Fluid Structure Interaction

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Seminar on “ Fluid Structure Interaction ” Student Name : S Kalyan Yadav Subject Code : 10MAE16 Guided by: Name: Dr. S K Maharana . Designation: Head of the department. Department of Aeronautical Engineering

Content: 

Content Definition. Literature Review. Need of FSI-Study. Problem formulation & Methodology. Fluid-structure-mesh Coupling. General classification. FSI-coupling schemes. FSI-Time stepping methods. Computational Data Transfer. Instrumentation. Activities carried out and ongoing . Conclusion.

Fluid structure interaction : 

Fluid structure interaction Fluid-structure interaction (FSI) is the interaction of some movable or deformable structure with an internal or surrounding fluid flow. FSI is a true Multiphysics phenomenon where a fluid flowing around or within a structure causes it to move, spin or even change shape due to flow-induced pressure and shear loads – ANSYS Inc Fluid-structure interaction (FSI) scenarios are those that involve the coupling of fluid mechanics and structural mechanics – FLUENT Inc Propagation of a pressure wave through an incompressible fluid in a flexible tube

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Continued……

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Fluid-structure interactions can be stable or oscillatory. In oscillatory interactions, the strain induced in the solid structure causes it to move such that the source of strain is reduced, and the structure returns to its former state only for the process to repeat Continued……

Literature Review : 

Literature Review Fluid-structure interactions are a crucial consideration in the design of many engineering systems, e.g. aircraft and bridges. Failing to consider the effects of oscillatory interactions can be catastrophic, especially in structures comprising materials susceptible to fatigue . Tacoma Narrows Bridge (1940), is probably one of the most infamous examples of large-scale failure. Aircraft wings and turbine blades can break due to FSI oscillations.

Examples: 

Examples Fluid-structure interaction has to be taken into account for the analysis of aneurysms in large arteries and artificial heart valves. A reed actually produces sound because the system of equations governing its dynamics has oscillatory solutions. The dynamic of reed valves used in two strokes engines and compressors is governed by FSI. The act of blowing a raspberry is another such example Alto and tenor saxophone reeds

Need of Study: 

Need of Study FSI results in the cause of Flutter. Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, buildings, telegraph wires, stop signs, and bridges. Flutter occurs as a result of interactions between aerodynamics, stiffness, and inertial forces on a structure. In an aircraft, as the speed of the wind increases, there may be a point at which the structural damping is insufficient to damp out the motions which are increasing due to aerodynamic energy being added to the structure. This vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft

Problem formulation & Methodology: 

Problem formulation & Methodology Fluid-structure interaction problems and Multiphysics problems in general are often too complex to solve analytically so they have to be analyzed by means of experiments or numerical simulation. Research in the fields of computational fluid dynamics and computational structural dynamics is still ongoing but the maturity of these fields enables numerical simulation of fluid-structure interaction.

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Two main approaches exist for the simulation of fluid-structure interaction problems: Monolithic approach: the equations governing the flow and the displacement of the structure are solved simultaneously, with a single solver Partitioned approach: the equations governing the flow and the displacement of the structure are solved separately, with two distinct solvers Continued……

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Continued….. The monolithic approach requires a code developed for this particular combination of physical problems whereas the partitioned approach preserves software modularity because an existing flow solver and structural solver are coupled. Moreover, the partitioned approach facilitates solution of the flow equations and the structural equations with different, possibly more efficient techniques which have been developed specifically for either flow equations or structural equations. On the other hand, development of stable and accurate coupling algorithm is required in partitioned simulation.

FLUID-STRUCTURE-MESH COUPLING : 

FLUID-STRUCTURE-MESH COUPLING CFD – Computational Fluid Dynamics CSD – Computational Structural Dynamics CMD – Computational Mesh Dynamics

General classification: 

General classification Transient FSI : The structure’s reaction forces continuously vary with time Steady-state FSI : The loads induced by the fluid are exactly balanced by the structure’s reaction forces and the structure reaches a displaced equilibrium position

FSI-coupling schemes: 

FSI-coupling schemes Strong : Fluid and structure are modeled as a continuum with a single system of partial differential equations Loose : Separate solvers for both fluid and structure

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Grid Generator Fluid solver Structure t=t+∆t t ≤ t fsi T≤t+i BEGIN END Initial Data Sub-iteration loop NO YES YES NO Fluid, Structure solvers restart FSI iteration loop Pressure transfer Displacement & Velocity of Center and FSI interface Reads velocities from structure solver in each sub-iteration Reads displacements LOOSE-FSI ALGORITHM Blue region – Key to implicit method

Need for loose coupling: 

Need for loose coupling Nonlinear structural solver and a nonlinear fluid solver are minimum requirements for the problem under consideration It would be computationally inefficient to develop a new Aero elastic / FSI tool to study this problem Best alternative would be to exploit the utility of well proven CFD and CSD codes and combine them ANSYS+CFX & ABAQUS+FIDAP

FSI-Time stepping methods: 

FSI-Time stepping methods Implicit – Coupling with sub-iterations Explicit – Coupling without sub-iterations

Computational Data Transfer: 

Computational Data Transfer Structural Code Fluids Grid Deformation Structures and Fluids Interface Fluid Solver Pressures Deflections Structural Grid deflections New Fluid Grid

Instrumentation : 

Instrumentation 2 arrays of 40 microphones each 3-D Digital Particle Image Velocimetry (PIV) Single point Laser Doppler Vibrometer (LDV) Scanning LDV (SLDV)

Activities carried out and ongoing: 

Activities carried out and ongoing Turbulent Boundary Layer Interactions with elastic end wall Hydrodynamic pressures force vibrations in end wall. Scanning LDV used to record vibration pattern of endwall

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Add Airfoil Tip to turbulent boundary layer. Complicated system of coupled hydrodynamic and acoustic pressures. Use unsteady force transducers with scanning and single point LDV to correlate unsteady force with vibration pattern of endwall. Continued……

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Sound Radiation From A Submersed Elastic Duct in Non-uniform Flow Continued……

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Fluid-Structure Interaction with Cracking . two-way coupled fluid-structure interaction (FSI) simulation with cracking (water plate). FSI - Fluid Structure Interaction with Sundance Toolbox. (with Nitsche's method). Continued……

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Fluid-Structure Interaction Simulation flapping wings Continued……

Conclusion: 

Conclusion Fluid-Structure Interaction (FSI) is the science of coupling the results of a Computational Fluid Dynamics (CFD) analysis and a Structural Mechanics analysis where their results affect each other. FSI is an advanced tool that bridges the gap between Computational Fluid Dynamics (CFD) and Structural Mechanics.

References: 

References Fluid structure interactions- Vol1 Vol2 - by Michael P. Paidoussis Fluid-structure interactions- by Klaus'Jiirgen Bathe Computational fluid dynamics- by John F.Wendt John ,D. Anderson Jr., Joris Degroote, G´erard Degrez, Erik Dick, Roger Grundmann and Jan Vierendeels. Wikipedia.org rstb.royalsocietypublishing.org adsabs.harvard.edu vimeo.com www5.in.tum.de www.iitr.ac.in www.springer.com www.witpress.com www.flow3d.com www.nd.edu www.pa.uky.edu scholar.google.co.in www.bloodhoundssc.com www.cs.wright.edu www.youtube.com www.howstuffworks.com www.numac.com.my

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