Showing posts with label fluid mechanics. Show all posts
Fluid Mechanics Lab
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| Bourden Tube Experiment |
1. Dead Weight Calibrator.pptx
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To Calibrate a Bourdon Type Pressure Gauge Using a Dead Weight Pressure Gauge Calibrator
Theoretical Background
1. Calibration: To check error with comparison to some standard device is called calibration.
2. Absolute Pressure (Pabs): The pressure that is taken with reference to absolute zero is called absolute pressure, and at absolute zero there is a perfect vacuum.
3. Gauge Pressure (Pg): The pressure that is taken with reference to atmospheric pressure is called gauge pressure. It may be positive or negative depending upon whether we take (Pg) above the atmospheric pressure or below the atmospheric pressure. Gauge pressure is always measured with atmospheric pressure, that is why when gauge pressure is at atmospheric pressure it results zero.
Pabs = Patm + Pgau
Bourdon Tube Pressure Gauge:
uThe bourdon tube pressure gauge is the most common type used to measure fluid pressure because it is reliable, inexpensive and relatively simple.
uThe bourdon tube is a curved tube closed at one end, which is attached to a spring-loaded mechanism that is itself attached to the gauge’s needle.
uThe port of the gauge is attached to the location in the system where you’re measuring pressure.
As pressure increases within the bourdon tube, the metal tube starts to straighten, and as it does, it tugs on the lever attached to the needle.
Apparatus: Dead Weight Tester
Procedure:
1. Remove the piston from unit.2. Close valve V1 and open valve V2.
3. Fill cylinder with oil.
4. Now close valve V2.
5. Put piston back in position with V1 and V2 in close position.
6. Read out pressure value on gauge and compare it with theoretical results.
7. Repeat the experiment by adding weights.
Reynolds Number
The Reynolds number is undoubtedly the most famous dimensionless
parameter in fluid mechanics. It is named in honor of Osborne Reynolds (1842–1912), a
British engineer who first demonstrated that this combination of variables could be used as a criterion
to distinguish between laminar and turbulent flow. In most fluid flow problems there will
be a characteristic length, and a velocity, V, as well as the fluid properties of density, and
viscosity, which are relevant variables in the problem. Thus, with these variables the Reynolds
number
arises naturally from the dimensional analysis. The Reynolds number is a measure of the ratio of
the inertia force on an element of fluid to the viscous force on an element. When these two types
of forces are important in a given problem, the Reynolds number will play an important role. However,
if the Reynolds number is very small xthis is an indication that the viscous forces
are dominant in the problem, and it may be possible to neglect the inertial effects; that is, the density
of the fluid will not be an important variable. Flows at very small Reynolds numbers are commonly
referred to as “creeping flows”. Conversely, for large Reynolds
number flows, viscous effects are small relative to inertial effects and for these cases it may be
possible to neglect the effect of viscosity and consider the problem as one involving a “nonviscous”
fluid. This type of problem is considered in detail in Sections 6.4 through 6.7. An example
of the importance of the Reynolds number in determining the flow physics is shown in the figure
in the margin for flow past a circular cylinder at two different Re values
parameter in fluid mechanics. It is named in honor of Osborne Reynolds (1842–1912), a
British engineer who first demonstrated that this combination of variables could be used as a criterion
to distinguish between laminar and turbulent flow. In most fluid flow problems there will
be a characteristic length, and a velocity, V, as well as the fluid properties of density, and
viscosity, which are relevant variables in the problem. Thus, with these variables the Reynolds
number
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| Reynolds Number |
arises naturally from the dimensional analysis. The Reynolds number is a measure of the ratio of
the inertia force on an element of fluid to the viscous force on an element. When these two types
of forces are important in a given problem, the Reynolds number will play an important role. However,
if the Reynolds number is very small xthis is an indication that the viscous forces
are dominant in the problem, and it may be possible to neglect the inertial effects; that is, the density
of the fluid will not be an important variable. Flows at very small Reynolds numbers are commonly
referred to as “creeping flows”. Conversely, for large Reynolds
number flows, viscous effects are small relative to inertial effects and for these cases it may be
possible to neglect the effect of viscosity and consider the problem as one involving a “nonviscous”
fluid. This type of problem is considered in detail in Sections 6.4 through 6.7. An example
of the importance of the Reynolds number in determining the flow physics is shown in the figure
in the margin for flow past a circular cylinder at two different Re values
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