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# Questions tagged [flow]

The motion of fluids (gases, liquids and granular material).

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68 views

### What is irrotational flow? How to judge?

For example, when the wing moves horizontally, the direction of fluid flow changes first to upward at the leading edge of the wing and then to downward at the trailing edge. Does it rotate? If the ...
35 views

### calculate CFM of a ceiling fan

I'm trying to calculate, or even understand what data do i need to calculate the CFM of a ceiling fan. in many countries this is a given data in the product details but not where I'm from. I have the ...
18 views

### Acoustics air flow vs the human body

My question to you all is... Is it possible to move air acoustically. ie to move air over a 2.1m distance to be felt by the human body with a cooling effect but not heard by the human ear ? I'm just ...
91 views

### Problem estimating the flow rate in natural draft chimney using Bernoulli equation including heat and friction losses

I am trying to build a simple model for fluid flow and heat transfer in a natural draft chimney. I've found some literature about it (most of them giving the same result as the equations on the ...
50 views

### Why does blood pressure drop when blood vessels rupture?

Some people say that because the flow is large, the pressure is low. Is that right? Why does the pressure drop when the flow rate is high?
31 views

### How to measure flow rate using Toricelli's law?

For my experiment, I want to investigate the relation between height and velocity using Torricelli's law. I would like to know how I would measure the flow rate from volume in a spouting cylinder.
62 views

### Viscous losses in loop helical flow

Imagine flow of the following kind. The flow line for each flow particle is a helix with its axis bent so that the beginning attaches to the end. How can I determine the viscous losses in this flow ...
110 views

### Do drones fly because of low pressure above them or high pressure below them?

I was working on some drone battery life solutions and was stuck with the question whether drones fly because of low pressure created above them by the rotor or due to high pressure created below them....
50 views

### A doubt on this paper regarding Ricci flow on space-time

https://arxiv.org/abs/1812.06239 In this paper,the authors use ricci flow to construct Lifshitz spaces. But it is known that ricci flow is limited by Riemannian manifold, which has a positive metric....
17 views

### Macroscopic hydrodynamics, is there a fluid “vacuum” force?

Background I was looking at the following simulated fish movement article and how the physics could be improved (ie, made more realistic) with out a huge impact on performance. It looks like they ...
144 views

### Is it correct for me to understand why air moves along a curved surface?

As shown in Fig. 1, water flows horizontally from A-A section, and it flows along the surface under the action of gravity. As long as the velocity is not high enough, the water will not leave the ...
181 views

### What does the pressure term in Bernoulli's equation signify?

Consider the Bernoulli equation of fluid dynamics. One of the terms is $p$. I know it is pressure. But what type of pressure is it? Is it pressure due to height or a completely different concept?
38 views

### Bernoulli's theorem in water flow through a burette

Consider a burette (like the one in a chemistry lab) with uniform cross-section and open at both ends so that they are exposed to the atmosphere. Once we open the stopcock/plug (P in the diagram) the ...
20 views

### Surface refresh rate

How does one determine the refresh rate of a fluid in the following example: A laminar flow of a certain (lets say 10 ml/hour) volume/time of a certain fluid goes along a certain surface area (lets ...
87 views

131 views

### Can you explain the perfume bottle with the Bernoulli effect?

Someone explained the perfume bottle with the Bernoulli effect: squeezing the bulb over the fluid creates a low pressure area due to the higher speed of the air, which subsequently draws the fluid up. ...
36 views

### simple gas flow between regions

How does gas flow between regions of differing pressures? How does the momentum of the gas effect that flow between regions of differing pressures? I am trying to program a simple simulation of gas ...
73 views

### Is it correct to use Bernoulli's theorem to explain that a disk floats in the air? Should the correct explanation be based on Boyle's law?

In this video, a device is introduced from 1 minute to 18 seconds. After entering the air, the disc at the bottom of the device will be suspended in the air. The video explains that this is because of ...
72 views

### How can I calculate the speed at which a gas flows from one volume to another?

Suppose that there are two rigid Volumes A and B. Each of these contains a gas with know properties (pressure, temperature, number of moles, volume, composition). Suppose also that there is a pipe ...
71 views

### Gas Flow Between Two Pressure Vessels

I am trying to determine the volumetric flow rate between two pressure vessels at different pressures and volumes. Nitrogen gas is stored in a K bottle at 2640 psi (P1)and 3045 in$^3$ (V1). The tank ...
70 views

### Replace warm air with cold air

In summers i.e. now, my room has hot uncomfortable air in night,but outside air is cold 4-5 degrees Celsius colder than inside, my room has windows parallel to wind flow, so though wind flows in night ...
216 views

### Why can water be sprayed farther when the pipe outlet is narrowed?

Someone told me: This is because the flow rate remains unchanged, so the flow rate of small diameter pipelines is faster. I don't think this explanation is right: the diameter of the pipe outlet is ...
99 views

### Can Bernoulli Equation be applied across two fluids?

There is a beaker with two liquids placed above another. The beaker has a hole at bottom. So can I use Bernoulli equation across the interface of liquids.
117 views

### Complex Potential describing inviscid fluid flow

I'm a Mathematics student, working through a homework sheet for a Fluid Mechanics module. The question is given: Consider the flow described by the complex potential $$w=4z+\frac{8}{z}.$$ ...
37 views

### Which way does the fluid flow? [closed]

In the given siphon arrangement if a hole is made at D, will water leak out or will air leak in? I think air should leak in as fluids flow from high to low pressure but I'm not sure... Any help ...
31 views

### Potential Flow integration (no-voice and very beginner!)

Let's say I managed to compute a velocity field that is divergence-free. How do I integrate it over time? meaning, I created a potential function, set v to be curl of potential function, so I have now ...
168 views

The energy loss in a hydraulic jump is still calculated with the old equation of Bresse from year 1860; (I.e., equation 7 in this paper from 2017) $$\frac{\Delta E}{E_1} = \frac{(\sqrt{1+8Fr^2}-3)^3}... 1answer 106 views ### Why does the flame of a gas stove not spread backwards? On lighting a gas stove the flame is active only above the burner. However, the gas input from beneath the burner and all the way to the pipeline contains gas fuel. Why doesn't it all ignite up ? I am ... 2answers 169 views ### How pressure and velocity is related? And its effect in cavitation As per my knowledge I think when velocity increases and discharge is constant,the fluid(liquid) molecules get away from each other in the region where velocity is high and that's why they get ... 1answer 65 views ### Bernoulli Experiment- why is the pressure on the left greater? [closed] Is the Pressure P_2 caused by a reaction force to the fluid-fluid collision, or is it the result of the collisions of the water molecules with the walls at the neck of this experiment. The part ... 1answer 47 views ### Energy balance in a thermodynamic system I think I've missed this point in class but I was wondering how to determine for example if I have a turbine, the Energy balance would look something like this: W as work h_1 as intake and h_2 ... 1answer 45 views ### Expression of mass flow rate for steady flow According to Wikipedia the mass flow rate is given by:$${\dot {m}}=\iint _{CS}\rho \mathbf {v} \cdot {\rm {d}}\mathbf {A}$$And using the Reynolds Transport Theorem (if there is no sources):$$\...
In this wikipedia article about potential flow around circular cylinder, the stream function is given by: $$\psi =U\left(r-{\frac {R^{2}}{r}}\right)\sin \theta \tag{1}$$ But in another article we ...