Turbulence Simulation on the Connection Machine
J. Blair Perot, Principal Investigator
Co-investigator: Paul Malan
Stanford University
## Research Objective

To use direct numerical simulation to investigate the fundamental
fluid and heat transfer physics of wall-turbulence interactions.
## Approach

The unsteady, incompressible Navier-Stokes equations and a passive
scalar equation (for heat transfer) are solved using a second-order,
finite-volume staggered-mesh approach in primitive variables. Time
advancement is performed using a semi-implicit fractional-step method,
and all the relevant scales of turbulent motion are resolved.
## Accomplishment Description

A number of different boundaries were studied using grid sizes over 32
million nodes and obtaining turbulent Reynolds numbers as high as
375. Performance over a GFLOP was obtained on the CM-2, and initial
results of over 500 MFLOPS were obtained using the CM-5. Detailed
near-wall statistics, including Reynolds stresses, turbulent heat
fluxes, and transport equation budgets, were calculated. Statistics
exist for solid walls, free surfaces, permeable walls, and moving
solid walls. The near-wall structures associated with kinematic
effects, viscous effects, and energy transfer were fully
identified. The understanding of these structures has lead to the
development of a number of improved near-wall turbulence models.
## Significance

Understanding and modeling near-wall turbulence is of vital importance
to almost any engineering application which involves fluid
mechanics. This work probes the fundamental physics of the
wall-turbulence interaction and brings closer the development of
rational near-wall turbulence models.
## Future Plans

The effects of small mean shear on near-wall turbulence are under
investigation. There are plans to evaluate large-eddy turbulence
models and extend these studies to curved and rotating walls.
## Publications

1. Perot, J. B.: Direct Numerical Simulation of Turbulence on the
Connection Machine. Parallel Computational Fluid Dynamics 1992,
Elsevier Publishing Co., 1993.
2. Perot, J. B.; and Moin, P.: A Near-Wall Model for the Dissipation
Tensor. Eleventh Australasian Fluid Mechanics Conference, Hobart,
Tasmania, Dec. 14--18, 1992.
Velocity vectors and temperature contours in several planes extending
perpendicularly from a shear-free wall.

*Web Work: kmiceli@nas.nasa.gov*