Committee of the First Makassar International Conference on Civil Engineering

  

Committee of the First Makassar International Conference on Civil

Engineering

SCIENTIFIC COMMITTEE

• Prof. Dennes T. Bergado (Thailand)
• Prof. Toshimitsu Komatsu (Japan)
• Prof. Tetsuro Esaki (Japan)
• Prof. Shigenori Hayashi (Japan)
• Prof. Shinji Kawabe (Japan)
• Prof. Jinchun Chai (Japan)
• Prof. Yan-Jun Du (China)
• Prof. Indrasurya B. Mochtar (Indonesia)
• Prof. Herman Parung (Indonesia)
• Prof. Mahmood Md. Tahir (Malaysia)
• Prof. Robert J. Verhaeghe (Netherland)
• Prof. Dadang Ahmad Suriamiharja (Indonesia)
• Bambang Trigunarsyah, PhD (Australia)
• Marolo Alfaro, PhD (Canada)

ADVISORY COMMITTEE

• South Sulawesi Governor * Rector of Hasanuddin University * Dean of Engineering Faculty * Head of Civil Engineering Department * Secretary of Civil Engineering Department * Prof. Mary Selintung * Prof. Lawalenna Samang * Prof. Herman Parung * Prof. Wihardi Tjaronge * Prof. Dadang Ahmad Suriamiharja * Dr. Arsyad Thaha * Dr. Sakti Adji Adisasmita * Dr. Rudi Djamaluddin

ORGANIZING COMMITTEE

  Chairman Prof. M. Saleh Pallu Co-Chairman Dr. Tri Harianto Secretary Ardy Arsyad, MEng Bambang Bakri, MEng St. Hijraini, MEng Asiyanthi T. Lando, MEng Treasurer Irwan Ridwan, MEng Members Dr. Mukhsan P. Hatta M. Asad Abdurrahman, MEng Muralia Hustim, MEng

  Proceedings of the First Makassar International Conference on Civil Engineering (MICCE2010), March 9-10, 2010, ISBN 978-602-95227-0-9

EFFECTS OF GROIN PERMEABLE ON FLOW VELOCITY

  1

  2

  3

  4 Hasdinar Umar , Nur Yuwono , Radianta Triatmadja , and Nizam

  ABSTRACT: The Roughness in the open channel are inhibiting factor which depends on the amount of resistance characteristics such as the roughness of channel. This paper investigates the vertical piles in the flow through the open channel which act as hydraulic roughness affecting the flow behaviors. The purposes of this research are to study the reduction coefficient that affects the magnitude of flow velocity in the open channel due to the resistance of vertical piles. The Research based on the influence of the vertical piles to the flow has been studied by previous researchers. The results of those studies explained that the vertical piles can reduce the flow velocity due to the increase of the shear ). stress ( This research uses the structure of the model structure vertical a pile in 2D open channel with the width of channel is 0.6 m and the length is 10 m. The distance between the model structures is determined as two times length of the model structure (2L) and the distance between the vertical piles (G) is 0.7 cm.. The results showed that with the arrangement of the vertical piles, flow rate is reduced compared to the conditions of open channel without a vertical pile structure. The shorter the distance between the pile and the bigger the pile diameter to be used, the smaller the Chezy coefficient is become. Therefore the resistance becomes bigger then the velocity reduced.

  Keywords: flow, velocity, vertical piles, resistance.

INTRODUCTION THE DRAG FLOW

  Flow through an object (either fully or partially The Flow in the open channel is a fluid flow through submerged), then the object will get the force direction channels with free surface. Phenomenon of flow in open of the flow. This force is called drag. The amount of channel with a varieties flow conditions has been studied by hydraulic engineers. The Roughness in the open drag will be influenced by parameters as follows: channel are inhibiting factor which depends on the

  1) b

  shape (S ), amount of resistance characteristics such as the

  2)

  the projection area of the object in the plane roughness of channel. Groin piles in the flow through the perpendicular to the direction of flow ( A ), open channel acts as a hydraulic roughness affects the

  3) flow velocity ( V ),

  flow. Flow velocity distribution with the constraints of a

  4) fluid density (  ), dan

  groin is essential to determine the parameters affecting the flow velocity changes. Some research of groin has

  5) viscosity (  ).

  been investigated by several previous researchers such as Raudkivi (1996), examine the groin permeable form of

  The relation between the drag forces with those vertical piles in the southern Balitic Sea, in Raudkivi parameters can be written by:

  (1996) explained that groin permeable form of vertical

  F f S , A , V , ,    

  D b

  columns act as hydraulic roughness on the coast parallel (1) currents. Bakker et al (1984) and Kolp (1970) in

  Raudkivi (1996) stated that the groin piles can reduce the Using dimensional analysis the equation can be flow velocity parallel to the coast until about half of the expressed in the form of: current speed compares it without piles groin, so that it

  2

  V       

  1 F f R , S A 

  D e b

  2

  can be said that groin piles serve as barriers for flow of

  C f R , S

  current parallel to the coast. Vertical piles can also   

  D e b

  (2) reduce the intensity of turbulence on the sea floor around ₁ the pile. ₂ Lecturer, Hasanuddin University, Makassar 90222, INDONESIA ₃ Professor, Gadjah Mada University, Yogyakarta 55281, INDONESIA

TECHNICAL PARAMETER IN OPEN CHANNEL

THE FLOW CLASSIFICATION

  R 

  One method of solving problems is an open channel with direct step method. In this method, the channel division is done in pale with each breath. Starting from the end of the downstream boundary where the hydraulic characteristics of the expression are known, calculated water depth along the channel. Direct step method is a simple method that can be used for prismatic channels. Figure 1 shows a pale under review for calculations. Assumption that the velocity distribution is a uniform in latitude and Coriolis is taken as 1, then :

  c. Energy Slope

  ); P = wet cross-section circumference (m)

  2

  (7) where R = hydraulic radius (m); A = wet cross-sectional area flow (m

  Hydraulic radius of a look in the flow equation can be formulated as follows

  : P A

  V  y z     

  b. Hydraulic Radius

  )

  2

  = average velocity (m/sec); A = flow cross-sectional area perpendicular to the direction of flow (m

  V

  hf g V y z g

  2

  3

  2

  2

  2

  2

  2

  2

  1

  1

  1

  (8) Remembering :

  I z z z       x

  2

  1

  (9)

  /sec);

  (6) where: Q = discharge (m

  D C is the resistance coefficient (drag) which is a

  (3)

  (4) where U = velocity (m/sec); L = length (m);  = kinematic viscosity (m

   

   L U R e

  The turbulent flow of fluid particles move in the direction that causes irregular change of momentum, mass and energy from one part to another fluid. In Chow, 1997, the ratio of inertial forces to the viscous force per unit volume is known as the Reynolds number (Re). Reynolds number can be written as follows:

  1. Laminar and turbulent flow Laminar flow is a steady flow, fluid particles move along smooth lines layers by layers of a smooth glide with the other neighboring layers. Laminar flow can be observed in the fluid that has a high viscosity and low velocity.

  The flow can be classified into types by the criteria:

  1 V A C F D D      

  V Q  

  2

  2

  function of Reynolds number (Re) and the shape (S b ). C D for cylinder is 1,2.

  a. Discharge

  Discharge is the amount of liquid flowing through a cross-flow per unit time. Discharge was measured in liquid volume per unit time. In an ideal liquid, is considered not having friction with the edge of the channel, either open channel or pipe. So the speed has the same value for every point in the look of latitude. Flow equation through a cross-section is described as follows:

  A

  2

• 6

   500  laminar flow 500 < Re  2000  transitional flow Re

  The following values are Reynolds number limitation of fluid flow characteristics in open channel flow: Re

  /sec) = 1,004 x 10

  2. Subcritical and supercritical flow Comparison of inertial forces to gravitational forces per unit volume is known as the Froude number (Chow,

  1997), can be written

  as: D g

  V F r

   

  (5) where

  r F = Froude number; V = velocity (m/sec); g

  = the acceleration due to gravity (m

  2

  /sec);

  D

  = hydraulic depth (m) Flow critical to say the same if the Froude number 1, the flow is called subcritical if the Froude number is less than 1 and the flow of supercritical Froude numbers when more than 1. Subcritical flow is sometimes called balance flow while the term rapid flow and flow incubate (shooting flow) is also used to express the flow supercritical.

   2000  turbulent flow

  1/2 C h 

  I   x where = Chezy coefficient (m /sec); R = hydraulic f f

  (10) radius (m);

  I = average energy slope of 1 and 2 expression.

  So :

  2

  2 V

  V

  1

  2 FLOW THROUGH VERTICAL PILE BARRIERS I   x  y   z  y   I   x

  1

  2 2 f

  2

  2 g g

  Flow through a vertical pile barriers on the open

  2

  2    

  V V

  2

  1

  channel is influenced by 2 type of shear stres, which are:

  y   y 

  2

  1    

  2

  2 g g

       x 

  a. Shear stress between the base with water channels

  I I  f

  (11)

  b. Shear stress between the vertical piles with water or Shear stress equation of flow through a vertical pile constraints can be formulated as follows

   I  I   x  E  E f s 2 s

  1

   =   (14) +

  o

  1

  2

  2 E  E s 2 s 1  

  where = total shear stress (kg/m .sec); = shear stress

  o

  I   f

  1 I

  2  x between the base with water channels (kg/m .sec);  =

  2

  (12) shear stress between the vertical piles with water

  2

  (kg/m .sec) where:

  V

  2  . g .

2 V   (15)

  o

  2 E  h  C s o

  2 g  2  . g .

  V   (16)

  1

  2 C _{2 f}

  1 V ^{1 /2g Energy slope, I h f = I f .}

∆x

₂ Shear stress between the vertical piles with water is a relationship between large stems, number of stems and

  V /2g Surface water, I w ² _D

  the coefficient of drag (C ). This is becaused the

  y ₁

  function of vertical piles is becoming barriers to the flow therefore it can be formulated resistance force to the flow of the vertical piles.

  y ₂

  2 V Bottom channel, I o

  F C  A (17) I o

      ∆x

  D D ∆x

  2 z

  Reference line ² If the resistance force is the same with the shear z ¹

  stress F  and the area of the vertical pile which

   D

  2 n

  N

  Figure 1. Part channels to reduce direct step method

  A z . d

  resist the flow is  , then the resistance

  i  b . L

   i force to shear stress.

d. Chezy coefficient

  _n

  2 N

  V  C  z d (18)    . 

  2 D i  b L

  .  i

  2 Energy slope I is the average energy of 1 and 2 f

  expression. So that the Chezy coefficient values can be Shear stress from the equation of flow through a searched with a length of pale (  x ). Chezy coefficient vertical pile obtained Chezy coefficient equation of flow ( C ) can be calculated by using Equation 13. through a vertical pile resistance with the influence of

  V

  the channel bottom roughness:

  C 

  (3-14)

  R 

  I

  1 where Vt = velocity with groin (m/sec); Vo = velocity C  _{o n} without groin (m/sec); K = reduction coefficient.

  C  N  d  z _{D i} 

  Reduction coefficient is the function of barrier groin

  1 (19) _{i 2}  structure.

  C ₁ 2  g  b   L Permeability of the Vertical Pile Structure LABORATORY RESEARCH

  Permeability structure of the vertical pile structure is the ratio between the distances between the vertical piles The model vertical piles have the following design and the diameter of pile multiplied with ratio of width of specifications: the channel and the length of the groin.

  a. Diameter of pile is 1.25 cm

  G l

  b. Number of pile length varies in accordance with

  p  . 100 % d b

  the structure, L = 45 cm and L = 30 cm

  c. The distance between piles in a row model G = (20)

  0.7 cm, the permeability of the structure = 0.5

  G . l d 

  d. The distance between the model 2L .

  p b Equipment used in this study are as follows.

  where d = pile diameter (m); G = distance between the vertical piles (m), b = width of the channel (m), l =

  1. Flume tanks, lines of material flexiglass its length of the groin (m). entirety consists of a channel with a length of 10 meters, 0.6 meters wide, 0.45 meters tall and

  Flow Velocity

  (3-62) the door to regulate the depth of water flow. Velocity of flow through open channel with Chezy

  Channel walls made of translucent material equation is: (glass wall) with a thickness of 10 mm. At the V  C R .

  I (21) edges there revenue water hole (inlet) and the

  excretion of water holes (outlets) Chezy coefficient in the equation of flow through a vertical pile barrier permeability function pile structure of the vertical structure (equation 19) substituted into equation 21 so that the flow velocity equation obtained through a vertical pile constraints as follows:

1 The Flume Tank

  V  R  I (22) n

  C  N  d  z D i

  

  1 i

  

  2 C 2 g b L    

  1 Figure 2. Flume Tank

  where V = flow velocity (m/sec); g = the accelaration

  2

  due to gravity (m/sec ); C = drag coefficient; p =

  D Water from

  permeability of vertical pile structure (%); b = wisech of

  the pump Tail gate Model of Flume

  the channel (m); G = the distance between the piles; I =

  Surface water groin tank

  energy slope; l = length of the groin (m)

REDUCTION COEFFICIENT

  E D C B A

  Groin can reduce flow velocity, the value of speed

  10 m

  reduction can be approached with the equation Figure 3. Scheme of the flume tank and model of groin

  Vt = K. Vo (23) (Side View)

  K = Vt / Vo (24)

  Table 2. Data of flow velocity measurements in the l condition without the model

  G

  Model of groin Measurement point Flow Velocity (Vo) vertical

  (m/sec)

  piles

  A 0,533 B 0,48 h

  1 C 0,48

  6 D 0,48 E 0,474 b = 0,6 m

  Figure 4. Scheme of the flume tank and model of groin Table 3. Data of flow velocity measurements in the

  (front view) condition with the model

  2. Water pump to provide flow simulation in Measurement point Flow Velocity accordance with the planning. The depth of

  (Vt) water in the channel is set using the Flan (m/sec) attached to one end while the rate of flow

  A 0,286 channels can be set according to the use by B 0,257 adding or subtracting using rounds pedal (pedal C 0,257 jack). The stability of the flow velocity can be

  D 0,237 checked by looking at a high moving water or E 0,228 high difference in the orifice tube is inserted in the pipe income (inlet) cannel

  3. Point Gauge to measure the depth of flow Table 4. The results of theoretical calculations on the 4. Stopwatch is used to record the time of flow rate condition without a groin model. measuring the velocity at the time of calibration

  Measurement point Flow Velocity (Vo)

  5. Current meter for measuring the velocity at (m/sec) points that were reviewed

  A 0,24

  6. Camera for documentation and stationery for B 0,25 recording of research results C 0,25

  D 0,26

RESEARCH RESULTS

  E 0,52

  Discharge Flow

  Discharge simulation used in this study is : Table 5. The results of theoretical calculations on the flow rate condition with a groin model (Cd = 0.9)

  Table 1. Data flow calibration results Measurement point Flow Velocity(Vt)

  Discharge recorded Real Discharge (m/sec)

  (lit/sec) (lit/sec) A 0,183

  Y = 0.988x + 0.916 B 0,145 10 10.796 C 0,130 15 15.736

  D 0,123 E 0,125

  Flow velocity

  Flow velocity measurements obtained from the Flow Depth laboratory, can be seen in the table below. The depth of the flow obtained through the observation wall of water on the glass and through a channel measurement using a point gauge.

  Energy Slope

  Energy slope ( I f ) is specific energy difference in Table 7. Chezy coefficient without groin both look long divided by pale ( x). Energy slope can be

  Flow Energy Chezy calculated by using equation 13. Measurement Velocity slope coeffient point

  (Vo) The results of calculations are given in Table in

  (I )

  f (C )

  1

  below (m/sec))

  A

  0.533 0.002

  42.4 B Table 5. The results of the energy slope (without groin)

  0.48 B 0.48 0.002

  38.4 C

  0.48 Specific

  C

  0.48 0.001

  54.6 Energy Measurement Energy

  D

  slope

  0.48 point (E )

  s

  (I )

  

f D

  0.48 0.003

  31.5 (m)

  E

  0.474 A 0,121

  0,002 B 0,120

  Chezy Coefficient With Groin

  B 0,120 0,002 Equation 19 can be used to calculation the Chezy

  C 0.118 coefficient with groin. Chezy coefficient calculation C 0,118 0,001 results are presented in table 8. D 0,117

  Table 8. Chezy coefficient with groin D 0.117 0,003

  Flow Energy Chezy

  E 0,114 Measurement Velocity slope coeffient point

  (Vt) (I f )

  (C )

  1

  (m/sec))

  A

  0.286 0.037

  5.6 Table 6. The results of the energy slope (with groin)

  B

  0.257

  B

  0.257 0.023

  6.5 Specific

  C

  0.257 Energy

  Measurement Energy

  C

  0.257 0.017

  7.7 slope point (E s )

  (I ) D

  f 0.237

  (m)

  D

  0.237 0.016

  7.4 E A 0,149

  0.228 0,037

  B 0,143

DATA ANALYSIS

  B 0,143 0,023 C 0,138

  Flow velocity through Barriers Groin Pile Vertical

  C 0,138 0,017 The Alteration of flow velocity due to resistance

  D 0,133 model groin vertical pile can be seen in the picture below. D 0,133 0,016 E 0,128

  Chezy Coefficient Without Groin

  Flow trough the channel without piles is a common condition that occur the water through a channel without barriers. Chezy coefficient calculation results are presented in table 7.

  From the picture above can be seen that the rate of directly proportional to the permeability model flow after there is a groin model is lower than the rate of groin, so it can be concluded that the smaller the flow without a groin model. This indicates that the groin permeability model groin (the distance between vertical piles serve as barriers to the flow and can reduce the piles closer), the Chezy coefficient will also the velocity. be getting smaller and the flow velocity will provide smaller. Flow velocity before and after there is model is in

  3. Coefficient of drag (Cd) value that gives the theory the pile model can be calculated by equation 22. results of theoretical research approach is about The relationship between the ratio of the velocity 0.95. without the model (Vo) and the velocity with a model (Vt.) with a dimensionless coefficient ph / d, can be seen

  ACKNOWLEDGEMENTS in the picture below.

  This study is supported by the Laboratory of Hydrology Hydraulic, Engineering Studies Center, Gadjah Mada University, Yogyakarta.

  REFERENCES

  Chow, V.T., 1997, Hidraulika Saluran Terbuka (Open Channel Hydraulics) , Erlangga, Jakarta. Raudkivi, 1996, Permeable Pile Groin, Journal of

  Waterway, Port, Coastal and Ocean engineering Figure 6. Compare the relationship Vt. / Vo research and theory with coefficient ph / d ASCE, 122.

  Raju K.G.R., 1986, Aliran Melalui Saluran Terbuka, Erlangga, Jakarta. From the picture above can be seen that the coefficient reduction is about 0,5 (research results) and Stone B.M. and Shen H.T., 2002, HydraulicResistance

  of Flow in Channels with Cylindrical Roughness

  the line of the closest relationships with the research , results is the line between the coeffiecient of drag (C )

  d Journal of Hydraulic Engineering ASCE, 128(5),

  0.9 and 1, so that it can concluded that the value of the 500 – 506 coefficient of drag (C d ) is 0.95. Coefficient of drag is Streeter, V.L., Wylie, E.B., 1988, Mekanika Fluida, Jilid influenced by the number of vertical piles, the distance

  1, Edisi 8, Erlangga, Jakarta. between piles, and the diameter of the pile. So the need

  Sujatmiko, 2006, Equivalensi Nilai Koefisien Chezy for the further research on the effect of the number,

  Pada Aliran Terhambat Batang Vertikal,

  Master diameter and permeability of the groin against the Tesis, Gadjah Mada University, Yogyakarta. coefficient drag. As can be seen in the research

  Yuwono N., 1992, Dasar-dasar Perencanaan Bangunan Sujatmiko (2006), the drag coefficient values obtained

  Pantai,

  Hydraulic dan Hydrology Laboratory, were 0.95 for the number of vertical piles and more PAU IT Gadjah Mada University, Yogyakarta. vertical piles are closer together. Therefore it can be said

  Yuwono N., 1996, Perencanaan Model Hidraulik that the drag coefficient is affected by the number of

  (Hydraulic Modelling) , Hydraulic dan Hydrology

  piles, the density of the distance between the piles and Laboratory, PAU IT Gadjah Mada University, the pile diameter.

  Yogyakarta.

  CONCLUSION

  1. Coefficient reduction is about 0,5 so the groin vertical pile can reduce the flow velocity of the flow velocity half before there is no groin vertical pile

  2. Chezy equation for flow through a vertical pile