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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 24 Oct 2020 16:29:26 GMT2020-10-24T16:29:26ZMass entrainment-based model for separating flows
http://hdl.handle.net/10985/15235
Mass entrainment-based model for separating flows
STELLA, F.; MAZELLIER, N.; JOSEPH, Pierric; KOURTA, A.
Recent studies have shown that entrainment effectively describes the behavior of natural and forced separating flows developing behind bluff bodies, potentially paving the way to new, scalable separation control strategies. In this perspective, we propose a new interpretative framework for separated flows, based on mass entrainment. The cornerstone of the approach is an original model of the mean flow, representing it as a stationary vortex scaling with the mean recirculation length. We test our model on a set of mean separated topologies, obtained by forcing the flow over a descending ramp with a rack of synthetic jets. Our results show that both the circulation of the vortex and its characteristic size scale simply with the intensity of the backflow (the amount of mass going through the recirculation region). This suggests that the vortex model captures the essential functioning of mean mass entrainment, and that it could be used to model and/or predict the mean properties of separated flows. In addition, we use the vortex model to show that the backflow (an integral quantity) can be estimated from a single wall-pressure measurement (a pointwise quantity). This finding encourages further efforts toward industrially deployable control systems based on mass entrainment.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/152352018-01-01T00:00:00ZSTELLA, F.MAZELLIER, N.JOSEPH, PierricKOURTA, A.Recent studies have shown that entrainment effectively describes the behavior of natural and forced separating flows developing behind bluff bodies, potentially paving the way to new, scalable separation control strategies. In this perspective, we propose a new interpretative framework for separated flows, based on mass entrainment. The cornerstone of the approach is an original model of the mean flow, representing it as a stationary vortex scaling with the mean recirculation length. We test our model on a set of mean separated topologies, obtained by forcing the flow over a descending ramp with a rack of synthetic jets. Our results show that both the circulation of the vortex and its characteristic size scale simply with the intensity of the backflow (the amount of mass going through the recirculation region). This suggests that the vortex model captures the essential functioning of mean mass entrainment, and that it could be used to model and/or predict the mean properties of separated flows. In addition, we use the vortex model to show that the backflow (an integral quantity) can be estimated from a single wall-pressure measurement (a pointwise quantity). This finding encourages further efforts toward industrially deployable control systems based on mass entrainment.Detailed Pressure Measurements During the Transition to Rotating Stall in an Axial Compressor: Influence of the Throttling Process
http://hdl.handle.net/10985/15600
Detailed Pressure Measurements During the Transition to Rotating Stall in an Axial Compressor: Influence of the Throttling Process
MARGALIDA, Gabriel; DAZIN, Antoine; JOSEPH, Pierric; ROUSSETTE, Olivier
This paper presents experimental unsteady pressure measurements gathered on a single stage axial compressor during pre-stall and transition to stall operations. The aim of this study is to analyze the transition from a stable operating point to the fully developed rotating stall regime, and more specifically, the effect of the throttling process on the development of the instabilities. To do so, experiments have been repeated leading the compressor to stall operations with various throttling speed. On one hand, this paper analyses the effect of the throttling speed on the dynamic of the instability development from the first detection of spike type precursors to completely developed rotating stall. On the other hand, a stall warning signal based on the correlation of the instantaneous pressure signal with a reference pressure signal is built. The influence of the location of the pressure transducer used for the warning signal is first analyzed. Then an analysis of the effect of the throttling process on the time between the warning signal and the effective stall development is proposed.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/156002018-01-01T00:00:00ZMARGALIDA, GabrielDAZIN, AntoineJOSEPH, PierricROUSSETTE, OlivierThis paper presents experimental unsteady pressure measurements gathered on a single stage axial compressor during pre-stall and transition to stall operations. The aim of this study is to analyze the transition from a stable operating point to the fully developed rotating stall regime, and more specifically, the effect of the throttling process on the development of the instabilities. To do so, experiments have been repeated leading the compressor to stall operations with various throttling speed. On one hand, this paper analyses the effect of the throttling speed on the dynamic of the instability development from the first detection of spike type precursors to completely developed rotating stall. On the other hand, a stall warning signal based on the correlation of the instantaneous pressure signal with a reference pressure signal is built. The influence of the location of the pressure transducer used for the warning signal is first analyzed. Then an analysis of the effect of the throttling process on the time between the warning signal and the effective stall development is proposed.Comparison and Sensibility Analysis of Warning Parameters for Rotating Stall Detection in an Axial Compressor
http://hdl.handle.net/10985/19179
Comparison and Sensibility Analysis of Warning Parameters for Rotating Stall Detection in an Axial Compressor
MARGALIDA, Gabriel; JOSEPH, Pierric; ROUSSETTE, Olivier; DAZIN, Antoine
The present paper aims at evaluating the surveillance parameters used for early stall warning in axial compressors, and is based on unsteady pressure measurements at the casing of a single stage axial compressor. Two parameters—Correlation and Root Mean Square (RMS)—are first compared and their relative performances discussed. The influence of sensor locations (in both radial and axial directions) is then considered, and the role of the compressor’s geometrical irregularities in the behavior of the indicators is clearly highlighted. The influence of the throttling process is also carefully analyzed. This aspect of the experiment’s process appears to have a non-negligible impact on the stall warning parameters, despite being poorly documented in the literature. This last part of this research work allow us to get a different vision of the alert parameters compared to what is classically done in the literature, as the level of irregularity that is reflected by the magnitude of the parameters appears to be an image of a given flow rate value, and not a clear indicator of the stall inception.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10985/191792020-01-01T00:00:00ZMARGALIDA, GabrielJOSEPH, PierricROUSSETTE, OlivierDAZIN, AntoineThe present paper aims at evaluating the surveillance parameters used for early stall warning in axial compressors, and is based on unsteady pressure measurements at the casing of a single stage axial compressor. Two parameters—Correlation and Root Mean Square (RMS)—are first compared and their relative performances discussed. The influence of sensor locations (in both radial and axial directions) is then considered, and the role of the compressor’s geometrical irregularities in the behavior of the indicators is clearly highlighted. The influence of the throttling process is also carefully analyzed. This aspect of the experiment’s process appears to have a non-negligible impact on the stall warning parameters, despite being poorly documented in the literature. This last part of this research work allow us to get a different vision of the alert parameters compared to what is classically done in the literature, as the level of irregularity that is reflected by the magnitude of the parameters appears to be an image of a given flow rate value, and not a clear indicator of the stall inception.