Calculation of Sound Fields in Flowing Media Using CAPA and Diffpack

Transcription

1 Calculation of Sound Fields in Flowing Media Using CAPA and Diffpack H. Landes 1, M. Kaltenbacher 2, W. Rathmann 3, F. Vogel 3 1 WisSoft, 2 Univ. Erlangen 3 inutech GmbH

2 Outline Introduction Sound in Flowing Media The Tools - CAPA and Diffpack Coupling Diffpack and CAPA Application: Flowmeter Conclusion and Outlook

3 Sound in Flowing Media Wave Equation (Pierce) generalized velocity potential ψ Convective derivative operator Flow not influenced by sound FEM Formulation Unsymmetric matrices Damping matrix required even in undamped case Infinite elements and fluid-structure interaction

4 Outline Introduction Sound in Flowing Media The Tools: CAPA and Diffpack Coupling Diffpack and CAPA Application: Flowmeter Conclusion and Outlook

5 CAPA: a short overview Pre-Processing Interfaces to Standard FEM/BEM Software Piezoelectrics Ferroelectric Material Electrostatics Nonlinear Force Acoustics Mechanics Magnetics Nonlinear Material Large Deflections and Large Strains Nonlinear Wave Propagation Post-Processing

6 CAPA: a short overview (cont.) FEM, BEM, and hybrid schemes Time domain, frequency domain, and eigenvalue calculations Problems in bounded and unbounded regions Implicit, explicit, and mixed solutions Iterative and direct solvers Multigrid

7 Diffpack - Philosophy Structural mechanics Porous media flow Water waves FEM FDM I/O Grid Field Aerodynamics Stochastic PDEs Observation: Methodology basis independent of applications Heat transfer Vector Matrix Ax=b Other PDE applications Incompressible flow

8 Diffpack - Tailored FEM Component software to develop solvers for nonstandard or specialized simulation problems C++ libraries with over 600 classes for FEM, FDM, FVM (e.g. grids, solution data) store and solve linear systems nonlinear solver Complementary to programs like ANSYS or NASTRAN Requires an expert user who understands the physics, mathematics and C++ programming Benefits are: Applicable to most simulation problems Exact modelling of physical effects Control of numerical solution algorithm Highest quality simulation results

9 Outline Introduction Sound in Flowing Media The Tools: CAPA and Diffpack Coupling Diffpack and CAPA Application: Flowmeter Conclusion and Outlook

10 Coupling CAPA and Diffpack General approach: use CAPA for acoustics and Diffpack for the flow simulation Feasibility study: use simple flow solver NSPenalty1 based on Meshing with ANSYS, use cdb-file and ANSYS-CAPA interface Datafilter toolbox to convert mesh from cdb file to Diffpack grid boundary conditions from ANSYS to Diffpack Validation runs ρ (v + v v) = - ( λ v) p = λ v

11 Coupling CAPA and Diffpack (cont.)

12 Verification Test Case Cylindrical Tube, laminar flow (Poiseuille flow) Comparison with internal CAPA 1D flow option Length 300 mm, medium water, excitation 200 khz burst Maximum relative difference below 0.08 %

13 Outline Introduction Sound in Flowing Media The Tools: CAPA and Diffpack Coupling Diffpack and CAPA Application: Flowmeter Conclusion and Outlook

14 Application: Flowmeter Setup Air filled tube Flow direction Transducers Diameter 30 mm Operating frequency 200 khz length of measurement tube 36 cm approx. 500 million elements for 3D model!

15 Application: Flowmeter (cont.) FE Model 2D approach (section modeling) Approx elements (mesh density 400 times higher than shown above) time steps Calculation time approx. 10 h

16 Application: Flowmeter (cont.) Stationary flow: inflow velocity 0.3 m/s velocity streamlines pressure distribution

17 Application: Flowmeter (cont.) Comparison of sound fields receiver flowing media media at rest

18 Application: Flowmeter (cont.) Signal at receivers

19 Application: Flowmeter (cont.) Sound propagation within flow

20 Conclusion Feasibility study: coupling of CAPA and Diffpack for sound in flowing media Only minimal changes in CAPA required Different grid sizes used in solution (acoustic mesh significantly finer) Interpolation provided by Diffpack internals Future work Implementation of an advanced flow solver in Diffpack Treat problems involving non-stationary flows