Subject: Seeking Solenoid Analysis & Design Tools (software) & Literature
From: "David A. Westman"
Date: Fri, 13 Dec 1996 06:19:55 -0800
Looking for
- computer software tools
- books, articles, other literature
to provide info on analysis and design of simple solenoids.
1st interest is in analysis of basic performance characteristics:
i.e., generating force vs. stroke curves for a set of dimensional,
material, etc. parameters (and evaluating effects on performance of
changing these).
Also interested in analyzing other aspects such as heat rise, transient
characteristics, residual magnetism, etc.
Any suggestions, leads, or experiences? Thanks.
Subject: After the Glory Days
From: Richard Uher
Date: Fri, 13 Dec 1996 09:10:32 -0500
After the Glory Days...
A HISTORY OF LAND TRANSPORTATION IN THE IEEE: FROM THE AGE OF
ELECTRICITY TO THE COMPUTER AGE
by Keith Uher, Carnegie Mellon Press 1988; 100 pages; price $24.95.
Library of Congress Catalog Number 87-73140
ISBN 0-88748-071-3
Copyright© 1987 Keith Uher
A History of Land Transportation in the IEEE is available from the Rail
Systems Center, 2013 Country Club Drive, Mount Vernon, PA 15135. The
cost is $24.95 which includes postage and handling. Please
enclose a check with your order. To reserve your copy for ten days
e-mail: urichard@lm.com
About 90 copies left.
Please visit the Rail Systems Center at URL:
http://www.lm.com/~urichard/rsc_1.htm
We sponsored the research that produced the book.
Synopsis of the book:
Many books and articles have been written on nearly every aspect of
early railroads and their effect on the development of the United
States. But as one gets closer to the present, fewer writings on this
subject can be found. There seems to be two main reasons for this lack
of scholarship. First, the days of the steam railroads were very
romantic - filled with heroic and villainous characters and landmark
events.
And second, by the early part of the century, the automobile had grabbed
much of the attention away from the railroads. Despite the few writings
on railroads after the glory days, transportation was and is very
important to the United States and could become even more important in
the future. And an understanding of the recent past is very important to
gain insight into the future.
This book examines one small span of the history of modern railroads.
Specifically, it examines the last century of electric railroads (both
urban and mainline) from the point of view of the main electrical
engineering society: the Institute for Electronic and Electrical
Engineers (IEEE). The major events and problems of electric railroads
are examined, from the development of the first trolley system to the
present experimentation with magnetic levitation. It is hoped that this
publication will spur other, more detailed studies of this very
important subject.
Subject: Re: FEA theory needed for FEA software?
From: rizzo@hogpb.ho.att.com (-A.RIZZO)
Date: 12 Dec 1996 16:21:57 GMT
In article <58p0a2$gha@usenet.rpi.edu>,
Mark Beall wrote:
>
>Using today's commercially available software, I agree. However, given
>the idealized mathematical description (not a finite element model)
>it is quite possible to write software to automatically solve that
>description to an accuracy dictated by the engineer. With such software
>there would be no need for the engineer to understand what technique
>is used (I believe that this is the "golden fleece" that Tony Rizzo
>referred to).
I'm afraid that the golden fleece to which I referred is much
more golden than this. See below.
>It would still be the engineers responsiblity to
>make sure that he modeled the correct problem, he still would have
>to do the engineering.
>
>Mark Beall
At conferences, I have had and have overheard numerous discussions
with managers, executives, and management consultants who think
that automated analysis software can replace the engineer (I said
the engineer, not the dedicated FE analyst). Inevitably, the
objective of these folks has been to save money, by replacing engineers
with "designers" who are paid lower salaries. This is the very
dangerous golden fleece that scares the dickens out of me.
It scares me, because I know that it's only a matter of time before
software suppliers create software that appears to be automated to
the extent that the software defines the problem, does the analysis,
and interprets the results. I already know the inevitable outcome of
having such a package in the hands of a person who lacks experience
as an engineer (I said experience, not formal schooling).
I also know that even experienced engineers with such software
can never eliminate the need for dedicated analysts. Just as
they do today, most engineers who design products will do a perfectly
good job solving 90% of the problems 90% of the time. But with
uncanny regularity they all run into the unknown. The dedicated
analysts are the folks who have the tools and the experience to
explore the unknown.
It's a fact of life that not exploring the unknown is not an
option for a company that is trying to bring new products to market.
Creating and marketing new and truly innovative products requires
delving into new territory with greater frequency. Therefore,
as the design/analysis software packages become more powerful
and more widespresd, the process by which the technical
unknown is explored becomes the constraint for many companies.
I use the word constraint in the sense that Goldratt uses it.
A constraint is the one thing that prevents a company from making
more money.
I use the term golden fleece, because such automated analysis
packages cannot overcome the constraint that I just mentioned.
If a company is constrained by the ability of its engineers to
make truly new designs work properly, and if automated analysis
packages can improve only those parts of the design process that are
non constraints, then automated analysis packages cannot have a
significant, positive impact on the bottom lines of those companies.
I'm very sorry to say that I've seen an example of this already. I
watched helplessly as a friend used one such package to design a new
product. He did the entire design, from beginning to end, using
the package. He used the built-in mesh generator and the built-in
solution module to do a number of FE analyses of the components of
the product. The pictures looked beautiful, and the whole design
process was blindingly fast. But, apparently, my friend ran headlong
into some unknown physics (unkown by him). The prototype failed its
field trials miserably, and the project was canceled.
However, such software packages can have a slight positive
impact on the bottom line. By using them, engineers do become
more efficient at the non constraint tasks. As a result, a
company will need fewer such engineers. One design engineer
who is proficient with such a software package can do the work
of two or three. Therefore, the company can survive with
fewer design engineers.
If the company can survive with fewer design engineers, and if
the mentality of cutting staff to generate profits does not
change (I see no indication that it will change), then some
design engineers will lose their jobs. Is this a problem?
That depends on who you are. If you are a software supplier
who sells such automated packages, then it's not a problem.
It's an opportunity. If you're an employer, and if your defacto
goal is to minimize operating expenses, then it's an opportunity
to make more progress toward your erroneous goal. If you're
a design engineer, then it might be a problem.
Nevertheless, the arrival of such software packages is inevitable.
It's happening already. Hmm! How long has it been since
I updated my resume?
Tony Rizzo
Subject: Re: FW: Warning of a New Internet Virus - NOT
From: Paul Skoczylas
Date: Fri, 13 Dec 1996 13:19:20 -0700
Katarina Weinberg wrote:
> At best, more people are aware of all the chain letters and Trojan
> viruses that keep showing up.
Actually, Viruses and Trojan Horses are completely different entities
(so you can't have a "Trojan virus").
A virus is a program that lives inside an executable, and duplicates
itself and infects other executables. The executable that is infected
may appear to act normally, but at some point may behave badly (and
erase your hard drive, for example). A computer virus is just like a
real virus, which is actually some DNA in a protein shell, that infects
living cells, and duplicates itself inside those cells to spread to
other cells.
A Trojan Horse is a program/executable on its own. It claims to be one
thing, when in reality it is something else. A good example is the
PKZIP scare a couple of years ago. Someone wrote a destructive program
(I forget what it did, exactly--something like erasing a hard drive) and
uploaded it to various sites, pretending it was the next version of
PKZIP. People, anxious to always have the lastest version, downloaded
it and suffered the consequences. A Trojan Horse does not duplicate
itself inside other executables like a virus does. (A virus could
infect a trojan horse executable, however...)
-Paul
Subject: University Level Design for Recycling Competition
From: Hugh Jack
Date: Fri, 13 Dec 1996 14:14:18 -0500
This may be of interest to students and faculty doing design work.
You can get more details at,
http://www.engineer.gvsu.edu
------------------------------SNIP----------------------------------
THE FOURTH ANNUAL PADNOS DESIGN
COMPETITION
COMPETITION INFORMATION AND GUIDELINES
The Padnos Competition is an annual competition which recognizes innovative senior design
projects in engineering which are environmentally responsible. This competition is sponsored by
the Louis and Helen Padnos Foundation and by Grand Valley State University, in cooperation
with the American Society of Mechanical Engineers. The intent of the competition is to be
compatible with the typical senior engineering design experience which is included in every
ABET accredited engineering program. To be considered, a project must have a major focus
on an innovative engineering approach to solving a problem in an environmentally
responsible manner. The particular environmental problem for the project must be addressed
in the report.
AWARD STRUCTURE
A video presentation of the three winning entries is distributed to the participating institutions
during the academic year following the competition. This video also recognizes all of the
participating institutions.
Grand Prize (1)
The cash award associated with the grand prize consists of a $6,000 grant in the name of the
project faculty supervisor. The funds are to be distributed as follows: Student Team - $2,000;
Institution - $4,000 (use of the institution award is to include sending the winning team to the
award presentation as necessary). In addition, the judging by the Padnos Competition judges
constitutes the peer review for
The Technology Journal of the Franklin Institute. Grand Prize entries are invited to
submit a paper to this journal based on the project.
Honorable Mentions (2)
The cash award associated with each honorable mention consists of a $2,000 grant in the name
of the project faculty supervisor. The use of this award is to include sending at lease one
member of the winning team to the award presentation as necessary.
POTENTIAL PROJECT TOPICS FOR SUBMISSION INCLUDE (but are
not limited to)
Product or Process Design for Recycling Design for Disassembly
Design for Source Reduction and Waste Minimization Life Cycle Assessment Based Design
Design for Energy and/or Resources Conservation
JUDGING CRITERIA
The contest entries shall be judged based upon:
Scope of Potential Environmental Impact Originality of Design
(broadly and specifically) Potential for Implementation
Engineering Analysis Quality of Submission
Economic Feasibility
COMPETITION ENTRY REQUIREMENTS
1. Individuals or teams may enter. At least one team member must be enrolled in a senior
engineering design experience. Interdisciplinary teams are welcome.
2. To be considered, the project being submitted must have been completed in the academic
year immediately preceding the entry submission deadline.
3. Project submissions must be prepared in English and include:
A completed Entry Cover Sheet
A completed Address Information Form
A written Project Report
An Executive Summary of the project (approximately 1000 words)
Either
A video presentation (approximately 10 minutes and not more than 15 minutes)
or
A demonstration poster and script (poster size when displayed not exceed 36"x48")
COMPETITION TIME-TABLE
As this competition is designed to accommodate the various academic calendars and senior
project approaches, the intent to participate form deadline is flexible. Submission of these forms
is used to constitute the judging panel each year. The recommended schedule for submissions
is:
October 1, 1996 (flexible) - Submission of Intent to Participate Forms (Fall Term Projects)
February 1, 1997 (flexible) - Submission of Intent to Participate Forms (Winter Term Projects)
May 15, 1997 - Submission of Entries (extensions possible by special request)
September, 1997 - Presentation of Awards at the ASME Technical Design Conference
RECOMMENDED REPORT FORMAT
* Clear statement of the problem being addressed
* Concise summary and conclusions (approximately 10 pages)
* Statement of how the Padnos Competition criteria are addressed
* Appendices presenting supporting material
RECENT WINNING ENTRIES
Dairy Waste Management Treatment System Univ. of Tenn., Knoxville 1996 Grand Prize
Winner
Construction Materials from Pulp-mill Solid Residuals Seattle University 1996 Grand Prize
Winner
Supermilage Drivetrain Optimization Cedarville College 1996 Honorable Mention
Collapsible Truck Wind Deflector Cedarville College 1995 Grand Prize Winner
Pre-heating Water with Refrigerator Waste Heat Michigan State Univ. 1995 Honorable Mention
Sidewall Removal Mechanism for Recycling of Tires Univ. of Victoria 1995 Honorable Mention
Today's Newspaper - Tomorrow's Construction Material Montana State Univ. 1994 Grand Prize
Winner
Steel Removal from Radial Tires: Rubber Recycling North Dakota State Univ. 1994 Honorable
Mention
Optimization of the Beverage Vending Machine Michigan State Univ. 1994 Honorable Mention
OTHER RECENT ENTRY TOPICS
Conversion of waste materials to new products
Manufacturing process re-design to avoid use of environmentally unacceptable materials
Generation of energy from renewable resources
New techniques for clean-up of hazardous material spills
Innovative control techniques for energy conservation in heating & cooling systems
Waste prevention or minimization through innovative scheduling methods
Innovative techniques for soil remediation
Innovative methods for waste treatment
FOR MORE INFORMATION
Entry forms and additional information are available via the internet or by request. The internet
address for the Padnos Competition Home page is:
http://engineer.gvsu.edu/pse-info/97-info.htm
Information is also available from:
Paul D. Plotkowski, Ph.D.
Padnos Competition Coordinator
301 W. Fulton
Grand Rapids, MI 49504
Padnos School of Engineering Telephone (616) 771-6750
Grand Valley State University FAX (616) 771-6642
E-Mail Internet: plotkowp@gvsu.edu
------------------------------SNIP----------------------------------
Subject: Re: hvac for small house
From: gt5458c@prism.gatech.edu (Wesley A. Younger)
Date: Fri, 13 Dec 1996 13:07:00 -0500
In article <32b5d5e3.33983657@news.zip.com.au>, waiwhite@zip.com.au (Ian
A. White) wrote:
> In article <32a8aae0.869765913@newshost.ccsi.com>,
> larry@ccsi.com (Larry Marshall) wrote:
>
> > I am building a small one bedroom house (640 sq ft) in central TX.
> > Central A/C & Heat seems like overkill. Am considering a wood stove
> > for heating but would like recomendations for A/C
>
> Certainly look at a reverse cycle air conditioner (heat pump). You
> will need to consider your local winter temperatures, and depending on
> how cold it gets, you might need backup heating. Having said this,
> the unit I have installed advises you to clear snow from the outdoor
> unit (it is a split system) to maintain operating efficiency, so it is
> fully intended for operation in such environments. Even if you do
> install backup heating, from an energy consumption point of view, it
> would still pay you to use the heat pump for your normal heating, only
> going to the backup system when conditions demand it. Why? Well with
> an up to 300% efficiency it is hard to go past it.
What he may not be considering, being an Australian, is that we can get
dirt-cheap natural gas service almost anywhere in the United States.
Having a heat pump really depends not just on your local winter
temperatures but also your local gas and electric rates. In Tennessee,
where TVA is still selling socialist electricity (not that I'm against
socialism, but that's what it is) at 5 cents per kWh and gas is a bit more
than usual, heat pumps are abundant. In Los Angeles, despite never needing
backup heat at all because of the weather, you won't ever find a heat
pump, because electricity is 11 cents per kWh (it's about that high here
in Georgia, from what I've heard) and gas is cheap. In fact, in sixteen
years of living in Los Angeles, I not only never saw a heat pump, but I
also never saw an electric water heater.
> From an energy, and cost point of view, local figures indicate that
> wood stove heating is the least efficient form of heating. Even the
> newer "improved" ones have major problems with pollution. Some of our
> worst winter pollution is as a direct result of the use of wood
> heaters. It is now difficult to get permission to install one in
> certain local government areas.
Looks to me like they can't get gas where he lives. Wood heat?
Sounds like that's his only alternative to a heat pump. They aren't
terrible, and are superior in some places (like in Tennessee with TVA
electricity) but certainly are more expensive in some areas.
Subject: 1997 Fiber Optic Sensors Course
From: ericudd@aol.com (EricUdd)
Date: 13 Dec 1996 22:02:17 GMT
Blue Road Research 1997-"Hands On"
Fiber Optic Sensor Courses
Spring Course-April 29-May 1, 1997
Fall Course-September 16-18, 1997
Fiber optic sensor technology offers a series of advantages with respect
to prior art electrical sensors that are changing the way many current
products are built and will open up the opportunity for many new systems.
The light weight and small size of fiber sensors are strongly complemented
by their strong immunity to electromagnetic interference eliminating the
need for heavy and costly shielding. The result has been widespread
interest in applying this technology to aerospace structures where weight
is critical. The automotive industry is looking at the use of fiber
sensors in automobile engines and intelligent highways. Because the fiber
sensors are made of glass they can tolerate wide temperature ranges, and
high levels of vibration and shock. Other materials such as sapphire for
very high temperatures and plastic fibers for very low cost have also been
effectively used. The medical profession is beginning to see widespread
use of fiber optic sensors to monitor constituents of the blood and drug
dosage. This course provides an overview of this technology and makes
extensive use of laboratories and demonstrations to allow participants to
understand how these devices are built and work.
COURSE MATERIALS
The course will be supplemented by course lecture notes that will be
provided the first day of class. Attendees may also want to purchase one
or more of the texts Fiber Optic Sensors: An Introduction for Engineers
and Scientists, Wiley, 1991, and Fiber Optic Smart Structrures, Wiley,
1995 both are edited by Eric Udd and may be purchased by registrants of
the course at a 15% discount from the Wiley list price.
INSTRUCTOR
Eric Udd, MSE
President of Blue Road Research, Inc. in Troutdale, Oregon, Mr. Udd has
over 15 years of experience in teaching fiber optic sensor courses. Prior
to founding Blue Road Research in 1993 to develop fiber optic sensor
technology, Mr. Udd was a McDonnell Douglas Fellow at McDonnell Douglas
Aerospace. Mr. Udd has had over 18 years of experience in the fiber optic
sensor field and has acted as principal investigator and or program
manager on over 20 DOD, commercial and internal research and development
efforts on fiber optic gyros, acoustic sensors, accelerometers, seismic,
strain, temperature and pressure sensors as well as fiber optic
communication systems. He has more than 60 papers published on fiber
optic sensors and has approximately 25 patents on fiber optic technology
issued or pending. He has edited the books, Fiber Optic Sensors: An
Introduction for Engineers and Scientists, Wiley, 1991 and Fiber Optic
Smart Sturctures, Wiley, 1995. Mr. Udd has chaired seventeen conferences
on fiber optic sensors and smart structures. He is a Fellow of SPIE-the
International Society for Optical Engineering, and is a member of OSA,
LEOS, and IEEE.
Day One-Fundamental Components and Concepts
Fiber optic sensors are comprised of light sources, modulators, light beam
conditioning optics, modulators, optical fiber and detectors. These
components will be reviewed and the interrelationship between their
operation and characteristics and fiber sensor performance described.
Intensity Based Fiber Optic Sensors
Some of the simplest yet commercially most effective fiber optic sensors
are based on intensity modulation. This part of the course will review
the operation of fiber optic sensors based on microbending, evanescence,
band edge, total internal reflection, blackbody radiation and grating mask
structures. Application of these sensors to temperature, pressure, linear
and rotary position sensing will be described.
Spectral Reflection Based Fiber Optic Sensors
In order to avoid problems associated with changes in intensity due to
variable cable losses and connectors sensors based on spectral reflection
offer the advantage of resistance to errors induced by intensity
variations. The two most commonly used examples of this type of sensor
are the Fabry-Perot etalon and the fiber grating. The methods of
fabricating these sensors and their performance characteristics will be
described.
Afternoon Laboratories and Demonstrations
Examination of fiber optic sensor components and associated hardware.
Demonstration of intensity and spectrally based fiber optic sensors.
Splicing, cleaving and assembly techniques associated with fiber optic
sensors. An intensity based liquid level sensor will be constructed and
demonstrated.
Day Two-Lectures
The Mach-Zehnder and Michelson Interferometers
The Mach-Zehnder and Michelson interferometers offer extremely high
sensitivity and have been used to support acoustic, magnetic, electric and
seismic sensors. The construction and operation of these sensors will be
reviewed and examples given of how these sensors may be used.
Multiplexing Fiber Optic Sensors
Methods of multiplexing fiber optic sensors including time, frequency,
wavelength, coherence and polarization techniques will be described.
Tradeoffs will be made between the various methods of multiplexing.
The Sagnac Interferometer
The Sagnac interferometer is the basis for the fiber optic gyro which is
the largest current market for a stand alone fiber optic sensor. This
interferometer can also be used to support acoustic, magnetic, and strain
sensing. This section of the course will describe how the Sagnac
interferometer may be configured to sense rotation and how various "error"
sources associated with fiber optic gyros can be used to convert the
device to sense other environmental parameters.
*Day Two Laboratories and Demonstrations
Attendees will build a Sagnac interferometer. This will be used to
demonstrate the measurement of rotation and acoustic signals. Also during
this afternoon construction will begin of a fiber optic grating based
sensor and demodulation system capable of measuring strain and
temperature.
*Day Three Lectures
Distributed Fiber Optic Sensors
Various methods have been devised to measure temperature, strain and
acoustic signatures along the length of an optical fiber. These methods
will be described as well as their applications and limitations.
Fiber Optic Smart Structures
One of the most exciting fields of fiber optic sensors is the area of
fiber optic smart structures where hair thin optical fibers are placed in
composite materials to measure such parameters as temperature, pressure
and strain. The application areas range from improving the manufacturing
process to health and damage assessment systems. This part of the course
will provide an overview of fiber optic sensors that are appropriate for
fiber optic smart structures and examples of how they are being applied.
Chemical and Environmental Sensors
This lecture will concentrate on how fiber optic sensors may be used to
monitor chemical and environmental effects. These sensors are
particularly important to those working in the medical fields as well as
those engaged in monitoring sites for possible contamination.
*Day Three Laboratories and Demonstrations
This lab will conclude the construction and test of the fiber grating
sensor and demodulation system. A Mach-Zehnder interferometer will be
constructed and used to demonstrate environmental sensing including
acoustics and temperature. Polarization effects will also be studied in
conjunction with the Sagnac and Mach-Zehnder interferometers.
Class Information
Classes begin at 8:30 am and conclude at approximately 5 pm. All "Hands
On" classes are held at Blue Road Research, 2555 N.E. 205th Avenue,
Troutdale, Oregon 97060. Blue Road Research is located about 6 miles east
of Portland International Airport. 1996 "Hands-On" classes are limited to
8 participants so early enrollment is encouraged, when classes are filled
individuals will be encouraged to register for the next class (about a six
month wait).
Fee: The fee is $795 for the three day course. If space is available any
two days may be taken for $600 and one day for $300. Priority will be
given to those who register for the full course.
Hotel Information
Blue Road Research is located close to McMenamins Edgefield, 800
669-8610, 503 669-8610 a European style hotel set on 25 acres with rooms
that range from about $65 to $95 and the Phoenix Inn, 800 824-6824, 503
669-6500, with rooms at about $40 to $51 that many visitors to BRR have
found to be an exceptional value. Other area hotels (near Portland
airport about 10 to 15 minutes from the course site) include the Sheraton
Hotel Portland Airport, 503 281-2500, 800 325-3535, the Shilo Inn-Airport
Way, 503 252-7500, 800 222-2244 and the Marriot Courtyard, 503 252-3200,
800 321-2211.
BLUE ROAD RESEARCH COURSE
REGISTRATION FORM
Please Print or Type
Name: ________________________________________________
Title: _________________________________________________
Company: _____________________________________________
Address including Mail-Stop: _____________________________
______________________________________________________
City: _________________________State: ________Zip:_______
Country (other than U.S.): ________________________________
Phone: _______________________________________________
Fax: _________________________________________________
email: ________________________________________________
BLUE ROAD RESEARCH COURSE
TITLE_________________________________________________
DATES________________________________________________
Please make checks payable to "Blue Road Research" and mail to Blue Road
Research, 2555 N.E. 205th Avenue, Troutdale, Oregon 97060. Payment may
also be made by Master Card or Visa by contacting Blue Road Research at
503 667-7772, fax 503 667-7880.
Subject: Re: Flow loss past coupling.
From: tburton@cts.com (Tom Burton)
Date: Sat, 14 Dec 1996 01:30:37 GMT
Several days have passed, but it looks like no one has reponded, so I'll give
it a shot. Suggestions follow related text below.
On Mon, 09 Dec 1996 11:08:20 -0700, Paul Skoczylas
wrote:
>A rod is run through a length of vertical pipe.
...snip...
>
>1. The flow loss (pressure loss) past the coupling. Flow rates are
>such that the flow will always be laminar (esp. with viscous fluids).
>Right now we are not considering the effects of the change in diameters,
>but rather are considering the loss in an annulus of the length of the
>coupling. This may or may not be a good approximation. Any
>suggestions?
Why not compute the expansion loss as if the Reynolds number were large:
Delta_P_e = (1/2) k rho (v2^2-v1^2)
where rho is the fluid's density, k is a loss coefficient roughly of order 1,
v2 is the mean fluid speed around the coupling, and v1 is the mean fluid speed
around the cylinder. If this expansion loss is small compared to the Delta_P_f
that you've already calculated, then your done. If not, then a more careful
analysis--or preferably relevant experimental data--may be needed.
>
>2. The axial force on the rod caused by fluid flowing past the
>coupling. Right now we are only using the estimated differential
>pressure across the coupling multiplied by the difference in
>cross-sectional areas of the rod and coupling. There is presumably some
>drag effects, by the flow along the surface of the coupling, plus some
>effects caused by the change in direction of the fluid to get around the
>coupling, plus the fact there is probably a low pressure wake behind the
>coupling. Does anyone have some suggestions for calculating these
>effects?
The flow analysis that yields the viscous pressure drop around the coupling
would normally also yield the frictional traction on the coupling. So why not
add that into the drag calculation? If you don't have that traction handy,
then here is a way to estimate roughly the frictional drag:
force = (1/2) * Delta_P_f * A
where Delta_P_f is the pressure drop you have already calculated due to
friction drag along the coupling (see question 1) and A is the cross-sectional
fluid area around the bushing. If this force is negligible compared to the one
you already calculated, then your done. If not, then, again, a more careful
analysis may be needed.
If you are willing to unwrap your annulus into a flat cavity, and if the
Reynolds number is very low (creeping flow), then you can solve this problem
analytically using conformal mapping. (Much better, you find someone else's
existing solution!) This would account for form and friction drag, the
low-pressure wake--the whole ball of wax.
>
>Thanks!
If this was any help, then your welcome.
>
>-Paul
Tom Burton Brahea Consulting 616/436-7436
Subject: Re: Pipe thread standards?
From: JPEYTON
Date: Sat, 14 Dec 1996 06:01:28 -0500
Theodore Henry Phares wrote:
>
> Hi,
>
> I have a vacuum cup with a 1/8" dia. nipple coming out of it.
> Unfortunately, the nipple is not threaded NPT, and I can't figure out what
> it is. It's close to 1/8" NPT, but not quite. Could it be NPS? Or is
> there another pipe thread standard w/o a taper? Is NPS usually used on
> pneumatic/vacuum stuff like this? To confuse the situation, I have some
> coiled air line that has NPT fittings.
>
> So, I have to ask:
>
> When and where is NPT used? When is NPS used?
>
> Are there common U.S. pipe thread standards in addition to NPT and NPS?
> How about metric?
>
> Can anyone suggest any references?
>
> Thanks in advance.
me.berkeley.edu/hel
Mr. Phares,
Have you checked the threads for PT standard compliance? PT threads have
same nominal diameter but slightly less taper & slightly different
thread pitch. ( Just enough to ruin your day ) PT threads are used
primarily by Asian (read Japanese) manufacturers
such as SMC,CKD,Toyo-Oki,etc. I don't know how or why the PT standard
developed.They are often referred to as "metric" but they are spec'd in
fractional inches. Go figure. . .(Kinda like measuring force in Kgf
instead of Newtons ) To check for sure what you have you might purchase
a thread pitch gage. (available for about $10-$20 from industrial supply
house like J&L; in Livonia,MI [don't have # handy]). Also you can learn
about the dozens of tapered thread standards (most are arcane or
proprietary) from the Machinery's Handbook. aka "THE Handbook" published
by Industrial Press (+/- $65) BTW: NPT threads are the default in North
America for low (-10 to 250psi) pressure apps using air / low viscosity
fluids.
Good luck!
Jim Peyton
Kinemetrix Industrial Design & Mfg.
