lab report
ThermalFluid Systems class, i have to make a lab report. the lab is (( Wind Tunnel Background )). i have uploaded the PDF File. Also, I have uploaded the (( Lab Report Template)) which you have to follow the steps. Also, I have uploaded the (( DATA TABLE )) that you need . aLSO, TO MAKE SURE THAT YOU HAVE ACCESS, AFTER YOU GOT IT I WILL SEND TO YOU THE LINK FOR THE (( DATA TABLE ))
Title of Experiment
By
Alex Bell
Bert Einstein
Tommy Edison
Mike Faraday
Date of Experiment: October 1, 2007
Date Turned In: October 17, 2007
For
ME125: Engineering Measurements
Professor Marbach
Abstract
The abstract is a brief summary of the entire experiment. It should include at least one sentence summarizing each of the following areas: background, objective, setup, results and conclusions. The abstract should stand alone, so do not refer to any figures or references.
1. Introduction and Background
Discuss the theory behind the lab. Make sure to address the physical laws that apply and any approximations or assumptions that can be made. Write the equations and EXPLAIN them completely and clearly. Identify all properties that must be measured (the properties come directly from the physical laws). You do not need to explain HOW you will measure these properties yet, that’s in the Experimental Setup and Procedure. Any other appropriate background or history should go here.
2. Objective
Get directly to the point, start this section with something like… “The primary objective of this experiment was to …” Secondary objectives included the following:
1. blah
2. blah
3. blah
3. Experimental Setup and Procedure
Provide a simplified schematic and a photograph of the actual setup. Discuss the relationship between the simplified system and actual device. After providing an overview of the system and connecting it to the background discussed in Section 1, explain how each property identified in Section 1 will be measured, calculated or assumed. Also carefully describe the procedure that was followed to conduct the experiments.
4. Results and Discussion
Provide a general overview of the results that will follow. Then, break down the results into subsections. Discuss the calculation/solution procedure, but put sample calculations in the appendix. Carefully think about the best way to present the data. Use tables, figures, contour plots or other graphical representations to present the results and clearly discuss the MEANING of the results. Discuss EVERY figure or table that is presented. If it’s not worth discussing, it’s not worth putting in the report! Were your results expected or are there significant differences from your expectations. Where did the errors come from? Did you make poor assumptions (if so which one(s)), were measurements inaccurate, etc.
5. Conclusions
Like the objectives, get right to the point. Provide one, overarching conclusion (ie. “The Sac State Wind Tunnel is HellaRad …”). Then, provide more detailed conclusions.
References
Doe, John, “Forces on a cylinder in viscous flow,” Journal of Cool Stuff, Vol. 5, Issue 6, pp. 111, 1776.
Appendix A: Sample Calculations
Appendix B: Raw Data
Appendix C:…
WindTunnel Background
Important Dimensions Diameter of the cylinder � = 0.75 �� Length of the cylinder � = 12 �� = 1 �� Height of the test section ” = 12 �� = 1 ��
IMPORTANT NOTE!!!
I HIGHLY recommend that you do all of the lab calculations in SI units, NOT British units!
Velocity Profile
• How to get position into units of in
The data acquisition system for the wind tunnel gives the position of the pitot tube in units of
volts. You can see this in your excel files for the velocity profiles. To get the position in terms of length
and not voltage, we will use a linear relation. Taking your minimum value in volts and maximum value in
volts, match them with the minimum value in height, 0 in, and the maximum value of height, 12 in,
respectively. From there, you should get a linear equation relating the two quantities. Here is an
example of how you would get the equation:
Note: This is just an example! Your equation will be different!
• Calculating the velocity from the pressures
You will see in the excel files for the velocity profiles that there are two different pressures: Diff
P and Total P. You will need to use Diff P to find the velocity. The total pressure could be used to find
the changes in density throughout the velocity profile, but we are interested in finding the velocity
profile and the density changes will be negligible. By understanding how a pitot tube works, the
differential pressure is related to velocity through Bernoulli’s equation.
y = 0.745x + 2.5
0
2
4
6
8
10
12
14
0 5 10 15
P
o
si
ti
o
n
i
n
u
n
it
s
o
f
in
Position in units of V
Example of Relation between V and in
Series1
Linear (Series1)
#$ + #$ + $& ‘($& + ‘)*$ = #& + $& ‘(&& + ‘)*&
‘(#$ + $& ‘($& + ‘)*$ = #& + $& ‘(&& + ‘)*&
+ ‘)*$ = #& + #$ + $& ‘($& + ‘)*$ = #& + $& ‘(&& + ‘)*&
‘(&& + ‘)*&
It is a stagnation point at the tip of the pitot
tube, so the velocity is equal to zero. Assuming
the difference is height is negligble, Bernoulli’s
equation reduces down to
∆# = 12 ‘( &
( = ,2∆#’
Now use this equation to find the velocity for every pressure under the “differential
pressure” column in the velocity profile excel files.
Now plot the four velocity profiles and explain their behavior.
Calculating the Drag (./01) and Coefficient of Drag (23)
• Converting the manometer pressure readings
As noted in the lab, the manometer pressure readings are opposite the real pressure. When the
pinpoint hole on the cylinder is facing the flow (i.e. the stagnation point), the pressure should be
a maximum, however on the manometer, it was a minimum. To convert the manometer data
into proper pressure data, you must do the following:
1. Take the absolute value of all of the data
2. Find the maximum manometer value.
3. Subtract all of the values from the maximum pressure value.
As an equation, you want to do the following:
For a pressure reading “S”: “converted pressure reading S” = maximum manometer value − pressure reading S
By doing this, you will get the proper pressure behavior around the cylinder.
Now you will plot the pressures around the cylinder and explain the behavior.
#<=>?@>=AB@
(CDEE <=DE>F
To pressure
instrument
• Calculating the Drag and Drag Coefficient
By integrating the xcomponent of the surface pressure on the cylinder over the surface area,
the resultant xcomponent of the force can be obtained:
GH = I #< JKLMNO
entire surface area.
Be sure to convert the #< value from inches of water, which was the unit of measure of the manometer, to Pa or Psi. Here is how to convert inches of water to Pascals:
#< R#ST = ')ℎ = ')(#< R�� "&WT) Note that ℎ, or as I wrote above #< R�� "&WT, is the inverted manometer water height.
‘ ≈ 1000 Z?F[ and ) = 9.8 F<^
Now, since our experiment was taken in discrete measurements, we have to use approximation
methods to evaluate the above integral. G_D>? = #H NO< Now we need to find NO< . The surface area of a cylinder is defined as: O< = 2`a� Since there are 72 pressure taps (each 5° apart) on the sphere, that means that there are 72 segments (a
segment is the arc length between two pressure taps). However, since we took pressure measurements
in 10° increments, our differential surface area can be described in the following way:
NO< = �K�Sb Lca�SJd SadS K� S Jeb��Nda# gadLLcad �SgL hdSLcadN = 2`a�36 Then the force equation becomes the following. At each pressure tap, the force acting on the cylinder is G_D>? = #H NO<
G_D>? = (#< JKLM) k2`a�36 l Thus the total drag on the cylinder is the following:
G_D>?,=B=>n = o #<,A JKLMA k2`a�36 l pq
Ar$
Now using the definition of drag:
G_D>?,=B=>n = Gs = 12 t_D>?'(CDEE <=DE>F& OCDB@=>n
Rearranging the above equation to solve for the coefficient of drag, you can calculate t_D>?:
t_D>? = ts = G_D>?,=B=>n12 ‘(CDEE <=DE>F& OCDB@=>n
Where U is the velocity and A is the projected area NOT the crosssectional area of the cylinder. When
you look at the cylinder from the flow’s perspective, the cylinder appears to be a rectangle. As a result,
the projected area is: OCDB@=>n = ��
Where D is the diameter of the cylinder and L is the length.
In the calculation of the drag and drag coefficient, you must use the free stream velocity, which was
found by using the pitot tube upstream of the cylinder.
• Comparing your ts value to theoretical values
In order to properly compare your data to theoretical data, you must calculate the Reynolds
number, a dimensionless fluids parameter.
uds = ‘(�v
Where V is the free stream velocity and D is the diameter of the cylinder. Then after calculating this
quantity, you can use the chart below to see the ts value that you should have gotten for that Reynolds
number.
Figure 1: Drag coefficient as a function of Reynolds number for a smooth circular cylinder and a smooth sphere. [1]
Make sure you use the curve for the smooth cylinder, NOT the smooth sphere.
Compare your calculated ts to the theoretical ts and explain the results.
Some other helpful illustrations from a fluid dynamics book:
Figure 2: Typical flow patterns for flow past a circular cylinder at various Reynolds numbers as indicated in Figure 1. [1]
Figure 3: Character of the steady, viscous flow past a circular cylinder: (a) low Reynolds number flow, (b) moderate Reynolds
number flow, (c) large Reynolds number flow. [1]
Figure 4: A comparison of theoretical (inviscid) pressure distribution on the surface of a circular cylinder with typical
experimental distribution. [1]
Figure 5: Inviscid flow past a circular cylinder: (a) streamlines for the flow if there were no viscous effects, (b) pressure
distribution on the cylinder’s surface, (c) freestream velocity on the cylinder’s surface. [1]
Figure 6: Explanation of boundary layer behavior around a cylinder. [1]
References
1. Munson, Bruce R. et al. Fundamentals of Fluid Mechanics, Fifth Edition. Ames, Iowa: John Wiley
& Sons, 2006.
Wind Tunnel
By
Jonathan Jaquias
Federico Venturi
Mubashir Khan
Georgia
(other guy)
Abstract:
1. Introduction and Background:
ν = √ ρair2ΔP
Utilizing Bernoulli’s equation for energy balance and referencing all of the
air flowing before the pitot of stagnation as zero and considering the height as
negligible; we were then able to reduce bernoulli’s equation into velocity (v) being
equal to the square root of two times the pressure (P), at every increment, divided
by the density ( ) of air.ρair
In analyzing the drag force and coefficient of drag
The pressure readings first must be converted to true pressure readings due to the
stagnation point resulting in a minimum pressure at the stagnation point.
From the projected area of the front cylinder (A=D*L), and the total drag
force (F) which is calculated using the manometers free stream velocity(pitot tube
upstream of cylinder), along with the density of air( ) the coefficient of dragρair
can be obtained through the below equations.
CD =
FTotal Drag Force
ρν A2
1 2
Free Stream Frontal
Reinholds number is utilized to compare the theoretical values of the drag
coefficient using the stream velocity (V) and the diameter of the cylinder (D) along
with the density of air ( ) and dynamic viscosity (μ).ρair
2. Objective:
The Primary objective of the lab is to obtain the relative pressure readings
from the manometer at 5 degree increments on the cylinder. The secondary
objective is to obtain the drag force readings at each pressure tap increment and
obtain the summation of all drag force readings. The third objective is to calculate
the drag coefficient using the free stream velocity of the pitot tube. Lastly, the
final objective is to compare theoretical values of drag coefficient through
Reinholds number which was found using the diameter of the cylinder and
averaged pressure readings.
3. Experimental Setup and Procedure:
Summarize steps of procedure and how we recorded each value
4. Results and Discussion:
Describe each graph
5. Conclusions:
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