ANSYS/Multiphysics FSI with Applications

Transcription

1 ANSYS/Multiphysics FSI with Applications Mark Troscinski Multiphysics Product Manager Presented By: David Ellis Idac Ltd FE-Net Industry Co-ordinator for Consumer Goods 1

2 Agenda/Objectives Answer some questions: What is Multiphysics? What is FSI? Describe benefits of new ANSYS FSI capability Illustrate some interesting FSI applications What is Multiphysics? Multiphysics - The ability to combine the effects of two or more different, yet interrelated physical phenomena, within one, unified simulation environment. 2

3 Multiphysics Coupling Heat Transfer Electricity Solid Mechanics Fluid Mechanics Magnetism Multiphysics Coupling Heat Transfer Solid Mechanics Thermal-Structural Coupling Engines, Gas Turbines, Heat Exchangers Electronic Components, Solder Joints Cryogenic components and systems Needed for any product subjected to extreme changes in temperature. 3

4 Multiphysics Coupling Heat Transfer Electricity Thermal-Electric Coupling Current-carrying conductors, bus bars Electric motors, generators, transformers Electronic components and systems Needed for electric power handling components and systems. Multiphysics Coupling Electricity Magnetism Low-Frequency Electromagnetics Motors, generators, induction coils High-Frequency Electromagnetics Waveguides, patch antennas, radar systems, microwave systems 4

5 Multiphysics Coupling Heat Transfer Thermal-Electromagnetic Coupling Induction heating systems Microwave heating systems Used in many manufacturing processes: Heat treating Pre-heating for metal forming operations Multiphysics Coupling Fluid Mechanics Electro- magnetics Electro- magnetics Fluid-Electromagnetic Coupling Induction furnaces for stirring molten metals Used by induction furnace manufacturers Environment too harsh to easily observe stirring patterns 5

6 Multiphysics Coupling Electricity Solid Mechanics Electrostatic-Structural Coupling Comb drives, torsional resonators Other MEMS devices Piezoelectrics Transducers, microphones, micropumps Inkjet printer actuation systems Multiphysics Coupling Electro- magnetics Solid Mechanics Magneto-Structural Coupling Solenoid devices, stepper motors Alternators, generators Used by engineers to determine: Magnetic force (linear systems) Magnetic torque (rotary systems) Efficiency 6

7 Multiphysics Coupling Fluid Mechanics Solid Mechanics Inviscid Fluid-Structural Coupling Acoustics-based applications Transportation NVH, undersea noise detection Viscous Fluid-Structural Coupling CFD-based applications Fuel injectors, control valves, fans, and pumps More, more, and still more! What is CFD? Numerical analysis of fluid flow, heat transfer, and related phenomena Within each finite element, the Navier-Stokes equations are rewritten as algebraic equations that relate nodal: Velocity Pressure Temperature Species concentrations to the values in the neighboring elements. Equations are assembled in matrices and solved to yield complete picture of flow down to resolution of mesh 7

8 Conservation of Mass CFD Equations Continuity Conservation of Momentum Newton s 2nd Law Conservation of Energy 1st Law of Thermodynamics Conservation of Species Concentration CFD Elements 2D: Fluid141 Quadrilaterals Triangles 3D: Fluid142 Hexahedrals or bricks Tetrahedrals or tets Pyramids Prisms 8

9 Eulerian CFD Flow Descriptions Focus on fixed volume of space, where fluid enters and leaves Lagrangian Focus on particular fluid region which moves relative to a fixed point of reference Arbitrary-Lagrangian-Eulerian (ALE) Boundary of fluid region moves at arbitrary velocity (something other than fluid velocity) FSI s dynamic mesh motion scheme What is FSI? In reality, it s Fluid-Solid Interaction! Fluid Mechanics Heat Transfer Solid Mechanics Coupled- Field 9

10 How is FSI done? Numerical coupling is established between the different physics modules Multiphysics Math The finite element formulation which treats a single phenomenon uses matrix algebra represented by: [ K ] { X } = { F } where [ K ] is the coefficient matrix { X } is the vector of nodal unknowns { F } is the known load vector 10

11 Matrix Coupling [[K 11 ] [K 12 ]]{[X 1 ]} {[F 1 ]} = [K 21 ] [K 22 ] [X 2 ] [F 2 ] Subscript 1 represents fluid; Subscript 2 is solid Coupled effects are accounted for by offdiagonal coefficient terms K 12 and K 21 Provides for coupled response in solution after one iteration. Positives: Matrix-Coupled FSI Solution of a coupled equation system achieved in a single step Negatives: Requires complete re-writing of the fluid and solid solvers (must develop new FSI elements) Matrix system tends to be very ill-conditioned due to difference in stiffness of fluid and the solid regions Large problems become computationally expensive 11

12 Load Vector Coupling [[K 11 ] [ 0 ] ]{[X 1 ]} {[F 1 ]} = [ 0 ] [K 22 ] [X 2 ] [F 2 ] Subscript 1 represents fluid; Subscript 2 is solid Coupled effects are accounted for by load terms F 1 and F 2 At least two iterations, one for each physics, in sequence, are needed to achieve a coupled response. Load Vector-Coupled FSI Fluid and solid variables are updated sequentially with independent fluid and solid solver algorithms At each FSI time step, appropriate loads are exchanged at the fluid-solid interface Positives: Not required to re-write fluid and solid solvers Able to leverage main features of each solver More economical for large scale problems 12

13 ANSYS FSI Initiative Tightly integrate FLOTRAN CFD & ANSYS solid solvers into a load vector-coupled FSI algorithm that is: Fully-automated Time-accurate Easy to use Leverage ANSYS/Mechanical core capabilities FSI Algorithm Benefits Fully-automated, time-accurate FSI solution algorithm for: Fluid-structure interaction Fluid-thermal interaction Fluid-thermal-electric interaction Fluid-piezoelectric interaction Why? For simulations closest to reality! 13

14 FSI Algorithm Benefits Full support for all structural nonlinearities: Geometric, material, and contact Dissimilar mesh interface: Automatically transfers loads between differently meshed fluid and solid regions Support for beam, shell, and solid elements: With or without mid-side nodes FSI Algorithm Benefits Fully-implicit time-stepping scheme: Automatically checks convergence of all relevant physics at each time step before advancing in time Allows for independent time step sizes for fluid and solid physics (sub-cycling) Provides for the most efficient, timeaccurate solutions 14

15 FSI Algorithm Benefits FLOTRAN Element Birth and Death: Suitable for FSI problems involving contact between immersed, moving structures Fluid elements may be automatically deactivated as surfaces come into contact (e.g., valve closes), or reactivated as they separate (e.g., valve opens) FSI Algorithm Layout Global Time Loop Stagger Loop ALE Mesh Morph Fluid Solution Load Transfer Solid Solution Load Transfer Convergence Check End Stagger Loop Increment Time ANSYS FLUID FLOTRAN 2D/3D Elements Extensive CFD Capabilities ALE Formulation Elasticity-Based Mesh Morphing ANSYS SOLID Structural/Thermal/Coupled-Field Geometric Non-Linearity Material Non-Linearity Contact Non-Linearity All Iterative and Direct Solvers All Transient Solver Options End Global Time Loop 15

16 Load Transfer From FLUID side Conservative Interpolation Nodal forces: FX, FY, FZ Nodal heat rates: Q From SOLID side Nodal displacements: UX, UY, UZ Nodal temperatures: TEMP Nodal velocities: VX, VY, VZ Non-Conservative Interpolation Nodal force fluxes: FX, FY, FZ Nodal heat fluxes: Q Interpolation between dissimilar meshes GST for FSI 16

17 Applications Truly applicable across all market segments: Automotive fuel injectors, control valves, engine dampers, fans & pumps Aerospace airframe and propulsion system components Flexible flow control devices, biomedical vessels and valves for blood flow Flow-induced vibration of piping systems and heat exchangers Diaper manufacturing processes, paper copy machines More, more, and still more! Deformable Flow Control Device Under low DP Under high DP 17

18 So What? Vernay Labs currently designs these devices by seat of pants method: Guess at shape to get right flow control characteristics Build and test, build and test, They have no automated process in place for designing these FSI-type devices. ANSYS/Multiphysics can significantly reduce their overall time to market. Fluid: Problem Description Incompressible, turbulent water flow Prescribed inlet-to-outlet P = 45 PSI Solid: Hyperelastic, high strain (>100%) materials Treated with Mooney-Rivlin model Simulation objective: Determine steady-state shape of solid and accompanying steady-state fluid flow rate 18

19 Axisymmetric Model CONTA172 s TARGE169 s Rubber - PLANE183 s Water - FLUID141 s Finite Element Mesh 19

20 FSI BC on Fluid FSI BC on Solid 20

21 FSI Results Problem Statement: Given plunger cavity pressure as f(time), what is the total mass flow to the leakage collection groove? mm Diesel Fuel Injection Actuation force Steels E = GPa ν = 0.29 Leakage collection groove Drain pressure => 100 kpa mm seal length Radial clearance = 2.15 microns 41 mm barrel diameter 8.5 mm plunger diameter 9.87 mm P(t) input (next page) Plunger Cavity 21

22 So What? Fuel injector leakage: Unavoidable parasitic loss Adversely affects system efficiency - Must be minimized! Current predictions grossly underestimate measured leakage volumes Caterpillar has NO automated method of predicting leakage rates. Tiny gains in system efficiency would provide tremendous advantage over their competitors Plunger Cavity Pressure 2.5E+08 Relative Static Pressure (Pa) 2.0E E E E+07 Fluid Properties: Fuel type: CAT1E262 Temperature: 85C Kinematic Viscosity: E-06 m^2/sec Density: Kpa Bulk Modulus: kpa Bulk modulus Slope: (i.e. bulk modulus = *P 0.0E Time (sec) 22

23 Model Geometry Plunger Cavity Barrel Model Geometry 10º Chamfer Leakage Inlet 23

24 Model Geometry Finite Element Mesh 24

25 Boundary Conditions UY=0 P=0 UY=0 UX=0 VX=0 VY=0 FSI(1) FSI(2) P(t) UY=0 FSI Results 500X Displacements 25

26 Leakage Flow Rates FSI CFD 6.00 Mass Flow Rate (gm/sec) Time (sec) LEAKAGE FSI / LEAKAGE CFD = 12.0! Pressure-Limiting Valve Spring constant: k spring = 8.0E+05 gm/sec^2 Spring preload: F preload = 2.5E+06 gm*mm/sec^2 Ball density: Ø 4.5 mm ρ ball = 7.8E-03 gm/mm^3 Fluid density: ρ fluid = 7.5E-04 gm/mm^3 Fluid viscosity: µ fluid = 4.0E-04 gm/(mm*sec) Relative inlet pressure: P inlet = 6.0E+05 Pa Ø 4.0 mm Ø 2.4 mm Ø 10.0 mm 55º 0.25 mm 26

27 So What? Pressure-limiting valves are used in antilock brake systems Huge liability ramifications Per VDO, tiny geometric design changes cause wide variations in valve response and performance Currently guessing on new valve designs Automated FSI tool will significantly reduce overall time to market and improve reliability Axisymmetric Model COMBIN14 SOLID42 s FLUID141 s 27

28 Finite Element Mesh Mesh Detail 28

29 Mesh Detail FSI Results 29

30 Ball Displacement History f» 875 Hz Office Copier FSI Paper Sheet: Thickness: in Length: 8.0 in Width: 11.0 in Curl Radius: 20.0 in Weight: # / in 2 Elastic Modulus: 500,000 PSI Vacuum hole: Width: 1/8 in 2 in 8 in Plenum Outlet: P: 3.0 in H 2 O 30

31 FSI Results Ink Jet Printer 31

32 Piezoelectric Micropump 500 V PZT Layer Silicon Membrane ~ 3 mm Air FSI Results 32

33 Pulsing Blood Flow Fluid element: 142 s Solid element: 45 s Dissimilar mesh interface Material Properties Solid density: 1150 kg/m^3 Young s modulus: 3.0*10^5 Pa Poisson ratio: 0.3 Fluid density: 1050 kg/m^3 Fluid viscosity: 4.0*10^-3 Inlet pressure pulse FSI Results 33

34 Vortex Shedding Re = 100 Vortex Shedding With Tail 34

35 VX = 20 mph; VY = 5 mph Summary ANSYS FSI solution capability: Easy to use, fully automated, time-accurate Full support for all structural nonlinearities Dissimilar mesh interface for beam, shell and solid elements, with or without mid-side nodes Future developments: Add automatic re-meshing capability Add n th physics to stagger loop Enhance FSI post-processing Add AMG parallel solver 35

36 Thank You! Any Questions? 36