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Hamid Fanaie

Flushing Study

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Hi all,

I need to do a flushing study, I want to fill an area of the interest with a tracer concentration equal to 1 and leave the rest of model domain concentration as 0.In addition I need to set the fall velocity equal to zero and let the hydrodynamic model move the tracer and disperse it.

Would you please advise what model is suitable for flushing study?

Any input on this issue is highly appreciated

Regards,

Hamid

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Hi,

Unfortunately, the model I would recommend is not distributed in the current version of SMS. It is the TUFLOW AD module of TUFLOW. It has the functionalities you need and is very robust. It doesn't suffer from numeric dispersion like other advection/dispersion codes. There will be an interface for this in the next version of SMS. It actually doesn't have a ton of extra inputs and it would be possible to setup by editing files outside of SMS. I could help explain how you could do the spatially varied concentrations (which would require creating an alternate type of file in SMS and modifying it). Contact sales if you are interested in this option and they can talk to me.

see http://www.tuflow.com/TUFLOW%20AD/TUFLOW_AD_Description.html

The other option is RMA4 which uses hydrodynamic output from RMA2. It can do conservative constituents and likely could handle your project (assuming you don't have lots and rapid wetting/drying which RMA2 doesn't handle particularly well). It does have more numeric(artificial) dispersion than TUFLOW AD. RMA4 is less expensive.

Cheers,

Rusty

Hi all,

I need to do a flushing study, I want to fill an area of the interest with a tracer concentration equal to 1 and leave the rest of model domain concentration as 0.In addition I need to set the fall velocity equal to zero and let the hydrodynamic model move the tracer and disperse it.

Would you please advise what model is suitable for flushing study?

Any input on this issue is highly appreciated

Regards,

Hamid

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Too many thanks Rusty,

I tried RMA4, and I found out what you mean, when I want to assign a concentration the unit is KG/m/s, so If I want to have just initial concentration in the specific time without further concentration adding to my model, I have to make it with some hot start runs. It would be a bit dogy to try to generate a specific initial concentration value at specific location with hotstarts. Is there any other way in RMA4 that I can manually assign the instantaneous initial concentration just to trace the flushing?

One would say that PTM engine may be the appropriate tool if they allow us to assign source for a 2D area with initial condition. Is it any way to define this problem in PTM?

Best regards,

Hamid

Edited by Hamid Fanaie

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I don't know of another way in RMA4 to manually assign the concentrations other than a gradual method described by the model, but this isn't what you want either.

PTM is a Lagrangian particle tracker meaning it tracks individual "parcels" through the domain. A parcel represents a specified mass of particles. You can compute concentrations based upon these parcels. I can't remember exactly how, but there is an option for neutrally boyant particles which won't fall to the sediment. I have heard of people using PTM to get a feel for flushing. All of the boundary conditions for PTM are defined in terms of mass of sediment. There is an area source that you can add mass to the model with. The units are kg/m^2/s so in the end you end up with a specific mass per time entering the simulation. I'm not quite sure if this is exactly what you want. Computing concentrations is a post-process that is done by calculating the parcels in a grid cell.

Feel free to contact our sales people if you would like to get a trial password to see if PTM will do what you would like. You could also try a trial version of TUFLOW AD and I'll help get you started if you would like. I really think it is the best tool for the job.

Cheers,

Rusty

Too many thanks Rusty,

I tried RMA4, and I found out what you mean, when I want to assign a concentration the unit is KG/m/s, so If I want to have just initial concentration in the specific time without further concentration adding to my model, I have to make it with some hot start runs. It would be a bit dogy to try to generate a initial specific concentration value at specific location with hotstarts. Is there any other way in RMA4 that I can manually assign the instantaneous initial concentration just to tracer the flushing?

One would say that PTM engine may be the appropriate tool if they allow us to assign source for a 2D area with initial condition. Is it any way to define this problem in PTM?

Best regards,

Hamid

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Is there any other way in RMA4 that I can manually assign the instantaneous initial concentration just to tracer the flushing?

Hamid,

To my understanding/experience you can assign intial concentration by element number (not by material or node, though). If your area of non-zero concentration is not very large (or if you find a way to easily get the element numbers - through materials perhaps - of the non-zero area), all you need to do is add them to your trn-file with notepad for example. You don't want to use decay, so use FQC 0.

Here's a simple test I did (with c=100)

...

TP 0 0 0 0 0 0

PE 1 5 0.1 1 1

FQC 0

ICE 113 100

ICE 114 100

ICE 110 100

ICE 107 100

ICE 224 100

ICE 223 100

ICN 217 100

END --- Time = 0.000, Step = 1.

END --- Time = 0.100, Step = 2.

...

post-25-127953961763_thumb.jpg

Edited by heimo

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Too many thanks Heimo,

That seems a smart way to do the job, I am out of my office for a week and do not have access to SMS dongle, but will definitely give it a try when I came back.

Best regards,

Hamid

Edited by Hamid Fanaie

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