Special Issue "Recent Advances in Computational Methods in Fluid Dynamics and Applications, Volume II"

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Mathematical and Computational Fluid Mechanics".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 5011

Special Issue Editor

Prof. Dr. Ramesh Agarwal
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Guest Editor
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1099, St. Louis, MO 63130, USA
Interests: computational fluid dynamics (CFD); computational magnetohydrodynamics (MHD); electromagnetics; computational aeroacoustics; multidisciplinary design and optimization; rarefied gas dynamics and hypersonic flows, bio-fluid dynamics; flow and flight control
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Special Issue Information

Dear Colleagues,

With nearly five decades of development, there have been tremendous advancements in the basic building blocks of computational fluid dynamics (CFD), namely, geometry modeling and mesh generation, numerical algorithms for the solution of fluid dynamics equations, and turbulence modeling. A large number of proprietary and commercial CFD codes have been developed that are now routinely used in all industrial applications involving fluid flow. Nevertheless, new advances continue to emerge in all building blocks of CFD. In this Special Issue, papers are invited from researchers on higher-order spatial and temporal numerical schemes, entropy stable schemes, gas-kinetic schemes, algorithms for overset meshes and adaptive meshes, parallel algorithms, analysis of algorithms, uncertainty quantifications, verification and validation, large data and machine learning algorithms, and other advanced topics. Papers are also invited on wall-modeled and wall-resolved methods for DES, LES, and DNS, as well as new turbulence models for RANS. Papers on large-scale CFD computations using advanced algorithms are especially welcome.

Prof. Dr. Ramesh K. Agarwal
Guest Editor

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Keywords

  • computational fluid dynamics
  • geometry modeling
  • mesh generation
  • numerical algorithms
  • fluid dynamics equations

Published Papers (4 papers)

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Research

Article
High-Order Accurate Numerical Simulation of Supersonic Flow Using RANS and LES Guided by Turbulence Anisotropy
Fluids 2022, 7(12), 385; https://doi.org/10.3390/fluids7120385 - 14 Dec 2022
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Abstract
This paper discusses accuracy improvements to Reynolds-Averaged Navier–Stokes (RANS) modeling of supersonic flow by assessing a wide range of factors for physics capture. Numerical simulations reveal complex flow behavior resulting from shock and expansion waves and so, a supersonic jet emanating from rectangular [...] Read more.
This paper discusses accuracy improvements to Reynolds-Averaged Navier–Stokes (RANS) modeling of supersonic flow by assessing a wide range of factors for physics capture. Numerical simulations reveal complex flow behavior resulting from shock and expansion waves and so, a supersonic jet emanating from rectangular nozzle is considered. PIV based experimental data for the jet is available from literature and is used for validation purposes. Effect of various boundary conditions and turbulence modeling approaches is assessed qualitatively and quantitatively. Of particular interest are the inlet conditions considering the turbulence intensity and the effect of upstream air supply duct, the effect of nozzle wall surface roughness on nozzle internal flow and downstream, wall y+ sensitivity for boundary layer resolution and laminar to turbulent transition modeling. In addition to mesh sensitivity, domain dependency is conducted to evaluate the appropriate domain size to capture the kinetic energy dissipation downstream of the nozzle. To further improve the flow characteristics, accounting for the anisotropy of Reynolds stresses is also one of the focuses. Therefore, non-linear eddy viscosity-based two-equation model and Reynolds stress transport model are also investigated. Additionally, the results of baseline linear (Boussinesq) RANS are compared. Corresponding comparisons with high-fidelity LES are presented. Jet self-similar behavior resulting from all simulation fidelities is assessed and it appears that turbulent flow in LES becomes self-similar, but not in RANS. Finally, various factors such as the nozzle geometry and numerical modeling choices influencing the anisotropy in jet turbulence are discussed. Full article
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Article
On Energy Redistribution for the Nonlinear Parabolized Stability Equations Method
Fluids 2022, 7(8), 264; https://doi.org/10.3390/fluids7080264 - 03 Aug 2022
Cited by 1 | Viewed by 736
Abstract
We identify and quantify a seemingly overlook mechanism for energy transfer between adjacent frequency disturbances in the Nonlinear Parabolized Stability Equations method. Physically, this energy transfer results from the finite-bandwidth nature of actual disturbance spectrums versus the common numerical assumption of a discrete [...] Read more.
We identify and quantify a seemingly overlook mechanism for energy transfer between adjacent frequency disturbances in the Nonlinear Parabolized Stability Equations method. Physically, this energy transfer results from the finite-bandwidth nature of actual disturbance spectrums versus the common numerical assumption of a discrete spectrum representation. Both quiet wind tunnel and flight conditions are considered and it is found that, for Mack’s second-mode instability, the mechanism is most significant in the 0.1–1% disturbance amplitude range (based on normalized pressure) and is responsible for a 15–30% increase in predicted disturbance amplitude. Full article
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Article
Numerical Simulation of High-Density Ratio Bubble Motion with interIsoFoam
Fluids 2022, 7(5), 152; https://doi.org/10.3390/fluids7050152 - 25 Apr 2022
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Abstract
The breeding blanket is one of the fundamental components of a nuclear fusion reactor and is responsible for the fuel production, generating tritium through neutronic capture reaction between lithium and neutrons. Lithium is a liquid PbLi alloy and the helium formed as reaction [...] Read more.
The breeding blanket is one of the fundamental components of a nuclear fusion reactor and is responsible for the fuel production, generating tritium through neutronic capture reaction between lithium and neutrons. Lithium is a liquid PbLi alloy and the helium formed as reaction by-product can coalesce into bubbles, generating a two-phase mixture with a high-density ratio (ηρO5). These bubbles can accumulate and stagnate within the blanket channels with potentially harmful consequences. In this work, the interIsoFoam solver of OpenFOAM v2012 is used to simulate bubble motion for a two-phase mixture representative of the He-PbLi system to test its potential for future developments in the field of fusion. In a first phase, several traditional benchmarks were carried out, both 2D and 3D, and considering the two variants of the VOF method implemented in the solver, isoAdvector and plicRDF. Subsequently, He bubbles of different diameters rising in liquid PbLi (ηρ=1.2×105) were analysed to investigate different regimes. For a Eötvös number (Eo) greater than 10, it was possible to recreate the axisymmetric, skirted, oscillatory regimes and the peripheral and central breakup regimes. For Eo < 10, non-physical deformations of the interface are observed, probably generated by spurious velocities that have a greater impact on the solution for very small bubbles and rising velocities. Full article
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Article
Comparison of Flow Behavior in Saccular Aneurysm Models Using Proper Orthogonal Decomposition
Fluids 2022, 7(4), 123; https://doi.org/10.3390/fluids7040123 - 23 Mar 2022
Cited by 1 | Viewed by 1223
Abstract
Aneurysms are abnormal ballooning of a blood vessel. Previous studies have shown presence of complex flow structures in aneurysms. The objective of this study was to quantify the flow features observed in two selected saccular aneurysm geometries over a range of inflow conditions [...] Read more.
Aneurysms are abnormal ballooning of a blood vessel. Previous studies have shown presence of complex flow structures in aneurysms. The objective of this study was to quantify the flow features observed in two selected saccular aneurysm geometries over a range of inflow conditions using Proper Orthogonal Decomposition (POD). For this purpose, two rigid-wall saccular aneurysm models geometries were used (i.e., the bottleneck factor of 1 and 1.6), and the inflow conditions were varied using a peak Reynolds number (Rep) from 50 and 270 and Womersley number (α) from 2 and 5. The velocity flow field data for the studied aneurysm geometries were acquired using Particle Image Velocimetry (PIV). The average flow field from the PIV measurement showed that the model geometry and Rep have more significant impact on the average flow field than the variations in α. The POD results showed that the method was able to quantify the flow field characteristics between the two model geometries. The mode shapes obtained showed different spatial structures for each inflow scenarios and models. The POD energy results showed that more than 80% of the fluctuating kinetic energy were captured within five POD modes for BF=1.0 flow scenarios, while they were captured within ten modes for BF=1.6. The time varying coefficient results showed the complex interplay of POD modes at different inflow scenarios, highlighting important modes at different phases of the flow cycle. The low-order reconstruction results showed that the vortical structure either proceeded outward or stayed within the aneurysm, and this behavior was highly dependent on α, Rep, and model geometry that were not evident in average PIV results. Full article
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