Modeling VIV Supression Using Negative Lift Coefficients

2011 ◽  
Author(s):  
Vikas Jhingran ◽  
Johnny Vogiatzis
Keyword(s):  
Vortex Shedding ◽  
Lift Coefficient ◽  
Effective Means ◽  
Balance Of Power ◽  
Power Input ◽  
Measured Data ◽  
Structure Interaction ◽  
Offshore Risers ◽  
Semi Empirical ◽  
Interaction Problem

Vortex-Induced Vibration (VIV) is a complex, non-linear fluid-structure interaction problem with important consequences for offshore risers, tendons and other tubulars. The prevalent approach in the industry is to use semi-empirical formulations to estimate VIV amplitudes, frequencies and the resulting fatigue damage. These semi-empirical techniques estimate VIV response amplitude by considering the balance of power input into the pipe due to vortex-shedding and the loss of power from the pipe due to damping. At the heart of this method are lift coefficient curves, which are used to estimate power input into the pipe. A key difficulty of this method is modeling the response of pipes with mitigation devices (strakes and fairings). This paper discusses the use of negative lift coefficient curves for estimating VIV response from mitigation devices. The author’s show how damping is handled in Shear7 using this approach. Results of comparisons between predicted and measured data show that negative lift curves are an effective means of modeling damping from VIV mitigation devices.

Lift Coefficient Curves for Predicting Response Using Shear7

2010 ◽  
Author(s):  
Vikas Jhingran ◽  
Johnny Vogiatzis
Keyword(s):  
Lift Coefficient ◽  
Balance Of Power ◽  
Power Input ◽  
Measured Data ◽  
Flexible Pipe ◽  
Structure Interaction ◽  
New Family ◽  
Offshore Risers ◽  
Semi Empirical ◽  
Interaction Problem

Vortex-Induced Vibration (VIV) is a complex, non-linear fluid-structure interaction problem with important consequences for offshore risers, tendons and other tubulars. The prevalent approach in the industry is to use semi-empirical formulations to estimate VIV amplitudes, frequencies and the resulting fatigue damage. These semi-empirical techniques estimate VIV response amplitude by considering the balance of power input into the pipe due to vortex-shedding and the loss of power from the pipe due to damping. At the heart of this method are lift coefficient curves, which are used to estimate power input into the pipe. Local lift coefficients are difficult to measure or derive for a flexible pipe and hence most of the lift curves used today have been developed using experiments with rigid cylinders. This paper discusses the development of a new family of lift coefficient curves using experimental data. Results of comparisons between predicted and measured data show the lift curves to effectively predict VIV response.

scholarly journals Investigation of a Stochastic Inverse Method to Estimate an External Force: Applications to a Wave-Structure Interaction

2012 ◽  
Vol 2012 ◽  
pp. 1-25 ◽  
Author(s):  
S. L. Han ◽  
Takeshi Kinoshita
Keyword(s):  
External Force ◽  
Inverse Method ◽  
Inverse Function ◽  
Wave Structure ◽  
Dynamic Responses ◽  
Structure Interaction ◽  
External Forces ◽  
Interaction Problem ◽  
Wave Structure Interaction

The determination of an external force is a very important task for the purpose of control, monitoring, and analysis of damages on structural system. This paper studies a stochastic inverse method that can be used for determining external forces acting on a nonlinear vibrating system. For the purpose of estimation, a stochastic inverse function is formulated to link an unknown external force to an observable quantity. The external force is then estimated from measurements of dynamic responses through the formulated stochastic inverse model. The applicability of the proposed method was verified with numerical examples and laboratory tests concerning the wave-structure interaction problem. The results showed that the proposed method is reliable to estimate the external force acting on a nonlinear system.

Analysis of Acoustic-Structure Interaction Using a High-Order Doubly Asymptotic Approximation

2016 ◽  
Vol 24 (01) ◽  
pp. 1550021 ◽  
Author(s):  
Heekyu Woo ◽  
Young S. Shin
Keyword(s):  
Order Approximation ◽  
Stable Model ◽  
Approximation Model ◽  
Third Order ◽  
Acoustic Structure ◽  
Structure Interaction ◽  
Proposed Model ◽  
The Stability ◽  
Third Order Approximation ◽  
Interaction Problem

In this paper, a new third-order approximation model for an acoustic-structure interaction problem is introduced. The new approximation model is designed to be an accurate and a stable model for predicting the response of a submerged structure. The proposed model is obtained by combining two lower order approximation models instead of using an operator matching method. The stability of this model is checked by a modal analysis. Finally, the approximation model is coupled to the spherical shell structure, and its performance is checked by a shock analysis.

An implicit full Eulerian method for the fluid-structure interaction problem

2010 ◽  
Vol 65 (1-3) ◽  
pp. 150-165 ◽  
Author(s):  
S. Ii ◽  
K. Sugiyama ◽  
S. Takeuchi ◽  
S. Takagi ◽  
Y. Matsumoto
Keyword(s):  
Fluid Structure Interaction ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Eulerian Method ◽  
Interaction Problem

scholarly journals Space/time multigrid for a fluid–structure-interaction problem

2008 ◽  
Vol 58 (12) ◽  
pp. 1951-1971 ◽  
Author(s):  
E.H. van Brummelen ◽  
K.G. van der Zee ◽  
R. de Borst
Keyword(s):  
Fluid Structure Interaction ◽  
Space Time ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Interaction Problem

A Tailored Nonlinear Slat-Cove Filler for Airframe Noise Reduction

2018 ◽  
Author(s):  
Gaetano Arena ◽  
Rainer Groh ◽  
Alberto Pirrera ◽  
William Scholten ◽  
Darren Hartl ◽  
...  
Keyword(s):  
High Strain ◽  
Interaction Analysis ◽  
Effective Means ◽  
Leading Edge ◽  
Structural Behavior ◽  
Deployable Structures ◽  
Airframe Noise ◽  
Structure Interaction ◽  
Slat Noise ◽  
Displacement Constraints

Exploiting mechanical instabilities and elastic nonlinearities is an emerging means for designing deployable structures. This methodology is applied here to investigate and tailor a morphing component used to reduce airframe noise, known as a slat-cove filler (SCF). The vortices in the cove between the leading edge slat and the main wing are among the important sources of airframe noise. The concept of an SCF was proposed in previous works as an effective means of mitigating slat noise by directing the airflow along an acoustically favorable path. A desirable SCF configuration is one that minimizes: (i) the energy required for deployment through a snap-through event; (ii) the severity of the snap-through event, as measured by kinetic energy, and (iii) mass. Additionally, the SCF must withstand cyclical fatigue stresses and displacement constraints. Both composite and shape memory alloy (SMA)-based SCFs are considered during approach and landing maneuvers because the deformation incurred in some regions may not demand the high strain recoverable capabilities of SMA materials. Nonlinear structural analyses of the dynamic behavior of a composite SCF are compared with analyses of similarly tailored SMA-based SCF and a reference, uniformly thick superelastic SMA-based SCF. Results show that by exploiting elastic nonlinearities, both the tailored composite and SMA designs decrease the required actuation energy compared to the uniformly thick SMA. Additionally, the choice of composite material facilitates a considerable weight reduction where the deformation requirement permits its use. Finally, the structural behavior of the SCF designs in flow are investigated by means of preliminary fluid-structure interaction analysis.

scholarly journals Effect of Cylinder Gap Ratio on The Wake of a Circular Cylinder Enclosed by Various Perforated Shrouds

CFD letters ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 51-68
Author(s):  
Nurul Azihan Ramli ◽  
Azlin Mohd Azmi ◽  
Ahmad Hussein Abdul Hamid ◽  
Zainal Abidin Kamarul Baharin ◽  
Tongming Zhou
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Control Method ◽  
Lift Coefficient ◽  
Base Case ◽  
Bluff Bodies ◽  
Ansys Fluent ◽  
Gap Ratio ◽  
Spacing Ratio

Flow over bluff bodies produces vortex shedding in their wake regions, leading to structural failure from the flow-induced forces. In this study, a passive flow control method was explored to suppress the vortex shedding from a circular cylinder that causes many problems in engineering applications. Perforated shrouds were used to control the vortex shedding of a circular cylinder at Reynolds number, Re = 200. The shrouds were of non-uniform and uniform holes with 67% porosity. The spacing gap ratio between the shroud and the cylinder was set at 1.2, 1.5, 2, and 2.2. The analysis was conducted using ANSYS Fluent using a viscous laminar model. The outcomes of the simulation of the base case were validated with existing studies. The drag coefficient, Cd, lift coefficient, Cl and the Strouhal number, St, as well as vorticity contours, velocity contours, and pressure contours were examined. Vortex shedding behind the shrouded cylinders was observed to be suppressed and delayed farther downstream with increasing gap ratio. The effect was significant for spacing ratio greater than 2.0. The effect of hole types: uniform and non-uniform holes, was also effective at these spacing ratios for the chosen Reynolds number of 200. Specifically, a spacing ratio of 1.2 enhanced further the vortex intensity and should be avoided.

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