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Book ; Online: Neural Ideal Large Eddy Simulation

Boral, Anudhyan / Wan, Zhong Yi / Zepeda-Núñez, Leonardo / Lottes, James / Wang, Qing / Chen, Yi-fan / Anderson, John Roberts / Sha, Fei

Modeling Turbulence with Neural Stochastic Differential Equations

2023

Abstract: We introduce a data-driven learning framework that assimilates two powerful ideas: ideal large eddy ...

Abstract	We introduce a data-driven learning framework that assimilates two powerful ideas: ideal large eddy simulation (LES) from turbulence closure modeling and neural stochastic differential equations (SDE) for stochastic modeling. The ideal LES models the LES flow by treating each full-order trajectory as a random realization of the underlying dynamics, as such, the effect of small-scales is marginalized to obtain the deterministic evolution of the LES state. However, ideal LES is analytically intractable. In our work, we use a latent neural SDE to model the evolution of the stochastic process and an encoder-decoder pair for transforming between the latent space and the desired ideal flow field. This stands in sharp contrast to other types of neural parameterization of closure models where each trajectory is treated as a deterministic realization of the dynamics. We show the effectiveness of our approach (niLES - neural ideal LES) on a challenging chaotic dynamical system: Kolmogorov flow at a Reynolds number of 20,000. Compared to competing methods, our method can handle non-uniform geometries using unstructured meshes seamlessly. In particular, niLES leads to trajectories with more accurate statistics and enhances stability, particularly for long-horizon rollouts. Comment: 18 pages
Keywords	Computer Science - Machine Learning ; Mathematics - Numerical Analysis
Subject code	621
Publishing date	2023-06-01
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: A Flexible Eddy Current TMR Sensor for Monitoring Internal Fatigue Crack.

Yang, Fei / He, Yuting / Fan, Xianghong / Chen, Tao / Zhang, Teng / Ma, Binlin

Sensors (Basel, Switzerland)

2023 Volume 23, Issue 23

Abstract: This paper proposes a flexible eddy current TMR (FEC-TMR) sensor to monitor the internal crack ...

Abstract	This paper proposes a flexible eddy current TMR (FEC-TMR) sensor to monitor the internal crack of metal joint structures. First, the finite element model of the FEC-TMR sensor is established to analyze the influence of the sensor's crack identification sensitivity with internal crack propagation at different depths and determine the optimal location and exciting frequency of the sensor. Then, the optimal longitudinal spacing and exciting frequency of the sensor are tested by experiment. The experimental results are consistent with the simulation results, which verify the correctness of the simulation model. Finally, the experiment is carried out for internal cracks of different depths to verify that the sensor can monitor internal cracks, and the crack identification sensitivity gradually decreases with the increase in the depth of the crack from the surface.
Language	English
Publishing date	2023-11-29
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s23239507
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: A lightweight deep learning model for ocean eddy detection

Haochen Sun / Hongping Li / Ming Xu / Fan Yang / Qiang Zhao / Cuishu Li

Frontiers in Marine Science, Vol

2023 Volume 10

Abstract: ... high energy. Traditional eddy detection methods are mainly based on physical mechanisms with high ... broadly used in the field of ocean remote sensing. This paper proposes a lightweight eddy detection model ... ghost eddy detection YOLO (GED-YOLO), based on sea level anomaly data and the “You Only Look Once” (YOLO ...

Abstract	Ocean eddies are typical oceanic mesoscale phenomena that are numerous, widely distributed and have high energy. Traditional eddy detection methods are mainly based on physical mechanisms with high accuracy. However, the large number of steps and complex parameter settings limit their applicability for most users. With the rapid development of deep learning techniques, object detection models have been broadly used in the field of ocean remote sensing. This paper proposes a lightweight eddy detection model, ghost eddy detection YOLO (GED-YOLO), based on sea level anomaly data and the “You Only Look Once” (YOLO) series models. The proposed model used ECA+GhostNet as the backbone network and an atrous spatial pyramid pooling network as the feature enhancement network. The ghost eddy detection path aggregation network was proposed for feature fusion, which reduced the number of model parameters and improved the detection performance. The experimental results showed that GED-YOLO achieved better detection precision and smaller parameter size. Its mAP was 95.11% and the parameter size was 22.56 MB. In addition, the test experiment results showed that GED-YOLO had similar eddy detection performance and faster detection speed compared to the traditional physical method.
Keywords	ocean eddies ; sea level anomaly data ; deep learning ; lightweight ; ghost eddy detection YOLO (GED-YOLO) ; Science ; Q ; General. Including nature conservation ; geographical distribution ; QH1-199.5
Subject code	551
Language	English
Publishing date	2023-11-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: The role of eddy-wind interaction in the eddy kinetic energy budget of the Agulhas retroflection region

Yanan Zhu / Yuanlong Li / Yang Yang / Fan Wang

Environmental Research Letters, Vol 18, Iss 10, p

2023 Volume 104032

Abstract: The Agulhas retroflection (AR) region possesses the highest eddy kinetic energy (EKE) level ... in the Indian Ocean. However, mechanisms regulating EKE of the AR remain uncertain. Here, by analyzing an eddy ... a key role in EKE dissipation. The lack of eddy-wind interaction results in flawed EKE budget ...

Abstract	The Agulhas retroflection (AR) region possesses the highest eddy kinetic energy (EKE) level in the Indian Ocean. However, mechanisms regulating EKE of the AR remain uncertain. Here, by analyzing an eddy-resolving coupled model simulation with improved EKE representation, we show that the upper-ocean EKE of the AR is mainly generated through barotropic instability in its upstream and leakage zones and is by nonlocal transport in its downstream zone. The interaction between mesoscale eddies and local winds plays a key role in EKE dissipation. The lack of eddy-wind interaction results in flawed EKE budget in the leakage zone in ocean-alone models, leading to severe biases in EKE distribution with overestimation and over-strong penetration into the South Atlantic. Our results highlight the essence of mesoscale air-sea interaction in the dynamics of the AR, with implications for understanding the inter-basin transport of the Agulhas leakage.
Keywords	mesoscale eddies ; eddy kinetic energy ; mesoscale air-sea interaction ; Agulhas current ; South Indian Ocean ; western boundary currents ; Environmental technology. Sanitary engineering ; TD1-1066 ; Environmental sciences ; GE1-350 ; Science ; Q ; Physics ; QC1-999
Subject code	551
Language	English
Publishing date	2023-01-01T00:00:00Z
Publisher	IOP Publishing
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Large-eddy simulation of vortex-excited force on a square cylinder with transverse wind fluctuations.

Du, Huanhuan / Fan, Zikai / He, Wei / Yang, Zheguang

Scientific reports

2023 Volume 13, Issue 1, Page(s) 14236

Abstract: This study utilized 3D Large-eddy simulation to investigate the crosswind drag force on a square ...

Abstract	This study utilized 3D Large-eddy simulation to investigate the crosswind drag force on a square cylinder subjected to transverse wind fluctuation. Two distinct methods were employed to generate the fluctuation: a prescribed sine function at the inlet boundary and an upwind barrier. The frequency was normalized in the same Strouhal number form. The transverse wind fluctuation with a normalized frequency above 0.05 tends to excite the square cylinder transversely with the same frequency band. The frequency effect also exists on the square cylinder located downwind an obstacle half the square cylinder's size. However, an obstacle 2.5 times the size of the square cylinder generates a cross-wind fluctuation with the normalized frequency of 0.04, which cannot excite the square cylinder transversely. The frequency effect from the upwind barrier significantly dampens with the distance and disappears at 8-10 times the square cylinder size.
Language	English
Publishing date	2023-08-30
Publishing country	England
Document type	Journal Article
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-023-41470-1
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Article ; Online: Large‐Eddy Simulations of a Convection Cloud Chamber

Fan Yang / Mikhail Ovchinnikov / Subin Thomas / Alexander Khain / Robert McGraw / Raymond A. Shaw / Andrew M. Vogelmann

Journal of Advances in Modeling Earth Systems, Vol 14, Iss 5, Pp n/a-n/a (2022)

Sensitivity to Bin Microphysics and Advection

2022

Abstract: ... of advection scheme, which can also change cloud simulation results. Here, an atmospheric large‐eddy ...

Abstract	Abstract Bin microphysics schemes are useful tools for cloud simulations and are often considered to provide a benchmark for model intercomparison. However, they may experience issues with numerical diffusion, which are not well quantified, and the transport of hydrometeors depends on the choice of advection scheme, which can also change cloud simulation results. Here, an atmospheric large‐eddy simulation model is adapted to simulate a statistically steady‐state cloud in a convection cloud chamber under well‐constrained conditions. Two bin microphysics schemes, a spectral bin method and the method of moments, as well as several advection methods for the transport of the microphysical variables are employed for model intercomparison. Results show that different combinations of microphysics and advection schemes can lead to considerable differences in simulated cloud properties, such as cloud droplet number concentration. We find that simulations using the advection scheme that suffers more from numerical diffusion tends to have a smaller droplet number concentration and liquid water content, while simulation with the microphysics scheme that suffers more from numerical diffusion tends to have a broader size distribution and thus larger mean droplet sizes. Sensitivities of simulations to bin resolution, spatial resolution, and temporal resolution are also tested. We find that refining the microphysical bin resolution leads to a broader cloud droplet size distribution due to the advection of hydrometeors. Our results provide insight for using different advection and microphysics schemes in cloud chamber simulations, which might also help understand the uncertainties of the schemes used in atmospheric cloud simulations.
Keywords	large eddy simulation ; cloud chamber ; microphysics scheme ; advection scheme ; Physical geography ; GB3-5030 ; Oceanography ; GC1-1581
Subject code	518
Language	English
Publishing date	2022-05-01T00:00:00Z
Publisher	American Geophysical Union (AGU)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Numerical investigation of interaction between anticyclonic eddy and semidiurnal internal tide in the northeastern South China Sea

Fan, Liming / Sun, Hui / Yang, Qingxuan / Li, Jianing

eISSN:

2024

Abstract: We investigate the interaction between an anticyclonic eddy (AE) and semidiurnal internal tide (SIT ... to the eddy field at an average rate of 3.0 mW m −2 (accounting for 7 % of the incoming energy flux of SIT ... when integrated over the eddy diameter). Second, the AE can modify the spatial distribution of tidal-induced ...

Abstract	We investigate the interaction between an anticyclonic eddy (AE) and semidiurnal internal tide (SIT) on the continental slope of the northeastern South China Sea (SCS), using a high spatiotemporal resolution numerical model. Two key findings are as follows: first, the AE promotes energy conversion from low-mode to higher-mode SIT. Additionally, production terms indicate that energy is also transferred from the SIT field to the eddy field at an average rate of 3.0 mW m −2 (accounting for 7 % of the incoming energy flux of SIT when integrated over the eddy diameter). Second, the AE can modify the spatial distribution of tidal-induced dissipation by refracting, scattering, and reflecting low-mode SIT. The phase and group velocities of the SIT are significantly influenced by the eddy field, resulting in a northward or southward shift in the internal tidal rays. These findings deepen our understanding of the complex interactions between AE and SIT, as well as their impacts on energy conversion, wave propagation, and coastal processes.
Subject code	551
Language	English
Publishing date	2024-02-21
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Numerical investigation of interaction between anticyclonic eddy and semidiurnal internal tide in the northeastern South China Sea

Fan, Liming / Sun, Hui / Yang, Qingxuan / Li, Jianing

eISSN: 1812-0792

2024

Abstract	We investigate the interaction between an anticyclonic eddy (AE) and semidiurnal internal tide (SIT) on the continental slope of the northeastern South China Sea (SCS), using a high spatiotemporal resolution numerical model. Two key findings are as follows: first, the AE promotes energy conversion from low-mode to higher-mode SIT. Additionally, production terms indicate that energy is also transferred from the SIT field to the eddy field at an average rate of 3.0 mW m −2 (accounting for 7 % of the incoming energy flux of SIT when integrated over the eddy diameter). Second, the AE can modify the spatial distribution of tidal-induced dissipation by refracting, scattering, and reflecting low-mode SIT. The phase and group velocities of the SIT are significantly influenced by the eddy field, resulting in a northward or southward shift in the internal tidal rays. These findings deepen our understanding of the complex interactions between AE and SIT, as well as their impacts on energy conversion, wave propagation, and coastal processes.
Subject code	551
Language	English
Publishing date	2024-02-21
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Accelerating Large‐Eddy Simulations of Clouds With Tensor Processing Units

Sheide Chammas / Qing Wang / Tapio Schneider / Matthias Ihme / Yi‐fan Chen / John Anderson

Journal of Advances in Modeling Earth Systems, Vol 15, Iss 10, Pp n/a-n/a (2023)

2023

Abstract: ... in climate models. A principal reason is that the high computational expense of simulating them with large‐eddy ...

Abstract	Abstract Clouds, especially low clouds, are crucial for regulating Earth's energy balance and mediating the response of the climate system to changes in greenhouse gas concentrations. Despite their importance for climate, they remain relatively poorly understood and are inaccurately represented in climate models. A principal reason is that the high computational expense of simulating them with large‐eddy simulations (LES) has inhibited broad and systematic numerical experimentation and the generation of large data sets for training parametrization schemes for climate models. Here we demonstrate LES of low clouds on tensor processing units (TPUs), application‐specific integrated circuits that were originally developed for machine learning applications. We show that TPUs in conjunction with tailored software implementations can be used to simulate computationally challenging stratocumulus clouds in conditions observed during the Dynamics and Chemistry of Marine Stratocumulus (DYCOMS) field study. The TPU‐based LES code successfully reproduces clouds during DYCOMS and opens up the large computational resources available on TPUs to cloud simulations. The code enables unprecedented weak and strong scaling of LES, making it possible, for example, to simulate stratocumulus with 10× speedup over real‐time evolution in domains with a 34.7 km × 53.8 km horizontal cross section. The results open up new avenues for computational experiments and for substantially enlarging the sample of LES available to train parameterizations of low clouds.
Keywords	large‐eddy simulation ; stratocumulus clouds ; tensor processing units ; numerical methods ; Physical geography ; GB3-5030 ; Oceanography ; GC1-1581
Subject code	551
Language	English
Publishing date	2023-10-01T00:00:00Z
Publisher	American Geophysical Union (AGU)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Accelerating large-eddy simulations of clouds with Tensor Processing Units

Chammas, Sheide / Wang, Qing / Schneider, Tapio / Ihme, Matthias / Chen, Yi-fan / Anderson, John

2023

Abstract: ... A principal reason is that the high computational expense of simulating them with large-eddy simulations (LES ...

Abstract	Clouds, especially low clouds, are crucial for regulating Earth's energy balance and mediating the response of the climate system to changes in greenhouse gas concentrations. Despite their importance for climate, they remain relatively poorly understood and are inaccurately represented in climate models. A principal reason is that the high computational expense of simulating them with large-eddy simulations (LES) has inhibited broad and systematic numerical experimentation and the generation of large datasets for training parametrization schemes for climate models. Here we demonstrate LES of low clouds on Tensor Processing Units (TPUs), application-specific integrated circuits that were originally developed for machine learning applications. We show that TPUs in conjunction with tailored software implementations can be used to simulate computationally challenging stratocumulus clouds in conditions observed during the Dynamics and Chemistry of Marine Stratocumulus (DYCOMS) field study. The TPU-based LES code successfully reproduces clouds during DYCOMS and opens up the large computational resources available on TPUs to cloud simulations. The code enables unprecedented weak and strong scaling of LES, making it possible, for example, to simulate stratocumulus with $10\times$ speedup over real-time evolution in domains with a $34.7~\mathrm{km} \times 53.8~\mathrm{km}$ horizontal cross section. The results open up new avenues for computational experiments and for substantially enlarging the sample of LES available to train parameterizations of low clouds.
Keywords	Physics - Atmospheric and Oceanic Physics ; Mathematics - Numerical Analysis ; Physics - Computational Physics ; Physics - Fluid Dynamics ; Physics - Geophysics ; J.2
Subject code	551
Publishing date	2023-01-11
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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