Slug flow in S-shaped risers

Supervisor: Sigurd Skogestad

Co-supervisor: Esmaeil Jahansahi

Studies on slug flow in S-risers: LedaFlow simulations and

experimentsMahnaz Esmaeilpour

Overview1- Introduction

2- Experiments

3- LedaFlow Simulations

4- Comparing Simulations and Experiments

1. IntroductionSlug flow in S-shaped risers

4 different flow regimes

Stable flow Transitional flow (TTS)

Severe Slugging II Severe Slugging I (SSI)

2. ExperimentsSetup

SensorsPressure sensors Acoustic sensor

2. Experiments (contd)

• Step change test in stable region

• Series of tests with different Usl’s and Usg’s to make related flow regime map

• Series of tests with different valve positions to make the bifurcation diagram

Usl = 0.2 [m/s] Usg = 1 [m/s]

2. Experiments (contd)

Step change test in stable region

Step change test in stable regionFFT of acoustic signal

2. Experiments (contd)

2. Experiments (contd)

Flow regime map

• 70 points of different gas & liquid superficial velocities

• Choke valve was fully open (100 % of valve opening)

0 1 2 3 4 5 60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Experimental Flow Regime Map

SS1

SS2

TTS

STABLE

Usg[m/s]

Usl [

m/s

]

2. Experiments (contd)

Bifurcation diagram

10 20 30 40 50 60 70 80 90 100 1100

0.5

1

1.5

2

2.5

3Experimental Bifurcation Diagram

Average pressureMax oscillationsMin oscillations

Valve opening [%]

Pres

sure

[bar

]

Usl= 0.2 [m/s] Usg= 1 [m/s]

3. Simulations• Simulating slug flow in S-riser with LedaFlow

• Make the same flow regime map as experimental one

• Making the same bifurcation diagram as

experimental one by changing valve position in different simulations with a fixed Usl and Usg

3. Simulations (contd)

Simulating slug flow in S-riser with LedaFlow

Severe Slugging I (SSI)Usl=0.1 [m/s] Usg= 1 [m/s]

Transfer region (TTS) Usl=0.1 [m/s] Usg= 4 [m/s]

Stable region Usl=0.2 [m/s] Usg=19 [m/s]

3. Simulations (contd)

Flow regime map based on LedaFlow simulations

4 6 8 10 12 14 16 18 20 220

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9LedaFlow Simulations, Flow Regime map

SS1SS2TTSSTABLE

Usg [m/s]

Usl [

m/s

]

3. Simulations (contd)

Bifurcation diagram

0 20 40 60 80 100 1200

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5LedaFlow Bifurcation Diagram

Average pressureMax. OscillationsMin. Oscillations

Valve opening [%]

Pres

sure

[bar

]

3. Simulations (contd)

Usl= 0.2 [m/s] Usg= 1 [m/s]

4. Comparing simulations & experiments

4 6 8 10 12 14 16 18 20 220

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Simulated Flow Regime map

SS1SS2TTSSTABLE

Usg [m/s]

Usl [

m/s

]

0 1 2 3 4 5 60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Experimental Flow Regime Map

SS1SS2TTSSTABLE

Usg[m/s]

Usl [

m/s

]

4. Comparing simulations & experiments (contd)

Thank you!