Vortical structure in the wake of a transverse jet

Structural features resulting from the interaction of a turbulent jet issuing transversely into a uniform stream are described with the help of flow visualization and hot-wire anemometry. Jet-to-crossflow velocity ratios from 2 to 10 were investigated at crossflow Reynolds numbers from 3800 to 11400. In particular, the origin and formation of the vortices in the wake are described and shown to be fundamentally different from the well-known phenomenon of vortex shedding from solid bluff bodies. The flow around a transverse jet does not separate from the jet and does not shed vorticity into the wake. Instead, the wake vortices have their origins in the laminar boundary layer of the wall from which the jet issues. It is argued that the closed flow around the jet imposes an adverse pressure gradient on the wall, on the downstream lateral sides of the jet, provoking 'separation events’ in the wall boundary layer on each side. These result in eruptions of boundary-layer fluid and formation of wake vortices that are convected downstream. The measured wake Strouhal frequencies, which depend on the jet-crossflow velocity ratio, match the measured frequencies of the separation events. The wake structure is most orderly and the corresponding wake Strouhal number (0.13) is most sharply defined for velocity ratios near the value 4. Measured wake profiles show deficits of both momentum and total pressure

Wind towers - design of flange ring connection

Today, wind power is second largest available renewable resource of energy, with 870 TW (terawatts). Large wind farms, with hundreds of wind towers are big opportunity for steel production industry. Designers and manufacturers of wind towers pay special attention on every single detail, always looking for some new solutions, trying to reduce price of wind towers. Some of the most interesting design and manufacturing details are connections used to assemble sections of tubular steel towers supporting wind turbins. There is traditional and actually more used flange ring connection and on the other side, as a new proposal which is used more and more, friction connection. In this paper theoretic basis of design of flange ring connection of wind towers is give

Design of class 4 cross section in axial compression according to EUROCODE 3

In this paper theoretic basis of design of class 4 cross section in axial compression according to EN1993-1-5 is given. Design procedure is given as an flow chart and ilustrated with an worked example. Plate buckling is treated localy and globaly through the concept of effective cross sections. Interaction between plate-like and column-like behaviour of panels is carried out thought buckling reduction factors and final effective area of cross section

Uporedna analiza proračuna ekscentrično pritisnutih elemenata prema Evrokodu 3 i JUS-u

Evrokod 3 daje dva ravnopravna postupka proračuna interakcionih koeficijenata za proračun ekscentrično pritisnutih elemenata konstantnog jednodelnog poprečnog preseka. U ovom radu je data uporedna analiza rezultata proračuna ekscentrično pritisnutih elemenata prema Evrokodu 3 i važećem domaćem standardu. Interakcioni koeficijenti su sračunati prema alternativnim informativnim aneksima A i B, Evrokoda 3. Analizirani su rezultati šest numeričkih primera u kojima su varirane dužine elementa i vrednosti aksijalne sile pritiska

Opšta metoda za proračun bočnog i torzionog izvijanja elemenata čeličnih konstukcija

Beside standard procedure for stability design of structural elements in compression, bending, as well in compression and bending, Eurocode 3 offers posibility to make these calculations using finit element method through general method for lateral and lateral torsional buckling of structural elements. In this paper general method for lateral and lateral torsional buckling of structural elements is presented. Also, there is numerical example whose results are compared with results of Eurocodes alternative procedures and JUS

Primer primene akustičke izolacije u čeličnoj konstrukciji sinemapleksa ''STER'' u Beogradu

Modern public buildings, such as multiplex cinemas, along with application of state of the art sound effects brings high acoustic isolation demands. Cinemas are often a part of building complexes such as shopping malls with subjects that produce serious level of noise and vibrations. Usage of modern materials, with specific dynamic characteristics, as a base for supports gives a wide range of possibilities in controlling the amount of noise and vibrations transferred to the structure. This paper gives an example of usage of acoustic pads in steel structure of “Ster” cinemaplex in Belgrade

Nosivost na smicanje anker ploče sa grupom elastičnih čep moždanika

Joint between concrete structural member and steel or timber structural member can be realized with anchor plate which is being embeded in concrete structure during the erection. Anchor plate can be connected with concrete structural member using any standard anchor, with anchors made of ribbed reinforcement or, with group of standard head stud connectors as it is described in this paper. This paper also describes a procedure for calculation of anchor plate shear capacity with connection to concrete member realized with group of head stud connector

Novi koncept proračuna aluminijumskih konstrukcija prema Evrokodu

This paper describes the basic philosophy of the design aluminium structures according to the new European standard EN1999: Design of aluminium structures, Part 1-1: General structural rules. Comparison of the properties of aluminium as a material for structural elements is given in relation to the carbon steel. Special attention is given to the buckling effect in compressed parts of the cross section as well as the thermal effects of welding process, resulting in reduction of the mechanical properties in the heat-affected zones. These effects are illustrated through a brief numerical example

The IL-17F/IL-17RC Axis Promotes Respiratory Allergy in the Proximal Airways

Summary The interleukin 17 (IL-17) cytokine and receptor family is central to antimicrobial resistance and inflammation in the lung. Mice lacking IL-17A, IL-17F, or the IL-17RA subunit were compared with wild-type mice for susceptibility to airway inflammation in models of infection and allergy. Signaling through IL-17RA was required for efficient microbial clearance and prevention of allergy; in the absence of IL-17RA, signaling through IL-17RC on epithelial cells, predominantly by IL-17F, significantly exacerbated lower airway Aspergillus or Pseudomonas infection and allergic airway inflammation. In contrast, following infection with the upper respiratory pathogen Staphylococcus aureus , the IL-17F/IL-17RC axis mediated protection. Thus, IL-17A and IL-17F exert distinct biological effects during pulmonary infection; the IL-17F/IL-17RC signaling axis has the potential to significantly worsen pathogen-associated inflammation of the lower respiratory tract in particular, and should be investigated further as a therapeutic target for treating pathological inflammation in the lung