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FISTeC
(Interdepartmental Centre of Science and Technology
for Historical and Architectural Conservation)
has investigated thermofluid dynamics phenomena
inside Domus Aurea in Rome, to understand the
causes of decay of the ancient and precious mural
paintings (fig. 1). Domus Aurea was Emperor Nero's
residence (first century A.D) and is now  completely
below ground level. Based on previous studies
on several historical hypogeum monuments (e.g.
Hebrew Catacombs at Torlonia Villa in Rome, Catacombs
in Tarquinia), CISTeC defined the optimal conditions
for the conservation of paintings: air temperature:
17°C (± 2°C), relative humidity:
92% (± 5%), air velocity < 0.4 m/s.
With STAR-CD we studied the
microclimatic changes (e.g. wind velocity, air
temperature and its relative humidity) inside the
rooms of Domus Aurea and how they differed from
the above optimal values.
These simulations have been
supported by experimental monitoring of the environmental
parameters: air temperature, contact temperature
of the walls, relative humidity of the air, wind
velocity.
Simulations were especially
concerned with the so called "Room with the
Golden Vault" (fig.1), where openings in the
masonry produced turbulent air flow.
Geometrical
model of the room
The geometrical model of "Room
with the Golden Vault" is 1:1 scale, the volume
of air storage capacity is equivalent to 813.10 m3.
Environmental
data and boundaries
We chose the microclimatic
data for the months of January and August 2000, because
they are the coldest and hottest periods of the year
in Rome. In figure 2a the original case is shown with
environmental average conditions (measured parameters).
Other simulations of the original case were carried
out changing only the wind velocity: the maximum and
the minimum values of wind were chosen from the experimental
measurements.
Finally, simulations were repeated
using a modified condition where the openings in
the masonry were closed (fig. 2b). We will show
how this proposed modification brings potential
benefits.
Results
- August 2000
The three values of the inlet
for this month are: average=0.09 m/s, minimum=0.03
m/s, maximum=0.73 m/s. There are no significant differences
between the summer and winter cases for what concerns
fluidodynamic and thermo-hygrometric distributions.
It goes without saying that the absolute environmental
values change.
The minimum values of air wind
velocity is 0.26 m/s and the maximum value is 0.96
m/s.
The optimal value for the indoor
air velocity (0.4 m/s) was exceed only in the maximum
velocity case. In the other cases, the critical
zones are: vault, pillars and western wall (fig.
3a). In summer the temperature difference between
walls and air is lower than in winter. In summer
the difference is 0.5°C with air temperature
in the range 18.5 - 19 °C (fig. 3a), while
in winter the difference is 2.1°C with air
temperature in the range 7.6 - 9.7°C.
An isothermal profile of the
inflow air is shown in fig. 4. The hygrometrical
trend follows the winter case, but the specific
humidity value is double. The higher wet zones
are the north wall and the vault (fig. 5a). In
the modified case the microclimatic conditions
are better and close to the optimal values (fig.
5b).
Conclusion
In the original cases,
the simulations led to the following results:
The inflow air damages the masonry season in
both seasons, but for different reasons:
- In winter the
optimal value is never reached
- In summer optimal
temperatures are
achieved but the humidity is too high
In the modified masonry cases,
simulations show that:
- Microclimatic
parameters are distributed more homogeneously>
- The room is more
insulated from the external environment
It is therefore easier to reach
optimal values for air temperature and relative
humidity and so guarantee the conditions for the
conservation of the mural paintings.
"CISTec of Rome", says Anthony
Massobrio of CD-adapco(Turin Office), "is a leading
example on how to merge art and technology. What
archaeologists discover, CFD studies help to preserve."
Read more - www.architectureweek.com/2003/0924/tools_1-1.html
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