Transpiration Cooling - Its Theory and Application

Transpiration cooling of turbulent boundary layers - theory and applicatio

Turbine vane gas film cooling with injection in the leading edge region from a single row of spanwise angled holes

An experimental study of gas film cooling was conducted on a 3X size model turbine vane. Injection in the leading edge region was from a single row of holes angled in a spanwise direction. Measurements of the local heat flux downstream from the row of coolant holes, both with and without film coolant flow, were used to determine the film cooling performance presented in terms of the Stanton number ratio. Results for a range of coolant blowing ratio, M = 0 to 2.0, indicate a reduction in heat flux of up to 15 to 30 percent at a point 10 to 11 hole diameters downstream from injection. An optimum coolant blowing ratio corresponds to a coolant-to-freestream velocity ratio in the range of 0.5. The shallow injection angle resulted in superior cooling performance for injection closest to stagnation, while the effect of injection angle was insignificant for injection further from stagnation

Stagnation region gas film cooling: Effects of dimensionless coolant temperature

An experimental investigation was conducted to mode the film cooling performance for a turbine vane leading edge using the stagnation region of a cylinder in cross flow. Experiments were conducted with a single row of spanwise angled (25 deg) coolant holes for a range of the coolant blowing ratio and dimensionless coolant temperature with free stream-to-wall temperature ratio approximately 1.7 and Re sub D = 90000. the cylindrical test surface was instrumented with miniature heat flux gages and wall thermocouples to determine the percentage reduction in the Stanton number as a function of the distance downstream from injection (x/d sub 0) and the location between adjacent holes (z/S). Data from local heat flux measurements are presented for injection from a single row located at 5 deg, 22.9 deg, 40.8 deg, from stagnation using a hole spacing ratio of S/d = 5. The film coolant was injected with T sub c T sub w with a dimensionless coolant temperature in the range 1.18 or equal to theta sub c or equal to 1.56. The data for local Stanton Number Reduction (SNR) showed a significant increase in SNR as theta sub c was increased above 1.0

Stagnation region gas film cooling: Spanwise angled injection from multiple rows of holes

The stagnation region of a cylinder in a cross flow was used in experiments conducted with both a single row and multiple rows of spanwise angled (25 deg) coolant holes for a range of the coolant blowing ratio with a freestream to wall temperature ratio approximately equal to 1.7 and R(eD) = 90,000. Data from local heat flux measurements are presented for injection from a single row located at 5 deg, 22.9 deg, 40.8 deg, 58.7 deg from stagnation using a hole spacing ratio of S/d(o) = 5 and 10. Three multiple row configurations were also investigated. Data are presented for a uniform blowing distribution and for a nonuniform blowing distribution simulating a plenum supply. The data for local Stanton Number reduction demonstrated a lack of lateral spreading by the coolant jets. Heat flux levels larger than those without film cooling were observed directly behind the coolant holes as the blowing ratio exceeded a particular value. The data were spanwise averaged to illustrate the influence of injection location, blowing ratio and hole spacing. The large values of blowing ratio for the blowing distribution simulating a plenum supply resulted in heat flux levels behind the holes in excess of the values without film cooling. An increase in freestream turbulence intensity from 4.4 to 9.5 percent had a negligible effect on the film cooling performance

From supported membranes to tethered vesicles: lipid bilayers destabilisation at the main transition

We report results concerning the destabilisation of supported phospholipid bilayers in a well-defined geometry. When heating up supported phospholipid membranes deposited on highly hydrophilic glass slides from room temperature (i.e. with lipids in the gel phase), unbinding was observed around the main gel to fluid transition temperature of the lipids. It lead to the formation of relatively monodisperse vesicles, of which most remained tethered to the supported bilayer. We interpret these observations in terms of a sharp decrease of the bending rigidity modulus $\kappa$ in the transition region, combined with a weak initial adhesion energy. On the basis of scaling arguments, we show that our experimental findings are consistent with this hypothesis.Comment: 11 pages, 3 figure

Stable isotope compositions of fluid inclusions in biogenic carbonates

Measurements have been made of hydrogen, carbon, and oxygen isotope compositions of inclusion waters and CO2 extracted from eleven species of modern marine and freshwater skeletal carbonates. The samples were collected in environments of highly contrasting temperatures and isotopic compositions of ambient waters. Inclusion waters were extracted in vacuum by thermal decrepitation of samples that were previously treated with H2O2 to remove organic matter. Water extractions were quantitative above 200[deg]C for aragonite species and above 350-400[deg]C for calcite species. Amounts of water liberated ranged from 0.6% to 2.2% and were generally very reproducible within a species but varied strongly from one species to another. Except for red algae and corals, the [delta]18O values of the shells are in accord with crystallization of carbonate at or near equilibrium with marine water of [delta]18O near 0[per mille sign]. The inclusion waters, however, are not in oxygen isotope equilibrium with ambient water and have high [delta]18O values of +6 to +18[per mille sign]. These high [delta]18O values do not result from partial exchange between water and either the host carbonate or small amounts of CO2 released during decrepitation. [delta]D values of inclusion waters range from -80 to -10[per mille sign] and are sensitive to the presence of small amounts of organic matter. The data for each species define a distinct field in [delta]D-[delta]18O space that is controlled by a vital fractionation effect. Stable isotope compositions of inclusion waters can be explained by metabolic reactions that incorporate relatively 18O-rich O2 that is dissolved in the water and used by the organism in respiration. Thus, inclusion waters in shells probably represent remnants of metabolic fluids produced by the mantle epithelium. The stable isotope compositions of such waters most likely result from varying metabolic rates that are specific to each species, as well as to formation temperature and the isotopic composition of ambient waters.Inclusion fluids in biogenic carbonates constitute an isotopic reservoir that has heretofore been unrecognized. The [delta]18O and [delta]D values of the inclusion waters are very different from those of meteoric, magmatic, and seawaters. Because these trapped fluids are released by the shells during heating, they could play a role in burial diagenesis. Burial of significant amounts of biogenic carbonates could liberate enough water to control diagenetic or metamorphic reactions in some cases. In the absence of other types of fluids, the participation of inclusion waters in such reactions should be easily recognized by their distinctive isotopic compositions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31923/1/0000876.pd

RNAmute: RNA secondary structure mutation analysis tool

BACKGROUND: RNAMute is an interactive Java application that calculates the secondary structure of all single point mutations, given an RNA sequence, and organizes them into categories according to their similarity with respect to the wild type predicted structure. The secondary structure predictions are performed using the Vienna RNA package. Several alternatives are used for the categorization of single point mutations: Vienna's RNAdistance based on dot-bracket representation, as well as tree edit distance and second eigenvalue of the Laplacian matrix based on Shapiro's coarse grain tree graph representation. RESULTS: Selecting a category in each one of the processed tables lists all single point mutations belonging to that category. Selecting a mutation displays a graphical drawing of the single point mutation and the wild type, and includes basic information such as associated energies, representations and distances. RNAMute can be used successfully with very little previous experience and without choosing any parameter value alongside the initial RNA sequence. The package runs under LINUX operating system. CONCLUSION: RNAMute is a user friendly tool that can be used to predict single point mutations leading to conformational rearrangements in the secondary structure of RNAs. In several cases of substantial interest, notably in virology, a point mutation may lead to a loss of important functionality such as the RNA virus replication and translation initiation because of a conformational rearrangement in the secondary structure