#large eddy simulation

[fuckyeahfluiddynamics]

Improving Turbulence Models

Calculating turbulent flows like those found in the ocean and atmosphere is extremely expensive computationally. That's why forecasting models use techniques like Large Eddy Simulation (LES), where large physical scales are calculated according to the governing physical equations while smaller scales are approximated with mathematical models. (Image credit: CasSa Paintings; research credit: K. Jakhar et al.; via APS)

[fuckyeahfluiddynamics]

Fans of sci-fi and fantasy have a long-standing tradition of exploring the physics and/or practicality of creations in their fandom, and Star Wars fans are no exception. (Image credit: Y. Ling et al.)

[fuckyeahfluiddynamics]

Controlling Aerosols Onstage

Few industries saw more disruption from the pandemic than the performing arts. To help orchestras return to the concert hall in a way that keeps performers and audience members safe, researchers have simulated air flow and aerosols around musicians onstage.  (Image credit: top - M. Nägeli, simulation - H. Hedworth et al.; research credit: H. Hedworth et al.; via NYTimes; submitted by Kam-Yung Soh) Read the full article

[fuckyeahfluiddynamics]

Spiderwebs and Stratocumulus Clouds

Stratocumulus clouds cover about 20% of Earth's surface at any given time, and they form distinctive patterns of lumpy cells separated by thin slits. Because of their interconnectedness, researchers nicknamed these narrow regions spiderwebs. (Image credits: featured image - L. Dauphin/MODIS, others - UConn ME 3250; research credit: G. Matheou et al.) Read the full article

[fuckyeahfluiddynamics]

Canada’s Bay of Fundy has some of the wildest tidal flows in the world. Every six hours, the flow direction through the strait shifts and tidal currents rise to several meters per second. This creates distinct jets a couple kilometers long that pour from one side of the strait to the other. 

What you see here is a numerical simulation of the flow using a technique called Large Eddy Simulation (or LES, for short). It’s one method used by fluid dynamicists to model turbulent flows without taking on the complexity of the full Navier-Stokes equations. At large lengthscales, like those of the jets and eddies we see above, LES uses the exact physics. But when it comes to the smaller scales -- like the flow nearest the shores or the bottom of the strait -- the simulation will approximate the physics in order to make calculations quicker and easier. Models like these make large-scale problems -- including modeling our daily weather patterns -- possible. (Image credit: A. Creech, source)

[fuckyeahfluiddynamics]

As the climate warms, many urban centers are facing stronger and more frequent storms. Some, like New York City, are using numerical simulations to better understand the interactions of their complicated urban geometries with hurricane force winds. 

Above you see a simulation showing predicted wind speeds in a Lower Eastside neighborhood. The incoming wind speed (from the left) is roughly 60 m/s (~134 mph), but the speeds around and between buildings are as much as 2 times higher than that. That means that, even if a storm is Category 3 or 4, there will be areas of a neighborhood that receive sustained winds well beyond the range of a Category 5 hurricane. Urban planners need this sort of data both for devising building requirements and for understanding what storm conditions warrant mandatory evacuations for residents. (Video and image credit: X. Jiang et al.)

[fuckyeahfluiddynamics]

The latest FYFD/JFM video is out! May brings us a look at the incredible flight of dandelion seeds, numerical simulations that reveal the flow above forest canopies, and a look at bee-inspired flapping wing robots being developed for exploring Mars! Learn about all this in the video below, and, if you’ve missed other videos in the series, you can catch up here. (Image and video credit: N. Sharp and T. Crawford)

[tobias-gerken]

A gas mixing into a forest

This is a large eddy simulation of a gas mixing into a forest. If we want to understand how gases that are emitted by forests react within the canopy-airspace, we must be able to simulate how their reaction partners, such as ozone are mixed downward. 

During the night there is little ozone within the canopy and once turbulence picks up in the morning, ozone from above is mixed downwards where it can react with plant emitted hydrocarbons.