Liquid sloshing in a partially filled container

first order stress analysis

10/29/2016

Don Blanchet

3B Associates

dwb3298@verizon.net

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