TransAT for Multiphase Flow in Pipes &
Risers
Djamel Lakehal (July, 2013)
ASCOMP GmbH, Zurich
www.ascomp.ch; [email protected]
• Multiphase flow in pipelines
– Slug flow in horizontal pipes
– Slug flow in inclined pipes
– Slug flow with sand
– Slug/churn/annular flow in risers
Outline
Multiphase flow in pipes→
Flow regime map
‣Horizontal pipe flow
‣Vertical pipe flow
Slug capturing and separation
Validation of base LS approach for interfacial (wavy) flows →
‣Experiment by Thorpe (J Fluid Mech., vol 39, 25-48, 1969) ‣Interesting because purely hydrodynamic, simple geometry and Bc’s ‣Limited results to most amplified wave length, critical velocity difference
The Thorpe experiment
The ‚refurbished‘ experiment (UCL, Belgium: J-M. Seynhaeve, Y. Bartosiewicz)
‣Calculated acceleration ramp to minimize initial perturbations ‣High speed camera ‣PIV (2D and stereoscopic)
‣Fluids fully characterized in house (surface tensions, densities, viscosities)
Flow visualization
Comparison
CLICK ON MOVIE
Comparison
The HAWAC setup (FZD Germany, C. Vallé)
Picture sequences at JL = 1.0 m/s and JG = 5.0 m/s with ∆t = 50 ms (depicted part of the channel: 0 to 3.2 m after the inlet)
Comparison
Slug formation in horizontal pipes →
Slug formation in an air-water flow.
Important features :
flow pattern: e.g. from stratified to slug
(Kelvin-Helmholtz instabilities)
Slug formation threshold
Pressure drop and slug speed
Slug formation: 1- ASHRAE case (Exp. Martin)
Exp. of Martin (2005)
-BFC grid 200.000 & 600.000
- 12 parallel blocks
- L = 6.3m; D=0.14m - JL=0.5m/s & JG= 14m/s. - Void fraction 50% - V-LES & LES for turbulence
3D slug formation
CLICK ON MOVIE
1.2 0.532 /s m l g lU U Dg
• Nicklin et al. (1962)
• Collins et al. (1978) Exp. Martin et al. (2005)
Liquid Temperature : -45°C; Liquid Depth : 76.2 mm
GasLiquid
PCB1 PCB2 PCB3
PCB4
PACE1 PACE2 PACE3 PACE4 PACE5
GasLiquid
Liquid SlugV
Location x (Meters)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Tim
e (S
eco
nd
s)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
U = dx/dt = 10.8 m/sec (dm/dt = 0.139 kg/sec)
U = dx/dt = 9.4 m/sec (dm/dt = 0.110 kg/sec)
U = dx/dt = 7.1 m/sec (dm/dt = 0.096 kg/sec)
Slug speed
Slug formation: 2- Imperial College WASP case
Physical Parm. Air water
Density(kg/m³) 1.18 997.1
Viscosity(Pa s) 1.83×10-5 ( at
25˚C) 0.98×10-3(at
25˚C)
Surface tension(N/m) − 0.037 (at 20˚C)
Air
Water
Experimental vs. CMFD of water holdup
Exp. (top) vs. CMFD water holdup results for UsL= 0.611m/s and UsG= 4.64m/s. • inlet pressure= 1atm (Probe • location from 0.76m to 3.56m)
• Initial slugs: at x < 5m
• ‘large’ slugs, or better, ‘operating’ slugs
• Scale ~ 2-4 D
• Hold-up = 1
CMFD 3D results: Slug forms & shapes (16m)
• Next slugs: at x > 5m
• ‘disturbance’ slugs
• Scale ~ 1 D
• Hold-up ~ 0.8-0.9
CMFD 3D results: Slug forms & shapes (16m)
CMFD 3D results: Slug signal (16m)
Sand Transport in pipes→
CLICK ON MOVIES
Sand Transport & Corrosion
Gas
Water/Sand
Slug formation in inclined pipes →
Slug flow up an incline (for CHEVRON USA)
Objective: Simulate slug flow up an incline for 3
different size pipes (2”, 4” and 26”), and estimate the re-
entrainment criteria for removing a settled solids bed.
Surface deformation
Level Sets method with V-LES
CLICK ON MOVIES
Droplet Entrainment in stratified two-phase pipe flows →
LEIS of the flow in a periodic pipe
Flow conditions:
- Domain: 3D x 1D - Grid: 46x96x96
- Re_b = 13000
- Air mass flowrate = 600 kg/hr
- Water mass flowrate = 12000 kg/hr
- Volume flow rate of water is 1/50 of that of air.
Click on movie to play
Courtesy: Badie & Hewitt © Imperial College London
Wetting mechanism
Uair=20 m/s ; Uwater=0.02 m/s; Pipe diameter = 0.078 m
Air-water flow
The practical context
Flow conditions:
- L = 5m; D = 0.5 m
- Splitter plate at inlet: l = 16cm
- Water and air
- UG = 20 m/s; UL = 0.2 m/s.
- Water cut: h/D = 0.14
- Ref = 7050
Computational parameters
- IST Grid 1: 800.000 cells
- CPU: 39H on a Dell PC (16 cores)
- BFC Grid 2: 1.6 million cells (580x 58x54)
- High order schemes: 2nd order time; Quick scheme for convection
LEIS of a space evolving flow in a pipe
Click on movie to play
LEIS of droplet entrainment in a pipe
Hydrocarbon flow in vertical pipes & risers →
Reality: Subsea
flow analysis
The main Issues: flow regime map, pressure drop & heat transients
Riser flow: The issues
Two-phase flow in a pipe (Szalinski et al. 2010)
Dispersed flow in a pipe, experiment of Szalinski et al., Chem. Eng. Sce, (2010)
• 2D axisymmetric steady & unsteady • 56‘000 grid cells • Mixture Algebraic Slip Model • Tomiyama lift & drag coeff. correlations • Turbulence: URANS (results shown)
Case 1 & 2: bubbly flow
Case 3: Slug-bubbly flow
Click on movie to play
Evolution of slug flow at different instants.
Slug-bubbly flow structures
Normalized SGS viscosity in the Taylor bubble wake
Instantaneous pressure drop along the pipe (left panel), and mean pressure drop (right panel): single-phase vs. slug flow
Instantaneous wall frictional velocities along the pipe
Pressure drop and frictional velocity
Annular film flow experiment of Zhao and Hewitt (2012, Imperial College London).
Annular Flow Regime (very thin film)
Annular flow case
Visualized ripple wavy and disturbance waves flow regimes
VG (L/min)
2250 1950 1650 1350 1050
ReG
(104) 9.33 8.09 6.84 5.60 4.35
ReL 211 302 452 603 -
VL
(L/min) 0.35 0.50 0.75 1.00 -
Flow measurement conditions
Flow conditions:
- D = 0.0345 m
- L = 4 m
- Water and air
- VG = 2000 L/m (instead of 1650 L/min), ReG = 8.55 x 104
- VL = 70 L/m (instead of 1 L/min), ReL = 4.22 x 104
- Initial film: h/D = 0.04
Computational parameters & model
- IST Grid : 800.000 (still medium)
- Comp. Time: 49H on 64 proc. (MPI parallel) local cluster
- Level Set
- V-LES for turbulence
- Filter width =0.1D
Thick-film annular flow (VLES + LS)
Flow structures development
CLICK ON MOVIE
Entrainment in the core flow
Film thickness varies with height and circumferentially,
With a radial correlation for the most unstable modes
Film thickness
Film thickness (normalized by initial value)
Film thickness could vary as much as 5 times the initial value
Disturbance waves
Entrainment in the core flow
Coherent/disturbance waves
Flow conditions:
- D = 0.032 m
- L = 0.2 m (shorter length for periodicity)
- Water and air
- VG = 1950 L/m, ReG = 8.09 x 104
- VL = 0.5 L/m, ReL = 302
- Initial film thickness: h/D = 0.01, then ‘h’ adjusts itself to the flow to an average of 1-3 x 10-4
Computational parameters & modelling
- Periodic domain in flow direction to sustain turbulence
- BFC Grid : 937,000 cells, with 12,500 covering cross section
- Comp. Time: 763 CPU H on 15 proc. (MPI parallel) local cluster
- Level Set
- Under-resolved DNS of turbulence; (diffusion effects left to discretization MILES approach)
Thin-film annular flow (LES/MILES + LS)
Thin Film: interfacial instabilities
Thin Film: transition to turbulence
Thin Film: transition to turbulence
CLICK ON MOVIE
Two-phase flow in vertical pipe (FZD)
Bubbly & churn flow experiment of
Prasser et al. (2006). TOPFLOW
- OpenMP 3D computation: 8h on a PC
- 15‘000 – 256‘000 grid cells
- Homogeneous Algebraic Slip Model
- Tomiyama lift & drag coeff. correlations
- Turbulence:
- LES with Smagorinsky model,
- V-LES (only results shown)
- URANS
D = 194mm
Churn flow case (TOPFLOW 118)
churn flow case. TOPFLOW-128
Click on movie to play
Entrainment Modelling:
Annular flow
Annular Flow (full domain)
Jg = 20 m/s, Jl = 1.5 m/s, Domain Spans 1 full wavelength
• Ligament formation, droplet detachment, formation of large disturbance wave clearly visible in these simulations
• Flow for full domain still developing
Annular Flow (full domain)
Cross Sectional View of Full Domain Simulation at (a) t = 5.8 ms, (b) t=33.1 ms, (c) t=78.9 ms, (d) t=133.4 ms
Annular Flow (full domain)
Thank you !
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