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Motilal Nehru National
Institute of Technology, Allahabad
Lab Report OnFlow Over Flat late in !ind
Tunnel"ub#itted to $ %r& A& R& au
%r& '& (& atel
"ub#itted by$ )roup *
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Overview
• Ob+ectives• Introduction•
Apparatus• Test procedure• Approach• alculations and results• o#putational analysis• Observations
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Objectives
• To e-peri#entally deter#ine velocity profile on a s#oothflat plate at various distances&
• o#putational analysis of flow over flat plate inside asubsonic wind tunnel&
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Introduction
• !hen real fluid flows past a solid body or a solid wall, thefluid particles adhere to the boundary and condition of no slioccurs&• This is the region where viscous forces are do#inant&• I#portant ter#s in boundary layer *& No slip condition.& La#inar boundary layer
/& Transition boundary layer 0& Turbulent boundary layer •. La#inar sub layer •. 1uffer layer •. Turbulent layer
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Turbulent Boundary Layer
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Growth of boundary layer over flatplate
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Test Apparatus Schematic diagram
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Test Apparatus wind tunnel! "omponents
• It is a device in for# of a long duct for producing a #ovingairstrea# for e-peri#ental purposes&
• It is used to study the effects of air #oving past solidob+ects 2 in our case it is a flat plate3&
• There are three essential co#ponents$*&4ffuser .& !or5ing section
/& %iffuser0&%riving unit
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#$ %ffuser :•. This is placed upstrea# of the wor5ing section&•. In it the fluid is accelerated fro# rest to appro-i#ately atupstrea# end to the re6uired conditions at the wor5ingsection&
&$ 'or(ing section)•. It is here that the #odel is placed is in the air strea# leavingthe downstrea# end of the effuser and the re6uiredobservations are #ade&
•. The wor5ing section consists of accessories to hold theinstru#ents and #odels and devices for facilitating the #otionof the #odel in all directions relative to airstrea# &
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*$+iffuser )
• The function of the diffuser is to recover the 5inetic energy of the airstrea# leaving thewor5ing section efficiently as possible
• Test section$ length 789&8:9&/8
,$ +riving unit)
• ower is supplied continuously to #aintain the flow through suction 2atvariable condition3&
• This is done using a fan and a #otor&• ower is given by . #otors of &;75w and .:88 rp# each&•
'elocity of inco#ing air can be controlled by ad+usting the controlvalve which further controls the suction by #aintaining the upstrea#opening&
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Accessories #! -itot Static Tube
• itot tube is a pressure #easure#ent instru#ent used to #easure fluid flowvelocity&
• "tagnation pressure 8c# - :&• For#ula used to convert reading in ter#s of velocity
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Multitube#ano#eter
Flat late
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Test -rocedure
•
The flat s#ooth surface was 5ept on a stand fir#ly, at the testsection of the wind tunnel&• The wind tunnel was set up with a itot tube, and the flat plat#ade #ovable so that analysis could be #ade at different sectionfro# the leading edge, attached to a #ulti tube #ano#eter to getthe pressure differentials&• Then the wind tunnel was turned on, and the #ano#eter wascalibrated&• The pressure differentials readings were ta5en at 0 points withthe boundary layer gradually increasing By 2distance #easuredfro# the surface3&• The pressure difference was noted carefully&• The test was repeated ad+usting the pitot tubeat 7, *8, *7, .8 c#
fro# the leading edge of the glass plate&
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Approach • !e have calculate the readings on the points2#entioned in previous slide3 and on four different velocities&
• To reduce the no& of readings we have ta5en the help of
Minitab "oftware in which Taguchi #ethod was used&• Nu#ber of para#eters$• 'elocity2u3&• %istance fro# leading edge2-3&• %istance fro# plate surface 2y3&• No& of levels used in each para#eters < 0
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"o fro# Taguchi chart
1y using above values the table provides the orthogonal arrayLC*> table &
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Taguchi orthogonal array L0#1
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.initab result• The result of Taguchi method had been validated
from Minitab Software.
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• !"# array has reduced the #$ readings %that hasto be calculated& to "# readings.
'(periment Velocity%m)s& * distance%m& + distance%m&" ", .,- .,,
", .", .,,$/ ", ."- .,,#$ ", . , .,,0- "- .,- .,,$# "- .", .,,1 "- ."- .,,00 "- . , .,,#2 , .,- .,,#", , .", .,,0"" , ."- .,," , . , .,,$"/ - .,- .,,0"$ - .", .,,#"- - ."- .,,$"# - . , .,,
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Shortcomings of taguchi
• Taguchi #ethod is #ainly used to reduced the no& ofe-peri#ents where few variables contribute significantly&
• 1ut in our e-peri#ents each of the variables have e6ualcontribution&
• "o taguchi #ethod was not co#patible with the ob+ectiveof our e-peri#ent as it was not providing the sufficient no&of readings to plot a graph different variables&
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Approach • 1ecause of non applicability of taguchi we proceeded withthe calculation of >0 readings&
• For that we have ta5en four velocities and for each velocity
there were four different - values and at each - velocitieswere calculated at different y values.
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Observations and "alculations
3,." ,." ,./ ,.- ,.1 ,.2 "." "./ ".-,
,.-
"
".-
.-
At u= 10m/s
4t (5.,-m4t (5,."m4t (5,."-m4t (5,. ,m
u/U
y/δ
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, ,.- " ".-,
,.
,.$
,.#
,.0
"
".
".$
".#
At u= 15m/s
at (5.,-m
at (5.", mat (5."- mat (5. , m
u/U
y/δ
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, ,.- " ".-,
,.-
"
".-
.-
At u= 20m/s
at (5 .,- mat (5 .", mat (5."- mat (5. , m
u/U
y/δ
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3,." ,." ,./ ,.- ,.1 ,.2 "." "./ ".-,
,.-
"
".-
.-
At u= 25m/s
at (5 .,- mat (5 .", mat (5 ."- mat (5 . , m
u/U
y/δ
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Boundary layer at different velocity
, ,.,- ,." ,."- ,. ,. -,
,.-
"
".-
.-
Boundary Layer Thickness
4t 65",m)s4t 65"-m)s4t 65 ,m)s4t 65 - m)s
x in m
δ in mm
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"omputational Analysis
• Flat plate was analyDed for the above #entioned velocitiesin Ansys Fluent& 'elocity were calculated at the above#entioned points.
Geometry)
%i#ension for geo#etry were in accordance to thelaboratory apparatus
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Geometry with domain used in CFD analysis
Meshing $Mesh was generated by siDing techni6ue with bias near the plate resulting finer #esh& !hile cowas #aintained away fro# the plate&
Eoo#ed view of #esh near plate
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Mesh %etails $tatistics !aximum "a#ue !inimum "a#ue
ke$ness ". /'3 "./,'3",
Aspect ratio /#.2$- ".,"2
%rtho&ona#ity ,.// "
"olver "ettings$• 1ecause of the turbulent flow standard 5 epsilon #odel was used wi
standard wall function for near wall treat#ent& !ith defaults constantssettings&
• 7oundary conditions: 4t inlet: velocity inlet Velocities given 8 ",9 "-9 ,9 - m)s 4t outlet: pressure outlet
auge pressure 8 ;ero Pascal.
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'elocity and ressure contoursPressure contours :
Total pressure is the summation of the static and dynamic pressure.
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'elocity and ressure contoursVelocity contours :
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'elocity and ressure contoursVelocity vector
contours :
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o#parison b@w e-peri#ental and co#putationalresults
, $ # 0 ", ",
,
,At #2 m3s
e(pcom
U
y
, $ # 0 ", " "$ "#,
,
,
At #4 m3s
e(pcom
U
y
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, - ", "- , -,
,
,
,
,
At &2 m3s
e(pcom
U
y
, - ", "- , - /,,,,,,
At &4 m3s
e(pcom
U
y
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Observations• !ith increase in a-ial distance fro# the leading edge , boundarylayer thic5ness increases &
• !ith increase in velocity ,at sa#e a-ial distance , 1oudary layerthic5ness decreases &
• Total ressure increase with increase in lateral height fro# plate &
• "tatic pressure re#ain constant throughout the do#ain e-ceptat the leading edge &
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• Than 6