Article
Engineering, Mechanical
Yu Xia, Patrick Sharkey, Ishan Verma, Alok Khaware, Davor Cokljat
Summary: This study successfully predicts the thermoacoustic oscillations and structural deformations in a laboratory-scale three-dimensional burner, providing support for realistic gas turbine combustor design and prognosis.
JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME
(2022)
Article
Mechanics
Lijun Yang, Bosheng Pang, Jingxuan Li
Summary: In this study, the differences between using weakly and strongly nonlinear flame models to predict thermoacoustic instability under various operating conditions were compared. It was found that the weakly nonlinear flame model performs well when the dominant acoustic mode is much stronger than other modes, but fails to capture mode frequency and growth rate when multiple unstable modes are present.
Article
Thermodynamics
Maria Castela, Alam Garciduenas Correa, Jason S. Damazo, Deanna A. Lacoste
Summary: Experimental study on thermoacoustic coupling of methane flames in small diameter tubes revealed that thermoacoustic instability impacts flame propagation and can lead to flame quenching. Depending on the tube length (acoustics), flames either fully propagate or extinguish prematurely.
COMBUSTION AND FLAME
(2021)
Article
Mechanics
Dan Zhao, Yiheng Guan
Summary: Self-excited thermoacoustic instabilities are frequently observed in rocket motors, gas turbines, ramjets, and aeroengine afterburners, which are highly detrimental and undesirable for engine manufacturers. This study predicts and characterizes modal growth behaviors in the presence of transverse and longitudinal combustion instabilities through thermoacoustic dynamics coupling studies. The derived maximum growth rate is experimentally confirmed to be greater than the practical measurements, and a phase drift is observed. The effects of variables such as the interaction index, time-delay, specific heat ratio, and acoustic losses/damping are examined.
Article
Chemistry, Physical
Shoutao Hu, Zijin Hong, Jiancun Gao, Ruxia Li, Quan Wang, Le Wang, Xigang Yang
Summary: The effect of magnetic materials on hydrogen explosion was investigated through experiments and simulations. It was found that aluminium wires inhibit hydrogen explosion when the volume fraction of hydrogen is below 20%, while nickel wires promote it. On the other hand, when the volume fraction of hydrogen is above 25%, aluminium wires promote hydrogen explosion while nickel wires inhibit it. In general, the ferromagnetic nickel wires have a better effect in inhibiting and promoting hydrogen explosion compared to aluminium wires, due to the induced magnetic field generated during the explosion process that influences key radicals in the chain reaction.
SUSTAINABLE ENERGY & FUELS
(2023)
Article
Mechanics
Ziyu Qin, Xinyao Wang, Xiao Han, Yuzhen Lin, Yuchen Zhou
Summary: This paper utilizes deep learning to gain a deeper understanding of thermoacoustic instability and achieve more reliable early warning. Flame images and pressure series are collected in model combustors, resulting in seven data domains. A pre-trained model called TIPE is trained to align the image and pressure signals in the embedding space. Transfer learning based on k-nearest neighbors is then performed for thermoacoustic instability prediction. The results show that the pre-trained model outperforms supervised models with improved resistance to class imbalance and better generalization.
Article
Engineering, Aerospace
Baoyin Ma, Junwei Li, Zhihui Zhang, Yunzhi Xi, Dan Zhao, Ningfei Wang
Summary: The study reveals that when the heat source position is fixed in solid rocket motors, combustion transitions from stable to very unstable as the equivalence ratio increases from 0.9 to 1.5, then returns to a stable state. The strongest pressure oscillations are observed in the rich combustion region and when the heat source is close to the nozzle exit, reaching approximately 122-125 dB in amplitude. The experimental method and theoretical model used can accurately estimate the stability map and limit cycle characteristics of thermoacoustic oscillation in solid rocket motors.
Article
Thermodynamics
Zongming Yu, Yuhua Ai, Yue Wang, Chuanzhi Luo
Summary: The study investigated the thermoacoustic instability of a laminar lean premixed flame in gas turbine combustors through theoretical analysis and numerical simulation, focusing on the autoignition and propagation mechanism of the flame. Results showed that the three-step mechanism could effectively describe the high-temperature chemistry involved in autoignition and flame propagation.
COMBUSTION AND FLAME
(2021)
Article
Mechanics
Meng Han, Xiao Han, Xinyao Wang, Lei Li
Summary: The present study investigates the effect of the exit geometry of the main stage on thermoacoustic instabilities in a model combustor with a dual-swirl layout. Experimental results show that most exit geometries lead to a sudden transition in flame shape, triggering strong thermoacoustic oscillation. Analysis of flame dynamics and reacting flow fields reveals that increased roughness of the outer wall can prevent flame shape transition and thermoacoustic instability.
Article
Thermodynamics
Xinyao Wang, Xiao Han, Chih-Jen Sung
Summary: In the start-up process of practical gas turbine applications, the modulation of operating condition could cause variations of stability regimes. An experimental investigation was conducted on the transitions of thermoacoustic modes and flame dynamics in a centrally-staged swirl combustor over a range of operating conditions. The results provide a guideline for quantifying the stability regimes of fuel-flexible combustors during the operating condition modulation processes.
Article
Thermodynamics
Ahmed Hamood, Artur J. Jaworski
Summary: This paper introduces a traveling-wave thermoacoustic generator that is free from a wavelength long loop for waste heat recovery applications.
Article
Acoustics
Alessandro Orchini, Tiemo Pedergnana, Philip E. Buschmann, Jonas P. Moeck, Nicolas Noiray
Summary: This study investigates the thermoacoustic instabilities in stationary gas turbines with a can-annular configuration. By studying a reduced-order system, the physical origin of the instabilities is better understood. The properties of the eigenvalues and eigenvectors of can-annular combustors are analyzed, with emphasis on the differences in can-to-can coupling under different boundary conditions.
JOURNAL OF SOUND AND VIBRATION
(2022)
Article
Thermodynamics
Max Meindl, Camilo F. Silva, Wolfgang Polifke
Summary: This study demonstrates the generation of spurious entropy waves when a hybrid approach for linear thermoacoustic stability analysis is employed to model acoustically forced premixed flames, attributing the unphysical behavior to the inability of the global Flame Transfer Function (FTF) to account for flame movement effects. The study also shows that the utilization of a local FTF can suppress the spurious entropy perturbations, highlighting the importance of fine-grained resolution of heat release rate fluctuations in the combustion zone for modeling flame movement. The Linearized Reactive Flow (LRF) approach is proposed as an alternative to hybrid models, which inherently accounts for locally resolved flame dynamics and eliminates the need for a local FTF, providing validation against high resolution CFD results.
COMBUSTION AND FLAME
(2021)
Article
Acoustics
G. Ghirardo, F. Gant
Summary: In this study, the acoustic flow field of rotationally symmetric systems and the influence of background noise on system states were investigated. Random background noise causes the system to randomly transition between spinning and standing states, and the intensity of noise affects the system's preference for these states. New methods were employed to track these changes and demonstrate the impact of noise intensity on the system dynamics.
JOURNAL OF SOUND AND VIBRATION
(2021)
Article
Astronomy & Astrophysics
Marcela Carena, Henry Lamm, Ying-Ying Li, Wanqiang Liu
Summary: This study introduces two schemes for determining Minkowski lattice spacings using tools from Euclidean lattice field theory, as well as advocates for a fixed-anisotropy approach to reduce circuit depth and number of independent simulations. These methods are demonstrated using qiskit noiseless simulators for a 2 thorn 1D discrete nonAbelian D4 gauge theory with two spatial plaquettes.
Article
Thermodynamics
Hans Yu, Matthew P. Juniper, Luca Magri
Summary: This study developed and tested a physics-based reduced-order model of a ducted premixed flame, where model parameters were learned from high-speed videos. By assimilating experimental data into a level-set solver using an ensemble Kalman filter, an optimally calibrated reduced-order model accurately reproduced complex nonlinear features, matching experiments even after assimilation was switched off. The automatically extracted model parameters were found to match the expected first-order behavior based on physics, showcasing how reduced-order models can be rapidly updated with new data availability without storing the data itself.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Thermodynamics
Stephan F. Oehler, Simon J. Illingworth
Summary: The study examines linear feedback flow control of the largest scales in an incompressible turbulent channel flow at a friction Reynolds number of Re-tau = 2000. It is found that a control set-up with a well-placed array of sensors and actuators performs comparably to either measuring the flow everywhere or actuating the flow everywhere, providing insight into estimating and controlling the very large scales of turbulence effectively at low computational cost.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2021)
Article
Physics, Fluids & Plasmas
Bo Jin, Sean Symon, Simon J. Illingworth
Summary: The study investigates energy transfer mechanisms for vortex shedding in the two-dimensional cylinder wake at a Reynolds number of Re = 100. It is found that linear mechanisms achieve an energy balance on their own, respecting the Reynolds-Orr equation, while nonlinear mechanisms significantly contribute to the transfer of energy to higher frequencies. However, the resolvent analysis does not accurately model nonlinear energy transfer between temporal frequencies, leading to discrepancies in energy balance compared to DNS.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mathematics, Applied
Gunther Waxenegger-Wilfing, Ushnish Sengupta, Jan Martin, Wolfgang Armbruster, Justin Hardi, Matthew Juniper, Michael Oschwald
Summary: A data-driven method for early detection of thermoacoustic instabilities is proposed and shows good performance on experimental data, comparing with state-of-the-art early warning indicators.
Article
Mechanics
Vikrant Gupta, Anagha Madhusudanan, Minping Wan, Simon J. Illingworth, Matthew P. Juniper
Summary: The study uses Navier-Stokes-based linear models to estimate large-scale fluctuations at different positions in wall-bounded turbulent flows, finding that the models perform reasonably accurately when considering the variation of stochastic forcing and eddy dissipation terms with wall distance and length scale.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
S. Demange, U. A. Qadri, M. P. Juniper, F. Pinna
Summary: This study investigates the stability features of spatially spreading heated jets in the viscous regime with real gas effects, using both unsteady two-dimensional axisymmetric simulations and linear analyses. The study confirms that including real gas effects in the stability equations has a strong effect on the growth rate of the global mode. Linear global analyses over the time-averaged states provide a satisfying prediction of the oscillation's frequency and the baroclinic torque obtained from the resulting global mode matches well with that of the simulations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Bo Jin, Simon J. Illingworth, Richard D. Sandberg
Summary: This study focuses on linear feedback control of two-dimensional flow past a cylinder at low Reynolds numbers, specifically looking at the optimal placement of a single sensor and a single actuator. By calculating the leading resolvent forcing and response modes of the flow, H-2-optimal estimators and controllers are designed. The research investigates optimal estimation, full-state information control, and overall feedback control, highlighting the importance of sensor and actuator placements in determining feedback control performance under varying Reynolds numbers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Denis Busquet, Olivier Marquet, Francois Richez, Matthew Juniper, Denis Sipp
Summary: Numerical investigation of stalling flow around a static airfoil at high Reynolds numbers revealed the existence of stable and unstable modes, including low-frequency stall modes and high-frequency vortex shedding modes. The study also showed how periodic solutions oscillate around steady solutions in phase space and how the disappearance of the limit cycle is due to bifurcations of periodic orbits.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Bo Jin, Simon J. Illingworth, Richard D. Sandberg
Summary: This study focuses on the estimation and control of the cylinder wake at low Reynolds numbers, with an emphasis on developing efficient numerical algorithms for designing optimal linear feedback controllers. The proposed resolvent-based iterative algorithm allows for optimal estimation of the flow using a limited number of sensors and optimal control when only a limited number of actuators are available. The method takes advantage of the low-rank characteristics of the cylinder wake and provides full-dimensional solutions by implementing a terminal reduction technique based on resolvent analysis.
THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS
(2022)
Article
Physics, Fluids & Plasmas
Anagha Madhusudanan, Simon J. Illingworth, Ivan Marusic, Daniel Chung
Summary: In this study, the linearized Navier-Stokes equations were used to investigate the large-scale flow structures in unstably stratified turbulent channel flows. By comparing the results of the linear model with direct numerical simulations, it was found that the linearized Navier-Stokes equations augmented with eddy-viscosity and eddy-diffusivity could successfully predict the emergence of quasistreamwise rolls, and the temperature fluctuations exhibited similar characteristics as observed in the simulations.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Alexandros Kontogiannis, Scott Elgersma, Andrew J. Sederman, Matthew P. Juniper
Summary: In this paper, we propose a method to solve the problem of joint velocity field reconstruction and boundary segmentation of noisy flow velocity images. The method is tested on synthetic images and experimental images, and its effectiveness and accuracy are demonstrated. The method also provides additional knowledge about the physics of the flow and addresses the shortcomings of other measurement methods.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Acoustics
Matthew P. Juniper, Matthew Yoko
Summary: In this study, we conducted 7000 experiments on an electrically-heated Rijke tube and assimilated the data using Bayesian inference. We developed a 1D pipe flow model for long timescale behavior and several 1D thermoacoustic network models for short timescale behavior. The models were ranked based on their marginal likelihood and the best model was selected for each component. The results showed that the selected model was physically-interpretable, simplified, and accurate across the entire operating regime. Furthermore, the model could be trained on limited data and successfully extrapolated beyond the training set.
JOURNAL OF SOUND AND VIBRATION
(2022)
Article
Computer Science, Artificial Intelligence
Alexandros Kontogiannis, Matthew P. Juniper
Summary: This study proposes a physics-informed compressed sensing (PICS) method for reconstructing velocity fields from noisy and sparse phase-contrast magnetic resonance signals. The method solves an inverse Navier-Stokes boundary value problem and is able to reconstruct and segment velocity fields while inferring hidden parameters. The problem is regularized using a Bayesian framework and Gaussian random fields as prior information. The algorithm developed in this study successfully reconstructs and segments velocity fields from noisy and sparse signals, showing good agreement with fully-sampled high SNR signals.
IEEE TRANSACTIONS ON IMAGE PROCESSING
(2023)
Article
Engineering, Multidisciplinary
Yubiao Sun, Ushnish Sengupta, Matthew Juniper
Summary: We use a physics-informed neural network (PINN) to model and optimize the flow around an airfoil for maximizing lift to drag ratio. The PINN takes airfoil shape parameters as inputs and approximates the Navier-Stokes equations using collocation points. The gradients of the lift-to-drag ratio with respect to the shape parameters are calculated using the differentiability of the PINN.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Computer Science, Interdisciplinary Applications
Tian Liang, Lin Fu
Summary: In this work, a new shock-capturing framework is proposed based on a new candidate stencil arrangement and the combination of infinitely differentiable non-polynomial RBF-based reconstruction in smooth regions with jump-like non-polynomial interpolation for genuine discontinuities. The resulting scheme achieves high order accuracy and resolves genuine discontinuities with sub-cell resolution.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Lukas Lundgren, Murtazo Nazarov
Summary: In this paper, a high-order accurate finite element method for incompressible variable density flow is introduced. The method addresses the issues of saddle point system and stability problem through Schur complement preconditioning and artificial compressibility approaches, and it is validated to have high-order accuracy for smooth problems and accurately resolve discontinuities.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Gabriele Ciaramella, Laurence Halpern, Luca Mechelli
Summary: This paper presents a novel convergence analysis of the optimized Schwarz waveform relaxation method for solving optimal control problems governed by periodic parabolic PDEs. The analysis is based on a Fourier-type technique applied to a semidiscrete-in-time form of the optimality condition, which enables a precise characterization of the convergence factor at the semidiscrete level. The behavior of the optimal transmission condition parameter is also analyzed in detail as the time discretization approaches zero.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Jonas A. Actor, Xiaozhe Hu, Andy Huang, Scott A. Roberts, Nathaniel Trask
Summary: This article introduces a scientific machine learning framework that uses a partition of unity architecture to model physics through control volume analysis. The framework can extract reduced models from full field data while preserving the physics. It is applicable to manifolds in arbitrary dimension and has been demonstrated effective in specific problems.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Nozomi Magome, Naoki Morita, Shigeki Kaneko, Naoto Mitsume
Summary: This paper proposes a novel strategy called B-spline based SFEM to fundamentally solve the problems of the conventional SFEM. It uses different basis functions and cubic B-spline basis functions with C-2-continuity to improve the accuracy of numerical integration and avoid matrix singularity. Numerical results show that the proposed method is superior to conventional methods in terms of accuracy and convergence.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Timothy R. Law, Philip T. Barton
Summary: This paper presents a practical cell-centred volume-of-fluid method for simulating compressible solid-fluid problems within a pure Eulerian setting. The method incorporates a mixed-cell update to maintain sharp interfaces, and can be easily extended to include other coupled physics. Various challenging test problems are used to validate the method, and its robustness and application in a multi-physics context are demonstrated.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Xing Ji, Fengxiang Zhao, Wei Shyy, Kun Xu
Summary: This paper presents the development of a third-order compact gas-kinetic scheme for compressible Euler and Navier-Stokes solutions, constructed particularly for an unstructured tetrahedral mesh. The scheme demonstrates robustness in high-speed flow computation and exhibits excellent adaptability to meshes with complex geometrical configurations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Alsadig Ali, Abdullah Al-Mamun, Felipe Pereira, Arunasalam Rahunanthan
Summary: This paper presents a novel Bayesian statistical framework for the characterization of natural subsurface formations, and introduces the concept of multiscale sampling to localize the search in the stochastic space. The results show that the proposed framework performs well in solving inverse problems related to porous media flows.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Jacob Rains, Yi Wang, Alec House, Andrew L. Kaminsky, Nathan A. Tison, Vamshi M. Korivi
Summary: This paper presents a novel method called constrained optimized DMD with Control (cOptDMDc), which extends the optimized DMD method to systems with exogenous inputs and can enforce the stability of the resulting reduced order model (ROM). The proposed method optimally places eigenvalues within the stable region, thus mitigating spurious eigenvalue issues. Comparative studies show that cOptDMDc achieves high accuracy and robustness.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Andrea La Spina, Jacob Fish
Summary: This work introduces a hybridizable discontinuous Galerkin formulation for simulating ideal plasmas. The proposed method couples the fluid and electromagnetic subproblems monolithically based on source and employs a fully implicit time integration scheme. The approach also utilizes a projection-based divergence correction method to enforce the Gauss laws in challenging scenarios. Numerical examples demonstrate the high-order accuracy, efficiency, and robustness of the proposed formulation.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Junhong Yue, Peijun Li
Summary: This paper proposes two numerical methods (IP-FEM and BP-FEM) to study the flexural wave scattering problem of an arbitrary-shaped cavity on an infinite thin plate. These methods successfully decompose the fourth-order plate wave equation into the Helmholtz and modified Helmholtz equations with coupled conditions on the cavity boundary, providing an effective solution to this challenging problem.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
William Anderson, Mohammad Farazmand
Summary: We develop fast and scalable methods, called RONS, for computing reduced-order nonlinear solutions. These methods have been proven to be highly effective in tackling challenging problems, but become computationally prohibitive as the number of parameters grows. To address this issue, three separate methods are proposed and their efficacy is demonstrated through examples. The application of RONS to neural networks is also discussed.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Marco Caliari, Fabio Cassini
Summary: In this paper, a second order exponential scheme for stiff evolutionary advection-diffusion-reaction equations is proposed. The scheme is based on a directional splitting approach and uses computation of small sized exponential-like functions and tensor-matrix products for efficient implementation. Numerical examples demonstrate the advantage of the proposed approach over state-of-the-art techniques.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Sebastiano Boscarino, Seung Yeon Cho, Giovanni Russo
Summary: This work proposes a high order conservative semi-Lagrangian method for the inhomogeneous Boltzmann equation of rarefied gas dynamics. The method combines a semi-Lagrangian scheme for the convection term, a fast spectral method for computation of the collision operator, and a high order conservative reconstruction and a weighted optimization technique to preserve conservative quantities. Numerical tests demonstrate the accuracy and efficiency of the proposed method.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)
Article
Computer Science, Interdisciplinary Applications
Jialei Li, Xiaodong Liu, Qingxiang Shi
Summary: This study shows that the number, centers, scattering strengths, inner and outer diameters of spherical shell-structured sources can be uniquely determined from the far field patterns. A numerical scheme is proposed for reconstructing the spherical shell-structured sources, which includes a migration series method for locating the centers and an iterative method for computing the inner and outer diameters without computing derivatives.
JOURNAL OF COMPUTATIONAL PHYSICS
(2024)