Download or read book Motion of Aircraft Wake Vortices in Ground Effect written by David C. Burnham and published by Createspace Independent Publishing Platform. This book was released on 2000-04-30 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report addresses the wake-turbulence separation standards for close-spaced parallel runways. Ground-wind anemometer data collected at Kennedy (landing) and O-hare (takeoff) airports are analyzed to assess the lateral transport probability for wake vortices.

Download or read book A Technique for Simulating the Motion and Ground Effect of Aircraft Wake Vortices written by R. H. Wickens and published by . This book was released on 1975 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wake Turbulence written by United States. Federal Aviation Administration and published by . This book was released on 1971 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vortex wakes of Aircrafts written by A.S. Ginevsky and published by Springer Science & Business Media. This book was released on 2009-07-07 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigation of vortex wakes behind various aircraft, especially behind wide bodied and heavy cargo ones, is of both scientific and practical in terest. The vortex wakes shed from the wing’s trailing edge are long lived and attenuate only atdistances of10–12kmbehindthe wake generating aircraft. The encounter of other aircraft with the vortex wake of a heavy aircraft is open to catastrophic hazards. For example, air refueling is adangerous operationpartly due to thepossibility of the receiver aircraft’s encountering the trailing wake of the tanker aircraft. It is very important to know the behavior of vortex wakes of aircraft during theirtakeoff andlanding operations whenthe wakes canpropagate over the airport’s ground surface and be a serious hazard to other depart ing or arriving aircraft. This knowledge can help in enhancing safety of aircraft’s movements in the terminal areas of congested airports where the threat of vortex encounters limits passenger throughput. Theoreticalinvestigations of aircraft vortex wakes arebeingintensively performedinthe major aviationnations.Usedforthispurpose are various methods for mathematical modeling of turbulent flows: direct numerical simulation based on the Navier–Stokes equations, large eddy simulation using the Navier–Stokes equations in combination with subrigid scale modeling, simulation based on the Reynolds equations closed with a differential turbulence model. These approaches are widely used in works of Russian and other countries’ scientists. It should be emphasized that the experiments in wind tunnels and studies of natural vortex wakes behind heavy and light aircraft in flight experiments are equally important.

Download or read book Proceedings of the Aircraft Wake Vortices Conference Washington D C October 29 31 1991 written by and published by . This book was released on 1992 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aircraft Wake Turbulence and Its Detection written by John Olsen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 599 pages. Available in PDF, EPUB and Kindle. Book excerpt: The combination of increasing airport congestion and the ad vent of large transports has caused increased interest in aircraft wake turbulence. A quantitative understanding of the interaction between an aircraft and the vortex wake of a preceding aircraft is necessary for planning future high density air traffic patterns and control systems. The nature of the interaction depends on both the characteristics of the following aircraft and the characteristics of the wake. Some of the questions to be answered are: What deter mines the full characteristics of the vortex wake? What properties of the following aircraft are important? What is the role of pilot response? How are the wake characteristics related to the genera ting aircraft parameters? How does the wake disintegrate and where? Many of these questions were addressed at this first Aircraft Wake Turbulence Symposium sponsored by the Air Force Office of Sci entific Research and The Boeing Company. Workers engaged in aero dynamic research, airport operations, and instrument development came from several count ries to present their results and exchange information. The new results from the meeting provide a current picture of the state of the knowledge on vortex wakes and their interactions with other aircraft. Phenomena previously regarded as mere curiosities have emerged as important tools for understanding or controlling vortex wakes. The new types of instability occurring within the wake may one day be used for promoting early dis integration of the hazardous twin vortex structure.

Download or read book A Parametric Study of Accelerations of an Airplane Due to a Wake Vortex System written by Eric C. Stewart and published by . This book was released on 1999 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Pressure Field of a Vortex Wake in Ground Effect written by Clinton E. Brown and published by . This book was released on 1975 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ground pressures under a descending pair of vortices, such as might be generated by aircraft either landing or taking off are computed. It is found that as the vortices first approach the ground, only positive pressures are produced; however as the descent continues the high velocity field of the vortices makes itself apparent in dips to sub-atmospheric pressure which lie closely beneath the vortex center. Nevertheless, a substantial positive pressure hill precedes the path of the vortex as it moves laterally in the 'ground effect'. The level of pressures produced is dependent only on the flight speed, lift coefficient and aspect ratio while the length scale of the pressure distribution is proportional to the span. These results may be useful in the development of systems to monitor multiple aircraft take-off and/or landing operations.

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 Dynamics of Longitudinal Wake Vortices written by Linda K. Kliment and published by . This book was released on 2009 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present study, the mid-field vortex wake is investigated. For the most part, the results focus on the motion of a pair of co-rotating vortices prior to merger, both in and out of ground effect. However, in order to verify the experimental and computational methods, results for single vortices, counter-rotating pairs, and complex wakes are also presented. A method is presented which allows measurement of the time dependent motion of vortex filaments. This optical method interferes minimally with the wake and allows recording of vortex location and time-dependent motion. From the position and time information recorded, extraction of the amplitudes of motion, core motion, spiraling behavior, vortex strengths, and the principal planes of motion is possible. First, a single vortex is studied in order to establish a basis for comparison. The dye remains in the core and the motion of a single vortex is shown to exhibit a growth in amplitude with increasing downstream distance and strength. The core motion is shown to be minimal, remaining smaller that one core diameter. In addition, when the single vortex is forced to oscillate at a given frequency, the dye still remains in the core, even though the amplitudes of motion are large. The forcing frequency is identified easily against the background noise. Two four-vortex cases are then presented. The first case consists of filaments that spiral while in the second they scatter. These results are consistent with those shown in literature and show that the experimental method can be used for analyzing complex wakes. Pairs of unforced, co-rotating filaments are studied outside of ground effect. Many cases are presented, some for nearly equal strengths and others in which one vortex is much stronger than the other. As in the single-vortex case, the amplitudes of motion are shown to increase as the downstream distance becomes greater. The constant rate of spiraling is shown to increase as the vortex strength increases and vortex span decreases. Vortex span either remains constant or decreases with downstream distance depending on the vortex separation distance. The motion of the center of spiraling is shown to be minimal, similar to the motion of the vortex core in the single-vortex cases. The filaments are shown to sometimes oscillate along preferred directions, which is inconsistent with a theoretical model developed in 1975. A few cases are also presented in which the merger location is analyzed. However, these are visual investigations only, since it is not possible to obtain quantitative data for such cases with the experimental method available. The behavior of co-rotating vortices in the presence of forcing functions is then presented. The results are compared to the theoretical model developed in 1975 and those published after 2002. However, a direct comparison with analytical results is not possible due to the large scatter in the experimental data. Regardless, the experimental results show that the forced corotating vortices do have an unstable oscillatory motion with growing amplitude. The preferred direction of motion implies the presence of stationary waves. These results contradict those of the analytical model developed in 1975 but agree in nature with those published more recently. Ground effect is then considered for counter-rotating vortices, because there is a wealth of information on this topic in the literature. When counter-rotating vortices are near a ground plane, a lateral drift as well as a rebounding behavior is present. The counter-rotating vortices are shown to have a preferred direction of motion which tends to become parallel to the ground plane. The motion is also shown to have increasing amplitude, although this quantity is slightly reduced by the presence of the ground plane. In addition, ground roughness in the form of streamwise ridges has no affect on the vortex trajectories, within the range of downstream distances observable in these experiments. After comparing the results to those in literature, it is concluded that the experimental method is valid and can be used to study co-rotating vortices in ground effect. Literature lacks information on co-rotating vortices in ground effect. The results in this document show that co-rotating vortices in ground effect have a lateral drift as well as a rebound similar to those of counter-rotating pairs. The resulting motion is similar to that of leapfrogging vortex rings. Preferred directions of motion are present, although no trend can be established. In addition, the amplitudes of motion are reduced slightly by the presence of the ground, just as they are for the counter-rotating vortices. Due to the lack of information on co-rotating vortices in ground effect in the current literature, a comparison is impossible. Therefore, two simple computation efforts are undertaken in order to verify some of the flow features. Using a two-dimensional viscous analysis, limited to laminar flow, it is shown that when co-rotating vortices are placed near a stationary wall, a boundary layer forms on the surface and separates. The secondary vortex released by boundary layer separation leads to rebounding of the primary vortices. In addition to affecting the trajectory, the no-slip boundary also affects the time to vortex merger as well as leading to an elongation of the vorticity contours. Furthermore, this analysis demonstrates that making the strengths of the two vortices differ slightly does not affect the spiraling rate, surface boundary layer separation, or rebound. A second inviscid model is also used to study cases consisting of two vortices of unequal strengths. Having unequal strengths does affect the lateral drift of corotating vortices in ground effect. Also, the center of spiraling shifts towards the stronger vortex. However, the inviscid model shows that the vortex span is unaffected by difference in strengths.

Download or read book Aircraft Vortex Wake Decay Near the Ground written by and published by . This book was released on 1977 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vortex wall Interactions and Sports inspired Airfoil Motions written by Sarah Elizabeth Morris and published by . This book was released on 2020 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding vortex-wall interactions has applications in the context of airplane trailing vortices, as wake vortices are an unavoidable by-product of aerodynamic lift. These vortices pose an increased hazard for aircraft at airport takeoffs and landings, as following aircraft flying through a vortex wake can experience dangerous rolling moments. In this work, we use a vortex generator tank and a delta wing in an XY-Towing Tank to study the dynamics of counter-rotating vortex pairs both in and out of ground effect, via PIV and flow visualization. When a vortex pair approaches a ground plane, the boundary layer that forms on the surface between the vortices and the wall separates, generating secondary vorticity and causing the primary vortex pair to ``rebound'' from the wall. Using a vortex generator tank to produce a temporally evolving vortex pair, it is shown that the introduction of perturbations at the ground plane results in earlier localized secondary vorticity generation. This leads to the formation of coherent secondary vortex structures, and an accelerated decay of the primary vortex pair. This passive, ground-based method could be a means to diminish the wake vortex hazard behind aircraft close to the ground. We study also the spatially evolving trailing vortices in the far-wake of a 75 degree leading-edge sweep-angle delta wing, using a novel technique to measure the axial flow in the vortex core. This technique is unaffected by vortex wandering, allowing us to capture axial flow data as close as 0.03 chord-lengths apart. Using this technique, the streamwise velocity profile is captured over 20 chord-lengths downstream of the delta wing, even when the vortex pair is in ground effect. In this thesis, we also study new modes of NACA 0012 airfoil motions using a ``sports-mimetic'' approach, inspired by the bodyweight motions of Olympic sailors as they maneuver their sailboats when racing. Olympic sailors use various unsteady aerodynamic techniques when racing to increase propulsion for their boat. One such technique is for sailors to use bodyweight movements to roll the boat about its longitudinal axis. This motion is used especially when turning in light winds by either ``roll tacking'' (upwind sailing) or ``roll gybing'' (downwind sailing); it is also used in ``sail flicking'' whereby the sailor rolls the boat, flicking the sail periodically. These motions are characterized in on-the-water experiments using a Laser sailboat and a 420 sailboat, equipped with a GPS, IMU, wind sensor and GoPro camera array. We study the underlying vortex dynamics of these maneuvers using these characteristic motions, along with full-scale flow visualization and laboratory experiments. Flow visualization experiments are conducted on Cayuga Lake with an Olympic Laser Sailboat, using an Enola Gaye WP40 smoke grenade to visualize large-scale flow features around the sail.

Download or read book A Parametric Study of Accelerations of an Airplane Due to a Wake Vortex System written by National Aeronautics and Space Administration and published by . This book was released on 2018-08-27 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study was conducted using strip theory to systematically investigate the effects of progressively more complete descriptions of the interaction of an airplane with a wake vortex system. The emphasis was in roll-dominant, parallel, vortex encounters. That is, the simulated airplane's longitudinal axis was nearly parallel to the rotation axis of the vortex system for most of the results presented. The study began with a drag-less rectangular wing in the flow field of a single vortex and progressed to a complete airplane with aerodynamic surfaces possessing taper, sweep, dihedral, and stalling and immersed in the flow field of a vortex pair in ground effect. The effects of the pitch, roll, and yaw attitudes of the airplane on the calculated accelerations were also investigated. The airplane had the nominal characteristics of a Boeing 757, and the vortex flow field had the nominal characteristics of the wake of a Boeing 767. The Bumham-Hallock model of a vortex flow field was used throughout the study. The data are presented mainly in terms of contours of equal acceleration in a two-dimensional area centered on the vortex pair and having dimensions of 300 feet by 300 feet.Stewart, Eric C.Langley Research CenterAERODYNAMICS; FLOW DISTRIBUTION; RECTANGULAR WINGS; ROLL; ROTATION; VORTICES; YAW; AIRCRAFT WAKES; MATHEMATICAL MODELS; BOEING 757 AIRCRAFT; BOEING 767 AIRCRAFT; GROUND EFFECT (AERODYNAMICS)...

Download or read book Response of Aircraft Encountering Aircraft Wake Turbulence written by Robert C. Nelson and published by . This book was released on 1974 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The investigation deals with the dynamic behavior of an airplane encountering aircraft wake turbulence. A digital computer simulation was developed to study the response of an aircraft flying into a trailing vortex wake. The simulation includes the complete six degree of freedom equations of motion, a description of the vortex velocity field, unsteady aerodynamics, and pilot control input. The parameters included the penetration angle, separation distance, aircraft size, and pilot control input. Predicted vortex induced motions are presented for general aviation, business, and light jet transport type aircraft.

Download or read book Atmospheric wake Vortex Interactions written by and published by . This book was released on 1978 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aircraft Wake Vortices written by T. E. Sullivan and published by . This book was released on 1990 with total page 72 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...