Turbulence Definition and 81 Threads

Hey PF! I was wondering if any of you were familiar with structure functions and how they relate to turbulence? Do you know of any good articles to research? Structure functions may be defined as $$S_{ij}(\vec{R}) = \mathbb{E} \Big[ \big( u_i(\vec{x}+\vec{R}) - u_i(\vec{x}) \big) \big(...

Turbulent fluid has more energy (mass) than laminar fluid?

As you can see, around Reynolds number of 5 105 the transition occurs for a smooth sphere. However, why is it that after this transition that the drag coefficient increases at turbulence?

I was discussing this with my friend the other night. I mentioned that proving existence of smooth solutions for the Navier-Stokes equations would win a $1,000,000 prize from the Clay Mathematics Institute, and also that turbulence is considered one of the unsolved problems of physics; as a...

Hi, I have built an 8' long wind tunnel for use in an experiment to test the effects of turbulence on several variables. However, seeing as this is an educational-level/novice wind tunnel with a fan rating of ~1800 cfm the wind speeds only really go up to ~10 mph. From my understanding, this...

I am measuring a 2D turbulent flow using a split film probe. This gives a time history of the velocity in the x and y directions. I have a few questions about obtaining energy spectra from these measurements that I am hoping someone can help me with. The energy spectrum of the turbulent flow is...

At the moment, I am reading about fluids and the drag force. There is one particular paragraph that I would like help with, specifically the part in red: "Here we examine only cases in which air is the fluid, the body is blunt (like a baseball) rather than slender (like a javelin), and the...

Just out of curiosity, is there a limit to how turbulent a flow can become? In otherwords, turbulence develop that is so chaotic that no discernible pattern/path can be found in the flow? Thanks.

Here is a glimpse of my current research. This is a kinetic simulation of electrostatic waves in a bump-on-tail plasma, with multiple resonances and some dissipation. Quasi-linear theory predicts a flattening of the velocity distribution over the range of resonant velocities of linearly unstable...

Turbulence -- just a phenomenon of cavitation? Is turbulence exclusively cavitation of a fluid? Please give me your insight on this idea.

Hey does anyone know where I can access some of these either for free or if my school has a subscription then I can access them on their network. I will be joining a research group soon on the simulation of heat transfer in a tokamak and would like to be up to date with the literature.

I've heard it said that 'we don't really understand turbulence', and that it is one of the biggest outstanding problems in classical physics right now. (Or at least Feynman thought so back in his day) But what is there to understand about turbulence and why don't we understand it? I thought...

How fast do i need to pump water in a 10" aluminum pipe to prevent freezing? Assume 32*F inlet temp and 0*F ambient . For my conditions, the temps will vary and T ambient easily gets down to -20*F or more.

These are two rather unrelated questions but I am curious. 1. How much does physics rely on engineering? I think it's pretty clear that modern engineering relies pretty heavily on physics. Without it we wouldn't have electicity, chemicals, or even know the amount of force and heat we are...

Evening out turbulence in a 3" pipe Hi folks, I have a small problem. In my car I'm building new pipes for the pressurized air. On a straight pipe there is a MAF sensor (Mass Air Flow). It consists of a hot wire and a temperature sensor. After the pipes were redone and the MAF sensor was...

As ole' Feynman said: "Turbulence is the most important unsolved problem of classical physics." So why is it so, that this everyday phenomena is so little understood by scientists?

What is the equation to estimate the turbulence kinetic energy per unit volume in pipe flow? Any information is appreciated. Thanks.

Right now I think one of the key problems with confining fusion in a tokamak is that turbulence is generated within the plasma. I was wondering if it were hypothetically possible a hypothethical nanomachine to control the random bombard of atoms that create turbulence and thus cease turbulence...

Does the critical temperature Tc of superconductivity suggest a similar parameter at the juncture between mechanical laminar and turbulent motion? In other words, is there an analogy between the electronic change at Tc and critical change in fluid flow at "room temperature"?

Hi there Can anyone provide me with an explanation of what a wavenumber is, and how it can be used in determining the extent to which energy is dissipated during turbulence (ideally in the context of the ocean)? I am aware of the basic definition of a wavenumber (i.e. the reciprocal of wave...

Hi guys. I know turbulence is a b($#H when trying to explain and often poses problems in flyid dynamics. However, our university lecturuer has thrown this at us to think about as it's a pretty interesting topic and I thought there might be some people out there that have ideas about it...

A smooth surface aborbs less sunlight than a rough one because more light is reflected. It takes relatively little energy to disturb a smooth surface.If the sea becomes more turbulent because of a changing wind direction or wind speed does the sea heat up more by absorbing more sunlight.And...

hello I wanted to know what happens to the level of turbulence when air pass through a 90 degrees pipe bend (where in the bend turbulence is greatest). I want to design a pipe to reduce turbulence through 90 degrees. I know its obvious that level of turbulence increases but i am puzzled as...

I took a recent flight from LAX to SFO on an Airbus 319 and noticed that there was a lot more turbulence than normal. So much so that the plane had to fly at its service ceiling, and even then, there was a good amount of shaking. I even had a mini panic attack and had to call a flight attendant...

Is there a formula for turbulence pressure that is a function of temperature ( in the convection zone of a star )?

Turbelence and modeling of this phenomenon are areas of professional interest, in addition to CFD and fluid-structure interaction. CFD-online is an excellent reference source for topics in CFD. I came across their Wiki and thought this might be useful...

Just to the point How to calculate Re number? in example for calculating Re number at diffrent points in a boat. How turbulence affect drag? I know simply turbulence will increase the drag but, to what extent; or simply, the formula connecting both. Comparing the drag between turbulence...

When one tries to have an insight into what the turbulence regime really is, one comes across the question of: is the turbulence a deterministic process or not? Even though we are able to simulate accurately turbulence with Direct Numerical Simulation (DNS) of the Navier-Stokes Equations, it is...

Well, the other day I saw a solution of a DNS (Direct Numeric Simulation) of a turbulent flow. My questions are a bit phylosophical, so that if I do not obtain some opinion in some day in this forum, it will be not a strange thing. -The turbulence is inherently three-dimensional and...

Hey I came into a doubt in the classical physics forums, and I want to know if I said something stupid. Usually we employ in Fluid Mechanics the adherence condition (u=0 just on the wall, where fluid and solid meets; u=velocity field). But I'm not sure if in turbulent regimenes this keeps on...

Hi all, the other day I was in a thermal bath where they had some whirlpool jets at the bottom of a basin about breast-deep. I was standing right over the jets, and the turbulence in the water was so strong at the surface, that I couldn't stand straight but was forced to sway back and forth and...