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1

Numerical study of detonation processes in rotating detonation engine and its propulsive performance

Yi Tae-Hyeong, Lou Jing, Turangan Cary Kenny, Wolanski Piotr

Transactions on Aerospace Research

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2020

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Nr 3 (260)

30--48

EN

Numerical studies on detonation wave propagation in rotating detonation engine and its propulsive performance with one- and multi-step chemistries of a hydrogen-based mixture are presented. The computational codes were developed based on the three-dimensional Euler equations coupled with source terms that incorporate high-temperature chemical reactions. The governing equations were discretized using Roe scheme-based finite volume method for spatial terms and second-order Runge-Kutta method for temporal terms. One-dimensional detonation simulations with one- and multi-step chemistries of a hydrogen-air mixture were performed to verify the computational codes and chemical mechanisms. In two-dimensional simulations, detonation waves rotating in a rectangular chamber were investigated to understand its flowfield characteristics, where the detailed flowfield structure observed in the experiments was successfully captured. Three-dimensional simulations of two-waved rotating detonation engine with an annular chamber were performed to evaluate its propulsive performance in the form of thrust and specific impulse. It was shown that rotating detonation engine produced constant thrust after the flowfield in the chamber was stabilized, which is a major difference from pulse detonation engine that generates repetitive and intermittent thrust.

PL

Przedstawiono badania numeryczne propagacji fali detonacyjnej w wirującym silniku detonacyjnym oraz jego wydajności pędnej z jedno- i wielostopniową mieszanką chemiczną na bazie wodoru. Kody obliczeniowe opracowano w oparciu o trójwymiarowe równania Eulera w połączeniu z pojęciami źródłowymi, które obejmują wysokotemperaturowe reakcje chemiczne. Obowiązujące równania zostały zdyskredytowane przy użyciu metody skończonej objętości opartej na schemacie Roe'a dla terminów przestrzennych oraz metody Runge-Kutta drugiego rzędu dla terminów czasowych. W celu weryfikacji kodów obliczeniowych i mechanizmów chemicznych przeprowadzono jednowymiarowe symulacje detonacji z jedno- i wieloetapowymi chemikaliami mieszaniny wodoru i powietrza. W symulacjach dwuwymiarowych badano fale detonacyjne obracające się w komorze prostokątnej w celu zrozumienia jej charakterystyki pola przepływu, gdzie udało się uchwycić szczegółową strukturę pola przepływu zaobserwowaną w doświadczeniach. Przeprowadzono trójwymiarowe symulacje dwufalowego wirującego silnika detonacyjnego z komorą pierścieniową w celu oceny jego właściwości pędnych w postaci ciągu i impulsu właściwego. Wykazano, że wirujący silnik detonujący wytwarza stały ciąg po ustabilizowaniu się pola przepływu w komorze, co stanowi istotną różnicę w stosunku do silnika detonującego impulsowo, który wytwarza powtarzalny i przerywany ciąg.

2

Numerical simulation of the auto-ignition and DDT by AMR

Tang X., Dziemińska E., Hayashi A. K., Tsuboi N., Asahara M.

Archivum Combustionis

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2017

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Vol. 37 nr 2

79--92

EN

In our previous work, combustion flows in a smooth tube are simulated with fixed computational meshes to investigate the auto-ignition and the subsequent deflagration to detonation transition (DDT). In this paper, we use another approach, which is adaptive mesh refinement (AMR) technology, to reproduce above detailed DDT as a pilot study of the further study of three-dimensional (3D) DDT with high resolutions and detailed chemical reaction mechanism. The auto-ignition and DDT are successfully captured by AMR system with a much smaller cost. The results are similar to the previous ones. In this paper especially the formation of precursor shock is discussed in details to present how the piston effect works and why the present initial condition can allow a rapid DDT. It is shown that due to the choice of initial conditions, the flame acceleration process in this work is carried out in a very short time because that the reflected shocks with an adequate strength successfully generate a region with high pressure and another region on the flame tip with a fresh gas of a high density. Subsequently, the pressure accumulation benefits the temperature distribution in the form of shock heating, especially in the boundary layer. An auto ignition triggers the DDT in the heated mixture in front of the flame.

3

A dynamically adaptive lattice Boltzmann method for thermal convection problems

Feldhusen K., Deiterding R., Wagner C.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 4

735--747

EN

Utilizing the Boussinesq approximation, a double-population incompressible thermal lattice Boltzmann method (LBM) for forced and natural convection in two and three space dimensions is developed and validated. A block-structured dynamic adaptive mesh refinement (AMR) procedure tailored for the LBM is applied to enable computationally efficient simulations of moderate to high Rayleigh number flows which are characterized by a large scale disparity in boundary layers and free stream flow. As test cases, the analytically accessible problem of a two-dimensional (2D) forced convection flow through two porous plates and the non-Cartesian configuration of a heated rotating cylinder are considered. The objective of the latter is to advance the boundary conditions for an accurate treatment of curved boundaries and to demonstrate the effect on the solution. The effectiveness of the overall approach is demonstrated for the natural convection benchmark of a 2D cavity with differentially heated walls at Rayleigh numbers from 103 up to 108. To demonstrate the benefit of the employed AMR procedure for three-dimensional (3D) problems, results from the natural convection in a cubic cavity at Rayleigh numbers from 103 up to 105 are compared with benchmark results.

4

Adaptive finite elements based on sensitivities fortopological mesh changes

Friederich J., Leugering G., Steinmann P.

Control and Cybernetics

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2014

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Vol. 43, no. 2

279--306

EN

We propose a novel approach to adaptive refinement in FEM based on local sensitivities for node insertion. To this end, we consider refinement as a continuous graph operation, for instance by splitting nodes along edges. Thereby, we introduce the concept of the topological mesh derivative for a given objective function. For its calculation, we rely on the first-order asymptotic expansion of the Galerkin solution of a symmetric linear second-order elliptic PDE. In this work, we apply this concept to the total potential energy, which is related to the approximation error in the energy norm. In fact, our approach yields local sensitivities for minimization of the energy error by refinement. Moreover, we prove that our indicator is equivalent to the classical explicit a posteriori error estimator in a certain sense. Numerical results suggest that our method leads to efficient and competitive adaptive refinement.

5

Adaptive mesh refinement for magnetic stimulation modeling

Sawicki B.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 5

152-154

EN

The aim of the paper is discussion of need for adaptive mesh refinement techniques for numerical modeling of magnetic stimulation. Problems of a' posteriori error estimation and automatic mesh refinement algorithms has been addressed. Results present that values in the solution can be changed up to 40% during refinement process. It has been shown that refinement algorithms introduce serious computational cost for realistic 3D meshes.

PL

Celem artykułu jest przedstawienie potrzeby wykorzystania adaptacyjnych algorytmów poprawy sieci elementów skończonych podczas modelowania zagadnień stymulacji magnetycznej. Omówiono problemy estymacji błędu lokalnego, automatycznego zagęszczania sieci bez pogorszenia jej jakości. Wyniki pokazują ponad 40% zmianę wartości rozwiązania podczas poprawiania sieci. Nie można jednak zapominać, że zagęszczanie realistycznej, trójwymiarowej siatki wiąże się z dużymi nakładami obliczeniowymi.

6

Software for adaptive refinement of finite element meshes using 2-D and 2-D electromagnetic field analysis

Gawrylczyk K. M., Alkhatib F.

Poznan University of Technology Academic Journals. Electrical Engineering

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2006

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No 52

51-61

7

A scalability Study of SGI Clustered XFS Using HDF Based AMR Application

Saini S., Talcott D., Yeung H., Myers G., Ciotti R.

Computational Methods in Science and Technology

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2006

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Vol. spec. issue

47-54

EN

Many large-scale parallel scientific and engineering applications, especially climate modeling, often run for lengthy periods and require data checkpointing periodically to save the state of the computation for a program restart. In addition, such applications need to write data to disks for post-processing, e.g., visualization. Both these scenarios involve a write-only pattern using Hierarchal Data Format (HDF) files. In this paper, we study the scalability of CXFS by HDF based Structured Adaptive Mesh Refinement (AMR) application for three different block sizes. The code used is a block-structured AMR hydrodynamics code that solves compressible, reactive hydrodynamic equations and characterizes physics and mathematical algorithms used in studying nuclear flashes on neutron stars and white dwarfs. The computational domain is divided into blocks distributed across the processors. Typically, a block contains 8 zones in each coordinate direction (x, y, and z) and a perimeter of guard cells (in this case, 4 zones deep) to hold information from the neighbors. We used three different block sizes of 8 × 8 × 8, 16 × 16 × 16, and 32 × 32 × 32. Results of parallel I/O bandwidths (checkpoint file and two plot files) are presented for all three-block sizes on a wide range of processor counts, ranging from 1 to 508 processors of the Columbia system.