Present Numerical Data Research Articles

Most Hampering Factors in the Implementation of Total Quality Management at Public Secondary Schools in South Africa

The study aims to investigate the most inhibiting factors to the implementation of Total Quality Management (TQM) at public secondary schools in the King Cetshwayo district of KwaZulu-Natal province in South Africa. The study adopted a posistivist paradigm and employed aa quantitative research approach in order to attend to the nature of the research problem and present numerical data. Three hundred (300) teachers and departmental heads were conveniently, but randomly sampled, and served with questionnaires to participate in the study. Empirical findings of this study revealed that the most factors hampering implementation of TQM at public secondary schools were the lack of resources/financial resources, failure by top management to create a suitable environment for quality improvement, lack of management skills, and poor commitment and philosophy to devise quality management strategies by top management. This paper indicates the suggested changes which the Department Basic Education needs to implement to improve the quality of education in public schools. The proposed changes are: to train and capacitate school principals regarding the best TQM to be implemented. There is a need to resource and fund schools to ensure all TQM-related infrastructure and human resources are available for effective or successful implementation. Received: 23 March 2024 / Accepted: 30 October 2024 / Published: 05 November 2024

The Effect of Glucagon-Like Peptide-1 (GLP-1) Receptor Agonists on the Lipid Profile of Diabetic Patients Using Statins: A Retrospective Cohort Study in the Diabetic Center of King Salman Bin Abdulaziz Hospital, Saudi Arabia.

Background Dyslipidemia is a common complication of type 2 diabetes mellitus (T2DM), which is the leading cause of morbidity and mortality in developed countries, including Saudi Arabia. Injectable glucagon-like peptide-1 receptor agonists (GLP-1RA) are recent therapies found to be effective in treating dyslipidemia in diabetic patients by acting similarly to the body's internal glucagon peptide hormone, regulating blood sugar levels and reducing triglycerides and low-density lipoprotein (LDL) levels. Aim of the study This retrospective cohort study aimed to investigate the effect of GLP-1RA on the lipid profile of dyslipidemia diabetic patients who were not controlled using statins. Methods Data were collected from the medical records of male and female diabetic patients with dyslipidemia (uncontrolled by statins) who were administered to the diabetic center of King Salman Bin Abdulaziz Hospital in Riyadh, Saudi Arabia, and received GLP-1RA (dulaglutide) from June 2023 to August 2023. The primary endpoint was the change in triglycerides and LDL-C levels after three months of using dulaglutide, and the secondary endpoints included the change in body weight, BMI, and HbA1c%. Descriptive analysis was conducted to present numerical and categorical data. The Wilcoxon signed-ranktest was used to compare numerical data before and after using dulaglutide. Ethical considerations were taken into account by ensuring anonymous data collection and obtaining IRB approval before data collection. Results The study included 102 patients with a median (interquartile range (IQR)) age of 59 (14) years. Females constituted 55.2% of the population. Obesity (96.1%), hypertension (71.6%), and retinopathy (13.7%) were the most commonly reported comorbidities. The study showed a significant reduction in body weight, BMI, HbA1c, hemoglobin, mean corpuscular volume (MCV), serum LDL-C, and triglyceride concentrations after three months of using dulaglutide (p<0.001). Conclusion Our study results confirm the positive effect of the GLP-1RA (dulaglutide) on the lipid profile of diabetic patients with dyslipidemia uncontrolled by statins.

High-order discretization–based self-adaptive turbulence eddy simulation for supersonic base flow with PHengLEI software

PurposeThe purpose of the present study is to develop a new numerical framework that can predict the supersonic base flow more accurately, including the development of axisymmetrically separated shear layer and recompression shock. To this end, two aspects are improved and combined, i.e. a newly self-adaptive turbulence eddy simulation (SATES) turbulence modeling method and a high-order discretization numerical scheme. Furthermore, the performance of the new numerical framework within a general-purpose PHengLEI software is assessed in detail.Design/methodology/approachSatisfactory prediction of the supersonic separated shear layer with unsteady wake flow is quite challenging. By using a unified turbulence model called SATES combining high-order accurate discretization numerical schemes, the present study first assesses the performance of newly developed SATES for supersonic axisymmetric separation flows. A high-order finite differencing-based compressible computational fluid dynamics (CFD) code called PHengLEI is developed and several different numerical schemes are used to investigate the effects on shock-turbulence interactions, which include the monotonic upstream-centered scheme for conservation laws (MUSCL), weighted compact nonlinear scheme (WCNS) and hybrid cell-edge and cell-node dissipative compact scheme (HDCS).FindingsCompared with the available experimental data and the numerical predictions, the results of SATES by using high-order accurate WCNS or HDCS schemes agree better with the experiments than the results by using the MUSCL scheme. The WCNS and HDCS can also significantly improve the prediction of flow physics in terms of the instability of the annular shear layer and the evolution of the turbulent wake.Research limitations/implicationsThe small deviations in the recirculation region can be found between the present numerical results and experimental data, which could be caused by the inaccurate incoming boundary layer condition and compressible effects. Therefore, a proper incoming boundary layer condition with turbulent fluctuations and compressibility effects need to be considered to further improve the accuracy of simulations.Practical implicationsThe present study evaluates a high-order discretization-based SATES turbulence model for supersonic separation flows, which is quite valuable for improving the calculation accuracy of aeronautics applications, especially in supersonic conditions.Originality/valueFor the first time, the newly developed SATES turbulence modeling method combining the high-order accurate WCNS or HDCS numerical schemes is implemented on the PHengLEI software and successfully applied for the simulations of supersonic separation flows, and satisfactory results are obtained. The unsteady evolutions of the supersonic annular shear layer are analyzed, and the hairpin vortex structures are found in the simulation.

Unforeseen Effects of the Post-Provisioning Model in Principal’s Administrative Roles in South African Public Schools

This study aims to investigate the effects of the Post-Provisioning Model in the management of public secondary schools in the King Cetsh wayo district of Kwa Zulu-Natal province in South Africa. Apart from previous studies on PPM, this investigation was conducted quantitatively to present numerical data. Since the study presented numerical data, this study was found grounded in the positivist paradigm. The literature findings reveal that school principals experience poor strategic management, lack of capacity-building workshops, poor filling of vacant posts; failure to manage educator job satisfaction, late admission of learners, and poor redeployment processes of educators. Empirical findings of this study also confirm such effects of PPM which threatens school management roles. The paper concludes by the submissions that there is a need to revise PPM implementation to address challenges and support the management roles of school principals. Moreover, there is a need to incapacitate school managers regarding the management of PPM for its effective implementation.

Experimental and numerical investigation of thermo-hydrodynamic performance of twin tube counter flow heat exchanger using cerium oxide nanofluid

This study accomplished experimental and numerical investigations regarding cerium oxide (CeO2) nanofluid. The aim of this study is to estimate the thermo-hydrodynamic performance of twin tube counter flow heat exchangers (TTCFHEs) in the presence of CeO2 nanofluid. The CeO2 nanofluid concentrations varied from 0.1% to 0.3% by volume. In TTCFHEs, the mass flow rates of cold fluid flow varied from 3 LPM to 15 LPM (i.e. Reynolds number, Re varied from 2436 to 11,626). At the same time, hot fluid flows inside the shell at a constant mass flow rate of 6 LPM. For the numerical investigations, the standard k-ɛ model is adopted for the turbulent flow regimes, where the Reynolds number is varied from 2436 to 11,626. For validation purpose, the present numerical study and experimental data are matched with the correlations available in the literature. Further, numerical result of the Nusslet number is well agreed with the experimentally recorded data with a deviation less than 10%. From the study, it is witnessed that the outlet temperature of the cold fluid increases and decreases with increasing the concentrations of CeO2 nanofluids and with increasing the flow Reynolds number, respectively. On account of 0.3% and 0.2% CeO2 nanofluid, the average Nusselt number (Nu) showed almost 43.35% and 30.13% greater than that of base fluid with a moderate increase in the pressure drop in the range of mass flow rate is considered. However, from the numerical investigations, the performance evaluation criteria (PEC) increases with increasing nanofluid concentrations. At higher concentrations (i.e. 0.3%) of CeO2 nanofluid, the average PEC showed 16.65% higher than the 0.1% CeO2 nanofluid with a marginal increase in the pressure drop.

Aerothermodynamic Analysis of Space Recovery Experiment Capsule at Mach 6

The main focus of this paper is to compute the flowfield and assess the aerodynamic drag of Space Recovery Experiment (SRE) modules at freestream Mach 6 at zero angle of incidence. Time-dependent Compressible axisymmetric Navier-Stokes equations are numerically simulated using a finite volume discretization method with a three-stage Runge-Kutta time-stepping scheme. The computed shock stand-off distance, pressure ratio across normal shock and stagnation point heat flux are showing satisfactory results with the analytical solutions.Available wind tunnel data such as Schlieren images, oil flow pictures and fore-body aerodynamic drag are compared with numerical results.Influence of various ramp angles of the SRE modules on surface pressure, flow separation, skin friction coefficient, wall heat flux and fore and base aerodynamic drag coefficients are investigated using present numerical data.

Effectiveness of norepinephrine versus phenylephrine intravenous boluses for the treatment of hypotension in elective lower-segment cesarean section under spinal anesthesia: A randomized controlled, double-blind study

Abstract Background and Aim: Hypotension following spinal anesthesia is a common adverse effect during caesarean sections, with potentially harmful consequences for both the mother and the fetus. While phenylephrine is the current first-line treatment for maternal spinal hypotension during obstetric anesthesia, norepinephrine has been proposed as a possible alternative due to its weaker b-agonist-mediated positive chronotropic action. However, there is a lack of comparative data on the safety and efficacy of these two drugs in obstetric anesthesia. This study aimed to compare the number of bolus doses of phenylephrine and norepinephrine required to treat hypotension after spinal anesthesia in lower segment caesarean sections, as well as to evaluate maternal and fetal outcomes in both groups, including complications. Materials and Method: A prospective double-blinded randomized controlled trial was conducted, The study included 60 term parturients between the ages of 18 and 40, who had singleton pregnancy and were categorized as American Society of Anaesthesiologists (ASA) physical class II, and who were scheduled for elective caesarean section under spinal anesthesia. the parturients were randomized into two groups: Group N and Group P. Group P patients received an intravenous dose of phenylephrine 100 µg, while Group N patients received an intravenous dose of 8 µg whenever the systolic arterial pressure dropped below 20% of the baseline.primary objective was number of intravenous drugs required to treat spinal hypotension, secondary objective were incidence of maternal and foetal Complications. The data was collected on a form and entered into Excel. Statistical analysis was done using Epi Info 7.2.1.0 for Windows. The Kolmogorov-Smirnov test was used to check normality. Mean and standard deviation or median and range were used to present numerical data, while frequency and percentage were used for categorical data. T-tests compared quantitative variables, and Chi-square tests compared categorical data. Two-tailed tests were used, and a P-value of &lt;0.05 was considered significant. Result: The patient’s demographic profile was comparable in both groups.T he number of bolus doses of study drug required to treat spinal hypotension was significantly lower in Group N versus P (1.50 ± 0.57 vs. 2.13 ± 0.73, p =0.001)Incidence of bradycardia was more in group P, but not statistically significant. Other maternal complications like bradycardia, hypertension, nausea, vomiting, shivering were comparable in both groups. Conclusions: According to our study, Intermittent boluses of norepinephrine were effective in the management of spinal-induced hypotension during caesarean section. Norepinephrine boluses can thus be considered as an alternative to phenylephrine boluses.

Accessibility Towards West Sumatra Tourism Area

Accessibility was identified as the main factor driving tourist travel. The transportation sector is one of the strategic elements in tourism. Transportation in tourism is a means to achieve tourist destinations and also a means of movement in tourist destinations. Transportation is one of the important indicators in the development of tourist destinations and the selection of destinations by tourists. West Sumatra Province is one of the provinces in Indonesia which is rich in tourist attractions and is also one of the tourist destinations that is quite taken into account not only at the national level but also at the international level. West Sumatra has been designated as one of the main national tourist destinations. This research identifies accessibility to existing tourist areas in West Sumatra and analyzes areas that have the highest and lowest accessibility and explains the existing condition of the availability of public transportation to provide services in terms of providing good accessibility to the tourist zone. This research uses a quantitative approach method to present numerical data through the normal distribution method to make each accessibility parameter into three classifications namely low, medium, and high, and also uses a qualitative approach that aims to investigate, describe and explain the existing conditions of transportation facilities to tourist zone which is the object of research using primary data. Through a qualitative approach, a detailed description of the condition of the availability of routes and public transportation will be produced which will be analyzed based on the results of mapping in the study area.

Experimental and numerical comparison of currently available reaction mechanisms for laminar flame speed in 70/30 (%vol.) NH3/H2 flames

To achieve net zero carbon emissions, ammonia is gaining traction as a promising alternative fuel. However, the combustion characteristics of ammonia need further investigation. The current study aims to analyze the laminar flame speed, a fundamental physio-chemical property of any combustible mixture, through experimental measurements and kinetic reaction mechanism analysis. The laminar flame speed of 70/30 (%vol) NH3/H2 at atmospheric pressure and ambient temperature across a wide range of equivalence ratios (0.6–1.4) was studied experimentally and compared to the performance of 36 kinetic reaction mechanisms to appraise their performance concerning laminar flame speed prediction for the measured NH3/H2 mixture. The absolute percentage error (APE) formula has been adopted for preliminary estimation based on the experimental measurements of the present study and numerical data. The study found that Duynslaegher et al. 2012 model shows good performance speed across lean and stoichiometry conditions with an APE value between 0%-6%. The mechanism of Nakamura et al., 2017 and Gotama et al., 2022 demonstrates a good estimation of laminar flame speed under rich conditions. The sensitivity analysis revealed that the reactions H+O2=O+OH, NH2+NH2=N2H2+H2, and OH+H2=H+H2O are the most crucial reaction with considerable effect in promoting the laminar flame speed at all conditions, while the reactions of H+O2(+M)=HO2+M, NH2+H=NH+H2, and NH2+O=HNO+H play an essential role in the retardation of laminar flame speed at all conditions. The effect of the aforementioned reactions varies for the equivalence ratio, mainly due to changes in adiabatic flame temperature.

Numerical evaluation of air gap effect on double-glazed solar air heater performance

Double glazing is one of the effective ways to improve the thermal performance of flat-plate solar air heaters. In this regard, by considering this type of heat exchanger, the free convection flow between two glass covers and the forced convection flow inside the main air channel were analyzed in the present study. The exact implementation of this idea was numerically investigated using COMSOL Multiphysics commercial software. Due to the occurrence of Bénard convective flows in the space between two glasses, the air gap thickness must be optimized so that the positive effect of the presence of the air layer as a suitable thermal insulation is not affected by this phenomenon and does not lead to thermal dissipation. By choosing air gaps of 1 cm to 5 cm and sun radiative heat fluxes of 600, 800, and 1000 W/m2, it was found that the higher rate of heat transfer from the absorber plate into laminar forced convection airflow took place in the air heater with 3 cm air gap. Under the solar irradiation of 1000 W/m2, computations indicated the values of 11.2 K, 9.7 K, and 8.8 K for air temperature increase along the air heaters with the air gap thicknesses of 3 cm, 5 cm, and 1 cm, respectively. Comparisons between the present numerical findings and experimental data reported in the literature revealed an excellent consistency.

An analytical formulation of unidirectional composite curved beam with out-of-plane fiber waviness under bending

A closed-form analytical solution is developed for analyzing laminated composite curved beam with out-of-plane fiber waviness under bending. Timoshenko beam theory was adopted in derivation where the effects of shear deformation was considered for moderately thick beam. Explicit expressions for evaluating equivalent axial and bending stiffness are formulated based upon the modified lamination theory and taking the structural deformation characteristics of narrow section beam into consideration. Stress distribution at any given location calculated by the proposed method is investigated. Significant increase of radial normal stress and shear stresses are observed when out-of-plane fiber waviness is introduced. The comparisons between present analytical results and numerical data indicate that the present methodology have ability to capture radial normal, circumferential normal, and shear stress distributions of composite curved beam with out-of-plane fiber waviness and the level of stress predicted is satisfactory with numerical results.

SUICIDE AS A PHENOMENON IN THE MUNICIPALITY OF PRIZREN FROM CITIZENS’ PERSPECTIVE

Suicide as a phenomenon is present in almost all societies of the world, including the Kosovar society, through which the individual tries to take his own life. According to the law, this offense is not punished because the individual ceases to exist as a legal subject, but if we are dealing with pushing or assisting suicide, then investigations are initiated by the competent authorities. The main purpose of this paper is to provide an overview of the opinions of the citizens of the Municipality of Prizren on the cause, methods and treatments of suicide cases in this municipality. An online questionnaire was used to achieve the required results. The research method used is of quantitative type, through which it is attempted to present numerical data about the issue in question. The results of the research indicate that the main cause of suicides in the Municipality of Prizren are unstable economic conditions, narcotic substances use and psychological stress. The research determines that one of the main ways to commit suicide is hanging and jumping from high objects. According to the data provided, it is observed that the phenomenon of suicide is of medium frequency, and not all cases of suicide should be subject to autopsy examination.

Effects of non-Darcy mixed convection over a horizontal cone with different convective boundary conditions incorporating gyrotactic microorganisms on dispersion

This paper investigates the influence of dispersion impact on mixed convection flow over a horizontal cone within a non-Darcy porous medium. Multiple convective boundary conditions are applied to address the heat, mass and motile microorganism transfer phenomena. This paper incorporates the dispersion effect for gyrotactic microorganisms due to biological and environmental applications. By imposing appropriate similarity transformations, the nonlinear partial differential equations governing flow, temperature, concentration, and microbe fields are reduced to a system of ordinary differential equations & then solved using the MATLAB BVP4C function. The computation of grid independence test is analyzed for different flow profiles to show the precision of the points. In a few instances, our present numerical data is compared with previously published works, leading to excellent agreement. The non-Darcy effect, as well as mixed convection values from 0.1 to 0.9 and buoyancy parameters from 0.2 to 0.8, all significantly affects the velocity profile. The reduction in the microorganism profile is brought on by the increase in the bioconvection Lewis parameter and bio convection peclet number between 0.3 and 1. In the absence of dispersion, the variation of Biot numbers between 0.5 and 2, favor heat, mass, and motile microorganism transfer the most in the range of mixed convection parameter 0.5 to pure forced convection 1. Thermal, solutal and microorganism dispersion coefficients a, b, c that lie between frac{1}{7} and frac{1}{3} and higher values of modified peclet number ranges from 2 to 10 cause increased dispersion effects which lower flow transfer rates mostly in forced convection regime.

Unsteady MHD Tangent Hyperbolic Nanofluid Past a Wedge Filled with Gyrotactic Micro-Organism

In this numerical investigation, tangent hyperbolic nanofluid past a wedge-shaped surface filled with gyrotactic micro-organisms has been examined. The simulations have been performed in the presence of Ohmic heating and linear thermal radiation effect. After using similarity transformation to convert modeled PDEs into ODEs, the system of ODEs is tackled with the aid of shooting technique. For the authenticity of the code, the present numerical data have been compared with the already existing results in the literature. The impact of important governing parameters on velocity, concentration, temperature, and motile density distribution is examined graphically. Furthermore, the numerical values of the surface drag, heat transfer rate, mass transfer rate, and motile density number are computed and represented in the tabular form. Our simulations indicate that the Nusselt number is enhanced for the growing values of unsteadiness and the velocity ratio parameters. Moreover, a significant raise in nanofluid velocity is observed as magnetic number gets bigger whereas the temperature profile is depressed. For the above proposed model, it can be concluded that heat and mass can be enhanced by using gyrotactic micro-organism.

Data science and its application in anesthesiology

Electronic health records have brought about vast improvement in all aspects of healthcare. ‘Anesthesia Information Management System’ is a specialized form of electronic health record system that is used to record all of the events taking place during the perioperative period, such as clinical procedures performed, physiologic changes that may happen and the medications administered. Based on anesthetic data many databases have been developed internationally for quality improvement in anesthesiology and to know the research outcomes. At an individual clinical level, big anesthesia data is not yet present, unless waveforms and continuous numerical data of intraoperative physiologic variables is recorded. Though the initiative for big data has taken up by some healthcare institutions in the health data management but our country is still far behind in this field. This editorial is aimed to highlight the necessity of this system and to draw the attention of the concerned authorities to plan provision of electronic record keeping in operating rooms.&#x0D; Key words: Electronic Health Records; Data; Data Science; Anesthesiology&#x0D; Citation: Abbasi S, Ahmed U, Khan FA. Data science and its application in anesthesiology. Anaesth. pain intensive care 2021;26(1):1–3;&#x0D; DOI: 10.35975/apic.v26i1.1757&#x0D; Received: January 11, 2022, Accepted: January 14, 2022

Peripheral heat transfer prediction of the subcooled falling liquid film on a horizontal smooth tube

The peripheral heat transfer correlation of the subcooled falling liquid film outside the horizontal tube was established using the present numerical data under different liquid flow rates, heat fluxes, tube sizes, distributor heights, and liquid temperatures. The results indicated that the present correlation can predicate 93% of 2654 data within ±25% in θ = 2°–15°, 92% of 2254 data within ±15% in θ = 15°–165°, and 80% of 1442 data within ±30% in θ = 165°–178°. The peripheral heat transfer correlation can predict 74% of 903 data and 80% of 700 data, respectively, within 0°–180° and 15°–165° with the deviations of ±30%. The sensitivity analysis indicated that the parameter angle and the distributor height have the most and least significant impact on the peripheral heat transfer correlation, respectively.

Numerical Simulation on Effects of Horizontal Natural Opening Area and Heat Release Rate on Temperature Distribution and Vent Flow in Small Compartment

In this study, the numerical simulation to investigate the effects of horizontal natural opening areas and heat release rates on temperature distribution and vent flow in a small compartment was performed using a fire dynamics simulator. The reduced scale model of a stage in a real scale theater with horizontal natural opening was selected for this study. The horizontal opening areas were 0.0196, 0.1024, and 0.2025 m&lt;sup&gt;2&lt;/sup&gt; (1, 5, and 10% of the floor area, respectively), and the heat release rates were 0.46, 1.35, and 2.61 kW. By decreasing the horizontal opening area and increasing the heat release rate, the temperature in the compartment increased. Additionally, by increasing the heat release rate, the average velocity near the center of the opening increased. For the increase in the horizontal opening area from 0.0196 to 0.1024 m&lt;sup&gt;2&lt;/sup&gt;, the velocity near the center of the opening increased. However, when the horizontal opening area increased from 0.1024 to 0.2025 m&lt;sup&gt;2&lt;/sup&gt;, the variation in velocity was not noticeable. Considering the analyses of temperature and velocity distributions of vent flow, the bidirectional flow pattern was observed, where the outflow and inflow occurred at the center and edge of the horizontal opening, respectively. The mass flow rate through the horizontal opening increased with the increase in the horizontal opening area and heat release rate. The previous correlation for mass flow rate under-predicted the present numerical simulation data.

Healthcare professionals in research (HPiR) Facebook community: a survey of U.K. doctoral and postdoctoral healthcare professionals outside of medicine

BackgroundHealthcare professionals outside of medicine (HCPs), including nurses, midwives and allied health professionals, are increasingly involved in research for patient benefit. Their challenge is to negotiate inter-professional or professionally isolated contexts. The aims of this study were to evaluate the ‘Healthcare Professionals in Research’ (HPiR) Facebook group (a self-directed and confidential peer support group for doctoral and postdoctoral HCPs) including engagement, the experiences of doctoral and postdoctoral HPiR members and to identify future career challenges using an on-line survey.MethodsThe HPiR Facebook group was launched in May 2019. Five HCP Community managers (CMs) were trained in on-line platform curation, moderation and screening. An on-line survey was designed to capture data from HPiR members. A purposive sampling approach was applied. Respondents were required to be doctoral and postdoctoral HCPs and a registered member of the HPiR group. Respondents represented a range of healthcare professions, 79 % of whom had over ten years clinical experience. Membership growth and engagement was analysed. Descriptive statistics were used to present numerical data. Qualitative data were analysed thematically.Results96 members were admitted to the group within the first month. All members were actively engaged with group content. 34/96 doctoral and postdoctoral HCPs completed the survey. Most members joined for networking (88 %) and peer support (82 %) purposes. Analysis of text responses showed difficulties in balancing a clinical academic career and highlighted the consequences of undefined clinical academic roles and pathways.ConclusionsDoctoral and postdoctoral HCPs value the opportunities that HPiR provides for peer support and connection with fellow HCPs. HPiR has the potential to strengthen research capacity, support research skill development and drive change within the clinical academic community. Clinical academic roles and pathways need to be standardised. The creation of opportunities beyond doctoral studies is a priority.

On the time irreversibility of compressible turbulence reflected by particles of various inertias

Time irreversibility of compressible homogeneous isotropic turbulence (HIT) is investigated from a Lagrangian point of view and single-particle statistics. For this purpose, direct numerical simulation (DNS) is implemented for compressible HIT at Taylor-mircoscale Reynolds number Reλ∼100 and turbulent Mach number Mt up to 1.01, in which tracers and inertial particles in a wide Stokes number (St) range are instantaneously tracked with time. The statistics of instantaneous power of particles corroborates that the violation of detailed balance of turbulence in compressible HIT is much stronger than in incompressible HIT. It turns out that the third moment of dimensionless instantaneous power (Ir) of tracers scales as Mt4. A possible explanation based on Kolmogorov-like argument proves to be plausible due to the lacks of direct verification and generality for other moments of the power. A further analysis from an Eulerian point of view suggests that the underlying mechanism for time irreversibility of highly compressible turbulence is quite different from that for weakly compressible or incompressible turbulence. For inertial particles, the moments of instantaneous power are suggested to scale as St−2n/3 at relatively large St numbers, and be dependent only on Mach number or Reynolds number at the small-St number end, which are manifested by the present numerical data. It is further shown that the empirical Mt4 scaling of Ir also approximately applies to various inertial particles, but only at high Mt numbers due to the diminishing effect of compressibility to the low-Mach number end. The time irreversibility announced by the Lagrangian statistical properties of particles of different inertias is shown to be highly associated with their responses to the vortex and shocklet structures in compressible turbulence.

Large-eddy simulation of flow past a circular cylinder for Reynolds numbers 400 to 3900

The benchmarking case of flow past a circular cylinder at the Reynolds number (Re) of 3900 is computed with two open-source codes, OpenFOAM and Nektar++, which are based on the conventional finite volume method (FVM) and the high-order spectral/hp element method, respectively. By using the Nektar++ model, mesh convergence for the case Re = 3900 is demonstrated (perhaps for the first time) through a systematic mesh dependence study, which includes separate examinations of the spanwise domain length (Lz/D), spanwise resolution, and the resolution in the plane perpendicular to the spanwise direction. The computational efficiencies for the Nektar++ and OpenFOAM approaches are then compared. This benchmarking study adds value to the broad Nektar++ and OpenFOAM communities and to the numerical modeling of bluff-body flows in general. Based on the Nektar++ approach, the computations are then generalized to a range of Re = 400–3900. It is found that Lz/D = 3 is adequate for Re = 2500–3900, while an increased Lz/D = 6 is recommended for Re = 400–2000. Based on the present high-fidelity numerical data, the physical mechanisms for the variations in the wake recirculation length and the hydrodynamic forces and pressure on the cylinder with Re are explored. In particular, the physics behind the inverse correlation between the root mean square lift coefficient (CL′) and the wake recirculation length, which includes a significant decrease in CL′ over Re = 270–1500, is highlighted.