belt Damping and Coulomb-Damped Tensioner

1996 ◽  
Vol 118 (2) ◽  
pp. 306-311 ◽  
Author(s):  
T. C. Kraver ◽  
G. W. Fan ◽  
J. J. Shah
Keyword(s):  
Complex Model ◽  
Pulley System ◽  
Coulomb Damping ◽  
Future Extension ◽  
Analytical Development ◽  
Complex Modal Analysis ◽  
Vibration Coupling ◽  
Modal Solution ◽  
Belt System ◽  
Complex Modal

The effects of damping on rotational vibratory solutions of a multiple pulley—flat viscoelastomeric belt system with rotary arm tensioner is developed. A complex model procedure is developed to solve both underdamped and overdamped cases. This complex modal procedure allows for future extension to include nonsymmetric rotational models, such as transverse belt vibration coupling. The modal solution enables rapid analysis over a spectrum of frequencies. Seven pulley system experimental results reported in the literature support the analytical development. Belt damping has significant vibration and belt tension amplitude effects. Tensioner spring rate and coulomb damping has minor effects.

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