A multiscale method for wave propagation in 3D heterogeneous poroelastic media

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. T237-T257
Author(s):  
Wensheng Zhang ◽  
Hui Zheng
Keyword(s):  
Wave Propagation ◽  
Computational Cost ◽  
Mesh Size ◽  
Multiscale Method ◽  
Small Scale ◽  
Physical Parameters ◽  
Local Problem ◽  
Wave Simulation ◽  
Poroelastic Media ◽  
Coarse Grids

A new multiscale method for wave simulation in 3D heterogeneous poroelastic media is developed. Wave propagation in inhomogeneous media involves many different scales of media. The physical parameters in the real media usually vary greatly within a very small scale. For the direct numerical methods for wave simulation, a refined grid is required in mesh generation to maintain the match between the mesh size and the material variations in the spatial scale. This greatly increases the computational cost and computer memory requirements. The multiscale method can overcome this difficulty due to the scale difference. The basic idea of our multiscale method is to construct computational schemes on two sets of meshes, i.e., coarse grids and fine grids. The finite-volume method is applied on the coarse grids, whereas the multiscale basis functions are computed with the finite-element method by solving a local problem on the fine grids. Moreover, the local problem only needs to be solved once before time stepping. This allows us to use a coarse grid while still capturing the information of the physical property variations in the small scale. Therefore, it has better accuracy than the single-scale method when they use the same coarse grids. The theoretical method and the dispersion analysis are investigated. Numerical computations with the perfectly matched layer boundary conditions are completed for 3D inhomogeneous poroelastic models with randomly distributed small scatterers. The results indicate that our multiscale method can effectively simulate wave propagation in 3D heterogeneous poroelastic media with a significant reduction in computation cost.

A One-Way Coupled Euler and Parabolic Model for Outdoor Blast Wave Simulation in Real Environment

2018 ◽  
Vol 26 (04) ◽  
pp. 1850019
Author(s):  
M. Nguyen-Dinh ◽  
O. Gainville ◽  
N. Lardjane
Keyword(s):  
Wave Propagation ◽  
Blast Wave ◽  
High Performance ◽  
Near Field ◽  
Computational Cost ◽  
Physical Parameters ◽  
Atmospheric Conditions ◽  
Simulation Code ◽  
Coupling Procedure ◽  
Blast Wave Propagation

Aerial blast wave propagation is affected by numerous physical parameters such as the source energy, the topography, the ground nature, or the atmospheric conditions. Direct high performance computing simulations is a valuable tool, but remains extremely costly in complex environment which limits the number of simulations. It is best used locally or to build reference solutions useful for the evaluation of simplified fast running models. Indeed, as the blast wave propagates, its strength weakens and after some distance, linear acoustic theory may be valuable. Here, we present the results of a one-way coupling procedure between a nonlinear Euler direct simulation code for the near field, including the detonation phase, and a parabolic linear acoustic model for the far field. Both models take into account for topography and atmospheric conditions. We show that, compared to the full Euler simulations, the coupling procedure provides accurate results at a reduced computational cost for blast wave propagation in the vicinity of an actual pyrotechnic site. The quality of the signals is also improved in comparison with classical parabolic simulations started with an analytical solution.

scholarly journals How to adapt numerical simulation of wave propagation and ultrasonic laboratory experiments to be comparable — A case study for a complex topographic model

Geophysics ◽  
2018 ◽  
Vol 83 (4) ◽  
pp. T195-T207 ◽  
Author(s):  
Bence Solymosi ◽  
Nathalie Favretto-Cristini ◽  
Vadim Monteiller ◽  
Dimitri Komatitsch ◽  
Paul Cristini ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Computational Cost ◽  
Seismic Exploration ◽  
Quality Data ◽  
Small Scale ◽  
Water Tank ◽  
Zero Offset

Numerical methods are widely used in seismic exploration to simulate wave propagation; however, the algorithms are based on various assumptions. The accuracy of numerical simulations is of particular interest in the case of realistic geologic setups. The direct comparison of numerical results can have limitations, and an alternative approach can be the comparison of synthetic results with experimental data, obtained for a small-scale physical model in laboratory conditions. Laboratory experiments are repeatable and provide high-quality data for a known configuration. We have developed a possible workflow to adapt the numerical simulations and the laboratory experiments to each other, such that the two can be easily compared with high accuracy. The model is immersed in a water tank, and a conventional pulse-echo technique is used to collect the reflection data in zero-offset and offset configurations. We use a spectral-element method for the numerical modeling. The model geometry is implemented using a nonstructured mesh, and the computational cost can be optimized using larger elements and higher-order basis functions. The real source transducer characteristics are implemented based on a new approach: laboratory characterization of the impulse response, followed by an inversion step to obtain a numerically equivalent source. The comparison of the zero-offset synthetic and laboratory results reveals an excellent fit in terms of arrival time, phase, and amplitude. Minor amplitude mismatches may be attributed to the noise recorded in the laboratory data and to the possible inaccuracy of the proposed source implementation. Comparison of the simulated and laboratory offset traces also exhibits a good fit in general, but with significantly less accuracy for some arrivals than in the zero-offset case. This can be mainly attributed to the inaccuracies of the transducer positions during the laboratory measurements combined with the strong topography of the model.

3-D Navier-Stokes Simulation of Large-Scale Regions of the Bronchopulmonary Tree

2009 ◽  
Author(s):  
D. Keith Walters ◽  
William H. Luke
Keyword(s):  
Large Scale ◽  
Cfd Simulation ◽  
Computational Cost ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Mesh Size ◽  
Flow Path ◽  
Navier Stokes ◽  
Small Scale ◽  
Flow Geometry

A new methodology for CFD simulation of airflow in the human bronchopulmonary tree is presented. The new approach provides a means for detailed resolution of the flow features via three-dimensional Navier-Stokes CFD simulation without the need for direct simulation of the entire flow geometry, which is well beyond the reach of available computing power now and in the foreseeable future. The method is based on a finite number of flow paths, each of which is fully resolved, to provide a detailed description of the entire complex small-scale flowfield. A stochastic coupling approach is used for the unresolved flow path boundary conditions, yielding a virtual flow geometry allowing accurate statistical resolution of the flow at all scales for any set of flow conditions. Results are presented for multi-generational lung models based on the Weibel morphology and the anatomical data of Hammersley and Olson. Validation simulations are performed for a portion of the bronchiole region (generations 4–12) using the flow path ensemble method, and compared to simulations that are geometrically fully resolved. Results are obtained for three inspiratory flowrates and compared in terms of pressure drop, flow distribution characteristics, and flow structure. Results show excellent agreement with the fully resolved geometry, while reducing the mesh size and computational cost by as much as 94%.

A Method for Three-Dimensional Navier–Stokes Simulations of Large-Scale Regions of the Human Lung Airway

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
D. Keith Walters ◽  
William H. Luke
Keyword(s):  
Large Scale ◽  
Cfd Simulation ◽  
Computational Cost ◽  
Three Dimensional ◽  
Mesh Size ◽  
Flow Path ◽  
Physical Models ◽  
Navier Stokes ◽  
Small Scale ◽  
Flow Geometry

A new methodology for CFD simulation of airflow in the human bronchopulmonary tree is presented. The new approach provides a means for detailed resolution of the flow features via three-dimensional Navier–Stokes CFD simulation without the need for full resolution of the entire flow geometry, which is well beyond the reach of available computing power now and in the foreseeable future. The method is based on a finite number of flow paths, each of which is fully resolved, to provide a detailed description of the entire complex small-scale flowfield. A stochastic coupling approach is used for the unresolved flow path boundary conditions, yielding a virtual flow geometry that allows accurate statistical resolution of the flow at all scales for any set of flow conditions. Results are presented for multigenerational lung models based on the Weibel morphology and the anatomical data of Hammersley and Olson (1992, “Physical Models of the Smaller Pulmonary Airways,” J. Appl. Physiol., 72(6), pp. 2402–2414). Validation simulations are performed for a portion of the bronchiole region (generations 4–12) using the flow path ensemble method, and compared with simulations that are geometrically fully resolved. Results are obtained for three inspiratory flowrates and compared in terms of pressure drop, flow distribution characteristics, and flow structure. Results show excellent agreement with the fully resolved geometry, while reducing the mesh size and computational cost by up to an order of magnitude.

From acoustic to elastic inverse extended Born modeling: a first insight in the marine environment

Geophysics ◽  
2021 ◽  
pp. 1-73
Author(s):  
Milad Farshad ◽  
Hervé Chauris
Keyword(s):  
Least Squares ◽  
Marine Environment ◽  
Computational Cost ◽  
Physical Parameters ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
S Wave ◽  
Time Migration ◽  
Physical Density ◽  
Acoustic Approximation

Elastic least-squares reverse time migration is the state-of-the-art linear imaging technique to retrieve high-resolution quantitative subsurface images. A successful application requires many migration/modeling cycles. To accelerate the convergence rate, various pseudoinverse Born operators have been proposed, providing quantitative results within a single iteration, while having roughly the same computational cost as reverse time migration. However, these are based on the acoustic approximation, leading to possible inaccurate amplitude predictions as well as the ignorance of S-wave effects. To solve this problem, we extend the pseudoinverse Born operator from acoustic to elastic media to account for the elastic amplitudes of PP reflections and provide an estimate of physical density, P- and S-wave impedance models. We restrict the extension to marine environment, with the recording of pressure waves at the receiver positions. Firstly, we replace the acoustic Green's functions by their elastic version, without modifying the structure of the original pseudoinverse Born operator. We then apply a Radon transform to the results of the first step to calculate the angle-dependent response. Finally, we simultaneously invert for the physical parameters using a weighted least-squares method. Through numerical experiments, we first illustrate the consequences of acoustic approximation on elastic data, leading to inaccurate parameter inversion as well as to artificial reflector inclusion. Then we demonstrate that our method can simultaneously invert for elastic parameters in the presence of complex uncorrelated structures, inaccurate background models, and Gaussian noisy data.

Differences in the Upscaling Procedure for Compositional Reservoir Simulations of Immiscible and Miscible Gas Flooding

2021 ◽  
Author(s):  
Victor de Souza Rios ◽  
Arne Skauge ◽  
Ken Sorbie ◽  
Gang Wang ◽  
Denis José Schiozer ◽  
...  
Keyword(s):  
Computational Cost ◽  
Specific Treatment ◽  
Dynamic Responses ◽  
Scale Model ◽  
Small Scale ◽  
Coarse Scale ◽  
Reservoir Models ◽  
Permeability Upscaling ◽  
Gas Flooding ◽  
Grid Block

Abstract Compositional reservoir simulation is essential to represent the complex interactions associated with gas flooding processes. Generally, an improved description of such small-scale phenomena requires the use of very detailed reservoir models, which impact the computational cost. We provide a practical and general upscaling procedure to guide a robust selection of the upscaling approaches considering the nature and limitations of each reservoir model, exploring the differences between the upscaling of immiscible and miscible gas injection problems. We highlight the different challenges to achieve improved upscaled models for immiscible and miscible gas displacement conditions with a stepwise workflow. We first identify the need for a special permeability upscaling technique to improve the representation of the main reservoir heterogeneities and sub-grid features, smoothed during the upscaling process. Then, we verify if the use of pseudo-functions is necessary to correct the multiphase flow dynamic behavior. At this stage, different pseudoization approaches are recommended according to the miscibility conditions of the problem. This study evaluates highly heterogeneous reservoir models submitted to immiscible and miscible gas flooding. The fine models represent a small part of a reservoir with a highly refined set of grid-block cells, with 5 × 5 cm2 area. The upscaled coarse models present grid-block cells of 8 × 10 m2 area, which is compatible with a refined geological model in reservoir engineering studies. This process results in a challenging upscaling ratio of 32 000. We show a consistent procedure to achieve reliable results with the coarse-scale model under the different miscibility conditions. For immiscible displacement situations, accurate results can be obtained with the coarse models after a proper permeability upscaling procedure and the use of pseudo-relative permeability curves to improve the dynamic responses. Miscible displacements, however, requires a specific treatment of the fluid modeling process to overcome the limitations arising from the thermodynamic equilibrium assumption. For all the situations, the workflow can lead to a robust choice of techniques to satisfactorily improve the coarse-scale simulation results. Our approach works on two fronts. (1) We apply a dual-porosity/dual-permeability upscaling process, developed by Rios et al. (2020a), to enable the representation of sub-grid heterogeneities in the coarse-scale model, providing consistent improvements on the upscaling results. (2) We generate specific pseudo-functions according to the miscibility conditions of the gas flooding process. We developed a stepwise procedure to deal with the upscaling problems consistently and to enable a better understanding of the coarsening process.

scholarly journals A Cost-Effective Method for Bulge Prediction in Two Point Incremental Forming

2021 ◽  
Author(s):  
Jaekwang Shin ◽  
Ankush Bansal ◽  
Randy Cheng ◽  
Alan Taub ◽  
Mihaela Banu
Keyword(s):  
Shape Function ◽  
Incremental Forming ◽  
Computational Cost ◽  
Region Of Interest ◽  
Computation Time ◽  
Mesh Size ◽  
Cost Effective ◽  
Summation Method ◽  
Fem Modeling ◽  
Forming Defects

Accurate prediction of the defects occurring in incrementally formed parts has been gaining attention in recent years. This interest is because accurate predictions can overcome the limitation in the advancement of incremental forming in industrial-scale implementation, which has been held back by the increase in the cost and development time due to trial and error methods. The finite element method has been widely utilized to predict the defects in the formed part, e.g., bulge. However, the computation time of running these models and their mesh-size dependency in predicting the forming defects represent barriers in adopting these models as part of CAD-FEM-CAE platforms. Thus, robust analytical and data-driven algorithms must be developed for a cost-effective design of complex parts. In this paper, a new analytical model is proposed to predict the bulge location and geometry in two point incremental forming of an aerospace aluminum alloy AA7075-O for a 67° truncated cone. First, the algorithm calculates the region of interest based on the part geometry. A novel shape function and weighted summation method are then utilized to calculate the amplitude of the instability produced by material accumulation during forming, leading to a bulge on the unformed portion of the sample. It was found that the geometric profile of the part influences the shape function, which is a function created to incorporate the effects of process parameter and boundary condition. The calculated profile in each direction is finalized into one 3-dimensional profile, compared with the experimental results for validation. The proposed model has proven to predict an accurate bulge profile with 95% accuracy comparing with experiments with less than 5% computational cost of FEM modeling.

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