Transition Detection and Skin Friction Measurements on Rotating Propeller Blades

Abstract

The laminar-to-turbulent transition on high-speed rotating propeller blades is investigated in the present work experimentally. The analysis of limitations for optical skinfriction measurements by the oil-film interferometry, as well as of the results of feasibility experiments in the low-speed wind-tunnel BLSWT of AIRBUS Bremen at propeller rotation rates from 3000 up to 14400 rpm (50-240 Hz) and free-stream flow speeds between 30 and 70 m/s are included. The effects of Reynolds number and of the propeller advance ratio on the transition location and on flow topology are discussed. NomenclatureA variable of the thin-oil-film equation a acceleration a rot shear stress due to the centrifugal-force impact (a rot = ρ oil ω 2 R h/2) c chord length D propeller diameter g acceleration of gravity h film thickness J propeller advance ratio (J = πu ∞ /v rot = u ∞ /(nD)) k thermal conductivity M Mach number n rotation frequency (Hz) n r refraction coefficient P 0 total pressure p static pressure r recovery factor r cr critical onset transition (induced by leading-edge separation) radius r, θ polar coordinates R propeller radius ReReynolds number Re nD propeller Reynolds number (Re nD = (nD 2 )/ν) Re nr locally defined propeller Reynolds number (Re nr = (n4r 2 )/ν) Re nr,cr critical Reynolds number (Re nr,cr = (n4r 2 cr )/ν) t time T absolute temperature, or variable of the thin-oil-film equation T 0 total temperature

Engineering Method to Estimate the Blade Loading of Propellers in Nonuniform Flow

“…As shown in Ref. [73], a more pronounced crossflow exists in the leadingedge region at low advance ratios, which could lead to a crossflow instability and earlier transition on the blade in the experiment than would occur due to Tollmien-Schlichting instability. At a high advance ratio, there is a relatively strong crossflow in the boundary layer toward the trailing edge of the blade.…”

Boundary-layer transition on a rotor blade measured by temperature-sensitive paint, thermal imaging and image derotation

“…Recently, efforts have been focused more toward optical techniques for their high spatial resolution and relative ease of use. Investigations include the detection of boundary-layer transition and flow separation in propellers, helicopter rotors and turbine blades by temperaturesensitive paint (TSP) and pressure-sensitive paint (PSP) (Yorita et al 2012;Klein et al 2013), thermography (Mori et al 2007;Richter and Schülein 2014;Schülein 2014), oil film interferometry (Wadcock et al 1999;Schülein et al 2012) and micro-tuft imaging (Yamauchi et al 1997).…”

Linear Stability Analysis in Rotating Frames for Fan Blade Transition Prediction

“…. ), laminar to turbulent transition has been experimentally studied for decades, see for instance the work of Mc Croskey [2] (for helicopter blades) or the quite recent papers of Schülein et al [3] and Lang et al [4]. Linear stability theory has been applied for simple geometry in rotating frame: disks [5,6], cones [7][8][9] and flat plates [10].…”