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Turbulence Simulation on the Connection Machine

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.

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