TransAT for Multiphase Flow in Pipes &

Risers

Djamel Lakehal (July, 2013)

ASCOMP GmbH, Zurich

www.ascomp.ch; lakehal@ascomp.ch

• 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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