Dynamics of a Vortex Street

Computer model shows Large eddy simulation of Kármán vortex streets in the atmospheric boundary layer
From: Rieke Heinze
Presented at the AMS Conference on Mountain Meteorology, 2010

Description:
Atmospheric vortex streets consist of two rows of counterrotating mesoscale eddies with vertical axis in the wake of large islands. They resemble classical Kármán vortex streets which occur in laboratory experiments behind a cylinder. Usually, atmospheric vortex streets can be found in the stratocumulus capped mixed layer over the ocean when there is a strong elevated inversion well below the island top.

In the animations the island consists of a single Gaussian shaped mountain with a height of about 1.3 km and a base diameter of about 12km. Particles are released in one layer and act as passive tracers. Their vertical motion is disabled. The colour of the particles reflects the difference between the temperature at the respective particle position and the mean temperature, horizontally averaged over the total domain. Blue/red colours represent a relatively low/high temperature. The animation shows that the cores of the eddies are warmer than the environment. The length of the animation corresponds to about 14h real time.

Model Setup:
Total domain size (x|y|z): 144km x 60.8km x 3.8km
Grid spacing (x|y|z): 100m x 100m x 100m
Number of grid points (x|y|z): 1440 x 608 x 32
Simulated time: 14h
CPU-time: 1.1h
Number of CPUs: 256
Machine/ processor type: SGI Altix ICE at HLRN / Intel XEON Harpertown

For download see:
http://www.muk.uni-hannover.de/~maronga/animations.html#karman

Category:

Science & Technology

Tags:

• meteorology
• boundary layer
• atmospheric science
• Karman vortex