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I have noticed that there are single microscopic slide/slip chambers (Cytodyne, Flexflow, IBIDI) and many studies have used these chambers. I wondered how it is possible to have more robust data by using a single fluid flow chamber (1 replicate) and a control?
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Hi Mustafa,
our tech support team is happy to help with your question but would need a bit more info on your research question, experimental setup, etc. Please get in touch via Email: techsupport@ibidi.com
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I am confused between bright color or other
can I try
lymphocyte (PE) and the other activation marker which will seen on it will (V450 and percp.cy5)
note that : i have already one marker from the rare antibodies with APC color which will use definitely at the panel
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I am using FACSCanto || which has 3 laser with 9 color, and i will stain surface and intra for the same cell.
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Dear all,
I have been doing research on the leak detection of pipelines for some time. I did the simulations with simcenter software. But unfortunately, I tried to detect the location of the leak using Kalman filter in different ways, but it is not possible. Is it possible to guide me? Is it possible to send me the MATLAB code so that I can try on my own water pipelines and simulations?
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Richard Fenner and Steve Mounce have done work using Kalman filters for leak detection in water distribution networks Seyed.
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I have a situation in a T-Junction Microfluidic device. I am generating water droplets in oil medium using 2D simulation. I have fixed the velocity parameter of both liquids and increase the width of the main channel (Horizontal long channel where oil is passed) ONLY. I see a decrease in average flow pressure in the device with increasing width of the main channel. How do you justify?
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Assuming no change in channel height, this is a conservation of energy situation in which some of the fluid's energy is in the pressure and some in the kinetic energy of the fluid. Because the mass flow rate must remain constant, if the cross-sectional area of the fluid is raised, the fluid's speed will also increase , but the pressure in that section of the channel will decrease to main the mass flow rate at constant
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Hello! I am running flow cytometry on PBMCs and trying to optimize my voltages for FSC and SSC. The voltages I used were: FSC: 170 and SSC: 273.
However, what was strange is that on FlowJo, the units for FSC-A and SSC-A were from 0-1000, and 97% of my cells lie within that axis. I am perplexed, as most of the FSC and SSC units I find online are from 0-250k.
I will really appreciate if someone could explain to me why there is such a great disparity, thank you!
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Hi, I think you may be getting confused. The numbers of the axes are not voltages, but is a scale of fluorescence intensity.
I'm not sure which instrument you are using, but check that how you are exporting the data files as this can affect what you see on FlowJo. Nonetheless, there can be a slight difference between what you see on the instrument and what you see in FlowJo.
Also check that when you optimized your voltages, were you looking at FSC height, area, or width on the instrument? I see on the picture you put that you selected area, just check if that's what you used on your instrument.
If all else fails, email FlowJo support for assistance. They are really helpful
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Hello Everyone,
I'm modelling heat transfer in thermoacoustic device using Ansys fluent - the problem is 3D. Please what is the best way to specify the mean pressure of 5bar in the domain. The flow is driven by oscillating pressure at the inlet and outlet (that's there is reversed flow). 
I'm getting divergence in solution after the solution is first converged at about just 5 time step. I specified the mean pressure to be the operating pressure, while I used udf to specify the inlet and outlet oscillating pressure that is driven the flow. I enabled gravity. 
Suggestion will be appreciated. 
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Yes, the project finished in 2016. You can see some of the settings in this publication:
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While estimating the contraction and local scour, there are many equations in the literature mostly produced by using prismatic channels (e.g. rectangular). However, in real case studies, we are modelling the rivers with their irregular cross-sections and for scour analysis, the approach channel depth or flow depth at just upstream of the bridge could be "Maximum flow depth", "Local flow depth" at the upstream face of pier, and "Average flow depth".
The question is which approach should be used for contraction and local scour?
For contraction scour the answer is most probably the "Average flow depth".
What about the scour around piers?
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The depends on the depth of erosion you want to define. The assumed flow depth is the local depth immediately ahead of the supports or abutments.
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Hi,
Does anybody know of a self-report measure indexing the "runner's high" phenomenon (outside of flow scales)?
The term “runner’s high” (RH) is commonly used to describe the feeling of euphoria experienced by athletes engaged in endurance running. This state is usually characterized by (decreased) anxiety, relaxation, analgesia, euphoria, effortless running experience, and a “lost sense of time”.
Thanks!
Damien
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Running related "high" or coherent experiences is an everyday passion, as expounded in attached.
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I am wet spinning and have two syringe pumps. I want to run one pump at a time but as the syringe gets low on material start the second pump and turn the first pump off without interrupting the flow rate of the outlet. While the 2nd pump is running, I can fill up the first syringe and start that pump when the 2nd pump syringe gets low. So on and so forth. I would like to know if there is a directional valve that can help me achieve this. I was thinking a shuttle valve may work but I do not know if it will affect the outlet flow rate when I turn one pump off and another on
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Interesting
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Dear all,
I am trying to measure the pressure values of a venturi at the inlet and throat sections. The fluid is air at room temperature.
1. The main pipe diameter (D) is 6 mm and the throat diameter (d) is 3 mm. Measurements below 10 l/min do not satisfy Bernoulli's equation.
2. The main pipe diameter (D) is 7.5 mm and the throat diameter (d) is 4 mm. Measurements below 20 l/min do not satisfy Bernoulli's equation.
Is there any lower measurement limit for venturi flowmeters? If so, what is the underlying physical mechanism of this behavior?
Thank you in advance
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Note that by default, Venturi flow meters offer an accuracy of around ±1% of the discharge coefficient. Optimum calibration allows an even greater accuracy of up to ±0.25%. Venturi nozzle flow rate measurement systems are marginally more expensive than orifice-style flow meter systems.
Kind Regards
Qamar Ul Islam
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I'm trying to design an irrigation system in which I'm able to get slow liquid flow (dripping) out of multiple holes (exit points) that is uniform across all of the holes. The issue I keep running into is that any discrepancies in the holes - be it slight differences in size, orientation, etc.- results in a preferential path for the liquid and the flow becomes nonuniform; it flows fast out of some holes and slow (or not at all ) out of others.
Any thoughts on an approach would be greatly appreciated.
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I am reviewing some mobility flow data of the United States. Does anyone have recommendations regarding public access to big datasets such as mobile phone data, smart card data, or daily activities with the explicit origin and destination locations within the US (preferably, the individual-level data and not city or county level)?
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J. Rafiee
Hi, thanks for sharing the links. The daily and weekly flows between CBG to POI, CBG to CBG are gathered in the first two links, are there any sources that covers POI to POI inside a city?
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I have an O shaped water bath with a square cross section that I am circulating with an immersion circulator. How do I measure the flow rate at a given point in the bath? Can I use an anemometer even though that’s used for air?
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Flow rate is volume divided by time. So just put a floater and determine the time the floater goes round. Secondly determine the volume of water that you are stiring. This will give you a flow rate. Though this flow rate is higher than the middle one.
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I am doing a cell culturing experiment in a fluid flow chamber made of PDMS material. I was wondering how to sterilize the pipes and the flow chamber before/after the experiment, in case I want to use the same chamber for the second and third biological repeats?
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Hi,
We used devices repeatedly made up of PDMS as well as other materials with pathogenic bacteria. As long as the materials are Autoclaveable there is no problem in reusing them. Infact the current scenario of having sustainable development contains inherent clause of showing how we can use the same devices for longer periods with use of minimal processing. Apart form that, technically PDMS has shown to provide good results as long as the devices made from it are sterilized meticulously. It all percolates down to how good your skills are while handling cell cultures!!!
Regards
Amit
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My question is regarding how to make a custom-made culturing flasks (micro-fluidics) using a mold and flowable material that is similar to resin? what material is the most suitable in terms of cytotoxicit/biocompatiblity?
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I work in the northeastern USA and I am trying to find options for temperature/level loggers with automated real-time data collection and cloud-based data storage for easy data access. We have a network of sensors in our study watersheds, and data download takes up a lot of time and resources. Anyone have good luck with any sensors and/or data plans that offer cloud-based data access?
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Thank you, Brett Boisjolie, for discussing this issue. Since I live in a Himalayan region, we are still coping up to bring automated data loggers in our hydrological assessments. Usually, the systems we use are stand-alone systems that record data, which field workers manually pick up. However, in downstream areas wherein cellular networks are available, the data is continuously logged and sent to the admin while storing that in the cloud too...
Thanks
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I'm performing a cryogenic turning process.
The temperature are recorded from the thermal imaging camera.
Can I use these temperature values to simulate the flow characteristics and behaviour of the cryogenic coolant?
Is this an acceptable thesis?
Thank you in advance.
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Interesting question. Fluent provides you platform for using different input boundary conditions. But it requires a proper meshing and validation of the experimental results. You somehow have to formulate a process of extracting the input boundary conditions from the IR image.
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We have online GC-FID and GC-TCD (Mod: 2014) connected with flow reactor system.
This GC-FID/TCD is connected to a gas line coming from flow reactor system which I used for cascade reaction. In this flow reactor system ethanol is pumped with constant rate & heated at 160 oC and an inert gas (flow controlled by MFC) is using as carrier gas for ethanol. To prevent from condensation of ethanol, the line is wrapped with heating tapes. Further, the gas/ethanol flow through a loop in the GC-FID and GC-TCD, and when the sampling process starts, the GC takes the gas in the loop to column by pressing the switch (activate sampling at same time).
In this system, I flow the gas/ethanol at constant conditions in flow reactor for the long time as well, but I get instable peak area of ethanol in GC-FID as depicted in attached figure.
I tried a lot by changing the flow reactor parameters, checked gas leak, pressure regulators, sampling time. but facing the same problems.
Could anyone suggest me, where is the problem or anyone facing such type of issues?
Thanks in advance
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Raju Kumar , what is the initial temperature of the oven ?
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Hi,
We're having a bit of a problem while trying to find progenitor populations in bone marrow.
The protocol for CyTOF includes staining the cells, fixation, methanol perm for 15min, intracellular staining, fix and washes in 800g and Ir staining.
After washing the methanol, we had 5 million cells. However after Ir staining we were left with 3 million. Meaning we lost 2 million cells in the process. In addition, our CyTOF keeps clogging because of strange aggregates.
This feels a bit excessive and I was wondering where in the process we had it wrong.
Methanol is ice cold (-20C), added drop-wise, centrifuges were done in 800g.
Is it possible the cells were more vulnerable after the methanol and exploded in such speed?
Thanks
Mayan
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In my hands cell loss was largely due to the fact that there are many centrifugation steps (more than in FACS for instance), and I really compared lower vs. higher centrifugation steps and this appeared to be one major parameter that could reduce cell loss. I also thought 1000 x g was too high and would harm cells, but it worked like a charm and it might be even possible to go higher (I also did not mention that I began working at 800 x g, just like you, and I spun at 800 x g for all centrifugations until the methanol step).
I don't remember having big issues with aggregates, but I was working with human PBMCs and not bone-marrow cells so this was a bit different from you.
However, before I figured out that increasing centrifugation speed and working in V-bottom plates reduced cell loss, I tested if treating cells with DNase could help. The reason why I tested this is because I was suspecting dead cells (following the cisplatin treatment, which stains dead cells but which also induce cell death) to activate cells and/or to create some smears that would impair the process (trapping cells from the pellet, that would then move to the supernatant, for instance). Maybe that could be something you could test in your case ? Another thing we tested, but this was a pain in the neck, was to check the presence of cells in the supernatant after each centrifugation step, but I don't remember something spectacular from this and if I remember correctly number of cells found in the supernatant just began to increase after the methanol permeabilization.
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I'm currently developing my first lateral flow immunoassay and I have come accross some publications like when they optimize they lateral flow by computer simulation. I would like to dive deeper into such a branch of simulations and I wonder where to start, what should I try? Maybe you know some other publications with lateral flow device simulations.
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You might want to start with lattice-boltzman schemes, as I think they offer an an easy to understand introduction into numerical simulations. There is this python library pylbm ( https://pylbm.readthedocs.io/en/latest/). You could check out their example gallery to see if it's sufficient for your purposes..
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I know that ANSYS uses J2 flow theory (incremental plasticity approach) to solve the elasto-plastic problem. But I want to compare the results of  flow theory of plasticity and deformation plasticity theory. Can I do it using ANSYS or any other commercial software
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Dear Kanishk Sharma,
ANSYS does not possess the ability to perform direct computations with deformation theory of plasticity.
However, in the case of monotonic loading, the Multilinear Elasticity (TB,MELAS) can be used. The material behavior is described in this case by a piece-wise linear stress-strain curve. But the unloading is not linear and there is no hysteresis behavior.
Many years ago, I have implemented the deformation theory of plasticity into the finite element programm PANTOCRATOR (C++ code) developed in the St. Petersburg polytechnic university. Comparison of the finite-element simulation results for the deformation theory with the flow theory has shown their coincidence under proportional loading and strong differences under non-proportional loading.
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I need the ranged for flow water in liter/min for NTF
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Dear Dr Tawaha, according to following reference, the optimum flow rate of water in NTF for lettuce ranges from 3 to 8 L/square meter/hour i.e. 50-133 mL/square metre/minute.
Ref: Soilless culture: Theory and Practice. 2nd edition. 2019. (Eds. M. Raviv, J.H. Lieth and A. Bar-Tal).
With best regards Brahmanand
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I am familiar with Microsoft Office Suite but didn't have a Microsoft Visio license. Is there any free alternative that can be used to draw flows and diagrams for research papers/articles?
I searched online for Visio alternatives, there are many online services, but they are not user friendly and flexible.
Note: I am using Microsoft Word to write my articles.
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Dear Hadi
Actually I like using draw.io
I have a list of build-in templates and tools for different aspects.
The main advantage is the ability to save the diagrams as pdf files.
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Hello everyone,
I am looking for some references to understand the flow patterns when high-velocity gas is injected into a liquid tank. I want to see how the flow patterns are changing from low-velocity gas injection (bubbly flow) to high-velocity gas injection (droplet flow?). Can large pipes somehow be analogous to the flow patterns in liquid tanks when gas is injected?
Thank you.
Best regards,
EB
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Dear Mr. Thomas Frank.Thank you for your answer. I found exactly what I was looking for in the book that was recommended by Bachir Achour
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Does  anyone know the techniques to measure pressure change of less than 500Pa with at 100-150 oC? We would like to measure the air flow pressure change of less than 500Pa within a static pressure of 100KPa to 1.6MPa environment.
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Hi Kalpana
Lots of other manufacturers out there as well, e.g. GE Druck for industiral sensors, Kistler for more scientific sensors.
Take a look here for something that may land in between
I believe that Setra offers both typical strain based pressure sensors as well as capacitive pressure sensors. My guess is that the latter has a wider signal to noise ratio.
That said, amplitude resolution depends on how you digitze your signal - if you m
measure an analog output signal.
Sincerely
Claes
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I need to simulate the transition of Flow through Coarse Porous Media such as Rock-fill dams, to investigation of Water level profile in each distance from up-stream and determination of discharge of fluid seepage from the body of these media. Notice, I want to simulate a Single-Phase Flow.
How can I simulate this project? Please suggest and introduce a useful software for this issue to me...
What is your idea about Flow 3D, Fluent, ABAQUS,...
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Dear Dr. Majid Heydari ,
It would be appreciated if you explain more about the method you used to simulate the POROUS MEDIA for your Ph.D. thesis.
Best regards,
Mehdi
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I'm trying to find an empirical correlation for obtaining the critical Reynolds number in a 180-degree bend/curve/elbow with a circular cross-section (See the figure). I've searched for a lot of papers with no luck, but I know I’ve seen it somewhere before.
Can you recommend an article or book with a correlation for the critical Reynolds number as a function of tube diameter and curve radius?
Thank you in advance.
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In developing flows Reynolds number is a function of length and so is the arc of bend. If it is developed flow, with arc radius less than 10.33 mts ( atmospheric pressure head) the reynold's number is independent on arc radius and dependent on diameter. As long as dia is constant, there is no variation of reynolds, number.
But if the bend is sharp, the fluid creates a back pressure on the incoming flow, which will mostly make it unsteady flow pattern, where sudden drop in pressure occurs ( can be calculated using darcy-weisch bach relation) and suitable friction factor can be assessed. We can use reynold - calburn analogy to obtain Stanton number, with this we can arrive at reynold's number of the associated flow, at down stream of 180 degrees bend.
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I'm trying to use agent based simulation (ABS) for simulating emergency department. the goal of this study is optimization of patient flow in ED by minimizing length of stay and cost.
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Hi, ABS is a powerful tool but the most important think is to determine your agent , what I would suggest is to perform the Arena the simulation of your current system and check how the system behaves than you can model your system , it has OPTQUEST for optimization but I would not suggest that as it is just hit and trial method but what arena will do will provide you clear picture of your system with current waiting times and utilization value added etc times , after that you can use PSO or GA to solve the problem
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They have been proposed as the cause of the abnormal movement of the most distant galaxies in the observable Universe.
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@R. Guy Grantham Can we discuss about your research?
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To find the developed area of flow inside the tube we use the empirical relation (X = 0.05 ×D ×Re ). Can we use this relation to find the position of the developed flow inside the spiral tube?
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Yes, you can by assuming the tube to be locally Cartesian.
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How to measure discharge of a canal by surface float method?
If we know flow depth, top and bottom width of canal. And canal is lined with cement concrete. What should be size, weight and material of float? What is relation (Multiplying coefficient)between surface velocity and mean velocity?
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Greetings!
While not as precise as using a current meter, you can still get decent results using the float method. I offer a few suggestions below:
Float Choice. I agree with previous comments: Oranges are an excellent float because you want a float that is just below the water surface. If you use a stick or an empty plastic bottle, for example, any wind you have will likely influence your results. Oranges are relatively cheap (at least in the US) and they are biodegradable if you lose one in the stream. No matter what you use, it needs to be just dense enough that it sits just below the water surface, but doesn't sink or hit the bottom. Oranges fit this requirement. A half-filled plastic bottle might work, too, in an emergency.
Measurement Reach. This is not going to be an issue in a concrete trapezoid, but find a straight reach with minimum turbulence. There shouldn't be any constrictions, bends, or other other obstructions within about 5 channel widths up or downstream of your selected measurement reach. The more uniform the flow, the better the results. If present, you can remove wood, rocks, debris, etc... before you start the measurement. Just make sure you wait a period of time to allow the flow to become uniform again--15 minutes is a good rule of thumb, but it depends upon the size of the obstruction versus the size of the channel. You'll need to read the reach to decide when it's appropriate.
The section should be long enough such that you get at least 20 seconds of travel time for the floats. If you are doing storm event measurements, at the start of the measurement, you need to note the location of the water surface elevation as you'll likely have to come back later and measure the cross sectional area when it's safe to do so. In baseflow conditions, you should be able to measure the cross sectional area at the time you do the work.
If your intention is to go to the same site or sites in fair weather and foul for multiple measurements, I suggest that you monument or mark the measurement section. That way, you don't need to string a tape every time you go to a site. It's a time saver when you're working in the wet, in particular.
Finally, realize this--it is typically very difficult to find the perfect measurement location for a discharge measurement, no matter how you do it. Find the best site you can and do the best you can! Take lots of pictures of your site, take good notes during your work, and caveat your results as necessary in your write up.
Taking the Measurement. You need to sample the entire section, slow parts and fast. Don't just throw five floats in the middle, for example. In your mind or your field book, break the reach into two or three sections (example: Right Side third, Middle, Left Side Third). How many sections you need is best professional judgement.
In each section, I would recommend at least five measurements (so you'd have 15 data points in the example above). Also, make sure you introduce the float upstream far enough so that it has time to accelerate to the stream velocity before it crosses into the measurement reach. Use a stopwatch to measure the time needed for the float to travel to the downstream point of the measurement reach. I'm sure you realize this, but this type of flow measurement is usually a two person job.
Data Processing. Nothing to add here, really. You simply divide your measurement reach distance by the individual float travel times to get the individual surface velocities for each measurement. Then, I typically average all the measurements to compute an average velocity for the entire section. Once you have your average velocity, one important thing that was touched on before is you need to correct surface velocity measurements to average velocity measurements as surface values are always faster. The standard formula is:
Vavg = kVsur
where k is a correction coefficient that ranges from 0.80 in natural streams to 0.90 in artificial channels. Commonly, 0.85 is used--I might go to 0.90 in your case, based on your site description.
Final Thoughts. I don't know what your reason is for measuring discharge here, but if you are working long-term and you want to understand water flow at this location, you might want to install a staff plate and develop a rating curve for this site. Eventually, that would allow you to go to the site, take a reading off the staff plate, and get an instantaneous discharge value without having to measure it every time. That process, however, is too involved to describe here. But there are all kinds of references on-line for developing rating curves.
Good luck!
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I'm working on an overland flow model (MIKE 21 Flexible Mesh) where I have to set some open boundaries with a specified water level. After simulating a rain event, the triangulation mesh elements near the boundaries have water depths which are extremely high (hundreds of meters) and flow speeds of several hundreds of meters occur. What may cause this?
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Amin Rahdarian Agree, as long as the Courant number of your model is less than the recommended maximum value, the time step of the model should not be the key reason for the model to blow up or to cause unrealistically high water levels.
For surface elevation type of boundary condition, is there a recommended time step a time series boundary data? Will the time step have an impact on the simulation stability or extremely high water levels?
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Hello , for which percent we can trust in numerical solution results for energy and fluid flow problems in Fluent , Comsol , ... etc ?
Please verify the percentage for which software.
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you can be fairly certain, then all commercial codes available on the market are free of coding and algorithmic errors, i.e. they implement a numerical method for the solution of your problem correctly.
However, the numerical method itself, inherently, includes sources of error. These come primarily from space and time discretization (computational grid density and time step) as well as from which method has been used and terms up to which order have been neglected.
Furthermore, the mathematical-physical model, employed to describe the process you are simulating, is usually also an approximation of reality. For example, we know fluid viscosity is temperature dependent, but we choose to neglect that in our simulations, etc.
If the problem simulated is non-linear, a user-prescribed criterion is usually used to set the desired lowering of the error norms, which also contributes to the overall error.
My suggestion is to first identify all sources of error and try to keep them of the same order.
Secondly, one should always perform a nodalization analysis (and possibly a Richardson extrapolation) to examine, how the solution changes when different grids and time steps are used.
A short answer to your question, it is impossible to give a percentage to estimate the accuracy of a simulation. And beware, the accuracy does indeed depend on the expertise of the engineer doing the simulation.
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I am trying to determine whether tree cover (in proportions) at one site is affected by stream flow (and thus flooding, periods of drought etc.) recorded at the same site. The tree cover data is limited to a <20 records over the last 50 years while the flow data has a value for every month (average deseasonlised) for the last 30-50 years. What meaningful statistics would be valuable to assess the effects of flow on vegetation cover? I will repeat the process for each site to assess spatial variation.
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I might try looking at the rainfall in periods from the last vegetation assessment to the current vegetation count. I could see that an average rainfall might be important. Variance and periods of flood or drought might also be important. Before analysis, I would try graphing the data. Relationships might not be linear. I would also expect thresholds. Flooding for 2 days has little effect, but 3 weeks causes more extensive damage.
Temperature might influence vegetation growth as much or more than rainfall.
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I would like to find a way to build a model of the system I'm starting to research. Or really find any small amount of progress. Here's a snapshot of what's happening: Air is flowing (from atm.) through a porous media in what should be a vacuum chamber. I'm not concerned right now with why or eliminating the flow. I just started this in the last 2 days so I know very little and I'm still waiting to get some info from my peers. Rather sit and wait I want to try and see if I can get a leg up on some basic theory and possibly explore any similar mathematical models. I believe my peers want to characterize the flow so they are able to predict the behavior.
I am an undergraduate student and have taken an intro fluid mechanics class so my background is not in depth. I've been looking at some books and journal articles. They are okay but I'm just kind of aimlessly picking them.
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Hi
Air is fluid and has momentum principal when transfer, so you study about "Bernoulli,s low" and "friction loss" of gases specially air (Wright formula and Loeffler formula base on Weisbach formula)
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could you please explain by appliying bernoulli equation?
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For water, the continuity equation reduces to the divergence-free constraint divv =0.
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i need Froude Number output
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A converging nozzle increases the flow velocity and decreases the static pressure as per Bernoulli equation. Can a liquid flow through a converging nozzle result in static pressure below the vapour pressure of liquid and evaporation of liquid?
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But we will always have a high value of flow rate through a pipe (not nozzle) for any inlet condition beyond which vaporisation will occur.
For a pump, there would be a minimum pipe area for a fixed flow rate below which vaporisation will occur.
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I need the GAMS code for distribution load flow. In this regard, I have found the (improved) backward-forward sweep suitable to my work. So I need the GAMS code for this method.
I would appreciate if anyone can share this code with me.
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You can use the Developed power flow from this link
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Why does the imbibition process need a much higher pressure than the drainage process in the two-phase fluid flow in porous media?
Principally, because capillary pressure plays a positive role to drive the flow of wetting phase (e.g., water), the flow in an imbibition process (e.g., water displacing oil) should be easier (less pressure cost) than in a drainage (e.g., oil displacing water) process.
However, as shown by many laboratory core-scale test results, an imbibition usually needs a much higher pressure (e.g., 100 kPa) to drive the flow than a drainage (e.g., 20 kPa) under the same injection rate (e.g., 0.5 mL/min).
The high pressure during imbibition should be not due to the viscosity difference between fluids. When injecting either one of the phases alone in the media, the pressure drop is quite low.
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I fully agree with previous answers. But your question is not clear enough.
the distribution of fluids (previous history) and wettability (if the viscosities are similiar) are the controlling factors for the pressure needed to flow. involving capillary pressure muddles the issue.
For example, if your water saturation is 40 % and all the other variables are the same. Not all the pores have 40%! some will have 100% and others 20%. Therefore, the pressure drop will be different for different pore size distributions, mainly if they are not unimodal.
Also, during imbibition and drainage at the same saturation you will have different fluid distributions and as a consequence different pressures.
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Hi y'all,
I was trying to push water through a piece of porous media. I was measuring the pressure drop of it under a constant flow rate, and saw that the pressure drop kept increasing over time.
It starts as ~1 psi, and increases to like 10 psi after 7 minutes
Does anyone know why? This only happens to one type of my samples.
Edit: this is an experiment. It keeps increasing, but I can’t measure accurately because my tunings start to leak after 12 psi
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Hi Feichen and all.
OK: no loose particles migration and pore blocking. Then, the porous medium itself could be undergoing compression during experiment, thus reducing its permeability (Cf. Darcy’s Law). In this case, a constant flow rate would give what you getting: an increasing pressure drop. Try a constant very small flow rate. It will give a very small pressure drop, hopefully not enough to compress the medium and the pressure drop will be constant. If that is the case, you’re dealing with very compressible porous medium. If it is unavoidable to deal with this medium, for a given flow rate, you will need a large cross section so as to have low velocity and low pressure drop.
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Two nozzles of different output diameters (0.20 mm and 0.25 mm) are being used to take mass measurements for an analysis over a time period for the same input pressure.
It has been observed that the standard deviation in the measurements increases in with an increase in diameter of the nozzle.
Is this true? Does an increase in diameter causes greater fluctuations in the flow for the same input pressure?
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You can consider two parameters:
1) the mass flow rate, if it is taken constant an increase in the diameter causes a diminishing averaged velocity.
2) the Reynolds number, if the averaged velocity is taken constant the Re number increases. From 0.20 to 0.25 you are increasing the 25% and the Re number can be such that transition to turbulence can occur,
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Hi dear,
In a closed circuit water tunnel, I am going to use guide vanes in the bends for flow straightening.
Is there any methodology to determine the number of the required guide vanes and also the distance between the guide vanes?
Thanks,
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Dear Aaron Altman
Thanks for your suggestion.
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I want to be able to model some slug flow data using the unified model for gas-liquid pipe flow via slug dynamics by Zhang et al., 2003. Following the flow chart for slug flow calculation is challenging. Any help?
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Thanks to you Ahmed.
I will examine it and give you feedback soon.
Thanks again.
Joseph
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Hello all, currently I am doing experiments, in these experiments I am using a nozzle in order to cool a hot surface, meanwhile I am changing the water flow rate, and what I noticed is, when I change the water flow rate, the cone angle changes, and I am wondering whether the quality of the nozzle is low, or the water flow rate may affect the cone angle of the nozzle! Any answer will be very appreciated. thanks in advance for you all...  :) 
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I can't run MODFLOW Model using PEST in Visual MODFLOW Flex 4.1, and i can't find the tools PESTCHEK.EXE and INSCHEK.EXE in the PEST distribution files    to run the model , Is there any help, please ?
thank you
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I want to find a good Nusselt number correlations for nanofluid flow.
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Dear Sir,
Experimental study with numerical one for nanofluids is very interesting. But when we go for experimental part, the entire results are different. The trend was same but numerical value has great difference. As there are number of parameters which come into picture while doing experimentation which was not considered in numerical analysis.
Good luck
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I have a diffuser and i want ot calculate the pressure drop across the section.
In a diffuser we would also have a change in velocity or the fow.
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Any ideas on how to find the leakages in a pump.
This leakage should be a function of speed and pressure.
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I have read a book about turbulent plumes flow by rodi, there are 2 formulas about momentum flux and volume flux. In both formulas there is a constant K, but rodi didn't tells about the number. the formulas will develop into two parameters, plume invariant and richardson number. I need both of the values for my undergraduate thesis. So if you could tell me, i would be so grateful.
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If your  undergraduate work is related with environmental flows , perhaps it could be useful to read Chapter 9 (turbulent jets and plumes) of the now classic book by Fischer, List, Koh, Imberger and Brooks "Mixing in Inland and Coastal Waters"
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In a student group work we are making experiment on participants playing video games using  DFS-2 flow evaluation questionnaire.  We are looking for experimentation using this same questionnaire for other kind of activities, not related to game. the goal is to compare results.
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Thank you Patrick
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Dear Respondents,
State of forces acting on the typical sand particle due to water erosion is represented in the figure. Where of particle W, cohesive force FC, the angle of internal friction and resistance force FR . comment on them. If you find any fault kindly give your comments.
check if the cohesive force that acts between the particles representation is correct/wrong?
Resistance force,  FR=              given in the linked file,
Figure is given in word file attached
Thank you
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Dear Velusamy,
There are 3 ways that grains can move: 1. lifting of the grain off the grains beneath it. 2. sliding of the grain up and out of its position on the bed. 3. rotation of the grain about a pivot point formed by neighboring grains
For case 1, lift forces must exceed the “gravity force” (i.e. the weight, since gravity itself is an acceleration) For case 2, drag forces in the direction of easiest movement must exceed the combined frictional and gravitation force in the opposite direction For case 3, the moment of the fluid forces must exceed the moment of the gravitational force.
Fluid force is the resultant between lift component and Drag force.
With my best regards
Prof. Bachir ACHOUR
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I'm doing a differentiation experiment with flow analysis, comparing two cell lines: one is the wt cell line, and the other is a stable line transduced with our GOI + GFP marker.
The GFP is just a marker and is not important for my experiment.  Can I leave the GFP uncompensated?  The panels I'm using are:
(1st panel) PerCP-Cy5.5(Blue A), PE-Cy5(Y/G C), Alexa700(Red B), and sytox orange(Y/G E).
(2nd panel) APC(Red C), APC-Cy7(Red A), and sytox orange(Y/G E).
I checked the spectra and it doesn't look like GFP will overlap with the other fluors?  Also, I'm worried that I can't really compare the GFP- cell line with the GFP+ cell line if I compensate for GFP; it might overcompensate the GFP- cells.   
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Hi Kelly,
If you expect to see fluorescent shifts in the colors you are interested in I would suggest compensating.  Although the GFP may not contribute to the other fluorophores in this experiment, but it may in the future.  It's a good habit to get into because it eliminates one more confounder.  Finally, if you're using FlowJo you can remove the compensation after the fact and look at the differences.  Here is a article (of sorts) on compensation.
Good luck,
NM
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what type of information can be obtained by performing cyclic voltammetry for my redox flow cell?
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Thanks Mohammed
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Hi,
I am trying to find an empirical formula/graph/simple calculation that I can use to predict the flow pattern inside a horizontal rotating hollow cylinder. I intend to find a method by which I can understand the onset of different flow patters (i.e. annular, rimming, pool .etc) by varying the liquid fill percentage and/or the rotational velocity of the cylinder. I want to find out such data for a variety of setups and hence am not using CFD or experimentation.
It would be of great help if anyone could suggest a source to find the same.
Regards,
Vinayak Krishnan
MSc. Mech. TU Delft
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You don't need to select the moving mesh. Just select the boundary of the cylinder as 'wall' and specify the wall as moving, then select 'rotating', then put the rotating wall in ' rad/sec'.
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Is it possible that if one keeps on increasing the RPM of a fan,a certain point will come that it would start acting like an impenetrable disk and hence cause much more hindrance to the flow passing through it?
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Friction will be the main reason to reduce the RPM even the power increases.
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Hi everyone,
I'm studying the flow behind a bluff body and I have done a large eddy simulation in ANSYS-FLUENT 17.0. Now I would like to show the shedding vortices behind the bluff body in CFD-post; but I can't find vorticity in the list of parameters to plot the vorticity contour. Does anyone have idea?
Thank you,
Ali
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you can insert a plane in the position you interest and then insert vector in that plane, this will help you to see the velocity vector and if you interest about the vorticity you can export it from FLeunt and select it instead of vector 
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How can I sketch the T-S diagram for a flow in a duct with constant area through a Fanno, Normal shock, Rayleigh with heating and Fanno conditions, respectively.
Thanks in advance...
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Thanks for your favor, Dr Adel Oueslati.
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Hello,
I’m having some trouble simulating laminar steady-state flow over a sphere (OpenFOAM). The solution is converged but I’m having about 15% error on the drag coefficient (CD) for 10 < Re < 100, and about 20% for Re <= 1. Please, see some pictures of my simulation in this website http://imgur.com/a/AxIWE for more details.
Mesh
I’ve tested finer meshes to ensure the mesh independence. (The CD of the mesh from the pictures differs only 1.5% from a 15.4% more refined mesh)
Post-processing
From the picture "Pressure over the sphere and U streamlines for Re = 80", it seems like the flow isn’t steady (because of the different size of the recirculation zone), but shouldn’t it be for Re = 80? The separation zone is increasing the pressure in the back of the sphere, is that right?
Results
I think that there’s something strange with the pressure field, because for very low Reynolds numbers (<= 1) the drag should be predominantly viscous (the pressure CD represents 33.6% of the total CD).
Simulation parameters
I’m using simpleFoam solver (SIMPLE algorithm), GAMG for pressure (p) field and smoothSolver for velocity field (U) (see pictures for fvSoultion and fvSchemes). I’ve already changed those field solvers (PGC, GAMG, …), refined the mesh, reduced the tolerance of p, checked the boundary conditions and checked the size of the fluid domain, but the results barely change.
Does anyone have any clue what’s wrong, please?
Thanks in advance.
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Dear Renan Thomes,
I am happy that (atleast) some of my advice proved useful. From your (I must say pretty extensive) searches and simulation attempts, we are now confident that it is NOT the rate of mesh/grid extension/expansion/coarsening that is the problem. Further, you stated that you had already tried refining the mesh which didn't lead to major changes in the results. So at this stage we can (probably) assume that it is NOT the grid that's the problem.
My experience in CFD tells me that ONE computational framework (or solver setting) cannot conquer all cases of a given problem....in your case....different values of Re of flow over the sphere.
One has to understand the balance between inertia and viscous forces in a given simulation (hoping that those are the only two things we need to worry about :))...my Ph.D. senior taught me that (♡). Hence, for 20 < Re < 200, the flow is comparatively more advection (inertia) dominant than when Re < 20. Hence, there is a risk of artificial/numerical diffusion contaminating the solution at larger Re...so, a higher order (LinearUpwind in your case) scheme is necessary. On the other hand, because the low Re flow would be diffusion (viscous) dominant, a (pure) first order scheme would probably suffice and using a higher order scheme there may involve a risk of over-predicting velocities (which higher-order schemes do...by the way). 
Regarding the free-stream velocity being 1.03 m/s far away from the sphere...the free-stream velocity will increase AROUND THE SPHERE due to flow separation since the domain has to accommodate the same flow-rate (across any section) regardless of separation bubbles getting formed. But far away from the sphere...a 3% increase in free-stream velocity might be of some concern...hope you are not using WALL/SLIP/NO-PENETRATION conditions at the domain boundaries....What you can do is carry out a flux-balance between the inlet and the outlet (an option available in FLUENT but not sure about OpenFOAM)....the inlet-outlet mass flow rate difference should be around 1e-15 kg/s (or m3/s) or less to ensure that there is no volume dilatation in the domain. 
Regarding your attempts towards validating the analytical solutions...I think the expressions are in terms of radial (Ur) and tangential (Uθ) velocities...so I hope you used some kind of transformation to convert them from curvilinear (r,θ,z) to Cartesian space (x,y,z). Regarding the differences between simulation and analytical values....the analytical solution neglects all acceleration effects occurring during interaction with the sphere (as stated in the MIT-OCW document). For instance, analytically, the vertical velocity (W) is consistently zero above the sphere which is not possible in practice (observable in your results). Moreover, the U-velocity above the sphere ought to be more in practice (also observable from your results) because of the "crowding effect" (also mentioned in the MIT-OCW document).
But the fact that the free-stream velocity will actually decrease for creeping flows (Re<<1) has really "damaged my intuition" :) :) :)...
I hope you will be able to find a solution to your problem for Re<20 as well Renan. It was really nice having this discussion with you.  
Best regards.
Shaswat Saincher
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I am trying to test for Jurkat activation following stimulation with peptide-pulsed APCs. I am looking for a flow-based assay. Are there jurkat markers other than CD69 that are up/downregulated upon TCR activation?
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Thank you everyone!!
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Heat transfer in brazed plates exchanger
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Dear Mohamed,
I invite to take a look at Ph.D. thesis that can be found in the following link (it is in french) :
or at the article :
I have studied single phase flow and two-phase flow (condensation) inside BPHE. In general there is no single value for "critical" Reynolds number. I prefer not to call it critical because it is not a transition between laminar and turbulent flow. it is in fact a transition between helical flow and zig-zag (cross-flow). this Reynolds number represents the transition between a dominant helical flow for Re < Re_cr and a dominant zig-zag flow for Re> Re_cr.
the value of this Reynolds number depends on the geometry (inclinaison angle, corrugation pitch, plate spacing). In my Ph.D. , the first part is about single phase flow where you can find all the previous informations.
I hope this will be helpful for you.
Kind regards,
Kifah SARRAF
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I am trying to design a counter rotating wind turbine system and looking for an alternative method to find blade properties for the second rotor(downstream of flow of first turbine). For a single rotor wind turbine, Betz and Schmitz methods help out, but I can't find a similar approach for counter rotating wind turbines.
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Thank You Sir
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Streams are freshwater with fast flowing current (velocity 0.4 to up to 1 m/s), from main channels (C.20 metres wide, depth c. up to 5 metres in pools) to tributary streams (5-10m wide, mostly wadeable). River has rocky bed.  Mini rapids (main rivers) waterfalls and cascades  are common features.
Stream water is clear at baseflow with low conductivity (24.7 +/- 5.7 microS/cm) but gets turbid after rainfall.
Watershed is forested - gets pitch dark at night
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I did fail to mention, a plastic pipe with clear, watertight plexiglass viewer at bottom was sometimes useful in fast and shallow waters to see some darters and sculpins.  These are commercially available, and handles on the plastic pipe help to hold in place or move as needed.  Would not work well in highly turbid or bubbly waters.  The view is limited, but still may be useful in some circumstances.
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Hello,
I am trying to calculate the convection coefficients of the different faces of a building. Thus, I am wondering how to deal with external convection with a wind of a different direction from completely parallel or completely normal to the surface subject to the convection (see the attached picture).
For instance, under EES, for a vertical plate, there is a correlation dedicated to parallel flow, another one to normal flow and another one for a flow directing to the edge of a diamond shape. But no correlation is proposed for an any wind direction for a vertical shape.
By advance, thank you
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u can use same EES of vertical plate itself...am not sure 100% let me check 
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If the flow past a wind turbine is passed through a nozzle, will the flow's angular velocity change?
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Yes, but not only vorticity is important. You are also to take into investigations the geometry of the nozzle
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I am doing master thesis in which I have to optimise active power flowing through HVDC link and it is installed in parallel to AC line. I need to know how can I make obective function and what would be my constraints for this function?
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I have to maximize hvdc transmission power. 
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Show me your model you will use, plz.
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 Thank you for your answer and publication you have recommended, I just wonder which kind of model she will use in pulsatile flow research for crossflow. 
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In evaporator and condenser there two phase flow where may exist different kind of instabilities.
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@ Manigandan. For example pressure drop oscillation. Or thermal oscillation or flow patternoscillation....
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Greeting.
I am interesting on these topic.
any information or additional detail about this work
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Greeting.
Thank you very much Dr. Jean for your response.
Please, kindly I really hop to get opportunity to discuss with you some aspect relating modelling viscoelastic flow during extrusion in my work . I used Starr CCM software and finite element formulation.  
I will very grateful for you to give me this glorious chance  
Kind Regard
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Hello everyone,
Are there any recent works that involve the study of pressure drop in foam flows in the plug flow regime. And the parameters that affect the same and some explanation into the behavior.
Thanks in advance.
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Can we use tri-vector meter to measure bidirectional AC power flow?
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Tri-Vector meters cannot measure bidirectional power flow. Only advanced digital meters used in smart distribution system can do it.
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According to my study, single phase model works better under Developing flow condition while for Fully developed flow its not work better. Because once the flow is developed the velocity profile for fluid with particles and without particle is almost same because single phase can not compute slip velocity. I used Mixture model for fully developed flow and get better results.
So, according to me for fully developed flow (hydraudynamically and thermally) two phase model predicts better compared to single phase.
What are your thoughts on this?
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Sorry. I thought, it was mixing of fluid with particles. For nano particles, the flow interaction between fluid and particles is very little. 
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dfig based wind turbine
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Dear Khaled,
Bidirectional flow in a DFIG-based wind turbine is almost typical as it is related to the sub-and super-synchronous modes operation of the DFIG (see the attached paper).
Regards,
Mohamed
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I want to identify cycling voltages for my non-aqueous redox flow cell. Does Cyclic voltametery can help me to get the charging-discharging voltages of my redox cell.
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Hello.
I need to calculate flow rates from precipitation and temperature data.
What software do you recommend?
Thanks.
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I think you can use SWAT Cup software
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Hi I need help, how can I simulate a flow using interFoam where both gas and liquid flow into a rectangular column with different velocities from different inlets. Pure gas enters from one inlet and liquid enters from another inlet. Any suggestions?
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Dear Vimal Patel,
Your work is quite interesting  and was very useful to me. I was a bit confused about the way the fluids are treated by interFoam. Now it's evident that interFoam treats two phases as a combined mixture and hence single momentum equation. Thank you for your valuable info :)
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I am little confused about the meaning of thermal plumes and convection currents. As thermal plumes is flow driven by buoyancy effects, while convection currents is also flow driven by the density difference. Both are same or some difference is there ?
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Dear Dr. Rajesh Choudhary,
Please be patient with my lengthy and boring explanation....here goes....
Assume a rectangular cavity with length four times it's height. Heat the bottom....insulate the side walls....keep the top at a lower temperature compared to the bottom. Assuming air inside the cavity, it will so happen that the (bottom) air adjacent to the hot wall will become lighter due to thermal expansion and move up (flow becomes buoyancy driven). Once at the top, the air would cool and become heavier and fall downwards towards the hot wall only to be reheated again and sent back to the top. 
The ensuing vortical/rotational/circuitous movement of air inside the cavity is what is called a convection current and that vortex itself is called a convection cell.If the cavity is square....through an extremely crude assumption one could expect that it would have one convection cell with size comparable to the entire domain (not true at all times). But here's the twist....
At the outset we assumed that the cavity is rectangular with length four times the height. In that case, there are multiple convection cells generated within the same cavity and the flow pattern is characterized by slender vortices (that occupy the entire height of the cavity) placed side by side. This is where the concept of thermal plumes comes up. Since the bottom is heated, hot air from the bottom has to rise up....however, with the convection cells active within the cavity, an interplay emerges between (atleast) two forces.....(a) the buoyancy effect that tries to push the hot air upwards and (b) the inertia effect induced by the cells that opposes upward motion. The hot air would only rise up at points where the buoyancy effect dominates inertia or (put more correctly) get favorably aided by inertia (momentum) of the convection cells to move up. Turns out that there do exist such points of escape....
It is common knowledge that a vortex cannot be "breached" by flows directed towards it's center....it's like a balloon....but unlike pressure (that's inside the balloon) the vortex exerts centrifugal force which "forbids" a direct flow of momentum towards it's center. In fact, the path of least resistance for any such flow is around the periphery of the vortex where the centrifugal forces (F=mv2/r) are weakest (I hope I am not wrong on this one).
For the hot air, this path of least resistance lies between two adjacent vortices where the flow is directed upwards (since adjacent convection cells are counter-rotational). Hence, a jet of hot air shoots upwards through the junction of two adjacent vortices and blooms at the top due to (combined) advection-diffusion into a two-lobed pattern....resembling mushroom clouds that form during atomic bomb explosions. Such bi-lobed structures of hot air that routinely shoot-up from the heated wall (bottom) between adjacent convection cells is what is called a thermal plume. 
I am attaching a picture from one of my simulations that will showcase everything that I have explained above.
I hope this helps.
Best regards.