# FEA For a Water Tank

Hi,

I'm trying to do some stress analysis on a tank filled with water, I have split the walls into sections and applied the appropriate pressures. However, I'm confused as to whether I apply the weight of the water+pressure at that height difference to the bottom of the plate; or will the pressure account for the weight already? But this doesn't seem likely as the formula didn't include mass.

Thank you.

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Chestermiller
Mentor
You use the pressure only.

stockzahn
Homework Helper
Gold Member
Hi,

I'm trying to do some stress analysis on a tank filled with water, I have split the walls into sections and applied the appropriate pressures. However, I'm confused as to whether I apply the weight of the water+pressure at that height difference to the bottom of the plate; or will the pressure account for the weight already? But this doesn't seem likely as the formula didn't include mass.

Thank you.
Assume a tank with an area of the bottom 1 m2 and a height of 1 m filled with water. The weight of the contained water then would be 1 m3 of water multiplied with its density ##\rho##, hence 1000 kg corresponding to 9810 N.

Now let's calculate the pressure due to the water: ##p=\rho g h = 1000 \cdot 9.81 \cdot 1 = 9810\;N/m^2##. The force on an area of 1 m2 then is 9810 N, which is exactly the force due to the weight of the water. To find a total pressure at the bottom of course one has to add the atmospheric pressure at the water surface.

Chestermiller
Mentor
Assume a tank with an area of the bottom 1 m2 and a height of 1 m filled with water. The weight of the contained water then would be 1 m3 of water multiplied with its density ##\rho##, hence 1000 kg corresponding to 9810 N.

Now let's calculate the pressure due to the water: ##p=\rho g h = 1000 \cdot 9.81 \cdot 1 = 9810\;N/m^2##. The force on an area of 1 m2 then is 9810 N, which is exactly the force due to the weight of the water. To find a total pressure at the bottom of course one has to add the atmospheric pressure at the water surface.
The atmospheric pressure doesn't have to be included if you're working with gauge pressures. Otherwise, you need to include the air pressure contribution from the outside of the tank as well.