The present work aims at investigating a particular impinging jet configuration throughout a comprehensive experimental approach. A preheated air jet at 130 • C issues a fully developed circular pipe at Reynolds number 60,000 and discharges in the laboratory room to impinge a flat plate located 3 diameters downstream. The description of the velocity field and the complete Reynolds stress tensor is provided by stereoscopic particle image velocimetry (S-PIV) and laser Doppler velocimetry (LDV) measurements. For the first time, data are reported for the mean and fluctuating temperature of an impinging jet configuration with the help of cold-wire thermometry (CWT) measurements. The heat transfer distribution on the impinged plate is determined through an inverse method based on infrared thermography measurements on the rear face of the plate. The agreement between SPIV and LDV measurements is shown excellent over the whole flow field. The measured Nusselt number distribution exhibits a secondary maximum at r/D = 2, as observed in previous experiments for short impinging distances. Flow dynamics is characterized through a spectral analysis of time-resolved measurements while flow topology features are identified through coherent structure detection based on SPIV spatiallyresolved instantaneous velocity fields. This analysis shows that the jet column mode, associated with a Strouhal number of 0.4, plays a key role in the primary structure dynamics.

This paper reports on the investigation of an original impinging jet configuration through a wall-resolved largeeddy simulation. The heated jet issues from a fully developed pipe flow at temperature of 130°C and a Reynolds number based on the bulk velocity of 60000. The impinged plate is located three diameters downstream of the pipe exit. The CFD results have been validated against a specifically-created experimental database (Grenson et al., 2016). The overall statistical fields are well retrieved by the simulation both in the free jet and the wall jet region. In particular, the secondary maximum at the radial location = r D / 2 in the Nusselt number distribution is well predicted by the simulation. The underlying mechanisms from which the secondary maximum originates has been investigated. This analysis revealed that small-scale hot spots of strong convective heat transfer coefficient are responsible for the emergence of this secondary maximum. It is shown that the hot spots can be associated either to local unsteady "separation" of the flow or streaks-like structures above the impinging plate.

No abstract

Porous bleed systems are a common technique to control shock-boundary layer interactions and/or supersonic boundary layer. However, the influence of various design parameters is still unknown. Even though bleed models are required to minimize the costs of the design process, they often do not include parameter effects. In the present study, the effect of the hole diameter, the porosity level, and the length-to-diameter ratio are investigated by means of three-dimensional RANS simulations. The findings show an influence of the hole diameter on both flow control and efficiency of the porous bleed. A significant impact of the porosity level on the effective control of the shock-boundary layer interaction is found. In contrast, the length-to-diameter ratio does not influence the effective control but affects the efficiency of the system.

Purpose This paper aims to report the attempts for predicting “on-the-fly” flow distortion in the engine entrance plane of a highly curved S-duct from wall static pressure measurements. Such a technology would be indispensable to trigger active flow control devices to mitigate the intense flow separations which occur in specific flight conditions. Design/methodology/approach Evaluation of different reconstruction algorithms is performed on the basis of data extracted from a Zonal Detached Eddy Simulation (ZDES) of a well-documented S-Duct (Garnier et al., AIAA J., 2015). Contrary to RANS methods, such a hybrid approach makes unsteady distortions available, which are necessary information for reconstruction algorithm assessment. Findings The best reconstruction accuracy is obtained with the artificial neural network (ANN) but the improvement compared to the classical linear stochastic estimation (LSE) is minor. The different inlet distortion coefficients are not reconstructed with the same accuracy. KA2 coefficient is finally identified as the more suited for activation of the control device. Originality/value LSE and its second-order variant (quadratic stochastic estimation [QSE]) are applied for reconstructing instantaneous stagnation pressure in the flow field. The potential improvement of an algorithm based on an ANN is also evaluated. The statistical link between the wall sensors and 40-Kulite rake sensors are carefully discussed and the accuracy of the reconstruction of the most used distortion coefficients (DC60, RDI, CDI and KA2) is quantified for each estimation technique.

The renewed interest for Supersonic Civil Transport on one side and the environmental challenges that whole aeronautics sector will have to overcome in the next decades calls for an holistic evaluation of the environmental impacts of a possible reintroduction of supersonic flights after Concorde retirement in 2003. In this perspective, a research effort has been initiated by ONERA to investigate the lowest levels of environmental impacts that can be expected by a new generation of civil supersonic aircraft. This paper presents the set-up and verification of different models and of a methodological design approach combining conceptual and preliminary aircraft design capabilities. This approach is intended to design a supersonic civil transport aircraft concepts that can serve to evaluate the minimum levels of environmental impacts of new supersonic aircraft integrating state-of-the-art technologies in terms of sonic boom, take-off noise and emissions.

This paper presents a comprehensive study of an impinging jet configuration [1], which has been selected for its high Reynolds number Re D = 60,000, small nozzle-to-plate distance H/D = 3 and temperature difference between the heated jet and the ambient. First, the experiments are described and analysed, then numerical simulations (DNS, LES, ZDES and RANS) are assessed to evaluate the resolution level required to capture the salient features of this configuration.