Computational and experimental investigation of the flow structure and vortex dynamics in the wake of a Formula 1 tire

The flowfield around a 60% scale stationary Formula 1 tire in contact with the ground in a closed wind tunnel was examined experimentally in order to assess the accuracy of different turbulence modeling techniques. The results of steady RANS and Large Eddy Simulation (LES) were compared with PIV data, which was obtained within the same project. The far wake structure behind the wheel was dominated by two strong counter-rotating vortices. The locations of the vortex cores, extracted from the LES and PIV data as well as computed using different RANS models, showed that the LES predictions are closest to the PIV vortex cores. All turbulence models were able to accurately predict the region of strong downward velocity between the vortex cores in the center-plane of the tire, but discrepancies arose when velocity profiles were compared close to the inboard and outboard edges of the tire. These discrepancies could be due to the sensitivity of the CFD solution to the tire shoulder profile, which may not exactly match the experimental profile. In the near wake region directly behind the contact patch of the tire, contour plots of in-plane velocity were compared for all three datasets. The LES simulation again matched well with the PIV data

In-Hole Measurements of Flow Inside Fan-Shaped Film Cooling Holes and Downstream Effects

The study of low-speed jets into crossflow is critical to the performance of gas turbines. Film cooling is a method to maintain manageable blade temperatures in turbine sections while increasing turbine inlet temperatures and turbine efficiencies. Initially, cooling holes were cylindrical. Film cooling jets from these discrete round holes were found to be very susceptible to jet liftoff, which reduces surface effectiveness. Shaped holes have become prominent for improved coolant coverage. Fan-shaped holes are the most common design and have shown good improvement over round holes. However, fan-shaped holes introduce additional parameters to the already complex task of modeling cooling effectiveness. Studies of these flows range in hole lengths from those found in actual turbine blades to very long holes with fully developed flow. The flow within the holes themselves is difficult to study as there is limited optical access. However, the flow within the holes has a strong effect on the resulting properties of the jet. This study presents velocity and vorticity fields measured using high-resolution magnetic resonance velocimetry (MRV) to study three different fan-shaped hole geometries at two blowing ratios. Because MRV does not require line of sight, it provides otherwise hard-to-obtain experimental data of the flow within the film cooling hole in addition to the mainflow measurements. By allowing measurement within the cooling hole, MRV shows how a poor choice of diffuser start point and angle can be detrimental to film cooling if overall hole length and cooling flow velocity are not properly accounted for in the design. The downstream effect of these choices on the jet height and counter-rotating vortex pair is also observed

Antimicrobial Agents and Urinary Tract Infections

Urinary Tract Infections (UTIs); second-ranking infectious diseases are regarded as a significant global health care problem. The UTIs annually cost tens of millions of dollars for governments worldwide. The main reason behind these costs is incorrect or indefinite treatment. There are a wide range of gram-negative and grampositive bacteria which may cause UTIs in males and females, children and adults. Among gram-negative bacteria, some members of Enterobacteriaceae such as Escherichia coli (E.coli) strains have significant contribution in UTIs. Uropathogenic E.coli (UPEC) strains are recognized as typical bacterial agents for UTIs. Thus, sharp and accurate diagnostic tools are needed for detection and identification of the microbial causative agents of UTIs. In parallel with the utilization of suitable diagnostic methods-to reduce the number of UTIs, effective and definite treatment procedures are needed. Therefore, the prescription of accurate, specific and effective antibiotics and drugs may lead to a definite treatment. However, there are many cases related to UTIs which can be relapsed. Due to a diversity of opportunistic and pathogenic causative microbial agents of UTIs, the treatment procedures should be achieved by the related antimicrobial agents. In this review, common and effective antimicrobial agents which are often prescribed for UTIs caused by UPEC will be discussed. Moreover, we will have a sharp look at their (antimicrobials) molecular treatment mechanisms.</jats:sec

Film Cooling Effectiveness Improvements Using a Non-Diffusing Oval Hole

The need for improvements in film cooling effectiveness over traditional cylindrical film cooling holes has led to varied shaped hole and sister hole designs of increasing complexity. This paper presents a simpler shaped-hole design which shows improved film cooling effectiveness over both cylindrical holes and diffusing fan-shaped holes without the geometric complexity of the latter. Magnetic resonance imaging measurement techniques are used to reveal the coupled 3D velocity and coolant mixing from film cooling holes which are of a constant oval cross-section as opposed to round. The oval shaped hole yielded an area-averaged adiabatic effectiveness twice that of the diffusing fan-shaped hole tested. Three component mean velocity measurements within the channel and cooling hole showed the flow features and vorticity fields which explain the improved performance of the oval shaped hole. As compared to the round hole, the oval hole leads to a more complex vorticity field which reduces the strength of the main counter-rotating vortex pair. The counter-rotating vortex pair acts to lift the coolant away from the turbine blade surface and thus strongly reduces the film cooling effectiveness. The weaker vortices allow coolant to stay closer to the blade surface and to remain relatively unmixed with the main flow over a longer distance. Thus, the oval-shaped film cooling hole provides a simpler solution for improving film cooling effectiveness beyond circular hole and diffusing hole designs.</jats:p

Magnetic Resonance Imaging Studies of Flow and Mixing for Single-Hole Film Cooling

Magnetic resonance imaging (MRI) measurement techniques are used to reveal the coupled 3D velocity and coolant concentration fields for a single film cooling hole with L/D of 4, ejection angle of 60°, and blowing ratios of 0.5 and 1. The jet exits into a boundary layer with momentum thickness of 0.1D. Magnetic resonance velocimetry (MRV) measures 3 component mean velocity everywhere within the channel, cooling hole, and feed plenum. Magnetic resonance concentration (MRC) provides the coolant concentration distribution which is directly analogous to film cooling effectiveness. The coupled velocity and concentration show that high velocity ratios lead to a detached jet which lowers effectiveness. Vorticity from the feed hole creates a streamwise oriented counter rotating vortex pair which lifts the coolant stream from the surface and sweeps in main channel flow inducing a kidney-shape to the coolant jet cross-section. Without the need for optical access, MRV allows study of the flow inside the feed hole including the entrance separation and secondary flows. Cross-stream feeding of the cooling hole shows added spanwise asymmetry at the hole entrance, but this asymmetry is significantly reduced moving up the hole.</jats:p

Nouvelles minéralisations dans le massif du Sheyvardagh, Azerbaidjan, Iran

Bariand Pierre, Ziegler V., Issakhanian V., Vassigh H. Nouvelles minéralisations dans le massif du Sheyvardagh, Azerbaidjan, Iran. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 84, 3, 1961. pp. 326-327

Magnetic Resonance Imaging Techniques for Measuring Film Cooling Flow Velocity and Effectiveness

Film cooling of gas turbine engine components directly influences the efficiency and lifetime of the engine. Prediction of the film cooling surface effectiveness remains a problem area for engine designers. Magnetic Resonance Imaging (MRI) measurements of the surface film cooling effectiveness can be made using the analogy between temperature and passive scalar concentration in which the concentration of scalar marked cooling fluid is measured as it mixes with the main flow. The present work specifically addresses refinements to MR imaging techniques needed to accurately measure the concentration of a scalar contaminant at a flow-bounding surface. Anecdotal data are presented from experiments in which a single film jet exits into the boundary layer on one wall of a square channel. Data are presented for hole angles α = 30° and 60° and blowing ratios BR = 0.5 and 1.0. The Reynolds number of the main channel based on hydraulic diameter and bulk velocity is 400,000 and the jet Reynolds number at BR = 1.0 is 5300.</jats:p