application of cfd on assessment of drag forces exerted by subaqueous mudflow

8/12/2019 Application of CFD on Assessment of Drag Forces Exerted by Subaqueous Mudflow

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Application of CFD on Assessment ofDrag Forces Exerted by Subaqueous

MudflowPresented by:

Zainul Faizien Haza


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Outline

BACKGROUND

LITERATURE REVIEW

PROBLEM IDENTIFICATION

OBJECTIVES

METHODOLOGY

RESULT AND DISCUSSION

CONCLUDING REMARK


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BackgroundSubmarine slide is one of the geohazards which hasnow become a serious and complex problem in themarine field because it has detrimental consequencesagainst offshore installations such as fixed platforms,submarine pipelines, cables and other seafloorinstallations as well as people and infrastructure alongthe coastlines.

As consequences of rapid development of oil and gasindustry, which is moving to depth over 1000 m alongor in propinquity of the continental slope, pipelinesinstallation are subjected to such geologicallyhazardous condition.The Society of Underwater Technology estimates the

cost to repair pipelines damaged by submarine slidesto reach US$ 400 million per year.

Submarine slide wasgeohazard

Seafloor pipeline wasthreatened bygeologically hazardouscondition


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http://gulfofmexico.marinedebris.noaa.gov/photos-video/SideScan/SideScan01.jpg/image_view_fullscreen

Seafloor pipelines (generally overlying the continental slopes) are subjected tomovements of unstable sediments.

Background
http://gulfofmexico.marinedebris.noaa.gov/photos-video/SideScan/SideScan01.jpg/image_view_fullscreenhttp://gulfofmexico.marinedebris.noaa.gov/photos-video/SideScan/SideScan01.jpg/image_view_fullscreen


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Literature Review

Submarine slide involved cohesive fine-grained material, i.e. clays and silts (Hance2003).

Kaolin was the most predominant clay mineral contained in seafloor sediment (Fallick etal. 1993; Youn et al. 2006; Martn-Puertas et al. 2007).

Findings revealed that in terrigenous clastic sediment, muddy material dominated theschematic of sediment deposits (Nichols 1999).

Submarine slide could reach very long run-out distance up to hundreds of kilometers on agentle slope (Elverhoi et al. 2000; Hance 2003; Blasio et al. 2004; Bryn et al. 2005).

Field investigation


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Numerical modeling

In year 2001, a simulation was performed in 1-D numerical model (Imran et al. 2001).This study was incorporating the model of the Bingham, Herschel Bulkley, and bilinearrheologies of viscoplastic fluids. The numerical simulation with slope of 2 characterized thevelocity up to 16.18 m/s.

Other computational model that was conducted in 2007 was fitted into hydroplaningobservation and proposed a block model for submarine slide simulation (Wright and Hu2007).

Computational model of a relatively new is the impact of submarine debris flow onpipelines which was modeled using computational fluid dynamic that delivered result of dragcoefficient C D for design purpose, related to the value of Reynolds number, Re (Zakeri et al.

2009).

Literature Review


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Availability of CFD software for quantitative prediction of flow phenomenaincluding : all desired quantities with high resolution in space and time; the actualflow domain; and virtually any problem and realistic operating conditions.

Problem Identification

Objectives

With respect to the above circumstances, the current work is aimed t o e m p l o ythe num erica l me thod o f CFD in inves t igat ion and e laborat ion o f the m ode lof sub mar ine s lide , which is simulated by laboratory experiment. Commercialsoftware of ANSYS Fluent 14.0 is utilized to conduct the numerical simulation.Furthermore, the use of CFD in the current work is also to replicate the conditionstested in the laboratory experiment in order to obtain the captured visualizations of

the motion attributes of the sub-aqueous mudflow including velocity and exerteddrag force, which are very difficult to be done using conventional camera.


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Experimental studies and numerical modeling of sub-aqueous mudflow

Experimental studiesNumericalmodeling

Methodology > scheme of work


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determine the magnitude ofthe apparent viscosity, app .

Bro ok field Digital Visc om eter DV-I+

Fann Model 35 Visc om eter

Fann Model 140 Scale Mud B alance

determine the magnitude of the apparentviscosity, app .

determine the magnitude of thedensity ( r ).

mapp ; r

AmericanPetroleumInstitute (API)Standard

ASTM D1092-05

Methodology > m easurem ent devices


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Kaolin clay content(KCC)

(%)

Kaolin Water Mud(liters )

Weight(kg )

Volume(liters )

Weight(kg )

Volume(liters )

10

13

15

18

20

23

25

28

30

35

5.0

6.5

8.0

9.5

11.0

12.5

14.0

15.5

17.0

21.0

1.9

2.5

3.0

3.6

4.2

4.8

5.3

5.9

6.5

8.0

45.0

43.5

45.3

43.3

44.0

41.8

42.0

39.9

39.7

39.0

45.0

43.5

45.3

43.3

44.0

41.8

42.0

39.9

39.7

39.0

46.9

46.0

48.4

46.9

48.2

46.6

47.3

45.8

46.1

47.0

Methodology > m u d m i x d es i g n


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Methodology > kao l in and w a ter com pos i t ion


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Methodology > rec tang ular ch annel ( f lum e)


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Methodology > rec tang ular ch annel ( f lum e)


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Methodology > pipe mod e l


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Methodology > CFD s im ulat ion > pre-pro cess ing

Fluid area x -axis y -axis

Minimum (m)

Maximum (m)

Minimum (m)

Maximum (m)

Mud 0 1.009 0.394 0.60

Water 0.999 8.55 0 0.60

The 18,871 nodes and 18,425 elementswere created by using size function of onproximity and curvature with proximityminimum size of 1.2512e-003 m andmaximum face size of 2e-002 m.


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Experiment Results > rheolog ical pro per t ies

Kaolin clay content(KCC)

(%)

Density ( r f )

GS

Viscosity

(lbs/gal ) (kg/m3)

( Pas )

*Pascal second

Lowest Highest

10 8.79 1054 1.07 0.105 2.201

13 8.93 1071 1.09 0.187 4.882

15 9.10 1092 1.10 0.238 6.170

18 9.21 1105 1.12 0.493 12.204

20 9.45 1134 1.13 0.696 15.096

23 9.57 1148 1.18 1.029 21.881

25 9.60 1152 1.20 2.120 28.642

28 10.19 1223 1.22 2.274 30.198

30 10.30 1236 1.23 2.386 33.636

35 10.55 1266 1.27 4.778 51.543


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nc K =

Herschel-Bulkley model

shear strength (t )yield strength (t c)shear rate ( )

Solver of least squares approach

is employed to generate thefitting curve equation withapproximation error:

N

i

niicii K err

1

2))(( t t

R2 in range 0.996 to 0.999

Kaolin claycontent (KCC)

(%)

t c n R 2

(%)

10 0.60 0.73 0.25 97.09

13 0.69 1.59 0.25 98.99

15 1.71 1.63 0.27 99.43

18 2.69 3.05 0.30 98.94

20 3.40 4.73 0.32 99.99

23 3.47 7.11 0.32 99.92

25 3.57 8.88 0.40 99.79

28 4.96 10.25 0.40 99.90

30 5.70 12.68 0.42 99.99

35 9.00 20.36 0.50 99.99

Experiment Results > rheo log ica l mod e l


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Experiment Results > rheo log ica l mod e l


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Experiment Results > labora tory exper im ents


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Experiment Results > CFD s im ulat ion


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In order to observe the dynamics of nose position, Euclidean method is applied todetermine the distance reached by mudflow between two consecutive capturedimages.

212

212

2 )()( z z l l l ij

Experiment Results > veloci ty m easurem ents


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Mudflow Velocity in Laboratory Experiment


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u= Re

2 f

m

r


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Experiment Results > the co l l i s ions

Lab.Experiment

CFDSimulation


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Experiment Results > labora tory exper iment > drag forces

221 u A

F C f

d d

r

Signal processing isimplemented to get a preciseread of data logger output. Toolof Fast Fourier Transform (FFT)

was employed to analyze thedata logger output.


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Experiment Results > CFD s im ulat ion > co eff . of d rag forces

Coefficient of Drag Forces ( C d ) in CFD Simulation


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Experiment Results > coeff . of d rag forces

Mud

model (%KCC)

r u Re Fd max Cd

(kg/m 3 ) (m/s) (N)

Laboratory Experiment

10 1054 0.29 92.6 0.267 0.74

15 1092 0.25 25.3 0.336 1.19

20 1134 0.27 15.3 0.515 1.44

25 1152 0.26 7.89 0.694 2.14

30 1236 0.25 7.95 1.038 3.17

CFD Simulation

10 1054 0.28 65.54 0.5227 1.61

15 1092 0.31 20.85 0.8823 2.14

20 1134 0.33 10.42 1.7029 3.51

25 1152 0.35 4.20 2.4726 4.46

30 1236 0.38 1.53 5.4901 7.83

Summary of laboratory experiment and CFD simulation


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)15.1(7.2282.0 ed RC

1.1Re19

2.1 Newton iannon

DC

To express the C d as relative to Reynolds number ( Re), which is representing the C d values propagation of the two types of experiment, laboratory and CFD. The

formulation of C d - Re relationship is expressed as follow.

According to the solver of least square approach, the current formulation providedthe R2 = 92.1%.

Similarly, in 2009, Zakeri et al. had proposed a correlation between C d and Re,which was expressed as


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Consider a 100 m section of a 0.15 m diameter pipeline that is subjected to impact by asubmarine debris flow approaching at 3 m/s having a density of 1200 kg/m3 and its flow

properties defined by the following rheological model: t = 500 + 15 0.45

where, t is the shear stress in Pascal. The drag force exerted by the impact per unit length ofthe pipe for the cases of suspended seafloor pipeline installations is obtained through thefollowing calculations:

= u /d = 3 / 0.15 = 20 s-1. Re = ( r x u2) / ( m x ) ; where m x = t t = 500 + 15 x 20 0.45 = 557.75 Pa.

= (1200 x 32) / 557.75

= 19.4

Using proposed equation,

C d = 0.82 + 22.7 Re(-1.15)

= 1.57 F d = r C d A u2 = 199.7 kN

Experiment Results > appl ica t ion example


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The application of commercial software of ANSYS Fluent to create the backcalculation of laboratory experiment was presented. Simulation setup was

implemented as the pressure-based Navier-Stokes ( pbns ) with absolute velocityformulation and mixture-model for multiphase model with two phases of Eulerian phase.

It produced the simulation model, which has similar collision event (betweenmudflow and pipeline) with laboratory work in term of sequential views images of

head flow impaction and the propagation trend line of the drag force coefficientvalues.

Concluding Remark

Furthermore, Re-Cd relationship was suitably expressed asC d = 0.82 + 22.7 Re(-1.15) . The current experiment generated a high similarity oftrend line of Re-Cd relationship with the previous study ( Zakeris equation (Zakeri

et al. 2008)). It indicated that the content of clay material (i.e. kaolin) play a majorrole in mudflow movement and collision, whereas granular materials (used in

previous study) provide an extra density.


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F. Nadim, "Challenges to geo-scientists in risk assessment for sub-marine slides," Norwegian Journal ofGeology, vol. 86, pp. 351-362, 2006.S.-K. Hsu , et al. , "Turbidity Currents, Submarine Landslides and the 2006 Pingtung Earthquake offSWTaiwan," Terr. Atmos. Ocean. Sci., vol. 19, pp. 767-772, 2008.

R. Bruschi , et al. , "Impact of debris flows and turbidity currents on seafloor structures," Norwegian Journalof Geology, vol. 86, pp. 317-337, 2006.D. C. Mosher , et al. , "Submarine Mass Movements and Their Consequences," in Submarine MassMovements and Their Consequences, Advances in Natural and Technological Hazards Research . vol. 28,D. C. Mosher , et al. , Eds., ed New York: Spinger, 2010, pp. 1-8.J. Locat and H. J. Lee, "Submarine Landslides: Advances and Challenges," presented at the The 8thInternational Symposium on Landslides, Cardiff, U.K, 2000.J. O. Shin , et al. , "Gravity currents produced by lock exchange," Journal of Fluid Mechanics, vol. 521, pp. 1-34, 2004.

R. J. Lowe , et al. , "The non-Boussinesq lock-exchange problem. Part 1. Theory and experiments," Journalof Fluid Mechanics, vol. 537, pp. 101-124, 2005.V. K. Birman , et al. , "Lock-exchange flows in sloping channels," Journal of Fluid Mechanics, vol. 577, pp.53-77, 2007.Standards, "ASTM D2196-05 Standard Test Methods for Rheological Properties of Non-NewtonianMaterials by Rotational (Brookfield type) Viscometer," ed: ASTM International, United States, 2005.Z. F. Haza , et al. , "Experimental studies of the flow-front and drag forces exerted by subaqueous mudflowon inclined base," (In Press) Natural Hazards, 2013.P. Coussot, Mudflow Rheology and Dynamics . Rotterdam: AA Balkema, 1997.H. Pazwash and M. Robertson, "Forces on Bodies in Bingham fluids," Journal of Hydrulic Research vol. 13,pp. 35-55, 1975.P. A. Sleigh and I. M. Goodwill, The St Venant Equations : School of Civil Engineering, University of Leeds,England, 2000.

A. Zakeri , et al. , "Submarine debris flow impact on pipelines Part II: Numerical analysis," CoastalEngineering, vol. 56, pp. 1-10, 2009.

A. Zakeri , et al. , "Submarine debris flow impact on pipelines Part I: Experimental investigation," CoastalEngineering, vol. 55, pp. 1209 - 1218, 2008.

References


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application of cfd on assessment of drag forces exerted by subaqueous mudflow

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