Dome Surface Research Articles

Film thickness of free falling water flow on a large-scale ellipsoidal surface

Falling water film flow on large-scale curved dome of passive containment, of which the data is very scarce, plays a crucial role for the thermal-hydraulic behaviors of passive containment cooling system (PCCS) in advanced nuclear power plant. It exhibits a developing phenomenon in nature because of continuous changes of the inclined angle, the width and the extend angle of the flow channel in the longitudinal direction. In order to examine the influences of these continuously varying factors on the flow characteristics, the film thickness of free falling water flow on a large-scale ellipsoidal surface with continuously varying inclined angle and extend angle has been measured experimentally. The working fluid is the low hardness municipal water, of which the inlet temperature is the same as ambient environment. Capacitive non-contact displacement transducers, Micro-Epsilon capaNCDT-CS10 sensors, are used to measure the film thickness at different locations with inclined angle ranging from 18° to 76°. The range of the film Reynolds number is from 360 to 2175. Detailed analyses on the relationship between the dimensionless film thickness and the film Reynolds number at different longitudinal positions on the dome surface are carried out. No obvious influence on the evolution of falling film caused by the continuous changes of the inclined angle, the width and the extend angle of flow channel on the dome can be observed. A new empirical correlation of film thickness on the ellipsoid dome surface is suggested based on the data obtained in the present experiments. Most of experimental data points fall in the range of ±15% around its prediction. Comparisons are also made between the suggested correlation with other theoretical or empirical correlations of film thickness in straight channels reported in the literature, as well as the numerical results on curved surface by computational fluid dynamics software COMMIX and GASFLOW-MPI. Fairly good agreements are observed, proving that the suggested correlation can predict the film thickness on the curved dome surface of PCCS with much accuracy and then provide a more reliable basis for further analysis of the conjugate heat and mass transfer of PCCS.

Regression modelling of radiant fluxes on different view factors under shading in a densely built environment

ABSTRACTThe exchange of radiant fluxes between different surfaces in an outdoor environment can be described with an enclosure theory. It provides a physical understanding of the relationship between different surfaces and consequent radiant fluxes within an enclosure, which is constructed by including surfaces of building façades and an imaginary surface of sky dome. Radiant fluxes on a surface can be expressed as linear combinations of view factors. This study examines the linear dependencies of urban radiant fluxes on view factors, namely Sunlit View Factor (SLVF), Green View Factor (GNVF), and Sky View Factor (SVF), using an empirical regression analysis. Results revealed a simple and linear correlation between view factors and outdoor radiant fluxes. As such, a quick estimation of the potential increase in the outdoor mean radiant temperature in relation to neighboring built environments can be achieved, and industry guidelines for designing thermally comfortable open spaces can be formulated accordingly.

Optimized design method for the inner surface of a conformal dome based on the ray tracing approach.

Traditional optical domes are spherical, which introduces constant aberrations with look angle. However, spherical domes are not optimum for reducing aerodynamic drag. Conformal domes deviate from spherical to reduce drag but they generate dynamic aberrations varying significantly with look angle in the field of regard. Thus, conformal domes require unique challenges for aberration correction. This paper presents a method to reduce the dynamic aberrations through designing the inner surface of conformal domes. This method follows the principle that the optical axis ray of the imaging system maintains the same direction after refraction through the conformal dome for different look angles. Based on this principle, equations that the inner surface should satisfy are established and a numerical solution method is introduced. Eventually, Zernike polynomial coefficients of Z4, Z5, Z8, and Z9, which represent defocus, astigmatism, coma, and spherical aberration, respectively, are analyzed for quadratic domes with different inner surfaces. Compared with domes with traditional inner surfaces, quadratic domes with the inner surfaces calculated by this method have smaller Zernike aberrations. In conclusion, this design method for the inner surface can effectively reduce dynamic aberrations.

Subtalar Joint Alignment in Ankle Osteoarthritis

Category: Ankle Arthritis, Hindfoot Introduction/Purpose: The influence of the subtalar joint on the evolution of ankle joint osteoarthritis is still a matter of debate. Although subtalar joint compensation of deformities above the ankle joint was proposed until mid-stage of ankle osteoarthritis, the evidence of this assumption is weak. In this study, we investigated the subtalar joint alignment in different stages of ankle joint osteoarthritis using weightbearing CT scans. The influence of the tibio-talar tilt and presence of subtalar joint osteoarthritis was additionally assessed. We hypothesized, that the subtalar joint compensates for deformities above the ankle joint in early- to mid-stage of ankle osteoarthritis. We also hypothesized, that subtalar joint compensation increases with a pronounced tibio-talar tilt and decreases with the presence of subtalar joint osteoarthritis. Methods: We included patients with ankle joint osteoarthritis treated in our institution from January 2013 to April 2016. A control group of 28 patients was additionally assessed. Varus and valgus ankles were subdivided according to the modified Takakura classification, the tilt of the talus in the ankle mortise and stage of subtalar joint osteoarthritis. The type of ankle osteoarthritis was diagnosed on a plain weightbearing anterior to posterior radiograph of the ankle. The medial distal tibial angle (TAS) and the angle between the tibial shaft and the surface of the talar dome (TTS) were measured. The subtalar joint alignment was assessed using weightbearing CT scans. Two angles were assessed: The subtalar inclination angle (SIA) was measured to investigate the subtalar compensation. For assessment of the morphology of the talus, the inftal-subtal angle (ISA) was determined. Results: This analysis showed significant differences of the subtalar inclination between varus feet and the controls (SIA, P=.001). Regarding the talar morphology, significant differences were found between varus/ valgus feet and the controls (ISA, P=.001 and .036, respectively). No significant differences of the subtalar joint inclination and talar morphology could be identified comparing different stages of ankle joint osteoarthritis inside the varus or valgus group. No relationship between the tilt of the talus in the ankle joint mortise and the subtalar joint inclination or talar morphology was identified. Neither presence nor absence of subtalar joint osteoarthritis influenced the subtalar joint inclination and talar morphology. Conclusion: Varus ankles compensate in the subtalar joint for deformities above the ankle joint. Compensation had no influence on the stage of ankle osteoarthritis, extent of the tibio-talar tilt and stage of subtalar joint osteoarthritis. Consequently, the progression of ankle joint osteoarthritis is more depended on the supramalleolar alignment and integrity of the periarticular structures (i.e. ligaments and tendons) than on the osseous alignment of the subtalar joint.

К ВОПРОСУ О ПРИМЕНЕНИИ ПАРАБОЛИЧЕСКИХ ОБОЛОЧЕК ВРАЩЕНИЯ В СТРОИТЕЛЬСТВЕ В 2000-2017 ГОДАХ

Dome is often used by architects for cover of large spans. Only spherical, conical, elliptical, parabolic, and hyperbolic surfaces of revolution among tens of the well-known surfaces of revolution can be taken for middle surfaces of domes. Spherical domes have the most spread in modern building due to simplicity of their form in comparison with other shells of double curvature. But researches of paraboloidal domes do not end. Some new information on strength analysis of parabolic shells, on determination of the frequencies of their natural vibrations and the examples of application of paraboloid of revolution in civil engineering in 1900=2017 are presented in this review paper. The main presented bibliography was published in XXI century.

Wind effect on grooved and scallop domes

This paper numerically studies the wind effect on grooved and scallop domes. The introduction of a groove on a spherical dome causes abrupt change on its wind pressure coefficient (Cp) in the vicinity of the groove. The sharpness of indentation varies with the position angle of the axis of the groove to wind direction and obtains its highest effect at 90°. This paper develops equations for the distribution of Cp on the surface of spherical, grooved and scallop domes with rise to span ratios [0, 0.7]. The results of the equations agree reasonably well with that of CFD.

Critical bending radius of thin single-crystalline silicon with dome and pyramid surface texturing

Four-point bending tests are performed on 50-μm-thick single-crystalline silicon (Si) wafers with dome- and pyramid-shaped surface patterns, which are used as flexible Si solar cells. Surface patterns, which act as stress concentrators, reduce the flexural strengths, leading to larger critical bending radius. The critical bending radii of surface-textured Si are much smaller than the calculated values for a single-notch geometry. The finite element analysis shows that the stress concentrations at the tips of the surface patterns effectively disperse in fine and periodic dome and irregular pyramid patterns.

Status of dynamic water film model development in 3-D CFD code GASFLOW-MPI for analysis of passive containment cooling system

The advanced passive PWR AP-1000 and AP-1400 are pressurized water reactors (PWR) with advanced passive safety systems. Most recognize the passive containment cooling system (PCCS) as being one of the most important concepts for advanced passive safety systems. Following a postulated design-base-accident (DBA), an outside cold liquid-water spray is injected on the apex of the spheroidal dome. The resulting water film drains under gravitational body forces over the outside dome surface and down the cylinder surface. This PCCS removes heat from the containment interior to reduce potentially damaging pressure and temperature loads. A numerical model for simulating the falling water film transport in PCCS has been developed in 3-D CFD code GASFLOW-MPI. The water film model is governed by mass, momentum and energy transport equations with essential source terms for inter-phase exchange. The conjugate heat and mass transfer between the gas mixtures inside the containment, water film, and the gas in the annular space outside of the steel containment can be simulated. The heat conduction in the solid steel containment is calculated as well. In order to facilitate model validation in GASFLOW-MPI, we have developed an exact numerical solution (ENS) for the one-dimensional steady-state liquid film flow over an ellipsoidal-domed cylinder. Although the ENS assumes constant containment wall temperature and outside ambient air temperature, it can incorporates any generalized heat transfer correlation between the containment surface and water film as well as any generalized heat and mass (evaporation) transfer correlations between the film and outside ambient air. ENS results for draining liquid water films clearly present the coupling effects of heat and mass transfer. Excellent comparisons between the ENS and CFD calculation results support the reliability and accuracy of the dynamic water film model in GASFLOW-MPI code which provides an efficient way to analyze PCCS in 3-D full scale advanced light water reactors.

Representations over the Earth’s shape and the process of day and night from Nahua indigenous schoolchildren / Representaciones sobre la forma de la Tierra y del proceso día y noche en niños de escuelas indígenas Nahuas

This research presents the way in which children from a Nahua indigenous community build representations of the Earth’s shape, as well as the process that causes day and night. Concepts from school and local culture were studied. For the first case, a questionnaire was applied to 331 children, out of which 38 children were then interviewed on the topics from the questionnaire. For the cultural ideas, three teachers from the region and 30 children from the sample were interviewed. The results show that the representations depend on the form of questioning and the existence of three models: a flat structure with a celestial dome and mechanisms that hide or remove the Sun or the Moon in order to create day and night; a spherical structure with a surrounding sky, where the Sun and Moon rise and set; and a transitional model with a hollow sphere, flat surface and celestial dome. Cultural ideas do not appear to have any influence over these models, probably due to a loss of the community’s cosmogonic knowledge and the age of the children.

Numerical and Experimental Study of an Under-Ground Water Reservoir, Cistern

This article presents experimental and numerical study of an under-ground water reservoir (cistern) during six months operation in a semi-arid region. The cistern with one dome, four windcatchers and a water reservoir is located in Lar, a hot arid city at south of Iran. Outdoor and indoor air temperature and humidity, water temperature in three depths and dome surface temperature were measured using a data logging system. The results show that the average air humidity inside the cistern was almost constant during the experiments but its slight variation during a day follows inside air temperature changes. The inside air temperature was always lower than the ambient temperature and inside and outside average air temperature difference was about 6 °C. The difference was slightly higher in the hot seasons. The water reservoir was also modeled in 2D, axisymmetric and quasi steady numerical simulation for six months of operation. Highly stratified water temperature distribution was observed in the numerical results as well as the experimental measurements.

Columellar Reconstruction: A New Technique for Median Cleft Lip Repair.

Median cleft lip (MCL), failure of the fusion of the medial nasal prominences in the midline resulting in vertical cleft through the center of the upper lip, can be repaired by various columellar reconstruction approaches depending on the nature of patient. The main drawback of these surgical techniques is the use of healthy neighboring structures that may compromise the process. In this report, the authors present a new approach for repairing MCL which involves simultaneous columellar reconstruction without damaging any nasal units. Briefly, columella was reconstructed with 2 lateral triangular flaps harvested from both cleft sides. They were sutured together and attached to the ventral surface of the nasal dome at the midline. The procedure was resulted in satisfactory clinical and esthetic outcome suggesting this approach may present a better alternative for this condition.

Aerothermal radiation transfer calculation method from the dome to the detector based on reverse ray tracing

The effect of aerothermal radiation of the optic dome on the signal-to-noise ratio of infrared detection system is becoming a crucial issue when the temperature of optic dome is increases in the high speed incoming flow. The method to calculate the radiated power transfer from the whole dome to the unit of the detector through the optic system according to the inverse ray tracing was proposed. The gradient temperature distribution of the dome surface and the attenuation coefficient of the dome material with the wavelength and the temperature were taken into considered in dome’s thermal radiation calculation. According to the mothed, the simulation software was developed and used to analyze the effect about the radiated power transfer from dome of the example optic system to the detector. Simulation results show that the dome with high temperature generates more noise radiated power on the focus plane, to choose reasonable wavelength band and thickness of the dome is useful to increase the signal-to-noise ratio.

Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

Abstract. Supersaturation often occurs at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high Antarctic Plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic Plateau is presented. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content, even in the case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the Antarctic Plateau are thus likely biased low. The measurements are compared with results from two models implementing cold microphysics parameterizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the two models, leaving much room for model improvement. This is unlikely to strongly affect estimations of surface sublimation because supersaturation is more frequent as temperature is lower, and moisture quantities and thus water fluxes are small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high-altitude cirrus clouds in meteorological and climate models.

Novel Directional Blanket Covering Method for Surface Curvature Analysis at Different Scales and Directions

The curvature of surface topography is quantified in this study using a newly developed directional blanket covering curvature (DBCC) method. The novel method addresses a long-standing problem of a measurement of a local surface curvature at individual scales and directions. The curvature data are obtained using the first and second derivations of the quadratic polynomial fitted to the local surface profile extracted from the surface height image data at individual scale and direction. The range of scales is set between an instrument spatial resolution and 1/10 of the image shortest size. Using the surface curvature data, three parameters, i.e. curvature, peak and valley dimensions, are calculated as the slopes of lines fitted to data point subsets of log–log plots of surface areas (differences between dilated and eroded surface curvature matrices) against scales of calculation. The dimensions quantify directional changes in the overall curvature and the curvature of peaks and valleys at individual scales. The scale corresponds to the centre of the subset. A flat surface criterion based on the surface areas was also proposed. Using the criterion, a flat surface was identified in computer images of dome, corrugated plate and fractal surface. The DBCC method was applied to computer-generated fractal surfaces with increasing curvature complexity, sine waves with decreasing curvature at single scale and microscope images of isotropic (sandblasted) and anisotropic (ground) surfaces of titanium plates. Results showed that the method is accurate in the measurement of surface curvature and the detection of minute changes occurring in the curvature of real surfaces over a wide range of scales.

Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

AbstractThe surface deformation field measured at volcanic domes provides insights into the effects of magmatic processes, gravity‐ and gas‐driven processes, and the development and distribution of internal dome structures. Here we study short‐term dome deformation associated with earthquakes at Mount St. Helens, recorded by a permanent optical camera and seismic monitoring network. We use Digital Image Correlation (DIC) to compute the displacement field between successive images and compare the results to the occurrence and characteristics of seismic events during a 6 week period of dome growth in 2006. The results reveal that dome growth at Mount St. Helens was repeatedly interrupted by short‐term meter‐scale downward displacements at the dome surface, which were associated in time with low‐frequency, large‐magnitude seismic events followed by a tremor‐like signal. The tremor was only recorded by the seismic stations closest to the dome. We find a correlation between the magnitudes of the camera‐derived displacements and the spectral amplitudes of the associated tremor. We use the DIC results from two cameras and a high‐resolution topographic model to derive full 3‐D displacement maps, which reveals internal dome structures and the effect of the seismic activity on daily surface velocities. We postulate that the tremor is recording the gravity‐driven response of the upper dome due to mechanical collapse or depressurization and fault‐controlled slumping. Our results highlight the different scales and structural expressions during growth and disintegration of lava domes and the relationships between seismic and deformation signals.

Basic geometry and aberration characteristics of conicoidal conformal domes.

This paper investigated the geometry and aberration characteristics of conicoidal conformal domes. First, on the basis of previous research, we got the expression that was suitable for describing the external surface of the conicoidal conformal dome. Based on the theory of differential geometry, this paper first proved that the Dupin index line of a quadric surface was an ellipsoid and the radius of curvature had extreme values in the meridian plane and sagittal plane. Then the uniform formulas of curvature which were suitable for ellipsoid, paraboloid, and hyperboloid were deduced in the meridian plane and sagittal plane, respectively. Meanwhile, the angle between the axis of imaging systems and the surface normal was calculated. With the help of computers, the plots of curvature differences and the angle in the case of different edge slopes, fineness ratios, and the locations of the rotational center were obtained. Finally, we analyzed the Zernike polynomial coefficients of Z4, Z5, and Z8, which represent defocus, astigmatism and coma, respectively for the model established in CODE V. The research indicates that the dynamic ranges of defocus, astigmatism, and coma increase with the growing of edge slopes and fineness ratios, but have little change with the variation of the rotational center positions. Moreover, the curves of Z5 and Z8 have turning points, and the curves of curvature differences and angle difference are only similar to the curves of Z5 and Z8 when the look angle changes after the turning point. For the look angle changing from zero to the turning point, the curves of Z5 and Z8 change rapidly. This is mainly caused by the significant variations of the symmetry of the conformal dome participating in imaging. Therefore, the aberrations with small scanning angles should be given more attention when designing the conformal systems.

Investigation and modelling of the turbulent wall pressure fluctuations on the bulbous bow of a ship

For the effective operation of sonar systems mounted inside the bulb of fast ships, it is important to reduce all the possible noise and vibration sources that radiate noise and interfere with sonar sensor response. In particular, pressure fluctuations induced by turbulent boundary layers on the sonar dome surface represent the major source of self-noise for on-board sensors. Reliable calculations of structural vibrations and noise radiated inside the dome require valid statistical descriptions of wall pressure fluctuations beneath the turbulent boundary layer. Previous research about wall pressure fluctuations deals with equilibrium turbulent boundary layers on flat plates in zero pressure gradient flow, for which scaling laws for power spectral densities and empirical models for the cross spectral densities are well established. On the contrary, turbulent boundary layers on bulbous bow exhibit the combined effects of three-dimensionality, streamline and spanwise curvatures and pressure gradients. In order to collect information about realistic configurations, wall pressure fluctuations were measured in an experimental campaign performed in a towing tank; data were collected at two different locations along a large scale model of a ship bulb and their spectral characteristics were investigated in terms of auto and cross spectral densities. Mean flow parameters of the boundary layer, required in the analysis, were obtained by a finite volume code that solves the Reynolds Averaged Navier Stokes Equations. The applicability of classical scaling laws for pressure spectra on zero pressure gradient flat plate was investigated, together with the spatial characterization of the wall pressure fluctuations in the space-frequency domain; parameters of some semi-empirical models available in the scientific literature were tuned to fit the measured pressure field.

Talar dome detection and its geometric approximation in CT: Sphere, cylinder or bi-truncated cone?

ObjectiveThe purpose of our study is to give a relatively objective definition of talar dome and its shape approximations to sphere (SPH), cylinder (CLD) and bi-truncated cone (BTC). Materials and methodsThe “talar dome” is well-defined with the improved Dijkstra’s algorithm, considering the Euclidean distance and surface curvature. The geometric similarity between talar dome and ideal shapes, namely SPH, CLD and BTC, is quantified. 50 unilateral CT datasets from 50 subjects with no pathological morphometry of tali were included in the experiments and statistical analyses were carried out based on the approximation error. ResultsThe similarity between talar dome and BTC was more prominent, with smaller mean, standard deviation, maximum and median of the approximation error (0.36±0.07mm, 0.32±0.06mm, 2.24±0.47mm and 0.28±0.06mm) compare with fitting to SPH and CLD. In addition, there were significant differences between the fitting error of each pair of models in terms of the 4 measurements (p-values<0.05). The linear regression analyses demonstrated high correlation between CLD and BTC approximations (R2=0.55 for median, R2>0.7 for others). Color maps representing fitting error indicated that fitting error mainly occurred on the marginal regions of talar dome for SPH and CLD fittings, while that of BTC was small for the whole talar dome. ConclusionThe successful restoration of ankle functions in displacement surgery highly depends on the comprehensive understanding of the talus. The talar dome surface could be well-defined in a computational way and compared to SPH and CLD, the talar dome reflects outstanding similarity with BTC.

The effects of natural and mixed convection on heat transfer across adjacent micro-channels, in extreme pressure and temperature conditions

This abstract summarizes a mainly experimental investigation of heat transfer across an insulation pack specimen used to protect the upper surface of the Hot Box Dome of an advanced gas cooled nuclear reactor from the hot gas above it, under actual operating conditions. The pack consists of multiple stainless steel layers forming narrow channels, less than 1mm wide between them. The facility developed, can operate at pressures of 40bar, temperature differences across the insulation pack of up to 500°C, with and without flow through the pack channels and at horizontal and inclined orientations. Measurements led to the calculation of the effective thermal conductivity and also the mapping of the temperature variation across the pack for a range of flow rates, and also for angles to the horizontal of up to 30°. The effective conductivity data show how, under these extreme pressure and temperature conditions, the rate at which thermal energy is transferred to the lower, cold side, of this multi-channel pack, depends on the Rayleigh and Reynolds numbers at different angles of inclination. The corresponding local temperature measurements advance understanding of the local thermal characteristics and suggest the presence of strong flow structures. The most striking finding is the strong influence of buoyancy for all flow rates investigated, even for the horizontal cases. Tests at inclined orientations suggest the presence of flow reversal. Complementary conjugate heat transfer numerical analysis, using a simplified two-dimensional representation of the pack, has also been carried out. For the inclined case the computed flow features are consistent with those suggested by the local temperature data.

Conformal dome aberration correction by designing the inner surface

The ray transmission models of optical domes were established, and the characteristics of the rays while passing through a hemispherical dome and a conformal dome were comparatively analysed. Acquiring the minimum deviated angles from the inner surface of the conformal dome was then determined to be the designing goal for reducing the dynamic aberrations. Based on this, the inner surface of the conformal dome was optimized and thus, the dynamic aberrations were reduced. Finally, a completely cooled conformal optical system was designed. The results show that the optical system have produced good imaging quality within all the fields of regard, which further illustrates that designing the inner surface of a conformal dome is an effective method for aberration correction.