Tagged Questions

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

35 views

Why is oil more slippery than water? [duplicate]

It is very well known that the higher the viscosity the higher the resistance offered. But why do we slip more on oil as compared with water even if oil has higher viscosity than water?
19 views

How does shape affect fluid flow for a given section area?

I'm a designer and I have no background in physics and have almost no understanding of fluid behavior. I've been asked to change the dimensions of a reflection chamber on a lab spectrometer. A tube ...
43 views

Heat transfer in solidification of cylindrical billet

I am trying to plot IN MATLAB the temperature profile of solidification of metal in manufacture of cylindrical billets. The metal is solidifying and the billet moves downwards as a constant water ...
228 views

How to calculate fluid(oil / hydrocarbon) loss under pressure

I'm trying to calculate the amount of fluid that would flow through an area dependant on the amount of pressure that there is. I'd also like to know the rate at which it would flow. Essentially I ...
51 views

What would be the optimal diameter of gold grains if you want to fill a pool with them and swim in it?

I was wondering, if I were to fill a pool with gold/gold dust, what would be the optimal diameter of the grains to minimalize the friction to a point at which you would be able to swim in it ((and if ...
62 views

Which came first, the Crest or the Trough?

We were dealing with 'Interference of light' the other day in class, and our teacher mentioned the 'ripples in water' scenario......and well, that [and not interference in particular] became the bone ...
15 views

Inlet with variable pressure profile

This is the first time for me here. Consider a pipe with inlet and outlet. This outlet is open to atmosphere. In CFD we can set inlet having variable velocity profile (e.x. parabolic profile) and I ...
117 views

Why does saliva on the finger give correct direction of wind?

When we lick a finger and put it up in the air, the side that is cooled is the one facing the direction from which the wind is blowing. But consider this, if we take a cross section of the finger, ie ...
33 views

Does surface tension attenuate turbulence?

Rapids and several other "white water" systems could be typical examples of turbulent motion. To describe such flows the Navier-Stokes equations must be extended by terms describing the surface ...
198 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 ...
108 views

Submerged water jet

I am trying to calculate at what pressure and speed water from a high pressure water jet will hit an object 100 millimeters away from the nozzle opening, but i can't figure it out. The nozzle will ...
56 views

How to popularly describe typical features of a “non-linear system”

To quote Physics.SE tag definition: The term non-linear or nonlinear has several definitions but is generally used to describe a system that cannot be approximated by a superposition principle or ...
120 views

Is the force exerted by the container on the fluid and the force exerted by the liquid on the container equal?

I came across a question where i was asked to find the force exerted by the walls of a frustum shaped bucket on a liquid inside it . I found the force exerted by the liquid on the walls of the bucket ...
297 views

Liquid column “recoils” in a sealed cylinder when hit by a piston — is it possible?

Consider a cylinder filled partially with a liquid (e.g. water). The cylinder is sealed, and is at held at room temperature (e.g 298K). At equilibrium (or when no external disturbance is imparted to ...
34 views

Rotating droplet of liquid

I'm interested in the fluid dynamics of a spherical droplet of liquid whose surface is forced to rotate at a constant velocity. I'm interested in either steady-state solutions (the internal flow ...
224 views

What is the physical fundamentals of Pascal's law

Pascal's law or the principle of transmission of fluid-pressure (also Pascal's Principle) is a principle in fluid mechanics that states that pressure exerted anywhere in a confined incompressible ...
108 views

If the surface tension is reduced to half(say by using a surfactant), what would be the effect on the size of an air bubble in the liquid

If I reduce the surface tension to half of the original value, what would be the effect on the size of an air bubble in the fluid? What would be the effect on buoyancy and drag forces? Also, if I ...
601 views

Silicone tube with three holes, flow rate, pressure

I have a silicone tube -- a saline solution flows in from one end, and then flows out of three holes of equal diameter and equal distance from each other that are along the side of the tube. What can ...
154 views

Ball Rotating in Place Under Waterfall

https://www.youtube.com/watch?v=Khf6koh3IO8 Can anyone help me explain this? It seems like the ball should shoot out from underneath. I have two main theories. 1) Bernoulli's Principle says that the ...
67 views

How much pressure would I lose on one side?

The equation for the gas flow rate (in pressure*volume/time units) $$Q = {kA\over d} (p_1-p_2)$$ where $A$ is the surface area, $d$ the wall thickness, $p_{1,2}$ the pressures on either side of the ...
103 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 ...
31 views

Working out Stokes' law [migrated]

A couple of weeks ago my professor gave me a paper on Stokes' law and how to derive it from the equations of motion and continuity. (http://www.ux.uis.no/~finjord/pdf/flu/stokes.pdf) In one of the ...
17 views

DPD weight function

I was wondering about the connection between the weight function of the random force and the conservative force between DPD particles in a standard DPD simulation. Both usually have the form [Groot ...
47 views

What happen when you stir a cup of coffe?

I have a cup of coffe, i add sugar to it and then i stir it. Why the flavor is homogeneous in all the liquid? I would expect to see the distribution of sugar following lines arround the fluid and not ...
34 views

Sound wave dissipation near a solid body

In this answer to a Physics.SE question I found the following intriguing comment: Under typical conditions the sound absorption length is quite long, and not that much heat is produced. A more ...
166 views

What is the total velocity/force on a particle in fluid?

I am now facing a fluid-particle interaction problem. I would like to simulate particle motion in a fluid. I do know the external force acting on a particle (dielectrophoretic force in this case) ...
20 views

Can more than one vortex form around a bathtub drain and what determines position?

I don't think I have ever seen more than one "vortex" or whatever you call the tornado-like helical thing that forms when water is draining from a tub. Is the position a function of the shape of the ...
269 views

Application of Stoke's Law

I was looking at Stoke's law and it says that you use it to calculate the drag force on a sphere passing through a fluid. Can i also use this equation to calculate the drag force on a car going ...
42 views

Wind Flow Simuation Equation

I have a data that contains pressure measurements in difference locations. Now i want to do wind flow simulation based on the pressure difference between these places. The problem is i want to do this ...
336 views

Fluid dynamics tsunami

I have been given a energy head (pressure) in meters for a given tsunami on land. If the tsunami hits a wall 1 meter by 1 meter, is it possible to calculate the height it will reach. I am thinking it ...
39 views

I am studying a 2D flow and I have a resource telling me that the following holds true for streamlines in general. Let $f$ be the density of the flow, and suppose there exists a unique streamline ...
651 views

Solve unsteady state Bernoulli equation for flow in a pipe

I am an engineer studying an unsteady-state flow through a pipe. The Pipeline has been cleanly cut into two halves, without deforming the cylindrical form of the pipe, exposing the contents to ...
313 views

Maximum hole size to stop a fluid passing through a solid

In a previous question, the following is answered in a general sense: Assume I have a inverse cone which holds 200ml water. I am going to cut the tip of the cone to create a small hole. How to ...
7k views

Are there any liquids with zero surface tension?

Having read the Wikipedia page on superfluids I'm still not sure if stuff like liquid helium at the lambda point actually have surface tension or not. Is superfluidity the same thing? And are there ...
276 views

Maxwell-Boltzmann distribution for transport equations

I have to calculate the transport coefficients for the Maxwell-Boltzmann distribution. But I'm not sure what distribution I have to use. As far as I know it should not be the MB distribution for $v$-...
620 views

Pipe in a flowing river problem

I'm working on a certain problem in fluid mechanics, which isn't really my strongest area. The problem is as follows: Curved pipe is partially submerged in a flowing river so that one end is pointing ...
87 views

Equal transit time fallacy and Newton's laws of motion

I've seen the equal transit time theory being used to explain aerodynamic lift [basis is Bernoulli's principle] several times. However recently I've been told that there is NO physical compulsion for ...
75 views

563 views

How does the dissolution of salt affect the solution density?

Suppose you have a container of water as a solvent and you a certain amount of salt as a solute sitting at the bottom of the container that has yet to start dissolving. Supposing temperature and ...