Questions tagged [fluid-dynamics]

The quantitative study of how fluids (gases and liquids) move.

Filter by
Sorted by
Tagged with
0
votes
0answers
36 views

How can I calculate the potential energy between two reservoirs of differentially pressured air held by water?

Ahoy digital heroes! I'm getting in a right tangle with the below, any help or suggestions would be deeply appreciated. SCENARIO Two identical chambers are partially submerged in an infinite volume ...
1
vote
1answer
32 views

How to determine the resultant velocity and height of flow from a vertical stream of water?

For a vertical flow of water that comes into contact with a horizontal surface (eg, water from the tap hitting the base of the sink), given the volume flow rate of the stream, how can I calculate the ...
0
votes
1answer
12 views

Pressure Forces acting on a Hemispherical tank

I am asked to estimate the force due to hydrostatic pressure exerted to a hemispherical container as shown below, due to the fluid which fills the container to $h$. I first parameterized the surface ...
0
votes
0answers
10 views

Pressure required to clear air bubbles in break lines

It is really tough to manually bleed brake lines for my bike because there are air bubbles where the lines bend. So I was wondering what whether the pressure required to push them out is somehow ...
1
vote
1answer
22 views

Which direction will a truncated cone be pushed by airflow?

Consider the shape below, with the bottom and top faces being holes. Imagine we hold the shape in place and blow a wind into the big hole. The air will exit the small end at a higher velocity due to ...
1
vote
1answer
30 views

Radial component of velocity in a Rankine-vortex

A Rankine vortex is a model of a vortex that assumes an inner region ($r<R$) with constant vorticity, $\omega_0$, which rotates as a rigid solid, and an outer region ($r>R$) with zero vorticity, ...
0
votes
0answers
30 views

How can we mathematically express the shape of liquid surface generated by a partly submerged body moving through that liquid? [closed]

Imagine a car moving through a flooded area. As it moves it causes the water in front to rise and level behind it is decreased along with changes in the side. What can be said about the nature of the ...
-1
votes
0answers
52 views

Are complicated equations and mathematical expressions really meaningful and realistic for explaining physical processes? [closed]

To further explain my question: One of the principles about doing scientific research that I will never forget, is the Occam's razor. Many famous scientists in the history also said something similar ...
0
votes
1answer
43 views

What exactly is $h$ in the bernoulli equation?

I've started with some very basic fluid dynamics, basically what's in Khan academy. The Bernoulli equation, from what I know, relates the pressure to velocity at two different cross-sectional areas of ...
0
votes
1answer
60 views

When you reduce the pressure of a liquid below it's saturation pressure within a container, does it boil or evaporate?

I was playing around with a compressed air can, and it made me think of the greater physics behind what actually happens when I pull the trigger. I know that compressed "air" cans actually ...
1
vote
0answers
23 views

Conservation of Angular Momentum of an Inviscid Fluid

I was trying to prove that the angular momentum of an ideal MHD plasma, defined by $\vec{L} = \int \rho \vec{r} \times \vec{u} \ dV$ is conserved when there are no external torques. That is: $\frac{d\...
0
votes
0answers
30 views

Any lecture notes or easy explanation of Holton's Meteorology?

I am struggling with understanding Holton's Dynamic Meteorology. Any lecture notes based on the book with easy explanations will help.
0
votes
1answer
31 views

Pressure gradient term at low Reynolds number

I was going over the derivation of the dimensionless Navier-Stokes equation, which is explained in this answer. By introducing dimensionless variables in the NS equation, one gets $$ \frac{D\mathbf u}{...
0
votes
1answer
21 views

Viscous flow over a perfectly smooth surface

Can a viscous liquid flowing over a hypothetical perfectly smooth surface exert viscous stresses on the surface? Can the viscosity of a fluid describe interactions between the fluid and some other ...
0
votes
1answer
29 views

What is the relationship between velocity and time of an object gliding through water?

I took a video of a swimmer pushing off of the wall and gliding through the water until they come to a stop. Using some video analysis software, I was able to plot data points for their velocity over ...
0
votes
1answer
18 views

How can I calculate the pressure at an arbitrary distance from an active spout pumping a compressible fluid?

Say I have a vent pumping a compressible gas into a room. The newly arrived gas will push the existing gas out of the way to an extent. But also both the new and existing gasses will become compressed....
0
votes
1answer
29 views

Can Brownian motion explain why white smoke moves around in the air?

Can Brownian motion explain why white smoke (fume) generated by chemical reactions moves around in the air?
4
votes
1answer
216 views

What does ultra-rarefied gas mean?

Without using any math, can you explain to me what a rarefied gas is? And then what an ultra-rarefied gas is? I'd like to understand it from a conceptual level if you can make connections to other ...
1
vote
1answer
25 views

Conservation of mass from material derivative

Let the mass be $m=\rho \text{Vol}$, where $\text{Vol}$ is the volume of the domain and the velocity is $u$. Applying the material derivative, then $$\frac{Dm}{Dt}=\frac{\partial (\rho \text{Vol})}{\...
2
votes
2answers
56 views

What does $ \mu \nabla^{2} \vec V$ mean in the Navier-Stokes equations?

$$\rho\frac{D \vec V}{Dt}=-\nabla p+ \mu \nabla^{2} \vec V+\rho g$$ In the Navier-Stokes equations there's this term $ \mu \nabla^{2} \vec V $. I don't really understand what this means. What is the ...
0
votes
0answers
18 views

Euler equation in cylindrical coordinates for axisymmetric fluid flow

The Euler equation in fluid dynamics for spherically symmetric fluid flow reads $$v_r\frac{dv_r}{dr}+\frac{1}{\rho}\frac{dp}{dr}+\frac{d\Phi}{dr}=0,$$ where, $v_r$ is the radial velocity and $\Phi=-1/...
0
votes
1answer
17 views

Maximum height of the water emerging from a sprinkler

The water in a garden hose is at 140 kPA gauge pressure and is moving at negligible speed. The hose terminates in a sprinkler consisting of many small holes. Find the maximum height reached by the ...
0
votes
2answers
60 views

Why can't water flow fast when the impact speeds up? (the incompressibility)

I'm a high school student studying physics in Korea! Please understand my poor English skills. In the text below, the liquid is said to be destructive and incompressible. And he says, "I the ...
1
vote
2answers
27 views

Water flowing after turning off pump

I'm pumping water with a mini pump through a plastic hose (1 meter), between two glass containers. My problem is that if I turn off the pump when the water is flowing through the entire hose, water ...
0
votes
1answer
25 views

Newborn suction force on syringe

Just had a newborn. He requires assisted feeding through a syringe connected to a small catheter. We place the small bendy catheter in his mouth, so he, simulating natural lactation, sucks the milk ...
2
votes
2answers
105 views

What is (local) pressure within a gas on the microscopic level?

Fluid dynamics view Fluid dynamics describes liquids and gases in terms of local pressure (among other variables), which varies from a point to point. While mathematically the concept is well-defined (...
3
votes
0answers
92 views

What allows this tornado to form in a frying pan?

I have just seen this video here where a mini tornado has formed in a frying pan: https://www.youtube.com/watch?v=6CJ-8ze2FjE Does anyone know how this happens or where I can find an explanation?
1
vote
0answers
20 views

How can i predict the amount of time it would take for my heron's fountain to stop? [closed]

I was assigned a project for my physics class and I'm supposed to build a Heron's fountain and to predict the time it would take to stop so I can then check it experimentally. However, I'm unsure of ...
1
vote
0answers
38 views

Sizing pipes for a filter system with two pumps and one inlet and outlet, bernoulli and venturi?

I need help with a concrete problem that needs solving through good application of physics principles. Here's the problem: I would like to build a filtering system for my bestway pool, the pool has ...
0
votes
1answer
28 views

Steady flow of a fluid observed in different reference frames

My question is that ,is it possible for a fluid to have steady motion in one frame and non steady motion in another?
0
votes
1answer
31 views

Analyzing Magnus effect from ground frame

How can we explain Magnus effect to the path deviation of a spinning ball assuming the air is still (looking from ground frame)? I understand that we can use bernoulli principle from ball's frame, but ...
0
votes
0answers
13 views

Is there a characteristic time interval where the continuum assumption doesn't hold?

From my understanding the continuum hypothesis for a fluid doesn't hold in two cases: if the particle body / control medium that is being examined approaches the size of the molecules in the system or ...
0
votes
1answer
37 views

Could you siphon water from a column of water that is supported by buoyancy?

A cylinder with a radius of $10 \;\mathrm{m}$ and a height of $10 \;\mathrm{m}$ is resting on top of a body of water. The cylinder is less dense than water. At the center of the base (equal to water ...
1
vote
1answer
40 views

Normal Shockwaves and its Thermodynamics

Please read this page before going to my question. When we derive the relation between Mach no. to the left side of the shock wave (M1) and that to the right side of the shock wave (M2),we do that ...
2
votes
2answers
44 views

Since the pressure in smaller bubble decreases why does its radius decreases and not increase, as it should, in the "communicating bubble" experiment?

If we blow two soap bubbles from two communicating pipes with funnels at the ends (see the fig) and close the tube to which they are connected, air will flow from the smaller bubble to the larger ...
0
votes
0answers
22 views

Leaking water from leaky pots

I have two absolutely identical pots with round bottoms. Each bottom has the same number of absolutely identical holes drilled in it. In the first pot, all the holes are quite far apart, while in the ...
0
votes
0answers
29 views

Relativistic hydrodynamics in cylindrical coordinates

I am interested in the study of 'axisymmetric' fluid flows around a compact object in general relativity. I am using the polytropic equation of state, $p=k(s)\rho^\gamma$, and the matter is assumed to ...
0
votes
1answer
49 views

Why doesn't Hydraulic pressure pull two cylinders apart?

Assume as simple hydraulic fixture as shown below. Where the pipe or hose connects the two, there is a missing area on each cylinder. Wouldn't the hydraulic pressure then create an unbalanced force on ...
1
vote
0answers
12 views

How to calculate the Euler equation for fluids in the newtonian limit from the stress-energy tensor?

I have been working through the exercises of Schutz's a first course in general relativity. In chapter 7 of the book there is a question about the conservation of the spatial components of stress-...
0
votes
0answers
19 views

Doubt related to venturimeter

We connect one limb of manometer at inlet of converging section and other at throat but why we don't connect one limb at throat and other at end of diverging section, is there any problem if we ...
0
votes
0answers
27 views

Why laminar flow does not produce pouring sound while turbulent flow does

I observed in a newly installed tap that it doesn't produce the pouring sound of water (due to a fine mesh on its mouth as I guess) which made me think that it is related to the type of flow (laminar ...
0
votes
1answer
55 views

Floating of steel plate in water

Consider a steel plate, in which orientation will it float in water 'horizontal or vertical' ? According to me in horizontal orientation plate will float but in vertical orientation it will not float ...
0
votes
0answers
64 views

What was the need for defining kinematic viscosity?

How is kinematic viscosity physically different than dynamic viscosity? What was the need for defining a new quantity ie kinematic viscosity though one can get one from the other? Do try to give a ...
26
votes
3answers
5k views

What is cold wind?

As per my understanding, temperature is the movement of particles in an environment. A highly energetic environment where particles possess high energy has a high temperature, and low energy means low ...
0
votes
1answer
35 views

Why don't the molecules on the surface of a water drop get pulled down to the bottom of the drop?

When discussing about surface tension, it is said that the surface water molecules experience a net downward cohesive force. If they experience such a force, then why don't the surface water molecules ...
0
votes
0answers
28 views

Why does a garden hose keep its shape when pressurized?

According to the linear momentum equation (time-independent), $$\Sigma F = \int_{\partial V}dA\bf{V}\rho\textbf{V}\cdot\textbf n$$a u-bend in a garden hose will cause a net force acting on the bend. ...
0
votes
0answers
7 views

Blade angle/design for the high lift to drag ratio

For my high school science fair project I'm trying to build an underwater turbine that would generate the most power. I decided that I would want to find the blade design with the highest lift to drag ...
0
votes
1answer
27 views

Stoke law determend the viscosity of liquid

In an experiment to determine the viscosity by the Stoke method. When we throw the ball into the liquid it will reach a certain mark and start recording the time. This mark what determines its ...
0
votes
0answers
18 views

How can the conservation/Navier Stokes equations (mass, momentum,energy) be modified to model two phase flow in a porous media?

Previously I have seen the derivation of the energy conservation equations for simulation of single phase flow in a porous media (a packed bed). These are the energy equations for the solid and fluid ...
0
votes
2answers
25 views

Can ionized air be used to create airflow without fans or other moving parts?

If I understand it correctly, ionized air should produce an electromagnetic field, which should mean that it can be attracted/reppeled by another field of the oposite/same charge respectively. If so, ...

1
2 3 4 5
115