An analytical and experimental study of inlet ground vortices

Motycka, D.; Walter, William; Müller, Gerald

doi:10.2514/6.1973-1313

Cited by 19 publications

(8 citation statements)

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“…It does not consider vortex mechanisms, which do not require non-zero ambient vorticity and which lead to two or more counter rotating vortex cores such as those described by de Siervi et al [5]. Besides a non-zero ambient vorticity (quantified by the Rossby number V i /WD i where V i is the inlet velocity, D i the internal diameter of the inlet, and W the ambient velocity gradient or shear [6]), these single cored vortices require the distance from inlet to free surface to be lower than a certain threshold, and the velocity of the air between the inlet and the solid surface to be lower than the blow-away velocity. The distance threshold and blow-away velocity are interdependent and are neatly combined in the plots used by several authors [7][8][9], of H /D i versus V i /V o .…”

Section: Vortex Formation Mechanismsmentioning

confidence: 99%

Location of the vortex formation threshold at suction inlets near ground planes by computational fluid dynamics simulation

Jermy

2008

Proceedings of the Institution of Mechanical Engineers, Part G:

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Vortices can develop in the intakes of turbojet and turbofan aero engines during high power operation near solid surfaces such as during takeoff or ground tests. These vortices can stall the compressor and cause significant damage. The factors determining the formation of the vortex include engine thrust, distance from ground, and ambient vorticity. A computational fluid dynamics study was conducted to determine whether these effects could be predicted numerically, and the results were compared to previous wind-tunnel studies. This is the first reported study of numerical predictions of the vortex formation threshold. Two factors, which had not been previously studied either experimentally or numerically, were investigated: the effects of increasing the size of the suction inlet and increasing the thickness of the ground boundary layer. Both were found to encourage vortex formation. The threshold of vortex formation predicted numerically agrees with previous wind-tunnel studies, within the scatter of the experimental data. The numerical results reproduce all trends identified in the experimental studies. The minimum shear required to form a vortex was found, lying between 0.001 and 0.05/s (Rossby number of the order of 105).

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Section: Vortex Formation Mechanismsmentioning

confidence: 99%

Location of the vortex formation threshold at suction inlets near ground planes by computational fluid dynamics simulation

Jermy

2008

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…These have included small-scale experiments (e.g. Klein 1957 ;Glenny 1970;Motycka, Walter & Muller 1973;Motycka & Walter 1975;Bissinger & Braun 1974), full-scale tests with engines (Rodert & Garrett 1955 ;Motycka 1976), panelmethod calculations of the velocity field associated with a potential vortex and inlet combination (Colehour & Farquhar 1971), and two-dimensional free-streamline potential-flow models of an inlet near a ground plane (Newman & Atassi 1980). A discussion of these various studies is given by Viguier (1980), but we can summarize the main conclusions presented in the existing literature as follows.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of inlet-vortex formation

et al. 1982

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An experimental and theoretical study is presented of the inlet-vortex (or ground-vortex) phenomenon. The experiments were carried out in a water tunnel using hydrogen-bubble flow visualization. The theoretical study is based on a secondary-flow approach in which vortex filaments in a (weak) shear flow are viewed as convected (and deformed) by a three-dimensional irrotational primary flow; the latter being calculated numerically using a three-dimensional panel method. Two basic mechanisms of inlet-vortex generation are identified. The first of these, which has been alluded to qualitatively by other investigators, is the amplification of ambient (i.e. far-upstream) vorticity as the vortex lines are stretched and drawn into the inlet. Quantitative calculations have been carried out to illustrate the central features connected with this amplification. I n contrast with what has been supposed, however, there is another mechanism of inlet-vortex formation, which does not appear to have been recognized previously and which does not require the presence of ambient vorticity. It is thus shown that an inlet vortex can arise in an (upstream) irrotational flow, for an inlet in cross wind. In this situation, the vortex is accompanied by a variation in circulation along the length of the inlet. The ratio of inlet velocity to upstream veIocity is an important parameter for both mechanisms.

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“…A group of researchers from MIT [13] discussed a mechanism of formation of these vortices. Ground vortices can, however, be formed also in the absence of any ambient flow [14][15][16][17]. Yet, in both cases the flow generated by the sucked air is similar, which has been confirmed experimentally (De Siervi et al, [18]) and computationally.…”

Section: Ground Vortexmentioning

confidence: 60%

Aero-Engines Intake: A Review and Case Study

El-Sayed¹

2016

J Robot Mech Eng Resr

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This paper presents an aerodynamic review for intakes of aero-engines. Classification of different types is introduced for both subsonic and supersonic aircrafts. Important parameters influencing intake performance like pressure recovery and spillage drag are discussed. In addition, crucial performance issues such as the angle of attack, ground vortex, swirl flow, noise propagation and icing are presented. These are critical issues which are carefully considered by airframe rather than engine manufacturers. Intake icing may be extremely dangerous and leads to drastic decrease in air mass flow and consequently aircraft propulsion.Calculation of intake performance is explained. The effect of intake performance on the whole engine performance is highlighted. Numerical analyses for present and previous researches are explained and critical parameters are identified.Finally, a case study resembling the intake of a high bypass ratio turbofan engine (in close similarity to that of GE CF-6 Turbofan Engine) is numerically analysed using the commercial code "ESI-CFD 2010" is thoroughly described and analysed. This paper is the first of a series of research work that will cover several R & D activities in HBPR and future EBPR turbofan intakes.

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An analytical and experimental study of inlet ground vortices

Cited by 19 publications

References 0 publications

Location of the vortex formation threshold at suction inlets near ground planes by computational fluid dynamics simulation

Location of the vortex formation threshold at suction inlets near ground planes by computational fluid dynamics simulation

Mechanisms of inlet-vortex formation

Aero-Engines Intake: A Review and Case Study

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