Large-Eddy Simulation #141: Upwind Wall Experiment
LES RUN #125: Upwind Wall Experiment. This simulation was an
experiment to determine if we could perturb the "prescribed inflow
wall" randomly and in order to quickly generate large-eddies just
downstream of it. To do this, the domain was 50 x 50 x 69 with
dx=dy=dz=15. It was initialized horizontally homogeneous with a
radiosonde sounding from the Sheboygan ISS during Lake-ICE on this
morning of 13 Jan 98. Click here to see the NMSTASK file. This domain is 750 m
(east-west) by 750 m (north-south) wide by 1.0 km tall and all over
land with a roughness length of 10 cm. The flow is from the NW with a
400 m deep mixed layer. Radiation in the model is turned off and there
is no surface heat flux. The west wall is a floating, prescribed inflow;
the east wall is radiative outflow, and the north and south wall are cyclic.
Only the v-component of flow was randomly perturbed by + or -
0.5 m/s on each 1/2-s timestep along the west wall below 400 m. The
results show the high-frequency noise quickly becoming correlated on
the wall and the resulting roll-like structures immediately downwind of
it. The movie is for 159 frames long (1-min and 39 s) and the time
interval between frames is 0.5 s. One possible theory for coalesence
of the eddies on the west wall is that the wall is a 2-D model. This
prevents vortex tube stretching and larger scale structures grow on
it.
UW Lidar // Oct 10, 1999 // root@lidar.ssec.wisc.edu
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