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ME 2204 Fluid Mechanics Machinery.

Dr.V.RAMJEEDean Rajalakshmi engineering

college

- Notes on lesson-

UNIT-1

- Introduction-
- Basic conceptsproperties of fluids-
- Fluid- solid- density- sp.wt- sp.gr-.temp
- Viscosity- vapour pressure-surface

tension-compressibility-pressure measurements-

control volume-flow characteristics- - Continuity equation- energy equation-
- Momentum equation-

UNIT-2

- Flow through conduits-circular annuli-
- Boundary layer-concepts-
- Darcy-weisbach equation-
- Friction factor-Moody diagram-
- Minor losses-
- Pipes in series-
- Pipes in parallel-

UNIT-3

- Dimensional analysis-
- Buckinghams theorem-
- Dimensionless parameters-
- Models and similitude-
- Application of dimensionless parameters-

UNIT-4

- Rotodynamic machines-Theory-
- Velocity diagram- energy transfer-
- Eulers equation-cascade theory-
- turbines-pumps-
- Work done specific speed-
- Efficiencies- centrifugal pumps-
- Performance curves- for pumps turbines-

Unit- 5

- Positive displacement machines-
- Reciprocating pumps-air vessels-
- Rotary pumps-
- Velocity triangle- specific speed-
- Efficiency- -
- Performance curves-

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CLOSED CIRCUIT WIND TUNNEL

CLOSED CIRCUIT OVER VIEW

Flow visualisation tank-

DRAG OF BODIES

- Smooth corners- less drag-streamlining

Cd2.2

Cd0.6

Cd1.6

Cd0.4

Cd1.0

Flow past a cylinder-

DRAG COEFFICIENT

Vortex shedding

Cross-flow oscillating force

V

Characteristic frequency

fS frequency (Hz) S Strouhal number 0.1850.2

(depending on Re) v flow velocity (m/s) d

cylinder dimeter (m)

Potential Flow

U(q) 2U? sinq

P(q) 1/2 r U(q)2 P? 1/2 r U?2

Cp P(q) - P ?/1/2 r U?2 1 - 4sin2q

STROUHAL NUMBER

TIME EFFECT

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Add-on devices for suppression of

vortex-inducedvibration of cylinders

Typical structures interested on VIV

Wind flow on/around buildings

ALONG ACROSS

Von Karman vortex street

gt 100 m tall Buildings (Holmes)

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View of the CT model inside the tunnel

HELICAL STRAKE

A GROUP OF CHIMNEYS

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AERODYNAMIC EXCITATIONS

- PRIMARY SOURCES
- Incoming turbulence, FT
- Vortex shedding, FW
- Motion-induced forces, FM
- F(t) Fturb(t) Fwake(t) FM
- Equation of motion
- MX CX KX FG

Wind Effects on Bridges

Length 850 m 2 side span each 335 m

width 12 m Bridge deck plate girder type

07.11.40 Bridge failed (4 months after

construction)Designed to with stand 45m/s

Failed at 19m/sFrequency of vibration changed

from 37 to 14 cycles/minOscillation half an

hour13.7 m sag183 m span broke

Computation of natural frequencies-Necessary

Before failure after failure

reconstructed

Aerodynamic Coefficients

Aerodynamic Forces and Moments

Blade Planform - Solidity

- Blade planform is the shape of the flatwise blade

surface - Solidity is the ratio of total rotor planform

area to total swept area - Low solidity (0.10) high speed, low torque
- High solidity (gt0.80) low speed, high torque

R

a

A

Solidity 3a/A

Slide Courtesy NREL USA

Airfoil Nomenclaturewind turbines use the same

aerodynamic principals as aircraft

OR

Or

a

V

V

VR Relative Wind

a angle of attack angle between the chord

line and the direction of the relative wind, VR

. VR wind speed seen by the airfoil vector

sum of V (free stream wind) and OR (tip speed).

Slide Courtesy NREL USA

Wind sensitive structures

How Wind Effects are quantified?

- WIND TUNNELS 90
- FULL SCALE FIELD EXPERIMENTS 9
- COMPUTATIONAL WIND ENGINEERING
- ( Complex flow

visualisation )

Venturimeter-

a200 , Re 4104

Variation of wind velocity with time and height

Wind speed terrain topography

Design classification

Features of wind speed

- Increase in mean wind speed with height
- Turbulence intensity
- Wide range of frequencies in the fluctuations

Wind Effects on Buildings

- MODE SHAPES AMPLITUDE
- Stretched strings attached on both ends are

actually simpler - Notice that each end remains fixed in place
- You are looking at different modes of oscillation
- The relative frequencies are in the ratio 1234

Drag of cars-

- Trucks- buses- trains-
- Aerodynamic drag-
- Add-on device-
- Different shapes of cars-
- Trailer- trucks-

Rotating cylinder-

- Applications-
- 1. Flettner rotors. Sailing ships-1924-
- 2. Drag reduction of trucks-
- 3. Magnus effect- balls- spin- cricket- tennis-
- 4. Wings to increase lift- less separation-

TURBINES AND PUMPS

- 1. PELTON TURBINE
- 2. FRANCIS TURBINE
- 3. KAPLAN TURBINE
- 4. PUMPS-reciprocating and centrifugal

pump-single stage and multi stage pumps- - ( Gear pump- )

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Specific speed of turbines-

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Gear pump-

Velocity triangle-Turbine

Velocity Triangle-Pump

CONCLUSIONS

- BUILDING AERO DYNAMICS
- CHIMNEYS,TOWERS,TALL BUILDINGS.
- BRIDGES- buffeting- flutter-
- TRANSMISSION LINES.
- CABLES(MARINE).
- Drag of vehicles- POLLUTION CONTROL.
- Wind mills- power generation- turbines-
- Pumps- (reciprocating centrifugal pump)
- Airplanes- helicopter- hovercraft-

REFERENCE

- Dr.V.Ramjee Fluid Mechanics Machinery

.Eswar press 2005 - Kumar.k.l.engineering fluid mechanics. 1995.
- Hoerner.S.F.(1965) Fluid dynamic drag.
- B.Barlow,H.Rae and A.Pope(1999) Low speed wind

tunnel testing. - Streeter- Bansal- som biswas- white-

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Pelton wheel bucket-

Gear wheel-pump-