A module was developed on “Application of Fluid Mechanics in Agriculture” for undergraduate students to get a practical knowledge of Fluid Mechanics. The work was guided by Dr Sachin Mandavgane. The presentation talks about the various aspects of agriculture where fluid mechanics is applicable like types of the pump and the various types of fittings used. It also differentiates between the fluid flow in a pipe with that of an open channel. In the end, it describes the application of fluid mechanics in drip irrigation and with a short numerical which calculates the head loss.

1. Fluid Mechanics
in
Agriculture
Applications
Presented By:
Saravana Kumaran
Undergraduate Student
Chemical Engineering
Under the Guidance of:
Dr. Sachin A Mandavgane
Associate Professor
Department of Chemical Engineering
VNIT Nagpur
1

2. Pumps
• Electrical energy to convert mechanical energy to hydraulic energy
• Essential component in agriculture for irrigation systems
Parameters to be considered for pump selection:
• The flow required for the irrigation system
• Pressure required by the system after considering all the losses
occurring due to pipe, fittings, valves, elevation and emitters
• The volume and optimum abstraction rate of the water source
• Source of water
• Energy source to power the pump (diesel, electricity, petrol)
2

3. Types of Pump
3
Pump
Centrifugal Pump
End-section Pump
Reciprocating Pump
Submersible Pump
Turbine Pump
Jet Pump
Booster Pump

4. Reciprocating Pump
Displacement action with the use of a piston,
plunger or diaphragm to pull and delivery the
fluid
4

5. 5
Application in Agriculture
It is mainly used in fertilizer injector
system

6. Centrifugal Pump
“The centrifugal pumps use the principle of centrifugal force to increase the mechanical
energy of liquid and move it from suction side to discharge side ”
Centrifugal pump needs to be primed before its usage
6

7. End-Section Centrifugal Pump
• Most common type of centrifugal pump
• The pump and the motor are close-coupled with each
other and they act as single unit
• Pushing the water rather than pulling it.
• It can be installed with the or below the water level
• Efficiency of the pump decreases when they are placed
above the water surface
7
In Agriculture, it can be used as irrigation
booster pump

8. Submersible Pump
• Installed underwater along with the motor
• They need not to be primed
• Energy efficient as it just preforms the function of
pushing the water
• Are multi-stage pumps which can create high
flow rate, high pressure or both for the liquid
8

9. Turbine Pump
• The pump is submerged in water whereas the motor
is attached to pump through drive shaft is mounted
above the water level
• Application where the size of the motor is large
• Consists of multistage for giving different flow or
pressure combinations
9

10. Jet Pump
• Hybrid of a centrifugal pump which is used to lift liquid
• Uses the principle of venturi-effect to lift the liquid
• Jet pump needs to be primed before the usage
• Flow rate in jet pumps are relatively low than its pressure/head
developed
• In agriculture, Water sources whose water level varies (like lakes,
rivers, ponds)
10

11. 11
Troubleshooting in Pump

12. 12
Troubleshooting in Pump
Problem Possible Solution
No Water • Prime pump
• Head too high
• Suction lift too high
• Air leak in suction pipe
• Suction pipe clogged
Not enough water • Prime pump
• Speed too low
• Head too high
• Suction lift too high
• Air leak in suction pipe
• Wrong foot valve size
• Wrong foot valve submergence
Low pressure • Speed too low
• Air in water
• Wrong impeller diameter
• Pump wear
• Impeller damage

13. 13
High power consumption • Speed too high
• Mechanical defect
Pump stops frequently • Air pocket in suction pipe
• Suction lift too high
• Wear in stuffing box
Troubleshooting in Pump

14. Fittings used in Agriculture
14
Coupler Elbow
End Cap

15. 15
ValvesAdapter
Reducer
Tee

16. Fluid Flow
16
Fluid flow in pipe
Head loss =
4𝑓𝑙𝑣2
2𝑔𝐷
Fluid flow in Open Channel
Head loss =
4𝑓𝑙𝑣2
2𝑔DH
Where, DH =
4𝐴
𝑃

17. Close-pipe metering devices
17
Flow Meter
Insertion Meters
Pilot tube
Thermal meter
Full-Bore Meters
Venturi meter
Orifice meter
Rota meter
Venturi meter
Orifice meter

18. 18
Rota meter
Pitot Tube Thermal meter
Close-pipe metering devices

19. Open Channel Flowmeters
A common method of measuring flow through an open channel is to
measure the height of the liquid as it passes over an obstruction as a
flume or weir in the channel.
19

20. 20
• They are used in cases of small discharge
• Best weir to measure discharge in an open
channel
Discharge , Q =
8
15
2𝑔𝐶𝑒 𝑡𝑎𝑛
𝜃
2
𝐻
5
2
Where, Q is flow over V-notch weir (m3/s)
Ce is found using graph
H is the head flowing through the notch (m)
θ(degrees) is the notch angle
g is the acceleration of gravity(9.81 m/s²)
Sharp-Crested Weir (V-Notch)

21. Sharp Crested Weir (Trapezoidal)
• These weirs are trapezoidal shaped with notch
side slopes of 4:1 (vertical:horizontal)
• These weirs are commonly used for irrigation
• Used when discharge is too great for a
rectangular weir
• Discharge, Q = 3.367𝐿𝐻3∕2
21

22. Broad Crested Weir
• Typically sturdier than sharp-crested weirs
• Used in medium to large size rivers and canals
(sturdier)
• Used as a flow measurement and water level
regulator
• Necessary for flow to be in subcritical range—ensures
smooth water surface
• Flow over a broad-crested weir is highly dependent
on the weir’s geometry.
• Discharge, Q = C L Hn
Where:
Q = Volumetric flow rate
C = Constant for the specific weir structure
L = Width of the weir
H = Height of water head upstream in relation to the
weir’s crest
n = structure variant (usually 3/2 for a horizontal weir)
22

23. Reference
• https://neutrium.net/fluid_flow/flow-in-open-channels-and-partially-filled-pipes/
• https://www.agric.wa.gov.au/water-management/pump-selection-irrigated-agriculture?page=0%2C0
• https://www.irrigationtutorials.com/pumps-page-2-types-of-water-pumps/
• https://www.dpi.nsw.gov.au/agriculture/irrigation/irrigation/systems/selecting
• https://www.engineeringtoolbox.com/flow-meters-d_493.html
• https://www.slideshare.net/SalmanBaig6/fluid-flow-sb
• https://www.scientificamerican.com/article/what-is-a-pitot-tube/
23

24. Fluid Mechanics
in
Agriculture
Drip Irrigation

25. Water is directly dripped near the
root zone
Also known as trickle irrigation or
micro-irrigation or localized
irrigation
More effiecient, conserves
water, avoids runoff More initial investment

26. Typical Drip Irrigation Layout
Source: www.jains.com

27. General information required to design a
Drip Irrigation System
• Source of Irrigation water
• Crops to be grown
• Topographic conditions
• Texture of soil
• Climatic data

28. Factors affecting Water requirement
• Type of crop (crop coefficient)
• Source of water
• Weather data (Class A pan evaporation data)
• Soil type
• Area under cultivation

29. Pressure variation along a pipeline
𝑃𝑑 = 𝑃𝑢 − 𝑘 ℎ1 ± 𝛥𝑧
Where,
• Pd, Pu are pressure at downstream and upstream positions (Kpa)
• h1 is the energy loss in pipe (m)
• 𝛥z is elevation difference (m) (positive for uphill)
• K= 9.81
H1 = FH1 + M1
Where,
• F is constant; it is a f(number of outlets and method used to estimate
H1)
• H1 is friction loss (m)
• M1 is minor losses through fittings

30. For H1, Darcy-Weisbach, Hazen-Willams or scobey equation is used
H1 =
𝑘𝐶𝐿𝑄 𝑚
𝐷2𝑚+𝑛
Where,
K is friction factor that depends on pipe material
L is length of pipe (m)
Q is discharge (l/min)
D is diameter of pipe (mm)
C, m and n are constants
For drip, D-W equation is preferred.
For D-W, C= 277778; m=2.0; and n=1.0

31. For D-W equation,
K = 0 ⋅ 811
𝑓
𝑔
Where,
f is friction factor from the moody diagram
f for small diameter trickle tubing is also related to the Reynolds number
Knowing the Reynolds number (NR),

33. Computing head loss due to pipe friction in a drip lateral with online emitters
for the following data:
• 16mm internal diameter lateral
• 200m long lateral with standard online emitters spaced 1m
• Design discharge of each emitter is 1 lph
• Water temperature is 20oC
Total discharge = (1 l/hr) (200) (1hr/60min) = 3.33 l/min
V= Q/A =
3.33 𝑙/𝑚𝑖𝑛
𝜋
4
16 2
= 27.6 cm/sec
NR=
𝜌𝐷𝑣
𝜇
= 4406

34. Since NR is between 2000- 105 ,thus it is turbulent flow
f= 0.32 𝑁 𝑅
−0.25
= 0.32 4406 −0.25
= 0.0393
K = 0 ⋅ 811
𝑓
𝑔
= 0 ⋅ 811
0.0393
9.81
= 3.25 x 10-3
L= 200m = (no. of emitter) CL
From figure, CL = 0.36ft = 0.11m
L= 200 + 200(0.11) = 222m
H1 =
𝑘𝐶𝐿𝑄 𝑚
𝐷2𝑚+𝑛 =
3.25×10−3 ×277778×222× 3.33 2
162×2+1 = 2.12m
Now, F= 0.33
h1= FH1 + M1 = (0.33 x 2.12) +0 = 0.70m

35. Factor affects the drip system capacity
• Irrigation water requirement
• Daily operating hours
• Irrigation interval
• Water application
• Efficiency

36. Reference
• Irrigation & Drainage (Agriculture), NPTEL Courses
36

37. Thank you