Post on 10-Sep-2020
Michael Schatzmann
Title
Lecturegiven in honour
of Ian Castro‘s
65th Birthday
SouthamptonMarch 28/29, 2012
Michael Schatzmann
Title
Michael Schatzmann, Bernd Leitl, Denise Hertwig, Frank HarmsMeteorological Institute, KlimaCampus, University of Hamburg
Susanne Fischer, Peer RechenbachMinistry of the Interior, State of Hamburg
Gopal Patnaik, Jay BorisNaval Research Laboratory, Washington DC
Pilot Project Hamburg, sponsored by the Federal Office of Civil Protection and Disaster Assistance and the Parliament of the State of Hamburg, Germany
LES for Accidental Releases
Michael Schatzmann
‚Urban‘ Roughness 1
Packing density λp = 0.25 Frontal area density λf = 0.25hc = 125mm, w/hc = 1
59 rows with 11 cubes each
x = 0 between rows 46 and 47,
y=0 at center lineof the tunnel
(Schultz, 2008)
Starting Point: Cheng, H. & Castro, I. P. , BLM 104, 2002
Michael Schatzmann
‚Urban‘ Roughness 2
Packing density λp = 0.25 Frontal area density λf = 0.32
X [mm]
-750 -625 -500 -375 -250 -125 0 125 250 375 500
Y[m
m]
-625
-500
-375
-250
-125
0
125
250
375
500
625
Z[m
m]
062.5125
187.5
Y
X
Z
ha = 156.25 mm, w/ha = 0.8
(Schultz, 2008)
Michael Schatzmann
‚Urban‘ Roughness 3
Packing density λp = 0.25 Frontal area density λf = 0.32
X [m m ]
- 7 5 0 - 6 2 5 - 5 0 0 - 3 7 5 - 2 5 0 - 1 2 5 0 1 2 5 2 5 0 3 7 5 5 0 0
Y[m
m]
- 6 2 5
- 5 0 0
- 3 7 5
- 2 5 0
- 1 2 5
0
1 2 5
2 5 0
3 7 5
5 0 0
6 2 5
Z[m
m]
06 2 .51 2 5
1 8 7 .5
Y
X
Z
ha = 156.25 mm, w/ha = 0.8
‚Urban‘ Roughness 4
Michel-Stadt(John Doe‘s Town)
Michael Schatzmann
Motivation
The majority of accidental release models considers mean flow and concentration fields only
Obstacles are not properly taken into account
Transient phenomena like plume meandering are usually neglected
New and innovative approaches are available now. They can significantly improve the situation.
Michael Schatzmann
The New Approach
The US Naval Research Laboratory and Hamburg University developed a new and advanced Emergency management system for the City of Hamburg.
The new emergency management tool is based on two NRL models; (1)a Large Eddy Simulation model and (2)a tool for the rapid display of the results.
Wind tunnel and field experiments were carried out in order to validate the system.
CT-Analyst Presentation
The steps towards realizing the new emergency management tool were:
Features of the New Approach
Michael Schatzmann
Features of the New Approach
1. Select appropriate domains: 16km x 12 km 4km x 4 km
Michael Schatzmann
Features of the New Approach
Geometrical complexity of the 4km x 4 km site
Michael Schatzmann
Features of the New Approach
2. Select an appropriate model and grid:LES –Model “FAST3D-CT”
Domain4km x 4 km with 2.5mresolution
Domain16km x 12 km
with 10mresolution
Michael Schatzmann
Content of the New Approach
3. Do the simulations for x wind directions and y stabilities, scale the results:
Resolution in both cases results in
≈ 210 million cells
≈ 20 GB of memory
time step: ≈ 0.05 s1 h ≈ 6 d
on a 64 CPU
SGI Altix computer
Michael Schatzmann
Features of the New Approach
4. Transfer the results into a data structure which can be read by the display tool “CT – Analyst”:
Data are transferred from FAST3D to CT-Analyst in Form of so-called Nomograf- tables which contain for each grid point the time series of the instantaneous wind vector.
CT-Analyst runs on a LapTop and comes with anuser-friendly interface as common in computer games.
CT-Analyst is fast because it displays pre-computedresults. CT-Analyst only extends these results to all wind directions and wind speeds.
Michael Schatzmann
Content of the New Approach
5. Select a source position. The plume edges are derived from the mean and turbulent flow field as computed by the LES model
6. Assume a plume profile and estimate mean and peak concentrations by applying the mass conservation principle
Michael Schatzmann
Validation of the New Approach
7. Validate the LES-model FAST3D and the emergency management system CT – Analyst:
A: Field Experiments
B: Wind Tunnel Experiments
Validation of the New Approach
Smoke Visualisation and Dispersion Experiments
Michael Schatzmann
Validation of the New Approach
Concentration Measurements:
Measurement Positions
Source
220°
6745 ppt
180 ppt
638 ppt
1716 ppt
73 ppt
501 ppt
591 ppt
Maximal Measured ConcentrationsSF6 Release Rate : 2 g/s
Experiment 2
Michael Schatzmann
Validation of the New Approach
7. Validate the LES-model FAST3D and the emergency management system CT – Analyst:
B: Wind Tunnel Experiments
Michael Schatzmann
Hamburg University‘s Wind Tunnel ‘WOTAN’
Michael Schatzmann
Validation of the New Approach
Wind Tunnel Experiments:
Model Scale: 1:350
Model Size: 1.4km x 3.7km
Wind Direction: 235° (WSW)
Wind Tunnel Measurements:
The Hamburg Radio Transmitter Tower
Time series measured at
different heightsare analysed.
The information is used to generate a proper wind
tunnel boundary layer in the
model scale of 1:350
Michael Schatzmann
Validation of the New Approach
Wind Tunnel Experiments:
Non-intrusivemeasurements of time series
of the wind velocity vector
in a dense array of points
Flow Measurements using LDA:
Release Locations
Wind Tunnel Experiments
Baumwall
z = 3.5m
approach flow
Wind Tunnel Experiments
Ground Level Wind Field within the Canopy Layer
3.5m
approach flow
z = 3.5mAromahaus
Wind Tunnel Experiments
Ground Level Wind Field within the Canopy Layer
Spatial and Temporal Variability of the Wind
2.5m
21m
33m 57m
Wind Tunnel Experiments
Michael Schatzmann
Wind Tunnel Experiments:
Flow visualization and measurement
of concentrationtime series
for many sources at a dense array of receptor points
Concentration Measurements using Fast FID:
Wind Tunnel Experiments
kontinuierliche Freisetzung
Wind Tunnel Experiments
Continuous Release
Wind Tunnel Experiments
Wind Tunnel Experiments
Continuous Release
235°
Gas erreicht Messort nicht
Gas erreicht Messort
Wind Tunnel Experiments
Determination of the Cloud Edges
Instantaneous Release
Wind Tunnel Experiments
Wind Tunnel Experiments
Instantaneous Release
235°Instantaneous Release
Wind Tunnel Experiments
Ian, go on and continue your community-inspiring work