Challenging the large eddy simulation technique with advanced <i>a posteriori</i> tests

Bou‐Zeid, Elie

doi:10.1017/jfm.2014.616

Cited by 17 publications

(9 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A well-established method called Large Eddy Simulation (LES) allows computation of turbulence on relatively coarse grids that account for Sub-Grid Scale (SGS) dynamics through an SGS model (see e.g. Deardorff (1970); Pope (2004); Bou-Zeid (2015)). The case of acoustic streaming appears as a reverse situation wherein a large scale flow (the acoustic streaming) emerges from small scale fluctuations (the acoustic wave).…”

Section: Streaming Source Spatial Filtering (Sssf)mentioning

confidence: 99%

On the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method

et al. 2017

View full text Add to dashboard Cite

Received XX revised XX accepted XX -To be entered by editorial office)When an acoustic wave travels in a lossy medium such as a liquid, it progressively transfers its pseudo-momentum to the fluid, which results in a steady acoustic streaming. Remarkably, the phenomenon involves a balance between sound attenuation and shear, such that viscosity vanishes in the final expression of the velocity field. For this reason, the effect of viscosity has long been ignored in acoustic streaming experiments. Here, we show experimentally that the viscosity plays a major role in cavities such as the streaming induced by surface acoustic waves in sessile droplets. We develop a numerical model based on the spatial filtering of the streaming source term to compute the induced flow motion with dramatically reduced computational requirements. We evidence that acoustic fields in droplets are a superposition of a chaotic field and a few powerful caustics. It appears that the caustics drive the flow, which allows a qualitative prediction of the flow structure. Finally, we reduce the problem to two dimensionless numbers related to the surface and bulk waves attenuation and simulate hemispherical sessile droplets resting on a lithium niobate substrate for a range of parameters. Even in such a baseline configuration, we observe at least four distinct flow regimes. For each of them, we establish a correlation of the average streaming speed in the droplet, which is increasingly dependent on the bulk wave attenuation as the viscosity increases. These correlations extend our results to a wide range of fluids and actuation frequencies.Key words: Authors should not enter keywords on the manuscript, as these must be chosen by the author during the online submission process and will then be added during the typesetting process (see http://journals.cambridge.org/data/relatedlink/jfmkeywords.pdf for the full list) † Email address for correspondence: michael.baudoin@univ-lille1.fr / Web site:

show abstract

Section: Streaming Source Spatial Filtering (Sssf)mentioning

confidence: 99%

On the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Numerical flow simulations provide a very economical alternative to investigate different design parameters and operational conditions. LES is emerging as a tool of choice for many environmental and engineering problems since it provides robust and detailed results at a manageable computational cost. Many of the simulations of HAWT wind farms surveyed in the introduction use LES, and it is currently the most widely adopted tool for simulations of Atmospheric Boundary Layer (ABL) flows since it can directly resolve the impact of important ABL features, including static stability and the far‐wake of bluff bodies such as wind turbines or buildings.…”

Section: Numerical Modelsmentioning

confidence: 99%

Simulation and wake analysis of a single vertical axis wind turbine

et al. 2016

Self Cite

View full text Add to dashboard Cite

Because of several design advantages and operational characteristics, particularly in offshore farms, vertical axis wind turbines (VAWTs) are being reconsidered as a complementary technology to horizontal axial turbines. However, considerable gaps remain in our understanding of VAWT performance since cross‐flow rotor configurations have been significantly less studied than axial turbines. This study examines the wakes of VAWTs and how their evolution is influenced by turbine design parameters. An actuator line model is implemented in an atmospheric boundary layer large eddy simulation code, with offline coupling to a high‐resolution blade‐scale unsteady Reynolds‐averaged Navier–Stokes model. The large eddy simulation captures the turbine‐to‐farm scale dynamics, while the unsteady Reynolds‐averaged Navier–Stokes captures the blade‐to‐turbine scale flow. The simulation results are found to be in good agreement with three existing experimental datasets. Subsequently, a parametric study of the flow over an isolated VAWT, carried out by varying solidities, height‐to‐diameter aspect ratios and tip speed ratios, is conducted. The analyses of the wake area and velocity and power deficits yield an improved understanding of the downstream evolution of VAWT wakes, which in turn enables a more informed selection of turbine designs for wind farms. Copyright © 2016 John Wiley & Sons, Ltd.

show abstract

“…We can then define a dimensionless group as the four-thirds power of the scale separation that is known as the Reynolds number (Re), Ã on the order of millimeters. This is not feasible for 3D turbulence resolving studies and may remain elusive for a considerable period in the future (Bou-Zeid 2015). Therefore, in virtually all studies that employ DNS for ABL flows, an offer is made with respect to the Reynolds number, assuming that for sufficiently large values of Re, certain relevant (scaled) statistics become insensitive to its exact value, a concept known as ''Reynolds-number similarity.''…”

Section: Toward a Direct Numerical Simulation Studymentioning

confidence: 99%

An Idealized Description for the Diurnal Cycle of the Dry Atmospheric Boundary Layer

Hooft

Baas

Tiggelen

et al. 2019

Journal of the Atmospheric Sciences

View full text Add to dashboard Cite

We present a conceptual model for the diurnal cycle of the dry atmospheric boundary layer (ABL). It may serve as a framework for future numerical studies on the transitional dynamics that characterize the ABL over land. The conceptual model enables us to define expressions for relevant physical scales as a function of the most prominent forcing parameters and the low degree of complexity facilitates a dimensionless description. This is useful to help generalize boundary layer dynamics that occur on a diurnal time scale. Further, the model’s application for numerical studies is illustrated herein with two examples: a single-column-model study that assesses the effect of wind forcing on the main characteristics of the diurnal cycle, and a large-eddy-simulation study on the daily evolution of turbulence under weak-wind-forcing conditions. The results from these studies sketch the general evolution of the present set of diurnal-cycle systems in more detail. We discuss how the setups are able to reproduce well-known dynamical features of the ABL and also highlight limitations, where the simple conceptual system is unable to describe realistic ABL behavior. We conclude that the present conceptual model has an interesting balance between model-system complexity and physical realism, such that it is useful for future idealized studies on the diurnal cycle of the ABL.

show abstract

Challenging the large eddy simulation technique with advanced a posteriori tests

Cited by 17 publications

References 16 publications

On the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method

On the influence of viscosity and caustics on acoustic streaming in sessile droplets: an experimental and a numerical study with a cost-effective method

Simulation and wake analysis of a single vertical axis wind turbine

An Idealized Description for the Diurnal Cycle of the Dry Atmospheric Boundary Layer

Contact Info

Product

Resources

About