Understanding behavior of tanks

Hello Alessandro, 

How much flow from the incoming flow will be stored in tank depends upon tank capacity like tank diameter, initial level, maximum level of tank etc. By changing diameter do you mean you are changing diameter of tank, this will increase of decrease storing capacity of the tank. 

And flow going out of the tank will depend upon total downstream demands at the junctions / customer meters that tank needs to supply. 

If this doesn't help then you may upload model files for our review. 

Sharing model files.

Hi Sushma, thanks for the answer. My question is why there is an extreme flow incoming to tanks like "R-SL02", "C-SC05" and "R-LM04", for example. When I said that I changed the diameter it means the upstream's pipes from tanks. In the moment that I changed the diameter more flow is required, causing a big headloss. In cases like tank R-SL01 there is an absurd flow incoming and such small flow going out to this tank. It's because the elevation difference or the initial level of tanks? I am not understand this behavior. I would like to know how it works on WaterGems.

Thanks!

Here is the link to download the file (I couldn't upload here)

https://we.tl/t-fSNd7J3AcA

Hi Alessandro,

You only provided the .SQLITE file, so I do not know what units you used (I assumed SI) or what scenario you were looking at (I assumed "Melhorias 2020") since that information is stored in the .WTG file.

For R-SL02 - there is a single pipe between this tank and tank R-SL01. When one of the tanks is higher than the other, the flow in that pipe will be the flow needed to induce a headloss equal to the difference in hydraulic grade between the tanks. In the copy of the model you provided, R-SL01 is at an initial elevation of 209.17 m and R-SL02 is at an initial elevation of 121.43 m. This means you are telling the model that there must be a drop (headloss) of 87.74 m (the difference) from R-SL01 down to R-SL02 in order for those two initial elevations to be true, so the model solve the flow around that - 63 L/s. This is the flow needed for a headloss of 287.86 ft in a 145 mm, 978 m long pipe with a roughness coefficient of 133. 

So, if you were to increase the diameter for example, while keeping the two tank initial elevations the same, then there would be a higher flow needed to induce the same headloss, which is why you see the flow increase.

The outflow of tank R-SL02 (1.24 L/s) is based on the sum of the downstream demands (1.24 L/s) since there are only demands downstream and no other boundary conditions (tanks or reservoirs).

For an EPS, this situation may be problematic, as oscillation can occur between timesteps - read more about that here: Rapid flow oscillation between hydraulically close tanks

For C-SC05 - in the model you provided, I only see an inflow of 4 L/s. Please clarify what you are seeing and what your specific concerns are in this area.

For R-LM04 - in the model you provided, I only see an inflow of 6 L/s. The inflow in this case is based mostly on the upstream tank R-NB02, which is at a higher elevation (85 m vs. 69 m). 

Hi Alessandro,

You only provided the .SQLITE file, so I do not know what units you used (I assumed SI) or what scenario you were looking at (I assumed "Melhorias 2020") since that information is stored in the .WTG file.

For R-SL02 - there is a single pipe between this tank and tank R-SL01. When one of the tanks is higher than the other, the flow in that pipe will be the flow needed to induce a headloss equal to the difference in hydraulic grade between the tanks. In the copy of the model you provided, R-SL01 is at an initial elevation of 209.17 m and R-SL02 is at an initial elevation of 121.43 m. This means you are telling the model that there must be a drop (headloss) of 87.74 m (the difference) from R-SL01 down to R-SL02 in order for those two initial elevations to be true, so the model solve the flow around that - 63 L/s. This is the flow needed for a headloss of 287.86 ft in a 145 mm, 978 m long pipe with a roughness coefficient of 133. 

So, if you were to increase the diameter for example, while keeping the two tank initial elevations the same, then there would be a higher flow needed to induce the same headloss, which is why you see the flow increase.

The outflow of tank R-SL02 (1.24 L/s) is based on the sum of the downstream demands (1.24 L/s) since there are only demands downstream and no other boundary conditions (tanks or reservoirs).

For an EPS, this situation may be problematic, as oscillation can occur between timesteps - read more about that here: Rapid flow oscillation between hydraulically close tanks

For C-SC05 - in the model you provided, I only see an inflow of 4 L/s. Please clarify what you are seeing and what your specific concerns are in this area.

For R-LM04 - in the model you provided, I only see an inflow of 6 L/s. The inflow in this case is based mostly on the upstream tank R-NB02, which is at a higher elevation (85 m vs. 69 m).