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Shock wave-boundary layer interactions (SWBLI) are observed in several practical high-speed internal flows, such as compressor blades, turbine cascades, nozzles and so on. Shock induced oscillations (SIO), aerodynamic instabilities so-called buffet flows, flutter, aeroacoustic noise and vibration are the detrimental consequences of this unsteady shock-boundary layer interactions. In the present study, a numerical computation has been performed to investigate the compressible flow characteristics around a 12% thick biconvex circular arc airfoil in a two dimensional channel. Reynolds averaged Navier-Stokes equations with two equation k-ωshear stress transport (SST) turbulence model have been applied for the computational analysis. The flow field characteristics has been studied from pressure ratio (ratio of back pressure, pbto inlet total pressure, p01) of 0.75 to 0.65. The present computational results have been compared and validated with the available experimental data. The results showed that the internal flow field characteristics such as shock wave structure, its behavior (steady or unsteady) and the corresponding boundary layer interaction are varied with pressure ratio. Self-excited shock oscillation was observed at certain flow conditions. Moreover, the mode of unsteady shock oscillation and its frequency are varied significantly with change of pressure ratio.

The mass flow rate measurement using a critical nozzle shows the validity of the inviscid theory, indicating that the discharge coefficient increases and approaches unity as the Reynolds number increases under the ideal gas law. However, when the critical nozzle measures the mass flow rate of a real gas such as hydrogen at a pressure of hundreds bar, the discharge coefficient exceeds unity, and the real gas effects should be taken into account. The present study aims at investigating the flow features of the critical nozzle using high-pressured hydrogen gas. The axisymmetric, compressible Navier-Stokes computation is employed to simulate the critical nozzle flow, and a fully implicit finite volume method is used to discretize the governing equation system. The real gas effects are simulated to consider the intermolecular forces, which account for the possibility of liquefying hydrogen gas. The computational results are compared with past experimental data. It has been found that the coefficient of discharge for real gas can be corrected properly below unity adopting the real gas assumption.

This paper describes computational work to understand the unsteady flow-field of a shock wave discharging from an exit of a duct and impinging upon a flat plate. A flat plate is located downstream, and normal to the axis of the duct. The distance between the exit of the duct and flat plate is changed. In the present study, two different duct geometries (i.e., square and cross section) are simulated to investigate the effect of duct geometry on the un-steady flows of a shock wave. In computation, the total variation diminishing (TVD) scheme is employed to solve three-dimensional, unsteady, compressible, Euler equations. Computations are performed over the range of shock Mach number from 1.05 to 1.75. Computational results can predict the three-dimensional dynamic behaviour of the shock wave impinging upon the flat plate. The results obtained show that the pressure increase generated on the plate by the shock impingement depends on the duct geometry and the distance between the duct exit and plate, as well as the shock Mach number. It is also found that for the duct with cross-section, the unsteady loads acting on the flat plate are less, compared with the square duct.

The present study describes an experimental work to investigate the effect of a nozzle exit reflector on a supersonic jet that is discharged from a convergent–divergent nozzle with a design Mach number of 2.0. An annular reflector is installed at the nozzle exit and its diameter is varied. A high-quality spark schlieren optical system is used to visualize detailed jet structures with and without the reflector. Impact pressure measurement using a pitot probe is also carried out to quantify the reflector’s effect on the supersonic jet which is in the range from an over-expanded to a moderately under-expanded state. The results obtained show that for over-expanded jets, the reflector substantially increases the jet spreading rate and reduces the supersonic length of the jet, compared with moderately under-expanded jets. The reflector’s effect appears more significant in imperfectly expanded jets that have strong shock cell structures, but is negligible in correctly expanded jet.

Abstract: Critical nozzle is defined as a device to measure the mass flow rate with only the nozzle supply conditions, making use of the flow choke phenomenon at the nozzle throat. Recently, such critical nozzles have been extensively utilized to measure the mass flow rate in a variety of industrial applications. For the measurement of mass flow rates in a wide range of operation conditions, the critical nozzle is required to be designed with different diameters. The objective of the present study is to investigate the effectiveness of a variable critical nozzle. A rod with a small diameter is inserted into the critical nozzle to change the effective cross-sectional area of the critical nozzle. Experimental work is performed to measure the mass flow rate of the critical nozzle with rod. Computational work is carried out using the two-dimensional, axisymmetric, compressible Navier–Stokes equations which are discretized using a fully implicit finite volume method. The diameter of the rod is varied to obtain different mass flow rates through the variable critical nozzle. Computational results predict well the measured mass flow rates. The boundary layer displacement and momentum thickness at the throat of the critical nozzle are given as a function of Reynolds number. The discharge coefficient of the critical nozzle is given as an empirical equation.

The present computational study addresses the attenuation of the shock wave propagating in a duct, using a porous wall/cavity system. In the present study, a weak shock wave propagating over the porous wall/cavity system is investigated with computational fluid dynamics. A total variation diminishing scheme is employed to solve the unsteady, two-dimensional, compressible, Navier-Stokes equations. The Mach number of an initial shock wave is changed in the range from 1.02 to 1.12. Several different types of porous wall/cavity systems are tested to investigate the passive control effects. The results show that wall pressure strongly fluctuates due to diffraction and reflection processes of the shock waves behind the incident shock wave. From the results, it is understood that for effective alleviation of tunnel impulse waves, the length of the perforated region should be sufficiently long.

Abstract. The present study addresses experimental results for investigating the details of the near field flow characteristics produced in an under-expanded, dual, coaxial, swirling jet. The under-expanded swirling jet is discharged from a sonic inner nozzle. An outer annular nozzle produces co- and counter-swirling streams relative to the inner primary swirling jet. The interaction between both the outer annular swirling stream and inner under-expanded swirling jet is quantified by impact and static pressure measurements, and visualized by using the shadowgraph method. Experiments are performed for several different pressure ratios. The results show that the outer secondary co-swirling jet significantly changes the structure of the inner under-expanded swirling jet, such as the shock structures and the recirculation region generated at the jet axis. The effect of the outer secondary stream on the major structures of the inner primary swirling jet is strongly dependent on the pressure ratio of the inner swirling jet, regardless of the swirl direction of the outer stream.

The present study addresses the distortion of the compression wave reflected from an open end of a shock tube. An experiment is carried out using the simple shock tube with an open end. Computational work is also performed to represent the experimented flows. The second-order Total Variation Diminishing scheme is employed to numerically solve the unsteady, axisy-mmetric, inviscid, compressible governing equations. Both the experimented and predicted results are in good agreement. The generation and development mechanisms of the compression wave, which is reflected from the open end of the shock tube, are obtained in detail from the present computations. The effect of size of the baffle plate at the open-end that causes the reflection of the incident expansion wave is found negligible. A good correlation is obtained for transition of the reflected compression wave to a shock wave inside the tube. The present data show that for a given wave length of the incident expansion wave the transition of the reflected compression wave to a shock wave can be predicted with good accuracy.

Shock discharge from a duct exit is often encountered in many engineering practices and usually gives rise to an annoying noise problem similar to a sonic boom. Such a noise can have hazardous effects on human beings, as well as structures in the vicinity, unless proper control strategies are developed. The objective of the current work is to characterize the impulse wave caused by a weak shock discharged from an open end of a duct. Experiments were performed using an open-ended shock tube for shock Mach number of 1·02–1·45. Computational analysis was applied to model the unsteady flow field by application of axisymmetric, inviscid, compressible equations. A total variation diminishing (TVD) numerical scheme was used to solve the conservation equation system. The effect of a baffle plate, installed at the duct exit, on the impulse wave was investigated both experimentally and by numerical calculation. The results of the experiments were in good agreement with the results of numerical calculations. The results showed that the baffle plate affects the strength of the impulse wave only when its diameter is less than 3 times the duct diameter. With the diameter of the baffle plate less than 3 times the duct diameter, the strength of an impulse wave for a given shock Mach number increases when the baffle plate becomes larger. The impulse wave has a directivity to the centerline of the duct. It was found that for prediction of the impulse wave aero-acoustical theory should be used only at distances larger than four times the duct diameter.

Hepatocyte-like cells have been observed in the pancreas of the rat. We examined the bile acid biosynthetic function of these cells to determine whether they were real hepatocytes. This study investigated the existence of two liver-specific enzymes involved in bile acid biosynthesis (cholesterol 7alpha-hydroxylase and delta(4)-3-ketosteroid 5beta-reductase) in the hepatocyte-like cells. We could demonstrate cholesterol 7alpha-hydroxylase activity and its circadian rhythm in the hepatocyte-like cells. Northern blot analysis demonstrated the expression of messenger RNA for the 7alpha-hydroxylase and delta(4)-3-ketosteroid 5beta-reductase in the pancreatic hepatocyte-like cells. To measure the amount of the messenger RNA, we used the competitive polymerase chain reaction method for the 7alpha-hydroxylase. This quantitation revealed the existence of a circadian rhythm of cholesterol 7alpha-hydroxylase messenger RNA in the hepatocyte-like cells. These results indicated that bile acid biosynthesis was performed in the pancreatic hepatocyte-like cells as noted as in the liver parenchymal cells.

Abstract: Neosaimiri fieldsi, from the South American middle Miocene locality of La Venta, is represented by a relatively complete mandible and dentition that strongly resembles that of extantSaimiri. Comparison with a large sample of mandibles ofSaimiri indicates that this specimen cannot be distinguished from modern populations on the basis of any reportedly diagnostic feature, such as cingulid development, molar length ratio, trigonic/talonid ratio, or mandibular depth. The fossil is best considered an extinct species of the modern genusSaimiri until further material indicates otherwise.

Experimental investigations on the effect of inlet turbulence and flow distortion on the performance of a monoplane and a biplane Wells turbine are reported. The performance of biplane Wells turbine is more sensitive to turbulence when compared with a monoplane. The primary effect of increase in turbulence on the performance of Wells turbine is the postponement of stall.

This paper describes the conversion of 5β-cholestane-3α,7α,12α,25-tetrol into 5β-cholestane-3α,7α,12α,24β,25-pentol by liver microsomes. A sensitive radioactive assay for measuring the formation of 5β-cholestane-3α,7α,12α,24β,25-pentol was developed. Optimal assay conditions for human and rat microsomal systems were established. A higher 24β-hydroxylation activity was detected in rat than in human liver under the conditions employed. The hydroxylation of 5β-cholestane-3α,7α,12α,25-tetrol by the rat liver microsomal fraction fortified with NADPH was stimulated about two-fold by administration of phenobarbital. Phenobarbital treatment also stimulated hydroxylations at C-23, C-24α, and C-26. Carbon monoxide markedly inhibited all side-chain hydroxylations. In contrast, side-chain hydroxylase activities were not affected in animals deprived of food for 48 hr. These results are consistent with a previously postulated cholic acid biosynthetic pathway involving 5β-cholestane-3α,7α,12α,24β,25-pentol as a key intermediate in man and in the rat.

A bile acid disappearance test using an enzyme immunoassay for ursodeoxycholic acid (UDCA) is presented. The immunoassay employs an antiserum produced in rabbits with UDCA coupled by amide linkage to egg albumin. An antigen (UDCA)-enzyme (beta-D-galactosidase) complex was prepared by adding the N-hydroxy-succinimide ester of UDCA to beta-D-galactosidase in a molar ratio of 5000:1. The anti-UDCA serum was coupled to glass beads and a competitive reaction between bile acids and UDCA coupled to the enzyme on the glass beads was measured by determining enzyme activity. One bead was used for each test tube. Thus it was convenient to wash and transfer the bead to a fresh test tube after incubation. The procedure requires 2.5 hr at 30 degrees C for the competitive reaction and enzyme assay. Using a 1:100 dilution of anti-serum, the intensity of fluorescence of 4-methylumbelliferone produced from 4-methylumbelliferyl-beta-D-galactoside by the enzyme decreased linearly with a logarithmic increase of UDCA concentration over a range of from 0.1 to 10 pmnd taurine conjugates, and good recovery data were obtained. The development of the enzyme immunoassay using glass beads shortens analysis time; furthermore, the method makes it possible to detect obstructive jaundice in rabbits before the serum bilirubin level is elevated.

The effect of surgical removal of cecum and appendix on bile acid metabolism was studied in the rabbit. Bile acid composition of bile and intestinal contents were analyzed by gas-liquid chromatography and individual bile acids were further identified by mass spectrometry. In normal, intact rabbits (group I), the biliary bile acids consisted largely of deoxycholic acid (DA) 95.3 +/- 1.0 (mean +/- SE) %; cholic acid (CA) 2.3 +/- 1.1% and lithocholic acid (LA) 1.0 +/- 0.3% were also detected. Removal of cecum and appendix (group II) produced significant changes in biliary bile acid composition: DA fell to 58.3 +/- 31.8%, CA rose to 37.7 +/- 10.4%, and LA was barely detectable (0.3 +/- 0.1%). Administration of chenodeoxycholic acid (CDA), 125 mg/day, produced severe hepatotoxicity, reduced food intake, and produced weight loss (group III). Biliary LA rose to 15.0 +/- 1.3%, while DA was 61.3 +/- 14.0% and CDA 21.8 +/- 14.6% of total biliary bile acids. Feeding CDA to animals without cecum and appendix (group IV) resulted in a slight increase of LA (3.2 +/- 2.2%) compared to group III, and appreciable amounts of ursodeoxycholic acid (UDA) 32.0 +/- 9.8% and of 7-ketolithocholic acid (7-KLA) 3.0 +/- 0.6% appeared in bile. The animals of group IV exhibited no hepatotoxicity and ate and gained weight normally. These results indicate that the microbial population of cecum and appendix is active in 7alpha-dehydroxylation of primary bile acids and that removal of these organs results in an increased formation of UDA by an unknown mechanism.-Yahiro, K., T. Setoguchi, and T. Katsuki. Effect of cecum and appendix on 7alpha-dehydroxylation and 7beta-epimerization of chenodeoxycholic acid in the rabbit.