[esp-r] Re: [ESP-r] issues regarding air flow network and CFD

[Jon Hand]

Questions about air flow and CFD

Information about the equations used in the flow network are available
in a PhD thesis by Jan Hensen (look on the ESRU web site) and the source
code has lots of commentary as well as the actual equations in the
code.

ESP-r simulation is based on the domains that have been defined. If
you have a CFD domain defined in the model you will get the CFD
solver along with the other relevant domains.  If you do not want
the CFD solution you should remove references to the CFD domain
from your model configuration file.

Cp values can be derived from many sources - some people prefer
wind tunnel tests, others prefer to create a CFD model of the site
and run it with wind from different directions.  There is also a
web based tool from a University in The Netherlands which can
be used to evaluate Cp values for certain building types.

-Jon Hand
________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of Liu Pei-Chun [laxpcl at nottingham.ac.uk]
Sent: 30 October 2009 13:48
To: esp-r at lists.strath.ac.uk
Subject: [esp-r]  [ESP-r] issues regarding air flow network and CFD

Dear ESP-r users,

I am now operating ESP-r in the windows XP. My issues are as follows:

Firstly, the Cp database within ESP-r is proposed to be used for low-rise buildings (up to 3 storeys). If my modelling case is placed in the 8th level above the ground which means the node height is about 30m. I wonder how the Cp value is calculated.
Secondly, the ESP-r cookbook suggests that it’s better to place a boundary node at the height of each opening to the outside. If nodes and connections are at different heights, then the pressure difference will also include stack effects. My case is that I set the connection height the same as the boundary node and is lower than the internal node (0.8m). The results showed that the neutral pressure difference at connection shift to 10 pa while the stack pressure at connection is zero and the zero heat gain is applied. I would like to know where can I find more information regarding the equations used in the airflow network calculation?
Finally, I try to use the CFD module within ESP-r. I found that once I defined the .dfd file in the modelling case, the simulation will run the CFD even I choose not to activate CFD during the simulation.  I wonder if something wrong with the program or it is due to my operation system.

Regards,
Pei-Chun (Ingrid), Liu


PhD Student
Sustainable Research Building
School of the Built Environment
University of Nottingham
NG7 2RD


Tel: +44 (0)115 84 67262
Email: laxpcl at nottingham.ac.uk


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