how set a vertical discharge?

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mariafattorini
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how set a vertical discharge?

#1 Post by mariafattorini » Wed Jan 13, 2010 10:16 pm

Hello,

I need an advice:
I have to define a discharge characterized by zero horizontal velocity (v=u=0m/s) and vertical velocity of 2m/s toward the bottom (w=-2m/s). How can I set this case?
In the ana_psource.h it is possible set only u- or v- velocity components; is there nothing for w- vertical component?

thank you very much for any help,
maria

mariafattorini
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Re: how set a vertical discharge?

#2 Post by mariafattorini » Sun Jan 17, 2010 10:08 pm

Dear all,

I'm wondering if I can use roms in order to simulate the heat exchange between the ambient sea water and a costant discharge of cold water that is released at a point -10 m below the free surface and is downward directed (i.e. the horizontal velocity components are zero but there is a vertical velocity related to the discharge).

Can I use the point-source technique, setting the Q_PSOURCE option (with TS_PSOURCE), or is this specially suited only for river runoff?

Thank you very much,
Maria

zhaoqian
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Re: how set a vertical discharge?

#3 Post by zhaoqian » Mon Jan 18, 2010 8:06 am

I think you can active Q_PSOURCE and TS_PSOURCE and set Qbar、Qsrc and Tsrc in ana_psource.h file.

The ana_psource.h file can not only sets the imformation for T&S, but can set the imformation for other tracers.

mariafattorini
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Re: how set a vertical discharge?

#4 Post by mariafattorini » Mon Jan 18, 2010 3:14 pm

Dear all and thank you zhaoqian,

still concerning the Q_PSOURCE option, I just noted the post at the page "viewtopic.php?f=31&t=867&hilit=point+source", where jcwarner pointed out that, althought Q_PSOURCE is actually a vertical source term (see also http://www.myroms.org/Workshops/ROMS200 ... cripps.ppt), it was under construction at April 2008.

Is Q_PSOURCE option working at present?

If yes, how has the ANA_PSOURCE fragmetn related to Q_PSOURCE to be settled? I am sorry but, reading the ANA file I have find only examples concerning the setting for UV_SOURCE case. Can you help me?

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jivica
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Re: how set a vertical discharge?

#5 Post by jivica » Tue Jan 19, 2010 6:53 am

Be careful, the last time I used it was not working properly. Application was: Q_SOURCE with sediments and after when all sediment was on the bottom there was no mass conservation. On the other hand while using UV_ there it was exactly. Do some tests to see if it is working OK, the code was running (!) but results were basically wrong!!

Cheers,
Ivica

zhaoqian
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Re: how set a vertical discharge?

#6 Post by zhaoqian » Wed Jan 20, 2010 1:06 am

[img]d:\result.jpg[/img]

mariafattorini
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Re: how set a vertical discharge?

#7 Post by mariafattorini » Wed Jan 20, 2010 11:08 am

Thank you for your replies.

I am studing a submerged downward cold sea water jet. The jet comes from a port of diameter=1.9m that is located at 12m under the free surface.

I used the Q_PSOURCE and TS_PSOURCE options.
I set a horizontal grid spacing of about 1.7m in x and y directions, then, in the ana_psource file, I set only a point source (at i=12,j=25). Qsrc equal to 3 m3/s has been imposet just at the vertical level
k=2 (0 elsewhere).

Once the velocity field has reached the stationary regime, I noted that the vertical velocity w at the point source is about 2.5 m/s. Why it is so different from the value Qsrc/(dx*dy)=1 m/s?

Many thanks for any help,
Maria

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jivica
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Re: how set a vertical discharge?

#8 Post by jivica » Thu Jan 21, 2010 12:53 am

Well be sure that you know what are the limits of the model that you use...
In your example you have vertical velocities order of m/s which is comparable with horizontal ones....
hydrostatic/non-hydrostatic models?
From my experience I use "near-field model" for close to the source dynamics and after I put the "near-field" solution into
"far-field" model like ROMS....
But it is up to you...

Cheers,
Ivica

mariafattorini
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Re: how set a vertical discharge?

#9 Post by mariafattorini » Thu Jan 28, 2010 9:04 am

Hello jivica,

of course I agree what you noted.

In other words,if the horizontal velocity field is zero (i.e. the ambient water is at rest) ROMS can not simulate any vertical source point. Is it correct?
In priciple any vertical velocity (let say acceleration) violate the hydrostatic assumption but I believe that, since the ROMS developers have included Q_PSOURCE, it can "sustain" at least small vertical velocity values.

However, in order to redure the vertical velocity values, related to my problems, I simulated the "near-field" using EPA-VP and after I put the obtained plume discharge (corresponding to 0.03 m/s where the grid spacing is about 10m) and temperature into "far-field" modeled using ROMS.
I'm still frustrated about roms results related to the Q-PSOURCE option. Still the velocity field is not realistic since values about 0.16m/s are present at 20 m far from the source and near the bottom there are values close to value of the source.
Is this source velocity still too high for roms? Consider that the horizontal velocity is about zero in my model.

Moreover, I wonder if the source points have to be placed close to a land value or it can be placed inside a fluide domain.

Thank you again,
maria

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