Boundary layer Definition and 61 Threads

In physics and fluid mechanics, a boundary layer is the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant. The liquid or gas in the boundary layer tends to cling to the surface.
The boundary layer around a human is heated by the human, so it is warmer than the surrounding air. A breeze disrupts the boundary layer, and hair and clothing protect it, making the human feel cooler or warmer. On an aircraft wing, the boundary layer is the part of the flow close to the wing, where viscous forces distort the surrounding non-viscous flow. In the Earth's atmosphere, the atmospheric boundary layer is the air layer (~ 1 km) near the ground. It is affected by the surface; day-night heat flows caused by the sun heating the ground, moisture, or momentum transfer to or from the surface.

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  1. A

    Tripping the boundary layer why?

    Tripping the boundary layer...why?? I don't understand why we have these "vortex generators" to trip the boundary layer into becoming turbulent...i've seen this a lot on F1 cars. On a regular car you can trip the boundary layer in front of your windshield...does the boundary layer somehow...
  2. V

    Boundary Layer displacement thickness

    Hey guys, The streamlines just outside a boundary layer are pushed away from the wall by the displacement thickness \delta* and I understand that; \delta*=\int^{\infty}_{0}(1-\frac{u}{U})dy Now this is for flow over a plate with length x=4m. At x=0 is the leading edge and at x=4...
  3. M

    Turbulent Boundary layer thickness on a flat plate

    I am really confused. Would you please tell me what the turbulent boundary layer thickness is on a flat plate? There is a well-known Schlichting formula in the previous editions of his book “boundary layer theory”, which is: \delta = 0.37 X Re^{-0.2} But actually I could not find this...
  4. A

    My essay on the atmospheric boundary layer

    3 pages double spaced. Can someone please comment on it before Sunday? That would be nice. Thanks! the file located at http://students.washington.edu/achen89/3_boundarylayer.doc . Please feel free to e-mail corrections to hemaalpha@gmail.com Human civilization (and biological phenomena) has...
  5. K

    How do different hull treatments affect water flow and boat speed?

    Hi Sailing 30 yrs ago we used to wax and polish hulls to maintain a protective and as gloss a surface as possible. However some say that anything that beads water such as wax causes more drag than a smooth surface that water will sheet over. Note Racing rule 53 " SKIN FRICTION A boat...
  6. A

    Stability for turbulent boundary layer

    concerning fluid flow past a body, i know that if the boundary layer is laminar then the flow becomes unstable when the Reynold's number of the flow is greater than the critical Reynold's number. is this also true when the boundary layer is turbulent? tia
  7. P

    How Does Film Thickness Affect Mass Flow Rate in Laminar Liquid Boundary Layers?

    Here is the problem: (From sabersky, problem 8.9) Vapor condenses on a vertical surface to form a liquid film. The film moves under gravity and forms a laminar liquid boundary layer. Derive an expression for the mass flow rate dm/dt as a function of the local film thickness \delta. Neglect...
  8. A

    How Does Object Shape Influence Water Flow Patterns?

    I have a physics project and i chose the topic of fluid dynamic (i don't know of it is really fluid dynamic but i think that is close enough). My level is only a high school student for information, in order to avoid any over complicating explenation. The concept is simple: first pour a...
  9. P

    Magnus force and boundary layer equations

    First of all I am trying to find a "derivation??" for the Magnus force that affects rotating cylinders and spheres passing moving through air. By derivation, if it is not correct, I mean a proof, something showing how the function was created. I have found the magnus force quite easily by...
  10. W

    How does turbulence affect the boundary layer and create drag on swimsuits?

    hi, I'm just currently doing some research on swimsuits and how they work. i have found that 1 type of swimsuit makes water "stick" to the suit longer so the water doesn't separate and cause drag. i notice this is very similar to how golf balls work with the dimples making the air stick longer...
  11. Clausius2

    Electromagnetic boundary layer.

    I want to comment with you this imaginary problem. I have not formulated it yet. But I would want your qualitative opinion about this. It is not anything new or revolutionary, because electromagnetic control of boundary layers have been proved yet. But I would want to understood mathematically...
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