Download - Momentum Fluida
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8/13/2019 Momentum Fluida
1/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 1Autumn Quarter
Transport Phenomena
Lab 4
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8/13/2019 Momentum Fluida
2/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 2Autumn Quarter
Topics to be covered
Transport Phenomena
Energy
Mass Momentum (fluid)
Viscosity and rheology
Falling ball viscometers examine the effect of viscosity on object falling through
the fluid.
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8/13/2019 Momentum Fluida
3/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 3Autumn Quarter
Transportation applications
Energy
Fighter jet cooling
Radiators
Air conditioners Mass
Intracellular transfer
Momentum (i.e. fluid)
Pumps
Airplane flight
Water flow
Applications all over
engineering:
Mechanical
Chemical
Aeronautical
Biomedical
Civil
Industrial Systems
Materials Science
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8/13/2019 Momentum Fluida
4/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 4Autumn Quarter
Energy and Mass Transport Mechanisms
Energy Transport
Mass Transport
Flow Direction
N2 O2valve
Difference in temperature is
the driving force for heat
transfer.
Difference in concentrationis the driving force for mass
transfer.
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8/13/2019 Momentum Fluida
5/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 5Autumn Quarter
Momentum (Fluid) Transport
Flow types
Turbulent flow
Laminar flow
Velocity Gradient
Viscosity
Reynolds Number
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8/13/2019 Momentum Fluida
6/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 6Autumn Quarter
Momentum transport Mechanisms
If pressure drop is small across the object, fluidmotion is smooth and transfer is molecular. Thatis, momentum transfers from molecule tomolecule through the fluid. Fluid flows in layers
Difference in pressure is the driving force,causing fluid to flow
Laminar flow ( Molecular)
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8/13/2019 Momentum Fluida
7/17
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8/13/2019 Momentum Fluida
8/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 8Autumn Quarter
Coefficient of Viscosity ()
Under conditions of laminar flow, the force (F) required tomove a plate at constant speed against the resistance of afluid is proportional to the area of the plate (A) and to thevelocity gradient (dVx/dy) perpendicular to the plate.
F = A (dVx/dy) (or)
= (dVx/dy) where, is shear stress per unit area
Newtons Law of Viscosity
Unit (SI): kg m-1 s-1 (preferred) or Pa-s
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8/13/2019 Momentum Fluida
9/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 9Autumn Quarter
Reynolds Number (Re)
Re is a dimensionlessparameter that describes flowand is defined as
Re = DV /
D: Characteristic length scale (such as diameter of a
pipe, diameter or length of a body) (m)
V: Characteristic Velocity (m/s)
: Density of fluid (kg/m3)
: Viscosity of fluid (kg/ms)
Ratio /is called Kinematic Viscosityof fluid,
usually expressed in (m2/s)
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8/13/2019 Momentum Fluida
10/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 10Autumn Quarter
Re and Critical Velocity
At a critical value of Re, flow will change from
laminar to turbulent - the flow velocity at which
this occurs is called the critical velocity.
Critical Re changes based on application
there are no analytical methods for predicting
critical Re available due to complex origins of
turbulence.
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8/13/2019 Momentum Fluida
11/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 11Autumn Quarter
Re and Critical Velocity
For fluid flow throughpipes, critical Re 2000
Re < 2000 for
laminar Re >> 2000 for
turbulent
2000 < Re < 4000 istransition region
laminar or turbulent
Critical Re changes fordifferent flow types:
1 for object movingin a fluid (this lab)
1000 for flowbetween parallel walls
500 for flow in awide open channel
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8/13/2019 Momentum Fluida
12/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 12Autumn Quarter
Falling Sphere Viscometer
Requires a transparent vertical
tube filled with test fluid and the
object (a sphere).
When object starts to drop (free
fall), it accelerates downward till itreaches a maximum velocity
called terminal velocity (Vt).
Terminal velocity affected by
Density, viscosity of the fluid Shape, size, density of object
Measure terminal velocity.
Vt
Assume:Sphereattainsterminal
velocityhere
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8/13/2019 Momentum Fluida
13/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 13Autumn Quarter
Falling Sphere Viscometer
Sphere at terminalvelocity (Vt)
Fd = Fg Fb
Fg
Fd Fb
When body attains terminal velocity,
body experiences no acceleration
forces acting on the body are in
equilibrium.
Magnitude of terminal velocity should
result in a low Recritical Re is
about 1.
Gravitational Force (Fg) depends on:
Density of sphere
Radius of sphere
Acceleration due to gravity
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8/13/2019 Momentum Fluida
14/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 14Autumn Quarter
Falling Sphere Viscometer
Force due to buoyancy (Fb) depends on:
Density of fluid
Radius of sphere
Acceleration due to gravity Drag force (Fd) is the resistance of the fluid to
motion of body given by Stokes law, depends on:
Absolute viscosity of fluid
Terminal Velocity (Vt)
Radius of sphere
Fg
Fd Fb
Fd = Fg Fb
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8/13/2019 Momentum Fluida
15/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 15Autumn Quarter
Falling Sphere Viscometer
Vt
Design should consider:
Wall effects
Ratio of diameter of sphere todiameter of cylinder should beas small as possible.
Bottom effectsTo ensure minimal error, westop recording before aspecific height from thebottom of cylinder.
Terminal velocity of object
through fluidShould yield Re
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8/13/2019 Momentum Fluida
16/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 16Autumn Quarter
Lab Report Requirements - in pairs
Analysis and discussion of the two fluids at your tableplus a third fluid from the lab website
Position/time plots with trendlines
Analysis and discussion of the velocities from eachgroup in the class
Comparison of group data against class
Determination of Reynolds number and viscosity foreach fluid
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8/13/2019 Momentum Fluida
17/17
Engineering H191 - Drafting / CAD
The Ohio State University
Gateway Engineering Education Coalition
Lab 4 P. 17Autumn Quarter
Todays Goals
Collect data using the LabVIEW application
Save at least 6 .csv files 3 per fluid using the two
fluids at your table
Collect 6 sample Vt(3 per fluid) and report to the
front, as described at end of procedure:
Open your .csv files and determine Vtby fitting
trendlines and calculating total velocity