Flow Analysis of a Circular Cylinder on the Savonius...

International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:19 No:06 41

190506-2323-IJMME-IJENS © December 2019 IJENS I J E N S

Flow Analysis of a Circular Cylinder on the

Savonius Hydrokinetic Turbine Performance Placed

the Side of Advancing Blade

Priyo Agus Setiawan1,3*, Triyogi Yuwono1,2, Wawan Aries Widodo1

1Mechanical Engineering Department, Institut Teknologi Sepuluh Nopember

Kampus ITS Keputih-Sukolilo, Surabaya 60111, Indonesia 2Center of Excellence in Automotive Control & System, Institut Teknologi Sepuluh Nopember

Kampus ITS Keputih-Sukolilo, Surabaya 60111, Indonesia 3Marine Engineering Department, Politeknik Perkapalan Negeri Surabaya

Jl. Teknik Kimia Kampus ITS Keputih-Sukolilo, Surabaya 60111, Indonesia *Corresponding Author: [email protected]

Abstract— The present study has investigated numerically the

effect of a circular cylinder diameter installed at the side of the

advancing blade on the performance of vertical axis Savonius

water turbine. The 2D simulation in the Gambit and Fluent Ansys

17.0 software has been performed by using the technique of the

moving mesh and the realizable k-epsilon turbulence model, to

compare the Savonius turbine performance between without

(conventional turbine) and with a circular cylinder installed at

the side of the advancing blade. The numerical validation is done

by comparing the result with published experimental data. In this

phase, the parameter used is the torque coefficient on the air fluid

by varying the three meshes from coarse to fine. Then, after the

numerical validation is reached, the working fluid in the

simulation will then be converted to water, then the ratio of the

diameter of the circular cylinder and the Savonius turbine varies

ds/D = 0.1, 0.3, 0.5, 0.7 and 0.9. The flow visualization show that

placing the circular cylinder beside of the advanced blade will

reduce the pressure and increase the velocity attached on convex

advancing blade. The results show that the highest power

coefficient (Cp) occurs at ds/D = 0.7 and TSR = 0.7, where the

increase in Cp can reach more than 28% compared to the

conventional one.

Index Term— savonius turbine; circular cylinder; advancing

blade; torque coefficient; power coefficient; moving mesh.

I. INTRODUCTION Indonesia is an archipelago country that has many seas not used

optimally for marine renewable energy. Purba et al have done

observation toward the ocean current by measuring average

velocity located Biawak, Anambas, Berhala and the results of

average velocity is 0.272 m/s, 0.055 m/s, 0.135 m/s,

respectively [1]. The velocity of ocean currents in Indonesia is

very low, so the type of turbine suitable for use is the Savonius

turbine which has a low tip speed ratio (TSR). Unfortunately, the Savonius turbine has low performance compared by the

others type of turbine. That is why, investigations have been

conducted by several authors to improve the performance of

Savonius turbines. Kailash et al have made the effort of

improvement toward the Savonius turbine by placing obstacle

as the deflector. The aim of the placing of deflector is to direct

of fluid flowing to the advancing blade to increase the velocity;

where two deflector plates are installed, one in front of the

returning blade and one other at the side of advancing blade of

the turbine. The experimental has been done in the water tunnel

with dimensions 0.73 m of width and 0.33 m of height using the

aspect ratio of the model of 0.7, and the results show that the

maximum of power coefficient (Cp) of 0.25 reached at the Tip

Speed Ratio (TSR) 1.08 [2]. Yuwono et al have conducted the

numerical study by varying the width of curtain plate placing at

the upstream of returning blade of Savonius turbine. They have

proven that placing the curtain plate upstream from the returning blade cannot always improve the Savonius turbine

performance. Where it has been proven that for the widest

curtain of S/D = 2 in Reynolds number of 90,000 is lower than

without curtain or referred to as conventional Savonius turbines

[3]. Kacprzak et al have studied numerically a modified turbine

blade to improve turbine performance. This is the elliptical

turbine blade as a turbine model that has a higher performance

than a coventional one [4]. For the continuation of research

from Kacprzak et al [4], Sanusi et al [5] have carried out

combined blades experimentally using two forms of blades that

are elliptical to concave and circular in shape to convex. It can increase performance 11% higher than conventional blade

shapes at TSR = 0.79. Sanusi et al [6] has studied numerically

for the combined blade of Kacprzak et al [4] toward the flow

characteristics using the 2D simulation. The visualization

analysis uses the contour of velocity and pressure on each blade

by investigating the pattern of a particular flow. The results of

particular flow pattern show that the blade combination of

elliptical-circular has the highest performance, after that the

blade in form elliptical and the lowest performance is the

conventional blade model. The Savonius turbine model uses

overlapping ratios = 0.23 experimentally tested in a water

tunnel has been studied by Nakajima et al [7]. The flow visualization results have concluded the pattern flow as

attached flow in the convex advancing side, dragging flow

occurs after attached flow, stagnation flow in the convex

returning side, overlap flow in the center of the rotor, vortex

flow from the returning and the advancing. Sheldahl et al have

studied the turbine performance experimentally by using the

Savonius model. The experimental data has been obtained by

testing the Savonius turbine in the wind tunnel using velocty 7

m/s and 14 m/s. The models have 1 m of height, 1 m of

diameter, and it has varied the bucket number of 2 and 3 and

overlap ratio from 0.0 to 2.0. The results of the experiment give the recommendation for the bucket number of 2 and the overlap

ratio of 0.1 - 0.15 [8]. The experiment of the Savonius turbine



has been performed in the towing tank with a velocity of 0.56 m/s. The cylinder as disturbance has been placed at the side of

advancing blade numerically by varying the diameter and the

best results occurs at ds/D of 0.7. The results only discusse the

amount of torque and power coefficient [9]. The research about

cylinder also has been done numerically in front of the

advancing by varying the diameter. The results has been

obtained the best performance at the ds/D of 0.5 at stagger 30o

and 60o [10].

Yaakob et al have concluded that the parametric design for

the wind turbine can be used in the water turbine, and the results

of the power coefficient have the same curve compared to the

wind turbine [11]. The authors (Altan et al [12], McTavish et al [13], Rosario et al [14], Satrio et al [15], Wenlong et al [16];

Ariwiyono et al [17], Setiawan et al [9]; Setiawan et al [10],

[18], [19] have investigated numerically that show acceptable

results for simulation.

The description above explains that the obstacle shapes like

a cylinder and deflector plate can improve the turbine

performance. The present study has continued research from

Setiawan et al [9] by adding the flow visualization around

turbine as the velocity contour, the pressure contour and the

pressure different of along blade surface. A circular cylinder

effect will be investigated numerically while it is installed at beside of the advancing blade by varying ds/D = 0.1, 0.3, 0.5,

0.7, and 0.9 for X/D = 0.5 and Y/D = 0.7. It should be noted that

the position of the circular cylinder X/D = 0.5 and Y/D = 0.7 is

determined for no particular reason, but indeed research is

currently being carried out by other groups in the same

laboratory about the effects of X/D and Y/D position for certain

cylinder diameters on the Savonius turbine performance. When

a circular cylinder installed at the side of advancing blade, thus

the gap between the upper side of circular cylinder and the

advancing blade will form a channel like a nozzle. This causes

the fluid flowing through the nozzle to be accelerated and that will increase the momentum of flow in this region. The

momentum of flow in this gap will increase the positive torque,

then it will increase the Savonius turbine power. In practice, this

configuration might be applied in a small river or a water

channel with one direction flow of water. Therefore, the

objective of this study is to decide the size of a circular cylinder

that is placed on the side of the advancing blade with respect to

the turbine. The numerical simulation will be obtained the best

performance by seeing the effect of a circular cylinder size

include the coefficient of torque and the coefficient of power.

After that, the visualization includes the velocity pathline

structure, the contour of pressure, and the distribution of pressure along the blade surface will be also presented. These

results will be compared to conventional ones.

II. NUMERICAL SIMULATION

A. Computational Domains And Boundary Conditions

The Savonius blade rotates the clockwise (CW) by adding a

circular cylinder placing at the side of the advancing blade.

Fig.1 indicates the position of circular cylinder relative to the

blade. The 2D computational domains and boundary conditions

can be seen in Fig.2. The domain in this simulation has 3 (three) zones namely stationary, wake, and rotating zone. It has two

interfaces namely interface between rotating and wake zone,

interface between wake zone and stationary zone that can be

seen in Fig.2. The boundary conditions are the inlet, outlet upperside, lower side, Savonius blade that can be seen in Table

1.

In boundary conditions, the inlet is as the velocity inlet with

10D of length from inlet to center of Savonius turbine, outlet is

as the pressure-outlet with 10D of length from center of

Savonius to outlet, the lower and upper side is the wall with the

same length in 6D, the turbine blade is the wall and rotation

inserting the angular velocity (rad/s). The first interface is

between the area of the rotating zone to wake zone and the

second interface is between the area of wake domain and

stationary zone. The upper and lower side use symmetry to

avoid the influence of the wall. The upper side and lower side were taken 6D from the center turbine. This present study uses

structured mesh by setting the first layer on the rotor surface.

The changing of the circular cylinder diameter is varied ds/D

from 0.1 to 0.9 with incremental 0.2 that can be seen in Fig.2.

Table I

The boundary conditions for the simulation

Parameter Input

Inlet Velocity-inlet

Outlet Pressure outlet

Upper side Symmetry

Lower side Symmetry

Turbine Wall, rotation,

Interface 1 Interface between rotating and wake

zone

Interface 2 Interface between wake and

stationary zone

Fig. 1. A circular cylinder arrangement toward Savonius

B. Mesh Generation

The computational domains in this simulation consist of three

(3) domains such as the fixed, the rotating and the stationary domains. The meshing in geometry is used quadrilateral

elements for giving the solution of high accuracy that can be

seen in Fig.3. The simulation uses the Realizable k- (RKE) turbulence model by setting the y+ value between 30 and 100

[16]. The y+ value is made by setting the height of the first layer

to the blade surface as showed in Fig.3 (d).

ds/D = 0.1, 0.5, 0.7, 0.5 and 0.9

X/D = 0.5

Y/D = 0.7

X/D

Circular

cylinder

Conventional

Savonius

Y/D

ds



Fig. 2 The 2D computational domain and boundary conditions for

simulation.

(a)

(b)

(c)

(d)

Fig. 3 Grid generation for the fixed domain (a), the wake domain (b), the

rotating domain (c) and blade (d).

C. Solver Setup The solver needs the input data before the simulation is started.

Model for solver will be inserted solver with green-gauss cell-

based, 2D double precisions, transient and viscous with

realizable k-epsilon (RKE). The requirement of the fluent

ANSYS as presented in Table II.

Table II

The requirement of fluent.

Parameter

Input

For verification

and validation

For a water

turbine

General Solver Pressure based,

Transient and 2D

Pressure based,

Transient and 2D

Model Viscous Realizable k-e

(RKE)

Realizable k-e

(RKE)

Material

Air (for

verification

and validation)

ρ = 1.225 kg/m3

μ = 1.7894. 10-5

kg/m.s

ρ = 998.2 kg/m3

μ = 1.003. 10-3

kg/m.s

Cell zone

condition

Rotating zone

Mesh motion,

Material name: air

Rotational velocity

(rpm) for

verification and

validation using

table 3 and 4,

respectively.

Mesh motion,

Material name:

water

Rotational velocity

(rpm) for the

simulation using

table 5

Wake zone Name of Material:

air

Name of Material:

water

Stationary

zone

Name of Material:

air

Name of Material:

water

Boundary

conditions

Inlet Velocity inlet 7 m/s,

Temperature 300 K

Velocity inlet 0.22

m/s, Temperature

300 K

Outlet Pressure outlet, 0 Pa Pressure outlet, 0 Pa

Upper side symmetry symmetry

Lower side symmetry symmetry

Savonius Moving wall,

rotation, no slip

Moving wall,

rotation, no slip

Mesh interface Interface 1, Interface

2

Interface 1,

Interface 2

Solution Monitors

Residual

Absolute criteria

10-5

Absolute criteria

10-5

Run

calculation

TSS using Table 3, 4

and Max Iteration

150 iterations

TSS using Table 5

and Max Iteration

150 iterations

The simulation has used the ANSYS 17.0 to solve

incompressible U-RANS for transient analysis by using the

sliding mesh for this case. For simulation, the increment angle

uses 1o to obtain the accuracy results [15] with the maximum

iteration 150. It means the process achieve the convergence

with setting residual in about 10-5 for all parameters. The

verification has performed at TSR = 1.078 and the velocity = 7

m/s taken from experimental data of Nakajima et al [15]. The mathematics equation includes Tip Speed Ratio (TSR), the

Coefficient of Torque (Cm), the Coefficient of Power (Cp), the

Number of Time Step (NTS), the Time Step Size (TSS) as

indicated in Eq. (1) to (5).

TSR = .D

2 .U (1)

Cm =T

14AsDU2

(2)

𝐶𝑝 = 𝑇𝑆𝑅 𝐶𝑚 (3)

NTS = N 360

(4)

TSS = N

0.15915 ω x NTS (5)

Where N is the number of rotations, is the increasing angle

or degree of rotation of the time step, is the angular velocity of the turbine (rad/s) and 0.15915 is the constant (conversion

from rad/s to rot/s units).



The verification use the data from Table 3 by calculating the angular velocity (rad/s) using equation (1), NTS using equation

(4), TSS using equation (5), and the calculation results can be

seen in Table 3. After that, the validation has been performed

needed the input data that must first calculate ω (rad/s), N

(rpm), NTS and TSS varying the TSR = 0.3, 0.5, 0.7, 0.9, 1.1,

and 1.3 as showed in Table 4. The verification and validation

use the data presented by Sheldahl et al [8]. The next work is to

simulate on Savonius turbine by adding a circular cylinder

installed at the side of the advancing blade. The input data for

software can be seen in Table 2.

Table III

Number of time step and time step size for validation

TSR N (RPM) ω (rad/s) NTS (s) TSS (s)

1.078 144.087 15.095 51871 0.0011627

Table IV

Number of time step and time step size for using air fluid

TSR V

(m/s)

D

(m) N (RPM)

ω

(rad/s)

NTS

(s)

TSS

(s)

0.3 7 1 40.091 4.200 14433 0.00415567

0.5 7 1 66.818 7.000 24055 0.00249340

0.7 7 1 93.545 9.800 33676 0.00178100

0.9 7 1 120.273 12.600 43298 0.00138522

1.1 7 1 144.087 15.095 51871 0.00115628

1.3 7 1 173.727 18.200 62542 0.00095900

Table V

Number of time step and time step size for using water fluid

TSR V

(m/s)

D

(m)

N

(RPM)

ω

(rad/s)

NTS

(s)

TSS

(s)

0.3 0.22 0.4 3.150 0.330 1134 0.05289041

0.5 0.22 0.4 5.250 0.550 1890 0.03173424

0.7 0.22 0.4 7.350 0.770 2646 0.02266732

0.9 0.22 0.4 9.450 0.990 3402 0.01763014

1.1 0.22 0.4 11.550 1.210 4158 0.01442466

1.3 0.22 0.4 13.650 1.430 4914 0.01220548

D. Verification And Validation Of Numerical Simulations

The results of post-processing in the transient simulation are

grid convergence to estimate the effect of grid resolution on

calculating of dynamic torque coefficient for a full rotation of

the rotor with three different grid densities, which are

approximately 17,006, 61,105 and 120,000 nodes as shown in

Fig.4. Simulations have performed on a conventional Savonius

turbine at TSR of 1.078 following the value in Table 2. The verification has been performed by replacing the

element size near the blade with the node number 61,105 and

120,000 nodes have given the same trend results. By

considering the time consumption for economic reasons, the

grid with 61,105 elements would be chosen for the validation

step. The numerical validation has been done by comparing

with the experimental results presented by Sheldahl et al [8].

The comparison results of the average coefficient of torque

(Cm) between the numerical and experimental by varying TSR

of 0.3, 0.5, 0.7, 0.9, 1.1 and 1.3 can be seen in Fig.5. The graph

can be conclusions and is considered valid for used on the real

problem by installing a circular cylinder. The validation of the numerical simulation has shown high accuracy in comparison

with the experimental of Sheldahl et al. [8] by varying TSR.

The next step performed by changing fluid from air to water.

The input data of the real simulation was shown in Table 2.

Fig. 4 Comparison of grid convergence for verification.

Fig. 5. Validation of the torque coefficient (Cm).

The numerical domain has been tested to Savonius turbine

for low current with the current velocity of about 0.22 m/s. The

application on the Savonius turbine of vertical axis has been

done the validation process. The inlet as velocity-inlet has applied for the value current velocity of 0.22 m/s. The Savonius

turbine has a diameter of 0.4 m with the sliding mesh condition

for transient flow. The next numerical simulation will be done

by placing a circular cylinder on vertical axis Savonius water

turbine in front of the advancing blade.

Considering this present study, in which simulations have

applied to vertical axis Savonius water turbine so that the air

would be converted to water after validation has achieved. The

study has been performed at the velocity 0.22 m/s kept constant

and the Savonius turbine is 0.4 m of diameter. When validation

has been achieved, the study in this problem has been

performed by installing a cylinder placed the side of the advancing blade with the Y/D = 0.7 and the X/D = 0.5.

III. RESULTS AND DISCUSSION

A. Torque and power coefficient

Fig.6 and Fig.7 indicate the graph of the torque coefficient and

the power coefficient, respectively, as function of tip speed ratio

(TSR). The coefficient of torque increase at ds/D = 0.7 for TSR

from 0.5 to 0.9, and it will also increase at ds/D = 0.9 for TSR

1.1 and 1.3.



Fig. 6. The torque coefficient as the function of TSR with the changing of

the cylinder diameter.

Fig. 7. The power coefficient as the function of TSR with the changing of

the cylinder diameter.

Compared to the conventional Savonius turbine, the

present of circular cylinder with ratio of diameters (ds/D)

varies 0.1, 0.3, 0.5, 0.7 and 0.9 have a positive impact on

the torque coefficient. Where, the torque coefficient will

increase with increasing ds/D up to 0.7. The maximum

torque coefficient occurs at ds/D = 0.7 and then the increase

in ds/D > 0.7 will decrease the coefficient of torque. The analysis of power coefficient in Fig.7 similar to the torque

coefficient, where the coefficient of power increases by

increasing the torque coefficient. The maximum coefficient of power (Cp) is also obtained at ds/D = 0.7, where the

increase in Cp can reach more than 28% at TSR = 0.7

compared to the conventional one. The depth analysis can

be performed by investigating the changing of ds/D toward

the dynamic torque coefficient for one rotation as shown in

Fig.8.

B. Torque Coefficient For One Rotation

Fig.8 indicates the coefficient of dynamic torque one rotation

for 360 degrees at TSR of 0.7 with respect to change of ds/D.

Peak dynamic torque coefficient has increased by increasing

ds/D and the turbine performance also increase. In the range from 0 to 30 degree, the dynamic torque coefficient has shown

increasing the torque coefficient for all diameter variations.

But, In the range from 30 to 120 degree, the best improvement

of maximum dynamic torque coefficient obtained at ds/D of 0.7

and then followed by ds/D of 0.9, where the both are higher than

the conventional one. The analysis in the range from 120 to 195

degree, the minimum dynamic torque coefficient is showed at

ds/D of 0.5. By decreasing the torque coefficient in this range,

it shows that the cylinder diameter ds/D of 0.9 will decrease the

torque coefficient however it can decrease the power coefficient

or the performance coefficient. The Peak dynamic torque coefficient occurs at ds/D of 0.7 and 0.9. In a range from 105 to

195 degree, the maximum dynamic torque coefficient occurs at

ds/D of 0.7. The maximum overall dynamic torque coefficient

is predicted occurred at ds/D of 0.7.

Fig. 8. Dynamic torque coefficient at a tip speed ratio 0.9 with respect to the

changing of circular cylinder diameter (ds/D).

C. The Velocity Pathline Structure at TSR = 0.9, = 30o to Advancing Blade Side

Fig.9 illustrates velocity pathline structure for changes in the

diameter ratio of ds/D which vary of 0.1, 0.3, 0.5, 0.7 and 0.9.

The formation of stagnation point over the single circular

cylinder occurred in front of a circular cylinder. The position of

stagnation point will change when a circular cylinder near rotating equipment as the Savonius turbine. The change of

stagnation point occurred at the upper side as shown in Fig.9.

The change of stagnation position in front of the cylinder is

caused by Savonius turbine for all circular cylinder diameter

variations. Nakajima et al. (2008) have found the flow

characteristic around Savonius namely attached flow, dragging

flow, stagnation flow, overlap flow, vortex from advancing and

vortex from returning. In this case, overlap flow does not occur

at conventional Savonius with zero overlap ratio.

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0,5 0,7 0,9 1,1 1,3

To

rqu

e C

oef

fici

ent

(Cm

)

Tip Speed Ratio

Conventional Savonius

ds/D = 0.1

ds/D = 0.3

ds/D = 0.5

ds/D = 0.7

ds/D = 0.9

0,12

0,14

0,16

0,18

0,20

0,22

0,24

0,26

0,28

0,5 0,7 0,9 1,1 1,3

Po

wer

Co

effi

cien

t (C

p)

Tip Speed Ratio

Conventional Savonius

ds/D = 0.1

ds/D = 0.3

ds/D = 0.5

ds/D = 0.7

ds/D = 0.9

-0,40

-0,20

0,00

0,20

0,40

0,60

0,80

1,00

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330 345 360

Dynam

ic T

orq

ue

Coef

fici

ent (C

m)

(deg)

Conventional Savonius ds/D = 0.1

ds/D = 0.3 ds/D = 0.5

ds/D = 0.7 ds/D = 0.9



(a) Conventional Savonius

(b) ds/D of 0.1

(c) ds/D of 0.3

(d) ds/D of 0.5

(e) ds/D of 0.7

(f) ds/D of 0.9

Fig. 9. Velocity pathline structure for the changing of the cylinder diameter at TSR of 0.9 and blade angle () of 30o.

The formation of stagnation point also occurs in the front

surface of the returning blade called stagnation flow. Stagnation

flow always occurs at the convex returning blade. The

investigation of flow visualization is observed around Savonius blade with the following analysis from Nakajima et al. (2008).

The formation of the vortex can be found at the edge of the

advancing blade side for all circular cylinders variations. The

gap of two bluff bodies has caused the flow accelerated. On

other hands, the increase of velocity will increase the flow

momentum between both of bluff bodies that can be seen in Fig.9 (e). Therefore, the flow momentum will increase when a

circular cylinder is mounted at the advancing blade side. The

Vortex shedding from returning

Vortex shedding from advancing

Attached flow

Dragging flow

Stagnation flow

High velocity

Vortex shedding from advancing


Attached flow

Dragging flow

Stagnation flow


Attached flow

Dragging flow

Stagnation flow

Attached flow


Dragging flow

Stagnation flow


Attached flow

Dragging flow

Stagnation flow


Vortex shedding from advancing Attached

flow

Dragging flow

Stagnation flow



edge of the advancing blade has shown the vortex formation at returning and advancing blade. Stagnation point has occurred at

the returning blade that can be seen in Fig 9. (e). Attached flow

and dragging flow always occur at convex advancing blade.

Attached flow is indicated by high velocity increasing ds/D.

The maximum velocity area has been reached at ds/D of 0.7 and

decreased at ds/D of 0.9. The velocity in the attached flow area

can cause the drop pressure at the advancing blade, however it

will increase the positive torque and automatically the power

also increases. The prediction of the maximum power

coefficient occurs at ds/D of 0.7.

D. The Pressure Contour at TSR = 0.9, = 30o to Advancing Blade Side

Pressure contour by varying ds/D can be seen in Fig.10. Attached flow regime has shown the changing of pressure. On

other hands, the low pressure has occurred in this regime. This

shows that a circular cylinder can cause the drop pressure at the

convex side of the advancing blade. The negative pressure that

occurs at convex of the advancing blade will cause the

increasing positive torque, however it also will increase the

power coefficient. The prediction of the highest performance

will occur at ds/D of 0.7 that based on the average torque

coefficient.

(a) conventional Savonius

(b) ds/D = 0.1

(c) ds/D = 0.3

(d) ds/D = 0.5

(e) ds/D = 0.7

(f) ds/D = 0.9

Fig. 10. Pressure contour for the changing of the cylinder diameter (ds/D) at TSR = 0.9

and = 30o.

E. The Pressure Distribution On The Blade Surface At TSR =

0.9, = 30o to Advancing Blade Side

The pressure distribution has been investigated by varying ds/D

at TSR = 0.9 and the blade angle () = 30o that can be seen in Fig.11. The graph shows two regimes namely the pressure

distribution of the advancing blade and the returning blade. The

pressure distribution will be investigated in the front and back

side. The graph shows that the pressure distribution in front side similar to all variations at the advancing blade, and the pressure

distribution in the back side has been obtained the highest

pressure at ds/D of 0.7 for the returning blade. The graph hows

the pressure distribution where the negative pressure occurs at

the back side. The pressure distribution at back side of the

advancing blade shows that ds/D of 0.7 have more negative

Low pressure

Stagnation pressure



pressure than the other and the pressure distribution at the returning blade is not significant toward cylinder variations.

The analysis is performed by correlating the pressure and

velocity contour. It is taken the result of the pressure

distribution significantly at the back side of the advancing blade

as shown in Fig.11. The negative pressure in the graph shows

the circular cylinder diameter effect has increased the velocity

at the back side of the advancing blade. The results of velocity

contour show that the highest velocity occurs at the ds/D of 0.7

and the lowest pressure occurs in this variation.

Fig. 11 Pressure distribution on blade surface for the changing of the

cylinder diameter ds/D of 0.5 at TSR = 0.9 and = 30o.

IV. CONCLUSION

Based on the discussion above, the effect of mounted a

circular cylinder the Side of the advancing blade with the

variation of ratio diameter of circular cylinder and Savonius

turbine (ds/D) can be quantitatively predicted. The changing of

ds/D cause an increase velocity in the attached flow area and the maximum velocity occurs at ds/D of 0.7. The velocity in the

attached flow provokes a blade pressure drop on the backside

of advancing blade which causes an increasing of the net

pressure. Finally it causes an increase in drag pressure on the

advancing blade and automatically in positive torque. Among

the circular diameter tested, the circular cylinder diameter of

ds/D = 0.7 gives the highest power coefficient (Cp) at TSR =

0.7, where the increase in Cp can reach more than 28%

compared to the conventional one. The simulation results also

confirm that there is no overlapping flow in conventional

Savonius turbine due to the absence of overlap ratio in

conventional Savonius turbine.

ACKNOWLEDGMENT

The authors would like to thank the Shipbuilding Institute of

Polytechnic Surabaya has given for all support to finished this researches.

REFERENCES [1] N. P. Purba, J. Kelvin, M. Annisaa, D. Teliandi, K. G. Ghalib, I. P. Resti

Ayu and F. S. Damanik, F.S, “Preliminary research of using ocean

currents and wind energy to support lighthouse in small island Indonesia,”

Energy Procedia, vol. 47, pp. 204-210, 2014.

[2] G. Kailash, T. I. Eldho and S. V. Prabhu, “Performance Study of Modified

Savonius Water Turbine with Two Deflector Plates,” International

Journal of Rotating Machinery, vol. 2012, pp. 1-12, 2012.

[3] T. Yuwono, A. A. Latip, N. P. Putri, U. Muhammad, E. N. Mazhilna,

C.Ariyanto, U. Andaryani and A. F. Fauzi, A. F, “Numerical study on the

effect of width of single curtain on the performance of Savonius wind

turbine,” MATEC Web of Conference, vol. 154, pp. 01110, 2018.

[4] K. Kacprzak, G. Liskiewicz and K. Sobczak, “Numerical investigation of

conventional and modified Savonius wind turbines,” Renewable Energy,

vol. 60, pp. 578–585, 2013.

[5] A. Sanusi, S. Soeparman, S. Wahyudi and L. Yuliati, “Experimental

Study of Combined Blade Savonius Wind Turbine,” International Journal

of Renewable Energy Research, vol. 6, pp. 614-619, 2016.

[6] A. Sanusi, S. Soeparman, S. Wahyudi and L. Yuliati,” Performance

Analysis of a Combined Blade Savonius Wind Turbines,” International

Journal of Fluid Machinery and Systems, vo. 10(1), pp. 54-62, 2017.

[7] M. Nakajima, S. Iio and T. Ikeda, “Performance of Savonius Rotor for

environmentally friendly hydraulic turbine,” Journal of Fluid Science and

Technology, vol. 3(3), pp. 420 – 429, 2008.

[8] R. E. Sheldahl, L. V. Feltz and B. F. Blackwell, “Wind Tunnel

Performance Data for Two- and Three-Bucket Savonius Rotors,” Journal

of Energy, Vol. 2, pp. 160-164, 1978.

[9] P. A. Setiawan, T. Yuwono and W. A. Widodo, “Numerical simulation

on improvement of a Savonius vertical axis water turbine performance to

advancing blade side with a circular cylinder diameter variations,” IOP

Conf. Ser.: Earth Environ. Sci., vol. 200, pp. 012-029, 2018.

[10] P. A. Setiawan, T. Yuwono and W. A. Widodo, “Effect of a circular

cylinder in front of advancing blade on the Savonius water turbine by

using transient simulation”, International Journal of Mechanical and

Mechatronics. 19(01), 151-159, 2019.

[11] O. B. Yaakob, D. T. Suprayogi, M. P. Abdul Ghani and K. B. Tawi,

“Experimental Studies on Savonius-type Vertical Axis Turbine for Low

Marine Current Velocity,” IJE Transactions A: Basics, vol. 26(1), pp. 91-

98, 2013.

[12] B. D. Altan and M. Atilgan, “An experimental and numerical study on the

improvement of the performance of Savonius wind rotor,” Energy

Convers. Manag. Vol. 49, pp. 3425-3432, 2008.

[13] S. McTavish, D. Feszty, T. Sankar, “Steady and rotating computational

fluid dynamics simulations of a novel vertical axis wind turbine for small-

scale power generation,” Renewable Energy, vol. 41, pp. 171-179, 2012.

[14] L. Rosario, M. Stefano and M. Michele, “2D CFD modeling of H-

Darrieus Wind turbines using a Transition Turbulence Model,” Energy

Procedia, vol. 45, pp. 131–140, 2014.

[15] D. Satrio, I. K. A. P. Utama and Mukhtasor, “The influence of time step

setting on the CFD simulation result of vertical axis tidal current turbine,”

Journal of Mechanical Engineering and Sciences, vol. 12, pp. 3399-3409,

2018.

[16] T. Wenlong, S. Baowei and M. Zhaoyang, “Numerical investigation of a

Savonius wind turbine with elliptical blades,” Proceedings of the CSEE,

vol. 34, pp. 796–802, 2014.

[17] N. Ariwiyono, P. A. Setiawan, A. W. Husodo, Sudiyono, A. Subekti, A.

I. Juniani, S. So’im, P. P. S. Lukitadi, R. Indarti, F. Hamzah, “A

Numerical Study Of The Turbulence Model Influence On A Savonius

Wind Turbine Performance By Means Of Moving Mesh,” Journal of

Mechanical Engineering Research and Developments (JMERD), vol.

42(3),pp. 91-93, 2019.

[18] P. A. Setiawan, T. Yuwono, W. A. Widodo, E. Julianto and M. Santoso,

“Numerical study of a circular cylinder effect on the vertical axis savonius

water turbine performance at the side of the advancing blade with

horizontal distance variations,” International Journal of Renewable

Energy Research, vol. 9 (2), pp. 978-985, 2019.

[19] P. A. Setiawan, T. Yuwono and W.A. Widodo, “Numerical Study of the

Stagger Angle Effect of a Circular Cylinder Installed in Front of

Returning Blade Toward the Vertical Axis Savonius Water Turbine

Performance,” IOP Conf. Series: Journal of Physics: Conf. Series, 1179,

012107, 2019.

-160

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

-1,0 -0,8 -0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0

Pre

ssu

re(P

a)

x/c (m)

ds/D = 0.1

ds/D = 0.3

ds/D = 0.5

ds/D = 0.7

ds/D = 0.9

Returning Blade

Adancing Blade

Front Side Curve

Back Side curve

https://iopscience.iop.org/article/10.1088/1742-6596/1179/1/012107/meta




Flow Analysis of a Circular Cylinder on the Savonius...

Documents

Transcript of Flow Analysis of a Circular Cylinder on the Savonius...