56,221 research outputs found
Application of HRN EN ISO 3834-3 norm i BRAVAR-MONT company
No full textU radu je analizirana norma HRN EN 3834 općenito, uz naznaku na HRN EN ISO 3834-
3 koji se odnosi na poduzeće Bravar-mont d.o.o. i izradu konstrukcije prema njoj. Norma određuje
točno specificiran redoslijed svih procedura koje se moraju obaviti prije, tijekom i nakon
zavarivanja kako bi dobili kvalitetan proizvod. Glavni čimbenik navedenog je kvalificirano,
provjereno i odgovorno osoblje, koje mora pratiti sve naputke izdane od norme da bi završni
proizvod bio unutar zahtjeva ugovora, ali i same norme.The paper analyzes HRN EN 3834 norm with an indication on HRN EN ISO 3834-3 norm
relating to Bravar-mont company and production of constructions according to that norm.
This norm specifies the exact order of all procedures that must be performed before,
during and after welding to obtain a quality product. The main factor is qualified, verified and
responsible staff, who must follow all instructions issued by the norm in order for the finished
product to be within the requirements of the contract, but also within the norm
A Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
Near Wall PIV-Measurements on the Windward Slope of a Hill
No full textThe turbulent flow over periodic hills was measured near to the wall, using planar Particle-Image-Velocimetry (PIV) at high spatial resolution. Our focus is on the near wall turbulence structure on the windward slope of the hill. For large-eddy simulation (LES) we suspect that, if this was not predicted accurately, it affects the prediction of the velocity profiles over the hill crest which in turn will affect the recirculation length downstream of the hill. Regarding the time averaged velocities, we were able to resolve the linear viscous region of the boundary layer. The velocity distribution and also the Reynolds stress does not comply with the law of the wall as it is valid for a turbulent boundary layer at equilibrium
Etika u promatranju sa sudjelovanjem : Izazovi i dileme u radu s osjetljivim populacijama
No full textOvaj završni rad bavi se etičkim dilemama i strategijama koje istraživači koriste u primjeni istraživačke metode promatranja sa sudjelovanjem, posebice u radu s osjetljivim skupinama. Promatranje sa sudjelovanjem je kvalitativna istraživačka metoda prikupljanja podataka u kojoj istraživač postaje dio skupine koju istražuje i uz sudjelovanje detaljno zapaža ponašanja i odnose u skupini. Iako vrlo korisna metoda, često se primjenjuje u radu s ranjivim skupinama poput djece, osoba s invaliditetom, žrtvama nasilja i sličnih osjetljivih skupina što otvara niz etičkih dilema. Rad opisuje najčešće dileme na koje istraživači nailaze u primjeni promatranja sa sudjelovanjem poput prikrivenog promatranja, informiranog pristanka, privatnosti i kontrole prikupljenih informacija, rizika i štete za sudionike istraživanja, njihovo iskorištavanje i odnos istraživača prema skupini kao i ostale posebne situacije. Na primjerima iz literature posebno objašnjava etičke dileme u radu s osjetljivim populacijama poput žena koje kockaju. Osim etičkih dilema, u radu su navedene i odgovarajuće strategije kojima se istraživači koriste u promatranju sa sudjelovanjem, s fokusom na ranjive skupine. Osiguravanje informiranog pristanka, korištenje pseudonima i izmjena podataka radi očuvanja anonimnosti i zaštite sudionika, upravljanje prikrivenim identitetom istraživača i povjerljivim informacijama, strategije su kojima istraživači rješavaju navedene etičke dileme. Zaključuje se kako metoda promatranja sa sudjelovanjem zahtijeva visoku razinu profesionalnosti kod istraživača budući da cilj istraživanja i prikupljanja vrijednih informacija mora uvijek biti u svrhu očuvanja dobrobiti sudionika, a da potencijalni rizici za skupinu koju se istražuje moraju biti minimalni
Energy dissipation and flux laws for unsteady turbulence
No full textDirect Numerical Simulations of spatially periodic unsteady turbulence show that the high Reynolds number scalings of the instantaneous energy dissipation rate and interscale energy flux at intermediate wavenumbers are qualitatively different from the well-known cornerstone scalings of equilibrium turbulence where and are time-dependent rms velocity and integral length-scales. Instead, they both scale as where and are length and velocity scales characterizing initial/overall unsteady turbulence conditions
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Real-space Manifestations of Bottlenecks in Turbulence Spectra
No full textAn energy-spectrum bottleneck, a bump in the turbulence spectrum between the inertial and dissipation ranges, is shown to occur in the non-turbulent, one-dimensional, hyperviscous Burgers equation and found to be the Fourier-space signature of oscillations in the real-space velocity, which are explained by boundary-layer-expansion techniques. Pseudospectral simulations are used to show that such oscillations occur in velocity correlation functions in one- and three-dimensional hyperviscous hydrodynamical equations that display genuine turbulence
Wreck removal in Croatian law and in the Nairobi International convention on removal of wrecks
No full textAutor konstatira i kritizira nepostojanje distinkcije između instituta spašavanja i instituta vađenja potonulih stvari u Pomorskom zakoniku iz 2004. U drugom dijelu rada opsežno izlaže temeljne postavke onvog međunarodnog dokumenta, Međunarodne konvencije o uklanjanju podrtina, donesene u Nairobiju 2007. godineIn the first part of the paper the author criticizes the decision of the creators of the 2004 Maritime Code to eliminate wreck removal from the Code as an autonomous institute and subject it to the provisions governing salvage. Such decision has far-reaching consequences and is not in the tradition of the Croatian maritime tradition. In the second part the author analyses the provisions of the 2007 Nairobi International convention on the removal of wrecks
Braid Entropy of Faraday Waves driven 2D Turbulence
No full textWe report new experimental results that use tools from braid theory to characterize two-dimensional turbulent flows driven by Faraday waves. The average topological length of the material fluid lines is found to grow exponentially with time. It allows us to compute the braid’s topological entropy SBraid. We show that SBraid increases as the square root of the turbulence kinetic energy E ~ u^2, where u^2 is the horizontal velocity variance . At long times, the PDFs of Lbraid are positively skewed and present strong exponential tails
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