Marine Current Numerical Simulation in the Lembeh Strait, North

Sulawesi, Indonesia

Parabelem Tinno Dolf Rompas, Marianus and John Robby Wenas

Universitas Negeri Manado, North Sulawesi, Indonesia

Keywords: Numerical simulation, marine current, RANS model, marine current turbines.

Abstract: This paper presents a numerical simulation to describe the velocities of marine current in the Lembeh strait,

North Sulawesi, Indonesia. These velocities were used to make the turbine profile in the marine current

turbines. The RANS calculations were performed in its modelling. The turbulence model using the 3D

mixing-length model for shallow water flows that the vertical velocities are small. It’s found the marine

current velocities can be used to design of the marine current turbines in the power plant installation. The

power density maximum capacity in the small zone of Lembeh strait by the numerical measurement result is

82.11 kW/m

which enable to the power plant installation in the future.

1 INTRODUCTION

The study in the Lembeh strait is conducted (Hadi et

al, 2015) to observe the relationship between

morphological and species diversity of sponges in

coral reef ecosystem in the Lembeh Strait and to

investigate the most influential factor of habitat on

the sponge diversity. The study is not investigated a

numerical model and its simulation. Also, in study

(Dwinovantyo et al, 2017) is only to determine

sediment concentration from measured acoustic in

the Lembeh strait. Atmojo et al. (2017) are

conducted experiments and numerical simulations in

Lembeh strait. The results are showed that in the

Lembeh strait enable to applied farming method of

some turbines.

The numerical models and its simulations of

marine current are used by researchers to find

velocity distributions. The validation of a numerical

model is studied by (Rompas et al, 2017d) for

analyzing kinetic energy potential in the Bangka

strait, North Sulawesi, Indonesia. Rompas and

Manongko (2016) are studied the numerical

simulations of marine currents in the Bunaken strait,

North Sulawesi, Indonesia. They study are to get

simulations of the velocity and kinetic energy

distributions. A numerical model is got by (Rompas

et al, 2017b) who described the velocity

distributions of marine current in the Bangka strait

by using RANS (Reynolds-Averaged Navier-Stokes)

equations. The approach of a numerical model is

conducted (Rompas et al, 2017a) to study on marine

currents in the Bangka strait, North Sulawesi,

Indonesia to plan the marine current power plant.

The same study is conducted by (Rompas and

Manongko, 2018a; Rompas and Manongko, 2018b)

in the Manado bay but (Rompas and Manongko,

2018b) presented on the free surface by numerical

modelling. Rompas et al (2017c) are designed a

numerical model for predicting the velocities and

kinetic energies by conditions at low and high tide

currents with two discharges of 0.1 and 0.3 Sv.

respectively. Study on tidal marine currents has

conducted by Martinez et al. (2018), Badshah et al.

(2018), Fraser et al. (2018), Bishoge et al. (2018),

Lust et al. (2018), Frost et al. (2018), and Dai et al.

(2018) which explains that marine currents can

produce electrical energy through the velocity of

marine currents that drive tidal turbines. They are

used the models of numerical and experimental.

Study on modelling and numerical simulations of

marine currents by using CFD (Computational Fluid

Dynamics) has investigated by Schuchert et al.

(2018), Vogel et al. (2018), Gong et al. (2018),

Bonar et al. (2018), Nuemberg and Tao (2018),

Hachmann et al. (2018), Brown et al. (2017), Lo

240

Rompas, P., Marianus, . and Wenas, J.

Marine Current Numerical Simulation in the Lembeh Strait, North Sulawesi, Indonesia.

DOI: 10.5220/0009009102400245

In Proceedings of the 7th Engineering International Conference on Education, Concept and Application on Green Technology (EIC 2018), pages 240-245

ISBN: 978-989-758-411-4

Brutto et al. (2016), Malki et al. (2014), and

Turnock et al. (2011).

The objective of the study is to get a numerical

simulation of marine current in the Lembeh strait,

North Sulawesi, Indonesia for the goal making the

turbine profile that used in development of marine

current power plant in the Lembeh strait in the

future.

2 METHOD

The RANS equations that are deformed by the

Navier-Stokes equations after turbulent averaged

and assumed the pressure in the depth is hydrostatic

(Rompas et al, 2017c). The numerical model is used

the semi-implicit finite difference to solve 3D with

the 3D mixing-length model for shallow water flows

that the vertical velocities are small.

Figure 1: The map of the Lembeh strait

Figure 2: The bathymetry of the Lembeh strait

Figure 1 shows the map of study in the Lembeh

strait, Indonesia. The zone of numerical model is

located between Lembeh Island and Sulawesi Island

on 125

11’15.95”E-125

17’21.98”E and

25’47.65”N-1

32’52.29”.

Figure 2 shows the bathymetry in the Lembeh

strait with the maximum depth of 140 m and at the

small zone is average of 15 m depth and width of

550 m.

Figure 3: Flowchart of a numerical model

Figure 3 shows steps of a numerical model for

the calculation of velocity distributions by using

Marine Current Numerical Simulation in the Lembeh Strait, North Sulawesi, Indonesia

241

Fortran 90 application programs. The input and read

data is the process to read all data and the

calculation of parameters needed for calculation of

the velocities in direction axes x, y, and z

respectively included maximum time to do iteration

that using the all of parameters as explained in

Rompas et al (2017c). The beginning condition is

the all of variable as beginning velocities is zero

included calculation to Tecplot 9 application

programs which is an application for simulation. The

seawater depths are generated by the vertical mesh

using Argus One application programs. The layers of

vertical axis (depth) are generated by indexing and

generating index of boundary layers as denote for

deformation of the meshes. The discharge and

average velocities are calculated to beginning

conditions in calculation the velocities.

The “n” symbol shows the calculation quantity in

iteration to do the calculation process until

maximum iteration. Determination whether a

program can proceed to velocities calculations

needed to process of the advection. The using of

model turbulence refers to Rompas et al (2017a)

with 3D mixing-length models. The free surface is

calculated by using a linear five-diagonal system to

get the seawater surface elevation. In the other hand,

the components of velocities (U and V) are

calculated by using a linear three-diagonal included

for calculating the convective and viscous term,

whereas for calculating velocity vertical W used

equation in Rompas and Manongko (2018b).

Finally, the calculation results as the velocities (U,

V, and W) printed to simulations in the Tecplot 9

application programs. If iteration is not maximum

then the process back to “n” to do the process again,

and if iteration is maximum then calculation stop.

The velocity distributions are calculated by

numerical computational at the conditions of low

and high tide currents. The conditions are conducted

by Rompas and Manongko (2016), Rompas and

Manongko (2018a), and Rompas and Manongko

(2018b) in the Manado bay and by Rompas et al

(2017a), Rompas et al (2017b), Rompas et al

(2017c), and Rompas et al (2017d) in the Bangka

strait.

Power density of marine current can be

calculated by equations (1) and (2) respectively

(Rompas et al, 2017a).





 







(1)

where, P

is power density per cross-sectional area

in kW/m

and V is the velocity resultant of

marine current, V =

222

wvu 

, and

respectively are scalars (numerical equations), and ρ

= 1024 kg/m

(at 20 C and salinity of 34).

The results of print which are calculated by

numerical then used to process simulation by using

Tecplot 9 application programs. The simulations are

resulted 2D-simulated of velocity distributions when

low and high tide currents. The results of simulation

analyzed by compare to the results of other studies.

Then, the results concluded to reveal the conditions

of marine current in the Lembeh strait.

3 RESULTS AND DISCUSSION

Figure 4 shows the velocity distributions when low

tide currents at discharge of 0.1 Sv (1 Sv = 1000000

/s) (Rompas et al, 2017c). The results are showed

that velocities in around small zone are different to

big zone. That’s because flow of marine current is

blocked by the small zone. Also, the perpendicular

cross-sectional area passed by the current is very

small (average of 8250 m

) compared to the other

zone, so that the velocities of current become large.

Figure 5 shows the velocity distributions when high

tide currents at discharge that same as Figure 4. The

higher velocities are showed on the small zone with

the perpendicular cross-sectional area is so small.

EIC 2018 - The 7th Engineering International Conference (EIC), Engineering International Conference on Education, Concept and

Application on Green Technology

242

Figure 4: 2D-simulated of velocity distributions when low

tide currents

Figure 6 and 7 are show the velocities in around

of small zone are varied from 0.00-5.09 m/s (when

low tide currents) and when high tide currents of

0.00-4.59 m/s (Figure 8 and Figure 9). Both of when

inside and outside the small zone, the velocities are

become small and between the small zone become

large. The results are greater than Atmojo et al.

(2017) who study of marine current energy potential

in Lembeh strait by using numerical simulations of

software world tide 2009. Likewise the results from

Rompas and Manongko (2016), Rompas et al.

(2017), and Rompas and Manongko (2018) by using

the numerical simulations of Fortran 90 and tecplot

9. The current movement is straight not only before

enter the small zone but also after out of the small

zone (Figure 7 is enlarged from Figure 6 which is

marked with red color rectangle), while in Figure 9

(enlarged from Figure 8 which is marked with red

color rectangle), the current moves before enter the

small zone with the direction to Northwest and

living the small zone to West.

Figure 5: 2D-simulated of velocity distributions when high

tide currents

Figure 6: 2D-simulated of velocity value distributions

when low tide currents

Marine Current Numerical Simulation in the Lembeh Strait, North Sulawesi, Indonesia

243

The average velocity before enter the small zone

is 4.00 m/s at the low tide current (Figure 7) and

when the high tide current is 4.00 m/s (Figure 9).

When the currents living the small zone, the average

velocity at low tide currents is 4.50 m/s and when

the high tide current of 4.00 m/s.

Figure 7: 2D-simulated of velocity distributions when low

tide currents in around the maximum velocities

Figure 8: 2D-simulated of velocity value distributions

when high tide currents

The results are showed that marine currents that

flowing in around of small zone when low tide

currents are different when high tide current. The

values when low tide currents more than when high

tide currents.

The result will be used to make the turbine

profiles. The marine current potential for power

plant installation is the small zone that the current

velocities are biggest (Figures 7 and 9 that showed

by the red color rectangle). In this zone, the

maximum capacity of power density that installed by

farm turbines (Figure 7 shows maximum capacity

greater than Figure 9) is 82.11 kW/m

. The results, if

compared by Atmojo et al. (2017), Rompas and

Manongko (2016), Rompas et al. (2017), and

Rompas and Manongko (2018) are greater. The

results are enabling to develop marine current power

plant at the small zone (Figures 7 and 9 in areas the

red color rectangle) in the future.

Figure 9: 2D-simulated of velocity distributions when high

tide currents in around the maximum velocities

4 CONCLUSIONS

The numerical simulation of marine currents in the

Lembeh strait, North Sulawesi, Indonesia was

successfully studied. The velocity distributions when

low tide currents are different when high tide

currents include the values of velocity distributions

which the values when low tide currents are bigger

than when high tide currents. The values are can be

used to design marine current turbines. The capacity

of power plant by the numerical measurement is

enable to install marine current power plant at the

small zone of Lembeh strait, North Sulawesi,

Indonesia in the future.

ACKNOWLEDGEMENTS

The authors are very thankful to DRPM,

Kemenristekdikti, Indonesia which has given

financial in this study.

EIC 2018 - The 7th Engineering International Conference (EIC), Engineering International Conference on Education, Concept and

Application on Green Technology

244

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