Experimental investigations on steady wake effects in a high-lift turbine cascade

Compressible Direct Numerical Simulation of Low-Pressure Turbines: Part I — Methodology

“…Separation bubbles and the type and location of laminar-turbulent transition are sensitive to upstream disturbances, including background turbulence in the main stream and wakes from the upstream rows [3,4]. As the profile losses depend strongly on the state of the boundary layers on the blades [5], it is crucial that the boundary layer states can be predicted accurately in order for LPT design to match stringent performance and weight requirements. Although Reynolds Averaged Navier-Stokes (RANS) incorporating the latest transition models appear to achieve good agreement with experiments at low Reynolds numbers in terms of pressure coefficient and transition onset, these models are often unable to provide accurate results in terms of total pressure losses [6] in the wide design space generally required for changing operating conditions of LPT.…”

The Current State of High-Fidelity Simulations for Main Gas Path Turbomachinery Components and Their Industrial Impact

“…Therefore, as the profile losses depend strongly on the state of the boundary layers on the blades [43], it is crucial that the boundary layer states, and the presence of a local boundary layer separation, can be predicted accurately in order for LPT design to match stringent performance and weight requirements. The above characteristics pose considerable challenges for turbulence modelling approaches that need to specifically address boundary layer transition of the by-pass and separated flow type, while this class of internal flows do not experience natural boundary layer transition due to the concerted action of high background turbulence and discrete wakes and pressure waves.…”

Aero-thermal flow characterization downstream of an NGV cascade by five-hole probe and filtered Rayleigh scattering measurements

“…In utilizing a molecular absorption line as notch filter, laser stray light can be strongly attenuated, while portions of Rayleigh scattering pass through the filter and form the FRS signal (Miles et al, 2001). The FSM-FRS signal intensity scattered from a small volume filled with gas molecules of a single species, which is accumulated by the detector at sensor element ij, can be described as (Forkey, 1996;Doll et al, 2014)…”

“…The experimental characterization of aero-thermal flow properties in such configurations typically relies on well-proven probe based technology such as pneumatic multi-hole devices, hot-wire probes or thermocouples (see e. g. Heinke et al (2004); Qureshi et al (2012); Luque et al (2015)). Due to their robustness and reliability, pneumatic multi-hole probes are widely used in applications related to turbomachinery.…”

“…In this regard the filtered Rayleigh scattering technique (FRS) (Miles and Lempert, 1990) may prove a valuable alternative to existing approaches. Extended by the method of frequency scanning (FSM-FRS) (Forkey, 1996;Doll et al, 2014), the technique is capable to acquire timeaveraged pressure, temperature and velocity maps simultaneously. FRS relies on molecular scattering only, no seeding particles have to be added to the flow.…”