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qgisred / QGISRed

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Set Roughness Coefficient (From Materials and installDate) #35

Closed Mehdi-Ali closed 3 years ago

Mehdi-Ali commented 3 years ago

"Set Roughness Coefficient" is a very helpful function, what formula is it based on ? I searched everywhere and could not find it! Thank you so much for sharing your amazing plugin.

fmartine commented 3 years ago

We are using internally the assumption that the roughness coefficient e (Colebrook) increases linearly with time: e = eo + a t, being t the pipe age. Some values for eo and the slope a are assumed internally for different materials. I a coming version, both of them would be editable, and automatic conversion to C values and n values for H-W and C-M formulas will be done

Mehdi-Ali commented 3 years ago

Thank you for answering to my question, were the assumption of the "eo" and the "a" based on experiences and practical results or were it purely theoretical ?

fmartine commented 3 years ago

The hypothesis of the linear variation of roughness with time was first formulated by Colebroosk in 1937, and later confirmed by numerous experimental studies. The following reference: "Predicting Internal Roughness in Water Mains" by T. Walski, published in 1988 in the Journal AWWA confirm these results. You can download it from: https://www.researchgate.net/publication/235156580_Predicting_Internal_Roughness_in_Water_Mains . (see in particular fig. 1)

Mehdi-Ali commented 3 years ago

Thank you for your answers. Best regards.