Download or read book The Stability of a Vortex Pair in the Presence of a Ground Plane written by Nicholas R. Rotta and published by . This book was released on 1971 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The configuration stability of a vortex pair in the presence of a ground plane is examined. First the motion of a vortex in three dimensions is examined by the method of matched asymptotic expansions in which the solution of the Navier-Stokes equations are constructed asymptotically. The dependence of the velocity and stability of the vortex on factors such as the outer(inviscid) flow field and viscosity in the inner (vortical core) region is clearly established. The proximity of the ground plane enters through the outer solution which is matched to the inner, viscosity dependent, solution. The vortex pair in ground effect is shown to be unstable to disturbances of all wavelengths with increasing amplification rate as the ground is approached. Indications are that the present analysis predicts a more stable (less unstable) vortex system than does the inviscid theory. Comparison of the present analysis, in the limit of zero ground effect, with photographs of vortices undergoing a configuration instability is made. The viscosity necessary for agreement is found to be on the order of the eddy viscosity for the turbulent line vortex, indicating the existence of turbulence in the vortex core. (Author).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Paper written by and published by . This book was released on 1985 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Air Pollution Abstracts written by and published by . This book was released on 1972 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aircraft Wake Vortices written by James N. Hallock and published by . This book was released on 1991 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the National Aerospace Electronics Conference written by and published by . This book was released on 1971 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Pair Instabilities in Ground Effect written by James Gerard Fogg and published by . This book was released on 2001 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Wake Alleviation Studies with a Variable Twist Wing written by G. Thomas Holbrook and published by . This book was released on 1985 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Wake Alleviation Studies with a Variable Twist Wing written by and published by . This book was released on 1985 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Index written by and published by . This book was released on 1972 with total page 1074 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements written by and published by . This book was released on 1972 with total page 844 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Congress of the International Council of the Aeronautical Sciences written by International Council of the Aeronautical Sciences. Congress and published by . This book was released on 1974 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On the Stability of Vortex Motions in the Presence of Magnetic Fields written by Y. T. Fung and published by . This book was released on 1982 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stability analyses are performed on a general type of vortex flows with density inhomogeneity and with both the axial and azimuthal magnetic fields. A sufficient condition for stability, subject to arbitrary perturbations, is derived. The condition, however, involves the complex eigenfrequency. Nevertheless, we are able to examine how the flow profile influences the flow characteristics by studying three general types of perturbations. Analytical solutions are obtained to support the resultant arguments. Unlike the axial velocity which always destabilizes the flow, the azimuthal velocity can convey either stabilizing or destabilizing effects depending on the gradient it possesses and the centrifugal force field it creates. This characteristic is shown in all the three general types of perturbations to the flow. For flow subject to azimuthal perturbations, an upper bound on the complex phase velocity, which is reminiscent of the semi-ellipse theorem in the non-hydromagnetic case, is found for some flow profiles satisfying a constraint. Even though it cannot be observed directly from the sufficiency conditions or from the bound on the unstable waves, we are able to show that the presence of the magnetic field, regardless of the detailed profile, always stabilizes azimuthal perturbations. Such an argument is also supported by exact solutions to the governing stability equations. For uniform rotation and constant Alfven velocities, azimuthal instabilities can only occur when negative density gradients exist within the flow domain. Furthermore, the phase velocity for such instabilities must lie on a semi-circle in the complex phase velocity plane independent of the detailed density profile.
Download or read book A Collection of Technical Papers written by and published by . This book was released on 1984 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1948 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seventh Conference on Aerospace and Aeronautical Meteorology and Symposium on Remote Sensing from Satellites November 16 19 1976 Melbourne Fla written by and published by . This book was released on 1976 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Viscous Effects on a Vortex Wake in Ground Effect written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-15 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wake vortex trajectories and strengths are altered radically by interactions with the ground plane. Prediction of vortex strength and location is especially important in the vicinity of airports. Simple potential flow methods have been found to yield reasonable estimates of vortex descent rates in an otherwise quiescent ambient background, but those techniques cannot be adjusted for more realistic ambient conditions and they fail to provide satisfactory estimates of ground-coupled behavior. The authors have been involved in a systematic study concerned with including viscous effects in a wake-vortex system which is near the ground plane. The study has employed numerical solutions to the Navier-Stokes equations, as well as perturbation techniques to study ground coupling with a descending vortex pair. Results of a two-dimensional, unsteady numerical-theoretical study are presented in this paper. A time-based perturbation procedure has been developed which permits the use of analytical solutions to an inner and outer flow domain for the initial flow field. Predictions have been compared with previously reported laminar experimental results. In addition, the influence of stratification and turbulence on vortex behavior near the ground plane has been studied. Zheng, Z. and Ash, Robert L. Unspecified Center NAG1-987...
