**RSICC CODE PACKAGE PSR-461**

**1. NAME AND TITLE**

PELE-IC: Code System for Fluid-Structure Interaction Analysis.

**2. CONTRIBUTORS**

Lawrence Livermore National Laboratory, Livermore, California, through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; CDC7600 (P00461C760000).

**4. NATURE OF PROBLEM SOLVED**

PELE-IC is a two-dimensional semi-implicit Eulerian hydrodynamics program for the solution of incompressible flow coupled to flexible structures. The code was developed to calculate fluid-structure interactions and bubble dynamics of a pressure-suppression system following a loss-of-coolant accident (LOCA). The fluid, structure, and coupling algorithms have been verified by calculation of benchmark problems and air and steam blowdown experiments. The code is written for both plane and cylindrical coordinates. The coupling algorithm is general enough to handle a wide variety of structural shapes. The concepts of void fractions and interface orientation are used to track the movement of free surfaces, allowing great versatility in following fluid-gas interfaces both for bubble definition and water surface motion without the use of marker particles

**5. METHOD OF SOLUTION**

The solution strategy is to first solve the Navier-Stokes equations explicitly using values from the previous time-step. Since these values do not necessarily satisfy the continuity equation, the pressure field is iterated upon until the incompressibility condition for each computational cell is satisfied within prescribed limits. The structural motion is computed by a finite element code from the applied pressure at the fluid-structure interface. The shell structure algorithm uses conventional thin-shell theory with transverse shear. The finite-element spatial discretization employs piecewise-linear interpolation functions and one-point quadrature applied to conical frustra. The Newmark implicit time integration method is used as a one-step module. The fluid code then uses the structure's position and velocity as boundary conditions. The fluid pressure field and the structure's response are corrected iteratively until the normal velocities of fluid and structure are equal. The effects of steam condensation and oscillatory chugging on structures are calculated according to a simplified theory of condensation on a free surface due to C. S. Landram.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

Typical problem run times are from 5 to 40 minutes on the CDC7600. The running time for the six sample problems ranged from 32 to 172 CP seconds.

**8. COMPUTER HARDWARE REQUIREMENTS**

123,000 (octal) words of SCM and 272,000 (octal) words of LCM were required on CDC7600.

**9. COMPUTER SOFTWARE REQUIREMENTS**

PELE was developed on the SCOPE 2.1 and LTSS operating systems. A Fortran compiler is required. The code was tested at NESC in 1980 but was not retested when transferred to RSICC and released in 2001.

**10. REFERENCES**

**a) Included with package:**

W.H. McMaster and E.Y. Gong, "User's Manual for PELE-IC: A Computer Code for Eulerian Hydrodynamics," UCRL-52609 (May 29, 1979).

E.Y. Gong, E.E. Alexander, W.H. McMaster, and D.F. Quinones, "PELE-IC Test Problems," UCRL-52835 (October 1, 1979).

TANK Sample Problem Output from NESC.

**b) Background information:**

W.H. McMaster, D.M. Norris Jr., G.L. Goudreau, D.F. Quinones, E.Y. Gong, B. Moran, and N.A. Macken, "Coupled Fluid-Structure Method for Pressure Suppression Analysis," NUREG/CR-0607 (May 1979).

W.H. McMaster, E.Y. Gong, C.S. Landram, and D.F. Quinones, "Fluid Structure Coupling Algorithm, Computers and Structures," Vol. 13, pp. 163-166 (1981).

**11. CONTENTS OF CODE PACKAGE**

Included in the package are the referenced documents in 10.a and one DOS-formatted 3.5" diskette containing a self-extracting compressed file with source files and test cases.

**12. DATE OF ABSTRACT**

May 2001.

** KEYWORDS:** FINITE ELEMENT METHOD; FLUID DYNAMICS; LOCA