Documents published in Scipedia

• Dirichlet boundary control of a steady multiscale fluid-structure interaction system

  G. Barbi, A. Chierici, V. Giovacchini, L. Manes, S. Manservisi, L. Sirotti

  eccomas2022.

  
  

  Abstract

  This work aims to extend the techniques used for the optimal control of the NavierStokes systems to control a steady multi-scale FSI system. In particular, we consider a multiscale fluid-structure interaction problem where the structure obeys a membrane model derived from the Koiter shell equations. With this approach, the thickness of the solid wall can be neglected, with a meaningful reduction of the computational cost of the numerical problem. The fluid-structure simulation is then reduced to the fluid equations on a moving mesh together with a Robin boundary condition imposed on the moving solid surface. The inverse problem is formulated to control the velocity on a boundary to obtain a desired displacement of the solid membrane. For this purpose, we use an optimization method that relies on the Lagrange multiplier formalism to obtain the first-order necessary conditions for optimality. The arising optimality system is discretized in a finite element framework and solved with an iterative steepest descent algorithm, used to reduce the computational cost of the numerical simulations.

  Abstract
  This work aims to extend the techniques used for the optimal control of the NavierStokes systems to control a steady multi-scale FSI system. In particular, we consider a multiscale [...]

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• A posteriori MOOD limiting approach for multicomponent flows on unstructured meshes

  P. Tsoutsanis, P. Farmakis

  eccomas2022.

  
  

  Abstract

  A relaxed, high-order, Multidimensional Optimal Order Detection (MOOD) framework is extended to the simulation of compressible multicomponent flows on unstructured meshes in the open-source unstructured compressible flow solver UCNS3D. The class of diffuse interface methods (DIM) is employed with a five-equation model. The high-order CWENO spatial discretisation is selected due to its low computational cost and improved non-oscillatory behaviour compared to the original WENO variants. The relaxed MOOD enhancement of the CWENO method has been necessary to further improve the robustness of the CWENO method. A series of challenging compressible multicomponent flow problems have been implemented in UCNS3D, including shock wave interaction with a water droplet and shock-induced collapse of bubbles arrays. Such problems are generally very stiff due to the strong gradients present, and it has been possible to tackle them using the extended MOOD-CWENO numerical framework.

  Abstract
  A relaxed, high-order, Multidimensional Optimal Order Detection (MOOD) framework is extended to the simulation of compressible multicomponent flows on unstructured meshes [...]

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• Non-reflecting boundary condtions on unstructured grids

  H. Kersken, C. Frey

  eccomas2022.

  
  

  Abstract

  Non-reflecting boundary condition at interfaces for flow simulations in turbomachinery using the method laid out by Giles [1] and Saxer [2] require averages or Fourier decomposition of the flow solution using stations of constant radius at the interface. On structured grids the grid generation process can easily enforce grids having element centers with this property while on unstructured grids this is rarely achievable. We describe an approach which works on an auxiliary mesh with a band structure created from the surface mesh at interfaces and study the influence of the prescribed distribution of the bands on the solution. The effectiveness of the approach is demonstrated by applying it to the simulation of a compressor stage and comparing the results with results obtained by using the existing approach for creating bands and a simulation on a structured grid.

  Abstract
  Non-reflecting boundary condition at interfaces for flow simulations in turbomachinery using the method laid out by Giles [1] and Saxer [2] require averages or Fourier decomposition [...]

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• Numerical methods for diffuse interface multifluid models

  C. Le Touze, N. Rutard

  eccomas2022.

  
  

  Abstract

  We describe some numerical methods developed in ONERA's Cedre platform to solve diffuse interface multifluid models with a view to realistic industrial applications. These methods are illustrated on test cases such as a shock-droplet interaction case.

  Abstract
  We describe some numerical methods developed in ONERA's Cedre platform to solve diffuse interface multifluid models with a view to realistic industrial applications. These [...]

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• Numerical Investigation of Oleo-Pneumatic Shock Absorber: A Multifidelity Approach

  A. Sheikh Al-Shabab, B. Grenko, D. Vitlaris, P. Tsoutsanis, A. Antoniadis, M. Skote

  eccomas2022.

  
  

  Abstract

  A representative shock absorber geometry is developed based on the general guidelines available in the literature, and it is validated against experimental measurements from a drop test. Simulations are conducted using a multi-fidelity approach ranging from unsteady scale resolving three-dimensional simulations to dynamic system models. High fidelity simulations provide a detailed insight into the flow physics inside the shock absorber, as well as help calibrate and validate lower fidelity methods, under conditions for which no experimental measurements are available to achieve that purpose. On the other hand, lower fidelity methods are used to efficiently scan the design space and test the dependency of the shock absorber performance on the various design parameters, in addition to identifying parameter combinations that would be of interest to investigate using a high-fidelity approach.

  Abstract
  A representative shock absorber geometry is developed based on the general guidelines available in the literature, and it is validated against experimental measurements from [...]

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• High-order, high-fidelity simulation of unsteady shock-wave/boundary layer interaction using flux reconstruction

  N. Goffart, B. Tartinville, K. Puri, C. Hirsch, S. Pirozzoli

  eccomas2022.

  
  

  Abstract

  In this work, a high-order implicit large-eddy simulation of an oblique shockwave/boundary layer interaction at Mach 2.3 is performed. The high-order solver is based on the flux reconstruction method, allowing an arbitrary order of accuracy. A particular attention is paid to the shock-capturing technique which consists in a combination of a Laplacian artificial viscosity with the Ducros sensor. The ability of such a solver to accurately predict the flow features is assessed on both steady and unsteady fields. In particular, the typical lowfrequency motion of the reflected shock is reproduced. The shock-capturing methodology is proven to be efficient at resolving the shocks without damping the turbulence in the boundary layer. The results obtained give confidence in this solver to study in more details the shockwave/boundary layer interaction phenomenon and future work is focused on the analysis of the oscillatory turbulent field in the interaction region.

  Abstract
  In this work, a high-order implicit large-eddy simulation of an oblique shockwave/boundary layer interaction at Mach 2.3 is performed. The high-order solver is based on the [...]

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• Implicit LES of the Transonic Flow Over A High-Pressure Turbine Cascade using DG Subcell Shock Capturing

  B. Klose, C. Morsbach, M. Bergmann, E. Kügeler

  eccomas2022.

  
  

  Abstract

  Implicit large-eddy simulations of the high-pressure turbine cascade VKI-LS89 under transonic operating conditions using a high-order accurate discontinuous Galerkin spectral element method are presented. The subcell shock capturing method by Hennemann et al. [1] is investigated and compared against simulations with artificial viscosity. Additionally, the effect of laminar and turbulent inflow conditions are validated against numerical and experimental results from literature. This analysis shows that the subcell-shock-capturing method performs well by effectively reducing spurious oscillations across the shock front and acoustic waves while leaving the rest of the solution domain unaffected.

  Abstract
  Implicit large-eddy simulations of the high-pressure turbine cascade VKI-LS89 under transonic operating conditions using a high-order accurate discontinuous Galerkin spectral [...]

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• Functional implications of renal adaptations in gestational hypertension

  M. Stadt, A. Layton

  eccomas2022.

  
  

  Abstract

  During pregnancy, major adaptations in renal morphology, hemodynamics, and transport occur to achieve the volume and electrolyte retention required in pregnancy. These complex changes can appear counterintuitive when considered in isolation. Additionally, in pregnancies complicated by a disorder, such as gestational hypertension, kidney function may be altered from normal pregnancy. To analyze how renal function is altered during pregnancy, we developed epithelial cell-based computational models of solute and water transport in a nephron of the kidney for a rat in midand late-pregnancy. The model represents known pregnancy-induced changes in renal transporters, including reduction in proximal tubule and medullary loop transporters. The pregnant rat nephron models predicted urine output and excretion consistent with measured values. Additionally, we simulated the inhibition and knockout of the ENaC and H+-K+-ATPase transporters.

  Abstract
  During pregnancy, major adaptations in renal morphology, hemodynamics, and transport occur to achieve the volume and electrolyte retention required in pregnancy. These complex [...]

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• A time-staggered CFD scheme for variable density moist air Flow

  H. Amino, C. Flageul, B. Carissimo, M. Ferrand

  eccomas2022.

  
  

  Abstract

  We present a conservative second order staggered time scheme for dry and moist variable density air flow implemented in the open source CFD solver code saturne. The staggered time arrangement introduced by Pierce and Moin [1] is extended to finite volumes and discontinuous solutions. An Helmholtz equation is solved in order include the thermodynamical pressure variation and to remove the acoustic CFL restriction. The internal energy equation supplemented by a corrective source term based on the kinetic energy dissipation [2] is solved, allowing the scheme to be consistent with discontinuous solutions. The water phase change is treated by considering thermodynamical equilibrium. Dalton’s law is used to compute the density and the temperature is obtained from the internal energy equation, solving with Newton’s method in case of phase change. A numerical analysis is presented to insure the positivity of the thermodynamic variables, followed by the scheme verification and validation. First, dry air cases are presented: a natural convection and shock cases are used to verify its accuracy related to singularities and buoyancy effects. Moreover, a pressure cooker like system shows the scheme good reproduction of pressure variations and correct time error convergences rates. Finally, the moist air module is verified against analytical cases.

  Abstract
  We present a conservative second order staggered time scheme for dry and moist variable density air flow implemented in the open source CFD solver code saturne. The staggered [...]

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• Mathematical and numerical analysis of a simplified model for boiling flows

  T. Pichard

  eccomas2022.

  
  

  Abstract

  We focus on a toy problem which corresponds to a simplification of a boiling twophase flow model. This model is a hyperbolic system of balance laws with a source term defined as a discontinuous function of the unknown. Several discretizations of this source terms are studied, and we illustrate their capacity to capture steady states.

  Abstract
  We focus on a toy problem which corresponds to a simplification of a boiling twophase flow model. This model is a hyperbolic system of balance laws with a source term defined [...]

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