Experiments
W. J. Devenport
Last Modified December20th, 2006
Background
The purpose of the experiments in AOE 3054 is to give you hands
on experience in organizing and conducting and documenting experimental tests.
You will get to see in real life some of the phenomena you only met in theory in
previous classes. You will get hands on experience of experimental techniques
and equipment typical of aerospace and ocean engineering applications (as well
as learning about other techniques in the classes and online lectures). Above
all, you will be encouraged to think independently about the experiments you are
given and the equipment you are using, both their capabilities and flaws.
None of the experiments have required procedures or pre-set measurement
objectives (except for experiment 5, and there are good reasons here). It is up
to you to decide on what they are. In addition, none of the experiments have
'expected results'. You are expected to open mindedly and objectively assess
your own results, their limitations, and what they mean. Your results are unique
and always have value as new and independent observations.
You
are expected to keep comprehensive documentation of each experiment you perform
in the form of a logbook. A logbook is like a detailed diary of your team's
preparation for, and activity during, an experiment. All logbooks are kept in MS
Excel. Logbooks are described in detail in
appendix 1. You will also be
asked to write full reports on three selected experiments. Reports are also
described in appendix 1, and
report writing will be covered in class. You will have a chance to revise each
report after you receive comments back from your instructor.
Lab
Organization and Preparation
Experiments are held once every two weeks (except for experiment 6 which is
done as part of instrumentation lab) and are performed in teams of 2 or 3
students. All experiments assume that you have mastered the material in the 'Basic
Concepts in Experiments' chapter of the lab manual and the
online lectures on "Statistical Data Analysis"
and "Estimating Experimental Error".
In particular you are expected to be comfortable with the concepts of
uncertainty analysis, and be ready to make formal uncertainty estimates (a.k.a.
error estimates) for all the measurements you make, and results you infer from
them. All experiments assume you are familiar with MS Excel and how to generate
a logbook.
When you have an experiment scheduled, your homework on that week
will be to prepare for it. To prepare you should
(a) Take the relevant online
lecture.
Background material for experiments 1, 2, 3 and 4 is covered in the four
online classes "Flow Visualization (Ex 1)", "Measuring Static Displacement and
Deformation in Structures (Ex 2)", "Measuring Velocity and Pressure in Fluid
Flows (Ex 3)" and "Laser Doppler Anemometry (Ex 4)". These classes provide
a broad overview of the technology in each of these areas, some of which you
then get to use in each experiment.
(b) Carefully read the relevant chapter of
the manual.
It is important to be familiar with the descriptions of the measurement
techniques and experimental set up, as well as any theoretical or descriptive
background. Experiment chapters also include a photographic equipment inventory.
(c) Meet with the other members of your
team and prepare a preliminary logbook. Your team members will be listed on
your individual schedule handed out during the introductory lab period. Together
your will need to decide on goals (try to
develop at least one goal not in the manual), on what measurements will be made,
how tasks will be assigned and what uncertainties will need to be
estimated. This information should be recorded on the preparation page of a new
logbook, generated using the logbook template (note that the template also
includes many suggestions for preparation). Your teams homework grade is
assessed on the contents of this preparation page. You must email your
instructor a copy of this logbook before coming to lab. Note that, if necessary,
you can visit the lab before your test to check on equipment if you want. Open
times for Randolph 25 (usually Monday afternoons) will be posted on the course
home page.
Exit Checklist
At the end of the experiment the team will need to complete the logbook and
give it to the instructor (transferring the logbook using one of the USB jump
drives will likely be the easiest way to do this). The last few minutes of lab
are a good time to identify the team you will be working with on your next
experiment, and maybe look over the apparatus you will be using.
For those experiments on which you will be writing reports (the first, third
and fifth experiments you do) the end of the lab period is a good time to check that everybody has everything they need. The following suggestions
may be helpful.
-
Look over the 'Recommended Report Format' section of the manual chapter. Do you have a good sense of
what the objectives in your report will be, how you will describe what
the various results mean, what the report conclusions are likely to be? There is
no requirement
that everybody in the team have the same objectives/conclusions, but it
is critical that the team discuss this before leaving the lab, so that
everyone is as well informed as possible. It is good to exchange ideas
as a team about how you are going to write the report - this will save
you a lot of time later.
-
Has the team discussed how the data could/should be further (a) analyzed and (b)
plotted, so as to make the most sense? Should the velocities/pressures/distances/strains
be normalized? Plotted against what? On the vertical or horizontal axis?
With error bars? What errors? If you are not sure about some data (why
it was taken, how it should be plotted) it is your responsibility to initiate
a team discussion (and logbook entry?) on this issue before everybody
leaves the lab.
-
Have you got all the information in the logbook you are going to need to
describe all the apparatus, instrumentation, methods, coordinate systems,
materials etc.? Does anyone in the team have ideas for items for which
model no. info, dimensions, photos are missing and need to be added to
the logbook? Are there any obvious items not in the logbook (e.g. this
measurement/tunnel/probe was lousy/great - just remember to include specifically
why)? Have someone in the team skim the manual chapter for missed items/ideas.
-
Has the team discussed how good/bad/useful the various pieces of data
you have are? You will be expected to provide error/uncertainty estimates
along with all the results presented in your report. Have you discussed
in the team how large these errors might be?
Are they calculated (or is the information needed to calculate them) in
the logbook? Can anybody think of any further error sources/confounding
factors? Is there consensus over what data is most reliable? Least reliable?
Those factors in the experiment that most limit the applicability/validity
of your conclusions?
Instructions for the
Introductory Lab
To introduce
you to the experiments part of this course and introductory lab will be held at
the start of semester. Prepare for this lab period by reading the Introduction
section of the course manual, this (overview) section and appendix 1 describing
logbooks and lab reports. Look particularly at the logbooks. Download and check
out the logbook template and sample logbook. You will need to bring to lab
-
A printed copy of these instructions.
-
Your laptop computer, containing a copy of the
logbook template.
Your lab will
be held in Randolph 25 which is in the basement of Randolph Hall where the open
jet wind tunnel is sited. The best way to get there is to go down the stairs
next to Randolph 219 to the basement and continue straight ahead through the
door at the bottom of the stairs. The door to Randolph 25 is the large double
door that will be ahead to your left.
The meeting
will include the following.
- First you will meet your teaching
assistant for the lab experiments. (You will meet your Instrumentation Lab
instructor at the first Instrumentation Lab meeting). Your TA coordinates the lab
experiment periods and will grade your experiment logbooks and lab reports.
They serve as a primary point of contact for you. Make sure you record their
information.
- You will get an individualized schedule (on paper) that
will show when you are doing each experiment and instrumentation lab period
and with whom. Make sure you understand the sheet. You will find that for each
lab you are working in a team of 2 or 3 students. Team assignments are
different most weeks.
- You, and all the other student members of the group,
will introduce themselves so you can recognize those people you will be
working with on each experiment. Everyone should confirm that their contact
information (email) on the individual schedules is correct. This contact info
is critical since it will allow students performing the same experiment at the
same time to communicate in advance to prepare for that experiment.
- Your TA will explain how the group labs work, how it is
the students’ responsibility to plan and perform the experiment, how
experiments are expected to run for the complete lab period. Make sure you
understand. Now is the time to ask questions if you don’t understand anything. They will explain
what preparation is expected for lab (a preparation logbook) and how it is
submitted (by email to them before lab time). They will also explain what a
logbook is, how and when it is submitted (by transferring to the TAs computer
at the end of lab), how it is graded and how comments are returned to you.
Logbooks, including preparation, earn team grades – i.e. all the members of a
team in attendance for the same experiment get the same grade.
- You will learn about computer use in the lab. Students
are expected to use their own laptop computers in lab. This is the time to let your TA know if you foresee any difficulties. You will need your laptop
to write your logbook, download photos from the digital cameras (you are
welcome to use your own digital cameras or camera phones as well) and, in
Instrumentation Lab, take computerized measurements.
- You will get to see how to use the equipment in the lab
that is used for experiments 1-4. This is your chance to get a really good
look at things without the pressure of an experiment to complete. You are
expected to cast a objective and critical eye on the equipment. You will have
to objectively judge (or guesstimate) its accuracy when you do these
experiments.
- Once you have been introduced to all the equipment you
should meet with the team members you will be working with during next weeks
experiment (check your schedule to see who they are and go meet them next to
that setup). Along with them you should
- Try out all the hardware for the experiment
- Try out your laptop in the lab. Can you get a wireless
connection in the lab? If not let your TA know.
- Opening the logbook template in your computer and
start a logbook preparation.
- Try out the digital camera
- Practice getting pictures from the camera into your
logbook. To avoid huge files use the camera on its lowest resolution. Also,
save the photos from the camera as JPEGs on your computer and then use
Insert>Picture in Excel, rather than importing them directly.
- Try using the USB jump drive (i) to transfer the
logbook to the computers of other team members, (ii) to your TAs laptop (as
though you were submitting it)
- Try out for yourself all the equipment in your
experiment
- Start your preparation for the experiment as suggested
in the relevant section of the course manual.
- Be sure to return all equipment and furniture to the state it was in when
you arrived (as you will need to do at the end of every lab period).