Unsteady crossflow separation location measurements on a maneuvering 6:1 prolate spheroid

Wetzel, Todd G.

doi:10.2514/3.14086

Cited by 6 publications

(15 citation statements)

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“…The minima in the wall shear are taken as separation locations following Wetzel and Simpson. 1 Experimental data 30 are also presented for comparison. Accurate prediction of surface pressure gradient, for which the overall turbulent ow should be well resolved, leads to accurate prediction of strength and direction of cross ow.…”

Section: Results and Comparison Datamentioning

confidence: 99%

“…The separations are delayed in the pitch-up maneuver case due to the history effect, which is an effect dependent on the true total path the particle has traversed. 1 Pressure coef cients, C p D p= 1 2 ½U 2 0 , at various axial locations, x D 0:11, 0.44, 0.77, and 0.90, are presented in Fig. 6 for increasing pitch angles.…”

Section: Results and Comparison Datamentioning

confidence: 99%

“…Three parameters, that is, grid size, timestep size, and pseudo-time iteration number, with three different levels, that is, ne, medium, and coarse, are considered for normal force coef cient, C N D normal force= 1 2 ½U 2 0 L 2 at t D 5:5, that is, the halfway point of the pitch-up maneuver. C N is normal to the ow direction and believed to be a global quantity that is sensitive to the parameters selected.…”

Section: Results and Comparison Datamentioning

confidence: 99%

“…It resembles the submarine maneuver 1 that was modeled after data for a full-scale submarine during the initial transient portion of a turning maneuver and is suitable for the objectivesof the present study.The spheroidis pitched about its center, which is consistentwith the experimentalsetup. 1 Figure 1 shows the schematic of the pitch-up maneuver. Computational conditions are set following the experimental conditions, except for the sting at the rear of the model, wind-tunnel walls, and the slight backward motion of the model caused by limitations of plunge-pitch motion coordination in the experimental facility.…”

Section: Model Problem and Mathematical Formulationmentioning

confidence: 99%

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Numerical Simulation of Unsteady Turbulent Flow Around Maneuvering Prolate Spheroid

Rhee

Hino

2002

AIAA Journal

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A three-dimensional Reynolds averaged Navier-Stokes method for unsteady turbulent ow around a maneuvering vehicle was developed and applied to a model problem concerning an extreme case of submarine maneuvers. A body force term is added in the momentum equations to take into account the inertial motion in the body-xed coordinate system. The Spalart and Allmaras turbulence model is employed for turbulence closure. An arti cial compressibility is introduced into the continuity equation for velocity-pressure coupling. The governing equations are discretized by second-order accurate nite volume method in space and second-order accurate backward scheme in time. The computational results are analyzed with global and local quantities and validated by comparison with experimental data. Overall, the present method performs quite well in predicting the unsteady ow phenomena associated with a maneuvering prolate spheroid, and the results compare well with available experimental data. Comparisons of steady and unsteady ow results show lags in the ow eld development and delays of ow separation in unsteady ow cases, indicating that unsteady ow phenomena cannot be well understood by simple extensions of steady or quasi-steady computational results. Comparisons with experimental data reveal that the isotropic eddy viscosity turbulence model used does not adequately resolve the vortical ow in separated regions.

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Section: Results and Comparison Datamentioning

confidence: 99%

Section: Results and Comparison Datamentioning

confidence: 99%

Section: Results and Comparison Datamentioning

confidence: 99%

Section: Model Problem and Mathematical Formulationmentioning

confidence: 99%

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Numerical Simulation of Unsteady Turbulent Flow Around Maneuvering Prolate Spheroid

Rhee

Hino

2002

AIAA Journal

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“…Plots of this data are shown in Figure 1.2. Wetzel [28,29] measured steady and unsteady skin friction values over the spheroid surface and mapped the separation lines shown in Figure 1.2.…”

Section: Prolate Spheroid Flowmentioning

confidence: 99%

Development and Testing of the Virginia Tech Doppler Global Velocimeter

Fussell¹

2003

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Large-eddy simulation of tripping effects on the flow over a 6 : 1 prolate spheroid at angle of attack

2023

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Large-eddy simulation is used to simulate the flow around a 6 : 1 prolate spheroid at $10^\circ$ and $20^\circ$ angles of attack, and Reynolds number $4.2 \times 10^6$ . Flows with and without trip are compared to understand the relative effect of the trip on the state of the boundary layer and separation. For the tripped case, the geometry of the trip is resolved to better predict its effect on the downstream flow. The simulations employ overset grids that allow adequate resolution of the trips without significant increase in the overall computational cost. Results suggest that while the trip accelerates transition to turbulence at $10^\circ$ , it does not induce a fully developed turbulent boundary layer as intended at $20^\circ$ . Rather, the influence of the trip is localized, and the near-wall flow converges towards a solution similar to that of the non-tripped case upstream of separation. This is due to two distinct phenomena: directly downstream of the trip, favourable pressure gradient and streamline curvature effects suppress the disturbance on the windward side. Further along the spheroid, the boundary layer receives a small fraction of the initial perturbation due to spanwise and wall-normal streamline curvatures inducing a secondary flow that advects the low-momentum trip wake to the leeward side. The locations of transition and separation are insensitive to the presence of the trip. The simulation results are used to construct a regime map that identifies different regions characterized by distinct boundary layer properties and flow features. The present results underscore the difficulty associated with tripping smooth bodies at angle of attack, and the importance of accounting for transition in simulations of such flows, even on tripped geometries.

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Unsteady crossflow separation location measurements on a maneuvering 6:1 prolate spheroid

Cited by 6 publications

References 0 publications

Numerical Simulation of Unsteady Turbulent Flow Around Maneuvering Prolate Spheroid

Numerical Simulation of Unsteady Turbulent Flow Around Maneuvering Prolate Spheroid

Development and Testing of the Virginia Tech Doppler Global Velocimeter

Large-eddy simulation of tripping effects on the flow over a 6 : 1 prolate spheroid at angle of attack

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