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- Characteristic Length of a 2D NACA Airfoil?
This may seem a stupid/basic question, but I haven't found the answer as of yet, so I would very much appreciate any help that someone can offer:
I am simulating a 2D NACA 0012 airfoil for various angles of attack. Unfortunately, after a mesh convergence study, I found that at an angle of attack of 8 degrees, I am obtaining a Coefficient of Lift (Cl) of just 0.54 (Re: 6million). This is far below what I would have expected. I have tried for numerous weeks to improve the accuracy without success, and I am now starting to wonder if there is a flaw with my original understanding/parameters.
Cl is given by the formula:
Cl = Lift Force / .5*rho*v*v*A
where rho is the density of air, v is the freestream velocity, and A is the planform area.....
In the case, of a 2D airfoil, it is my understanding that "A" would be given by the chord length. In my example, the chord length of my airfoil is 1m and as it is 2D, I would use a Reference Value for the Area of just 1 in Ansys Fluent.
Similarly for the coefficient of drag (Cd):
Cd = drag Force / .5*rho*v*v*A
where rho is the density of air, v is the freestream velocity, and A is the area.....
It is my understanding that A would be 1 in this case also.
Are my assumptions correct?
If they are, I cannot see where in the above formulae I consider the overall shape of the airfoil - i.e. if I had a NACA 0012 or a NACA 0015 airfoil, both 1m in length, my assumptions above would suggest that they both have the same coefficient of lift and drag, which cannot be correct?
Thanks in advance for any help you can provide.
For the last part of your problem:
the shape of the profile is discribed in the discussed formulas by the coefficents Cl and Cd them selves. They will be different r NACA 0012 and 0015 for the same flow conditions. Also note that Cl and Cd are normaly strongly dependent on angle of attack and Reynolds number. Looking for the problem from the other way -If you are performing simmulations with fluent and as a result you get Forces (lift and drag) they will be different for both profiles, giving as a result different calculated values of Cl and Cd.
I'm not sure about the problem with the value of A since I'm not axacltly fluent specialist, but to my understanding when you consider 2D simulation it is done for some infitizimaly small width of the profile dh. So, A would be A=dh*L. When you take A=1 (m^2) with L=1m this actualy mens dh=1 m which of course probobly isn't " very small" .This might ve the problem with wrong results of the coefficient Cl you get. When you put the correct value of dh that fluent assumed for lift force calculation in 2D flow, you should get more realistic reults.
Furthermore note that F_lift=Cl*A*ro*(v^2)/2 not /5 as you sugested.
Hope I could help,
- Anyone can help me about abut vortex induced vibration?
I want to know about vortex induced vibration and know it effect on structure specially dynamic response of structure.
Take a look at DNC RP-C205 which contains a lot of How To about environmental loads on structures. http://www.ivt.ntnu.no/imt/courses/tmr4195/literature/Standards%20and%20Recommendations/DNV-RP-C205.pdf
- Is it possible that Nst is smaller than Gst based on the output from the program Permut, and why?
hS (se) 0.610 (0.0663)
hT (se) 0.845 (0.0289)
Gst(se) 0.278 (0.0805)
vS (se) 0.540 (0.0676)
vT (se) 0.636 (0.0601)
Nst(se) 0.151 (0.0532)
Nst was smaller than Gst , it was quite the puzzle for me.
Thanks in advance.
This may helps:
- Can someone troubleshoot the problem of no precipitation after acid (TFA) cleavage of shot peptides like dipeptide?
I have been synthesizing a set of short peptides and i am facing a problem of no precipitation acid (TFA) in few of the peptides. I usually precipitate using diethyl ether and if still there is no precipitation, I go for petroleum ether but this time I have no precipitation with either of them
I also tried phase separation method using chloroform but it does not seems to be working in separating peptides from the impurities of side chain protections and all
I would think that trifluoroacetatic acid salts of dipeptides only rarely are crystalline, as a rule rather than an exception.
Sometimes, however, diisopropyl ether can precipitate these salts, even though that is not always doable.Following
- Does anybody suggest me a nice textbook about genetics?
Hello, I have a bachelor on psychology and making my master on neuroscience. I am going to do my thesis in a molecular biology and genetics laboratory, however beforehand, I have to study on the basics of genetics. It would be great if you would suggest a book mainly based on vertebrates.
Thank you in advance.Following
- The Analytic Hierarchy Process-Is it old and Outdated?
I am in the process of developing a proposal which hinges on developing a risk assessment model. I am proposing to use multi criteria decision analysis tools for this especially the AHP by Prof Saaty. However, one of the Professors commented as follows: "The research method suggested looks rather simple and is using a very outdated method".
I note that much as there have been newer versions as alternatives to the AHP ie fuzzy methods and TOPSIS, the AHP appears to remain dominant both in practice and academia. Based on this, i feel the AHP remains a dominant legend in multi criteria decision analysis. Any thoughts for tried and tested alternative methods for me to develop a risk assessment model?Following
- What is the relevance of electro-deposing polymers at negative Celcius temperatures? How can it enhance the actuation performances?
Most of the researchers working on EAP actuators grow the polymers at -20°C for instance, but I couldn't find any pertinent chemical/electrical/mechanical explanation.
Some electro deposing composites depends on the structure of polymer and most of the time you can not have defined structure for a polymer containing double bonds, so each form has different capacity. Temperature allows the enough energy to achieve the defined structure, so my point is maybe low temperatures can cause a defect free formation of well defined chain which might be ideal by not providing enough energy to form altering structure.Following
- History of community development in Africa?
I am currently working on a document concerning community development (CD) in Sub-Saharan African context. I am currently searching for published works on the subject. I know this is a diverse topic to embark in Africa, but any country or countries context(s) in the Sub-Saharn region will be of help.
Typical themes will of interest will include:
- Traditional contexts of CD
- Pre-colonial CD
- Connection of land or land tenure to CD
- How CD has developed over time, etc.
- HIA - gathering health and economics - how to make sense?
1 How can I properly structure metrics for assessing health benefits of urban mobility projects, as well as healthier food supply?
2 In other words, how can HIA procedures (through detailed metrics) help urban planners to make tangible health plus economic advantages of their projects ( whether possible)?
The two metrics that immediately come to mind are obesity and time spent exercising. Both levels should improve following effective programs of that nature. I would take a difference-in-differences approach if possible, using nearby locations. This would be a great way for urban planners to not only point to the improvements in the population, but also how they've done a better job than the nearby "competing" locations. I hope that this helps.Following
- Any idea on modeling of delamination in shells using cohesive elements?
I find that the cohesive zone elements embedded in ABAQUS can not be deleted under mix-mode loading, especially when there is compression load. Even if those elements are excessively distorted because in my model SDEG VALUE IS ZERO ALWAYS AND STATUS VARIABLE HAS VALUE OF 1 ..
1. So I want to ask that why they can't be deleted. Do cohesive zone elements work well under mix-mode loading involving compression? Or should I inprove my model in some certain way?
Do you have any suggestions?
my project is post buckling and growth of delamination in composite shell ,,delamination is modeled using zero thickness cohesive elements..?
As I know in using of cohesive zone model, the cohesive material properties especially the elastic and traction properties affect the element delition significantly. In order to see how the elements can be deleted, pls choose less values of maximum traction. Also, to prevent from excessive distortion of cohesive elements you can increase the elastic properties of the CZM. I think your problem is due to the wrong properties of CZM not to mixed-mode crack propagation.
I hope it will help you
- When using the attached inequalities, how can the parameters be calculated?
Right now I am working with Prospect theory framework and I struggle with mathematical calculations part.
I would appreciate any help, how using attached inequalities, the parameters are found out (the answers are given as well).
Dear Dr. Lehtihet,
Looks like I have found the reason for inconsistencies between our two solutions. My program was written using the presented PDF file (the one accompanying a speadsheet file) and you were most likely using the picture now seen directly below the question. In "my" version there are constants pA2=0.9 and pB1=0.1, while in original formulation (non-symbolic, that's why I didn't use it) those two constants are equal to 0.1 So, different inequalities systems have different solutions.
In my opinion both our methods are acceptable. My is slower, but always produces guaranteed results even if rounding errors are non-negligible. Anyway, spreadsheet is also fine if one is interested in just a single acceptable solution, disregarding all others.
In summary, we both did a good job.
With best regards,
- Why is overall activity and expression of peroxidase isoenzyme in a root system more pronounced than an aerial one, under cold acclimation?
Why overall activity and the expression of izoenzymes peroxidase is more pronounced during the acclimation low non-freezing temperatures in root tissue than aerial tissues (leaves and stems)
Yes, there are many reports in different plants with respect to metals and salts etc.Following
- What is the current state of diabetic treatment through targeted drug delivery with nanoparticles?
My research area is nowhere near to drug delivery. But it looked interesting. As far I know stop of production of a hormone called insulin is the reason of diabetic and that's why this insulin is injected to human body. So, I was just thinking whether there is any technology already available where we can store insulin hormone and place it inside the body for long years to supply those insulin.
It would be great if you are kind enough to let me know about the latest state of drug delivery research via nanoparticles.
Thanking you in advance
Dear Professor Marco
Thank you very much for your such kind response.
What made me interested about this thing is an article of Microchip,(http://www.technologyreview.com/news/528121/a-contraceptive-implant-with-remote-control/) where they made a chip to supply the levonorgestrel hormone as an alternative to contraceptive pills. So, I was curious to know whether such thing can be done for diabetic patients as well.
What I have understood the main problems are:
1) In case of supplying levonorgestrel, the control is pretty simple as the dose is fixed. They did it 30micrograms/dose. But for the case of insulin, you have to measure the blood sugar in every instant and control the dose accordingly.
2) The risk factor is much higher for insulin. For the contraceptive case, any mishit will make someone pregnant but for insulin, they have to die.
3) For levonorgestrel, you need very small amount but for insulin, it needs much more quantity compared to levonorgestrel. So, to store it for long years, as they did 16 years for contraceptives, the insulin has to shrink in a big scale. And this is a big big challenge.
4) levonorgestrel is chemically stable in nature, where insulin is chemically unstable.
Am I right about the things? And are there some more thing should be taken in consideration?
One more thing: this video from a Professor of Uni of Cal, San Francisco looks interesting : https://www.youtube.com/watch?v=rY_siujVJEgFollowing
- What is the effect of sulphur mustard on radiation therapy?
What is the effect of sulphur mustard on radiation therapy?
This is an interesting topic.
I would like to know if there are documented facts about mortality from the administration of sulphur mustard.
Thanks dear Jorge, for the update on the effects of SM administration. From the picture you painted, it doesn't look as if the gains outweighs the risks, does it?Following
- How can I estimate vitamin D level in rat?
Thanks in advance for your replies.
Its okay thank you!!Following
- There any state of the art sustainability in home gardens?
I need assessment sources on measuring sustainability in home gardens, Thank´s. Greetings.Following
- Which one is best fit for Urban/City's Park Soundscape recording, Ambisonic or Binaural ?
I need some suggestions based on experience from Soundscape related researchers. All the City's parks I would like to analyze are small in size and located in a busy streets. Thanks.Following
- A study from Stanford has established PPIs causing MI, any other study apart from this?
It is known that PPIs hamper the functioning of Nitric Oxide Synthase, decreasing the endogenous NO for coronary vessels. Is there any trial that supports PPIs are causing MI. If yes, what is the type of trial and is it worth establishing this fact?
The AGA disagrees with the PloS One findings.
See the ref here:
- What is the best survey method for assessing how CSOs manage ethnic politics?
I asked this question because I am collecting data on the management of ethnic politics by CSOs in Ghana for my masters thesis. my thesis is qualitative perspective
You may wish to know that abbreviations mean different things and create ambiguity.
What is CSO?Following
- Is there anyone who is working on the chondrosarcoma cell line - SW-1353?
Is there anyone who can lend me the chondrosarcoma cell line SW-1353?Following
- Is there any way to obtain estimated coefficients for random effects in Stata?
By default, Stata estimates random effects in multilevel mixed models (e.g. mixed or meqrlogit) in the form of variance components - so I get one estimate for an intercept modeled as random effect on level 2. I wonder if it is possible to additionally obtain average effect coefficients for factor variables (e.g. time) that are specified as random effects on level 2. In other words, I would like to have single coefficients for any level of my random effects variable time instead of the estimated variance only. I know that SAS PROC MIXED provides such estimates but I am not sure on how to do this in Stata.
Thanks a lot.
It is possible to run cross level models in Stata, but I am not sure if it is possible to retrieve those specific coefficients. I'll play around with it and see if I can figure it out.Following
- Is Chalmers' so-called "hard problem" in consciousness real?
In his 2014 book "Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts" Stanislas Dehaene wrote "Chalmers, a philosopher of the University of Arizona, is famous for introducing a distinction between the easy and the hard problems. The easy problem of consciousness, he argues, consists in explaining the many functions of the brain: how do we recognize a face, a word, or a landscape? How do we extract information form the senses and use it to guide our behavior? How do we generate sentences to describe what we feel?
“Although all these questions are associated with consciousness,” Chalmers argues, “they all concern the objective mechanisms of the cognitive system, and consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them. By contrast the hard problem is the “question of how physical processes in the brain give rise to subjective experience … the way things feel for the subject. When we see for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness or the meditative quality of a moment lost in thought … It is these phenomena that poses the real mystery of the mind”."
Stanislas Dehaene's opinion is "that Chalmers swapped the labels: it is the “easy” problem that is hard, while the “hard” problem just seems hard because it engages ill-defined intuitions. Once our intuition is educated by cognitive neuroscience and computer simulations, Chalmers’ “hard problem” will evaporate".
Personally, I agree with Stanislas Dehaene's opinion.
Thanks. Yes, then, it goes poof.Following
- Where can I find literature on information flow regarding lean operations within service industry?
I am looking for literature describing what information flow is and it's impact within the service industry. I am also interested to what information flow techniques are widely known and most efficient, to improve the information flow within an organisation. Lastly, I would also be interested in examples of organisations that have been successful or have failed after implementation of new information flow techniques, which was supposed to improve the organisation.
information flow is an abstract word. however, it is related to lean manufacturing we can understand this concept through every lean dimensions. VSM, 5ss, poka yoke etc..
Lean Connections: Making Information Flow Efficiently and Effectively Paperback – June 2, 2008by
Chris Harris (Author)
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Chris Harris (Author), Rick Harris (Author)
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ISBN-13: 978-1563273742 ISBN-10: 1563273748 Edition: 1st
ADDRESSING INFORMATION FLOW IN LEAN
PRODUCTION MANAGEMENT AND CONTROL
Bhargav Dave1, Sylvain Kubler2, Kary Främling3 and Lauri Koskela4Following
- Which is the appropriate statistical test for this data?
I have recorded data from N subjects (for the moment 9, but it will increase). After each experiment I use different analysis and the success rate. The analysis is divided into three parts which can be perform in several ways:
Start : S1, S2, S3, S4
Mid: M1, M2, M3, M4, M5
End: E1, E2, E3, E4
S4 can be combined only with M4 and M5, while S1..S3 can be combined with M1...M3. E1...E4 can be combined with all the previous combinations. In total there are 44 combinations, for example S1M1E1 or S3M2E4.
The first analysis that I performed was a one-way ANOVA to find which was the "best" combination. The next that I want to test is which is the best Start, Mid and End.
I think that neither n-way ANOVA or one-way MANOVA is the test that I should run, should I group by for example "Start", take the mean value for each subject and perform a one-way ANOVA? Should I count each of the different results as "Repeated measure"? In both cases I am losing the information about the interaction between "Start", "Mid" and "End". Which is the appropriate statistical test?
I am still having a hard time understanding your data layout and what it is you are trying to do. What specifically are your data, what are the variables, how do you determine what is the start, mid, and end - or are these different variables? Does each subject have all variables or levels of the variables?
I suggest that you attach a spreadsheet with the layout of your data and a few observations. Then, if you describe what you are hoping to accomplish, it would make it easier to respond to your post.
- Why is the polysome ratio lesser than monosomes on a polysome profile that I get?
I use the Beckmans gradient fractionator. I have just managed to install it and get a nice gradient on my own as noone seems to use this in my lab. As I am new into doing this, initially I got beautiful monosome vs polysome peak. Now I get neat gradients but the polysomes look lesser than the monosomes. Has anyone faced this problem?
We are short of money nowadays, but still retain brains.
We'll compete to anyone due to our brains.
"any answers on that front?" (I am citing you).Following
- What are the different ways to characterize the Magnetic domains in magnetic nanostructures other than MFM and PFM?
I would like to image the magnetic domains in magnetic thin films and nanowires nanotubes so what are the possible techniques to do this other than MFM and PFM?Following