Effects of Wall Shape on Flow Regimes and Performance in Straight, Two-Dimensional Diffusers

Carlson, J. J.; Johnston, J. P.; Sagi, C. J.

doi:10.1115/1.3609545

Cited by 32 publications

(13 citation statements)

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“…The 1149 performance of a straight two-dimensional diffuser had been studied and analyzed by Reneau et al [21]. The effect of wall shape on flow regimes and performance had been studied in a straight two-dimensional diffuser by Carlson et al [22]. The profile of a plane diffuser with given upstream width and length had been optimized to obtain the maximum static pressure rise by Cabuk and Modi [23].…”

Section: Literature Surveymentioning

confidence: 98%

An evolutionary optimization of diffuser shapes based on CFD simulations

Ghosh

Pratihar

Maiti

et al. 2010

Numerical Methods in Fluids

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SUMMARYAn efficient and robust algorithm is presented for the optimum design of plane symmetric diffusers handling incompressible turbulent flow. The indigenously developed algorithm uses the CFD software: Fluent for the hydrodynamic analysis and employs a genetic algorithm (GA) for optimization. For a prescribed inlet velocity and outlet pressure, pressure recovery coefficient C * p (the objective function) is estimated computationally for various design options. The CFD software and the GA have been combined in a monolithic platform for a fully automated operation using some special control commands. Based on the developed algorithm, an extensive exercise has been made to optimize the diffuser shape. Different methodologies have been adopted to create a large number of design options. Interestingly, not much difference has been noted in the optimum C * p values obtained through different approaches. However, in all the approaches, a better design has been obtained through a proper selection of the number of design variables. Finally, the effect of diffuser length on the optimum shape has also been studied.

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Section: Literature Surveymentioning

confidence: 98%

An evolutionary optimization of diffuser shapes based on CFD simulations

Ghosh

Pratihar

Maiti

et al. 2010

Numerical Methods in Fluids

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“…When flow separation occurs in a symmetric diverging duct having straight walls, the pressures on the two walls may differ due to flow instability ͑Ashjaee and Johnston, 1980;Carlson et al, 1967͒, resulting in a skewed flow. Also, flow from a centrally located slit into a larger rectangular duct is known to move toward one side of the downstream duct ͓Tsui and Wang, 1995;Cherdron et al, 1978; this phenomena is also mentioned in Shadle et al ͑1991͒ for an eccentric glottal orifice͔.…”

Section: Flow Behavior Within and Downstream Of A Diverging Ductmentioning

confidence: 99%

Intraglottal pressure profiles for a symmetric and oblique glottis with a divergence angle of 10 degrees

Scherer

Shinwari

Witt

et al. 2001

The Journal of the Acoustical Society of America

240

243

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Human phonation does not always involve symmetric motions of the two vocal folds. Asymmetric motions can create slanted or oblique glottal angles. This study reports intraglottal pressure profiles for a Plexiglas model of the larynx with a glottis having a 10-degree divergence angle and either a symmetric orientation or an oblique angle of 15 degrees. For the oblique glottis, one side was divergent and the other convergent. The vocal fold surfaces had 14 pressure taps. The minimal glottal diameter was held constant at 0.04 cm. Results indicated that for either the symmetric or oblique case, the pressure profiles were different on the two sides of the glottis except for the symmetric geometry for a transglottal pressure of 3 cm H2O. For the symmetric case, flow separation created lower pressures on the side where the flow stayed attached to the wall, and the largest pressure differences between the two sides of the channel were 5%-6% of the transglottal pressure. For the oblique case, pressures were lower on the divergent glottal side near the glottal entry and exit, and the cross-channel pressures at the glottis entrance differed by 27% of the transglottal pressure. The empirical pressure distributions were supported by computational results. The observed aerodynamic asymmetries could be a factor contributing to normal jitter values and differences in vocal fold phasing.

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“…Relationships were deduced between these flow regimes and the diffuser characteristics [27] while, concurrently, a simple geometry parameterization gave room for more efficient designs [28].…”

Section: Two-dimensional Straight Diffusermentioning

confidence: 99%

Design Optimization of a Two-Dimensional Subsonic Engine Air Intake

2006

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A novel geometry modeling technique is defined for the optimization of pressure recovery through a twodimensional subsonic diffuser based on that of a Formula One race car airbox. The airbox design procedure involves considering the expansion of the flow entering the airbox coupled with a bend through 90 deg. Both of these features are discussed separately in terms of parameterization approaches before the most suitable techniques are united in the final optimization study producing an airbox harboring strong local geometric control and with a set of design variables compact enough to retain optimizer efficiency. A global Krig response surface model is employed to support our optimization studies, comprising design of experiments and updates based upon the expected improvement to the objective function followed by a local exploration in a reduced area of the design space. We find that we can efficiently converge to an optimum airbox design. The geometry modeling technique discussed allows for potentially radical designs with high pressure recoveries. Nomenclature A = two-dimensional diffuser width, m a = Hicks-Henne bump amplitude, m C p = static pressure coefficient E = two-dimensional diffuser total expansion ratio, A e =A in Ex = local expansion ratio, Ax=A in f = objective function k = number of dimensions N = diffuser axial length, m n = number of observed responses p = mass-averaged static pressure, Pa R = correlation between two sample points r = vector of correlations T = dimensionless width factor of Hicks-Henne bump U = mass-averaged inlet velocity, m=s x = untried point x p = normalized distance of Hicks-Henne bump peak along duct centerline from duct entry, x p 2 0; 1 = wall-contouring parameter ij = Kronecker delta where ij 1 if i j and ij 0 if i ≠ j , p, = Kriging hyperparameters = mean = maximum likelihood estimator of the mean = fluid density, kg=m 3 2 = variancê 2 = maximum likelihood estimator of the variance Subscripts in = diffuser inlet location e = diffuser exit location measured at the engine filter location

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Effects of Wall Shape on Flow Regimes and Performance in Straight, Two-Dimensional Diffusers

Cited by 32 publications

References 0 publications

An evolutionary optimization of diffuser shapes based on CFD simulations

An evolutionary optimization of diffuser shapes based on CFD simulations

Intraglottal pressure profiles for a symmetric and oblique glottis with a divergence angle of 10 degrees

Design Optimization of a Two-Dimensional Subsonic Engine Air Intake

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