Boundary layer receptivity to freestream vortical disturbances

Lin, Nay; Stuckert, Greg; Herbert, Thorwald

doi:10.2514/6.1995-772

Cited by 2 publications

(3 citation statements)

References 9 publications

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“…A quantitative comparison of the experimental results with those of theory requires that the boundary-layer signature of the free-stream disturbance used in the calculation matches that measured in the experiment (figure 8). The convected array of vortices introduced by Rogler & Reshotko (1975) and used by Crouch (1994a, b) and Lin et al (1995) in their receptivity calculations has quite a different signature in the boundary layer than that measured in this experiment. The array of vortices produces a much higher fluctuation gradient close to the edge of the boundary layer (see Crouch 1994b, figure 2).…”

Section: Discussion and Comparison With Theorycontrasting

confidence: 49%

“…Detailed reviews are given in Choudhari & Streett (1994) and Crouch (1994a). A comparison between finite Reynolds number results and results of calculations using the parabolized stability equations made by Crouch & Bertolotti (1992) for acoustic receptivity and by Lin, Stuckert & Herbert (1995) for vortical receptivity, showed the two methods to be in agreement. A further comparison between the results of finite Reynolds number calculations and those of a direct numerical simulation of acoustic receptivity at localized surface suction made by Crouch & Spalart (1995) also showed good agreement.…”

Section: Introductionmentioning

confidence: 92%

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Local boundary-layer receptivity to a convected free-stream disturbance

Dietz

1999

J. Fluid Mech.

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An investigation of the local receptivity of a Blasius boundary layer to a harmonic vortical disturbance is presented as a step towards understanding boundary-layer receptivity to free-stream turbulence. Although there has been solid experimental verification of the linear theory describing acoustic receptivity of boundary layers, this was the first experimental verification of the mechanism behind local receptivity to a convected disturbance. The harmonic wake from a vibrating ribbon positioned upstream of a flat plate provided the free-stream disturbance. Two-dimensional roughness elements on the surface of the plate acted as a local receptivity site. Hot-wire measurements in the boundary layer downstream of the roughness confirmed the generation of Tollmien–Schlichting (TS) instability waves by an outer-layer interaction between the long-wavelength convected disturbance and the short-scale mean-flow distortion due to the roughness. The characteristics of the instability waves were carefully measured to ensure that their behaviour was correctly modelled by linear stability theory. This theory was then used to determine the immeasurably small initial wave amplitudes resulting from the receptivity process, from wave amplitudes measured downstream. Tests were performed to determine the range of validity of the linear assumptions made in current receptivity theories. Experimental data obtained in the linear regime were then compared to theoretical results of other authors by expressing the experimental data in the form of an efficiency function which is independent of the free-stream amplitude, roughness height and roughness geometry. Reasonable agreement between the experimental and theoretical efficiency functions was obtained over a range of frequencies and Reynolds numbers.

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Section: Discussion and Comparison With Theorycontrasting

confidence: 49%

Section: Introductionmentioning

confidence: 92%

Local boundary-layer receptivity to a convected free-stream disturbance

Dietz

1999

J. Fluid Mech.

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“…32-34,8, and 35-38͒. The work of Crouch,37 and a later study by Lin, Stuckert and Herbert, 38 modeled the scattering of the two-dimensional vortex-array pattern of Rogler and Reshotko 20 ͑our mode ''A''͒ by small amplitude surface undulation to study the effect of free-stream turbulence on the growth of Tollmien-Schlichting waves. The scattering process is needed to convert the phase speed of the free-stream disturbances into a value close to that of the TS waves, as shown by Ruban 32 and Goldstein 33 in their study of acoustic waves and localized surface irregularities.…”

Section: Receptivity Of Unsteady Disturbancesmentioning

confidence: 99%

Response of the Blasius boundary layer to free-stream vorticity

Bertolotti¹

1997

Physics of Fluids

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Two-and three-dimensional vortical modes that solve the linearized Navier-Stokes equations in the free stream are used in the present theory to represent some of the key features of low-level turbulence. Excluding the leading edge, the effect of these modes on the Blasius boundary layer is investigated using the parabolized stability equations ͑PSE͒. When the vortical modes are steady, or have low frequencies, the PSE analysis is started at a location x 0 from the solution to a new set of ordinary differential equations. This solution is able to satisfy the linearized Navier-Stokes equations in a rather large neighborhood of x 0 . When the vortical modes have frequencies equal to those of unstable Tollmien-Schlichting waves, the scattering of the vortical modes by surface undulation produces only a weak response in the boundary layer, in agreement with other investigations. However, when steady and low-frequency vortical modes are considered, the analysis yields results that successfully reproduce a number of the experimental measurements of Kendall ͓AIAA Paper 90-1504 ͑1990͔͒ on streaky structures, known as Klebanoff modes, that cause a periodic spanwise modulation of the streamwise velocity.

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Boundary layer receptivity to freestream vortical disturbances

Cited by 2 publications

References 9 publications

Local boundary-layer receptivity to a convected free-stream disturbance

Local boundary-layer receptivity to a convected free-stream disturbance

Response of the Blasius boundary layer to free-stream vorticity

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