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Dylan8

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  1. Hi everyone, I am currently doing a project regarding in-situ chemical oxidation of BTEX using persulfate solution, and trying to use RT3D to represent the process. As reading the literature the reaction should be a pseudo 1st-order kinetic reaction model, but the only relevant option I found in the reaction package is the inst. aerobic degradation of BTEX which only offers oxygen as the electron acceptor. In this case, could someone familiar with the persulfate or other similar oxidation mechanisms tell how to construct the RT3D model? convert the persulfate concentration to an equivalent oxygen concentration? or should I try more options other than MODFLOW? Regards Dylan
  2. Hi all, I have come up with some errors when running the tute model of TUTE: MODFLOW – Generating Data from Solids that indicate “changing heads are below the bottom of cell xxx". It is so weird that a tute brings up a problem like this. Having read a thread in the forum suggesting to remove the BC of constant heads from the sources sinks coverage, I found many cells dry out with red triangular flags after a modflow run. I knew it was different from what is instructed in the tute sheet, but it seems plausible for me that without those BC these cells could dry out. A further question is, i was constructing a more complex multi-layer solids model and tried to convert to modflow. My BCs are constant heads set on the arc of the coverage boundary, kind of surrounding my small catchment of interest, and they are definitely all below the bottom of my first, second and part of the third layer, so how to define the default layer range? (i.e. from 1 to 1, 3 to 12 as I have 12 layers in total, or 1 to 12?). PS: in this coverage I define wells, specific head, layer range for source sink and layer range for areal properties, and tick used for BC option. The first trial I have set was 1 to 12 (dont know if appropriate), converted map to modflow, and could see the blue dots assigned from layer1 to 12 of my conceptual model. All of them indicate the some heads I define in the coverage. (Really? Does it have to be a 58 m head in the even very bottom of my rock layer of 30 m elevation?). As expected, the model warned that lots of heads were below cells' bottom. When removing all of them in sources sinks and running the model in steady state, I found it never converge. A feeling was that I did it wrong when defining BCs. This is where I got confused. Could anyone kindly help? I am using GMS Version 10.0 Thanks for any help Rgds Dylan
  3. Just came up with a question regarding where to apply different solution schemes for the advection package activated in the MT3D or RT3D model, and the cases are based on the tutorials 1. Can someone please explain further why we choose the Standard finite difference method for both the Sequential anaerobic degradation and BTEX degradation with multiple electron acceptors, MMOC for the Rate-limited sorption reaction, MOC for both Instantaneous aerobic degradation and Double-Monod model, 3rd order TVD (ULTIMATE) for all MT3D tutorial cases, etc. If there were relevant recommended reading resources, that would be greater. 2. In the Rate-limited sorption reaction tute, what is the meaning of changing Max. number of cells any particle will be allowed to move per transport step to 2 in the Particle dialog of the Advection package? 3. How to save multiple solutions as a .rts file like what it supposed to import in the Rate-limited sorption reaction tute. Because each time I ran the model it would overwrite the existing solution with a new solution of both Aqueous and Soil given a certain mass transfer coefficient. How to come up with a solution with different runs (i.e. different mass transfer coef in one solution file? Thanks, Dylan
  4. I am a junior learner running through the general tutorials of MODFLOW, GMS and have come up with some confusion relating to the steps. 1. What happen to the right part of zone 3 with a constant recharge rate when importing csv file automatically matching zone name? The other zones are assigned correctly except for this part of zone 3. 2. In the tutorial it states the stress periods should match three changing point of recharge rate, i.e. 1/1/1986, 1/3/1986, 1/7/1986 (actually it is four including 1/10/1986). What is the purpose to set 1/5/1986, 1/6/1986 and 1/9/1986 etc. since no change takes place at these time? In addition, this should assume all the recharge polygons have the same changing points of rate over the space, so what if we have different change in time of these zones, say 1/3/1986 for zone 2 and 1/4/1986 for zone 3 etc. How to set stress periods for this scenario?
  5. Steady State vs. Transient

    Hi there, can you specify what the length of your each stress period and what the magnitudes of recharge rate are for each? Also the information of your steady state simulation. In addition, is your landfill site covered by a confined or unconfined aquifer beneath? Because I would like to try to interpret your problem theoretically assuming that your settings were perfect. Of course you are welcome to find any model setting workaround if that is the case. Cheers!
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