The von Kármán street behind a circular cylinder: flow control through synthetic jet placed at the rear stagnation point

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Influence of Machine Learning-based active flow control on the turbulent statistics of the flow over a circular cylinder

The aim of the present paper is to investigate the capabilities of Machine Learning (ML) to reduce the aerodynamic drag of a circular cylinder in cross flow, by actively controlling its wake with a synthetic jet

Effects of the stroke length and nozzle-to-plate distance on synthetic jet impingement heat transfer

This study focuses on the combined e ect of the nozzle-to-plate distance andof the stroke length on the cooling performances of impinging synthetic jets.Infrared thermography is used as temperature transducer in conjunction withthe heated thin foil heat transfer sensor to measure time- and phase-averagedconvective heat transfer...The authors wish to thank Mr. G. Sicardi for contributing the realization of the experimental setup. Carlo Salvatore Greco, Andrea Ianiro and Gennaro Cardone have been partially supported by Grant DPI2016-79401-R funded by the Spanish State Research Agency (SRA) and European Regional Development Fund (ERDF).Publicad

Engine Combustion Network "Spray G": Wall heat transfer characterization by infrared thermography

[EN] Nowadays, several efforts are being made to design more efficient, cleaner, and economically accessible engines. Spray-wall interactions are strongly related with the fuel-air mixture and emission formation. As such, they are considered as the most important physical processes in engine research. In the present study, the infrared thermography coupled with an inverse heat transfer data reduction is applied to evaluate the wall heat transfer of an iso-octane spray generated by a multi-hole gasoline direct injector (Spray G) impinging on a heated thin foil. The experimental apparatus includes an Invar foil (50 mu m in thickness) heated by Joule effect and the injector located at 66.66 injector nozzle diameter above the surface. Thermal images of the impinging spray are acquired from the dry side of the foil at several time delays from the start of injection at two different injection pressures (10 and 20 MPa) and two different wall temperatures (373 and 473 K). The experimental data are reduced in the dimensionless form in terms of the spray cooling efficiency zeta, which represents the ratio between the spray cooling heat flux and the heat transfer capability of the fluid, by taking into account the area of impact of the spray. Results show a substantial increment of the heat flux and the spray cooling efficiency by increasing the wall temperature. Also, the increment of the injection pressure has an increasing effect on the area of impact, the heat flux, and the efficiency of the spray for both wall temperatures investigated in the experimental campaign. The spray cone angle and the plume jet axis angle were also estimated from the wall heat flux distribution.The author C. Carvallo thanks the Universitat Politecnica de Valencia for his predoctoral contract (FPI-2019- S1) which is included within the framework of Programa de Apoyo para la Investigacion y Desarrollo(PAID-01-19) and would also like to say thanks for the mobility economical help provided by the program Ayudas para movilidad dentro del Programa para la Formacion de Personal investigador (FPI) de laUPV''.The authors kindly acknowledge Consiglio Nazionale delle Ricerche- STEMS for hardware and technical support. Funding for open access charge: CRUE-Universitat Politecnica deValencia.Zaccara, M.; Carvallo-García, CL.; Montanaro, A.; Gimeno, J.; Allocca, L.; Cardone, G. (2022). Engine Combustion Network "Spray G": Wall heat transfer characterization by infrared thermography. Experimental Thermal and Fluid Science. 142. https://doi.org/10.1016/j.expthermflusci.2022.11082514

Association of kidney disease measures with risk of renal function worsening in patients with type 1 diabetes

Background: Albuminuria has been classically considered a marker of kidney damage progression in diabetic patients and it is routinely assessed to monitor kidney function. However, the role of a mild GFR reduction on the development of stage 653 CKD has been less explored in type 1 diabetes mellitus (T1DM) patients. Aim of the present study was to evaluate the prognostic role of kidney disease measures, namely albuminuria and reduced GFR, on the development of stage 653 CKD in a large cohort of patients affected by T1DM. Methods: A total of 4284 patients affected by T1DM followed-up at 76 diabetes centers participating to the Italian Association of Clinical Diabetologists (Associazione Medici Diabetologi, AMD) initiative constitutes the study population. Urinary albumin excretion (ACR) and estimated GFR (eGFR) were retrieved and analyzed. The incidence of stage 653 CKD (eGFR < 60 mL/min/1.73 m2) or eGFR reduction > 30% from baseline was evaluated. Results: The mean estimated GFR was 98 \ub1 17 mL/min/1.73m2 and the proportion of patients with albuminuria was 15.3% (n = 654) at baseline. About 8% (n = 337) of patients developed one of the two renal endpoints during the 4-year follow-up period. Age, albuminuria (micro or macro) and baseline eGFR < 90 ml/min/m2 were independent risk factors for stage 653 CKD and renal function worsening. When compared to patients with eGFR > 90 ml/min/1.73m2 and normoalbuminuria, those with albuminuria at baseline had a 1.69 greater risk of reaching stage 3 CKD, while patients with mild eGFR reduction (i.e. eGFR between 90 and 60 mL/min/1.73 m2) show a 3.81 greater risk that rose to 8.24 for those patients with albuminuria and mild eGFR reduction at baseline. Conclusions: Albuminuria and eGFR reduction represent independent risk factors for incident stage 653 CKD in T1DM patients. The simultaneous occurrence of reduced eGFR and albuminuria have a synergistic effect on renal function worsening

An Improved Data Reduction Technique for Heat Transfer Measurements in Hypersonic Flows

The re-entry phase is one of the most critical phases in the lifetime of most space missions. When the spacecraft comes into contact with the atmosphere, it is exposed to intense stresses, both mechanical and thermal. The experimental analysis of this phase is therefore of primary importance for the design of spacecrafts and for the dimensioning of thermal protection systems. High enthalpy wind tunnels are designed to simulate the extreme conditions and the complex flow phenomena which develop during re-entry. It is therefore understood how the measurement of heat fluxes is one of the crucial goals of the tests in high enthalpy wind tunnel. The measurement of heat fluxes generally is not made directly but starting from transient temperature measurements on the surface of the model; as such, this is a typical inverse problem and usually implies great sensitivity to measurement errors. The purpose of this work has been to develop a new heat flux sensor to improve the accuracy and stability of the sensors currently used, and it is based on the minimization of the functional of the sum of the mean square errors between temperature transients measured experimentally and temperature transients generated by the numerical solution of the heat conduction equation inside the model, through an optimization process in which the physical parameters h and Taw, on which the temperature rise depends, are estimated. Experimental temperature measurements are performed by means of infrared thermography. To increase the accuracy of thermographic measurements, a new method of optical/geometrical reconstruction has been developed. This method allows to identify with precision the point on the three-dimensional surface of the model on the IR image, and it also permits to take directional emissivity into account to improve the accuracy of the thermographic measurements. In chapter one a general introduction on infrared thermography is given, and the reason why a geometrical reconstruction technique is desirable is made clear. The resection technique, based on the well established pinhole camera model, is subsequently explained in chapter two. The new heat flux sensor is illustrated in chapter three; the limits of the classical thin film, the most widely used heat flux sensor, are highlighted and the mathematical model on which the new sensor is based is explained. A full numerical validation of the sensor and of its limits of applicability has been performed showing that the sensor, in its one-parameter estimation form, can be used in a wide variety of test conditions. The experimental implementation, both of the new geometrical reconstruction technique and of the new heat flux sensor, is illustrated in chapter 4 and 5. The experiments in chapter 4 have been performed in Alta’s HEAT wind tunnel on a double cone model. This is a classical test for which both previous experimental results and numerical simulations are available. It has infact been designed ad hoc for the purpose of code validation within the CAST project. The test illustrated in chapter five has been performed in CIRA’s Scirocco wind tunnel. The purpose of the test was to investigate the shock wave boundary layer interaction on a full-scale model of EXPERT 20deg flap. The materials used in the test are those intended to be used on the capsule itself. The two test cases illustrated in this work have provided a good initial experimental validation for the new heat flux sensor and have shown that it can be successfully used, coupled with the implemented geometrical reconstruction technique, both in test cases designed ad hoc and in simulations of real life models, which do not require any preliminary preparation for the sensor to be used