Article
Acoustics
Manuj Awasthi, William J. Devenport, Stewart Glegg
Summary: Measurements were taken of the far-field sound from two types of three-dimensional discontinuities - swept forward-facing steps and a circular embossment - immersed in a low Mach number turbulent boundary layer. The results showed that the far-field sound from the swept forward-facing step scaled with the step-normal component of the boundary-layer edge velocity, while the far-field sound from the circular embossment was qualitatively similar to that from a forward-facing step of the same height. A prediction formula for the embossment noise was derived based on the step-normal velocity scaling and an existing prediction formula for the sound radiated by a forward-facing step, which showed good agreement with the measured sound spectra.
JOURNAL OF SOUND AND VIBRATION
(2023)
Article
Acoustics
Stefan Schoder, Florian Kraxberger, Sebastian Falk, Andreas Wurzinger, Klaus Roppert, Stefan Kniesburges, Michael Doellinger, Manfred Kaltenbacher
Summary: The presented research proposes a filtering technique to detect and correct errors and outliers inside acoustic sources. This method improves data quality and assesses the convergence of aeroacoustic source terms.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2022)
Article
Mechanics
Felix Gstrein, Bin Zang, Mahdi Azarpeyvand
Summary: This study demonstrates that biologically inspired finlet treatments can effectively reduce trailing-edge noise on flat plates, making them a promising technology for noise suppression in engineering applications. Through detailed experiments and analysis, the researchers investigated the near-field dynamics of the flow field and the noise-reduction mechanism of the finlet surface treatments. They found that the interaction between the finlets and the flow generated "finlet-induced turbulence," which effectively reduced the unsteady wall-pressure fluctuations and resulted in a broadband reduction of trailing-edge noise. The study also confirmed the existence of an optimal distance between the finlets and the trailing-edge for maximum mixing effects.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Cheng Zhao, Yan Yang, Tao Zhang, Haibo Dong, Guoxiang Hou
Summary: A hybrid computational approach is proposed to handle acoustic scattering and flow-induced noise problems using the sharp interface immersed boundary method. The method is validated through benchmark acoustic problems and flow past a circular cylinder. The method is further used to predict noise generated by flow around a four-cylinder array with two different arrangements, revealing differences in sound radiation patterns and intensity compared to a single cylinder.
COMPUTERS & FLUIDS
(2021)
Article
Mechanics
Chitrarth Prasad, Datta Gaitonde
Summary: This study develops a method for extracting coherent wavepacket data from high-speed schlieren images and effectively filtering out unwanted acoustic components. When combined with spectral proper orthogonal decomposition (SPOD), the method accurately captures various types of jet dynamics.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Acoustics
Matthieu B. R. Gelot, Jae Wook Kim
Summary: This study examines the feasibility of using Amiet's theory to predict the noise reduction effect of serrated trailing edges, as well as improving prediction accuracy through directivity correction. Experimental results from wall-resolved large-eddy simulations show a significantly improved prediction with this correction method.
JOURNAL OF SOUND AND VIBRATION
(2021)
Article
Computer Science, Interdisciplinary Applications
Oriol Guasch, Arnau Pont, Joan Baiges, Ramon Codina
Summary: In this work, the finite element computation of flow noise in the presence of slowly moving rigid bodies at low Mach numbers is addressed using hybrid and direct computational aeroacoustics (CAA) strategies. The problem is tackled by extending a previous study where the acoustic pressure was split into direct and diffracted components and solved separately using finite element method (FEM). The performance of the proposed methods is demonstrated for aeroacoustics of flow past a oscillating airfoil and flow exiting a duct with a moving teeth-shaped obstacle.
COMPUTERS & FLUIDS
(2022)
Article
Computer Science, Interdisciplinary Applications
Hang Yu, Carlos Pantano
Summary: This paper introduces a new immersed boundary method for simulating compressible viscous flow, which adds surface singularities to the governing equations. Generalizing from the well-known no-slip and isothermal condition to stress and heat flux conditions, as well as extending to porous surfaces, the method is applicable to flow-structure interaction problems.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Jeff D. Eldredge
Summary: The study introduces a discrete Heaviside function to mask fields on the grid and develop operators and identities for any surface geometry. The derived equations include familiar IBM forcing terms as well as additional terms to regularize field jumps onto the grid and specify constraints on field behavior on each side of the interface, referred to as immersed layers. The method is demonstrated on various incompressible flow problems, showcasing its effectiveness in simulation.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Mechanics
Matteo Mancinelli, Vincent Jaunet, Peter Jordan, Aaron Towne
Summary: In this study, a resonance model is used to model and predict the generation mechanism of A1 and A2 screech tones in a subsonic jet. It was found that incorporating the thickness of the shear layer into the jet-dynamics model can improve the accuracy of describing experimental data, and an improved resonance model for screech-frequency predictions was proposed.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Woutijn J. Baars, Nathan E. Murray, Charles E. Tinney
Summary: This study evaluates the acoustic source field produced by a laboratory-scale heated jet with specific Mach numbers, using arrays of microphones traversed across the jet's acoustic field. The analysis identifies the dominant sound production mechanism and studies the spatial topography of the overall sound pressure level. By analysing the sound field on a per-frequency basis, unique data-informed polar patterns of sound intensity are revealed for each frequency, which can be accurately propagated using the inverse square law to gauge errors encountered when calculating sound pressure spectrum levels and acoustic power. The measurement strategy proposed in this study has potential applications in comparing facilities, extrapolating measurements to different scales, validating models, and developing noise control strategies.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Shayan Maleki, Virgilio Fiorotto
Summary: This paper defines a novel model to evaluate the near-bottom effects of added mass and investigates the instantaneous pressure field due to body movement. The study reveals strong body accelerations measured in laboratory experiments that have not been evidenced in previous theoretical studies.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Jeanne Joachim, Carole-Anne Daunais, Valerie Bibeau, Luca Heltai, Bruno Blais
Summary: In this study, a parallel immersed boundary strategy using Nitsche's method (NIB) is proposed to impose boundary conditions on a fluid. The NIB method is validated and compared with other methods in well-established test cases. The versatility of the NIB method is demonstrated by simulating a mixing rig with two off-centered impellers. The software and simulation files used in this study are available in the public domain for reproducibility.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Gregory S. Shallcross, Jesse Capecelatro
Summary: The characteristic-based volume penalization combined with a high-order energy-stable finite difference framework is a computationally efficient method for compressible flows. It improves stability by avoiding increased stiffness associated with boundary treatment and does not require modifications to the computational stencil.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Xiang Zhao, Zhen Chen, Liming Yang, Ningyu Liu, Chang Shu
Summary: In this study, the original boundary condition-enforced immersed boundary method is improved with the use of conjugate gradient technique and explicit technique for simulating incompressible flows with moving boundaries. The computational efficiency of the improved IBM is demonstrated to be higher than other popular IBM methods, especially the explicit technique-based IBM with a linear computational complexity. Coupled with D1Q4 lattice Boltzmann flux solver, the IBM with conjugate gradient technique and explicit technique successfully simulate two-dimensional and three-dimensional flows with second order accuracy in space.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Mechanics
Jung-Hee Seo, Karthik Menon, Rajat Mittal
Summary: This study proposes a method to decompose the loading noise into components related to their generation mechanism and specific vortex structures. The method is applied to sound generation by a circular cylinder and loading noise generation by a pitching airfoil, showing its ability to identify dominant noise generation mechanisms and quantify the effect of vortex structures on noise generation.
Article
Mechanics
Tomas Solano, Chuanxin Ni, Rajat Mittal, Kourosh Shoele
Summary: The effectiveness of face masks depends on both the material and the fit on faces. A new model for masks is presented to study the leakage pattern on realistic faces. Higher porosity reduces leakage.
Article
Mechanics
J. H. Lee, S. Kuhar, J. -H. Seo, P. J. Pasricha, R. Mittal
Summary: This study explores the impact of body posture and stomach motility on drug bioavailability using a biomimetic in silico simulator. The simulations demonstrate that changes in posture significantly affect the emptying rate of the drug into the duodenum, while gastroparesis reduces the dissolution and emptying of the drug. Neuropathic gastroparesis has a greater impact on gastric emptying compared to myopathic gastroparesis.
Article
Physics, Fluids & Plasmas
Wen Wu, Charles Meneveau, Rajat Mittal, Alberto Padovan, Clarence W. Rowley, Louis Cattafesta
Summary: The response of a turbulent separation bubble to zero-net-mass-flux actuation is investigated via direct numerical simulations. The results demonstrate that the length of the separation bubble can be reduced by forming vortex pairs at the appropriate excitation frequencies. In addition, the time-averaged structures exhibit a high sensitivity to the actuation.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Mostafa Aghaei-Jouybari, Jung -Hee Seo, Junlin Yuan, Rajat Mittal, Charles Meneveau
Summary: The force partitioning method is used to analyze the pressure-induced drag for turbulent flow over rough walls. The study quantifies the contributions of rotation-dominated vortical regions and strain-dominated regions to the pressure drag, and investigates the effects of surface geometry on drag. The results suggest that the phi field, which encodes surface geometry, can be used to parametrize the surface drag.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Engineering, Multidisciplinary
Jung-Hee Seo, Rajat Mittal
Summary: This study reveals the mechanism of how a trailing swimmer can improve its swimming performance by utilizing the wake-induced flow of the leading fish. The results show that this mechanism can significantly enhance the thrust and efficiency of the trailing fish. The findings not only contribute to the understanding of fish-fish hydrodynamic interactions but also have potential applications in designing bioinspired propulsion systems.
BIOINSPIRATION & BIOMIMETICS
(2022)
Article
Mechanics
Sharun Kuhar, Jae Ho Lee, Jung-Hee Seo, Pankaj J. Pasricha, Rajat Mittal
Summary: This study simulates the mixing, breakdown, and emptying process of a liquid meal containing protein in a model of a human stomach, and quantifies the effect of stomach motility on the rate of food breakdown.
Article
Physics, Fluids & Plasmas
Karthik Menon, Sushrut Kumar, Rajat Mittal
Summary: This study reports on the mechanisms of vortex-induced lift production in low Reynolds number flows over low aspect-ratio rectangular wings. By using a force-partitioning method, the pressure-induced aerodynamic loads due to distinct flow features or vortex structures around the wing can be estimated. The study shows that cross-span-oriented vortices contribute more to the total lift than spanwise-oriented vortices, and spanwise vortices in the near wake can produce net negative lift on the wing.
PHYSICAL REVIEW FLUIDS
(2022)
Review
Gastroenterology & Hepatology
Anmol Singh, Nikhil Bush, Furqan A. Bhullar, Mahya Faghih, Chris Moreau, Rajat Mittal, Jung-Hee Seo, Rupjyoti Talukdar, Sundeep Lakhtakia, Vikesh K. Singh, Venkata S. Akshintala
Summary: This review evaluates the dynamics of pancreatic duct pressure (PDP), including measurement methods and the clinical implications of elevated PDP. The study found that ductal hypertension is associated with pancreatic diseases and symptoms such as pancreatic pain and pancreatic insufficiency.
Article
Physics, Fluids & Plasmas
Rajat Mittal, Jung Hee Seo
Summary: This article presents the evolutionary history of immersed boundary methods, tracing their origins to the beginning of computational fluid dynamics in the late 1950s. It highlights the advancements in this simulation methodology over the last 50 years and explores the interplay between immersed boundary methods and body conformal grid methods. Drawing upon the authors' combined experience of over 40 years, the article provides a personal and subjective perspective. Through a critical and comparative approach, the article aims to empower readers to understand the capabilities and limitations of these methods and to pursue advancements that fill key gaps and break new ground.
PHYSICAL REVIEW FLUIDS
(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)
