# Tagged Questions

A regime of nonlinear viscous flow characterized by random, rotational motion with a wide range of length scales. Its study is critical to many fields, such as aerospace, atmospheric science, chemical engineering, and astrophysics.

141 views

### Pressure loss in an infinite pipe

I feel lost in this problem. I know pressure loss occurs in a pipe flow due to friction. Say given a constant diameter pipe, if we keep lengthening the pipe horizontally, and static pressure will ...
18 views

### reference request: 2D turbulence

I'm reading papers regarding the 2D Navier-Stokes equations. But I don't have a physics background. Would anybody come up with some introductory references of 2D turbulence which contain the following ...
36 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 ...
58 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 ...
75 views

### Is the flow of a viscous fluid in free space under no pressure gradient always laminar?

Consider a (Newtonian) incompressible viscous fluid in three spatial dimensions, whose velocity field $\mathbb{v}=\mathbb{v}(x,y,z,t)$ moves according to the Navier-Stokes equations \tag{1}\label{...
50 views

### Why does laminar flow turn turbulent(*) in external fluid flow and why doesn't a fully developed laminar flow turn turbulent in flow through pipes?

(*:with increase in distance from the leading edge.) I would appreciate if you give detailed explanation for the first question and then apply the same logic to answer the second.
36 views

### History of Turbulence suggestions

I am looking for extensive historical accounts of turbulence that ideally is strong in math and physics (at least giving references). Any suggestions? The only book I found is "A Voyage Through ...
32 views

### How is zonal flow defined and computed?

The transition to turbulence in pipe flow was recently observed to be in the same universality class as directed percolation. This was done by reinterpreting the turbulence and laminar flow in terms ...
25 views

### Spin on the rack

Bike mounted on hitch rack. Why wheels spin constantly while I drive? I can't find anything on the internet. The kids in the other cars love to watch them
74 views

### Why is turbulence caused?

In high Reynolds numbers we have turbulent flow. This is because the inertial forces are much greater than the viscous forces. I understand inertial forces to be actually the fictional forces due to ...
35 views

### Trouble understanding a formula in Turbulence

I'm very new to turbulence.I'm reading this book on "Turbulence: An introduction for scientist and Engineers" by Davidson. I came across this formula for energy dissipation. This is in chapter one. I ...
29 views

I am trying to read following article: http://arxiv.org/pdf/1410.1262v1.pdf According to the equation (2.10) and (2.11), the random force is defined as $\langle f_i(x) \ f_j(x) \rangle = \delta(t-t'... 3answers 43 views ### Wind restistance as function of temperature Is temperature-dependent wind resistance the reason there's a significant increase in fuel consumption in my Prius car when air temperature drops by 30 degrees K from 300 degrees K? I think I see a ... 0answers 47 views ### Plane landing into a tunnel Typical action movies cliché is landing a plane in a tunnel or even a flight in a tunnel. Let's drop any doubts about supreme heroic piloting skills of the characters etc. and focus on aerodynamics. ... 1answer 17 views ### Which are the best books I can refer for turbulent heat transfer and its computation? I am a graduate student. I wanted to do computation on heat transfer problem mainly heat convection. I am working on turbulent regime. Can you kindly suggest some good books so that I can get ... 1answer 64 views ### Turbulence in gravitational waves I want to understand physical meaning and possible implications of few terms often used in physics specially with regards to gravitational waves / space-time fabric Space-time fabric is disturbed by ... 2answers 53 views ### Is it possible that a plane in turbulences has more downward acceleration than gravity's In multiple Hollywood movies and TV shows I've seen scenes where a plane enters turbulences and for a moment the people in the plane seem to move upwards relative to the plane. As far as I know, as ... 2answers 63 views ### Is it possible to let a flag stand frozen in time? It´s clear that a moving flag is a chaotic system. But is it nontheless possible, under certain conditions and a uniform wind velocity, to make the flag look frozen in time, i.e., flat without ... 2answers 73 views ### Misunderstanding about Reynolds number I am confused about Reynolds number. I am trying to use the formula to see if NASCAR cars have laminar or turbulent flow. But I am not sure how exactly to use the equation in order to do such ... 1answer 75 views ### What is actually the characteristic length in fluid dynamics description? In many fluid-dynamics models and quantities (Reynolds number, Strouhal number... generally various turbulent flow descriptions) there is a parameter (usually$L$or$\ell$) descripted as ... 1answer 55 views ### Velocity of liquid molecules in turbulent flow I was solving some questions when I came across this: what is the velocity of liquid molecules in contact with the walls of the tube? and the answer was given that it can have any velocity and then ... 0answers 172 views ### Numerical model for a Air core Vortex, why it's still so limited? [closed] The Question can be Formally presented as follows; How is the Numerical Model (CFD, Navier Stokes) of fluid dynamics for Vortexes at in it's limits? At this Publication from 2013 at page 48 is said;... 4answers 515 views ### Does steady flow imply laminar? Most secondary school textbooks, in their chapter about fluid dynamics, seem to suggest that "steady flow" and "laminar flow" are synonyms. Though I never received any fluid mechanics course when I ... 1answer 189 views ### Flow through a rifled pipe In turbulent flow the friction is inertial for the most part: the chaotic flow causes the fluid in the faster moving center to interchange randomly with the fluid near the edge. This eventually allows ... 1answer 52 views ### Fluid flow around a cylinder For an irrotational, incompressible fluid we can solve Laplace's equation for the velocity potential in a fluid in order to obtain the velocity field. This can be done for flow around a cylinder to ... 0answers 79 views ### The Optics of the Vortex (in Water): why there is a bright ring also in reversed flow? This question is closely related to this one; The optics of vortex (in water): why there is a bright ring? In this case "physics girl" gives somehow an plausible explanation, and it's only debatable ... 8answers 5k views ### Turbulent spacetime from Einstein equation? It is well known that the fluid equations (Euler equation, Navier-Stokes, ...), being non-linear, may have highly turbulent solutions. Of course, these solutions are non-analytical. The laminar flow ... 0answers 29 views ### Modeling Fluid Flow I could really use some assistance. How would I go about trying to use Maple in order to model flow of a fluid through objects? For a rough example, such as entering an enterance of a maze and exiting ... 1answer 113 views ### Physical intuition on vortex sound generation Whenever a fluid has a nonzero vorticity, it looses some of its energy in a form of sound wave. Formally is this mechanism described by Lighthill's equation or some related model (like e.g. Curle's ... 1answer 49 views ### How Does Rotational and Turbulent Motion Contribute to the Pressures of Dynamical Systems? Rotational and turbulent motion can deepen a gravity well in a galaxy or galaxy cluster. In an analysis of the mass components of a large body, this would appear to be one of the components. Does it ... 0answers 53 views ### Dependence of the magneto-rotational instability (MRI) on thermal relaxation? The MRI is the most efficient driver of turbulence in accretion discs (as measured by the effective scalar stress). The magnetic field, being properly coupled to the gas (weak coupling), connects the ... 3answers 598 views ### Why don't surfboards fly out the back of a utility truck when driving on the highway? I have never had it happen myself and every time I throw my boards (shortboards not malibus) in the back of someone's ute, with no cover on the tray, they always assure me they'll be alright( the ... 1answer 52 views ### Why do you feel air moving past you when you walk? I know that when you walk through the air you form a wake vortex and turbulent air behind and the vortex grows the faster you walk. When I walk past people I almost feel wind that's behind them. So ... 1answer 85 views ### How to model the mixing of two fluids? In the context of a research project of mine, I am faced with the difficult task of modeling the mixing of two fluids in a container. I would like to achieve the following: Given a container (... 1answer 135 views ### How are the turbulent spectra determined in relativistic turbulence? In a non-relativistic compressible fluid, the turbulent energy spectra are well-understood and appear to follow the Kolmogorov hypothesis. It would also appear that relativistic turbulence also ... 2answers 130 views ### What do the differences between spatial and temporal spectra imply about the structure of turbulence? In the study of turbulence (theoretically, computationally and experimentally), we often appeal to Taylor's Hypothesis, which (very loosely) summarized means taking measurements at one point in space ... 1answer 331 views ### Turbulent and smooth flow of water from a tap When water flows normally from a tap, we can say it is turbulent ( Pic 1 ). But when we attach a piece of cloth to the opening of tap, water flow becomes smooth ( Pic 2 ). We can say that by touching ... 1answer 141 views ### Velocity of water from tap to fill a cracked bucket to brim Let us consider a real life situation. The bucket in figure below (drawn using MS PAINT) has an irregular crack of essentially small area. And I decide to open a tap above it and start filling it ... 0answers 22 views ### Limitation of Rytov approximation for turbulence I have been working through the textbook "Laser Beam Propagation through Random Media" by Andrews and Phillips and have arrived at an interesting dilemma. For a second-order perturbation in the Born ... 2answers 158 views ### Why is the Reynolds number “the way it is?” Why is its order the way it is? Why is the Reynolds number “the way it is?” Why is its order the way it is? I'm not sure if this is an appropriate question for this context, but I would like more intuition on this matter and so I'... 3answers 1k views ### Laminar vs Turbulent flow separataion (Left is a laminar separation, Right is a turbulent separation) I have been having a bit of trouble understanding this concept. How come the laminar separation involves a much larger wake than the ... 0answers 47 views ### Any applications of kinetic physics on cosmological scales? On galaxy cluster scales, one is usually forced to use approximate theories such as hydrodynamics or magnetohydrodynamics for modelling cosmological phenomena. I wanted to ask if kinetic theory is ... 1answer 59 views ### Reynolds Average Navier Stokes equations and turbulence scale To obtain the time average of an unsteady term like$\frac{\partial u_{i}}{\partial t}by definition we perform the following: \begin{align} \overline{\frac{\partial u_{i}}{\partial t}} &= \... 1answer 234 views ### What is the cause for turbulence? The transition from laminar flow to turbulent flow is usually told interms of Reynolds numbers. The Reynolds number isRe=UL/\nu$where$U$is the speed,$L$is dimensional length and$\nu$is the ... 3answers 177 views ### Why are vehicles not pitted like golf balls? I have read that non-laminar flow reduces drag on blunt bodies. Given that, why is pitting not used on motor vehicles? 2answers 456 views ### The optics of vortex (in water): why there is a bright ring? This picture is from this YouTube video from "Physics Girl", which shows how you can generate vortices in a swimming pool by using a plate: And there she explains the creation of the shaded circle ... 1answer 243 views ### Can a vacuum make a turbulent flow laminar? When a vacuum is generated next to a turbulence, does the flow towards the vacuum become laminar? Imagine a vacuum cleaner tube is put next to turbulent air movement, does the "suction" change the ... 0answers 43 views ###$L^p\$-weighted enstrophy calculations

Mathematician here, only somewhat familiar with physics, but finding myself involved in a research project on fluid dynamics. I'm studying a 3D simulation of turbulent fluid flow, and we are currently ...