Buoyancy Measurements Research Articles

Experimental Measurements of Buoyancy Induced Flow in Rotating Cavities Under High Reynolds Number Conditions

Experimental Measurements of Buoyancy Induced Flow in Rotating Cavities Under High Reynolds Number Conditions

Academic Buoyancy Measurements of First Year Engineering Students at the University of Saskatchewan

As part of program evaluation and continuous improvement, the University of Saskatchewan deployed a survey across the common Re-Engineered First-Year (REFY) program in September 2022, and collected just over 300 responses. This survey included four questions developed by Martin and Marsh [3] to measure academic buoyancy, which these authors define as the ability to cope with everyday academic setbacks. In this study, the highest buoyancy question score (slightly positive) referred to dealing with setbacks, and the lowest (slightly negative) referred to the ability to deal with stress. Statistical analyses show a correlation between the responses to the two buoyancy questions related to stress, as well as between the responses to the two buoyancy questions related to setbacks. There is a statistically significant difference in all academic buoyancy scores between male and female respondents (male scores are higher). Buoyancy scores for students participating in high-performance competitive sports also tended to be higher than those in recreational sport activities. Members of clubs also tended to have higher scores than students engaged in other extra-curricular activities.

Understanding the Spatiotemporal Variability of Tropical Orographic Rainfall Using Convective Plume Buoyancy

Abstract Mechanical forcing by orography affects precipitating convection across many tropical regions, but controls on the intensity and horizontal extent of the orographic precipitation peak and rain shadow remain poorly understood. A recent theory explains this control of precipitation as arising from modulation of lower-tropospheric temperature and moisture by orographic mechanical forcing, setting the distribution of convective rainfall by controlling parcel buoyancy. Using satellite and reanalysis data, we evaluate this theory by investigating spatiotemporal precipitation variations in six mountainous tropical regions spanning South and Southeast Asia, and the Maritime Continent. We show that a strong relationship holds in these regions between daily precipitation and a measure of convective plume buoyancy. This measure depends on boundary layer thermodynamic properties and lower-free-tropospheric moisture and temperature. Consistent with the theory, temporal variations in lower-free-tropospheric temperature are primarily modulated by orographic mechanical lifting through changes in cross-slope wind speed. However, winds directed along background horizontal moisture gradients also influence lower-tropospheric moisture variations in some regions. The buoyancy measure is also shown to explain many aspects of the spatial patterns of precipitation. Finally, we present a linear model with two horizontal dimensions that combines mountain wave dynamics with a linearized closure exploiting the relationship between precipitation and plume buoyancy. In some regions, this model skillfully captures the spatial structure and intensity of rainfall; it underestimates rainfall in regions where time-mean ascent in large-scale convergence zones shapes lower-tropospheric humidity. Overall, these results provide new understanding of fundamental processes controlling subseasonal and spatial variations in tropical orographic precipitation.

Academic Buoyancy: Overcoming Test Anxiety and Setbacks

High levels of test anxiety can be damaging for academic achievement, wellbeing, and mental health. It is important, therefore, to consider those psychological attributes that may offer protection against the development of test anxiety and its negative consequences, thereby contributing to a potential positive future life trajectory. Academic buoyancy, the ability to respond effectively to academic pressures and setbacks, is one such attribute that offers protection from high test anxiety. We begin by defining test anxiety and a brief review of the literature to consider the harmful nature of test anxiety. This is followed by a definition of academic buoyancy and brief review of the literature to consider the beneficial character of academic buoyancy. Next, we describe the Self-Regulatory Executive Function model of test anxiety and consider the mechanisms and processes by which academic buoyancy exerts beneficial effects on test anxiety. The paper concludes with a consideration of critical issues for the conceptualisation and measurement of academic buoyancy, arising from the synergies, connections, and relations, theorised with test anxiety, and how these may inform future studies.

Manufacturing of scaffolds with interconnected internal open porosity and surface roughness.

Manufacturing of three-dimensional scaffolds with multiple levels of porosity are an advantage in tissue regeneration approaches to influence cell behavior. Three-dimensional scaffolds with surface roughness and intra-filament open porosity were successfully fabricated by additive manufacturing combined with chemical foaming and porogen leaching without the need of toxic solvents. The decomposition of sodium citrate, a chemical blowing agent, generated pores within the scaffold filaments, which were interconnected and opened to the external environment by leaching of a water-soluble sacrificial phase, as confirmed by micro-CT and buoyancy measurements. The additional porosity did not result in lower elastic modulus, but in higher strain at maximum load, i.e. scaffold ductility. Human mesenchymal stromal cells cultured for 24 h adhered in greater numbers on these scaffolds when compared to plain additive-manufactured ones, irrespectively of the scaffold pre-treatment method. Additionally, they showed a more spread and random morphology, which is known to influence cell fate. Cells cultured for a longer period exhibited enhanced metabolic activity while secreting higher osteogenic markers after 7 days in culture. STATEMENT OF SIGNIFICANCE: Inspired by the function of hierarchical cellular structures in natural materials, this work elucidates the development of scaffolds with multiscale porosity by combining in-situ foaming and additive manufacturing, and successive porogen leaching. The resulting scaffolds displayed enhanced mechanical toughness and multiscale pore network interconnectivity, combined with early differentiation of adult mesenchymal stromal cells into the osteogenic lineage.

Temporal Evolution of the Swell and Magmatic Fluxes Along the Louisville Hotspot Chain

AbstractHawaii and Louisville are the two long‐lived hotspot chains in the Pacific basin. Characterizing the swell flux, Qs, a measure of the plume buoyancy, and the flux of the magmatic material accumulated along the chain, Qm, brings important constraints on the plumes' temporal evolution and on their interaction with the lithosphere. Numerous studies focus on the temporal evolution of the Hawaiian chain, but no study investigates the temporal evolution along the Louisville chain. In the present study we constrain the temporal evolution of the swell and magmatism fluxes along the Louisville chain, from volcano ages and bathymetry data. The overall Louisville magmatism flux appears nearly constant, that is, Louisville plume activity has exhibited remarkably little variation over the past 30 m.y., in agreement with geochemical data. These results are also in agreement with recent studies along Hawaii, which show that the Qm increase is due to plume migration toward a more fertile mantle reservoir. This means that, in general, long term variations in Qm relate to variations in the deep source of the plume. Along Louisville, we find short‐term variations occurring with a periodicity of ∼5–10 m.y. in both Qm and Qs, similar to the short‐term variations observed along Hawaii by former studies. As these variations occur along hotspot chains associated with either a heterogenous or homogeneous chemical signature, they must be created by shallow phenomena. The tilt of the plume conduit by large‐scale mantle advection is our preferred model, as it can account for both the geophysical and geochemical observations.

Buoyancy and hydrostatic balance in a West Indian Ocean coelacanth Latimeria chalumnae

BackgroundBuoyancy and balance are important parameters for slow-moving, low-metabolic, aquatic organisms. The extant coelacanths have among the lowest metabolic rates of any living vertebrate and can afford little energy to keep station. Previous observations on living coelacanths support the hypothesis that the coelacanth is neutrally buoyant and in close-to-perfect hydrostatic balance. However, precise measurements of buoyancy and balance at different depths have never been made. ResultsHere we show, using non-invasive imaging, that buoyancy of the coelacanth closely matches its depth distribution. We found that the lipid-filled fatty organ is well suited to support neutral buoyancy, and due to a close-to-perfect hydrostatic balance, simple maneuvers of fins can cause a considerable shift in torque around the pitch axis allowing the coelacanth to assume different body orientations with little physical effort.ConclusionsOur results demonstrate a close match between tissue composition, depth range and behavior, and our collection-based approach could be used to predict depth range of less well-studied coelacanth life stages as well as of deep sea fishes in general.

Buoyancy and Hydrostatic Balance in The West Indian Coelacanth Latimeria chalumnae

Buoyancy and balance are important parameters for static or slow moving low‐metabolic aquatic organisms. The extant coelacanths, a single genus (Latimeria) consisting of two species living at moderate depths (100 – 400 m) in the Western Indian Ocean and off Indonesia and representing an ancient group of lobe finned fishes dating back to the early Devonian (410 Myr), have among the lowest metabolic rates of any living vertebrate, and thus would be predicted to expend precious little energy to maintain buoyancy and balance. Previous observations on living coelacanths support the hypothesis that the coelcanth is neutrally buoyant and is in close to perfect hydrostatic balance in any body posture. Likewise, point‐by‐point measurements of tissue composition have shown a generally high lipid content of coelacanth tissue supporting neutral buoyancy without a gas filled bladder as found in other sarcopterygians (lungs) and in many actinopterygians (swim bladder). However, precise measurements of buoyancy and hydrostatic balance at different depths have never been made in the coelacanth. Here we show using non‐invasive imaging that buoyancy of the coelacanth closely matches its depth distribution and a close‐to‐perfect balance can be used by the animal to change body posture with little effort. We found that the lipid filled “fatty organ” of the coelacanth is well adapted to support neutral buoyancy and simple maneuvers of fins can cause a considerable shift in torque around the pitch axis. This allows the coelacanth to assume and remain in any body posture like horizontal orientation, headstand or tail stand with little physical effort. Our results demonstrate a close match between tissue composition in the extant coelacanth, depth range and behavior (e.g. effortless vertical drift hunting with the electrosensitive rostral organ in close contact with the substrate). We anticipate our non‐invasive technique of mapping tissue components to be a starting point for more sophisticated models of buoyancy and hydrostatic balance in aquatic vertebrates in general. Specifically, we suggest the technique can be used on the few late term and juvenile coelacanth specimens in existence to predict the most likely habitat depth of the juvenile life stage which is currently unknown.

Scaling CO2 convection in confined aquifers: Effects of dispersion, permeability anisotropy and geochemistry

Solubility trapping of carbon dioxide (CO2) in deep saline aquifers is considered an effective mechanism of carbon storage. The dissolution of CO2 in aquifer brine may result in gravitational instability, which triggers convective mixing (similar to the well-known Rayleigh–Bénard convection problem). The process starts with the diffusion of CO2 into the brine, followed by the onset of convection (tc), which may be followed by the constant-flux regime, F=Fc, where F is the dissolution flux. Scaling tc and Fc with characteristic measures (such as Rayleigh number as a measure of buoyancy to diffusive driving forces) is important for the characterization of CO2 injection at a large scale. Previously, natural complexities such as hydrodynamic dispersion, permeability anisotropy and geochemical interactions have been neglected in the scaling relations of convective mixing. This work explores the effects of such simplifications on the scaling relations of convective mixing using high-resolution 2D numerical simulations. Our results provide new insights from revisiting the convective mixing scaling. We show that the Sherwood number (Sh) depends on the domain height in the presence of the hydrodynamic dispersion. In line with such findings, we show that Sh-Rayleigh scaling prefactor is directly related to longitudinal dispersivity (αL). Moreover, we show that increasing the permeability in each direction is beneficial for the process by decreasing convection onset time (tc) and increasing the dissolution flux (F). Smaller permeability anisotropy ratio (defined as the ratio of vertical to horizontal permeability, ℘=Kz/Kx) results in earlier onset time and higher dissolution flux, which scales with ℘0.54 and ℘−0.21 compared to convection–diffusion, respectively. Finally, our simulation results show that earlier tc and higher F are expected due to carbonate geochemical reactions. The scaling relations of convective mixing in deep saline aquifers guide prioritization and selection of appropriate aquifers for geological CO2storage and designing efficient injection schemes.

Buoyancy of post‐fertilised Dissostichus mawsoni eggs and implications for early life history

AbstractGametes from gravid Antarctic toothfish (Dissostichus mawsoni) were combined in vitro and buoyancy measurements were made on fertilised eggs during early development. Eggs were strongly positively buoyant, indicating that they would ascend quickly in the water column and reside near or in association with the underside of sea ice, which covers most of the spawning habitat during winter. An association with sea ice may provide: protection from the turbulence of ice‐free surface waters, a mechanism that modifies the velocity of advection by surface currents, and a habitat with a concentrated planktonic food source during spring months. An association with sea ice would also create spatial differences in egg advection patterns for eggs produced spanning a large geographic area. The effects of climate change on sea ice formation and melting patterns, or fishery‐induced changes in the spatial density of adults could then influence juvenile advection patterns and influence survival.

Vertically distributed wall sources of buoyancy. Part 2. Unventilated and ventilated confined spaces

Abstract

Nondestructive Determination of Fruit Surface Area Using Archimedean Buoyancy

Estimates of fruit surface area are often required in physiological and technological studies. The objective was to establish a procedure to accurately quantify the fruit surface area based on Archimedean buoyancy measurements. The setup comprised a fixed, linear stepper motor mounted with its spindle vertical and aligned directly above the pan of an electronic balance. A fruit was clamped to the motor spindle and a beaker of water rested on the balance pan. When the motor was activated, the fruit was progressively immersed, stepwise, in the water. Each vertical displacement step increased the buoyant upthrust on the fruit, which was opposed by a corresponding increase in the downthrust on the balance. Pairs of the step displacement length (mm) and corresponding buoyancy increment (g) values were recorded in an MS Excel (Microsoft, Redmond, WA) spreadsheet using Arduino components. Each displacement step immersed another “virtual slice” of the fruit in the water. From each pair of known displacement–buoyancy measurements, the volume (mL) of that slice could be calculated with high precision based on the known density of the liquid (g·mL−1). With the fruit orientated so that its morphological “long” axis was vertical, for most fruitcrop species, the slice can be assumed to have a circular cross-section. Hence, the slice can be analyzed geometrically as a truncated cone of known height (mm) and known volume (mL). Therefore, the surface area of its outer face is calculable. The surface area of the whole fruit was calculated as the cumulative total of the surface areas of all steps (virtual slices). The procedure was evaluated and calibrated using stainless-steel spheres in place of the fruit. However, the measured surface area was slightly greater than that calculated for a sphere. The calculated and measured areas did not differ by more than 1.7%. The surface area determinations were highly reproducible (cv = 0.95%). The magnitude of the displacement steps affected the variability of the surface area measurements. Increasing the step displacements decreased the measurement variability, but there were no significant effects on the surface area measurements of the surface tension of the liquid or of the wettability of the surface of the fruit or the stainless-steel subject. Using stainless-steel spheres (diameter, 5–60 mm) or rubber truncated cones (mean diameter, 8–45 mm) revealed an excellent agreement between the measured and calculated surface areas. Using tomatoes, grapes, blueberries, and strawberries, the measured surface areas were in excellent agreement with those calculated from the fruit dimensions and appropriate geometrical assumptions. The results demonstrate that the surface areas of fruit with approximately circular cross-sections normal to their morphological axes can be determined with high accuracy and reproducibility using Archimedean buoyancy.

The buoyancy-based biotope axis of the evolutionary radiation of Antarctic cryonotothenioid fishes

In the absence of any prior comprehensive analysis, I evaluate divergence along the biotope axis in the habitat stage of the evolutionary radiation of Antarctic cryonotothenioids. I utilize the available percentage buoyancy (%B) measurements as habitat proxies for recognition of the pelagic, semipelagic, demersal, and benthic biotopes that include, respectively, 5%, 10%, 73%, and 12% of the 59 species and 1749 specimens in the study. The majority of species retain the ancestral demersal biotope of Eleginops maclovinus, and this probably enhances ecological plasticity. Divergence into the pelagic biotope is the most distinctive organismal feature of the radiation and, although only 5% of species are pelagic, this biotope is not depauperate in global comparisons. Pelagic or potentially pelagic species are Dissostichus mawsoni, D. eleginoides, Pleuragramma antarctica, Aethotaxis mitopteryx, and Gvozdarus svetovidovi. Small ontogenetic changes in %B with growth are typical; however, this is extensive in D. mawsoni, a species with the potential to transition through benthic to pelagic biotopes over ontogeny. Occupation of the pelagic biotope by large D. mawsoni may be impermanent as it is lipid-dependent, a contingency reliant on the availability of P. antarctica as prey. In unusual conditions, the specialized sacs of P. antarctica can also yield their lipid for metabolism with possible loss of buoyancy. Pelagic species are inordinately important in the food web. In the southwestern Ross Sea a guild of large mammalian and avian predators, which includes D. mawsoni, is reliant on lipid-rich, energy-dense cryonotothenioid prey. This includes asymmetrical intraguild predation on D. mawsoni, with P. antarctica as a basal resource for the guild.

Deep Convective Organization, Moisture Vertical Structure, and Convective Transition Using Deep-Inflow Mixing

Abstract It is an open question whether an integrated measure of buoyancy can yield a strong relation to precipitation across tropical land and ocean, across the seasonal and diurnal cycles, and for varying degrees of convective organization. Building on previous work, entraining plume buoyancy calculations reveal that differences in convective onset as a function of column water vapor (CWV) over land and ocean, as well as seasonally and diurnally over land, are largely due to variability in the contribution of lower-tropospheric humidity to the total column moisture. Over land, the relationship between deep convection and lower-free-tropospheric moisture is robust across all seasons and times of day, whereas the relation to boundary layer moisture is robust for the daytime only. Using S-band radar, these transition statistics are examined separately for mesoscale and smaller-scale convection. The probability of observing mesoscale convective systems sharply increases as a function of lower-free-tropospheric humidity. The consistency of this with buoyancy-based parameterization is examined for several mixing formulations. Mixing corresponding to deep inflow of environmental air into a plume that grows with height, which incorporates nearly equal weighting of boundary layer and free-tropospheric air, yields buoyancies consistent with the observed onset of deep convection across the seasonal and diurnal cycles in the Amazon. Furthermore, it provides relationships that are as strong or stronger for mesoscale-organized convection as for smaller-scale convection.

Continual refined isothermal adsorption of pure illite in shale with gravimetric method

Conventional isothermal adsorption measurement (CM) and continual refined isothermal adsorption measurement (CRM) were used to investigate the methane adsorption of illite. The main differences between these two measurements are the repeated pressure during the buoyancy measurement and adsorption measurement in CRM. The results show that the adsorption isotherms of illite with CM and CRM were different, depending mainly on sample volumes calculated with various maximum buoyancy measurement pressures. The dynamic of sample volumes during the buoyancy measurement can be divided into 3 different stages. The rapid filling of helium at lower pressure stages results in an initial increase of the sample volume. With increasing test pressure, the shrinking interlayer space and decreased interparticle void volume in illite that can be compressed leading to the subsequent reduction in sample volume. Finally, when the test pressure exceeds to 5MPa, the sample volume presents stable. Combined with the volume of adsorbed phase CH4, the absolute volume that would be used to calculate the methane adsorption can be acquired. According to the mass balance equation, the modified and believable methane adsorption of illite was calculated.

Experimental Study of the Relationship Between Particle Size and Methane Sorption Capacity in Shale.

The amount of adsorbed shale gas is a key parameter used in shale gas resource evaluation and target area selection, and it is also an important standard for evaluating the mining value of shale gas. Currently, studies on the correlation between particle size and methane adsorption are controversial. In this study, an isothermal adsorption apparatus, the gravimetric sorption analyzer, is used to test the adsorption capacity of different particle sizes in shale to determine the relationship between the particle size and the adsorption capacity of shale. Thegravimetric method requires fewer parameters and produces better results in terms of accuracy and consistency than methods like the volumetric method. Gravimetric measurements are performed in four steps: a blank measurement, preprocessing, a buoyancy measurement, and adsorption and desorption measurements. Gravimetric measurement is presently considered to be a more scientific and accurate method of measuring the amount of adsorption; however, it is time-consuming and requires a strict measuring technique. A Magnetic Suspension Balance (MSB) is the key to verify the accuracy and consistency of this method. Our results show that adsorption capacity and particle size are correlated, but not a linear correlation, and the adsorptions in particles sieved into 40 - 60 and 60 - 80 meshes tend to be larger. We propose that the maximum adsorption corresponding to the particle size is approximately 250 µm (60 mesh) in the shale gas fracturing.

Predictors and Consequences of Academic Buoyancy: a Review of Literature with Implications for Educational Psychological Research and Practice

Existing studies have focused on examining how academic buoyancy or the ability to cope with day-to-day challenges in school may be linked to academic functioning. This review article reported the current state of the academic buoyancy literature in the educational contexts. Findings from previous investigations on the theorizing, measurement, predictors, and consequences of academic buoyancy are summarized. Research gaps are also identified to proposed future research directions. Results on the association of academic buoyancy with positive academic functioning and well-being outcomes are used to draw practical implications for school psychologists and guidance counselors in the school settings.

Comparison of measured and simulated performance of natural displacement ventilation systems for classrooms

Children spend the majority of their weekdays in classrooms that often have low indoor air quality and limited financial resources for the initial and running costs of mechanical ventilation systems. Designing effective natural ventilation (NV) systems in schools is difficult due to the intense use of the classroom spaces and the dependence of NV on building geometry and outdoor conditions. Building thermal and airflow simulation tools are fundamental to predict NV system performance in the design phase. These predictions of these tools must be validated (preferably with data from real buildings). This paper presents a set of detailed measurements of buoyancy driven natural DV systems of three classrooms located in two buildings in Lisbon (Portugal). The rooms are located in two educational buildings, a kindergarten and a university, and have different buoyancy driven natural DV systems (with and without chimneys). The experimental measurements are used to validate a three-node DV model implemented on the open-source thermal building simulation software EnergyPlus. The validation results show that the building thermal simulation model tested is able to predict bulk airflow rate with an average error of 16%. In addition, a good agreement is also obtained for the vertical temperature prediction: an average error of 4% corresponding (average deviation of 0.7°C). Analysis of the kindergarten rooms results revealed, that as expected, increasing chimney height from 1 to 4m has a significant positive impact in NV system performance. The performance of natural DV systems depends on the number of thermal plumes in the room. For the same sensible heat load, increasing the number of plumes lowers the average occupied zone air temperature and increases the bulk airflow rate. In light of the complexity of the cases tested, NV with uncontrolled boundary conditions, the results of the comparisons performed between measurements and simulations should contribute to increase confidence in the use of EnergyPlus to simulate buoyancy driven natural DV systems.

Determining the Mechanical Characteristics of Microspheres in Compression

The methodology to determine the compressive strength of microspheres is improved. It is validated by buoyancy measurements. It is demonstrated that the tangent circle method allows determining the point of maximum curvature of the stress–strain curve of microspheres. The optimal ratio of the height of microspheres to the diameter of the die mold (H/D) is determined. Curves of variation of the elastic modulus and absorbed strain energy with the maximum cyclic stress are plotted.

On instability and mixing on the UK Continental Shelf

The stability of stratified flows at locations in the Clyde, Irish and Celtic Seas on the UK Continental Shelf is examined. Flows are averaged over periods of 12–30min in each hour, corresponding to the times taken to obtain reliable estimates of the rate of dissipation of turbulent kinetic energy per unit mass, ε. The Taylor–Goldstein equation is solved to find the maximum growth rate of small disturbances to these averaged flows, and the critical gradient Richardson number, Ric. The proportion of unstable periods where the minimum gradient Richardson number, Rimin, is less than Ric is about 35%. Cases are found in which Ric < 0.25; 37% of the flows with Rimin < 0.25 are stable, and Ric < 0.24 in 68% of the periods where Rimin < 0.25. Marginal conditions with 0.8 < Rimin/Ric < 1.2 occur in 30% of the periods examined. The mean dissipation rate at the level where the fastest growing disturbance has its maximum amplitude is examined to assess whether the turbulence there is isotropic and how it relates to the wave–turbulence boundary. It is concluded that there is a background level of dissipation that is augmented by instability; instability of the averaged flow does not account for all the turbulence observed in mid-water. The effects of a horizontal separation of the measurements of shear and buoyancy are considered. The available data do not support the hypothesis that the turbulent flows observed on the UK shelf adjust rapidly to conditions that are close to being marginal, or that flows in a particular location and period of time in one sea have stability characteristics that are very similar to those in another.