Tsunami Induced Turbulent Coherent Structures

Tsunami Induced TCS

Nearbed TCS Shallow horizontal TCS Near-surface breaking TCS

Harbors and Ports

Pick up and Liquefaction

Scour

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Diane Foster (UNH), Pat Lynett (USC), and Tom Hsu (Udel)Sponsor: NSF CMMI - 1135026

Tsunami Induced Turbulent Coherent Structures

Nearbed TCS

Pick up and Liquefaction

Scour

With significant intellectual contributions from Donya Frank and Meagan Wengrove

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y

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Observations

• NEESR– Large Wave Flume– O. H. Hinsdale Wave

Research Lab• Wave Conditions– Long Waves– Short Waves & Long

Waves– Short Waves

Observations

• BL measurements– u, v, w – 1 mm range bins over 3 cm– 100 Hz

• Bed Roughnesses– Flat– Rippled– Rough

Observations

• BL meaurements– u, v, w – 1 mm range bins– 100 Hz

• Bed Roughnesses– Flat– Rippled– Rough

Single solitary over a flat smooth bed

u (m

/s)

w (m

/s)

Single solitary over a flat smooth bed

u (m

/s)

w (m

/s)

Reynolds Stress Estimate

u

Reynolds Stress Estimate

u

t

Rough Bed

• Flat• Rippled• Rough

Smart Sediment Grains

• Dimensions: – 2.5 x 1.5 x 1.4 cm

• Components: – 2 triaxial accelerometers, memory

card, battery and wireless transmitter.

• Enclosure:– 4.4 cm Delrin plastic sphere– Combined specific gravity of 1.3

Overview of Test Results• Preliminary tests– Low noise floor: 0.3 m/s2

– Accurate reproduction of oscillations with reference accelerometer

• Large-scale wave tank tests– Height=0.20m, Period=3s– Incipient motion at Shields

of 0.025 and Sleath of 0.12– Results indicated plug flow

sediment transport regime

• X-Force Balance yields: where:

Incipient Motion

b

T

p

> ~ 0.37

Sleath (1999)

€

S =ρUoω(ρ s − ρ )g

€

θ = ρu*2

(ρ s − ρ )gd50

p +∂p∂xdx

S +θd50

h> kCb(1+α)

> 0.04~0.08 incipient motion > 0.8 sheet flow

S > 0.29 plug flow

• X-Force Balance yields: where:

Incipient Motion

b

T

p

> ~ ?

Sleath (1999)

€

θ = ρu*2

(ρ s − ρ )gd50

p +∂p∂xdx

S +θd50

h> kCb(1+α)

> 0.04~0.08 incipient motion > 0.8 sheet flow

S > 0.1 plug flow

€

S =ρ Du∞ Dt(ρ s − ρ )g

S +θd50

h

S +θd50

h

Thank you• Boundary Layer

observations over fixed beds

• Particle accelerations of incipient motion and rolling grains