Near-On-Design Unsteadiness in a Supersonic Low-Boom Inlet

Candon, Sean; Loth, Eric; Rybalko, Michael

doi:10.2514/1.b35603

Cited by 4 publications

(11 citation statements)

References 22 publications

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“…To avoid this issue, the Nichols-Nelson approach [27] was selected due to its versatility and reduced sensitivity to grid construction compared to other hybrid RANS/LES methods. Additionally, the NicholsNelson has produced promising results in previous computational studies of the current supersonic inlet [15,16,20,28].…”

Section: B Hybrid Rans/les Methodologymentioning

confidence: 91%

“…The hybrid RANS/LES results presented in the current study employed a 16.7-million-point grid, which was demonstrated to provide grid-independent results for all time-averaged features of this inlet flowfield [16]. The 3-D computational flow domain was divided into 20 separate zones across a 10 deg axisymmetric span for parallel computation and included the flowfield from upstream of the centerbody spike tip to downstream to the mass flow plug.…”

Section: B Hybrid Rans/les Methodologymentioning

confidence: 99%

“…Figure 2a shows the inlet portion of the grid from just upstream of the spike tip down to the AIP (downstream region and mass flow plug not shown). Grids were generated in Gridgen, and resolution and domain length studies were performed [15,16]. Grid points were placed in the radial direction by following the hyperbolic tangent function near the centerbody and cowl surfaces in order to better resolve the boundary layers, as seen in Fig.…”

Section: B Hybrid Rans/les Methodologymentioning

confidence: 99%

“…These dynamics were compared to results with a computational domain extended to include the downstream low-speed diffuser and the mass flow plug. The study by Candon et al [16] indicated a substantial increase in shock motion in the extended computational domain case compared with the fixed downstream pressure case, suggesting the presence of streamwise propagating waves originating in the low-speed diffuser. However, a detailed understanding of these waves (i.e., characterization in terms of speed and amplitude as a function of streamwise position and fundamental description in terms of fluid dynamic evolution) has not yet been previously published.…”

mentioning

confidence: 96%

“…However, at a "near-design" MFR of 0.955, this inlet produced a substantially more unsteady shock, which may have been related to the little-buzz phenomenon as described by Fisher et al [1]. To computationally investigate the mechanism for these near-design oscillations seen in the low-boom inlet, Candon et al [16] employed a fixed backpressure condition established at the exit plane of the high-speed subsonic diffuser, i.e., at the aerodynamic interface plane (AIP). These dynamics were compared to results with a computational domain extended to include the downstream low-speed diffuser and the mass flow plug.…”

mentioning

confidence: 98%

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Acoustically Induced Shock Oscillations in a Low-Boom Inlet

et al. 2016

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Experimental unsteady centerbody surface pressures measured in a low-boom inlet have been analyzed and compared with an unsteady computational flow approach. The experimental dataset was gathered at the 8 × 6 ft supersonic wind tunnel at the NASA John H. Glenn Research Center in 2010. The axisymmetric external compression inlet considered herein featured a relaxed isentropic centerbody compression spike followed by a short subsonic diffuser to the aerodynamic interface plane. The axisymmetric inlet computational domain comprised a 10 deg sector, starting with the freestream inflow region, and included both the internal flowpath up to the mass flow plug and the external flow past the sharp-edged cowl for external flow. The selected inlet test conditions were based on a 1.67 freestream Mach number at a zero angle of attack with a near-design spillage rate of approximately 4%. Both experiments and simulations revealed temporal shifts between pressure peaks at different streamwise locations, indicating upstream-running compression waves that moved at acoustic speeds. These waves became amplified near the geometric throat and produced streamwise oscillations of the external normal shock. The simulations also revealed a second smaller shock on the centerbody at the geometric throat, for which the complex dynamics suggested an opportunity for further study. Nomenclature a = speed of sound D = diameter L = length N = number of unsteady pressure readings p = pressure r = radial direction coordinate t = time u = streamwise velocity component x = streamwise direction coordinate y = normal direction coordinate z = spanwise direction coordinate τ = timescale Subscripts AC = acoustic AIP = aerodynamic interface plane CB = centerbody cowl = inner cowl diff = averaged over low-speed diffuser end = wave end peak = local peak RMS = root mean square sh = shock start = wave start tip = spike tip ∞ = freestream condition Superscripts 0 = fluctuation = normalized

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