[esp-r] Re: Problem with airflow network

[Aizaz Samuel]

The fixed pressure nodes are used in CFD-airflow network conflation, where 
each connection to the CFD domain node is replaced by a known pressure node 
(at the pressure of the CFD node at that time step).

-Aizaz

On Friday 10 July 2009 15:21, Jon Hand wrote:
> In a dozen years of creating flow networks I have never had an occasion to
> use a known fixed boundary type.  Boundary nodes are typically of type
> wind pressure driven for most users.
>
> Again, the design of flow networks is covered in the ESP-r Cookbook.  If
> someone has a really good use for fixed nodes then I would be happy to
> include it in the Cookbook.
>
> -Jon Hand
> ________________________________________
> From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk]
> On Behalf Of Liam O'Brien [obrien_liam at hotmail.com] Sent: 10 July 2009
> 14:15
> To: esp-r at lists.strath.ac.uk
> Subject: [esp-r] Re: Problem with airflow network
>
> Thanks, Jon and Monika.  Does the "known: boundary" type of node not count
> as a boundary node?  I specified its ambient temerpature and pressure as
> 20C and 0 Pa, repsectively.  Both unknown [zonal] nodes have connections to
> this node.
>
> Liam
>
> > From: jon at esru.strath.ac.uk
> > To: obrien_liam at hotmail.com; esp-r at lists.strath.ac.uk
> > Date: Fri, 10 Jul 2009 08:14:27 +0100
> > Subject: [esp-r] Re: Problem with airflow network
> >
> >
> > It is essential that there be at least one connection to a boundary node.
> > The solver really needs this rule to be followed.
> >
> > For more information on defining air flow networks there is a chapter in
> > the current version of the ESP-r Cookbook (ESRU web page -> software
> > downloads -> esp-r -> beginners guide
> >
> > -Jon Hand
> > ________________________________________
> > From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk]
> > On Behalf Of Liam O'Brien [obrien_liam at hotmail.com] Sent: 09 July 2009
> > 20:24
> > To: esp-r at lists.strath.ac.uk
> > Subject: [esp-r] Problem with airflow network
> >
> > Hello everyone,
> >
> > I'm setting up a fairly rudimentary airflow network, in which two zone
> > air nodes exchange air with a third node that is intended to mix the air
> > and send it back to the nodes. A fixed volume rate component moves the
> > air. The "mixing" node was assigned to known boundary conditions of P=0
> > Pa, T=20C. However, after several tries, I continue to get the following
> > message for each timestep:
> >
> > Please check (in the following order) that:
> > - each node has some flow path to a boundary pressure and
> > - iteration convergence control is not too strict.
> > Day 2 Month 1 Hour 24.000: 100 iterations; flows solution failed
> >
> > I assume the first issue is triggering the message. I would have thought
> > that having the mixing node at known conditions would alleviate this
> > error.
> >
> > Any thoughts? (I realize this could be accomplished in the operations
> > file, but I want something more sophisticated eventually.)
> >
> > The afn file is below.
> >
> > Thanks very much!
> >
> > Liam O'Brien
> >
> > ----------------
> >
> > 3 1 4 1.000 (nodes, components, connections, wind reduction)
> > Node Fld. Type Height Temperature Data_1 Data_2
> > south 1 0 2.5000 20.000 0.0000 250.01
> > north 1 0 2.5000 20.000 0.0000 250.01
> > Mixing 1 2 20.000 0.0000 0.0000 2.0000
> > Component Type C+ L+ Description
> > Circulation 30 2 0 Constant vol. flow rate component m = rho.a
> > 1. 0.200000003
> > +Node dHght -Node dHght via Component
> > south 8.750 Mixing -8.750 Circulation
> > north 8.750 Mixing -8.750 Circulation
> > Mixing -8.750 south 8.750 Circulation
> > Mixing -8.750 north 8.750 Circulation
> >
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-- 
Dr Aizaz A Samuel
Research Fellow
Department of Mechanical Engineering
University of Strathclyde
M324 James Weir Building
75 Montrose Street
Glasgow, UK
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