Towards Wall-Modeled LES with Lattice Boltzmann Method for Aeroacoustics: Application and Understanding

The aim of this work is direct noise computation (DNC) of high-lift wing using Wall-modeled LES (WMLES) with Lattice Boltzmann Method (LBM). There are two aspects of this work: application, where the commercial LB solver ProLB is used as a DNC tool to compute highlift noise, and understanding, where an effort is made to gather know-how about the intricate details/nuances involved with wall-modeling in LBM by implementing it. For the present study, the Category 6 LEISA2 F16 high-lift configuration from the Benchmark for Airframe Noise Computations (BANC) workshop has been selected as the high-lift airfoil. The three-element unswept high-lift wing with deployed slat and flap is resolved on a mesh with different spanwise resolutions ranging from 5% to 20% clean chord length. Periodic boundary condition is used along the spanwise direction. The results of WMLES-LBM simulations were validated for relative accuracy against the extensive experimental BANC database. Results of both aerodynamic and aeroacoustic comparison with the experiments is discussed in detail. For the aspect of understanding, a quasi-analytical wall function for flat walls has been introduced into the academic LB research code Musubi. Results of the simulation were compared with the published DNS results

Natural radionuclide of Po210 in the edible seafood affected by coal-fired power plant industry in Kapar coastal area of Malaysia

<p>Abstract</p> <p>Background</p> <p>Po²¹⁰can be accumulated in various environmental materials, including marine organisms, and contributes to the dose of natural radiation in seafood. The concentration of this radionuclide in the marine environment can be influenced by the operation of a coal burning power plant but existing studies regarding this issue are not well documented. Therefore, the aim of this study was to estimate the Po²¹⁰concentration level in marine organisms from the coastal area of Kapar, Malaysia which is very near to a coal burning power plant station and to assess its impact on seafood consumers.</p> <p>Methods</p> <p>Concentration of Po²¹⁰was determined in the edible muscle of seafood and water from the coastal area of Kapar, Malaysia using radiochemical separation and the Alpha Spectrometry technique.</p> <p>Results</p> <p>The activities of Po²¹⁰in the dissolved phase of water samples ranged between 0.51 ± 0.21 and 0.71 ± 0.24 mBql^-1whereas the particulate phase registered a range of 50.34 ± 11.40 to 72.07 ± 21.20 Bqkg^-1. The ranges of Po²¹⁰activities in the organism samples were 4.4 ± 0.12 to 6.4 ± 0.95 Bqkg^-1dry wt in fish (<it>Arius maculatus</it>), 45.7 ± 0.86 to 54.4 ± 1.58 Bqkg^-1dry wt in shrimp (<it>Penaeus merguiensis</it>) and 104.3 ± 3.44 to 293.8 ± 10.04 Bqkg^-1dry wt in cockle (<it>Anadara granosa</it>). The variation of Po²¹⁰in organisms is dependent on the mode of their life style, ambient water concentration and seasonal changes. The concentration factors calculated for fish and molluscs were higher than the recommended values by the IAEA. An assessment of daily intake and received dose due to the consumption of seafood was also carried out and found to be 2083.85 mBqday^-1person^-1and 249.30 μSvyr^-1respectively. These values are comparatively higher than reported values in other countries. Moreover, the transformation of Po²¹⁰in the human body was calculated and revealed that a considerable amount of Po²¹⁰can be absorbed in the internal organs. The calculated values of life time mortality and morbidity cancer risks were 24.8 × 10^-4and 34 × 10^-4respectively which also exceeded the recommended limits set by the ICRP.</p> <p>Conclusions</p> <p>The findings of this present study can be used to evaluate the safety dose uptake level of seafood as well as to monitor environmental health. However, as the calculated dose and cancer risks were found to cross the limit of safety, finding a realistic way to moderate the risk is imperative.</p

Konzept und Umgebung für gekoppelte Simulationen von Elektrodialyse-Prozessen

Zugl.: Dissertation, RWTH Aachen University, 2020.Electrodialysis is an efficient process for seawater desalination that involves various interacting phenomena. In this process, ions are transported by flow, diffusion and an electric force and separated by selective membranes. For the optimization of this process, it is important to understand these interactions. This work presents rigorous mathematical models to describe the overall process and develops a numerical strategy for its simulation. With this approach it becomes possible to simulate the involved physical effects and their interactions in detail. To achieve this, the Maxwell-Stefan equations for mixtures are used. They take into account the electrical force and the multicomponent interactions with concentration dependent diffusivity coefficients and thermodynamic factors. Additionally, the usual assumption of local electroneutrality is not assumed to allow the nonideal effects in the electrical double layer near the membrane. For the numerical solution of these equations, the multicomponent lattice Boltzmann method (LBM) is developed and implemented in the solver Musubi. This model for the channel flow is coupled with an electric field and a model for the membranes. To obtain the electric field, the LBM that solves the Poisson’s equation is implemented in Musubi. The channels between the membranes are realized by spacers with complex geometry. A mesh generator (Seeder) on the basis of octrees is developed to ensure the appropriate discretization of the mesh for these channels. An essential part of this work is dedicated to the development of the parallel scaling coupling tool APESmate. APESmate is developed within the APES suite along with Seeder and Musubi on a central octree data structure that allows efficient handing of I/O on large scale distributed parallel computing systems. The developed software is used to compare the nonideal multicomponent model for various concentrations and surface potentials. The results show that nonideal effects increase with the concentration, especially in the electrical double layer. The spacers for various hydrodynamic angles and inflow velocities near and away from a sealed corner are investigated to find the design with reduced pressure drop and without low velocity zones. The highly resolved simulations show that the pressure drop increases with the hydrodynamic angle, while the extend of the low flow regions decreases.Elektrodialyse ist ein effizientes Verfahren zur Meerwasserentsalzung, in dem verschiedene Phänomene zusammenwirken. Ionen werden dabei durch Strömung, Diffusion und eine elektrische Kraft transportiert und mittels selektiven Membranen getrennt. Für die Optimierung dieses Prozesses ist ein Verständnis der Interaktion dieser Effekte wichtig. Diese Arbeit präsentiert rigorose mathematische Modelle des Gesamtprozesses und erarbeitet eine numerische Strategie zur Simulation. Durch diesen Ansatz wird es möglich, die auftretenden Effekte mit ihren komplexen Interaktionen detailliert zu simulieren. Dazu werden die Maxwell-Stefan Gleichungen für Gemische verwendet, die auch die elektrische Kraft und Mehrkomponentenwechselwirkungen mit konzentrationsabhängigen Diffusions- und thermodynamischen Faktoren berücksichtigt. Darüber hinaus wird hier ebenfalls nicht die übliche Annahme der lokalen Elektroneutralität getroffen, um die Effekte in der elektrochemischen Doppelschicht an den Membranen zu ermöglichen. Für die numerische Behandlung dieser Gleichungen wird ein Lattice-Boltzmann (LBM) Verfahren im Löser Musubi implementiert. Das Modell der Kanaldurchströmung wird mit einem elektrischen Feld und einem Modell für die Membranen gekoppelt. Für das elektrische Feld wird in Musubi eine LBM zur Lösung der Poisson Gleichung implementiert. Die Kanäle zwischen den Membranen werden durch Abstandshalter mit komplexer Geometrie realisiert. Um eine passende Diskretisierung des Gitters für diese Kanäle zu gewährleisten wird ein Gittergenerator (Seeder) auf der Basis von Octrees entwickelt. Ein wesentlicher Teil dieser Arbeit ist der Entwicklung des parallel skalierbaren Kopplungswerkzeugs APESmate gewidmet. APESmate wird im Rahmen der APES-Suite neben Seeder und Musubi entwickelt und erlaubt die Interaktion verschiedener Löser auf Basis einer gemeinsamen zentralen Octree-Datenstruktur, die eine effiziente Handhabung der I/O auf großen verteilt parallelen Rechensystemen ermöglicht. Die entwickelte Software wird verwendet, um das nichtideale Mehrkomponentenmodell für verschiedene Konzentrationen und Oberflächenpotentiale zu vergleichen. Die Ergebnisse belegen, dass nichtideale Effekte, insbesondere in der elektrochemischen Doppelschicht, mit der Konzentration zunehmen. Die Abstandshalter werden mit mehreren hydrodynamischen Winkeln und Einströmgeschwindigkeiten nahe und fern einer Ecke untersucht, um die Auslegung mit minimalen Druckabfall und ohne Totwassergebiete zu bestimmen. Diese hochaufgelösten Simulationen zeigen, dass der Druckabfall mit dem hydrodynamischen Winkel zunimmt, während die Größe der Zonen mit geringer Durchströmung abnehmen

Framework for coupled simulation of electrodialysis processes

Electrodialysis is an efficient process for seawater desalination that involves various interacting phenomena. In this process, ions are transported by flow, diffusion and an electric force and separated by selective membranes. For the optimization of this process, it is important to understand these interactions. This work presents rigorous mathematical models to describe the overall process and develops a numerical strategy for its simulation. With this approach it becomes possible to simulate the involved physical effects and their interactions in detail. To achieve this, the Maxwell-Stefan equations for mixtures are used. They take into account the electrical force and the multicomponent interactions with concentration dependent diffusivity coefficients and thermodynamic factors. Additionally, the usual assumption of local electroneutrality is not assumed to allow the nonideal effects in the electrical double layer near the membrane. For the numerical solution of these equations, the multicomponent lattice Boltzmann method (LBM) is developed and implemented in the solver Musubi. This model for the channel flow is coupled with an electric field and a model for the membranes. To obtain the electric field, the LBM that solves the Poisson’s equation is implemented in Musubi. The channels between the membranes are realized by spacers with complex geometry. A mesh generator (Seeder) on the basis of octrees is developed to ensure the appropriate discretization of the mesh for these channels. An essential part of this work is dedicated to the development of the parallel scaling coupling tool APESmate. APESmate is developed within the APES suite along with Seeder and Musubi on a central octree data structure that allows efficient handing of I/O on large scale distributed parallel computing systems.The developed software is used to compare the nonideal multicomponent model for various concentrations and surface potentials. The results show that nonideal effects increase with the concentration, especially in the electrical double layer. The spacers for various hydrodynamic angles and inflow velocities near and away from a sealed corner are investigated to find the design with reduced pressure drop and without low velocity zones. The highly resolved simulations show that the pressure drop increases with the hydrodynamic angle, while the extend of the low flow regions decreases

A robust lattice Boltzmann method for parallel simulations of multicomponent flows in complex geometries

In this work, we are concerned with robust parallel simulations of multicomponent flows in complex ge- ometries by an extended lattice Boltzmann method. In Zudrop et al. (2014) [22] we presented a model for the incompressible Navier-Stokes and Maxwell-Stefan diffusion equations. Here, we prove that the implicit-to-explicit variable transformation of the model is well-posed under weak constraints on the di- mensionless Maxwell-Stefan diffusivities. Furthermore, we analyze various boundary conditions for the multicomponent lattice Boltzmann model. These results make the model robust and well suited for com- plex geometries, which allows us to study realistic, large-scale mass transport applications

Key ingredients for wall-modeled LES with the Lattice Boltzmann method: Systematic comparison of collision schemes, SGS models, and wall functions on simulation accuracy and efficiency for turbulent channel flow

In this study, we consider different combinations of collision schemes, wall functions, and subgrid scale (SGS) models to simulate the bi-periodic turbulent channel flow at . The study is carried out on a lattice stencil, where the considered collision schemes are the Multiple Relaxation Times (MRT), the Hybrid Recursive Regularized Bhatnagar-Gross-Krook (HRR), and the parameterized Cumulant scheme. The considered SGS models are the Smagorinsky, the Wall-Adapting Local Eddy-viscosity (WALE), and the Vreman model. The Cumulant scheme utilizes its intrinsic implicit SGS model. The turbulent velocity profile is modeled with the following wall functions: the Reichardt, the Musker, and a combination of the Werner and Wengle and the Schmitt (Power-law) function. To assure an impartial comparison, all these ingredients are implemented in the same infrastructure, the open-source software Musubi. The comparison of the considered wall functions shows that the Musker function offers a good compromise between accuracy and performance. When comparing the considered SGS models, although the WALE model delivers the most accurate results, the Vreman model offers the fastest computation. On average, the parallel performance improves by . Amongst the considered collision schemes, the Cumulant outperforms the competitors accuracy-wise. However, for the considered test case, the fastest collision scheme is the MRT. Our investigations show that for the considered test case, the best results in terms of accuracy and performance are delivered by the combination of the Cumulant scheme with its implicit SGS model and the Musker wall function