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sunum

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Nazli Yilmaz

on 16 April 2014

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Transcript of sunum

FLUID MUD GRAVITY CURRENTS THROUGH EMERGENT AQUATIC VEGETATION
Fluid mud gravity currents through emergent aquatic vegetation



by

Nazli Aslican Yilmaz


April, 2014

Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
OUTLINE:

Introduction and Motivation

Experimental setup, methodology and measurement techniques

Viscous fluid-mud gravity currents over smooth surfaces
Anatomy of fluid-mud gravity currents propagating through emergent aquatic vegetation
Propagation modeling of fluid-mud gravity currents through emergent aquatic vegetation
Conclusion
MOTIVATION:

Coastal dredge disposal operations result in fluid mud bottom gravity currents.
Fluid-mud underflows overrun everything in its path; damage aquatic flora and fauna, and engineering installations.
Other examples for gravity currents in nature: underwater landslides,snow avalanches, dust storms, ash clouds, etc.
Several industrial applications, i.e. effluent transportation, slurry transportation, free surface flows (foodstuff, paints, concrete)
Gravity Currents:



Viscous-buoyancy phase gravity current









The driving force acting on gravity current per unit width:


The resisting force acting on gravity current per unit width:

Middle East Technical University, Ankara
RESEARCH OBJECTIVES:

To formulate the Fanning friction coefficient for viscous shear forces of the bottom surface for gravity currents propagating over smooth surfaces.
To propose a relationship between the Fanning friction coefficient and Reynolds number for constant-flux viscous gravity currents.
To investigate effect of vegetation on the viscous fluid-mud gravity current anatomy.
To determine the effect of emergent stiff aquatic vegetation on the gravity current propagation dynamics; and formulate f-Re relation.
f-Re relations for closed conduit:

f=16/Re (Moody 1944)

f-Re relations for open channel flows:

Newtonian
f = K/Re (Straub et al. 1958)
K is a function of duct opening (Sparrow 1962)

non-Newtonian
f = 16/Re(Kozicki et al. 1966)
f = 16/Re for rectangular channels (Haldenwang and
Slatter 2006)
K is a function of channel cross-section and fluid
rheology (Burger et al. 2010)
Flow through aquatic vegetation:

Aquatic vegetation

Closed conduit flow through packed columns (Ergun 1952)
f is a function flow and material properties
f - Re relation for closed-conduit

Open channel flow through emergent cylinders (Tanino and Nepf 2008)
f - Re relation for open channel

Gravity current through emergent cylinders (Tanino et al. 2005)
Front velocity formulation for constant-volume Newtonian Gravity currents
Triangular profile of constant-volume Newtonian gravity currents

From conservation of momentum the coefficient of friction:


Order of magnitude analysis of shear stress at position xf :


Reynolds number of gravity current:



Friction coefficient equals to:


Correction factor for shape assumption:
Dimensionless shape factor, K is constant thoughout the propagation.

K is a function of parameters that remain fixed over time in a given gravity current.


K as a function of dimensionless parameters

where

EXPERIMENTAL SETUP:

DENSITY AND RHEOLOGY MEASUREMENTS:

Kaolinite Clay (OM4 Ball Clay)


Experimental conditions:

Only the experimental data that corresponds to the viscous-buoyancy propagation phase is used.
Data is corrected to exclude the side-wall friction force.






Experimental shape factor, K is formulated with a coefficient of determination value of 0.86

Viscous Propagation Model:


Bed Erosion:
increased siltation and sediment transport
self-sustaining turbidity currents
Gravity Current Profile
gravity current profile formulation in terms of friction coefficient, f (Findikakis and Law 1998)
Turbulent-Laminar Transition
critical Reynolds number
Vegetation effect of fluid-mud gravity currents:

3 sets of experiments with different fluid-mud concentrations and vegetation densities.
Presence of the vegetation changes the gravity current profile from blunt head with an almost rectangular body to a smooth distinct triangular shape.


a preliminary parameterization is proposed to relate the current slope to the flow behavior index and the vegetation density
Vegetation effect of fluid-mud gravity currents:
THANK YOU!

? QUESTIONS ?

Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
BACKGROUND INFORMATION:
BACKGROUND INFORMATION:
BACKGROUND INFORMATION:
THEORETICAL ANALYSIS:
THEORETICAL ANALYSIS:
THEORETICAL ANALYSIS:
EXPERIMENTAL METHODOLOGY AND MEASUREMENT TECHNIQUES:
RESULTS:
DISCUSSION:
ONGOING WORK:
ONGOING WORK:
Re - f Relation for Constant-Flux Underflows
Nazli A. Yilmaz
ONGOING WORK:
Vegetation effect of fluid-mud gravity currents:

Vegetation effect on gravity current anatomy will be qualitatively and quantitatively examined.
Fanning friction factor for aquatic vegetation will be formulated.
f-cylinder Re relation will be studied.


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