The quantitative study of how fluids (gases and liquids) move.
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66 views
Why is there no UV catastrophe (divergence) in turbulence?
I have just read that as the Reynolds number is increased, the separation of macroscopic and microscopic scales increases and that this also means that there is no UV catastrophy (or equivalently UV ...
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105 views
Can a divider “laminarize” turbulent flow and thus reduce friction?
Looking at the Moody chart I think to myself, the friction factor doesn't decrease much at all with Reynolds number after a certain point. I wonder if laminar flow is more efficient in a sense, and ...
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63 views
Atmospheric Circulation
What is the simplest simulatable model giving our rotating earth its 3 circulation cells (Hadley, Ferrel, Polar)?
The model should also show 1 circulation cell if the earth's rotation were stopped (or ...
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122 views
Why does the milk frother on my coffee machine make so much noise?
I have a Sunbeam home espresso machine with a steam wand. The steam roars out straight from the end of the wand. When it's first placed in the cold milk it really screams! Once the milk has a bit of a ...
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212 views
What's the efficency of a steam jet pump?
Jet pumps or venturi pumps are often stated as having a "terribly low" efficiency, steam jet pumps specifically are usually describes as "only justifiable when there's an abundant steam supply anyway" ...
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53 views
Sound level of organ pipe driven by helium
The sound pressure level of an organ pipe is a function of the gas flow rate delivered to the pipe. Source
Would the sound level of an organ pipe driven by helium be lower than that of a pipe driven ...
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54 views
How do Kolmogorov scales work in shear thinning fluis?
My understanding of Kolmogorov scales doesn't really go beyond this poem:
Big whirls have little whirls that feed on their velocity,
and little whirls have lesser whirls and so on to viscosity.
...
3
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155 views
Flow behind a plate causes pressure drop?
I've done an experiment where we direct an air jet from a fan onto a set of electronic scales. By measuring the velocity of the air jet at the exit of the fan nozzle, and applying the conservation of ...
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39 views
Finding Surface Tension of water at certain Temperature and Pressure
So the question is:
Using the Young-Laplace Equation (if applicable), find the surface tension (dynes/cm) for water at 20
degrees Celsius with 2.5 psi. Round to the nearest tenth.
...
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33 views
Shock Rarefaction Interaction
I am interested to see/know if there exist analytical solutions for shock/rarefaction interaction. A rarefaction wave catches up from behind to a shock wave. The shock will decay and the motion will ...
2
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0answers
46 views
Robot controling pouring process from a bottle
I need to solve a problem within mechanic of fluids for a part of my thesis. Robot will pick up a bottle of beer, cola, julebrus or any other kind of beverage. And then it has to bring it to the glass ...
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51 views
Seashell occurrance
Sometimes, sea shells accumulate on the sea shore, but sometimes they will instead be dragged back out to sea. What are the main physical factors that determine which of these things will happen?
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96 views
Conformal symmetry of Navier-Stokes?
This question is in reference to the paper arXiv:0810.1545
Can someone help understand this scaling argument and the proof(?) that there is a conformal symmetry in Navier-Stoke's equation? (..am I ...
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78 views
Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model
In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
2
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0answers
60 views
Fluid flow in a hollow spring(helix)
Liquid flowing in a long hollow spring(helix). Any effects on the flow rate etc when the spring is stretched or compressed?
When the stretching or compressing of spring is done at brisk speeds the ...
2
votes
0answers
76 views
Stat mech explanation for separation of one liquid from another in gravity?
If one mixes two distinct ideal gases above the Earth's surface, one with a higher molecular mass than the other, then at equilibrium, their number density gradients will be such that at low heights, ...
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101 views
Turboshaft Turbine Mathematical Model
Are there any simplified mathematical models for how two gas coupled turbines (also called a free power turbine) should interact with one another as the speed of the driving turbine changes.
(i.e.) ...
2
votes
0answers
51 views
How does a hinge affect the amount of a submerged material?
Suppose I have a rod that has a density of $X <1$. If I were to submerge that rod in water (density 1), I would expect $X$ of the rod to be below water and $1-X$ of it to be above water (simple ...
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132 views
How to calculate the Darcy-Weissbach friction factor for shear thinning laminar flow in a pipe?
The Darcy-Weissbach friction factor for laminar flow would be $\frac{64}{Re}$
Now, having a shear thinning (non-newtonian) fluid where the viscosity is not constant how do I arrive at $Re$?
To know ...
2
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0answers
135 views
Early stages of a computational model for object movement charting
We would like to build a computational model capable of accurately predicting the position of any object inside a chamber at any given time.
Inside the model we would have a number of smaller ...
2
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0answers
53 views
Ratio of horizontal to vertical kinetic energy in ocean
What is the ratio between horizontal and vertical kinetic energy in the ocean and what is the scale dependencies of this ratio ?
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69 views
Concentration of fluid pumped through a tube?
I have a bottle filled with a fluid A, and a tube of volume $V_0$ filled with a fluid B leading away from it.
When I now start pumping fluid A out of the bottle, I am interested in the concentration ...
2
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0answers
78 views
How do I simulate a constant velocity flow in porous media
I am modelling gas combustion in porous media. Most contemporary models assume that the pressure drop from the porous media is small enough to disregard, but I want to include that in my ...
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74 views
Jupiter: Zonal Jets in opposite directions
I recently read that the Great Red Spot arises from the shear instability of zonal flow from zonal jets travelling in opposite directions.
Is there any reason why such zonal jets travel in opposite ...
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0answers
7 views
How to find outflow pressure/force of air through a pipe
I have been trying to find the correct method for determining the outflow force resulting from a certain amount of air being forced into a pipe of a certain dimension. Essentially i'm trying to ...
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0answers
22 views
What is the relationship between complex time singularities and UV fixed points?
In this paper it is described how the turbulent kinetic energy spectrum and the flatness (a measure for intermittency) are governed by the position of the (dominant) singularities of the solutions of ...
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0answers
35 views
What is a good reynolds number for this process?
I’m trying to convince my boss that the mixers we are using are too much. I’m trying to prove that we are over-mixing our product. Our product is ink…just your basic ink found in your printer at home. ...
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0answers
15 views
CMB anisotropies and tightly coupled limit
Sorry if this is a technical question. I am studying the origin of CMB anisotropies and the tightly coupled limit of the Boltzmann equations. We have a fluid composed of ionized electrons and photons.
...
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96 views
2-D Turbulence - how does it look like?
Consider parallel flow in the X direction over a 2D semi infinite flat plate. If turbulence is 2-D, in which axes should we expect the vortices to form.
Also, are there any experimental/visualization ...
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34 views
What temperatures can be reached in an air-to-air thermocompressor nozzle and why?
People are generally of the opinion that the boiler injector cannot be redesigned to run on air. In other words, an air-to-air thermocompressor that puts fresh air into a tank without a mechanical ...
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0answers
49 views
Calculating pressure in accelerated fluids in closed and open vessels?
The question asked was "what should be the acceleration such that the pressure at both the points marked by thick dots be equal? the vessel is open and cubic with side 5m?"
Initially i considered ...
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0answers
46 views
Physical interpretation of an intermittency definition
A random function $v(t)$ is said to be intermittent at small scales of its "Flatness" $F$, given as
$$
F(\Omega) = \frac{\langle (v_{\Omega}^{>}(t))^4\rangle}{\langle ...
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22 views
blood fluidics - can you determine the force exerted on a bound red blood cell under shear stress?
Is it possible to calculate the force exerted on a bound, infected red blood cell under various shear stresses? The strength of an adhesive interaction is normally measured by SPR or AFM, however ...
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29 views
where to find sample fluid stirring data?
I want to find some force data for fluid stirring. Originally I intended to record the data using my force sensor, but it doesn't have the resolution to read stirring force for Newtonian fluid.
...
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73 views
Wall pressure of a fluid flow in a pipe of variable radius
Using all cylindrical coordinates, pipe with z-axis vertically upward and radius of $r = G(z)$, flow is incompressible, inviscid and steady, Using appropriate boundary conditions I want to find the ...
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43 views
Is sonoluminescence relevant to the behaviour of Navier-Stokes (or converse)?
More precisely, could Sonoluminescence be a singularity of Navier-Stokes(NS)?
Is there some other connection that might be interesting, or is it completely irrelevant?
Wiki page mentions NS, but says ...
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98 views
Mechanical effects of convective flow in steady-state stagnant film diffusion
When analysing diffusion problems in the context of the simplified film model, two limiting cases are ussually introduced during the solution of the differential chemical species mass balance ...
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166 views
Venturi in nozzle of water jet
I am trying to understand a waterjet system for maneuvering boats from a physics perspective. (See Marine Holland Parts if you are interested.)
The system uses venturis in the nozzles. My question is ...
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0answers
296 views
propeller flying physics for the layman
I'm starting a (quad?)copter build, and i can find plenty of knowledge about stabilizing the craft and things related to gyroscopy.
but there's absolutely zero information on things that help me ...
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79 views
How does a particle move in Water?
Is there any precise model (More precise than the random walk model) that describes a particle's movement in water ?
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123 views
Why is my ballpoint pen spatially temperamental?
I'm trying to write with a ball-point ink pen on a plastic[1] sandwich bag. When I try to write on some parts of the bag, no ink transfers to the bag: I can continue trying for quite a while in vain. ...
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0answers
35 views
What is the fluid approximation for BCS action?
For a system with free fermion gas at finite density (i.e. free Dirac action),
we have an ideal fluid description with rho, p, n.
What is the fluid description for BCS action?
Suppose we have a box ...
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101 views
How to integrate twice of this viscous term?
I am reading a paper, and I do not understand why the author said the following term when integrated twice will become,
$\int\limits_\Omega {{\rm{d}}\Omega {{\bf{\psi }}^{\bf{u}}}\cdot\nabla ...
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64 views
Discharge of a propeller in a yield-stress liquid
What form does the discharge stream of a propeller take in a Herschel-Bulkley fluid, chracterised by having a certain yield stress, shear between layers only occurs beyond that stress.
This situation ...
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280 views
Do the properties of two streams flowing into an engine add together when they mix?
Let's say I have two stream supplys that have separate mass flow rates, enthalpies, and velocities that flow into an engine. Upstream of the engine's inlet, the two streams mix to form one stream that ...
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0answers
110 views
How do I determine where the maximum air velocity around an object is?
I have a freestream of air directed at an object. Is there a way to find where the maximum air velcoty occurs with only having initial air speed and static pressure at the object?
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0answers
590 views
What's the meaning of a pressure coefficient in fluid mechanics?
I have a jet of air leaving a contraction from a pressurized tank at a velocity of 28.8 m/s and it's being directed towards a small object equipped with static pressure holes on its surface that give ...
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226 views
Creating the proper suction
I'm a bit rusty on my fluid dynamics. I'm experimenting with creating my own leaf vacuum.
How would I determine how much suction a fan creates?
Bernoulli's equation would apply correct?
I would ...
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votes
0answers
25 views
Absolute Viscosity of Water at certain temperatures
I just started my class on fluid mechanics. There's a problem that requires absolute viscosity $u$ of water at 25C. I looked up my table in the book and I only have it for water at 20C and 30C. I ...
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13 views
What type of constraint is the homogeneity of a fluid?
Suppose we have a homogeneous fluid (may or may not have viscosity). Is the constraint due to homogeneity a holonomic constraint? Thanks.
