Flow visualisation and modelling of solid soap extrusion

Ram extrusion of a solid granular soap was studied using three geometrically identical but differently-scaled extruders. The experimental design revealed deviation from the Benbow and Bridgwater (1993) extrusion model due to nonideal, scale-dependent effects. Typically these effects, linked to the shear rate in the extruder, are absorbed into the model's material pseudo-properties. The data were able to be represented using the Basterfield et al. (2005) model for extrusion flow which does include a shear rate as a variable. Flow visualisation in conjunction with fluid dynamics-based simulations showed, however, that the assumptions underlying the Basterfield et al. model are not appropriate for soap extrusion, despite the good agreement of the model with the experimental extrusion data. This highlights a need for care in interpretation of extrusion data, in that the limited information gathered about any given experiment, typically just the extrusion pressure, can lead to the generation of spurious parameters if the wrong model is applied.This work was funded by Ceratizit GmbH Austria and Sandvik Hyperion U

Amphitheatre stage roofing made of wooden – based materials

Import 26/02/2015Návrh zastřešení pódia v areálu bývalého letního kina v Boršicích. Vypracovány tři varianty z materiálů na bázi dřeva. Vybraná varianta je podrobně zpracována včetně přípojů, návrhu ztužení a založení. Byl také vypracován návrh montáže vybrané varianty.Static design of roofing a stage in former summer cinema area in Borsice. Three concepts were designed of wood-based materials. The detailed design of one concept was made including connections, bracings and foundations. Assembly procedure was also designed.221 - Katedra konstrukcívýborn

Uticaj sile držanja i stanja površina na duboko izvlačenje „tailored blanks”

During the deep drawing of tailored blanks, tribological conditions make an influence on a forming process in a very complex way. The blank holding force and contact surfaces state of tools and materials are important parameters, which the final parameters of a deep drawing process depend on. In the paper the results of experimental analysis of deep drawing of tailored blanks and basic blanks they were made of, were shown. The influences of the different blank holding forces and different tribologic conditions were investigated, using the main deformations distributions and the deep drawing force change during the process.Publishe

THE EFFECTIVE NOTCH STRESS APPROACH FOR FATIGUE ASSESSMENT OF WELDED TUBULAR JOINTS

Ph.DDOCTOR OF PHILOSOPH

Vortex-forced-oscillations of thin flexible plates

Fluid-structure interaction of a slender flexible cantilevered-element and vortices in an otherwise steady flow is considered here by investigating the dynamics of thin low-density polyethylene sheets subject to periodic forcing due to B\'enard-K\`arm\`an vortices in a $2$-meter long narrow water channel. The vortex shedding frequency $f_v$ is varied via the mean flow speed $U_0$ and the cylinder diameter $d_0 = 10$, $20$ and $40$ mm, while the structures' bending resistance is properly controlled via its Young's modulus $E$, thickness $e_b$ and length $L_b$. Thereby, it is first shown that the non-dimensional time-averaged sheet deflection, namely, the sheet \textit{reconfiguration} $\bar{h}_b/L_b \sim C_y^{\mathcal{V}/2}$ and also, the time-averaged \textit{drag force} $\bar{F}_d \propto U_0^{2+\mathcal{V}}$, where $\mathcal{V} \leq 0$ is the well-known Vogel number for flexible structures in a steady flow and $C_y = 12 \left({C_d \frac{1}{2} \rho U_0^2}/{E}\right) \left({ L_b^3/}{e_b^3} \right)$ is the Cauchy number comparing the relative magnitude of the profile drag force over a typical elastic restoring force, if the sheet were rigid. Measurements and a simple model based on torsional-spring-mounted flat plate illustrate that the tip amplitude $\delta_b$ is not only directly proportional to the characteristic size of the eddies, say $d_v$, but also to the sheet mechanical properties and the vortex flow characteristics such that $\delta_b/d_v \sim C_y^{(1+\mathcal{V})/2} \sqrt{U_0/f_v d_v}$. Furthermore, a rich phenomenology of structural dynamics including vortex-forced-vibration, lock-in with the sheet natural frequency, flow-induced vibration due to the sheet wake, multiple-frequency and modal response is reported

Droplet collection in a scaled-up rotating separator

Separation of droplets from a gas stream is a frequent operation in natural gas processing. The trend towards remote, contaminated fields demands compact, efficient and reliable demisting equipment. A new challenge is the cleaning of highly contaminated natural gas. In a novel process called condensed rotational separation (CRS), natural gas contaminants (CO2 and H2S) are removed by condensation. The low surface tension of the condensing species leads to a fine mist of 1{10 micron droplets, entrained in the clean gas stream. In CRS, the condensed droplets are separated from the gas in a rotating phase separator (RPS). The core of the RPS is a rotating element: a bundle of channels (tubes), contained in a cylinder which rotates around its axis. When a particle laden gas is led through the rotating channels, the centrifugal force drives the particles (droplets) towards the walls. The radial traveling distance of droplets is small as compared to the channel length. This effects the efficient separation of particles as small as 1 micron. To verify scaling laws and liquid removal, a full scale prototype was built at the Eindhoven University of Technology, based on a previous small scale CH4/CO2 test unit at Shell Global solutions in Amsterdam. The prototype was tested at atmospheric conditions, using air and water. The test rig models an 80 mmscfd (24 m3 n/s) natural gas installation, which, in terms of volume flow, is equivalent to an entire gas well. In previous RPS applications (e.g. air filtration, flue gas filtering), the flow inside the channels was laminar. However, high volume flow/high fluid density applications in the oil and gas industry are characterized by unstable or even turbulent channel flow. To quantify the effect of flow instabilities and turbulent mixing on the separation efficiency, a good measurement accuracy is needed. In order to determine the separation efficiency as a function of droplet size, a mist injection system was built and droplet size distributions were measured by means of laser diffraction particle sizing. The accuracy was improved by paying specific attention to channel entrance effects and vignetting in the laser diffraction system, plus reducing side leakage along the rotating element. By varying the gas flow rate and element rotation speed, the efficiency curve was measured in a large operating range. Compared to previous measurements in literature obtained with laminar RPS units, the accuracy was improved and better correspondence to theory was obtained. We further completed the theory of laminar efficiency for rectangular channels. In high pressure natural gas installations like CRS, a large gas density and high flowrates induce turbulent conditions within the rotating channels. To simulate high Reynolds numbers in the atmospheric test setup, an element with enlarged channels was built. To maintain the same separation efficiency, the element and prototype also had to be elongated. The subsequently obtained results are the first with unstable/turbulent flow till date. In the turbulent regime, measurements showed good correspondence to direct numerical simulations (DNS) of particle laden rotating pipe flow. Further investigation of the DNS results yielded a new model which characterizes the effect of mixing on the separation efficiency. For bulk Reynolds numbers below 2000, poor separation efficiencies were found due to flow instabilities in otherwise laminar flow. It is well known that nonrotating pipe flow becomes turbulent at bulk Reynolds numbers Re > 2000. However, sufficient rotation causes pipe flow to become unstable against in finitesimal disturbances already at Re = 83. The instabilities induce traveling spiral waves inside the rotating channels, which tend to trap particles and undo their separation. This is specifically relevant in RPS applications for oil/water separation. The negative effect of the spiral waves was taken into account by a new empirical correction factor. The measurement method was further applied to cyclones and vane packs. For axial cyclones an accompanying model was introduced, based on realistic vortex profiles. A benchmark was made for the efficiency of three types of demisters for natural gas processing: vane packs, cyclone decks and rotating elements

Potential Lost Productivity Resulting from the Global Burden of Myopia: Systematic Review, Meta-analysis, and Modeling

Purpose: We estimated the potential global economic productivity loss resulting from vision impairment (VI) and blindness as a result of uncorrected myopia and myopic macular degeneration (MMD) in 2015. Clinical Relevance: Understanding the economic burden of VI associated with myopia is critical to addressing myopia as an increasingly prevalent public health problem. Methods: We estimated the number of people with myopia and MMD corresponding to critical visual acuity thresholds. Spectacle correction coverage was analyzed against country-level variables from the year of data collection; variation in spectacle correction was described best by a model based on a human development index, with adjustments for urbanization and age. Spectacle correction and myopia data were combined to estimate the number of people with each level of VI resulting from uncorrected myopia. We then applied disability weights, labor force participation rates, employment rates, and gross domestic product per capita to estimate the potential productivity lost among individuals with each level and type of VI resulting from myopia in 2015 in United States dollars (US$). An estimate of care-associated productivity loss also was included. Results: People with myopia are less likely to have adequate optical correction if they are older and live in a rural area of a less developed country. The global potential productivity loss associated with the burden of VI in 2015 was estimated at US$244 billion (95% confidence interval [CI], US$49 billion–US$697 billion) from uncorrected myopia and US$6 billion (95$2 billion—US$17 billion) from MMD. Our estimates suggest that the Southeast Asia, South Asia, and East Asia Global Burden of Disease regions bear the greatest potential burden as a proportion of their economic activity, whereas East Asia bears the greatest potential burden in absolute terms. Conclusions: Even under conservative assumptions, the potential productivity loss associated with VI and blindness resulting from uncorrected myopia is substantially greater than the cost of correcting myopia