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Showing papers on "Starting vortex published in 1969"


Journal ArticleDOI
TL;DR: In this paper, a general discussion of the superfluidity of a dense liquid is given, in which it is shown that high rates of shear give difficulty, and an equation is constructed which describes the flow of a continuous incompressible superfluid at zero temperature with a resistance to shear.

81 citations


Patent
09 Jun 1969
TL;DR: A vortex generator for the ends of airfoil structures that directs air on the high pressure side of the structure into a vortex generator chamber and discharges the swirling air at the trailing edge is described in this article.
Abstract: A vortex generator for the ends of airfoil structures that directs air on the high-pressure side of the structure into a vortex generator chamber and discharges the swirling air at the trailing edge of the structure. The exit orifice of the vortex generator may be directed at fixed or variable attitudes for causing the vortex created by the generator to either increase or decrease lift provided by the airfoil structure.

52 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the turbulent vortices are only shed two-dimensionalally when the gap between the end-plates is less than or equal to four times the base height of the shedding body.
Abstract: Spanwise velocity correlations of the turbulent vortices shed by a two-dimensional bluff body of D-section are presented for different aspect ratios of the shedding body between end-plates. From these it is shown that the vortices are only shed two-dimensionally when the gap between the end-plates is less than or equal to four times the base height of the shedding body.

36 citations



Patent
John R Erwin1
02 Jan 1969
TL;DR: In the fan portion of a turbofan engine, rotor blades comprise a primary cambered airfoil and an auxiliary air-foil as mentioned in this paper, where the throat section between adjacent blades positions the normal air shock wave on the auxiliary airfoil, creating oblique shock waves which weaken the normal shock wave and minimize energy losses.
Abstract: In the fan portion of a turbofan engine, rotor blades comprise a primary cambered airfoil and an auxiliary airfoil. Where air flow exceeds a sonic velocity relative to the blades, the throat section between adjacent blades positions the normal air shock wave on the auxiliary airfoil. Each auxiliary airfoil forms a nozzle in combination with the pressure surface of its adjacent primary airfoil. This minimizes energy losses normally associated with such normal shock waves riding on the suction surfaces of cambered airfoils in regions of relatively thick boundary layer air. Lateral struts projecting from the primary airfoil, and used to position the auxiliary airfoil, create oblique shock waves which weaken the normal shock wave and minimize energy losses associated with a normal shock wave''s effect of distributing boundary layer air on an airfoil surface. These features are also effective in reducing the generation of noise.

28 citations


Journal ArticleDOI
TL;DR: In this article, a theoretical and experimental analysis was performed to determine the effect that the wing geometry and the boundary layer on the lower surface of the wing have on the trailing rolled-up tip vortex.
Abstract: A theoretical and an experimental analysis was performed to determine the effect that the wing geometry and the boundary layer on the lower surface of the wing have on the trailing rolled-up tip vortex. Model test results are presented for the vortex structure downstream of wings of varying aspect ratio and taper ratio. The geometry and strength of the rolled-up tip vortices were measured over a range of lift coefficients. In general, it was found that the strength of the vortex is less than one would predict on the basis of the midspan circulation about the wing. Conclusions are given with regard to the size and strength of a vortex as they relate to the wing aspect ratio, taper ratio, and lift coefficient.

23 citations




Book ChapterDOI
TL;DR: In this article, a flow field of these vortices was studied by observing and registering tracks of small particles on the free surface of the liquid, and it was shown that each of the vortice constituting the Karman street is not a completely isolated vortex structure in an unbounded medium, because it experiences the influence of the closely located body that is flowed past and the whole chain of the karnes.
Abstract: Theoretical models of vortex rings obtained in the framework of the ideal fluid theory apparently give only a qualitative idea of a structure and characteristics of vortex rings that form and exist in a real viscous fluid. Until recently, direct experimental studies of the hydrodynamic structure of real vortex rings have been lacking, and thus it has not been clear how realistically theoretical models of vortex rings reflect the actual phenomenon. The lack of reliable experimental data on the structure of a vortex ring and on the structure of concentrated vortices in general, with the latter being one of the basic types of fluid and gas motion in natural conditions and in technical devices, is mostly explained by complexity and unsteady character of vortex motion in a fluid, and by imperfection of suitable scientific instrumentation. There are only experimental investigations by Timme (1957) and Kirde (1962), who studied the structure and evolution of one of the types of concentrated vortices forming in a crossflow past a cylindrical body and representing the so-called Karman vortex street (Karman and Rubach 1912; Schlichting 1969). In the experiments these vortices appeared on the water surface during the horizontal motion of a vertically set cylinder which was partly extended above the surface. A flow field of these vortices was studied by observing and registering tracks of small particles on the free surface of the liquid. However, it is clear that each of the vortices constituting the Karman street is not a completely isolated vortex structure in an unbounded medium, because it experiences the influence of the closely located body that is flowed past and the whole chain of the Karman vortices. These investigations give only an indirect idea of the structure of single concentrated vortices. The difficulties in performing direct measurements of a velocity field of vortices developing in actual conditions, such as whirlwinds, tornados, and hurricanes, are quite obvious.

11 citations




01 Jul 1969
TL;DR: The aerodynamic characteristics of an 11 percent thick symmetrical supercritical airfoil were determined in an 8 foot transonic pressure tunnel over a Mach number range of 0.30 to 0.85 as discussed by the authors.
Abstract: The aerodynamic characteristics of an 11 percent thick symmetrical supercritical airfoil were determined in an 8 foot transonic pressure tunnel over a Mach number range of 0.30 to 0.85. The Reynolds number of the tests, based on the airfoil chord, varied with Mach number over a range of 360 million to 774 million. The geometric angle of attack varied from -0.5 to 10.5 deg. The abrupt drag rise for the supercritical airfoil at zero normal force conditions occurs at a Mach number just above 0.82. The corresponding drag rise Mach number for a conventional NACA 0012 airfoil is approximately 0.70. At zero normal force conditions, the level of supervelocity over the supercritical airfoil is considerably reduced from that for the NACA 0012 airfoil. Also, the shock wave for the supercritical airfoil is substantially weaker than that for the NACA 0012 airfoil. For a Mach number of 0.82 and zero normal force, the flow over the present airfoil is supercritical; however, there is no discernible shock wave in the flow, indicating near isentropic recompression.

Proceedings ArticleDOI
01 Jun 1969
TL;DR: Vortex motion enhancement of jet penetration and spreading in supersonic fuel injection into large diameter combustors was studied in this paper, where the authors showed that the effect of vortex motion enhancement on jet penetration was negligible.
Abstract: Vortex motion enhancement of jet penetration and spreading in supersonic fuel injection into large diameter combustors

Journal Article
TL;DR: In this paper, the performance of an augmentor wing was examined with a simplified model that consists of a thin airfoil with a jet-augmented flap and a sink located at the hinge of the flap.
Abstract: The performance of an augmentor wing has been examined with a simplified model that consists of a thin airfoil with a jet-augmented flap and a sink located at the hinge of the flap. The analysis is based on a small disturbance theory. The results for the basic configuration, namely the airfoil with a jet-augmented flap, agree very well with those obtained by other authors. It shows that the lift on the airfoil can be increased appreciably with a jet-augmented flap. Suction on the upper surface of the airfoil can also induce additional lift on the system. This induced lift becomes more efficient as the suction slot moves towards the trailing edge. However, the lift decreases slightly as the jet momentum flux increases and the jet becomes more "stiff".

Journal ArticleDOI
TL;DR: In this paper, the authors describe the coupled diffusion of heat and vorticity in a high temperature, low speed, gaseous vortex, which is caused by both a radial convection of mass resulting from the unsteady heating of the gas and the temperature dependence of gas properties, and the numerical results were obtained by simultaneously solving the fluid heat conduction, continuity and Navier-Stokes' equations on a digital computer using a finite difference technique.

Journal ArticleDOI
TL;DR: In this article, it is shown that the plates produced on a liquid jet by finite amplitude pressure fluctuations at the orifice are associated with the phenomenon of vortex-ring formation in the jet.
Abstract: It is postulated that the plates produced on a liquid jet by finite amplitude pressure fluctuations at the orifice are associated with the phenomenon of vortex-ring formation in the jet. An experimental determination of the pressure profile, using a specially designed pressure probe, in the presence of such pressure fluctuations, produced results consistent with the presence of vortex rings. For weak rings (small pressure fluctuation amplitude) the transverse pressure force produced by the vortex is small and can only trigger the capillary instability. With strong rings the force can overcome the restraining surface tension force, thus producing a plate on the jet. The low pressure produced inside the vortex ring causes fluid to flow in from adjoining parts of the jet and so mass modulation occurs. The author has already shown that the injector vibration produces a pressure variation upstream of the orifice. This in turn results in mass modulation which can trigger combustion instability in liquid fuel rocket engines. The vortex-ring theory provides considerable insight into the coupling between injector vibration (or any source of upstream pressure fluctuation) and the combustion process. Nomenclature AR = cross-sectional area of the vortex ring [Eq. (13)] a = radius of the vortex core E = energy of the vortex ring [Eq. (11)] g = gravity constant H = depth of the fluid I = impulse of the vortex ring [Eq. (8)] PC = pressure in the neighborhood of the vortex core po = pressure in the center of the liquid jet TO = radius of the vortex ring [Eq. (11)]; original jet radius