What is Laminar flow: Definition and 47 Discussions

In fluid dynamics, laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids. In laminar flow, the motion of the particles of the fluid is very orderly with particles close to a solid surface moving in straight lines parallel to that surface.
Laminar flow is a flow regime characterized by high momentum diffusion and low momentum convection.
When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity and viscosity of the fluid: laminar flow or turbulent flow. Laminar flow occurs at lower velocities, below a threshold at which the flow becomes turbulent. The velocity is determined by a dimensionless parameter characterizing the flow called the Reynolds number, which also depends on the viscosity and density of the fluid and dimensions of the channel. Turbulent flow is a less orderly flow regime that is characterized by eddies or small packets of fluid particles, which result in lateral mixing. In non-scientific terms, laminar flow is smooth, while turbulent flow is rough.

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  1. G

    Misc. DIY laminar flow hood filtration question

    hello everyone, i am building a laminar flow hood for plant tissue culturing and have a question regarding flow and filters. my issue is i want a decent size of work space, that isn't all cramped up. as it stands, a 12"x24" hepa or merv 17 rated filter is pretty expensive, but two 12"x14"...
  2. axelb

    I How is the Reynolds number derived (is my derivation wrong)?

    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**...
  3. S

    Possible to create laminar flow in fast moving air?

    Is it possible to create (nearly?) laminar flow in a tube with rectangular C.S. , around 1 cm X 5 cm , with air moving at around 100 to 150 m/sec? Turbulence will likely set in sooner or later, but can the laminar flow be made to last over say 20 cm?
  4. Anachronist

    B Beam of air: Extending the range of a fan

    If one Googles for "laminar flow nozzle", one finds many interesting tutorials on creating a nozzle for a laminar water jet; a stream of water that remains coherent over a long distance without breaking up. These typically consist of a large-diameter tube with regions inside (like sponges and...
  5. L

    A fun, engaging and visual way of showing laminar flow for young kids

    I have been tasked by my fluid dynamics professor to create a 3 minute video showing and explaining laminar flow vs turbulant flow. It must be engaging and explain the concepts simply enough with no math. I will be re-writting this definition below to suite the needs ""Laminar flow occurs...
  6. curiously new

    I Laminar-turbulent transition and Reynolds number

    Hi all! This is my first post here, so hopefully I am not in violation of any rules or etiquette. I'm looking to derive an equation for Reynolds number as function of pressure for a pinhole leak in a pressurized gas line. The line is regular air and is pressurized to 1 atmosphere and is leaking...
  7. B

    I Analytical Open Channel Rectangular Fluid Flow

    Hi All, I'm looking for an analytical solution to the open channel rectangular fluid flow profile. The flow is bounded by three walls but the top is open to atmosphere. Assume steady state flow that is parallel and incompressible.I've already found information involving a rectangular flow...
  8. P

    Can Reynolds Number < 70 Cause Turbulence in Elbow Fittings?

    Hello people, If we are working on the flow with reynolds number less than 70 as we all know the flow will be laminar in pipe. Now if the flow continues to flow through elbow fittings like 90 degrees, will we get any turbulence because of the elbow bend ? How to deal with this problem in ansys...
  9. G

    Beyond Viscous Drag, Cavitation, Laminar Flow, & Reynolds

    When using Computational Fluid Dynamic (CFD) modeling you are able to see incredible complexity in water energy transfer. The Thermodynamic energy transfer occurs at much higher velocity so it does not apply in most of the cases I am looking at. What are the other parasitic energy transfers that...
  10. G

    Laminar flow in a tube, heat transfer coefficient-sanity check

    Hi there, Hopefully this is a very easy question and you all can just confirm this for me. When calculating heat transfer into a fluid from a heated tube, is it correct to say that the heat transfer coefficient is *not* dependent on the tube diameter? So, if we solve for T_{out}, we get...
  11. H

    Laminar and turbulent flow on dripping blood

    Can laminar and turbulent flow be used to explain dripping blood? Be it blood dripping from a weapon/ impacting on an uneven surface?
  12. M

    Need some intuition for laminar flow in different geometries

    Hi guys, I've been working through some notes on Transport Phenomena by Bird and I've basically been just developing velocity and shear stress profiles for various (simple) models by a differential momentum balance and I'm trying to understand why a certain result happens. When looking at...
  13. S

    I Laminar and steady flow(Distinguish)

    While deriving Poiseuille's law (the relation between flow rate and pressure gradient for fluid flow in a rigid cylindrical tube under a pressure gradient) , we make an assumption that flow is both laminar and steady.Why we need the flow to be laminar. Is it not enough to consider only steady...
  14. jdawg

    Fluid Mechanics: 2D Laminar Flow

    Homework Statement A reasonable approximation for the two-dimensional incompressible laminar boundary layer on the flat surface in Fig. P4.17 is u ≈ U(2*(y/δ) - 6*(y3/δ4) + y4/δ4) δ = Cx1/2 where C is a constant y ≤ δ Homework EquationsThe Attempt at a Solution Incompressible so...
  15. W

    Determining Δhloss for Turbulent Flow: Is it the Same?

    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...
  16. Mohamed_Wael

    Pressure drop doesn't depend on pipe material (laminar flow)

    why does the pressure drop equation derived for the laminar flow has no parameter to indicate the surface roughness of the material of the pipe,unlike the turbulent flow !
  17. Qais Hassan

    Confused about Reynolds Number- Fluid Mechanics

    Hi, I am working on the laminar flow and during my calculation at the outlet of my nozzle my Re was even greater than 120,000 however my other calculations seemed legit to me. And someone told me that I am calculating the Reynolds number of an open channel and for that flow can remain in laminar...
  18. F

    Solving Pipe Flow: Understanding Why $\tau =\mu(-dV/dR)$

    Homework Statement why the shaer stress ( tau) formula is given by μ(dv/ dy ) = μ(-dV / dR) , why there is a negative sign there ? Homework EquationsThe Attempt at a Solution
  19. H

    Why Does the Laminar Flow Equation Use Different Coefficients?

    Homework Statement as we all know , D=4R , D=hydraulic diameter , in the equation of P= (8μLV_avg) / (R^2) , i would get (128μLV_avg)/ (D^2) , am i right ? why the author gave (32μLV_avg)/ (D^2) ? Homework EquationsThe Attempt at a Solution
  20. MexChemE

    How do I model mass transfer in a tubular reactor?

    Good evening, PF! I am supposed to model the following system. I will be using the same notation as in BSL. Fluid A enters the reaction zone at z = 0 at a concentration CA0. A reacts to form B in the first order reaction A → B at a rate of R_A = k_1''' C_A. We assume the whole mixture to be...
  21. E

    How Does Tube Diameter Affect Reynolds Number in Gravity-Driven Laminar Flow?

    < Mentor Note -- please remember to use the Homework Help Template when posting schoolwork questions > Consider the fully developed laminar flow due to gravity of water in a vertical circular tube. Assume atmospheric pressure at inlet and outlet. Show that the relationship between diameter and...
  22. Dong Aleta

    Approximation of friction factor for Laminar Flow

    Hi! I read from Perry Green's ChE Handbook that the friction factor for Re ≤ 2,100 can be approximated by ƒ = 16/Re. But there was this question that I encountered (though I don't know the source) and according to it, ƒ = 64/Re for laminar flow. Can someone clarify which is which? Thank you!
  23. V

    Using Laminar Flow to measure Thermal Conductivity

    So, there's a project I'm working on (no, it's not school related), where I'm trying to figure out how to measure thermal conductivity of a material using laminar flow. The idea is to integrate this into a larger system, and it's a measurement I'd like to take in the process. I know the...
  24. throneoo

    Laminar Flow : shear force on walls

    Homework Statement a viscous fluid with viscosity η flows through a circular vessel of length L and radius R under a pressure difference of P. Assuming the flow is laminar, calculate: a)the force on the walls of the vessel. b)the net force on the vessel. Homework Equations Hagen-Poiseuille...
  25. arthurchen

    Laminar flow exits an inclined tube

    I am working on a problem in which viscous flow comes out from an inclined tube, forming some kind of a fountain. In the tube the fluid is Newtonian and the flow can be treated as Poiseuille flow. I want to study the movement of the fluid after it leaves the tube. Can someone point me about the...
  26. R

    Laminar flow in a pipe (Poiseuille flow)

    Homework Statement I am trying to derive Poiseuille's equation using an infinitesimal volume element of the pipe in cylindrical coordinates as seen below. I am using x for the flow direction, u for the velocity in the flow direction, and μ for the viscosity constant...
  27. A

    Wha is difference between laminar flow and streamlined flow.

    I have a doubt about the difference between laminar and streamlined flow. What is difference between those to flows of the liquid. Waht is the reason for the top layer of a liquid to have maximum speed in laminar flow. When does laminar and streamlined flows occur.
  28. P

    Laminar Flow: Finding Viscosity of Oil

    Homework Statement Finding the viscosity of oil... Homework Equations η = b/(6∏r) Fr = -bv The Attempt at a Solution The question only gives a radius, mass, density of oil, and terminal velocity. Is it possible to get the viscosity with the given information?
  29. M

    Laminar flow fixed parallel plates

    http://books.google.com/books?id=p7WsoU-CfPkC&pg=PA224&lpg=PA224&dq=6.132+fluid+mechanics&source=bl&ots=7q6rcCGewf&sig=EvcrqTJCxqLSPbKrkiztkPS4I6Q&hl=en&sa=X&ei=6vo6UYusIenFyAHHt4GYAQ&ved=0CDoQ6AEwAw#v=onepage&q=6.132%20fluid%20mechanics&f=false Can someone please tell me how they arrived at...
  30. W

    How the Reynold number of 4000 consist of laminar flow?

    I was asked a question that the Reynold number of a fluid is greater than 4000 but flow Is Still laminar. How is it possible? can anyone explain?.
  31. T

    COMSOL: Problem about optimization applied to a laminar flow

    Hi all,i'm new here and i really hope that you could help me with this problem that is blocking the progression of my graduation thesis. I'm working on a 3D stationary simulation of brachiocefalic artery; I'm using laminar flow physics with a known velocity in inlet and a normal stress in...
  32. V

    Help with Drag Calculation for Laminar Flow Model

    Hi there, I am working an a stationary, laminar flow model and would like to calculate the drag of that model. Now the Comsol forum guys suggest to use the operator reacf(u). It is also used in the "Flow over a circular cylinder" tutorial. Does anyone know where to get it from or how to use...
  33. S

    Why do streamlines converge when water flows down?

    1)Can two streamlines(line of flow) converge to a single one ? 2) When water flows from the tap, as it flows down the horizontal area of cross-section decreases...An argument using the Equation of Continuity is given...but I have two doubts regarding those i) Is water in freefall Laminar...
  34. F

    How Do Swimsuits Influence Laminar Flow and Reduce Drag?

    Hi I’m student at a french university, I have to present a project about swimsuit and I must carry out experiments. I’ve decided to work on the buoyancy of swimsuits, the flow around it and drag. To measure drag, I think I’ll drop a heavy ball wrapped in swimsuit material in the water and...
  35. B

    Need Help Understanding Turblance / Laminar Flow

    Hi guys, first post and I hope I got the right forum. I have been doing some reading on fluid dynamics and there are a couple things I can't figure out. 1) When you light a candle or something and the smoke rises. It starts of nice and smooth, but then turns all turbulent after a little bit...
  36. X

    Fluid Mechanics: Inviscid flow v.s. Laminar flow

    Hey guys, I am kind of confused here but can you guys define for me inviscid flow and laminar flow? In my understanding, inviscid flow is when viscous effect is very weak and laminar flow is when reynolds number is in general, less than 2300. In that effect, does that mean that viscosity for...
  37. B

    Fluid with laminar flow going through a constriction in a pipe has low

    Hi What is the fundamental reason why a fluid with laminar flow going through a constriction in a pipe has lower pressure? Pressure is defined as force per unit area so the fluid particles must be hitting the pipe wall in the constriction with less force. Beetroot
  38. J

    What is the profile of the second fluid in laminar flow with two fluids?

    Hi I am working in an application where we pump a fluid in a water -filled tube, where the second fluid has a viscosity of 3-4 times the viscosity of water. We have laminar flow (Re around 20). If the fluids were 100% compatible (e.g. colored water vs clear water) I have determined that...
  39. A

    What is an Eddy to Turbulent and Laminar Flow

    I understand that there can be turbulent flow and laminar flow. However, there is a term 'eddies/eddy' related to this which is not explained in my textbooks. What is an 'eddies/eddy'? :confused: Thanks in advance.
  40. G

    Laminar Flow through a Tringular Duct

    I'm currently a freshman chemical engineer at Penn State and I've gotten so frustrated at fluid transport that I have resorted to online forums for one last desperate attempt to try and figure out what exactly is going on. This question is part of a long agonizing 2 week homework assignment and...
  41. D

    What is the solution for the laminar flow problem?

    Problem: Two horses pull a barge from rest in a canal filled with a viscous fluid that provides laminar resistance (FR = –kv). The two horses walk on each side of the canal so that their net force is applied exactly forward. The barge has a mass of 3000 kg and the donkeys pull forward with a...
  42. D

    How Does Laminar Flow Resistance Affect Barge Movement in a Canal?

    Problem: Two horses pull a barge from rest in a canal filled with a viscous fluid that provides laminar resistance (FR = –kv). The two horses walk on each side of the canal so that their net force is applied exactly forward. The barge has a mass of 3000 kg and the donkeys pull forward with a...
  43. I

    Shear Stress due to Laminar flow

    Homework Statement Oil of Density 888kg/m^3 and viscosity 0.8Pa*s is flowing in a horizontal pipe of diameter 0.15m. The local flow velocity at the centerline is 10m/s. find the shear stress exerted by the oil on the wall of the pipe. Homework Equations tau = -eta*(dv/dy) The...
  44. T

    How is the force in the Y direction developed in a simple laminar flow?

    RE: non-compressible, laminar flow, Newtonain fluid. Viscosity is often defined by looking at a fluid between two plates with the upper plate moving at a small velocity relative to the lower plate. The plate moves in the x direction and a velocity gradiant is created. Viscosity is then...
  45. M

    "fully developed laminar flow" and fully developed turbulent flow"?

    Hi all, can you tell me what different between "fully developed laminar flow" and fully developed turbulent flow"? :cry: