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Alphawater go down abruptly to a small number

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Old   May 7, 2020, 06:00
Default Alphawater go down abruptly to a small number
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Hi Foamers,

I am about to use interFoam for mudflow simulations using Herschel-Bulkley rheology. prior to my main job, I am simulating the conventional 3d dambreak by only changing the rheology of the fluid and assuming laminar flow. When I do simulate by varying the parameters tau0 and k, for certain combination of these parameters, I am facing this problem:

- After certain time step the fluid with alphawater=1.0 is disappearing. At some point of time alpha always go down abruptly to a very small number (order of 1.0e-5 even lower).
- I can't understand the physical implication. Does this have anything with my mesh size?
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Old   May 12, 2020, 14:05
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Hi,

- Have you correctly inspect the values? Have you inspected them visually?
- Why do you think the value would be problematic?
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Old   May 13, 2020, 13:17
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Thank you HPE,

For my case I used a 6 degree inclined flume of length 4m, width 1m and height 1m with a Herschel bulkley fluid of tau0 =0.01, k =9.6e-3, n=0.34 and rho =1350. The dam size was 1mx1mx0.5m. The grid size was 50mm. After running interFoam and visualizing taking the free surface at alphawater=0.5( Contour at alphawater =0.5), it went as normal as the dambreak tutorial for newtonian fluids until the simulation time is 0.4 seconds. Afterwards the fluid disappeared from the flume. I tried to to inspect the results and the alphawater range was between 0.0 to 1.0 until t =0.4 seconds. After that the range went to 0.0 to 1.0e-16 just after t =0.41. I did not know why?


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What I was expecting was the flow would continue until the applied shear stress due to the weight of the fluid is less than tau0 (yield stress).
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