Wall Function Research Articles

Numerical simulation on JAG-type corrugated plate flow heat transfer characteristics considering physical property changes and shell heat transfer

This research considers the combined effects of changes in fluid properties and shell heat transfer. The realizable k-epsilon turbulence model combined with the enhanced wall function is used to numerically simulate the flow and heat transfer characteristics of a new plate-shell heat exchanger plate side, which was verified to be accurate in combination with previous research results. Focus was placed on the analysis concerning the flow heat transfer characteristics for different corrugation depths at different inlet velocities. It was found that increasing the corrugation depth can make the fluid distribution tends to be uniform heat transfer performance increases, but the increase in velocity will have the opposite effect on the heat transfer performance. Furthermore, field synergy theory reveals the synergistic distribution regularities of the velocity field with the temperature field and pressure field. Consecutive vortex structures are formed along the grooves, and the flow in the core region of the corrugated channels is similar to the heat flow, reducing the synergistic ability among the three fields makes the heat transfer less effective. These findings contribute to understanding heat transfer in similar scenarios, especially in energy engineering and thermal management.

Patient-Reported Abdominal Morbidity Following Abdomen-Based Breast Reconstruction.

Abdominal wall morbidity occurs with increased frequency following flap harvest in the obese abdomen. Its impact on patient-reported outcomes (PROs) in breast reconstruction has been poorly characterized. A retrospective review of obese patients undergoing abdominal-based free autologous breast reconstruction was conducted over 15 years. Patient operative characteristics were recorded and outcomes were analyzed. PROs were assessed using the BREAST-Q abdominal survey. In total, 75 women (108 flaps) with the mean body mass index (BMI) of 33.2 were included. Flaps included deep inferior epigastric artery perforator (24%), muscle-sparing (43%), and free transverse rectus abdominis myocutaneous flaps (f-TRAM; 33%). World Health Organization (WHO) obesity class, BMI, and flap type did not affect flap failure (1%) or complication rates. Hernia developed in 7%; all necessitated repair. Eight percent developed abdominal bulge; one was repaired. Hernia formation was associated with increased patient age (p < 0.05). Bulge formation occurred more often in f-TRAM donor sites (p = 0.005). BMI, WHO class, flap type, and mesh use were not related to hernia or bulge occurrence in either univariate or multivariate analysis. The survey response rate was 63%. Abdominal Physical Well-Being (proxy for abdominal wall function) and Satisfaction with Abdomen (patient-perceived cosmesis) were similar across flap types, age, and WHO classification groups. Patients with postoperative bulge reported higher abdominal physical well-being scores, regardless of flap type (p < 0.01). Bulge was correlated with lower satisfaction (p < 0.05). The incidence of abdominal wall morbidity following abdominal free-tissue transfer for breast reconstruction was acceptably low in our population of obese patients. Hernia was a clinically significant complication, warranting surgical repair. Bulge was primarily a cosmetic concern and did not detract from patient-reported abdominal wall function. Age may represent an independent risk factor for hernia formation in this population.

Experiment and Numerical Studies of Convection Heat Transfer around a Rotating Hand-Shaped Former

Forced convective heat transfer around a rotating hand-shaped former was numerically studied to improve the rubber-glove-curing process. The former surface was separated into eight segments for simulation. The shear stress transport turbulence model and its wall functions were employed to model the rotating hand-shaped former in the heated airflow field. The rotation rate of the former varied from 0 to 5 in the freestream. The Reynolds number ranged from 1,583 to 15,837. The simulation results were compared and well agreed with the experimental data. These results indicated that the convective heat transfer of individual sections and the entire body varied according to the aforementioned variables. The most effective rotation rate was observed for the former segments that were far from the rotation axis. The lowest convective heat transfer occurred in the middle finger, which was located on the rotation axis and was shielded by other segments. Therefore, the average Nusselt number on the middle finger was significant and derived using a novel equation. This equation was compared with the computational fluid dynamics results and exhibited an average error and correlation coefficient of 7.32% and 0.9, respectively. It can help reduce the trial-and-error method to obtain curing conditions for rubber glove manufacturing.

Generalisation of the Penalised Wall Function Method for the Simulation of Turbulent flows With Unfavourable Pressure Gradients

The penalized wall function method for simulation of compressible near-wall turbulent flow regions in the numerical modeling of viscous compressible flows is developed. The method is formulated as a differential condition to match the outer and the wall function solutions and is based on a generalized characteristic-based volume penalization method to transfer shear stress from the outer region of the boundary layer to the wall. The method is modified to extend its applicability to turbulent flows with adverse pressure gradient, when separation and reattachment zones are formed, as well as to use computational meshes with coarser near-wall resolution. These advantages are demonstrated for two test problems, namely, the flow over a flat plate with zero and adverse pressure gradients.

Seismic performance of RC frame-shear wall dual structural systems

The two structural systems named “functional integration structural systems” and “functional separation structural systems” were proposed based on the design concept of energy dissipation. To study the seismic performance of reinforced concrete (RC) frame-shear wall dual structural systems in which shear walls are used for “functional integration” and “functional separation”, quasi-static tests of two single-story and two-span RC frame-shear wall specimens with a scale of 1:3 were carried out, and numerical simulation analysis of two five-story frame-shear wall dual structures based on the conditional mean spectrum-incremental dynamic analysis (CMS-IDA) method was carried out. The shear walls bearing lateral load and a small part of the vertical load are named functional separation structure. When the shear walls bearing both lateral load and vertical load are named as functional integration structure, the seismic performance was investigated in terms of crack initiation and damage, hysteresis performance, stiffness degradation, energy dissipation capacity, ductility of the specimens, and seismic collapse resistance of the whole structure. The studies showed that when the load-bearing function and lateral resistance function of the shear walls were separated, the structure had better ductility, energy dissipation capacity, damage development process, and seismic collapse resistance.

8-[(4-benzylpiperazin-1-yl)methyl]-3-(2-chlorophenyl)-7-hydroxy-chromen-4-one is an activator of contractile activity of intestinal smooth muscles with reversible M2 cholinomimetic properties

Background. Several pathologies (such as diabetes mellitus, Parkinson’s and Alzheimer’s diseases, multiple sclerosis, etc.) are accompanied by degeneration of cholinergic neurons, which are key regulators of the contractile function of the gastrointestinal tract walls, leading to atony and paresis. An effective strategy for normalizing the lack of contractile function of visceral SM is the use of drugs - selective agonists of muscarinic acetylcholine receptors (mAChRs) of the M2 subtype. The high similarity of the structure of the agonist-binding sites of different subtypes of mAChRs causes problems to develop selective ligands for these receptors. Nowadays, there is an urgent necessity to develop selective agonists of M2 subtype receptors as pharmacological tools for laboratory research and promising drugs. The aim of the present research was to investigate the effect of the 8-[(4-benzylpipe­razin-1-yl)methyl]-3-(2-chlorophenyl)-7-hydroxy-chromen-4-one (compound 1), which was in silico predicted to bind mAChRs, on the contractile activity of rat caecum circular smooth muscle. Materials and Methods. The research was carried out on rats. The contractile activity was studied tensometrically in the isometric mode on preparations of the circular smooth muscles of the caecum of Wistar rats. The kinetic properties of individual spontaneous contractions of SM preparations were determined in accordance with the method of multivariate mechanokinetic analysis with the calculation of mechanokinetic parameters for the phases of contraction and relaxation: time (τ0, τC and τR), force (Fmax, FC and FR), velocity (VC and VR) and impulse (Imax, IC and IR). The kinetic properties of acetylcholine-induced contractions were analyzed by calculating the normalized maximum velocities of the contraction (Vnc) and relaxation (Vnr) phases. Results. It was found that compound 1 caused an increase in the amplitude of acetylcholine-induced contractions; this effect was eliminated by preincubation of SM with the mAChRs M2 subtype inhibitor AF-DX 116. It was revealed that compound 1 (0.1–50 μM) also has the ability to significantly activate the functional activity of colonic SM in a dose-dependent manner, increasing the force and frequency of spontaneous contractions, as well as their mechanokinetic parameters. It was found that the presence of compound 1 (0.1 μM) in the solution washing the smooth muscle for a long time leads to a significant increase in the amplitude and frequency of spontaneous contractions, which tends to reach a stationary mode after 40 minutes of its action. The effect of compound 1 was stable for at least an hour of application to the caecum, and was reversible and significantly eliminated by washing the SM. Conclusions. Compound 1 stimulates the contractile activity of the cecal smooth muscle and exhibits M2 cholinergic properties.

Generalization of the Penalized Wall Function Method for Modeling of Turbulent Flows with Adverse Pressure Gradient

Generalization of the Penalized Wall Function Method for Modeling of Turbulent Flows with Adverse Pressure Gradient

Multi-omics analysis reveals activation of jasmonate synthesis and modulation of oxidative stress responses in boron deficient pea shoots

Boron (B) is vital for plant growth and development. Understanding aboveground tissue responses to B deficiency can offer insights into enhancing plant productivity under B-limited conditions. Here we show from comprehensive metabolomics analysis that during B deficiency treatment the number of differentially expressed metabolites (DEMs) increases from 64 to 193 in pea shoots. Boron deficiency intensified oxidative stress and led to decreased ascorbate and glutathione levels. Integrative metabolomic and transcriptomic analyses revealed activation of the phenylpropanoid biosynthesis and α-linolenic acid metabolic pathways under B deficiency. Metabolites of the phenylpropanoid pathway, including p-coumaryl alcohol and sinapic acid, increased, accompanied by upregulation of related biosynthetic genes. A decline in total flavonoid content suggested that the activation of phenylpropanoid synthesis might indicate increased lignin accumulation, thus affecting cell wall metabolism. The alterations in these pathways at specific time point highlighted the dynamic resource allocation caused by B deficiency, providing insights into metabolic reprogramming in pea shoot apices. In the α-linolenic acid pathway, B deficiency led to accumulation of 17-hydroxylinolenic acid, jasmonic acid (JA), and jasmonoyl-L-isoleucine, with upregulated JA biosynthesis genes. Jasmonates are proposed to play a key role in reprogramming shoot development particularly modulating membrane and cell wall structure and function under B deficiency. Increased levels of oxidation products of linoleic acid suggest changes to membrane structure and are also consistent with changes to the redox status of cells under B deficiency. Collectively, our findings elucidated intricate B deficiency responses at both the metabolome and transcriptome levels and identified potential targets for breeding crops tolerant to B deficiency, including jasmonate signalling, phenylpropanoid biosynthesis, and antioxidant capacity.

Application of analytical wall functions to CFD analysis of condensation flow

The wall function (WF) enables analyzing condensation flow in a nuclear reactor containment vessel with reasonable computational costs. However, conventional wall treatments rely on the logarithmic laws for velocity, temperature, and concentration, limiting applicability. In this paper, we applied the analytical wall function approach to the condensation flow analysis of steam/air mixtures. This approach features the analytical integration of transport equations considering the buoyancy, the material property change, and the convective terms. We conducted CFD analysis with the analytical wall function models for the forced, mixed, and natural convection and confirmed good prediction, especially when the log law does not hold.

Functional Diversification and the Plant Secondary Cell Wall.

Much evidence exists suggesting the presence of genetic functional diversification in plants, though literature associated with the role of functional diversification in the evolution of the plant secondary cell wall (SCW) has sparsely been compiled and reviewed in a recent context. This review aims to elucidate, through the examination of gene phylogenies associated with its biosynthesis and maintenance, the role of functional diversification in shaping the critical, dynamic, and characteristic organelle, the secondary cell wall. It will be asserted that gene families resulting from gene duplication and subsequent functional divergence are present and are heavily involved in SCW biosynthesis and maintenance. Furthermore, diversification will be presented as a significant driver behind the evolution of the many functional characteristics of the SCW. The structure and function of the plant cell wall and its constituents will first be explored, followed by a discussion on the phenomenon of gene duplication and the resulting genetic functional divergence that can emerge. Finally, the major constituents of the SCW and their individual relationships with duplication and divergence will be reviewed to the extent of current knowledge on the subject.

Clinical and Radiological Evaluation of Onlay Mesh Abdominoplasty in Obese Multiparous Patients with Moderate-to-Severe Rectus Diastasis.

Women with multiple pregnancies often experience abdominal protrusion and/or a lax abdominal wall. Various open surgical techniques have been developed to address rectus diastasis in abdominoplasty, ranging from suture plication to mesh reinforcement. This study aims to compare the clinical and radiological changes between traditional abdominal plication and the addition of non-absorbable mesh for rectus muscle (RM) diastasis repair in terms of function, postoperative outcome, and recurrence. This prospective retrospective study involved 63 women who underwent cosmetic tummy tuck surgery and met certain eligibility criteria. Patients with only mild diastasis recti, midline hernia, contraindications for major surgery, recent smoking history, or refusal of mesh augmentation were excluded. Clinical examination for abdominal protrusion or bulging and CT imaging was performed to check for recurrence of diastasis recti. The study included 33 patients who underwent mesh repair and 30 who underwent traditional abdominal plication. Follow-up was conducted after 1year using CT and a questionnaire to assess various factors compared to preoperative measurements, with overall satisfaction rated on a 10-point Likert scale. There was no significant difference in demographic data between the two groups. Patients who underwent mesh repair had a slightly longer hospital stay and drain duration. The average waist circumference decreased in both groups without any statistically significant difference. Objective CT showed significant reductions in both groups in inter-rectus distance, RM width and circumference, and intra-abdominal circumference compared to preoperative values. All patients expressed satisfaction with scar quality and umbilicus aesthetics, and no recurrence was detected either clinically or radiologically during the follow-up period. Comprehensive preoperative assessment and imaging techniques like ultrasound and CT scans allow surgeons to detect postpartum changes in the abdominal wall. Mesh reinforcement may be indicated for diastasis above 4 cm in obese multiparous females. Thorough preoperative evaluation permits customized surgical plans to optimally restore abdominal wall anatomy and function. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors at www.springer.com/00266 .

Experimental Study on Flow Structure Characteristics of Gap Flow Boundary Layer Based on PIV

The boundary layer is the main source of frictional resistance in gap flow, and the study of the flow structure characteristics of the gap flow boundary layer is of great significance for the study of gap flow theory. In this study, the PIV technique was utilized to experimentally investigate the gap flow boundary layers with Reynolds numbers of 16,587–56,870 and gap ratios of 0.6–0.8. The characteristics of the wall friction velocity, the boundary layer thickness, and the wall function of the gap flow boundary layer were analyzed, and the influences of the mean velocity of the gap flow and the gap ratio on the flow structure characteristics of the boundary layer were explored. The results show that using PIV to measure the velocity profile in the viscous sub-layer to solve for the wall friction velocity had good precision. The boundary layer thickness was inversely proportional to the mean velocity of the gap flow and the gap ratio. The wall functions of the boundary layer were as follows: in the viscous sub-layer (y+&lt; 5.5), u+=y+; in the transition layer (5.5 &lt;y+&lt; 26), u+=10.071tanh0.071y+; and in the logarithmic layer (y+&gt; 26), u+=2.78lny++3.8. The thickness of the logarithmic layer was proportional to the mean velocity of the gap flow and inversely proportional to the gap ratio. The inner region of the boundary layer extended to y&lt; 0.18δ or y&lt; 0.13(h/2).

Modified correlations for the Nusselt numbers at the boundaries of a bottom-heated molten metal layer in a stratified corium melt pool and an assessment of heat transfer conditions during a severe accident

The paper discusses new correlations for the Nusselt numbers at the side and bottom surfaces of a bottom-heated molten steel layer under the conditions of mixed natural convection of the melt at Rayleigh (Ra) numbers from ∼ 106 to 1012. The melt layer under consideration is characterized by radial non-uniformity of the temperature distribution, when the averaged temperatures of the top and side surfaces of the layer show a difference in value. This thermal pattern of the molten metal layer is typical when a stratified corium molten pool forms during a severe accident (SA). Upper metallic melt layer goes above the oxide phase of corium pool, and it is heated along its bottom surface. For an adequate prediction of heat transfer at the side and bottom surfaces of a layer in a SA, we developed special correlations for the Nu numbers. They take into account Rayleigh number and additional factors that determine geometric parameters of the layer and the temperature conditions at the bottom, side and top surfaces of the layer. Parameters in the developed correlations for the Nu numbers were determined via CFD simulation and mathematical processing of the simulation results. CFD simulations by means of the ANES code were completed in accordance with a specially developed experiments matrix. Two-parameter k-ω turbulence model by Wilcox, which includes Menter’s improved near wall functions, has been implemented in the CFD code and applied accordingly. To evaluate the accuracy and predictability of the developed correlations we ran a comparative analysis of the Nu numbers at the sidewall and bottom surfaces of the melt layer, as defined on the basis of the developed correlations for the Nu numbers and as defined in CFD simulation. The comparison showed a strong correspondence of the results within a wide range of Rayleigh number values of ∼ 106 < Ra < 1012. The analysis of the developed correlations allowed shaping a number of critical arguments that define heat transfer conditions at the melt layer boundaries. It was found that the Nu numbers at the side and bottom surfaces are largely dependent on the difference in the temperatures of the top and side surfaces of the layer. As the difference between the these temperatures widens, the Nu numbers increase drastically (by tens of percent or more) in comparison to similar Nu numbers defined on the basis of the well-known correlations. It is specified that when the temperatures at the top and side surfaces of the layer are equal, the heat transfer conditions at the side surface are defined by “Globe and Dropkin” correlation used for the horizontal surfaces of the layer. We also evaluated the significance of the geometric parameters on the Nu values for the sidewall and bottom surfaces of the melt layer. Multiplicative effect of this parameter and of the parameter for temperature conditions at the boundaries of the layer mentioned above may lead to a significant (by times) increase of the Nu values. That must be considered in the thermal analysis of the corium pool and the processes of the SA.

Intracranial Aneurysms and Lipid Metabolism Disorders: From Molecular Mechanisms to Clinical Implications.

Many vascular diseases are linked to lipid metabolism disorders, which cause lipid accumulation and peroxidation in the vascular wall. These processes lead to degenerative changes in the vessel, such as phenotypic transformation of smooth muscle cells and dysfunction and apoptosis of endothelial cells. In intracranial aneurysms, the coexistence of lipid plaques is often observed, indicating localized lipid metabolism disorders. These disorders may impair the function of the vascular wall or result from it. We summarize the literature on the relationship between lipid metabolism disorders and intracranial aneurysms below.

Towards the integration of distributed renewables: Operation analysis of pumped storage system under off-design condition based on CFD

Pumped storage plants are increasingly developing to cope with the rapid growth of renewable energy production. Micro-pumped storage (MPS) system is a new storage strategy for distributed energy integration. Centrifugal pump or axial pump replaces conventional pump turbines in this pumped storage system to ensure economic convenience and system flexibility. However, when MPS works in the generating operation mode, the limited high-efficiency range will result in complex hydrodynamic behavior and stability issues under off-design conditions due to renewable integration. At present, the instability mechanism of MPS under off-design conditions is not clear enough, and there is a lack of excellent research methods to analyze this problem. Therefore, this paper firstly introduces the entropy production theory considering the wall effect for visualizing the energy loss. Then the relationship between hydraulic performance and unsteady flow characteristics is established based on the loss characteristics. The results show that the entropy production theory with customized wall functions has higher accuracy and advantages in energy loss analysis compared to the default wall functions. Under partial loading conditions, the spatial-temporal instability of the flow separation point causes a rotating stall within the impeller, which in turn leads to destabilization and a significant reduction in hydraulic performance. Under overload conditions, despite slight changes in hydraulic performance, the most significant pressure fluctuation is six times stronger than the best efficiency point.

Pesticide exposure an unforseen trigger for atrial fibrillation

Abstract Background/Introduction Over the last few decades, the use of pesticides for improving crop yield has continued to soar. Recent evidence shows the residuals of pesticides in many fruits and vegetables in the local supermarket. Although acute exposure to pesticides has been related to various severe illness, including cardiovascular dysfunction, chronic pesticide exposure has been poorly studied. Herein we study the cardiotoxic effect of commonly used pesticides to the most common cardiac arrhythmia, atrial fibrillation (AF). Purpose Whether exposure to commonly-used pesticides triggers AF if so, explore the underlying molecular mechanism. Methods Ten commonly used pesticides in the Netherlands, including glyphosate, MCPA and boscalid, were used to study cardiotoxicity using experimental Drosophila and rat model systems for AF. Drosophila were exposed to three varying pesticide concentrations, ranging from reported environment concentrations, LD50 and high dose, followed by survival and heart wall measurements (heart rate (HR) and arrhythmicity index). In addition, rats were exposed to four pesticides, paraquat, glyphosate, round-up and MCPA for 16 months followed by AF detection (ECG) and Westernblot and metabolomic analyses of the atrial tissue samples. Results A dose dependant survival curve was observed of Drosophila fed with pesticides compared to controls. In prepupae a significant reduction in HR and increase in arrhythmicity index was found for all? utilized pesticides. Furthermore, a significant increase in AF and atrial arrhythmic episodes was observed in rats treated with pesticides (15-70%) compared to non-treated control rats (0%). Metabolomic analyses in rats revealed a significant increase in mitochondrial supercomplexes and 6-phosphoglyconlactate levels in pesticide treated rats compared to controls, suggesting a role for mitochondrial and energy dysfunction to underlie pesticide-induced AF. Conclusion(s) This study provides evidence that chronic exposure to commonly-used pesticides in the Netherlands affects longevity, heart wall function in Drosophila and triggers atrial arrhythmia and AF in rats. Likely, the pesticides impair mitochondrial function and energy metabolism.

Flow rectification in a micro-nanochannel junction: Interplay of channel geometry and interfacial properties for directional transport

The linear correspondence between flow rate and pressure drop for low Reynolds number hydrodynamics is often a constraint for the realization of miniaturized fluid circuits with selective junctions. Here we devise a micro-nanochannel junction with the directional flow in the nanochannel achieved by a combination of junction geometry and wall functionalization. The system can be compared to a fluid diode with parity-breaking between pressure drop and flow rate in the nanochannel junction with increasing flow rates in a particular configuration and negligible throughput in the reverse direction. This directional junction transport is tuned with slip length, characterizing channel wall functionalization as the bias parameter. Tuning the transport or leakage at a junction is key to engineering various applications. Such junctions are ubiquitous in systems like capillary blood flow, desalination systems, energy storage devices, etc. The resulting flow physics, thus unraveled, is an amalgamation of various factors which leads to a flow rectification system. We have delineated the effect of the confinement of the channel, the slip, and the geometry of the nanochannel towards the selective nature of the resulting configuration. We have successfully characterized a system to generate flow anisotropy while transporting fluid in different directions using numerical techniques. Additionally, our work demonstrates, for the first time, that a common definition of slip coefficient may be associated with three different flow regimes, which correspond to the order of magnitude of slip length relative to the channel dimensions thus providing a unifying key to engineer substrates and geometries towards designing fluid circuits.

Scaling high Rayleigh number natural convection boundary layer statistics: A vertical water tunnel experiment

A high Rayleigh number natural convection boundary layer adjacent to the vertical heated wall was investigated at a large-scale facility. The global Rayleigh number (Rax) measured by the temperature difference between the wall and ambient water and the distance from the bottom of the heated wall reached 1013. Experimental results confirm that the global Nusselt number Nux is scaled by power 1/3 of Rax, which is similar to the well-known asymptote of the previously achieved Rax. The velocity field obtained using particle image velocimetry (PIV) indicated that the buoyancy-dominant outer-layer scaling suggested by Wells and Worster [A geophysical-scale model of vertical natural convection boundary layers, J. Fluid Mech. 609, 111–137 (2008)] was not only applicable to scale the lower-order velocity statistics but was also valid as a reasonable measure of the spatial correlation, probability distribution, and quadrant contribution features in the outer layer. The dynamical behavior of fluid motion captured by PIV supported a robust momentum transfer to positive wall-normal direction, which was sustained by the Q1 and Q3 quadrants. In addition, merging the existing literature and current data suggested that near-wall function can be applied at a moderate Rax; the universality of this wall-function model was confirmed around z×∼0.7 (where z× represents the near-wall scaled wall-normal distance, Kiš and Herwig [The near wall physics and wall functions for turbulent natural convection, Int. J. Heat Mass Transfer 55, 2625–2635 (2012)]). At a larger buoyancy regime, it was expected to follow a canonical boundary layer flow.

Association between Smartphone Addiction and Breathing Pattern in Sedentary Young College-Going Students - A Cross-Sectional Study.

The number of smartphone users has progressively increased worldwide. Altered biomechanics of the cervicothoracic spine and ribcage could limit the chest wall function that affects the respiratory muscles strength, reducing diaphragm function in smartphone users. This study aimed to compare breathing patterns between smartphone-addicted and -nonaddicted user groups. To find the association between excessive smartphone use and breathing pattern in sedentary young college-going students. This cross-sectional study includes 230 participants. The participants were screened for the inclusion and exclusion criteria and were asked to fill out a Smartphone Addiction Scale questionnaire. These breathing patterns were then assessed by self-evaluation of breathing questionnaire (SEBQ), manual assessment of respiratory motion (MARM), breath-holding test, and capnography. The correlation of smartphone-addicted and -nonaddicted groups with breathing patterns was performed by Spearman rank correlation. Results show no significant association between the smartphone-nonaddicted and -addicted users. This study concluded that excessive smartphone use and breathing patterns are not associated.

Investigating Reynolds number effects in turbulent concentric coaxial pipe flow using stochastic one‐dimensional turbulence modeling

AbstractThe present study numerically investigates turbulent momentum transfer in concentric coaxial (annular) pipe flow with small radius ratios . To model the flow, a stochastic one‐dimensional turbulence (ODT) model formulated for cylindrical geometry is used that provides full‐scale resolution along a representative radial coordinate. The present investigation extends the model validation by Tsai et al. (PAMM, 22:e202200272, 2023), to radius ratios smaller than 0.1 and addresses boundary layers with strong spanwise curvature effects. The focus is on the assessment and analysis of statistical flow features in the vicinity of the inner cylinder wall, particularly in cases with small radius ratios. Following Boersma &amp; Breugem (Flow Turbul. Combust., 86:113–127, 2011), classical boundary‐layer and mixing‐length theory is utilized to analyze the model predictions. The results demonstrate that the ODT model captures leading‐order curvature and mixing‐length effects by its physics‐compatible construction. Utilizing the model for extrapolation to high Reynolds numbers inaccessible to conventional high‐fidelity numerical approaches shows that curvature effects persist and nonlocally affect the entire boundary layer. The model results provide support for a spanwise‐curvature‐modified wall function.