Experimental and Numerical Investigations of Flow Separation and Transition to Turbulence in an Axisymmetric Diffuser

Hoefener, Lars; Nitsche, W.; Carnarius, Angelo; Thiele, Frank

doi:10.1007/978-3-540-33287-9_27

Cited by 4 publications

(2 citation statements)

References 3 publications

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“…It has been suggested that when the transient growth becomes "sufficiently large", the flow is "mixed" by the nonlinearity, producing turbulence [21,22]. This approach can be roughly summarized by saying that flow systems are extremely sensitive to small perturbations in the initial flow [21][22][23][24]. The advantage of a small disturbance method lies in the fast direct calculation of flow amplitudes compared to their extraction after a time-costly unsteady flow calculation [25], which has been widely used in aerodynamics to solve problems of hypersonic, subsonic or transonic flow over a thin aerofoil and has been verified by experiments [22].…”

Section: Introductionmentioning

confidence: 99%

Sinuosity-Driven Water Pressure Distribution on Slope of Slightly-Curved Riparian Zone: Analytical Solution Based on Small-disturbance Theory and Comparison to Experiments

Xia

Lin

et al. 2016

Water

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A curved riparian zone can create highly complex flow patterns that have a great effect on erosion, pollutant transport, surface water-groundwater exchange and habitat qualities. The small-disturbance theory has been applied to derive the analytical solutions of pressure distributions along a sinusoidal riverbank. Experiments have also been performed to test the hydrodynamic and geomorphic effects on pressure distribution and to verify the applicability of the derived expressions. The derived expressions were simple, accurate and agreed remarkably well with experimental results for the riparian banks with a low degree of curvature. On the contrary, when a riparian bank had a high degree of curvature, these expressions applying the approach of small-disturbance, could not effectively estimate the pressure distributions for a complex bank boundary or complex flow conditions. Moreover, sensitive analysis has indicated that the disturbed pressures along the riparian banks increased with increasing Froude number Fr, as well as the ratio of bank amplitude to wavelength a/λ. However, a/λ has been found to have more significant influence on pressure variation in subcritical flow.

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Section: Introductionmentioning

confidence: 99%

Sinuosity-Driven Water Pressure Distribution on Slope of Slightly-Curved Riparian Zone: Analytical Solution Based on Small-disturbance Theory and Comparison to Experiments

Xia

Lin

et al. 2016

Water

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“…The frequencies related to the 3.75 inch (95 mm) inlet diffuser are found to be in the 2-3.2 Hz range. There are other references ( [73][74][75][76]) which study diffuser generated noise but the conditions in these experiments are far from those tested in this thesis and do not apply. The takeaway is that diffuser noise can be a significant issue given the right conditions.…”

Section: Diffuser Noisementioning

confidence: 95%

A Theoretical and Experimental Investigation on Ejector Acoustics and Ejector Silencer Design

Desmarais¹

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Ejectors are common devices used across many industries, however, they are often plagued by the presence of low frequency pressure pulsations causing both broadband and tonal noise. This thesis presents a theoretical and experimental investigation into the acoustics of an ejector-silencer combination with the emphasis placed on silencer design. More specifically, the noise generated by the jet, the diffuser and natural modes is explained and estimated. The noise generation mechanisms of impingement tones and edgetones are presented but accurate predictions are found to be hard to make. An outline of the experimental facility is followed by the mechanical, acoustical and aerodynamic design details of the approximately 70:1 ejector scale model. A detailed analysis on the primary nozzle control and calibration is presented before beginning an aerodynamic and acoustic characterization of both the ejector and the wind tunnel facility. From experimentation, it is found that the placement of a perforated cone in front of the solid cone is beneficial in reducing the noise generated without overly affecting the entrainment ratio. Other configurations tested tend not to be as acoustically effective or to decrease the entrainment ratio below an acceptable level. Experiments prove that the low frequency noise generated by the ejector is mainly caused by natural mode excitation.iv

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Experimental Investigations of Controlled Transition in a Laminar Separation Bubble at an Axisymmetric Diffuser

Hoefener¹,

Nitsche²

Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM)

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Experimental and Numerical Investigations of Flow Separation and Transition to Turbulence in an Axisymmetric Diffuser

Cited by 4 publications

References 3 publications

Sinuosity-Driven Water Pressure Distribution on Slope of Slightly-Curved Riparian Zone: Analytical Solution Based on Small-disturbance Theory and Comparison to Experiments

Sinuosity-Driven Water Pressure Distribution on Slope of Slightly-Curved Riparian Zone: Analytical Solution Based on Small-disturbance Theory and Comparison to Experiments

A Theoretical and Experimental Investigation on Ejector Acoustics and Ejector Silencer Design

Experimental Investigations of Controlled Transition in a Laminar Separation Bubble at an Axisymmetric Diffuser

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