COBEM99

S25 Métodos Numéricos

Title:

NUMERICAL COMPARISONS OF SECOND-MOMENT CLOSURE MODELLING WITH DNS FOR NEAR-WALL SUB-LAYER OF TURBULENCE

Summary :

THE SECOND-MOMENT CLOSURE MODEL (REYNOLDS STRESS MODEL - RSM) ARE HIGH-CLASS AND REFINED MULTI-EQUATION CLOSURE MODELS OF TURBULENCE WITH HIGHER PRECISION, MORE COMPLEXITY AND STRONGER ABILITY IN SIMULATION AND PREDICTION THAN THE CONVENTIONAL TWO-EQUATIONS CLOSURE MODELS OF TURBULENCE. THEORETICALLY, THE RSM, WHICH DIRECTLY CLOSE THE REYNOLDS-STRESS TENSOR (RST), HAVE GREAT POTENTIAL AND ENCOURAGING PROSPECTS TO BE ADOPTED FOR MODELLING INDUSTRIAL AND ENGINEERING PROBLEMS. HOWEVER, THE DEVELOPMENT AND APPLICATION OF SECOND-MOMENT CLOSURE MODELS NOW ARE STILL IN THE PRIMARY STAGE, BECAUSE OF THEIR GREAT COMPLEXITY AND ALSO OF THE DIFFICULTY TO MODEL THE NEAR-WALL SUB-LAYER OF TURBULENCE. THE SIMPLIFIED WALL TREATMENT, SUCH AS THE COMMONLY USED WALL-FUNCTION APPROXIMATION, CAN NOT EFFICIENTLY SIMULATE THE COMPLEX EFFECTS OF WALL. FURTHER INVESTIGATIONS OF THE HIGH-CLASS STRESS/FLUX-EQUATION MODELS ARE IN URGENT NEED, ESPECIALLY TO EXTEND THE SECOND-MOMENT CLOSURE TO THE NEAR-WALL SUB-LAYER OF TURBULENCE. DUE TO THE RECENT PROGRESS OF DIRECT NUMERICAL SIMULATION (DNS), IT HAS BECOME POSSIBLE TO TEST TURBULENCE MODELS AT THE LEVEL OF REYNOLDS STRESS BUDGETS IN SIMPLE SHEAR FLOWS. THIS PAPER PRESENTS THE NUMERICAL COMPARISON BETWEEN THE COMPUTATIONAL RESULTS OF MODELLING NEAR-WALL SUB-LAYER OF TURBULENCE BY USING THE LAUNDER AND SHIMA S (L&S-MODEL, 1989) SECOND-MOMENT CLOSURE MODEL AND THOSE RESULTED FROM DNS FOR THE CLASSICAL FLAT-PLATE BOUNDARY LAYER FLOW. KEY WORDS: REYNOLDS STRESS MODEL, SECOND-MOMENT CLOSURE, BOUNDARY LAYER FLOW, NEAR-WALL SUB-LAYER, DIRECT NUMERICAL SIMULATION.

Author :

Righeto, A. M.
Yu, L.

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