Modeling plume from pipeline discharge of dredged material

Transcription

1 Modeling plume from pipeline discharge of dredged material Sung-Chan Kim 1, Paul R. Schroeder, Terry K. Gerald, Tahirih C. Lackey 1, Joseph Z. Gailani 1,Presenter 1 Coastal and Hydraulics Laboratory Environmental Laboratory October 4, 1

2 Outlines Processes Existing models Model improvements Examples and issues Concluding remarks

3 Pipeline Discharge Processes Turbidity Plume Slow Settling Hindered Settling Entrainment Fluid Mud Underflow Accumulated or non-flowing mud

4 Pipeline Discharge Processes Multi-phase plume (open water discharge, overflow, etc) Both inertial force and buoyancy are important Koh & Chang (1973) Convective descent Dynamic collapse Passive diffusion lacking dense plume dynamics

5 Existing Models Automated Dredging Disposal Alternative Management System (ADDAMS) STFATE intermittent disposal (Johnson & Fong, 1995) CDFATE continuous disposal (D-CORMIX: Doneker et al, 4) Brandsma & Divoky (1976) extended Koh & Chang (1973) DIFID intermittent disposal (became STFATE) DIFCD continuous disposal PDFATE (Teeter, ) version Based on turbidity current dynamics over sloped bottom

6 STFATE

7 Schematics of DIFCD

8 DIFCD Jet d ds d ds d ds ( ) πr ρu = Eρ Sρ ( ) a i i i πr ρuu = B + Eρ U S ρu F a a i i D i ( ( ( ) ) ) ( ) ( ) ( ( ) ) πr ρ ρ U = E ρ ρ S ρ ρ E = E + E momentum S = rw C i fi si collapse i fi si a a a i a i i thermal Dynamic Collapse d ( πabl) = Eρa Siρi ds i d ( M ) = B + E ρ U S ρ U D ds a a i i i d ( B ) = E ( ) S ds E = E S = blw C Entrainment Settling ( ρa ρa) i( ρa( ) ρi) Entrainment i Settling

9 PDFATE (version )

10 Mass conservation PDFATE (version ) dq dx S = B EwU PW C Entrainment Deposition s Water loss Momentum conservation dh dx = 1.43C f Ri tanθ Ri ρ dq Ri ρ dcq Ri db h + 1 h h + ρ + Qdx ρ + CQdx Bdx 1 Ri Friction Body force (slope & buoyancy) Spreading db dx EwRi 1.7 C f = 1 B 1.4 1, if Ew ~ c1hri

11 Application Newark Harbor

12 DIFCD D-CORMIX) Mass Entrained (ft 3 ) Clouds at t=36 s Sand Fines1 Fines Distance (ft) C (kg/m 3 ) BH (m) BV (m) X (m) X (m) X (m) Finer more entrainment Each time step produces cloudes Initial entrainment Entrainment after collapse Discontinuity between jet plume and boundary impingement Thinning & spreading of plume after impingement

13 Axi-symmetic Flow development Gravity flow propagation Distinct ambient and gravity flows 3D bottom features

14 New PDFATE Model Schematics Jet Plume Gravity Plume U N x N

15 Gravity plume Mass conservation πrhu = Q Flux (from jet plume) reach thickness speed Momentum conservation u = Sediment fraction dr dt Froude Number = Fr g φh ' Reduced gravity Settling velocity Particle conservation dφ = φ wsf dt h r u h

16 Gravity plume Length scale Deposit r * = Q π η η exp w fs r r * Plume thickness Radial distance

17 Shallow Water Equation h t x uh Mass conservation ( ) Momentum conservation ( ) + uh u h 1 t x g h + + = t φh+ uh φ = wφ x Particle conservation ( ) ( ) fs BC u ( t), = (, ) ( ) u x t Fr g h N N 1 = h u h N X= X=x N

18 Tribell Shoal, James River

19 TSA18r 1 TSA17r Hourly snapshot of ADCP backscatter Bin Secondary plume Bin Stripping (very small) 4 TSA19r Progress Progress Bin Progress 4 TSA1r TSAr Bin 8 1 Bin Progress Progress

20 Concluding Remarks New PDFATE Jet plume from DIFCD Axi-symmetric Gravity plume (box model) Ongoing effort -D shallow water equation Implement stripping function Future plan 3 dimensional bedforms Multiphase flows