first order tank sloshing
TRANSCRIPT
Liquid sloshing in a partially filled container
first order stress analysis
10/29/2016
Don Blanchet
3B Associates
Goal
To estimate the structural adequacy of a fluid filled Delrin plastic container.
The actual behavior of the fluid is not a priority.
Analysis
Solid / Fluid interaction requires the use of FEA and CFD or a Multiphysics analysis simulation code.
The accurate use of these techniques requires the skills of an expert analyst and considerable software licensing cost.
A method using only FEA is demonstrated for a first order analysis by a design engineer.
Reference sloshing analysis : nonlinear computational fluid dynamics
From Reference: fluid waves
Not necessaryFor container
Stress analysis
Method – utilize FEA not CFD
Assign material properties to the pseudo “fluid”
– Density of water
– Very small elastic modulus
– 0.495 Poisson’s ratio incompressible
– No penetration surfaces between the “fluid” and the container walls
– Expected behavior like Jello
Model test case
Delrin container½ inch thick
15 x 15 x 10.5
Model
“fluid” ¾ full
Transparent container
1 G local gravity “fluid” without container
Deformation -sagging block of Jello
Jello resonant frequencies
F1 = 5.0 hz
Jello resonant frequenciesF2 = 8.0 hz
Jello resonant frequenciesF3=9.0 hz
Sloshing frequency 11.2 hz
Sloshing frequency 12 hz
Worse case : Crash loading 10G
WaveHeight1 inch
Fixed at bosses4 corners
Maximum Wall stress2900 psi
Factor of safety = 5900/2900 = 2.03