Talk:Turbulator

note

Kind of a random find, but I was reading the August 1989 issue of Popular Science (found it on my dad's shelf) about a new tri-hull ship design, and came to this page after learning about how its propeller mount used "turbulators" to smooth water flow into the propeller. Those turbulators seem to take the form of small spikes protruding from a surface. Any idea whether it's relevant to this article? Cctoide 01:22, 2 October 2007 (UTC)

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Airfoil turbulators==

When air flows over the wing (an airfoil) of an aircraft, there is a layer of air called the boundary layer between the wing's surface and where the air is undisturbed. Depending on the profile of the wing, the air will often flow smoothly in a thin boundary layer across much of the wing's surface. The boundary layer will be laminar near the leading edge and will become turbulent a certain distance from the leading edge depending on surface roughness and Reynolds Number (speed). However, there comes a point, the separation point, in which the boundary layer breaks away from the surface of the wing due to the magnitude of the positive pressure gradient. Beneath the separated layer, bubbles of stagnant air form, creating additional drag because of the lower pressure in the wake behind the separation point.

These bubbles can be reduced or even eliminated by shaping the airfoil to move the separation point downstream or by adding a device, a turbulator that trips the boundary layer into turbulence. The turbulent boundary layer contains more energy, so will delay separation until a greater magnitude of negative pressure gradient is reached, effectively moving the separation point further aft on the airfoil and possibly eliminating separation completely. A consequence of the turbulent boundary layer is increased skin friction relative to a laminar boundary layer, but this is very small compared to the increase in drag associated with separation.

The DG 300 glider used small holes in the wing surface to blow air into the boundary layer, but there is a risk that these holes will become blocked by polish, dirt and moisture.

For the aircraft with low Reynolds numbers (i.e. where minimizing turbulence and drag is a major concern) such as gliders, the small increase in drag from the turbulator at higher speeds is minor compared with the larger improvements at best glide speed, at which the glider can fly the farthest for a given height.

-- Jytdog (talk) 16:16, 8 October 2018 (UTC)

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In pipe flow==

The heat transfer coefficient for liquids and gases flowing through pipes in heat exchangers tends to be limited due to a fluid boundary layer close to the pipe wall that is stagnant or moves at slow speed, thus acting as an insulating layer. Such heat exchangers are, for example, in domestic central heating systems. This boundary layer can be broken or reduced in thickness if turbulators are placed in the pipe, which create a turbulent flow that reduces the boundary-layer thickness and thereby increase the heat-transfer coefficient. This increase in heat transfer coefficient comes at the price of increased pressure drop through the pipe as well as increased manufacturing cost and complexity.

Examples of turbulators for pipe flow are:

• Twisted-tape turbulators, a twisted ribbon that forces the fluid to move in a helicoidal path rather than in a straight line;
• Brock turbulators, a zig-zag folded ribbon;
• Wire turbulators, typically an open structure of looped and entangled wires that extends over the entire pipe length.

Turbulators can also be put to use in certain internal combustion engines - particularly, a ramjet engine. A simple porous wire mesh placed in the diffuser of the ramjet can increase turbulence in the flow entering the combustion chamber, which aids in fuel mixing. -- Jytdog (talk) 16:17, 8 October 2018 (UTC)