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Vertical Surfaces (vertical + surface)
Selected AbstractsFlame height correlation and upward flame spread modellingFIRE AND MATERIALS, Issue 6 2002Kuang- Chung Tsai Previous work has demonstrated that flame height is one of the two most important parameters determining the rate of vertical flame spread on a wall. Flame spread models rely on empirical flame height correlations of the form Xf=KQ,,n, but there have been no carefully controlled experiments designed to establish the validity of such correlations and there are no data for values of Q,,< c.25 kW/m. Two new sets of data are presented here, one based on experiments with 6 mm thick PMMA slabs (heights 25,250 mm, width 50,150 mm) as the fire source, measuring Q,, and Xf simultaneously. This set relates to the early stages of a wall fire when Q,,< 30 kW/m. The other set of data was obtained with a vertical gas-fired panel which consisted of an array of 14 independent burners arranged to allow the aspect ratio of the burning surface to be varied. The data confirm that the flame height correlates with Q,,, but reveal (inter alia) that there are two regions, for values of Q,, greater than and less than c. 20 kW/m. An existing upward flame spread model was modified to allow these two correlations to be incorporated to predict the development of a small fire on a vertical surface for these two regions, which would provide more realistic modelling information. Copyright © 2002 John Wiley & Sons, Ltd. [source] Effect of double stratification on mixed convection heat and mass transfer from a vertical surface in a fluid-saturated porous mediumHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2010V.J. Bansod Abstract This paper presents the mixed convection heat and mass transfer near a vertical surface in a stratified porous medium using an integral method. The conservation equations that govern the problem are reduced to a system of coupled non-linear ordinary differential equations, which is then reduced into a single algebraic equation using exponential profiles for the temperature and concentration. The results for heat and mass transfer rates in terms of Nusselt and Sherwood number are presented for a wide range of governing parameters like the buoyancy ratio (N), Lewis number (Le), flow driving parameter (Ra/Pe), in addition to both thermal and solutal parameters (S and R). The results indicate that the stratification effects have considerable influence on both the heat and mass transfer rates. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20300 [source] On the analytical solution of the Bejan-Khair equation arising in free convection in porous mediaHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2010V.J. Bansod Abstract This paper revisits the fundamental problem of free convection heat and mass transfer over a heated vertical surface embedded in a porous medium using analytical techniques. An integral procedure is applied to the boundary layer similar equation for the combined heat and mass transfer from a vertical surface in a porous medium. The analytical approximations have covered a wide range of governing parameters of the problem. The results for both Nusselt and Sherwood numbers agree well with numerical results published in the literature. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20297 [source] Effects of chemical reaction, heat and mass transfer on non-linear MHD flow over an accelerating surface with heat source and thermal stratification in the presence of suction or injectionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2003S. P. Anjali Devi Abstract An approximate numerical solution for the steady MHD laminar boundary-layer flow over an accelerating vertical surface with suction or injection in the presence of species concentration and mass diffusion has been obtained by solving the governing equations using R.K. Gill method. The fluid is assumed to be viscous, incompressible and electrically conducting with a magnetic field applied transversely to the direction of the flow. It has been observed that in the presence of mass diffusion: (i) in the case of suction, the velocity decreases and the temperature distribution and concentration of the fluid increase and for injection, the velocity increases and the temperature distribution and concentration of the fluid decrease with increase of thermal stratification parameter, (ii) in the presence of thermal stratification parameter in both the cases of suction and injection, the skin friction and rate of mass transfer decrease and the rate of heat transfer of the fluid increases with increase of chemical reaction effects, (iii) in the cases of suction and injection, an increase in the strength of magnetic field leads to fall in the velocity and rise in the temperature and concentration of the fluid along the surface. Copyright © 2003 John Wiley & Sons, Ltd. [source] Mixed convection flow of non-Newtonian fluid from a slotted vertical surface with uniform surface heat fluxTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009Rama Subba Reddy Gorla Abstract In the present paper, the combined convection flow of an Ostwald,de Waele type power-law non-Newtonian fluid past a vertical slotted surface has been investigated numerically. The boundary condition of uniform surface heat flux is considered. The equations governing the flow and the heat transfer are reduced to local non-similarity form. The transformed boundary layer equations are solved numerically using implicit finite difference method. Solutions for the heat transfer rate obtained for the rigid surface compare well with those documented in the published literature. From the present analysis, it is observed that, an increase in , leads to increase in skin friction as well as reduction in heat transfer at the surface. As the power-law index n increases, the friction factor as well as heat transfer increase. Dans cet article, on a étudié numériquement l'écoulement de convection combinée d'un fluide non-newtonien de loi de puissance de type Ostwald-de Waele en aval d'une surface perforée verticale. La condition limite d'un flux de chaleur de surface uniforme est considérée. Les équations gouvernant l'écoulement et le transfert de chaleur sont réduites à la forme de non-similarité locale. Les équations de couche limite transformées sont résolues numériquement par la méthode des différences finies implicites. Les solutions pour la vitesse de transfert de chaleur obtenues pour la surface rigide se comparent bien à celles qui sont décrites dans la littérature scientifique publiée. À partir de la présente analyse, on observe qu'une augmentation de , mène à une augmentation du frottement superficiel ainsi qu'à une réduction du transfert de chaleur à la surface. Lorsque l'indice de loi de puissance n augmente, le facteur de friction et le transfert de chaleur augmentent également. [source] Slip Casting of ZrB2,SiC Composite Aqueous SuspensionsADVANCED ENGINEERING MATERIALS, Issue 3 2010Valentina Medri Slip casting of concentrated aqueous suspensions was set up as forming technique for the production of crucibles from ZrB2,SiC composite powder. The dispersion effectiveness and the effect on the final microstructures of two commercial ammonium polyacrylates (Duramax D3005 and Dolapix PC33) used as dispersants were investigated. The first goal was pursued by evaluating the zeta potential of the powders in water at different concentrations of additives, while the second one was assessed by analyzing the microstructure. Duramax D3005 resulted more effective than Dolapix PC33 in electrostatically stabilize the suspensions. Correspondently, almost homogeneous microstructures and lower final porosity of the sintered crucibles were obtained with Duramax D3005, while ZrB2 layers on the vertical surfaces initially in contact with the plaster molds were observed using Dolapix PC33. Moreover, the use of this latter dispersant did not allow the preparation of thick crucible walls due to the sample rupture during the binders pyrolysis stage. [source] Detection of a low-relief 18th-century British siege trench using LiDAR vegetation penetration capabilities at Fort Beauséjour,Fort Cumberland National Historic Site, CanadaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 5 2009Koreen Millard Airborne Light Detection and Ranging (LiDAR), a remote sensing data collection technique, has many applications in the field of archaeology, including aiding in the planning of field campaigns, mapping features beneath forest canopy, and providing an overview of broad, continuous features that may be indistinguishable on the ground. LiDAR was used to create a high-resolution digital elevation model (DEM) in a heavily vegetated area at Fort Beauséjour,Fort Cumberland National Historic Site, Canada. Previously undiscovered archaeological features were mapped that were related to the siege of the fort in 1755. Features that could not be distinguished on the ground or through aerial photography were identified by overlaying hillshades of the DEM created with artificial illumination from various angles. LiDAR provides accurate digital topographic models with the additional benefit of mapping vertical surfaces in accurate detail below the forest canopy. © 2009 Wiley Periodicals, Inc. [source] Micro-bubble emission boiling from horizontal and vertical surfaces to subcooled parallel flow waterHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2003Satoshi Kumagai Abstract Heat removal of more than 10 MW/m2 in heat flux has been required in high-heat-generation equipment in nuclear fusion reactors. In some conditions of water subcooling and velocity, there appears an extraordinary high heat flux boiling in the transition boiling region. This boiling regime is called micro-bubble emission boiling (MEB) because many micro-bubbles are spouted from the heat transfer surface accompanying a huge sound. The study intent is to obtain heat transfer performance of MEB in horizontal and vertical heated surfaces to parallel flow of subcooled water, comparing with CHF of this system. Three types of MEB with different heat transfer performance and bubble behavior are observed according to the flow velocity and liquid subcooling. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(2): 130,140, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10077 [source] Expression of beta-keratin mRNAs and proline uptake in epidermal cells of growing scales and pad lamellae of gecko lizardsJOURNAL OF ANATOMY, Issue 1 2007Lorenzo Alibardi Abstract Beta-keratins form a large part of the proteins contained in the hard beta layer of reptilian scales. The expression of genes encoding glycine,proline-rich beta-keratins in normal and regenerating epidermis of two species of gecko lizards has been studied by in situ hybridization. The probes localize mRNAs in differentiating oberhautchen and beta cells of growing scales and in modified scales, termed pad lamellae, on the digits of gecko lizards. In situ localization at the ultrastructural level shows clusters of gold particles in the cytoplasm among beta-keratin filaments of oberhautchen and beta cells. They are also present in the differentiating elongation or setae of oberhautchen cells present in pad lamellae. Setae allow geckos to adhere and climb vertical surfaces. Oberhautchen and beta cells also incorporate tritiated proline. The fine localization of the beta-keratin mRNAs and the uptake of proline confirms the biomolecular data that identified glycine,proline-rich beta-keratin in differentiating beta cells of gecko epidermis. The present study also shows the presence of differentiating and metabolically active cells in both inner and outer oberhautchen/beta cells at the base of the outer setae localized at the tip of pad lamellae. The addition of new beta and alpha cells to the corneous layer near the tip of the outer setae explains the anterior movement of the setae along the apical free-margin of pad lamellae. The rapid replacement of setae ensures the continuous usage of the gecko's adhesive devices, the pad lamellae, during most of their active life. [source] Molecular Reproduction & Development: Volume 76, Issue 4MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2009Article first published online: 23 FEB 200 Computed cost function for in silico optimization of a cryoprotectant removal protocol. Karlsson et al. used membrane permeability data to predict the response of rhesus monkey oocytes to various methods for removing intracellular propylene glycol. The process parameter-space is shown as a gray plane; the corresponding response surface represents the expected cytotoxicity, and vertical surfaces (green and violet) demarcate predicted regimes of deleterious osmotic shock. See the accompanying article by Karlsson et al. in this issue. [source] Reestablishment of the Southern California Rocky Intertidal Brown Alga, Silvetia compressa: An Experimental Investigation of Techniques and Abiotic and Biotic Factors That Affect Restoration SuccessRESTORATION ECOLOGY, Issue 2010Stephen G. Whitaker Previous research has indicated that many rocky intertidal macrophyte communities in southern California, and other locations around the world, have shifted from larger, highly productive, fleshy seaweeds toward a smaller, less productive, disturbance-tolerant flora. In widespread decline are ecologically important, canopy-forming, brown seaweeds, such as the southern California rockweed species Silvetia compressa. Restoration efforts are common for depleted biogenic species in other habitats, but restoration within rocky intertidal zones, particularly on wave-exposed coasts, has been largely unexplored. In two phases, we attempted to restore Silvetia populations on a southern California shore by transplanting live plants and experimentally investigating factors that affect their survival. In Phase I, we implemented a three-way factorial design where juvenile Silvetia thalli were transplanted at four sites with a combination of simulated canopy and herbivore exclusion treatments. Transplant survival was low, although enhanced by the presence of a canopy; site and herbivore presence did not affect survival. In Phase II, we used a two-way factorial design, transplanting two size classes of rockweeds (juveniles and reproductive adults) on horizontal and partially shaded, north-facing vertical surfaces at a target location where this rockweed has been missing since at least the 1970s. Transplant survival was moderate but lower than natural survival rates. Larger thalli exhibited significantly higher survival rates than smaller thalli in both the transplanted and naturally occurring populations, particularly on vertical surfaces. Higher mortality on horizontal surfaces may have been due to differences in desiccation stress and human trampling. Transplanting reproductive adults resulted in the subsequent recruitment of new individuals. [source] Disturbance mediates the effects of nutrients on developing assemblages of epibiotaAUSTRAL ECOLOGY, Issue 8 2008NELSON VALDIVIA Abstract Local dynamics such as resource enhancement (e.g. nutrient supply) and stochastic events of destruction (disturbances that provide new space) are hypothesized to counteractively affect species diversity and composition. We tested the independent and interactive effects of nutrients and disturbance on the development of assemblages of epibiota attached to vertical surfaces in an oligotrophic system. Nutrient concentrations were manipulated at three levels (ambient, medium and high) while disturbance was manipulated by removing biomass at seven frequencies (0×, 2×, 3×, 4×, 5×, 7×, 12×). Nutrient and disturbance regimes had opposing effects on diversity such that species richness increased with resource enhancement (nutrients) and declined with disturbance. These results support the model that increased heterogeneity of distribution of limiting resources allows the coexistence of species with low and high resource requirements. [source] | |||||||||||||