Circular Chamber Research Articles

Double-tuning the inlet and outlet extension lengths of a family of straight-flow expansion chamber mufflers for broadband attenuation

This work presents a generalized end-correction expression for double-tuning the extensions of the concentric inlet and concentric/offset outlet ports of a family of straight-flow circular and elliptical expansion chamber mufflers as a function of geometrical parameters, which include the wall-thickness, ratio of chamber-to-port diameter, aspect-ratio, and the offset distance along the major-axis. To this end, first, the transmission loss (TL) performance of configurations with non-tuned extensions given by half and quarter chamber lengths at the inlet and outlet, respectively, was determined using 3-D FEA, which accounted for the multi-dimensional acoustic field at area-discontinuities. The effective lengths of the quarter-wave resonators at the inlet and outlet and the corresponding end-corrections were computed from the first and second resonance frequency peaks, respectively. The 3-D FEA showed that by considering geometric length equal to the effective inlet and outlet length, three-fourths of the troughs in the TL spectrum were nullified, thereby delivering a broadband attenuation. The 3-D effects were incorporated into the 1-D model through end-correction lengths. Parametric studies were conducted to examine the variation of end-corrections with different geometrical parameters, while the accuracy of the generalized end-correction expression was demonstrated by comparison against previous results.

Enhancing mixing efficiency of a circular electroosmotic micromixer with cross-reciprocal electrodes

Enhancing mixing efficiency in microscale processes for sensitive biomedical, pharmaceutical, and chemical applications is crucial, particularly when operating under low-velocity constraints. This study presents a comprehensive investigation into the impact of various factors on microfluidic mixing within a circular mixing chamber micromixer, utilizing electroosmotic principles. The governing equations are solved numerically using the finite element technique-based solver. This research examines the effects of microchamber diameter (D), inlet velocity (uo), alternating current (AC) voltage amplitude (ϕo), and AC frequency (f) on fluid mixing dynamics. Several key findings are noted from this study. The reduction of the circular microchamber diameter decreases the linear distance between cross-reciprocally placed microelectrodes, resulting in increased electroosmosis force and mixing efficiency. The voltage amplitude within the specified range shows increased mixing efficiency when fluid species are combined at appropriate velocity and AC frequency. The highest mixing efficiency of 98.84% is achieved with the following parameters: flow velocity (uo) of 150 μm/s, AC frequency of 4 Hz, voltage amplitude of 500 mV, and microchamber diameter of 20 μm. At a frequency of 12 Hz and voltage amplitude of 500 mV, the mixing efficiency exceeds 94.66% across a wide range of input velocities (100–200 μm/s), enabling versatile control in microfluidic devices. The nonlinear interaction between electroosmotic flow and microchamber geometry significantly contributes to this enhanced mixing efficiency. These results demonstrate the potential for optimizing microfluidic mixing processes through careful parameter tuning, particularly in applications requiring high efficiency at low flow rates. Thus, this study provides valuable insights for designing more effective microfluidic systems in various scientific and industrial fields.

Experimental study on the failure behavior of rockburst induced by a dynamic disturbance in the circular chamber for deep underground engineering

Rockbursts induced by disturbance loads have become a significant engineering issue. Block specimens featuring a circular chamber structure were designed to investigate the effects of the disturbance frequency on rockbursts. The experiment simulated a series of rockburst failure processes through a disturbance load with four different frequencies by maintaining a constant preset confining pressure. The experimental results showed that an increased disturbance frequency intensifies the shear failure response and enhances the rockburst intensity. Furthermore, the particle image velocity technique was used to calculate the ejection velocity. The results suggested that the initial ejection velocity of fragments during rockburst surged by 253 % as the disturbance frequency was increased from 0.005 Hz to 0.625 Hz. The assessment level of rockburst failure transitions ranged from slight to moderate. These results indicated that an increase in disturbance frequency exacerbated rockburst failures. Two mechanisms were proposed to explain this effect. (i) The increase in disturbance frequency elevates the internal friction angle of rock units, enhancing their ultimate energy storage capacity. (ii) Increased energy input causes the energy storage in rock units to surpass the minimum energy required for rock failure, endowing the fragmented rock mass with greater velocity and leading to more intense rockburst failures. Ultimately, recommendations for early warning of rockburst failure are also provided by discussing the microscopic failure mechanisms of rockburst experiments and the rockburst in situ.

A case study of displacement, stress condition and failure criterion of surrounding rock in deep super-large section double chambers in the Longgu Coal Mine, Shandong, China

To investigate the stability of a super-large section chamber group, an analysis was conducted based on the in-situ geological conditions of a super-large section chamber group utilized as a coal gangue separation system at the Longgu Coal Mine. Field measurement and numerical simulation were employed to analyze the failure area and stress state of the surrounding rock under varying chamber spacings. The results indicate that the extent of the plastic zone significantly expands when the spacing between chambers is less than 2.0 times the chamber width. When the distance between chambers is 1.5 times the chamber width, it results in the rock pillars being entirely within the plastic zone. As the chamber spacing decreases, the tangential stress within the rock pillar range increases. When the chamber spacing is 2.5, 2.0, and 1.5 times the chamber width, the maximum tangential stress is 1.19, 1.46, and 1.18 times that in the case of a single chamber, respectively. Based on the displacement analysis, it was observed that as the distance between the chambers decreases, there is a notable increase in the displacement of the pillar sides and chamber top, indicating a higher risk of collapse. Integrating the plastic area and stress analysis allows for the categorization of the rock pillar area into four sections: the broken area, loose area, stable area, and firm area. Drawing upon the theoretical solution of the plastic zone of a circular chamber and the equivalent radius method, an approximate solution for the plastic zone of a non-circular chamber has been provided. Furthermore, the minimum reasonable spacing between chambers in a super-large section chamber group is provided as a distance criterion for the failure of a double chamber.

Proliferation of SH-SY5Y neuroblastoma cells on confined spaces

Background:Microfluidics offers precise drug delivery and continuous monitoring of cell functions, which is crucial for studying the effects of toxins and drugs. Ensuring proper cell growth in these space-constrained systems is essential for obtaining consistent results comparable to standard Petri dishes. New method:We investigated the proliferation of SH-SY5Y cells on circular polycarbonate chambers with varying surface areas. SH-SY5Y cells were chosen for their relevance in neurodegenerative disease research. Results:Our study demonstrates a correlation between the chamber surface area and SH-SY5Y cell growth rates. Cells cultured in chambers larger than 10 mm in diameter exhibited growth comparable to standard 60-mm dishes. In contrast, smaller chambers significantly impeded growth, even at identical seeding densities. Similar patterns were observed for HeLaGFP cells, while 16HBE14σ cells proliferated efficiently regardless of chamber size. Additionally, SH-SY5Y cells were studied in a 12-mm diameter sealed chamber to assess growth under restricted gas exchange conditions. Comparison with existing methods:Our findings underscore the limitations of small chamber sizes in microfluidic systems for SH-SY5Y cells, an issue not typically addressed by conventional methods. Conclusions:SH-SY5Y cell growth is highly sensitive to spatial constraints, with markedly reduced proliferation in chambers smaller than 10 mm. This highlights the need to carefully consider chamber size in microfluidic experiments to achieve cell growth rates comparable to standard culture dishes. The study also shows that while SH-SY5Y and HeLaGFP cells are affected by chamber size, 16HBE14σ cells are not. These insights are vital for designing effective microfluidic systems for bioengineering research.

Analysis of Circular Chamber Armatures With Different Initial Winding Angles

Analysis of Circular Chamber Armatures With Different Initial Winding Angles

A Study on the Transient Response of Compressed Air Energy Storage in the Interaction between Gas Storage Chambers and Horseshoe-Shaped Tunnels in an Abandoned Coal Mine

This study focuses on the renovation and construction of compressed air energy storage chambers within abandoned coal mine roadways. The transient mechanical responses of underground gas storage chambers under a cycle are analyzed through thermal-solid coupling simulations. These simulations highlight changes in key parameters such as displacement, stress, and temperature within the chamber group during the loading and unloading processes of compressed air energy storage. It is found that within a cycle, the small circular chamber experiences the most significant deformation, with an average peak displacement of 0.24 mm, followed by the large circular chamber and horseshoe-shaped tunnels. The small circular chamber exhibits maximum tensile and compressive stresses. Therefore, special attention in engineering practice should be paid to the long-term safety and stability of small circular tunnels, and the stability of horseshoe-shaped tunnels should be also carefully considered. The findings from this study offer some insights for theoretical support and practical implementation in the planning, design, construction, and operation of high-pressure underground gas storage chambers for compressed air energy storage.

Multidirectional Vortex Micromixer Utilizing a Curved Channel with Variable Cross-Sectional Circular Arc Mixing Chambers

Multidirectional Vortex Micromixer Utilizing a Curved Channel with Variable Cross-Sectional Circular Arc Mixing Chambers

Hydrothermal scenario of buoyancy-driven magnetized multi-walled carbon nanotube-Fe3O4-water hybrid nanofluid flow within a discretely heated circular chamber fitted with fins

This investigation unfolds the hydrothermal changes of magnetized buoyancy-driven multi-walled carbon nanotube (MWCNT)-Fe3O4-water hybrid nanofluidic flow through two centrally placed circular cylinders. Four rectangular T-shaped fins are affixed with the internally placed comparatively small-sized heated cylinder, while the outer cylinder is discretely heated. Four different types of heater-cooler segment arrangements along the outer cylinder periphery are set to execute the investigation. The flow-related leading equations and boundary restrictions are presented and altered to their dimensionless form via suitable similarity transformations. Both nondimensional momentum and energy equations are solved by employing the Galerkin-finite-element technique. Numeric and experimental comparisons are executed to ensure the model’s accuracy. Several streamlines, isotherms, and Nusselt number graphics are revealed to explore the parametric impacts. Results assure accelerated velocity trajectory for Rayleigh numbers, while the flow seems to decelerate for magnetic effect and higher nanoparticle concentrations. Case 1 and Case 3 exhibit higher velocity magnitude and heat transmission out of all four designed cases. Case 1 promotes a 4.68% enhancement in heat transference compared to Case 3 for Rayleigh numbers within the range 104 to 105. Enhanced nanoparticle concentrations assist Case 1 in disclosing 8.13% higher heat transport compared to Case 3. This hydrothermal numeric investigation of natural convective magnetized hybrid nanofluidic inside discretely heated annular chambers might have promising applications in gas turbines, thermal storage devices, heat exchangers, solar receivers, electronic cooling, etc.

Numerical investigation of TiO2-water nanofluid heat transfer in a porous wavy circular chamber with a ┴-shaped heater under magnetic field

The role of natural convection NC in nanofluids is vital to the heat transfer efficiency of various thermal systems, including solar energy devices, HVAC systems, and heat exchangers. This research examines the NC of TiO2-water nanofluid in a porous wavy circular area with a ┴shaped heater under a constant magnetic field. The governed equations may well be solved utilizing the finite element technique, and the impact of various variables, such as the volume fraction of nanofluid (φ), radiation parameter (Rd), Rayleigh number (Ra), aspect ratio (AR), and Hartmann number (Ha), on the heat transfer of the ferrofluid is analyzed. The findings show that amplifying the aspect ratio from 0.3 to 0.5 reduces the local Nusselt number by up to 35%. Additionally, increasing the Ha from 0 to 40 results in a decrease in the maximum streamline by 85%.

First study of continental bioerosion traces on vertebrate remains from the Cretaceous of Algeria

Trace fossils, representing ichnospecies Cubiculum ornatus, C. inornatus, Cubiculum isp., and Cuniculichnus variabilis as well as three indeterminate morphological categories (thin branching grooves A and B, furrows and circular chambers), are here recorded on vertebrate remains from the mid-Cretaceous (lower Cenomanian) of the ‘Continental Intercalary’ deposits in the Gara Samani locality (central Sahara of Algeria). Apart from thin branching grooves (A and B), which are thought to result from root etching, the bioerosion traces recorded on the bones comprise circular chambers and furrows, which represent pupation chambers of scavenging insects, most likely attributed to dermestid beetles. These trace fossils are identified and described for the first time from the Cretaceous of Algeria. They add new data to the trace-fossil assemblages previously reported from other Cretaceous successions of North Africa (e.g., the Kem Kem beds in Morocco). Sedimentological clues indicate a braided fluvial system environment. Taphonomic analysis suggests that the vertebrate remains were most likely subaerially exposed for a prolonged time prior to being transported and finally buried. Therefore, most of the studied borings are likely the result of dermestid beetle larvae feeding on dry bones on dry lands; other borings represent plant etchings produced after the bones were partially covered by, or completely buried, in sediments.

Wave scattering by porous cylinders with inner columns near a vertical wall

This paper studies wave scattering by multiple dual porous circular cylinders in front of a vertical wall. Each cylinder is composed of an outer partially perforated cylindrical shell and an inner impermeable column, and a circular wave-absorbing chamber is formed by the shell and column. An analytical solution to the hydrodynamic problem is developed in the context of potential flow theory. In the solving procedure, the hydrodynamic problem is transformed into an equivalent problem in an open water domain by using the image principle. The whole fluid domain in the equivalent problem is divided into multiple regions, and the velocity potential of the fluid motion in each region is expressed as the Fourier–Bessel series. The effect of the perforated shell on wave motion is considered through a pressure loss condition. The unknown coefficients in the velocity potential are determined by the transmission conditions on the boundaries between adjacent regions. The wave force, wave run-up on the porous cylinders, and the surface elevation near the cylinders are calculated. The analytical results are consistent with published results in several limiting cases. Typical cases are presented to clarify the characteristics of the wave force and wave run-up on the cylinders and discuss the effects of the wall and hydrodynamic interference on the hydrodynamic quantities. Moreover, several feasible applications of dual porous cylinders are discussed by visualizing the distribution of wave amplitude near the structures, and some valuable results are given.

Study on the Periodic Collapse of Suspended Sandstone Interlayer under Coupled Thermo–Hydro–Mechanical Environment

In the process of in situ heat injection mining of coal seams, a circular combustion chamber will gradually be formed. However, for the interlayer coal seam, the interlayer will gradually suspend in the combustion chamber. When the critical distance is reached, the initial collapse and periodic collapse will occur, which will affect the flow field distribution and extraction efficiency of combustion gas. In order to study the initial and periodic collapse steps of interlayer in real-time high temperature and high-pressure thermo–hydro–mechanical (THM) coupling environments, sandstone specimens were collected from the field, and the macroscopic mechanical parameters of sandstone interlayer were tested using a self-developed thermo–hydro–mechanical coupling tester. The mechanical parameters (e.g., triaxial compressive strength, elastic modulus, Poisson’s ratio) of sandstone under different stress conditions were obtained. Then, based on the elastic thin plate theory, the mechanical modeling of the annular sandstone interlayer is carried out and the preceding mechanical parameters are brought into the generated analysis equation. Thus, the periodic collapse step of the suspended circular sandstone interlayer is obtained. The study results show that: (1) the macroscopic physicomechanical parameters of the sandstone interlayer do not vary monotonically with temperature—a slight increase in macroscopic parameters occurs at 400°C; and (2) the periodic caving pace of the sandstone interlayer decreases with the increase in the number of collapses. With the increase of temperature, the periodic caving pace of the sandstone interlayer decreases first, then increases, and then decreases. It gradually decreases with the increase of surrounding pressure. The research results of this paper can provide theoretical guidance and technical support for in situ heat injection mining technology.

Design, Simulation, and Evaluation of Polymer-Based Microfluidic Devices via Computational Fluid Dynamics and Cell Culture "On-Chip".

Organ-on-a-chip (OoC) technology has experienced exponential growth driven by the need for a better understanding of in-organ processes and the development of novel approaches. This paper investigates and compares the flow behavior and filling characteristics of two microfluidic liver-on-a-chip devices using Computational Fluid Dynamics (CFD) analysis and experimental cell culture growth based on the Huh7 cell line. The conducted computational analyses for the two chips showed that the elliptical chamber chip proposed herein offers improved flow and filling characteristics in comparison with the previously presented circular chamber chip. Huh7 hepatoma cells were cultured in the microfluidic devices for 24 h under static fluidic conditions and for 24 h with a flow rate of 3 μL·min-1. Biocompatibility, continuous flow, and biomarker studies showed cell attachment in the chips, confirming the cell viability and their consistent cell growth. The study successfully analyzed the fluid flow behavior, filling characteristics, and biocompatibility of liver-on-a-chip prototype devices, providing valuable insights to improve design and performance and advance alternative methods of in vitro testing.

Numerical Investigation on Cavitation Jet in Circular Arc Curve Chamber Self-Excited Oscillation Nozzle

In order to improve the cavitation performance of the self-excited oscillation nozzle (SEON), a novel SEON with a circular arc curve chamber was designed by changing the chamber wall profile of the SEON. The performance of the circular arc curve chamber SEON was studied numerically. Taking the vapor volume distribution and the vapor volume fraction as the evaluation indexes, the influences of the chamber wall profile on the cavitation performance of the circular arc curve chamber SEON were analyzed. In addition, it was compared with the broken-line chamber SEON. The numerical results show that the cavitation performance of the circular arc curve chamber SEON is first enhanced and then weakened by increasing the circular arc radius. The circular arc curve chamber structure can form a larger central cavitation volume in the nozzle, which improves the cavitation performance of the SEON. When the circular arc radius is 2 mm, the cavitation area and the turbulent kinetic energy of the circular arc curve chamber SEON increase by 122.5% and 16.9%.

Statistical proposals for a formal classification of Chalcolithic stone masonry passage graves with circular chamber in the Southeast of the Iberian Peninsula

This study offers a classification of 106 megalithic stone masonry passage graves forming part of the Los Millares archaeological complex characterised by circular chambers. The study has employed a statistical method implementing the OneR, JRip and Part classification algorithms as well as multivariate analyses. The research yielded four groups: large tombs capped with flat roofs, small tombs covered by false domes, and two types of medium-large tombs capped either by flat or false-domes that can be distinguished according to the angles of their chambers walls and the presence of construction reinforcements, including the number of stone retainer rings walls serving to brace the thrust.

Modified stochastic medium prediction model for the deformation response of concealed underground stations under existing pipelines

The underground pipeline network in the city is so intertwined that the concealed excavation of a metro station inevitably leads to a series of underground pipelines, causing settlement deformation and further risk of leakage. The existing theoretical methods for analysing settlement deformation are mostly for circular chambers, whereas metro stations have a nearly square cross-sectional form and different construction methods are very different, which have a greater impact on the deformation of the overlying pipelines. In this paper, based on the random medium theory and Peck's formula, the improved random medium model for predicting ground deformation is modified, the correction coefficients λ and η for the influence of different construction methods are proposed, the prediction model of underground pipeline deformation under different construction methods is obtained, and the numerical models of four work methods commonly used in urban tunnel construction: pillar hole method, side hole method, middle hole method and Pile-Beam-Arch (PBA) method are constructed through simulation, and the mathematical analysis software was used to fit the results to the model and obtain the range of correction coefficients λ and η for each of the four methods, and the accuracy and applicability of the theoretical model was verified by combining with actual engineering cases. The influence on the overlying pipes is in descending order: side hole method, pillar hole method, middle hole method and PBA method. The theoretical model provided in this paper for predicting the deformation of pipes in any overlying strata of the tunnel is well suited to the actual project and has a high degree of correlation with the measured results.

Steady rotation of a Mach shock: experimental and numerical evidences

This experimental and numerical work reports on the dynamical behaviour of a shock in an inert gas at the concave wall of a hollow circular chamber. The gas in the chamber was air or He + $${\rm O}_{2}$$ + 2 Ar at initial pressures $$p_{{\rm c0}}$$ ranging from 2 to 12 kPa and initial temperature T0 =288 K. The shock was generated using a detonation driven shock tube. The shock dynamics were characterized through high-speed shadowgraph recordings and high-resolution numerical simulations. For each gas and $$p_\text {c0}$$ , the experiments evidenced the formation of a Mach reflection along the wall and identified a range of initial pressures for which this configuration rotates with constant stem heights and constant velocities larger than those at the chamber entry. The numerical simulations were capable of capturing the dynamics quantitatively. These results extend to inert gases our previous work with a reactive gas for which we reported on the possibility of a steadily rotating overdriven Mach detonation. The steadiness range is narrower with the inert gases, likely because of the smaller initial pressure ratios at the chamber entry and lower support from the subsonic flow behind the shock. The initial support in the reactive case was more efficient because the discontinuities at the chamber entry were self-sustained Chapman–Jouguet detonations. Further investigations of these Mach rotating regimes should rely only on specific experiments and numerical simulations, for example, on the effect of the chamber dimensions, because of the complex non-dimensional formulation of the problem.

Escape dynamics of confined undulating worms.

We investigate the escape dynamics of oligochaeta Lumbriculus variegatus by confining them to a quasi-2D circular chamber with a narrow exit passage. The worms move by performing undulatory and peristaltic strokes and use their head to actively probe their surroundings. We show that the worms follow the chamber boundary with occasional reversals in direction and with velocities determined by the orientation angle of the body with respect to the boundary. The average time needed to reach the passage decreases with its width before approaching a constant, consistent with a boundary-following search strategy. We model the search dynamics as a persistent random walk along the boundary and demonstrate that the head increasingly skips over the passage entrance for smaller passage widths due to body undulations. The simulations capture the observed exponential time-distributions taken to reach the exit and their mean as a function of width when starting from random locations. Even after the head penetrates the passage entrance, we find that the worm does not always escape because the head withdraws rhythmically back into the chamber over distances set by the dual stroke amplitudes. Our study highlights the importance of boundary following and body strokes in determining how active matter escapes from enclosed spaces.

Experimental and Semitheoretical Analyses of Uplift Capacity of Belled Pile in Sand

Although belled piles have been widely applied to structures subjected to large horizontal loads, such as coastal structures, high chimneys, and transmission towers, their uplift capacity characteristics under various conditions have not been investigated in detail. In this study, model tests were performed in circular and half-circular chambers to determine the uplift capacity of belled piles in sandy ground under conditions such as relative density, penetration depth, and pile-tip inclination angle. Furthermore, image analysis was conducted by monitoring the model tests in a half-circular chamber to verify the shape of the failure surface. A semitheoretical model to predict the uplift capacity of belled piles in sandy ground was developed using the pile-tip failure angle and failure surface curve in accordance with the relative density, penetration depth, and pile-tip inclination angle based on the limit-equilibrium equation of a previous conventional pile. The values calculated using the proposed model were in good agreement with those obtained from experimental model tests.