End-Stage Boundary Layer Transition Models for Engineering Calculations

Abstract

The paper presents some recent new data on the combined eflects of pressure gradient and9eestream turbulence level on the onset and length of tho latter stages of the boundary layer transition process. Generalized correlations for the transition length Reynolds number are developed from considerations of the non-dimensional turbulent spot formation rate. The optimized correlation is built into a popular linear combination integral computer code to predict the growth of the transitional boundary layer in a number of practical engineeringflows. NOTATION

Heat transfer measurements on an intermediate-pressure nozzle guide vane tested in a rotating annular turbine facility, and the modifying effects of a non-uniform inlet temperature profile

“…Many authors have studied the effect of increased freestream turbulence on the heat transfer rate at the vane surface, and generally speaking such increases have been shown to promote earlier transition from a laminar to a turbulent boundary layer, an increase in the rate of production of turbulent spots being the agent of transition, and to augment the heat transfer rate in both the laminar and the turbulent boundary layer. Fraser et al [5] and Abu-Ghannam and Shaw [6] both give particularly comprehensive reviews of the eld. Universal correlations-even for a relatively limited class of vane geometry-for predicting both the point of transitional onset and the length of transition have so far evaded investigators.…”

Transition Length Prediction for Flows With Rapidly Changing Pressure Gradients

“…(6) is not valid for flows which have a transition onset point in a region of favorable pressure gradient and some modification is required to cover this case. This has been done here on the basis of correlations presented by Fraser et al (1994)…”

“…The latter problems have been ascribed to an unexpectedly large influence of local pressure gradient on turbulent spot propagation, as revealed by recent experiments of Gostelow et al (1995). The authors have used these results, together with correlations for spot inception rates from Gostelow et al (1994a) and Fraser et al (1994), to produce a modified Chen-Thyson model for the intermittency distribution in flows with rapidly changing pressure gradient.…”

An algorithm for the aerodynamic analysis of rotating blades using a weak viscous-inviscid interaction method

“…A number o f factors affect the transition behaviour in a shear layer. They are, as described by Roberts and Yaras (2005b), the Reynolds number, freestream turbulence intensity (B la ir (1982); V olino & Hultgren (2001)), turbulence length scale (Johnson & Ercan (1997); Roberts & Yaras (2003)), streamwise pressure gradients (Fraser et al (1994); Gostelow & Blunden (1989); and Sharma et al (1982)), streamline curvature (1994)), and surface roughness (Cummings & Bragg (1996), Pinson & Wang (1997), and Roberts & Yaras (2005a)). These factors affect the transition mode, the transition inception and completion locations, and the fraction o f tim e the flo w is turbulent in the flo w during transition.…”

“…Emmons showed that the inception, convection, and spreading rates o f turbulent spots determine the length o f the transition zone. Experimental studies by Fraser et al (1994) and Gostelow et al (1994), among others, show that the rate o f turbulent spot production is affected by the freestream turbulence intensity and streamwise pressure gradient. In addition, the w ork o f Pinson & Wang (1997) (1957), w ith fo llo w in g adjustments by Chen & Tyson (1971), Savill (1993a;1993b), Solomon et al (1995), Gostelow et al (1996) the effects o f the streamwise pressure gradient on the boundary layer.…”