Multiple Jet/Wall/Cross-Wind Interaction Relevant to VSTOL Ground Effects

Barata, Jorge M. M.

doi:10.2514/6.2013-4380

Cited by 4 publications

(2 citation statements)

References 47 publications

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“…Results demonstrate that the thrust increment due to the ground effect decreases as the tilt angle increases when approaching the ground. Barata [17,18] presented a detailed analysis of the flowfield beneath single and multiple impinging jets through a low-velocity crossflow, providing references for the analysis of more complex flowfields of jet-powered VTOL aircraft in practical situations. Birckelbaw et al [19], Saripalli et al [20], Chaderjian et al [21], and Page et al [22] used experimental measurements and numerical simulations to study the jet-induced flowfield of the AV-8B aircraft hovering in ground effect.…”

Section: Introductionmentioning

confidence: 99%

Longitudinal Aerodynamic Characteristics of Ducted Fan Propelled Fixed-Wing VTOL Aircraft Hovering in Ground Effect

2023

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The aerodynamic performances and control characteristics of vertical takeoff and landing aircraft will be significantly affected by the ground effect during takeoff and landing. The longitudinal aerodynamic characteristics and main flow features of a fixed-wing vertical takeoff and landing aircraft hovering in ground effect are investigated in this paper, using Multiple Reference Frame based numerical simulations. The aircraft is propelled by three ducted fans. Results show that the overall morphology of the flow is characterized by a fountain, ground vortex, reingestion, and recirculation. When the thrust distribution between the front and aft ducted fans changes, the flow features change as well. As the aircraft approaches the ground, the ducted fan thrust decreases, the fuselage lift increases, and the total lift first decreases and then increases. The maximum lift increases by 9.6% and the minimum lift decreases by 3.0% compared with that out-of-ground effect. The magnitude of the drag is about 1% of the lift, which has little influence on the aircraft’s performance. The pitching moment gradually changes from the equilibrium state to a significant nose-up moment. The total power consumed increases at a specific rotational speed.

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Section: Introductionmentioning

confidence: 99%

Longitudinal Aerodynamic Characteristics of Ducted Fan Propelled Fixed-Wing VTOL Aircraft Hovering in Ground Effect

2023

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“…Even within an aircraft engine the applicability of the JICF varies greatly owing to the range of desired characteristics of the flow; in the combustion zone(s) of the engine it is desirable to have a jet which penetrates deeply and mixes rapidly with the crossflow so as to promote more efficient combustion processes [5][6][7], whereas low penetration and a suppression of mixing is desirable for utilization in the turbine section for film blade cooling [8,9]. Moreover, implementation in the exhaust nozzle as a method of thrust vectoring or VSTOL would involve delicate tuning of the spread and penetration of the flow for specific control of the thrust [10][11][12]. In all cases, the flowfield is represented by a highly complex and dynamically nonlinear three-dimensional flow system composed of a variety of vortical structures.…”

Section: Introductionmentioning

confidence: 99%

Effects of controlled vortex generation and interactions in transverse jets

et al. 2022

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This experimental study examined the effects of controlled vortex generation and interactions created by axisymmetric excitation of a transverse jet, with a focus on the structural and mixing characteristics of the flow. The excitation consisted of a novel double-pulse forcing waveform applied to the jet, where two distinct temporal square wave pulses were prescribed during a single forcing period. The two distinct pulses produced vortex rings of different strength and celerity, the strategic selection of which promoted vortex ring interactions or collisions in the nearfield to varying degrees. Jet flow conditions corresponding to a transitionally convectively/absolutely unstable upstream shear layer (USL) in the absence of forcing, at a jet-to-crossflow momentum flux ratio of J = 10, and to an absolutely unstable USL at J = 7, were explored for a jet Reynolds number of 1800. Acetone planar laser-induced fluorescence (PLIF) imaging was utilized to quantify the influence of different prescribed temporal waveforms. All forcing conditions enhanced the spread, penetration, and molecular mixing of the jet as compared to the unforced jet, though to differing degrees. Interestingly, when the jet was convectively unstable, forcing which promoted vortex collisions provided the greatest enhancement in molecular mixing, whereas the absolutely unstable jet produced the greatest enhancement in mixing when the vortex rings did not interact, with important implications for optimized jet control.

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Numerical Simulation of Twin Impinging jets in Tandem through a Crossflow

Vieira

Barata

Neves

et al. 2015

53rd AIAA Aerospace Sciences Meeting

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The flow field of ground vortex generated by twin impinging jets in tandem through a crossflow is numerically studied in detail. Numerical simulation and visualization are presented for two turbulent circular jets emerging into a low velocity cross stream, impinging after on a flat surface perpendicular to the geometrical jet nozzle axis. The numerical study is based in experimental studies done early, so all the features of the experimental flow were maintained when the numerical simulation was performed. The Reynolds number used was based on the jet exit conditions of 43,000 to 105,000, a jet to crossflow velocity ratio of 22.5 to 43.8, an impinging height of 20.1 jet diameters and an interject spacing's of S=5D and L=6D. The analysis of the flow was extended to regions and flow conditions for which no measurements have been obtained in last experimental studies, i.e., for velocity ratios of 15 to 90. The numerical results show that for the smallest velocity ratios the jets initially do not mix, but remain together in two layers. Three different types of flow regimes were identify, therefore when VSTOL aircrafts operating in ground vicinity, only the regime with strong impingement on ground and with a formation of a ground vortex is relevant. The numerical results allowed to extend the last experimental studies, and prove that the deflection of the rear jet is due to the competing influences the wake, the shear layer, the downstream wall jet of the first jet and the crossflow. NomenclatureCμ, C1, C2 = turbulent model constants D = diameter of the jet H = impinging height k = turbulent kinetic energy r = radius of cylindrical coordinates Re = Reynolds number S = distance between the jets axis Sϕ = source term U = horizontal velocity, U u  ' (Umean+u') V = vertical velocity, V v  ' (Vmean+v') VR = velocity ratio, Vj/Uo W = transverse ' w W  (Wmean+w') X = horizontal coordinate Y = vertical coordinate Z = transverse coordinate Greek symbols ϕ = transport coefficient ɛ = turbulent kinetic energy dissipation μT = turbulent viscosity ρ = density σk, σε = turbulent Prandtl/Schmidt numbers

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Multiple Jet/Wall/Cross-Wind Interaction Relevant to VSTOL Ground Effects

Cited by 4 publications

References 47 publications

Longitudinal Aerodynamic Characteristics of Ducted Fan Propelled Fixed-Wing VTOL Aircraft Hovering in Ground Effect

Longitudinal Aerodynamic Characteristics of Ducted Fan Propelled Fixed-Wing VTOL Aircraft Hovering in Ground Effect

Effects of controlled vortex generation and interactions in transverse jets

Numerical Simulation of Twin Impinging jets in Tandem through a Crossflow

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