[swanmodel-users] 3. Interpreting SPECOUT results (Morgan Stephenson)

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Hi Morgan,

The formula you give
H=sqrt(8*E*factor*abs(direction1-direction2)*abs(frequency1-frequency2)).
is for Hrms, not Hm0.
Hm0=sqrt(2)*Hrms, so your values should be smaller rather than larger.

Regards,

Jim Gunson

CSIRO Marine and Atmospheric Research
Street address: Underwood Ave, Floreat Park, WA 6014
Postal address: Private Bag #5, Wembley, WA 6913
Ph: 61 8 93336511
Fax: 61 8 93336555
email: jim...@cs...

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Sent: Thursday, 23 June 2011 12:06 AM
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Subject: swanmodel-users Digest, Vol 5, Issue 5

Message: 3
Date: Tue, 21 Jun 2011 14:13:08 -1000
From: Morgan Stephenson <mst...@se...>
Subject: [swanmodel-users] Interpreting SPECOUT results
To: swa...@li...
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Dear all,

I am working on a SWAN model set up to run a hindcast model.  The model
outputs TABLE and SPECOUT for energy density.  The model has successfully
run but I am unsure how to interpret the results for the SPECOUT file.  I
have a couple questions that need clarifying but any help would be greatly
appreciated.

The first thing I'm trying to do is to convert the the energy density to a
wave height.  Currently I'm using the following formula to convert a point
in the output matrix, E, with units of m^2/Hz/deg:
H=sqrt(8*E*factor*abs(direction1-direction2)*abs(frequency1-frequency2)).

If I sum all of these values I get a significantly larger value than the
results for the significant wave height the same time period listed in the
TABLE output, which leads me to my second question. Does anyone know how to
get Hm0 for a direction band from the spectral data?  I've tried using the area
under the frequency/energy density plot as the Hmo, however I think I'm
missing some sort of conversion factor other than the one given by the SWAN
output.

Regards,
Morgan Stephenson
Sea Engineering Inc.
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Message: 4
Date: Wed, 22 Jun 2011 11:56:42 +0100
From: Alexandros Adam <A.A...@sm...>
Subject: [swanmodel-users] Bathymetric Data
To: swa...@li...
Message-ID: <201...@ww...>
Content-Type: text/plain;	charset=ISO-8859-1;	DelSp="Yes";
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Dear all,

I am using SWAN for my dissertation and I would really appreciate it
if you could answer some of my questions.

1. I used Battri to generate my mesh and all seem to work well except for
the bathymetric data. Since I want to use the linearly interpolated
data (generated by Battri)  I created a file with x y z information where x is
the longitude, y the latitude and z the bottom level. When however I
ask SWAN the BOTLEV output, it is clear that the bathymetric data are  
not inserted in a correct way. What would be the correct format to  
insert an unstructured bathymetry mesh?

INPgrid BOTtom UNSTRUCtured
READinp BOTtom 1 'Alex.bot' FREE

2. In the output I ask SWAN to give me values at specific points.  
Since however my data were transformed from longitude, latitude to km  
and I am working with a big space domain (~600x600km) my nodes have a  
lot of decimal points:

1	-114304.5464	-41179.46261
2	-113951.9021	-41372.96344

When I request an output at the first point, however, the value becomes:

-114300 -41180

Is this truncation just in the output, or will the actual results be  
interpolated in the truncated values. If the case of the latter is  
there a way to increase the arithmetic accuracy?

Thank you in advance,
Alexandros

-- 
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.

------------------------------

Message: 5
Date: Wed, 22 Jun 2011 09:05:12 -0700
From: Clayton Hiles <ce...@gm...>
Subject: Re: [swanmodel-users] Bathymetric Data
To: Alexandros Adam <A.A...@sm...>
Cc: swa...@li...
Message-ID: <BAN...@ma...>
Content-Type: text/plain; charset="iso-8859-1"

Hi Alexandros, I'll attempt to answer your questions.

1) The bottom file should contain only depth values listed in the exact same
order as the nodes in the .node file.  I have only used BatTri a little, but
it did not seem to produce such a file.  That said, it is easy enough to get
Matlab to write out the appropriate data.

2) I do not believe that SWAN can work in coordinate units of killometres.
 Either perform calculation in spherical coordinates or change your grid to
meters.   If working in meters, any decimal loss in precision should
be inconsequential.  I believe the loss in precision is only due to the
write format.  I have never attempted it, but you should be able to change
the format in the source code.

Hope that helps,

Clayton Hiles
Triton Consultants Ltd.

On 22 June 2011 03:56, Alexandros Adam <A.A...@sm...> wrote:

> Dear all,
>
> I am using SWAN for my dissertation and I would really appreciate it
> if you could answer some of my questions.
>
> 1. I used Battri to generate my mesh and all seem to work well except for
> the bathymetric data. Since I want to use the linearly interpolated
> data (generated by Battri)  I created a file with x y z information where x
> is
> the longitude, y the latitude and z the bottom level. When however I
> ask SWAN the BOTLEV output, it is clear that the bathymetric data are
> not inserted in a correct way. What would be the correct format to
> insert an unstructured bathymetry mesh?
>
> INPgrid BOTtom UNSTRUCtured
> READinp BOTtom 1 'Alex.bot' FREE
>
> 2. In the output I ask SWAN to give me values at specific points.
> Since however my data were transformed from longitude, latitude to km
> and I am working with a big space domain (~600x600km) my nodes have a
> lot of decimal points:
>
> 1       -114304.5464    -41179.46261
> 2       -113951.9021    -41372.96344
>
> When I request an output at the first point, however, the value becomes:
>
> -114300 -41180
>
> Is this truncation just in the output, or will the actual results be
> interpolated in the truncated values. If the case of the latter is
> there a way to increase the arithmetic accuracy?
>
> Thank you in advance,
> Alexandros
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
>
>
>
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