Documents published in Scipedia

• 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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• Application of interface capturing schemes on multiphase/multicomponent compressible flow of underwater explosion

  E. Adebayo, P. Tsoutsanis, K. Jenkins

  eccomas2022.

  
  

  Abstract

  We present in this work shock-/interface-capturing numerical methods in the finitevolume central-weighted essentially non-oscillatory (CWENO) reconstruction scheme on unstructured grids for the simulation of multi-component or multiphase compressible flows. Using the five-equation interface capturing models of Allaire et al. and Kapila et al. in the open-source unstructured compressible flow solver UCNS3D, we will demonstrate the capabilities and robustness of the CWENO in capturing and resolving the material interface in multicomponent/multiphase flows in the presence of strong gradients and material discontinuities, with oscillation free solutions and reduced numerical diffusion. To test our numerical methods, a simple one-dimensional test case and a more sophisticated 2d underwater test case with cavitation are considered. The numerical results of our study are compared with results from existing high-order methods. The results show that the CWENO is less dissipative without the spurious oscillations that typically develop at material boundaries and also gives a high-resolution description of the moving material interface with less artificial smearing than other high other schemes.

  Abstract
  We present in this work shock-/interface-capturing numerical methods in the finitevolume central-weighted essentially non-oscillatory (CWENO) reconstruction scheme on unstructured [...]

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• Development lengths for non-newtonian flows in pipes and tubes based on the wall shear stress

  C. Lambride, A. Syrakos, G. Georgiou

  eccomas2022.

  
  

  Abstract

  The development length needed for tube flows to re-adjust from a uniform to the fully-developed velocity profile is usually defined as the length required for the centerline velocity to reach 99% of its fully-developed value. This definition, however, may be quite inaccurate in non-Newtonian flows with almost flat velocity distributions near the centerline, since the velocity far from the axis of symmetry develops more slowly. Shear-thinning and viscoplasticity may cause the flow close to the centerline to evolve faster than that closer to the walls. Thus, alternative definitions of the development length have been proposed for viscoplastic flows. Given that blood exhibits shear thinning, we numerically solve the flow development of power-law fluids in pipes and calculate the development length as a function of the radius, determining the global development length along with the standard centerline estimate. We also consider an alternative definition, based on the evolution of the wall shear stress. Results have been obtained for values of the power-law exponent ranging from 0.

  Abstract
  The development length needed for tube flows to re-adjust from a uniform to the fully-developed velocity profile is usually defined as the length required for the centerline [...]

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• On the effect of Prandtl number to subgrid-scale heat flux models

  F. Trias, D. Santos, J. Hopman, A. Gorobets, A. Oliva

  eccomas2022.

  
  

  Abstract

  Estimations of the grid size and computational cost for direct numerical simulation (DNS) and large-eddy simulation (LES) of Rayleigh-Bénard convection (RBC) are presented in the {Ra, P r} phase space. Computational requirements to reach the so-called asymptotic Kraichnan or ultimate regime of turbulence using DNS are far too expensive. Therefore, we turn to LES to predict the large-scale behavior at very high Ra-numbers. However, a priori alignment studies clearly show why the modelization of the SGS heat flux is the main difficulty that (still) precludes reliable LES of buoyancy-driven flows at (very) high Ra-numbers. This inherent difficulty can be by-passed by carrying out simulations at low-P r numbers where no SGS heat flux activity is expected. This opens the possibility to reach the ultimate regime carrying out LES of RBC at low-P r using meshes of 10101011grid points. Nevertheless, to do so, we firstly need to combine proper numerical techniques for LES (also DNS) with an efficient use of modern hybrid supercomputers.

  Abstract
  Estimations of the grid size and computational cost for direct numerical simulation (DNS) and large-eddy simulation (LES) of Rayleigh-Bénard convection (RBC) are presented [...]

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• Towards proper subgrid-scale model for jet aerodynamics and aeroacoustics

  A. Duben, J. Ruano, F. Trias, A. Gorobets

  eccomas2022.

  
  

  Abstract

  This article presents the investigation of different grey-area mitigation (GAM) techniques towards achieving accurate subsonic turbulent round jet aerodynamics and aeroacoustics results. Combinations of new adapting subgrid length scales with 2D detecting LES models are used as the GAM technique. The numerical simulations are carried out on a set of refining meshes using two different scale-resolving codes: NOISEtte and OpenFOAM. The results show that all the considered techniques provide appropriate accuracy to predict the noise generated and the importance of both the numerical scheme and how subgrid eddy viscosity is modelled.

  Abstract
  This article presents the investigation of different grey-area mitigation (GAM) techniques towards achieving accurate subsonic turbulent round jet aerodynamics and aeroacoustics [...]

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