Analysis of unsteady pressures induced on a body by a rotor

Bi, Naipei; Leishman, J. Gordon

doi:10.2514/3.46093

Cited by 4 publications

(9 citation statements)

References 16 publications

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“…In particular, the form of presentation of Bi and Leishman 15 may be obtained by fixing attention on a specific point on the airframe and observing the behavior of the pressure at successive times. The present results appear to be consistent with those of Bi and Leishman 15 during the period before vortex-airframe collision in that they indicate a rapid drop in pressure with time as the vortex approaches. The magnitude of the drop is dependent on the relative position of the sensor point and the position of vortex impact as discussed in Ref.…”

Section: Resultssupporting

confidence: 91%

“…This appears to be due to the fact that the negative value of the circulation induces a larger total axial velocity on the airframe than is the case with the positive value of the circulation. It should be noted here that, in the work of Bi and Leishman,15 the results for the pressure distribution are plotted as a function of time at fixed locations on the airframe; in the present case the results have been plotted at a number of locations on the airframe for several times. The precise details of the pressure field in the work of Bi and Leishman 15 depend on the relative position of the pressure sensors on the airframe, and several different types of pressure traces have been identified.…”

Section: Resultsmentioning

confidence: 98%

“…We note here, however, that because of the presence of the downwash, the vortex head will eventually collide with the airframe, although at a substantially different angle than is the case for positive circulation. It should be noted that the initial position of the vortex does not necessarily correspond to that of the experiments of Bi and Leishman 15 ; moreover, the vortex core radius has been fixed as noted earlier. Consequently, quantitative comparison of the present results with the data of Bi and Leishman 14 ' 15 must await future work.…”

Section: Resultsmentioning

confidence: 99%

“…At the last time step shown for a v = 0.05, the head of the vortex is just over one core radius from the cylinder, and again the total dimensionless time of the calculation is t= 0.4. For all of the results shown so far, the sign of the circulation has been assumed to be positive; the experimental situation described X-axis by Bi and Leishman 14 ' 15 and Leishman and Bi 16 may be modeled to a first approximation by merely switching the sign of the circulation. The experimental conditions correspond to a = 1.72 and p = 2.4; the core size has been fixed at 0.1.…”

Section: Resultsmentioning

confidence: 99%

“…They were able to map the vortex position as a function of time, including the period during which a portion of the vortex impacts the cylinder. Bi and Leishman 14 ' 15 and Leishman and Bi 16 the circulation of the filament is of the opposite sign. Both situations will be considered in the present work.…”

Section: Introductionmentioning

confidence: 88%

See 4 more Smart Citations

Model for rotor tip vortex-airframe interaction. I - Theory

Affes

Conlisk

1993

AIAA Journal

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The flowfield generated by a helicopter in flight is extremely complex, and it has been recognized that interactions among components can significantly affect helicopter performance. In the present work a simplified model for the interaction of a rotor tip vortex with the helicopter fuselage is developed. The tip vortex is idealized as a single three-dimensional vortex tube, and the fuselage is modeled as an infinite circular cylinder. The Biot-Savart law is employed to describe the flow induced by the vortex, and the flow is assumed to be inviscid and irrotational outside the core of the vortex. The numerical calculations indicate that a large adverse pressure gradient develops under the vortex on the fuselage causing a rapid drop in the pressure there; large variations in the curvature of the vortex are not observed. Numerical solutions for the vortex position and for the pressure on the airframe are calculated for the case where the vortex is embedded in a three-dimensional steady mean flow; the effect of vortex core size is also investigated. The nature of the initial stages of the breakdown of local axisymmetry of the core of the vortex filament is suggested based on both the numerical and experimental results.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 88%

See 3 more Smart Citations

Model for rotor tip vortex-airframe interaction. I - Theory

Affes

Conlisk

1993

AIAA Journal

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Investigation of rotor tip vortex interactions with a body

Leishman

Crouse

1993

Journal of Aircraft

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Experimental investigation of rotor/lifting surface interactions

Leishman

1994

Journal of Aircraft

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Experiments were conducted to study the aerodynamic interactions between a rotor and a fixed lifting surface. A low aspect ratio rectangular wing was positioned at different locations in a rotor flowfield to simulate the aerodynamic environment encountered by the wings of tilt-rotors or the empennage of helicopters. Steady and unsteady pressure measurements were made on the wing at various chordwise and spanwise stations for different combinations of rotor thrust and advance ratio. Flow visualization was performed using the wide-field shadowgraph method, which helped to identify the locations of the rotor wake relative to the rotor and wing. The results have shown that the lifting surface operates in a highly unsteady three-dimensional flow environment with regions of partial or complete flow separation. In addition, large unsteady loads were induced on the wing by the rotor and its wake. Nomenclature = time-dependent pressure coefficient, Cp = time-averaged pressure coefficient, 100(p -p^/Q.5ptl 2 R 2 C T = rotor thrust coefficient, T/pTr£l 2 R 4 c h = rotor blade chord, m c w = chord of lifting surface, m k = reduced frequency N h = number of rotor blades p = static pressure, N/m 2 R = rotor radius, m r = mondimensional rotor radius T = rotor thrust, N t = time, s Vj = time-averaged induced velocity, m/s V x = freestream velocity, m/s jt, y = wing coordinate system, m x h, y/i ~ rotor coordinate system relative to hub, m a s = rotor shaft angle (tip-path-plane angle), deg fji = advance ratio, VJtlR p = air density, kg/m 3 or = rotor solidity, N b c b /TrR i f f -blade azimuth angle, deg (1 = rotor rotational speed, rad/s a) = circular frequency, rad/s

show abstract

Analysis of unsteady pressures induced on a body by a rotor

Cited by 4 publications

References 16 publications

Model for rotor tip vortex-airframe interaction. I - Theory

Model for rotor tip vortex-airframe interaction. I - Theory

Investigation of rotor tip vortex interactions with a body

Experimental investigation of rotor/lifting surface interactions

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