Boundary layer concepts..

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:You present an interesting conundrum: You seem to be asking to know the concepts resulting from the efforts of the truly GREATS in the field - Bernoulli, Froude, Prandtl, Euller and others - and yet, if you had the knowledge to be able to understand the responses, your question would not exist.

One must suspect a more complete question would result in a more meaningful answer. If you intend to ask about the fields of study which address these concepts, then be aware they are Thermodynamics and Hydrodynamics. These are complex and highly technical fields, but if you have the technical foundation and really want to get into them try starting with two books. The first is a textbook by Schlichting titled "Boundary Layer Theory" which was published by Springer some time back, maybe about 2001. You should find it very thorough. There are many good references on thermodynamics and flow. Try perhaps Laminar Flow Analysis by Rogers. It addresses thermodynamics in boundary to some detail.

If in reality you actually want an answer to the question asked, then I have no truly good response. The "application of thermal and velocity boundary layer concepts" is truly ubiquitous. Look around you and you see fluids at every turn - the atmosphere, the oceans, rivers, lakes, everywhere. The human body is, what, maybe three-quarters water. Consideration of the dynamics of fluids and heat apply in all these domains and many others. They include animal physiology, botany, medical engineering, medicine, combustion engineering, astronomy, aerodynamics, ocean engineering, nuclear power, micro-electro-mechanical systems (MEMS) development, meteorology, metrology, geology, hydrology, etc., etc. Heat and flow boundary layer concepts are pertinent in all these areas of consideration and many others.

The concept of boundary layer applies to constrained flow, as that in a pipe or other container (or perhaps a capillary in vascular systems.) The "boundary" is the part of the flow next to a "wall" of the pipe or other solid surface within the flow. The concept is that the flow near the surface is influenced by (among other things) the presence of the surface in that it "wants" to sort of stick to the wall. As a result there is a region of the flow which becomes progressively faster as position proceeds from the wall into the flow. In that region the flow is very much parallel to the surface. This region is referred to as "boundary layer." Further into the flow (beyond the boundary layer) the flow is said to be "turbulent." In this region the flow changes very dynamically, and is not generally parallel to the wall. The thickness of the boundary layer is largely defined by the viscosity velocity of the fluid and the geometry of the flow and the surface.

Heat issues arise in the boundary layer. In the turbulent flow area heat is moved quickly and in all directions resulting in fairly consistent temperatures. In the boundary the flow is organized and consistent resulting in a measurable (and predictable) gradient of temperatures across the layer as heat flows through it . Those are the concepts of thermal and velocity boundary layer issues.

It seems likely I have failed to provide the information you seek. My only advice is that if you ask a different (better focused, more complete) question you will likely get a better answer. Hope this helps.

R/

Sam Hicks

A few details. The boundary layer is not a "concept" but a reality. There is a property of fluids which has not been mentioned (or i did not notice it) viscosity, it is the reason a boundary layer appears.

The molecules of a fluid are at rest at the contact with a stationary border. Due to viscosity they interact with the nearby located molecules and do not let them move at full speed. Velocity will grow progressively from zero to a value where the influence of the wall is not any more sufficient and the fluid starts to move in a less organized manner. Near to the wall the boundary layer is parallel to the wall and laminar. It has been demonstrated that the thickness grows along the wall in the flow direction and that at some distance from the edge the thickness is such that the organized flow changes in a turbulent one so that the boundary layer becomes a least partly turbulent.

The higher the fluid viscosity is the thicker will be the transition (boundary) layer from speed zero and organized movement to disorganized movement (turbulent).

The smaller the mean speed the thicker the layer. Even in highly turbulent flows near to the wall a laminar boundary layer appears.

If there is a heat transfer from the wall to the fluid (or vice versa) all heat can only be transfered through the fluid in the boundary layer. A temperature rise in a fluid (not gas) leads to a viscosity reduction thus to a thinner boundary layer and to a higher convection (it comes from Latin taken with, transported).

Now a couple of applications of this knowledge:

- in heat transfer, a turbulent flow will allow a higher transfer intensity since more fluid will come to a contact with the wall, in order to obtain it tubes have for instance short finns (in flow direction) so that the layer will be as thin as possible and the turbulence as high as possible. A higher transfer intensity allows a surface reduction and reduces cost.

- hydrodynamic or aerodynamic friction reduction. It was noticed that the structure of sharks skin allows a better development of boundary layers, less turbulent, with less energy losses, submarines have such coatings.

Special texture were developed for plane wings in search of same effect: master the boundary layer and reduce losses.

- the different cabins used for return from space have a high radius spherical surface directed to earth during return flight because a high radius leads to a high boundary layer which is used in this case as a thermic insulation. It works also as n aerodynamic brake but the effect of a thicker layer is positive.