Trapped vortex cell for aeronautical applications: flow analysis through PIV and Wavelet transform tools

Results of the application of a trapped vortex cell to an airfoil with the aim of improving the aerodynamic performances are presented for two complementary experiments arranged at CIRA and at Politecnico di Torino. In the CIRA experiments, PIV measurements on a simplified configuration were carried out to characterize the trapped vortical structure and its effect on the separating flow downstream of the cell. In the experimental investigation at Politecnico di Torino, static pressure distributions were measured around a complete airfoil model, to yield lift and pitching moment coefficients. Wake surveys were also carried out to measure the drag. To study the unsteady phenomena inside the cavity pressure fluctuations signals were also investigated using Kulite sensors. In both experiments, the angle of attack of the airfoil and the Reynolds number were varied. It is shown that the flow inside the cell is highly unsteady with significant shedding of flow structures downstream. This phenomenon results in a large region of separated flow, in higher drag and lower lift. By contrast, the cell flow is considerably stabilized and regularized by applying distributed suction over the cell wall. As a result, the flow downstream of the cell reattaches and lower drag and larger lift are observed

Friction drag measurements in turbulent wall flows

Results of an experimental investigation devoted to the assessment of methodologies aimed at the friction drag measurement in turbulent wall flows are presented. Two techniques for local measurements have been developed. Namely, different versions of the velocity profile method have been used for a turbulent boundary layer developing on a flat plate. The oil flow interferometer has been arranged and results related with measurements performed in a fully developed turbulent channel flow and in the turbulent boundary layer are presented. Moreover a balance based on a floating-buoyancy system finalized to the integral measurement of the friction force acting on the flat plate is presented. The results of the three techniques are compared considering as a reference a well assessed empirical law. Good level of measurement accuracy using the balance has been evidenced highlighting the capability of the balance or the characterization of micro-grooved surfaces addressed for friction drag reduction applications

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

Drag reduction on a simplified 3D bluff body

A complete flow control over road vehicles is difficult to achieve because of different phenomena occurring in flow evolution, i.e. the wheel rotation and ground effect deeply influence the flow features. In spite of this, the problem can be approached following different strategies considering both passive and active flow control techniques. The flow around bluff body road vehicle exhibits a massive separation region and as a consequence the drag is mainly due to pressure losses. The total aerodynamic drag of such bodies can be roughly split into three main contributions. The rolling tire account for up to 25-30% whereas the rear part gives rise to 40-45% of the total drag. The remaining is due to the underbody flow and interferences. The wake structure is greatly influenced by the rear geometry of the body that determines the pressure field in this region. As showed by Ahmed [1] and by Iuso [2] the afterbody geometry plays a key role for the drag contributions and also for drag reduction when passive solutions are adopted. In cases where a square back rear part is imposed by different requirement such as internal space in commercial vehicles, passive or active control techniques can be used to achieve drag reduction. Passive and active vortex generators as those used by Aider et al [3] and piezoelectric vortex generators as proposed by Orazi et al. [4] can be adopted. Also synthetic jets located in the body rear part as done by Park et al. [5] or continuous blowing slots as done by Rouméas et al. [6] have been also used. Since a favorable energy budget is an essential requirement for a real application of active flow control the technique efficiency is of crucial importance. From this point of view very low energy absorption devices or direct drag alleviation are promising possible solutions. In the present study a simplified car geometry has been chosen as a reference shape and a wake control system has been designed based on continuous or synthetic jets. The results of preliminary CFD analysis focused on the investigation of natural and controlled flow behavior are presented here. Moreover, this study has allowed the design of the physical experiment in the wind tunnel

INVESTIGATION OF A NOVEL VTOL AIRCRAFT CONCEPT FOR OPERATIONS IN URBAN AREAS

Experimental investigation on a novel VTOL aircraft named “Anuloid” has been carried out to assess its aerodynamics performances. The study focused on two main aspects: the analysis of the Coanda effect on the 1:20 scaled model without cross-flow and the aerodynamic characterization of the body, performed on the 1:5 scaled model in a large wind tunnel. The first task included the study of the Coanda effect, both in hovering and in ground effect conditions. Basic and modified geometries for the fan duct outlet were also investigated and the influence of the Reynolds number was evaluated. A simplified preliminary analysis on the effectiveness of the maneuverability surfaces was finally conducted. Results evidenced that the Coanda effect is present only for the modified geometries of the outlet section, whereas the basic geometry gives rise to early flow separation. The wind tunnel tests highlighted that the aircraft has poor lift and high drag in normal flight condition, i.e. when α<0°. In addition to this, the pitching moment is negative in the whole range of incidences tested, resulting in longitudinal instability. Finally, pressure distributions revealed massive flow separation on both lower and upper surfaces that gives rise to a very complex unsteady and tridimensional flow field configuration around the body

Flow separation control applied to simplified car

A flow control technique aimed to the drag reduction has been applied to a 3D simplified car model. In order to control the near wake region, four continuous jets are disposed at the periphery of the body. The control performance are previously analyzed through a preliminary CFD study on a 1:1 scale model. The preliminary experimental investigation in condition of wind off has been also considered on a 3D printed model at a 1:8.75 scale in order to assess the whole chain of measurements. This investigation involves the direct measurement of drag force, the pressure distribution on the surface of the model and the wall pressure fluctuations. Different requirements led to a particular mounting configuration for the model. Primary calibration of the load cell and the pressure fluctuations sensors has been carried ou

Flow separation control applied to simplified car

A flow control technique aimed to the drag reduction has been applied to a 3D simplified car model. In order to control the near wake region, four continuous jets are disposed at the periphery of the body. The control performance are previously analyzed through a preliminary CFD study on a 1:1 scale model. The preliminary experimental investigation in condition of wind off has been also considered on a 3D printed model at a 1:8.75 scale in order to assess the whole chain of measurements. This investigation involves the direct measurement of drag force, the pressure distribution on the surface of the model and the wall pressure fluctuations. Different requirements led to a particular mounting configuration for the model. Primary calibration of the load cell and the pressure fluctuations sensors has been carried ou

Single-port versus conventional multiport access prophylactic laparoscopic bilateral salpingo-oophorectomy in high-risk patients for ovarian cancer: A comparison of surgical outcomes

Bilateral salpingo-oophorectomy (BSO) in carriers of BRCA1 and BRCA2 mutations is widely recommended as part of a risk-reduction strategy for ovarian or breast cancer due to an underlying genetic predisposition. BSO is also performed as a therapeutic intervention for patients with hormone-positive premenopausal breast cancer. BSO may be performed via a minimally invasive approach with the use of three to four 5 mm and/or 12 mm ports inserted through a skin incision. To further reduce the morbidity associated with the placement of multiple port sites and to improve cosmetic outcomes, single-port laparoscopy has been developed with a single access point from the umbilicus. The purpose of this study was to evaluate the surgical outcomes associated with reducing the risks of salpingo-oophorectomy performed in a single port, while comparing multiport laparoscopy in women with a high risk for ovarian cancer. Single-port laparoscopy\u2013BSO is feasible and safe, with favorable surgical and cosmetic outcomes when compared to conventional laparoscopy

Endometrial ablation: first- vs. second-generation techniques

Endometrial ablation is a procedure that surgically destroys (ablates) the lining of the uterus (endometrium). The goal of endometrial ablation is to reduce menstrual flow. In some women, menstrual flow may stop completely. In some cases, endometrial ablation may be an alternative to hysterectomy. There are several techniques used to perform endometrial ablation, including electrical or electrocautery ablation, in which an electric current travels through a wire loop or rollerball is applied to the endometrial lining to cauterize the tissue; hydrothermal ablation, in which heated fluid is pumped into the uterus and destroys the endometrial lining via high temperatures; balloon therapy ablation, in which a balloon at the end of a catheter is inserted into the uterus and filled with fluid, which is then heated to the point that the endometrial tissues are eroded away; radiofrequency ablation in which a triangular mesh electrode is expanded to fill the uterine cavity, at which point the electrode delivers an electrical current and destroys the endometrial lining; cryoablation (freezing), in which a probe uses extremely low temperatures to freeze and destroy the endometrial tissues; and microwave ablation, in which microwave energy is delivered through a slender probe inserted into the uterus and destroys the endometrial lining