Cylinder tank hydrostatic pressure problem

- November 18, 2022 at 8:19 pm
  
  Bozsonyik Ármin
  Subscriber
  
  Hello Everyone,
  I'm modelling a rigid tank with SHELL181 and FLUID30 elements in APDL. The cylinder wall height is 15.65 m, the radius is 7 m.
  I have defined the hydrostatic pressure, with SFGRAD and SF,PRES command.
  
  As you can see hydrostatic pressure get correctly along the wall. At the bottom of the wall it is 0.1565 MPa (15.65*10=156.5 kN/m2).
  
  My problem is that the tensile stress with static analysis is 2.5 MPa (2500 kN/m), but according to pressure vessel formula it is P*R=156.5*7=1095 kN/m.
  When I delete the pressure, there is no tensile stress in the wall, so just this hydrostatic pressure cause this stress value.
  How is this possible?
- November 22, 2022 at 5:50 pm
  
  mrife
  Ansys Employee
  
  Hi Bozsonyik Ármin
  That is not the correct "pressure vessel formula"...check the units. Hint: there is a thickness term missing...
  - November 22, 2022 at 6:15 pm
    
    Bozsonyik Ármin
    Subscriber
    
    You are right, I see. Thank you, for your answer!