Wake vortex encounter risk is a major safety issue in aircraft final approach phase. The evaluation of the risk is crucial when the industry takes the effort to reduce aircraft spacing for the purpose of capacity gain. This paper proposes a hybrid analytical method to assess the wake vortex encounter risk during the final approach phase. The hybrid method uses probabilistic method to calculate ...

For moderate Reynolds numbers, a sphere striking a wall in the normal direction leads to the trailing recirculating wake threading over the sphere and developing into a complex vortex ring system as it interacts with the wall. The primary vortex ring, which consists of vorticity from the wake, persists and convects slowly outwards away from the sphere due to the motion induced from its image. T...

Abstract--The wake flow behind a normal or an inclined plate is predicted by a discrete-vortex method. The vortex shedding phenomenon at the leading and the trailing edges is simulated by a vorticity creation technique according to the Kutta condition. This approach required that the strengths and locations of discrete vortices just shed from the edges be determined such that their presence in ...

The bottom boundary layer (BBL) under an internal solitary wave (ISW) of depression is examined using highly resolved, spectral multidomain penalty-method based, Large Eddy Simulation. The focus is on the three-dimensionalization of the initial shear-instability-driven near-bed vortex wake in the lee of the wave and on the downstream formation of fully developed turbulence. When the ISW propaga...

This note reports on the influence of aircraft wake vortices on the estimation of the turbulent energy dissipation rate using sonic anemometer measurements near the runway threshold. The wake vortex traces, which are generated at a height of about 65m and subsequently evolve in ground effect, are clearly visible in the velocity components and temperature. The observed temperature increase of 1K...

While wake structures of many forms of swimming and flying are well characterized, the wake generated by a freely swimming undulating fin has not yet been analyzed. These elongated fins allow fish to achieve enhanced agility exemplified by the forward, backward and vertical swimming capabilities of knifefish, and also have potential applications in the design of more maneuverable underwater veh...

The wake states resulting from the controlled oscillation of a cylinder transverse to the free stream are presented. A new wake state is revealed by instantaneous measurements of the total and vortex lift phases, and the phase-referenced, quantitative wake structure. This ‘‘intermediate wake state’’ occurs at oscillation frequencies between the previously observed lowand high-frequency states. ...

Rotorcraft wake modeling is still a major concern in rotorcraft design and analysis as it influences the aerodynamic, aeroacoustic, and aeroelastic behavior of the vehicle. This paper presents a comprehensive overview of rotorcraft wake modeling, in particular in the last decade, from the experimental, theoretical and computational viewpoints. Present capabilities are discussed and trends for f...

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Free-vortex wake models are capable of providing an accurate and physically detailed representation of the main rotor wake for flight dynamics simulation. Recent advances in computing power and efficient algorithms have made it feasible to use free wakes for real-time simulation. The CHARM free-vortex wake model was integrated with the GENHEL flight dynamics simulation of the UH-60A helicopter....