KH Data for Radar Backscatter Simulations
The latest data for the radar backscatter simulations is a collection of 10
64-element time series of velocity and temperature fields, taken at various
times during the evolution of a Re=10,000, Ri=0.05 KH billow. The movie
and table below show the overall evolution of the vorticity during the
simulation as well at the 10 times selected for the individual time series.
The simulation was performed on a 720X240X1440 mesh and a subgrid-scale
turbulence model was used to account for the very small scales that are not
resolved in the simulation.
The computed Reynolds number will match a shear layer of thickness
D = 6*L = 6*150 = 900 m, with a velocity jump of 2*Uo = 2*5 = 10 m/sec, at an
altitude of 63.25 km. Here L is the length scale used in the simulation,
which is the characteristic half-width of the eigenfunction that initiates
the turbulence and Uo is half the velocity jump. The normalizing parameters
for the simulation are L and Uo and thus the Reynolds number is
defined as Re = Uo*L/nu where nu is the kinematic viscosity. D is the
full width of the layer during the turbulent phase, which is roughly 6*L.
These dimensions will be used below to assign physical dimensions to the
simulation data. It is important to note that other dimensions can be used,
with the only constraint being that the Reynolds number formed from these
dimensions equals 10,000. Layers at lower altitudes (smaller viscosities)
will require fairly substantial reductions in the layer thickness and/or
the velocity jump in order to continue to match the Reynolds number.
The computational domain is 12.566L X 4.2L X 25L in the streamwise, lateral,
and vertical directions respectively. The corresponding mesh spacings are
2.618m X 2.625m X 2.604m.
Each times series contains 64 frames of velocity and temperature fields,
each separated by 1.5 sec. The data is archived on the DMS at ERDC on the
path /erdc1/lund/KH/les/720X240X1440/radar10/run##/vel, where ## is replaced
by 01, 02, 03, etc. The data is also currently on line on the work
disk attached to sapphire on the path /work/lund/KH/les/720X240X1440/radar10/run##/vel.
Please recall that the data themselves are written out in non-dimensional
form. Velocities are normalized by Uo=5 m/s (half the velocity jump) and
lengths are normalized by L=150 m (characteristic half-width of the initial
condition eigenfunction, the entire shear layer width is about 6*L=900 m).
Potential temperature is normalized by its background gradient and L. The
Richardson number is 0.05, the maximum background velocity gradient is
1*(Uo/L), and thus the buoyancy period is
2*pi/sqrt(Ri) = 28.1*(L/Uo) = 843 sec. The 64 frames span 64*1.5=96s,
or 0.114 buoyancy periods.
Vorticity, Side view on left, Top view on right
Click on the image to start the the movie
Case
| Starting Time
(in units of L/Uo) |
|---|
| run01 | 37.32 |
| run02 | 54.32 |
| run03 | 68.58 |
| run04 | 84.16 |
| run05 | 112.44 |
| run06 | 129.16 |
| run07 | 189.66 |
| run08 | 255.67 |
| run09 | 312.15 |
| run10 | 364.03 |