Article
Mechanics
M. Vernet, M. Pereira, S. Fauve, C. Gissinger
Summary: An experiment was conducted to study the flow of an electrically conducting fluid in a thin disc under the influence of an azimuthal Lorentz force. Different flow patterns were observed, including quasi-Keplerian velocity profiles, turbulent flow with large fluctuations and a Keplerian mean rotation profile, and a quasi-bidimensional turbulent flow with the formation of large scale condensates in the horizontal plane. These results are attributed to the instability of the Bodewadt-Hartmann layers at large Reynolds numbers and are discussed within the context of similar astrophysical turbulent flows.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Chang Liu, Dennice F. Gayme
Summary: The structured-singular-value-based approach proposed in this paper preserves certain input-output properties of the nonlinear forcing function to recover a larger range of key flow features. This method not only identifies flow structures predicted by traditional approaches but also captures oblique turbulent bands that have been observed in experiments and DNS.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Christopher J. Camobreco, Alban Potherat, Gregory J. Sheard
Summary: The transition to turbulence in conduits has been a long-standing problem in fluid mechanics, and understanding how to promote or suppress turbulence is crucial for energy production and conservation. While a global picture of three-dimensional (3-D) turbulence is emerging, subcritical turbulence in flows approaching two dimensions has not been observed. However, stability analysis and simulations have shown a subcritical quasi-two-dimensional (quasi-2-D) transition from laminar flow to turbulence, driven by nonlinear Tollmien-Schlichting waves. This alternative scenario calls for new thinking and strategies to control transition in rotating devices and nuclear fusion reactor blankets.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Minghan Chu, Xiaohua Wu, David E. E. Rival
Summary: This study utilizes a physics-based uncertainty quantification framework to estimate the uncertainty in Reynolds-averaged Navier-Stokes models by introducing eigenvalue, eigenvector, and turbulence kinetic energy perturbations. A regression-based marker function is introduced for simulating laminar-turbulent transitional flows, and a monotonic behavior of the predicted uncertainty bounds is observed with respect to turbulence kinetic energy perturbation. The predicted uncertainty bounds show a synergy behavior when eigenvalue perturbations are augmented with the marker function, significantly increasing the size of the uncertainty bounds.
Article
Mechanics
Takahiro Nemoto, Alexandros Alexakis
Summary: The study reveals that the decay time scale of turbulence in pipe flows increases double-exponentially as Reynolds number approaches its critical value, influenced by the transition between stable turbulence and metastable states.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
K. P. Sarath, K. V. Manu
Summary: This study investigates the stability and transition to turbulence in a diverging channel with a time-varying trapezoidal inflow boundary condition. Three categories of flow behavior are observed based on different Reynolds numbers and deceleration rates. The characteristics of primary instability, secondary instability, and streamwise vorticity generation are successfully captured using numerical simulations and dynamic mode decomposition algorithm.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Duo Xu, Baofang Song, Marc Avila
Summary: The study reveals that in pulsatile and oscillatory flows through pipes, high pulsation amplitudes can lead to the replacement of classic stream-wise vortices by helical disturbances and the dominance of axisymmetric disturbances under high frequency and Reynolds number conditions. These optimal disturbances reach their peaks in a short time period and show exponential energy gain scaling with the Reynolds number of the oscillatory flow component.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
S. Benard, W. Herreman, J. L. Guermond, C. Nore
Summary: In this study, we investigated swirling electrovortex flows in a cylinder filled with GaInSn metal through numerical simulations. Different flow regimes were identified and the velocity magnitude was studied both numerically and theoretically. The influence of the aspect ratio and wiring configuration on the flow was analyzed. Additionally, a simple model was proposed to explain the variation of flow intensity with wire radius.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Byron Guerrero, Martin F. Lambert, Rey C. Chin
Summary: This study investigates the time response and transient turbulence dynamics of rapidly decelerating turbulent pipe flows. Through statistical analysis of direct numerical simulations, it is found that turbulent flows undergo four transitional stages: inertial, friction recovery, turbulence decay, and core relaxation. The FIK identity is used to understand the time response of the skin friction coefficient.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Niccolo Tonicello, Guido Lodato, Luc Vervisch
Summary: The study discusses a high-order low dissipative numerical framework for modeling unresolved sub-grid scale flow turbulence and capturing shock waves simultaneously. It evaluates the accuracy of the recently developed Spectral Element Dynamic Model by simulating flows around two different airfoil profiles. The results show that the model performs well in detecting spatial under-resolution in high-order flow simulations.
FLOW TURBULENCE AND COMBUSTION
(2022)
Article
Mechanics
Joan Gomez, Huidan Yu, Yiannis Andreopoulos
Summary: The primary focus of this experimental work is the instability and transition to turbulence in pulsatile flows, which involve reverse flows and unsteady flow separations. By conducting experiments with different Reynolds and Womersley numbers, it was found that transition to turbulence is a spontaneous event covering the whole near-wall region.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Fabian Burmann, Jerome Noir
Summary: Experimental results on flows in a precessing triaxial ellipsoid show two branches of solutions for the uniform vorticity component as a function of the Poincare number. The first branch is characterized by large total fluid rotation amplitude and moderate tilt angle of the fluid rotation axis, while the second branch tends to align with the precession axis. Early occurrences of parametric instabilities saturate in the second branch, where the kinetic energy in the base flow and instabilities are of the same order.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Shyuan Cheng, Leonardo P. Chamorro, Phillip J. Ansell
Summary: A series of experiments were conducted to investigate the sources of local, high-amplitude velocity fluctuations produced during the late stages of boundary-layer flow transition to turbulence. The experiments involved controlled injection of Tollmien-Schlichting (TS) waves into a laminar boundary layer, leading to H-type transition to turbulence. Proper orthogonal decomposition (POD) was used to analyze the coherent structures and frequencies associated with the transition process. The study identified the crucial role of hairpin vortices in the overshoot mechanisms observed during late transition stage and developed a reduced-order model to explain these phenomena.
Article
Mechanics
Carlo Camporeale, Fabio Cannamela, Claudio Canuto, Costantino Manes
Summary: This paper presents results from a linear stability analysis of turbulent depth-averaged open-channel flows with secondary currents, showing the existence of sinuous instability and the conditions required for its presence. The study suggests that VLSMs might be triggered by nonlinear mechanisms and LSMs could be governed by an outer-layer cycle.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Biophysics
A. L. Haley, K. Valen-Sendstad, D. A. Steinman
Summary: Recent comparisons between experiments and CFD simulations show potential sensitivity of axisymmetric CFD models to small perturbations induced by mesh and inlet velocity for flow in FDA standardized nozzle geometry. While high-fidelity CFD of a non-axisymmetric stenosis model shows transition at Re - 700-800, experimental measurements report transition at Re - 400-500. Adding small-magnitude random noise at the inlet in the simulations brings CFD results more in-line with experiments, revealing a more gradual transition towards turbulence.
JOURNAL OF BIOMECHANICS
(2021)
Article
Mechanics
Niranjan S. Ghaisas, Steven H. Frankel
JOURNAL OF TURBULENCE
(2016)
Article
Mechanics
Niranjan S. Ghaisas, Dinesh A. Shetty, Steven H. Frankel
JOURNAL OF TURBULENCE
(2015)
Article
Nanoscience & Nanotechnology
Qian Li, Yann Delorme, Steven H. Frankel
MICROFLUIDICS AND NANOFLUIDICS
(2016)
Article
Computer Science, Interdisciplinary Applications
Vikram Singh, Steven Frankel
COMPUTERS & FLUIDS
(2020)
Article
Engineering, Chemical
Chandra Shekhar Pant, Yann Delorme, Steven Frankel
Article
Computer Science, Interdisciplinary Applications
Viktor Linders, Jan Nordstrom, Steven H. Frankel
JOURNAL OF COMPUTATIONAL PHYSICS
(2020)
Article
Engineering, Aerospace
Yann Delorme, Ronith Stanly, Steven H. Frankel, David Greenblatt
Summary: A hybrid computational approach combining LES and ALM is used to simulate the turbulent wake of a two-bladed rotor in hover. The method is validated against previous predictions and measurements, and demonstrates a novel way to explore active flow control strategies to reduce rotor noise.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Computer Science, Interdisciplinary Applications
Amareshwara Sainadh Chamarthi, Steven H. Frankel
Summary: In this paper, a novel hybrid nonlinear explicit-compact scheme for shock capturing based on a boundary variation diminishing (BVD) reconstruction is presented. The method combines a non-dissipative sixth-order central compact interpolation and a fifth-order monotonicity preserving scheme through the BVD algorithm. Numerical examples suggest that the method is capable of resolving small scale flow features and capturing sharp discontinuities as the MP5 scheme.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Vikram Singh, Steven Frankel, Jan Nordstrom
Summary: In this study, a kinetic energy stability estimate is developed to investigate the stability of wall model boundary conditions. It is found that the equilibrium stress wall model is unstable, while the dynamic slip wall model is stable. Numerical tests show that the equilibrium stress wall model is accurate but unstable, whereas the dynamic slip wall model is inaccurate but stable.
COMPUTERS & FLUIDS
(2021)
Article
Engineering, Civil
Ronith Stanly, Luis A. Martinez-Tossas, Steven H. Frankel, Yann Delorme
Summary: Combining large-eddy simulation (LES) with actuator line models (ALMs) allows accurate and affordable simulations of multirotor devices. A new filtered ALM (F-ALM) with tip correction has been proposed to prevent overprediction of power on coarse grids.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Engineering, Marine
Chandra Shekhar Pant, Steven H. Frankel
Summary: Numerical simulations were conducted to investigate the impact of active flow control on unsteady cavitation on a modified scaled-down Francis turbine, showing that the efficacy of wall jet injection in mitigating cavitation is limited by large pressure fluctuations induced by the interaction between the re-entrant jet and the wall jet under the studied operating conditions.
Article
Remote Sensing
Galia Faingold, Leonid Tartakovsky, Steven H. Frankel
Article
Computer Science, Interdisciplinary Applications
Yann T. Delorme, Kunal Puri, Jan Nordstrom, Viktor Linders, Suchuan Dong, Steven H. Frankel
COMPUTERS & FLUIDS
(2017)
Article
Computer Science, Interdisciplinary Applications
Ory Haimovich, Steven H. Frankel
COMPUTERS & FLUIDS
(2017)
Article
Computer Science, Interdisciplinary Applications
Yann T. Delorme, Mark D. Rodefeld, Steven H. Frankel
COMPUTERS & FLUIDS
(2017)
