Kinetic Energy Analysis Research Articles

The role of flow field dynamics in enhancing volatile organic compound conversion in a surface dielectric barrier discharge system

Abstract This study investigates the correlation between flow fields induced by a surface dielectric barrier discharge (SDBD) system and its application for the volatile organic compound (VOC) gas conversion process. As a benchmark molecule, the conversion of n-butane is monitored using flame ionization detectors, while the flow field is analysed using planar particle image velocimetry. Two individual setups are developed to facilitate both conversion measurement and investigation of induced fluid dynamics. Varying the gap distance between two SDBD electrode plates for three different n-butane mole fractions reveals local peaks in relative conversion around gap distances of 16 mm to 22 mm, indicating additional spatially dependent effects. The lowest n-butane mole fractions exhibit the highest relative conversion, while the highest n-butane mole fraction conversion yields the greatest number of converted molecules per unit time. Despite maintaining constant energy density, the relative conversion exhibits a gradual decrease with increasing distances. The results of the induced flow fields reveal distinct vortex structures at the top and bottom electrodes, which evolve in size and shape as the gap distances increase. These vortices exhibit gas velocity magnitudes approximately seven times higher than the applied external gas flow velocity. Vorticity and turbulent kinetic energy analyses provide insights into these structures' characteristics and their impact on gas mixing. A comparison of line profiles through the centre of the vortices shows peaks in the middle gap region for the same gap distances, correlating with the observed peaks in conversion. These findings demonstrate a correlation between induced flow dynamics and the gas conversion process, bridging plasma actuator studies with the domain of chemical plasma gas conversion.

Effects of submergence ratio on flow around a circular pier in combined wave–current flows using particle image velocimetry

The present study illustrates an experimental investigation of flow hydrodynamics in the vicinity of a submerged circular pier across various submergence levels under only current and wave–current combined flow conditions. The instantaneous velocity data are collected using particle image velocimetry for three distinct frequencies of waves to determine the influence of wave superimposition on the current-induced turbulence parameters. The distribution of phase averaged turbulence quantities, such as mean velocities, Reynolds shear stress, turbulent kinetic energy, flow patterns, and vorticity analysis by Q-criterion, are presented. The results provide insight into the impacts of wave frequency and submergence ratio on the formation of horseshoe vortices, trailing vortex, and reverse flow zones. From the results it is observed that a decrease in the submergence level of the structure causes the formation of strong horseshoe vortices and reverse flow zones in the absence of waves. Also, an increase in wave frequency intensifies the turbulence kinetic energy at the upstream of the pier and eddy generation behind the pier. The present findings highlight the effects of pier submergence and wave characteristics, such as frequency, wave height, and wave period, on flow patterns and turbulent flow characteristics and aid in the design of marine structures. Furthermore, experimental data serve as a valuable resource for validating theoretical or mathematical models related to combined wave–current environments.

Analysis on heat transfer and flow performance of pebble-bed fuel in three regular arrangements with multi-layers

The fuel pebbles in the core of the high-temperature reactor (HTR) are randomly arranged, making it difficult to analyze the heat transfer and flow characteristics quantitatively. Traditionally, three regular fuel pebble arrangements—simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC)—have been used in quantitative studies to determine the possible HTR heat transfer characteristics. However, most currently established arrangement models focus on a few layers, making them inadequate for revealing the variations in heat transfer and flow characteristics with different arrangements and pebble layers. This study established multilayered pebble-bed models for the three arrangements and analyzed the variations in the heat transfer coefficients with increased pebble layers. The reliability of the numerical computational approach was validated through a comparative analysis with experimental data. The study revealed that with the increase of layers, the heat transfer coefficient of SC and FCC arrangement basically stabled at 1480 and 4000 W/(m2·K). The heat transfer coefficient of BCC pronouncedly increased from 2500 to 3500 W/(m2·K). The flow velocity distribution suggested that the increase was caused by a rotation of the helium flow, which became apparent in the ninth layer and stabilized around the thirteenth layer. An analysis of the turbulent kinetic energy showed that this rotation was caused by an increase in turbulence. As the physical properties of helium changed, the flow became unstable and finally entered a new, stable state. Analysis of the boundary conditions at the inlet further supports this view.

Design, Fabrication, and Dynamic Analysis of a MEMS Ring Resonator Supported by Twin Circular Curve Beams.

In this paper, we present a compressive study on the design and development of a MEMS ring resonator and its dynamic behavior under electrostatic force when supported by twin circular curve beams. Finite element analysis (FEA)-based modeling techniques are used to simulate and refine the resonator geometry and transduction. In proper FEA or analytical modeling, the explicit description and accurate values of the effective mass and stiffness of the resonator structure are needed. Therefore, here we outlined an analytical model approach to calculate those values using the first principles of kinetic and potential energy analyses. The natural frequencies of the structure were then calculated using those parameters and compared with those that were simulated using the FEA tool ANSYS. Dynamic analysis was performed to calculate the pull-in voltage, shift of resonance frequency, and harmonic analyses of the ring to understand how the ring resonator is affected by the applied voltage. Additional analysis was performed for different orientations of silicon and assessing the frequency response and frequency shifts. The prototype was fabricated using the standard silicon-on-insulator (SOI)-based MEMS fabrication process and the experimental results for resonances showed good agreement with the developed model approach. The model approach presented in this paper can be used to provide valuable insights for the optimization of MEMS resonators for various operating conditions.

Deepening mechanisms of cut-off lows in the Southern Hemisphere and the role of jet streams: insights from eddy kinetic energy analysis

Abstract. Cut-off lows (COLs) exhibit diverse structures and lifecycles, ranging from confined upper-tropospheric systems to deep, multi-level vortex structures. While COL climatologies are well documented, the mechanisms driving their deepening remain unclear. To bridge this gap, a novel track matching algorithm applied to ERA-Interim reanalysis investigates the vertical extent of Southern Hemisphere COLs. Composite analysis based on structure and eddy kinetic energy budget differentiates four COL categories: shallow, deep, weak, and strong, revealing similarities and disparities. Deep, strong COLs concentrate around Australia and the southwestern Pacific, peaking in autumn and spring, while shallow, weak COLs are more common in summer and closer to the Equator. Despite their differences, both contrasting types evolve energetically via anticyclonic Rossby wave breaking. The distinct roles of jet streams in affecting COL types are addressed: intense polar front jets correlate with more deep COLs, whereas stronger subtropical jets relate to fewer shallow COLs. The COL deepening typically occurs in the presence of a robust upstream polar front jet, which enhances ageostrophic flux convergence and baroclinic processes. The subtropical jet positively correlates with COL intensity but weakens when considering the seasonality, suggesting uncertainties in this relationship. Additionally, we highlight the significance of diabatic processes in COL deepening, addressing their misrepresentation in reanalysis and emphasizing the need for more observational and modelling studies to refine the energetic framework.

Western North Pacific Monsoon Vorticity Distribution as a Potential Driver of Interannual Meridional Migration of the Boreal Summer Synoptic-Scale Wave Train

Abstract On interannual time scales, there is significant meridional migration of the boreal summer (May–October) synoptic-scale wave (SSW) train relative to the summer monsoon trough line over the western North Pacific (WNP) during 1979–2021. The associated plausible physical reasons for the SSW meridional migration are investigated by comparing analyses between two distinct groups: atypical SSW years where SSWs tend to prevail northward of the summer monsoon trough line and typical SSW years where SSWs largely occur along the summer monsoon trough line. During typical SSW years, SSWs originate primarily from equatorial mixed Rossby-gravity (MRG) waves and then develop into off-equatorial tropical depression (TD) waves in the lower troposphere of the monsoon region. During atypical SSW years, SSWs appear to be sourced from upper-level easterlies, propagating downward to the lower troposphere in the monsoon region, with a prevailing TD wave structure. A budget analysis of barotropic eddy kinetic energy suggests that interannual meridional SSW migration is closely related to changes in the vorticity distribution along the summer monsoon trough over the WNP, especially the western part of the summer monsoon trough. These changes cause low-frequency zonal convergence and shear differences, changing barotropic conversion around the monsoon trough and modulating interannual SSW meridional movement. In response to these changes, there are corresponding differences in SSW sources: a predominate MRG–TD wave pattern in typical SSW years and a predominate TD wave pattern in atypical SSW years. These results improve our understanding of the interannual variability of large-scale circulation and tropical cyclones.

DSC Derived (Ea & ΔG) Energetics and Aggregation Predictions for mAbs

The Arrhenius energy of activation of unfolding Ea unfolding and Gibbs free energy of unfolding ΔG unfolding have been calculated utilizing DSC differential scanning calorimetry for 4 mAbs (1 biosimilar) in 3 formulations. DSC derived ΔTm melting temperature changes for each mAb domain (CH2, Fab, CH3) at calorimetric scan rates at 60 °C, 90 °C, 150 °C and 200 °C / hr. were utilized to calculate the kinetic Eaunfolding. The DSC derived Ea trend with observed aggregate formation and can be used to predict%HMW formation post 9-month storage at 5 °C and 40 °C for all formulations analyzed. Additionally, thermodynamic ΔG unfolding energies were also derived (Tm, ΔCp and ΔH measurements) for each mAb at every scan rate to observe scan rate dependence of ΔG and for extrapolation to 0 °C/hr. (to report ΔG at true equilibrium conditions). Both derived thermodynamic ΔG and kinetic Ea energies were combined to build full energetic landscapes for mAb unfolding and aggregation. Statistical multivariate analysis of kinetic (Ea CH2, Ea Fab, Ea CH3) energies, thermodynamic (ΔG5 °C and ΔG40 °C) energies and in-silico modeled surface properties was also performed. Analysis revealed key significant parameters contributing to aggregation. These parameters were utilized to build predictive aggregation models for 25 mg/mL mAb formulations stored 9-months at 5 °C and 40 °C.

The failure causes analysis of low-pressure heater pipes based on the porous medium model and local model

Low-pressure heaters are critical heat exchange equipment in thermal and nuclear power generation. The high-speed steam flow in the low-pressure heaters induces pipe vibration, causing pipe failure. The large size and complex flow make it hard to calculate directly. This paper employs a combined method of the porous medium and local models by substituting the boundary to calculate and prove steam flow trajectory and velocity are consistent with the actual situation. The analysis of the turbulent kinetic energy exhibits that the primary causes of pipe vibration are the periodic vortex shedding and the impact of the impingement plate on the pipes. The stress analysis indicates that the loosening of the pipes leads to a 368 times amplification of the shear stress by 0.1 MPa. The most crucial step in solving such a problem is to strengthen the fixation of the pipes, especially near the shell region.

Effects of inflow Mach numbers on shock train dynamics and turbulence features in a backpressured supersonic channel flow

Investigations on shock train dynamics and relevant turbulence features in a backpressured supersonic channel flow are carried out using direct numerical simulation for three inflow Mach numbers of Ma0= 1.61, 2.0, and 2.45. As Ma0 increases, the shock train undergoes a structural change characterized by the leading shock which changes from the symmetric “λ” (Ma0=1.61) to the symmetric “X” (Ma0=2.00) and then to the asymmetric “X” pattern (Ma0=2.45). The symmetry breaking of shock structures induces asymmetric separation, which significantly alters the distribution characteristics of wall variables such as wall pressure and friction. To examine the unsteady behaviors of the shock train, a mode decomposition technique, namely, reduced-order variational mode decomposition [Liao et al., J. Fluid Mech. 966, A7 (2023)], is adopted taking its merit of adaptively extracting time-frequency features of dynamic systems. The modal analysis reveals that the shock train system exhibits significant centralization of low-frequency energy. Specifically, two basic types of low-frequency oscillation modes dominate the unsteady motion of the shock train: one depicts overall translating oscillation while another represents accordion-like oscillation. The analysis of turbulent kinetic energy shows that turbulence amplification is mainly dominated by the interaction of the decelerating mean flow with streamwise velocity fluctuations in the vicinity of the leading shock for all three cases, which is unaffected by the symmetry breaking of shock structures.

VIV of two rigidly coupled side-by-side cylinders at subcritical [formula omitted

Cross-flow vortex-induced vibration (VIV) of two rigidly coupled circular cylinders in side-by-side arrangement at a Reynolds number of 1000 is numerically investigated using direct numerical simulation. A low mass ratio of 1.27 is considered and the nondimensional centre-to-centre spacing ratio is fixed at 2.0. The reduced velocity ranges from 2 to 13. Three response branches are identified and these responses result in different wake and hydrodynamic characteristics. The cases with large amplitudes feature the co-shedding and lower pressure in the gap, while those with small amplitudes are characterised by two parallel vortex streets. Characterisation and quantification of the flow fields of two rigidly coupled side-by-side cylinders undergoing VIV, which have seldom been reported in the existing research, are elaborated on in this study via the statistical analysis in terms of the turbulent wake visualisation, Reynolds stresses, turbulence kinetic energy (TKE) and proper orthogonal decomposition (POD) analysis. It is found that the cases with large amplitudes show a more unstable wake with sharp increases in the Reynolds stresses and TKE in the near wake. Moreover, the large amplitudes are seen to weaken the asymmetry of the wake and the initial POD modes are more energetic. A reformulated version of the novel force decomposition technique is used to realise the measurement of the time-dependent contributions from each mode to the pressure drag. The large amplitude cases are associated with the drag mode and the lift mode, whereas three modes are observed as the amplitude decreases.

Investigation on radar characteristics of hailstorms seeded with the glaciogenic reagent in Romania

An operational hail suppression program has been based in Romania since 2005. The program is designed to reduce hail damage in the most vulnerable agricultural areas (protected areas) of the country. An exploratory analysis of volume-scan, S-band and C-band radars data, using a storm cell tracking software, was conducted to calculate six radar-derived parameters associated with hail from 51 seeded storms during the summers of 2017 to 2022. All selected hailstorms had a lifetime of more than one hour, which was divided into three stages: before seeding, during seeding, and after seeding. The statistical t-test was used to test the null hypothesis of no seeding effect. Comparing values before seeding and during seeding, the data support claims that seeding causes an increase in most of the analysed parameters. These can indicate the stimulation of the development of seeded clouds, due to the so-called dynamic effect. After seeding, a decrease in the values of all the parameters analysed was observed (with decreases in average values ranging between 10% to 15%). Furthermore, a spatial analysis of hail kinetic energy shows that areas with values over 300 J/m2 are lower in the protected areas compared to the neighbouring ones where the clouds have not been seeded.

Exhaustively Exploring the Prevalent Interaction Pathways of Ligands Targeting the Ligand-Binding Pocket of Farnesoid X Receptor via Combined Enhanced Sampling.

It is well-known that the potency of a drug is heavily associated with its kinetic and thermodynamic properties with the target. Nuclear receptors (NRs), as an important target family, play important roles in regulating a variety of physiological processes in vivo. However, it is hard to understand the drug-NR interaction process because of the closed structure of the ligand-binding domain (LBD) of the NR proteins, which apparently hinders the rational design of drugs with controllable kinetic properties. Therefore, understanding the underlying mechanism of the ligand-NR interaction process seems necessary to help NR drug design. However, it is usually difficult for experimental approaches to interpret the kinetic process of drug-target interactions. Therefore, in silico methods were utilized to explore the optimal binding/dissociation pathways of the NR ligands. Specifically, farnesoid X receptor (FXR) is considered here as the target system since it has been an important target for the treatment of bile acid metabolism-associated diseases, and a series of structures cocrystallized with diverse scaffold ligands were resolved. By using random acceleration molecular dynamics (RAMD) simulation and umbrella sampling (US), 5 main dissociation pathways (pathways I-V) were identified in 11 representative FXR ligands, with most of them (9/11) preferring to go through Pathway III and the remaining two favoring escaping from Pathway I and IV. Furthermore, key residues functioning in the three main dissociation pathways were revealed by the kinetic residue energy analysis (KREA) based on the US trajectories, which may serve as road-marker residues for rapid identification of the (un)binding pathways of FXR ligands. Moreover, the preferred pathways explored by RAMD simulations are in good agreement with the minimum free energy path identified by the US simulations with the Pearson R = 0.76 between the predicted binding affinity and the experimental data, suggesting that RAMD is suitable for applying in large-scale (un)binding-pathway exploration in the case of ligands with obscure binding tunnels to the target.

Non-obstructive hypertrophic cardiomyopathy exhibit subclinical abnormalities in systolic and diastolic ventricular kinetic energy and systolic haemodynamic forces on 4D flow CMR

Abstract Background Patients with non-obstructive hypertrophic cardiomyopathy (nHCM) exhibit a range of anatomical variations including septal, reverse septal, apical, and concentric hypertrophy. Cardiovascular magnetic resonance imaging (CMR) with 4D flow permits assessment of haemodynamic forces (HDF) and kinetic energy (KE) of intraventricular blood flow (1,2). These parameters may indicate subclinical flow inefficiencies which may not be detectable on routine transthoracic echocardiography (3,4). The aim of this study was therefore to investigate if left ventricular (LV) HDF and KE differ between nHCM and controls, and between subgroups of nHCM. Methods Patients with nHCM (n=71) and age- and sex-matched controls (n=20) underwent CMR at 3T (Trio, Siemens) (Table 1). Patients were categorised as phenotype positive (P+) based on presence of hypertrophy (maximum wall thickness ≥15mm, or ≥13mm with a positive family history), and as phenotype negative (P-) referring to pre-hypertrophic sarcomeric variant carriers. Patients with P+ nHCM were classified into subgroups based on the pattern of hypertrophy. Left ventricular HDF and KE were computed over the cardiac cycle using validated modules (1) (Figure 1). Measurements of HDF were based on the Navier-Stokes equations (1), and analysed in three orthogonal directions as root mean square and peak values for systole and diastole. Force ratio was calculated as the sum of the two transverse components divided by the longitudinal component. The Mann-Whitney U test was used for group comparisons, Pearson analysis for correlations, and Fisher’s exact test for binary categorical data. Results P+, P- patients and controls had comparable LV ejection fraction from CMR, LV outflow tract pressure gradients, and diastolic parameters on echocardiography (Table 1). Systolic HDF and force ratio were increased, primarily in the lateral wall-septum direction in septal and reverse septal P+ patients compared to controls, but did not differ in any other directions in P+ compared to P- patients and to controls (Table 1, Figure 1). Diastolic HDF and force ratio did not differ between groups. Systolic KE was increased in P+ patients compared to P- and to controls (Table 1, Figure 1), mainly through increased KE in patients with septal and reverse septal hypertrophy. P+ patients also had increased late diastolic (A-wave) KE relative to P- patients and to controls (Table 1). Both systolic KE and force ratio correlated with maximum wall thickness in patients (r=0.31, p=0.005; r=0.43, p<0.0001). Conclusion In non-obstructive hypertrophic cardiomyopathy, left ventricular HDF and KE analysis from 4D flow CMR detect subclinical flow abnormalities. Increased systolic HDF and KE are linked to the extent and pattern of hypertrophy. Late diastolic A-wave KE was also abnormal in P+ patients despite normal diastolic velocities on echocardiography.Table 1Figure 1

Reynolds stress anisotropy with higher-order turbulence in flow through rigid emergent vegetation: An experimental study

The flow turbulence and Reynolds stress anisotropy in flow over the smooth rigid bed with the emergent rigid vegetation in a straight channel have been experimentally investigated. Higher-order turbulence such as turbulent diffusivity, third-order moments of velocity fluctuation, quadrant analysis and flux of turbulence kinetic energy have been analysed. Reynolds stress anisotropy has been investigated by Anisotropic invariant maps (AIMs) with the use of eigenvalues for both vegetation and non-vegetation condition. In the vegetation zone, more diffusivity occurs and an apparent decrease in velocity causes larger eddies in the outer layer; whereas in the non-vegetation zone, larger eddies formation at near-bed has been found. Quadrant analysis has been done based on relative signs of velocity fluctuation which signifies that Reynolds shear stress is transported from the bed surface to the free surface when flow enters in the vegetation zone from the non-disturbed region. The longitudinal distribution of the anisotropy tensor near the bed surface for the vegetation zone provides the higher anisotropic flow than those of non-vegetation zone. Although, transverse and vertical distributions of the anisotropy tensor in the vicinity of the bed surface for the non-vegetation zone provide a lower anisotropic stream. Flow anisotropy can be understood by AIMs indicating axis-symmetric expansion in a non-vegetation zone whereas axis-symmetric contraction is in the vegetation zone. The outcomes of this study deliver a significant and detailed view of turbulent flow structures in vegetation and non-vegetation zone in an open channel flow.

Horizontal kinetic energy analysis of tropical transition simulations with the WRF and HARMONIE‐AROME models

AbstractFour tropical transition (TT) events in the North Atlantic basin are simulated with the Weather Research and Forecasting (WRF) and the HARMONIE‐AROME (HAR) models to study the main features of the horizontal kinetic energy (HKE) spectra of these kinds of high‐energetic atmospheric system. Though most of the times similar results are obtained with both models, HAR shows a more intense filtering and numerical dissipation, whereas WRF tends to represent overenergized spectra in the synoptic scale and especially at smaller wavelengths. Predictability is dissimilar for the four TTs studied due to the different spectral curve slope obtained for each case, ranging from unlimited to very poor predictability at synoptic scale. Additionally, an increased HKE is presented in the middle–upper troposphere spectra. A deep analysis of the different terms involved in the equation of the spectral energy budget is presented through a detailed study of one of these TTs. The role of all of them is studied, connecting the energy spectra and the meteorological processes involved. The energy budget terms related to the nonlinear spectral transfer, the three‐dimensional divergence, and diabatic process tendencies are identified as the key ones, whereas the potential and kinetic conversion terms and the vertical flux HKE and pressure divergence terms play a secondary role on modulating the spectrum behaviour. The major energetic contributions are found at the synoptic scale, but results show that a two‐dimensional energy cascade does not fully capture the whole spectrum of a TT. The role of convection, latent heat release, and moist convection outbursts is sketched and a link within different vertical levels is found. Results show that a high‐energetic system, such as a TT, can effectively alter the atmospheric energy behaviour.

Boundary Layer Energetics of Rapid Wind and Wave Forced Mixing Events

Abstract The observed development of deep mixed layers and the dependence of intense, deep-mixing events on wind and wave conditions are studied using an ocean LES model with and without an imposed Stokes-drift wave forcing. Model results are compared to glider measurements of the ocean vertical temperature, salinity, and turbulence kinetic energy (TKE) dissipation rate structure collected in the Icelandic Basin. Observed wind stress reached 0.8 N m−2 with significant wave height of 4–6 m, while boundary layer depths reached 180 m. We find that wave forcing, via the commonly used Stokes drift vortex force parameterization, is crucial for accurate prediction of boundary layer depth as characterized by measured and predicted TKE dissipation rate profiles. Analysis of the boundary layer kinetic energy (KE) budget using a modified total Lagrangian-mean energy equation, derived for the wave-averaged Boussinesq equations by requiring that the rotational inertial terms vanish identically as in the standard energy budget without Stokes forcing, suggests that wind work should be calculated using both the surface current and surface Stokes drift. A large percentage of total wind energy is transferred to model TKE via regular and Stokes drift shear production and dissipated. However, resonance by clockwise rotation of the winds can greatly enhance the generation of inertial current mean KE (MKE). Without resonance, TKE production is about 5 times greater than MKE generation, whereas with resonance this ratio decreases to roughly 2. The results have implications for the problem of estimating the global kinetic energy budget of the ocean.

Effect of Aging on Intraventricular Kinetic Energy and Energy Dissipation.

In recent years, analysis of kinetic energy (KE) and the rate of kinetic energy dissipation (KED) or energy loss (EL) within the cardiac chambers, obtained by cardiac imaging techniques, has gained increasing attention. Thus, there is a need to clarify the effect of physiological variables, specifically aging, on these energetic measures. To elucidate this aspect, we reviewed the literature on this topic. Overall, cardiac magnetic resonance and echocardiographic studies published so far indicate that aging affects the energetics of left and right intraventricular blood flow, although not all energy measures during the cardiac cycle seem to be affected by age in the same way. Current studies, however, have limitations. Additional large, multicenter investigations are needed to test the effect of physiological variables on intraventricular KE and KED/EL measures.

Forensic Analysis of A CNC Lathe Window Guard Failure

An analysis of an industrial lathe accident is presented in this paper. During operation, the rotating chuck lost its grip upon the cylindrical workpiece. The detached workpiece impacted the inside of the lathe cabinet, rebounded, struck the composite viewing window, and penetrated it. While observing the machining process through the window, the machinist was struck in the chest by the workpiece. He fell backward, suffering a severe traumatic brain injury when the back of his head impacted the concrete floor. The forensic analysis incorporated an event reconstruction to include an estimate of the ejection angle, velocity, and kinetic energy of the workpiece, the impact energy capacity of the window, and a failure analysis of the window and its frame. A kinetic energy analysis was performed by destructive testing of door/window replicas and high-speed vid-eography. Impact testing of exemplar workpieces against alternative design highly impact-resistant windows was also performed.

Numerical study of transient convective turbulent boundary layer flow along a vertical plate: analysis of kinetic energy and its dissipation rate

ABSTRACT The present article numerically investigates the turbulent buoyancy-driven (natural convection) flow along a vertical plate with a low Reynolds turbulence two-equation k-ϵ model. The deployed turbulence model is appropriate for low Reynolds number (LRN) turbulent flow adjacent to a solid boundary, and the turbulence kinetic energy (TKE) and dissipation rate of TKE are estimated using the momentum equations and are solved simultaneously with the mean flow conservation equations. Two-dimensional time-dependent viscous incompressible turbulent flow is simulated. This flow domain is governed by a highly non-linear group of partial differential equations, namely the time-averaged continuity, momentum, and energy, and also the flow property is determined through TKE, and dissipation rate of TKE equations. Since these equations are not solvable using analytical methods, an implicit second-order finite difference method is employed to solve the governing turbulent flow equations numerically. The simulated time-averaged velocity, temperature, TKE, and dissipation rate of TKE profiles along with friction factor and heat transfer rate are computed for different values of turbulent Reynolds and Prandtl numbers. Average velocity, temperature, turbulence energy, and dissipation rate under both transient and steady-state conditions are decreased with increment in . There is a decrement in average transient velocity and turbulence energy rates with increasing values, whereas the average temperature profile increases. Average steady temperature and turbulence energy profiles are also enhanced with rising values of . The majority of researchers focus on laminar flow and thus far turbulent flow has mainly been addressed through experiments only. To better elucidate the flow in this condition, the novelty of the present study is to utilize a numerical FDM procedure to probe more deeply into the turbulence characteristics in buoyancy-driven (natural convection) flow along a vertical plate with a low Reynolds turbulence two-equation k-ϵ model, as this topic is fundamental to many applications in science and engineering. Furthermore, the results of the turbulent flow simulations obtained from the current model are corroborated with existing results for the special case of laminar flow and a good correlation is achieved.

Barotropic and Nonlinear Decay of the Wintertime Baroclinic Wave Packets over the North Pacific: Energetics Analysis

Abstract Based on daily data from the Japanese 55-year Reanalysis (JRA-55) covering the winters (NDJFM) from 1958 to 2018, this study examines the growth and decay mechanisms of the baroclinic wave packet (BWP) inferred from regression analysis over the North Pacific. Day-to-day kinetic energy (KE) and available potential energy (APE) budget analysis suggest that BWP is driven mainly by baroclinic energy conversion (CPB), barotropic energy conversion (CKB), and the nonlinear term (CKE). CPB acts as a predominant APE source for BWP. Part of CPB acts to overcome the APE loss caused by transient eddy flux and most of it acts as a dominant KE source to drive BWP throughout its lifespan. CKB acts as a KE source before day −1, and as a major KE sink to damp BWP afterward, in which the north–south gradient of the climatological meridional flow plays a key role. Similarly, CKE acts as a KE source before day 0 and as a major KE sink afterward. The damping effect of CKE comes mainly from the scale interaction through the advection of high-frequency meridional momentum by the low-frequency zonal flow. It turns out that the vertical geopotential flux divergence also plays an active role in the dynamical coupling of different vertical BWP parts. There is persistent geopotential flux transfer from the middle-tropospheric layer into the lower- and upper-tropospheric layers, which serves as a major KE source to drive the BWP anomalies for the two layers and a major KE sink for the middle-tropospheric layer where the baroclinic energy conversion is the strongest. Significance Statement Previous studies indicate that baroclinic waves tend to organize into wave packets and are driven by the baroclinic instability. This study finds that the baroclinic waves decay mainly through the barotropic energy conversion and nonlinear processes. The results also indicate that the vertical geopotential flux divergence plays an active role in the dynamical coupling of the BWP anomalies in different layers of the troposphere. It is therefore very important to improve the representations of the climatological-mean flow, wave–mean flow interaction, and wave–wave interaction between high- and low-frequency waves in the midlatitudes, as well as the process of vertical transfer of the geopotential flux in numerical models for a better prediction of weather and climate variability in the extratropic regions.