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Topic: Flow separation

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	Boundary-Layer Separation
		The study of flow separation from the surface of a solid body, and the determination of global changes in the flow field that develop as a result of the separation, are among the most fundamental and difficult problems of fluid dynamics.
		It is well known that the separation is normally accompanied by a loss of the lift force, sharp increase of the drag, increase of the heat transfer at the reattachment region, pulsations of pressure and, as a result, flutter and buffet onset.
		Significant progress in theoretical study of separated flows has been achieved in the last thirty years, and a comprehensive description of the underlying ideas and the main results of the theory may be found in a monograph by Sychev et al (1998).
	www.maths.manchester.ac.uk /~ruban/blsep.html (1923 words)

	Boundary-Layer Separation
		The study of flow separation from the surface of a solid body, and the determination of global changes in the flow field that develop as a result of the separation, are among the most fundamental and difficult problems of fluid dynamics.
		It is well known that the separation is normally accompanied by a loss of the lift force, sharp increase of the drag, increase of the heat transfer at the reattachment region, pulsations of pressure and, as a result, flutter and buffet onset.
		The form of this singularity was first described by Landau & Lifshitz (1944) who demonstrated that the shear stress in the body surface upstream of separation drops as the square root of the distance from the separation, and the velocity component normal to the surface tends to infinity being inversely proportional to the shear stress.
	www.ma.man.ac.uk /~ruban/blsep.html (1923 words)

	Separation and Wakes
		For instance, in the flow through a large duct where the boundary layers are very thin, viscous effects are confined to a rather small region, and the fluid friction may sometimes be neglected.
		In contrast, when the flow is in the direction of decreasing area, as in the contraction flow shown in figure 11, there is very little risk of producing large separated regions, even for very large values of the included angle (up to 45^o), and generally losses are quite small.
		Friction is the source of the irreversibility of fluid flow: either through the formation of boundary layers over the surface, or large eddies in the wake (in thermodynamics we say that the entropy of the flow increases).
	www.princeton.edu /~asmits/Bicycle_web/separation.html (760 words)

	Quantitative Flow Visualization
		When the flow is passing by a bluff body, a strong adverse pressure gradient always presides over the rear half of the body and the flow separates.
		The flow separation prevents the pressure being recovered in the rear half of the object, therefore, causing a difference in pressure between the front and the back sides of the object.
		A jet is formed by flow issuing from a nozzle into ambient fluid which can be at rest (a free jet) or moving (a coflowing or counterflowing jet) or tangential to a solid surface (a wall jet).
	www.eng.fsu.edu /~shih/succeed/flow-vis.htm (995 words)

	[No title]
		Completely separated flow In cases 1a and 1b, the adverse pressure gradients were strong and persistent enough to cause a complete separation of the boundary layer without reattachment in the area that could be studied.
		Separation prediction In many practical applications, it is essential to be able to predict the position of flow separation, since it has a great effect on performance and heat transfer.
		Separated turbulent boundary layers of the studied type tend to be very sensitive to small pressure differences in the spanwise direction and it is very hard to establish a straight separation line perpendicular to the direction of the free-stream without a separation trip.
	www.f.kth.se /~f92-jgu/exjobb/exjobb.txt (7949 words)

	Flux diverting flow chamber for high gradient magnetic separation of particles from a liquid medium - Patent 4664796
		A separator apparatus according to claim 4 wherein said one output port of said first flow chamber is coupled to said one input port of said second flow chamber.
		A separator apparatus according to claim 7 wherein said one output port of said first flow chamber is coupled to said one input port of said second flow chamber.
		The separator 10 of the present embodiment is disclosed with a permanent magnet for generating the magnetic field used in particle separation.
	www.freepatentsonline.com /4664796.html (5606 words)

	Flow separation images (Site not responding. Last check: 2007-10-18)
		The tests were performed to verify computer predictions of the aerodynamics of a thin, sail like airfoil, as well as to study separation bubbles behind the mast and evaluate the effect of mast shape on the performance of the sail.
		The disturbance caused by the leeward side separation bubble at the luff ("leeward telltails flying") is strong enough to trigger the flow separation at the leech.
		Flow speeds ranging from 10 to 40 m/s were tried, and it was found that Reynolds Number had no influence on the aerodynamic characteristics of the thin, sail-like airfoil.
	www.wb-sails.fi /news/Stallpics_print.HTML (493 words)

	Flow Over a Circular Cylinder
		Therefore, the boundary layer flow is sensitive to the external pressure gradient (as the form of a pressure force acting upon fluid particles).
		Averaged velocity profiles of the flow past a circular cylinder is provided as a general representation of the wake flow field.
		Near the cylinder, flow separates from the surface.
	www.eng.fsu.edu /~shih/succeed/cylinder/cylinder.htm (1582 words)

	Standard Cirrus Oil Flow Tests
		But, the good part is that turbulent flow stays attached to curved or bent surfaces much better than laminar flow and that is very important for the proper operation of control surfaces and for holding off the stall condition at low airspeeds.
		Depending on the airfoil and flight conditions, separation bubbles may form to any degree, from no bubble at all to fully developed bubbles that are tall enough to add to the form drag of the wing by forcing the free stream flow to detour around them.
		If you compare the diagram of a separation bubble (above) to the oil flows, it can be seen that the region where the oil flow begins thickening in front of the main line of oil is the region of increasing separation leading back to the thickest part at the rear where the flow reattaches.
	www.standardcirrus.org /OilFlows.html (1723 words)

	GALLERY
		Flow separation around an NACA 0012 airfoil at 12° and 20° angles of attack has be investigated by direct numerical simulation (DNS).
		The three-dimensional separated flow around a slender flat-plate delta wing with sharp leading-edge at a 12.5 degree angle of attack has been studied by direct numerical simulation.
		Flow separation and strong streamwise vortex are observed.
	www.uta.edu /faculty/hshan/research/gallery.shtml (1023 words)

	KTH in your Pocket: Investigation of turbulent flow separation using particle image velocimetry (PIV) (Site not responding. Last check: 2007-10-18)
		Flow separation occurs as a result of flow deceleration over the surface of bodies such as lifting wings, turbomachinery blading or diffusers.
		Flow separation can be controlled to some extent by introducing longitudinal vortices in the boundary layer.
		In non-decelerating flow, the sublayer is much thinner than the light sheet, but in decelerating flow the viscous scale increases, making it possible to perform PIV measurements within the sublayer.
	www.kth.se /forskning/pocket/project.asp?id=3688 (316 words)

	Baylor University \|\| Engineering Research \|\| Effects of Flow Separation on Low Pressure Gas Turbine Blades
		However, at lower Re number flow, the Pak B blade suffers from flow separation due to adverse pressure gradients on the suction surface side of the blade [3].
		To account for this separation it is important to study the location along the axial chord where the flow transitions from laminar to turbulent [2].
		Then to achieve better separation from the aft portion of the flat plate the freestream velocity needs to be lowered to decrease the amount of energy in the air which will promote more flow separation.
	www.ecs.baylor.edu /engineering/research/index.php?id=31811 (3401 words)

	Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine
		Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils.
		In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation.
		A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level.
	www.grc.nasa.gov /WWW/RT/2003/5000/5820ashpis.html (821 words)

	Aerodynamics of the Delta Wing
		Flows past delta wings are severely compounded by the leading edge separation, by the roll-up structure of the concentrated vortices, and by the lateral and longitudinal instability that is consequent to large sweeps, high-angle of attack, and sharp manoeuvres.
		Separation is at the leading-edge when the leading edge is sharp, and leads to performances largely independent from the Reynolds number.
		Flow separation characteristics depend on speed (Mach number), wing sweep, angle of attack and wing thickness.
	aerodyn.org /Wings/delta.html (1300 words)

	Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine
		Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils.
		In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation.
		A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level.
	www.lerc.nasa.gov /WWW/RT/2003/5000/5820ashpis.html (821 words)

	Gabbai.com \| Flow Separation Detection (Site not responding. Last check: 2007-10-18)
		Using this visual method of separating the results it becomes very clear that there is indeed a difference in amplitude between the attached and separated flows.
		Now that it has been proved that flow separation can in fact be detected simply and cheaply using microphones and neural network software, one must look into the near future, where consideration must given to further experimenting, different artificial intelligence techniques and more advanced hardware, as well as long-term possibilities.
		In short, previously hard to determine separated flows were found to be significantly different to attached flows, even though the amplitudes were in the same range.
	www.gabbai.com /Neural_Nets/Neural_Nets.html (5001 words)

	Aerospaceweb.org \| Ask Us - Golf Ball Dimples & Drag
		The point at which the flow breaks away from the surface is called the separation point, and the flow downstream of this point is referred to as separated.
		One of the key factors affecting flow separation is the behavior of the boundary layer.
		Both the vortex generator and the LEX are primarily used to delay the flow separation that occurs when operating at high angles of attack near stall.
	www.aerospaceweb.org /question/aerodynamics/q0215.shtml (2202 words)

	3-D Flow Separation, Aerodynamics
		Definition of flow separation in three-dimensional flows is somewhat elaborate, since is must describe several topological features at solid walls that are not present in two-dimensional flows.
		In 2-D flows separation is identified by a region of backflow, and at the wall by a zero skin friction.
		Devices most commonly used for the study of 3-D separation include prolate spheroids, blunt and pointed cones at incidence, where non-axisymmetric vortex formation appear (all axisymmetric bodies at incidence are very prone to flow separation with consequent instability).
	www.aerodyn.org /Wings/3dsepar.html (486 words)

	Flow Control
		The traditional approach to the control of shear layer flows and enhancement of mixing has focused on the manipulation of global motions that are induced by the fundamental instability modes.
		The shear layer is generated by the flow separation off the edge of a backward-facing step, which is known to evolve similarly to a plane free shear layer in the near field.
		Locally, the development of a shear layer at the origin of a separated region is subject to the same instability considerations as that in a two-dimensional flow.
	www.me.gatech.edu /bvukasinovic/flowcontrol.html (431 words)

	Unidirectonal Flow Bedforms (Site not responding. Last check: 2007-10-18)
		Increased erosion associated with flow re-attachment tends to entrain grains which then move up the stoss side of the downstream pile of grains until they reach the next point of flow separation.
		The bed surface in upper plane bed flow is marked in detail by system of low linear ridges, a few grain diameters high, which align parallel to flow direction.
		Flow in the tidal channel is from lower right to upper left (i.e.
	www.umt.edu /geosciences/faculty/hendrix/g432/g432_L7.htm (1510 words)

	Aerodynamics of Teardrop Wingmasts
		The slower speed flow in the boundary layer displaces the outer flow as though the surface had a different shape, and the red and blue lines at the bottom of Figure 1 show this effective shape.
		However, the trailing edge separation point is also moving upstream and the deviation of the displaced outer flow from the sail shape at the trailing edge reduces the lift from its potential value.
		On the windward side, the separation point moves aft on the mast with increasing angle of attack and the reattachment point moves forward, shrinking the size of the separation bubble.
	www.tspeer.com /Wingmasts/teardropPaper.htm (7043 words)

	Contours - Issue 36 - Tecplot Blog: Scott Imlay (Site not responding. Last check: 2007-10-18)
		A flow separation (or boundary-layer separation) is a region, usually near the wall, where the flow is moving more-or-less in the opposite direction of the general flow.
		The flow is moving the wrong direction in a region of flow separation.
		This data is for transonic flow and there is a shock wave on the upper surface of the wing which is strong enough to create an isolated flow separation bubble.
	www.tecplot.com /showcase/contours/issue_37/article04.htm (988 words)

	Turbulators on Standard Cirrus Sailplanes
		This transition is often accompanied by a separation of the laminar flow from the wing surface and a reattachment later of turbulent flow that remains attached better than laminar flow, but increases drag.
		Turbulator tapes are often used to eliminate the separation bubble, and the additional form drag it causes, by tripping the laminar flow to turbulent flow at some point before the separation becomes high enough to cause significant additional form drag.
		Oil flow images and reports of wind tunnel tests suggest that no advantage can be gained from using turbulators on the outer panel of the lower surface.
	www.standardcirrus.org /Turbulators.html (1146 words)

	Thesis 'Flow Separation on Wind Turbine Blades' (Site not responding. Last check: 2007-10-18)
		The angle of attack of the flow incident to the blades is determined by the blade speed and the wind speed.
		The art of designing stall rotors is to make the separated area on the blades extend in such a way, that the extracted power remains precisely constant, independent of the wind speed, while the power in the wind at cut-out exceeds the maximum power of the turbine by a factor of 8.
		We add the argument that the chord-wise speed and its derivative normal to the wall is zero at the separation line, which causes the terms with the chord-wise speed or accelerations to disappear.
	www.ecn.nl /library/thesis/corten.html (1770 words)

	Control of Flow Separation by means of electromagnetic forces (Site not responding. Last check: 2007-10-18)
		Flow separation may occur in situations, where a boundary layer flow slowed down by wall friction is exposed to an adverse pressure gradient.
		Flow separation imposes severe limitations on the design and operation of several fluid mechanic devices.
		The streamlines formed by the particles indicate a flow field, which is approximately that of a potential flow.
	www.fzd.de /FWS/FWSH/EBLC/separation-control/separation-control.html (1425 words)

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