turb+mixing%201MM

turb+mixing%201MM - FACE8 Turbulence and Mxing Turbulence...

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1 FACE8 – Turbulence and Mxing Turbulence and mixing FACE8 2007
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2 FACE8 – Turbulence and Mxing Course outline ·1 M M Introduction to turbulence Basic concepts of turbulent flow Turbulent flow structures Energy cascade Turbulent energy spectrum ·2 M M Introduction to boundary layers + free shear flows Boundary layer analysis Transition and turbulence ·3 M M Turbulence and boundary layers ·4 M M Modeling Wall laws RANS & eddy viscosity models ·5 M M RSM, LES and DNS Eddy dissipation models MMA LAR
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3 FACE8 – Turbulence and Mxing Structure of 1 MM · 8.15-8.30: Intro 10 min prep 5 min presentation · 8.30-9.00: Part 1 – turbulence · 9.00-9.15: Break · 9.15-9.45 Part 2 – more turbulence · 9.45-9.50: Break · 9.50-11.20: Problem solving · 11.20-11.25: Break · 11.25-11.50: Problem solving at the board · 11.50-12.00: Resume and next lecture
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4 FACE8 – Turbulence and Mxing The 10 min prep… · Without your books and notes… Explain RANS Prepare a 30 sec answer…
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5 FACE8 – Turbulence and Mxing Some questions to be discussed · What is turbulence - characteristics? How do we use it/depend upon it in our everyday lifes? · Visual interpretations of turbulence Laminar vs turbulent Thermal plumes Wakes around obstacles 1 Wakes around obstacles 2 Channel flows 1 Channel flows 2 Channel flows 3 Boundary layer
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6 FACE8 – Turbulence and Mxing What is turbulence? · Irregularities – randomness Deterministic approaches cannot be used (statistics) We will look at the closure problem later today
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7 FACE8 – Turbulence and Mxing What is turbulence cont’d? · Diffusivity – mixing Increased momentum, heat and mass transfer Combustion efficiency Increased heat transfer rates Delayed boundary layer separation
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8 FACE8 – Turbulence and Mxing What is turbulence cont’d? · The fluid no longer moves as individual molecules but as macroscopic ”lumps” of fluid Highly enhances mixing rates · The flow contains a wide range of length and time scales of the turbulent motion (the stirred tea cup) · The flow is almost always 3-dimensional – vortex stretching Dissipation by viscous forces dampen turbulence unless new energy is constantly supplied Turbulence relies on extracting energy from the mean flow, for example from a shear layer Vortex stretching is an important mechanism feeding energy into vortices
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9 FACE8 – Turbulence and Mxing What is turbulence cont’d? · Transport of x-momentum across the A-A plane by molecular and turbulent motion differ significantly.
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10 FACE8 – Turbulence and Mxing Conceptual illustration of correlation · Lumps of low average u velocity is transported upwards by v’>0. As these lumps retain most of the original average u velocity it will be seen as a negative u’. For v’<0 it is the opposite and u’>0. Consequently in this flow the time average u’v’ stress (or correlation) is negative.
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11 FACE8 – Turbulence and Mxing Some questions to be discussed · What is turbulence - characteristics?
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This note was uploaded on 09/16/2011 for the course ME 563 taught by Professor Staff during the Spring '11 term at Auburn University.

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turb+mixing%201MM - FACE8 Turbulence and Mxing Turbulence...

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