What is Turbulent flow: Definition and 51 Discussions
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers.Turbulence is commonly observed in everyday phenomena such as surf, fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent. Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. This increases the energy needed to pump fluid through a pipe.
The onset of turbulence can be predicted by the dimensionless Reynolds number, the ratio of kinetic energy to viscous damping in a fluid flow. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence create a very complex phenomenon. Richard Feynman has described turbulence as the most important unsolved problem in classical physics.
Hello everybody,
I am thinking of the following problem:
A sphere a radius r is in a much larger container of radius R.
In this container, a fluid continuously flows with turbulent conditions from bottom to top.
I would like to approximate the force pushing the sphere up.
Some calculations I...
Hi everyone,
(this is my first post so be gentle)
I am currently getting my masters is mechanical engineering, was admitted to aero Ph.D. programs as Vtech, MSU, and Cinci last year but decided to get masters locally and apply to "better" schools (UofM) for next cycle with a better resume and...
I'm a HS student so please dumb it down. I'm looking into the Reynolds number of a sphere sinking in a fluid, and I want to determine whether my results meet creeping flow or not Re<<1, here's what I got. **sorry if I misused the prefix, I'm not sure whether it's highschool or undergraduate**...
I want to start with two scenarios and both contains a blower and a tunnel fitting for the blower and both have almost the same diameter. The tunnel has s little higher so that the blower can be fitted inside. In the first scenario, the blower is fitted at the end of the tunnel i.e. the flow...
Hello,i am just a college student who has a little confusion on when to consider both laminar and turbulent flow -say over a flat plate,should i assume turbulent flow all over the plate and use the related equations(nusselt number) or use the laminar and turbulent equation(Nusslet number) but if...
I would like to give a geometric interpretation to turbulence. Let's take into consideration for example a Poiseuille flow. The velocity profile resembles a parabolic bullet. As the particles are pushed by other layers of particles, then it must be that in addition to their translation, they...
Hi,
I was recently attempting a problem about the height of buffer regions and viscous sublayer.
Question:
A fluid flows through a smooth pipe of diameter 150 mm with flow rate, density and kinematic viscosity of 0.180 m^{3} s^{-1} and a density 700 kg and 0.40 \times 10^{−6} 𝑚^2...
Hi,
I was recently learning about turbulent boundary layers and came across the 'Prandtl mixing length'. I am struggling to understand what the concept is and what its purpose is. I would appreciate any help or guidance of where I can look to gain a better understanding.
The information I...
I am confuse understanding between unsteady and turbulent flow. If I look the fluid simulation in Youtube, they both look the same. What is the difference between them? Please explain for a beginner.
hi guys
I'm really struggling to get the expression for average speed in turbulent flow
The book explains absolutely nothing about how the integration is carried out, in addition to the fact that the logarithmic term becomes undefined when r = R what I did was carry out the integration up to...
Mathematical proofs that many turbulent flows can be predicted at least in a stochastic sense. Under the right conditions, it turns out that the flow lines and vortices pretty much follow a fractal law.
Popular version...
Suppose a fluid passes from having laminar flow, to having a turbulent flow (like when passing after an object). How do fluid speed and fluid density change after that?
According to wikipedia "The onset of turbulence can be predicted by the Reynolds number, which is the ratio of inertial forces to viscous forces within a fluid which is subject to relative internal movement due to different fluid velocities, in what is known as a boundary layer in the case of a...
Is it true that the laminar to turbulent flow transition has been finally solved? From what I've read, it seems to be well described by the Directed Percolation Model. I can hardly believe it since I haven't seen the news in the press (from my point of view, it's a long standing unsolved issue...
Hello PF,
I am new to the science of turbulence and fluids but recently I have been working with my professor on 2D steady state turbulence and I was looking for a way to model and simulate this scenario:
I have a flow affected by a spatially varying magnetic field and having a current pass by...
I remember from my physics classes that the wave functions for the hydrogen atoms or an electron in a box showed typical linear wave behaviour. However, when you have a large system's wave function, say for example the universe, will it then show different spatial-dynamic structure? What comes...
Hello,
I used the Darcy Friction Factor from the Moody Diagram along with the Reynolds number to find energy losses inside the cold air tubing of our vortex system. My calculations showed that I should decrease transitions, length, diameter, and velocity. I am mainly concerned with the figuring...
I simulated an incompressible turbulent flow across a tube. I managed to solve it using OpenFoam and the results seem to be right. However, I noted some vacuum pressure after the sudden expansion but can't figure out why the pressure decreases and then increases again. According to Bernoulli's...
In the gas industry engineers often have to purge gas pipes. For example, if repair work must be done on a gas line the fuel gas in the system must be removed before work can be done safely.
The Institute of Gas Engineers and Managers (IGEM) publication IGE/UP/1 stresses the need to achieve a...
Homework Statement
We know for Laminar flow in which Re<2000 that
##Δhloss=K*\frac{u^{2}} {2g}##
What about if Re>10000 and is turbulent?
Homework Equations
##Δhloss=K*\frac{u^{2}} {2g}##
where ##K=\frac{f*4L} {D}##
The Attempt at a Solution
How would Δhloss look like for turbulent...
"For a particular flow rate, the pressure drop due to the downward flow of the fluid is
balanced by the pressure gain due to gravity—that is, at this flow rate, the static
pressure in the pipe is independent of the distance along the pipe."
Book says this. Can you explain how the pressure...
Homework Statement
Hello everyone, I am having a problem whether or not a turbulence at a specific location (let's say A) is isotropic or not.
I have calculated the two root mean square values of velocity fluctuations measured at the point A in a fully developed turbulent pipe flow.
the first...
Please could someone verify this statement as I understand things:
If an object has a low reynolds number (or the fluid is very viscous) then it is dominated by viscous forces and inertia plays no role. The object is in a laminar flow regime.
That last part, is it correct? What I'm asking is...
I have an assignment involving a duct vent and turbulent flow.
Flow enters a duct vent of a certain cross-section, it then reaches another section with a smaller area, at the beginning of which there is a horizontal plate that is radiating heat.
It's a 2D problem.
Fluid is Air, inflow T=20C...
Quick facts: Age (19) / Mech. Eng. Sophomore / Automotive & Physics Lover
In an attempt to design and construct a new less restrictive engine intake system I've run into a number of questions I am not yet able to answer.
Main Goal: To produce a new intake system and associated plumbing...
I was hoping someone could give me an explanation as to why resistance of a fluid moving through a tube changes from being determined by viscosity in conditions of laminar flow to being determined by density in conditions of turbulent flow.
Thanks in advance.
Homework Statement
Consider the flow of air over an aerofoil.
The critical Reynolds number marking the transition from laminar to turbulent flow is 6 x 10^5, the dynamic viscosity is 2.0 x 10^-5 Ns/m^2, the density of air is 1.100 kg/m^3 and the aircraft velocity is 180 m/s.
What is the length...
So I understand that Reynolds number is the ratio of intertial forces to viscous forces but how exactly does this relate to flow? Why is it that when viscous forces dominate one gets a laminar flow? How to conceptualize?
If we're considering fluid flow over a plate and found that at one location the flow is turbulent. Is it always the case that there is also a transition and laminar region before that turbulent region on the plate?
Hello
I am trying to validate my model by comparing a simple axisymetric 2D
impacting flow of air on a surface.
The geometry is simple: a cylindrical (diameter d=26.5e-3[m]) jet of air
(debit Speed Ud=13.46[m/s]) is impacting a surface at distance H=0.2833[m].
Flow temp is Tj=20°C Wall...
Homework Statement
This time I'd like someone to verify that my rationale behind the correct answer is accurate...
Which of the following will decrease the chance of turbulent blood flow in a vein?
A. Narrowing the vein.
B. Thinning the blood without changing its density.
C...
i've been given this question by my lecturer at university and I am struggling with where to start with it to be honest. it feels like i don't have enough information. please can someone help?
For turbulent flow, the velocity profile inside a duct and a pipe of diameters Dd and Dp and
both...
i've been given this question by my lecturer at university and I am struggling with where to start with it to be honest. it feels like i don't have enough information. please can someone help?
For turbulent flow, the velocity profile inside a duct and a pipe of diameters Dd and Dp and
both...
i've been given this question by my lecturer at university and I am struggling with where to start with it to be honest. it feels like i don't have enough information. please can someone help?
For turbulent flow, the velocity profile inside a duct and a pipe of diameters Dd and Dp and
both...
Hi
I'm a mechanical engineering student who has been set a question by my fluid mechanics lecturer. I need to plot the velocity flow profile of water flowing in a pipe. The information given in the question is
diameter = 0.5m
Re = 10^5
I know that the seventh power law is used to find...
Homework Statement
A projectile of mass 0.1 kg traveling horizontally through the air with speed v(t) experiences
a drag force DT (t) whose magnitude is given by:
D (t ) 0.001 [v (t )] 2
At one instant, the projectile’s speed is measured to be 100 m/s. Calculate the speed of the...
To preface, I know about ~nothing about aerodynamics, but have been reading through wiki pages half the morning, but am still not quite sure how to answer a question.
Basically my question is concerning the turbulent flow that happens behind an aircraft, maybe just focusing on the wing for now...
Homework Statement
Consider a metal sphere of radius r, drag coefficient C, density p_s falling in a fluid p and viscosity n.
Find the acceleration:
I found this to be g - p/p_s * g - (3C/(8*p_s*r))*v^2. Others were in agreeal with this so take it as given.
***Show that your result has...
Hi Guys.
I have an absurd problem and no idea to solve it. Please could you help me?
\frac{u}{\hat u} = \left [ \frac{y}{R} \right ]^{1/n} = \left [1- \frac{r}{R} \right ]^{1/n}
Suppose the turbulent flow velocity distribution in a pipe of Radius R can be described by the equation...
Hi, guys, i tried to read the definitions of laminar and turbulent flowon some of the website, but had difficult time understanding them. I am wondering if you guys can explain the above terms in more plain words?
effect on Flow and pressure measuring due to turbulent flow of air
Hi,
I want to measure the air flow rate using a device which will basically measure the velocity of air and converts that in terms of flow rate reading. For creating flow of air i have used vacuum pumps which is connected by...
http://www.sciencedaily.com/releases/2008/11/081121101003.htm
Quote.
Until now, scientists assumed that a turbulent flow traveling with a constant speed will always remain turbulent. However, scientists from Göttingen and Delft have now found evidence that points to the contrary. "Our...
I want to build a flow hood for biology projects but a laminar flow HEPA costs more than I have in my bank account. There are cheaper HEPA filters out there but they don't produce laminar flow. The flow only needs to be laminar so eddies don't bring contaminates off dirty objects under the flow...
Do the head losses on turbulent flow are always greater then on a laminar flow? Why does it seem from the Moody chart that the friction factor becomes smaller when the flow becomes more turbulent?
I have an open question for anyone. My science/math modeling club is attempting to develop a predictive model for predicting the taphonomy of dinosaur bones exposed in a stream bank.
We have designed and built a 5ft X 5ft stream table with two curves. The idea id to put a large...
One of the factors that can produce a winning F1 car is the understanding of turbulent flow, the people that design these cars spend millions on wind tunnels, simply because turbulent flow has not yielded to mathematics, my way of thinking is ,that it is essential to understand turbulent flow...
How do u calc pressure at each end of pipe if u know its turbulent and u don't know the length.
Just got viscosity, density, temp diff at one end, D.
Cheers.
Hey guys how do you know when will a flow be turbulent or laminar?i came across a question asking what's the flow of the wind on the sail of a sailboat.i thought that since there is the sail to block the wind when the boat is surfing against the wind, the flow will be turbulent but the ans is...