Effects of Streamwise Pressure Gradient on Turbulent Spot Development

Abstract

A pressure distribution representative of a controlled diffusion compressor blade suction surface is imposed on a flat plate. Boundary layer transition in this situation is investigated by triggering a wave packet, which evolves into a turbulent spot. The development from wave packet to turbulent spot is observed and the interactions of the turbulent spot with the ongoing natural transition and the ensuing turbulent boundary layer are examined. Under this steeply diffusing pressure distribution, strong amplification of primary instabilities prevails. Breakdown to turbulence is instigated near the centerline and propagates transversely along the wave packet until the turbulent region dominates. An extensive calmed region is present behind the spot, which persists well into the surrounding turbulent layer. Celerities of spot leading and trailing edges are presented, as is the spanwise spreading half-angle. Corresponding measurements for spots under a wide range of imposed pressure gradients are compiled and the present results are compared with those of other authors. Resulting correlations for spot propagation parameters are provided for use in computational modeling of the transition region under variable pressure gradients.

Computational Simulation of Dynamic Stall on the NLR 7301 Airfoil

“…In this publication, the model of Gostelow et al (1996) was introduced, which permits the calculation of the transition length as a function of pressure gradient and free-stream turbulence level. This method continuously adjusts the turbulent spot growth in response to changes of the local pressure gradient.…”

Transition Models for Turbomachinery Boundary Layer Flows: A Review

“…These parameters can be obtained from correlations. For example, detailed correlations for α, σ, and N were constructed by Gostelow et al [67] and Solomon et al [68]. The factor Nσ/U in (1) has the dimension 1/m 2 .…”

“…If the transition is complete both R NAT and R BP terms are put to zero again and thus the v 2 -equation becomes equivalent to the k-equation. It means that the transitional and fully turbulent flow behaviour is prescribed by the Equations (66) and (67). The k-equation (65) is only needed to construct some of the model functions.…”

Transonic flutter computations for a 2D supercritical wing

“…In this publication the model of Gostelow et al (1996) was introduced which permits the calculation of the transition length as a function of pressure gradient and free-stream turbulence level. This method continuously adjusts the turbulent s p o t g r o wth in response to changes of the local pressure gradient.…”

“…In the present study, the turbulence models of Baldwin and Lomax (1978), of Baldwin and Barth (1990), and of Spalart and Allmaras (1992) are used to model turbulent o w regions. Each turbulence model is coupled with the transition model of Gostelow et al (1996). Numerical results are compared with experimental measurements of Schewe and Deyhle (1996) and Knipfer et al (1998) to validate the predictive capability of the code for unsteady transonic ow.…”