v8.21.102 ADLS102 - Meridian fluidielastic oscillator

Summary:

The objective is to calculate the displacement of the piston of a « meridian fluid-elastic oscillator ».

It is a spring-piston coupled with a fluid contained in a channel with rigid and fixed walls; the channel is crossed by a depressurization wave.

The plane problem of this meridian model is considered. This two-dimensional problem is reduced to a one-dimensional problem by considering, by approximation, that the transverse flow velocities induced by the movement of the piston are instantaneously transmitted into axial velocities.

Only one model is used. The calculation of the modes is in formulation \(u,p,\phi\).

2D elements are therefore used; these elements are based on QUAD4 meshes for the fluid and for the piston, on SEG2 meshes for the interface between fluid and piston to take into account the fluid-structure interaction (PHENOMENE =” MECANIQUE “, MODELISATION =”2D_ FLUI_STRU”).

The boundary conditions for the non-return of the wave are achieved by modeling a damper piston at each end; the excitation is achieved by applying a vacuum to the input piston.

The fluid under consideration is water (hot), the model schematizing the fluid-structure interaction in the annular space between tank and core envelope during rapid depressurization.

An exact analytical solution exists. Its comparison with the results produced by*Code_Aster* makes it possible to validate the consideration of fluid structural coupling in 2D.

• 1. Reference problem
  • 1.1. Geometry
  • 1.2. Material properties
  • 1.3. Characteristics of springs, weights and shock absorbers
  • 1.4. Boundary conditions and loads
• 2. Benchmark solution
  • 2.1. Calculation method used for the reference solution
  • 2.2. Benchmark result
  • 2.3. Uncertainty of the solution
  • 2.4. Bibliographical references
• 3. Modeling A
  • 3.1. Characteristics of modeling
  • 3.2. Characteristics of the mesh
  • 3.3. Calculus
  • 3.4. Tested sizes and results
  • 3.5. note
• 4. Summary of results