Turbulent Dynamics Research Articles

Beyond Cryptic Equations: Reimagining Concepts in Physics Through Metaheuristics and Fantasy Stories using Neutrosophic Venn Diagram

Physics, the grand narrative of the universe, has long been viewed as a realm of cold, hard equations. But what if we looked beyond the formulas and considered a more imaginative origin for some of its concepts? This article explores the intriguing possibility that physics, and even cosmology, might share a surprising kinship with metaheuristics and fantastical fiction. Metaheuristics, a branch of computer science, deals with finding approximate solutions to complex problems. Perhaps the universe, in its vastness, employs a set of "rules" that lead to the most likely outcomes, much like an algorithm searching for the best solution within a vast space of possibilities. The connection strengthens when we consider the fantastical. Argentine writer Jorge Luis Borges, known for his thought-provoking short stories, often explored themes of infinity, labyrinths, and forking realities. In this article, we discuss, among other things, how to look at physics laws from an alternative fundamental viewpoint that is fluid dynamics perspective. As an example, we provide an outline for deriving the Newton gravitational law from the Kutta-Joukowski theorem, and then deriving the Kutta-Joukowski theorem from Bernoulli principles. In the meantime, it is known that vortex flows, related to solar convective turbulent dynamics at granular scales and their interplay with magnetic fields within intergranular lanes, occur abundantly on the solar surface and in the atmosphere above.

Modeling and oblique transmission characteristics of an underwater wireless optical communication channel based on ocean depth layering.

Underwater wireless optical communication is widely considered in the field of underwater communication due to its high bandwidth and low latency. In a real transmission link, the temperature and salinity of seawater, chlorophyll concentration, and bubble density vary with ocean depth. Therefore, the depth of the optical transmitter in seawater and the tilt angle of the beam will exhibit different beam transmission characteristics. In this paper, an underwater oblique-range layered channel model considering the combined effects of dynamic turbulence, absorption, and scattering is developed based on real data of seawater at different depths measured by the Global Ocean Observing Buoy Argo and the Woods Hole Oceanographic Institution BCO-DMO. The effects of transmission distance, transmitter tilt angle, and transmitter depth on the oblique-range transmission characteristics of the beam in seawater are discussed. The simulation results show that, at the same transmission distance, the beam centroid displacement increases with an increase in transmitter depth only when the transmitter is located above the interior of the thermocline. When the transmitter is located below the interior of the thermocline, the influence of the transmitter tilt angle on the beam centroid displacement decreases. This indicates that at different depths within the interior of the thermocline, the optical beam transmission characteristics exhibit significant variations.

Development and Validation of a Compressible Reacting Gas-Dynamic Flow Solver for Supersonic Combustion

An approach based on the OpenFOAM library has been developed to solve a high-speed, multicomponent mixture of a reacting, compressible flow. This work presents comprehensive validation of the newly developed solver, called compressibleCentralReactingFoam, with different supersonic flows, including shocks, expansion waves, and turbulence–combustion interaction. The comparisons of the simulation results with experimental and computational data confirm the fidelity of this solver for problems involving multicomponent high-speed reactive flows. The gas dynamics of turbulence–chemistry interaction are modeled using a partially stirred reactor formulation and provide promising results to better understand the complex physics involved in supersonic combustors. A time-scale analysis based on local Damköhler numbers reveals different regimes of turbulent combustion. In the core of the jet flow, the Damköhler number is relatively high, indicating that the reaction time scale is smaller than the turbulent mixing time scale. This means that the combustion is controlled by turbulent mixing. In the shear layer, where the heat release rate and the scalar dissipation rate have the highest value, the flame is stabilized due to finite rate chemistry with small Damköhler numbers and a limited fraction of fine structure. This solver allows three-dimensional gas dynamic simulation of high-speed multicomponent reactive flows relevant to practical combustion applications.

Effects of streamwise rotation on helicity and vortex in channel turbulence

Helicity plays a key role in the evolution of vortex structures and turbulent dynamics. The helicity dynamics and vortex structures in streamwise-rotating channel turbulence are discussed in this paper using the helicity budget equation and the differentiated second-order structure function equation of helicity. Generally, rotation and Reynolds numbers exhibit opposing effects on the interscale helicity dynamics and the vortices. Under the buffer layer, the positions of the helicity peaks are proportional to the ratio between the Reynolds and rotation numbers. The mechanism is related to the opposing effects of convection and rotation. Rotation directly affects the helicity balance through the Coriolis term and corresponding pressure term. In the buffer layer, the scale helicity is negative at small scales but positive at large scales, which is mainly induced by the spatial effects (the production and the spatial turbulent convection) but reduced by interscale cascades. Examination of structures reveals the close association between scale helicity and streaks, with streak lift angles exhibiting an increase with rotation and a decrease with Reynolds numbers. In the log-law layer, the Coriolis terms and corresponding pressure terms are proportional to the rotation numbers but remain independent of the Reynolds numbers. The negative scale helicity is forward cascaded towards small scales. Generally, spanwise vortices in the log-law layer are related to sweep events and forward cascades. Our findings indicate that these spanwise vortices are suppressed by rotation but recover with increasing Reynolds numbers, aligning with the effects observed in the scale helicity balance.

Magnetic flutter effect on validated edge turbulence simulations

Small magnetic fluctuations ( B1/B0∼10−4 ) are intrinsically present in a magnetic confinement plasma due to turbulent currents. While the perpendicular transport of particles and heat is typically dominated by fluctuations of the electric field, the parallel stream of plasma is affected by fluttering magnetic field lines. In particular through electrons, this indirectly impacts the turbulence dynamics. Even in low beta conditions, we find that E × B turbulent transport can be reduced by more than a factor 2 when magnetic flutter is included in our validated edge turbulence simulations of L-mode ASDEX Upgrade. The primary reason for this is the stabilization of drift-Alfvén-waves, which reduces the phase shifts of density and temperature fluctuations with respect to potential fluctuations. This stabilization can be qualitatively explained by linear analytical theory and appreciably reinforced by the flutter nonlinearity. As a secondary effect, the steeper temperature gradients and thus higher η i increase the impact of the ion-temperature-gradient mode on overall turbulent transport. With increasing beta, the stabilizing effect on E × B turbulence increases, balancing the destabilization by induction, until direct electromagnetic perpendicular transport is triggered. We conclude that including flutter is crucial for predictive edge turbulence simulations.

Robustness of partially coherent vortex beams to the impact of dynamic Kolmogorov kind of turbulence

The wave propagation characteristics of Gaussian-Schell model vortex beams passing through a dynamic Kolmogorov type of turbulence are analyzed at the laboratory level. The effect of a rotating pseudo-random phase plate, which simulates Kolmogorov-type atmospheric turbulence, on the Gaussian-Schell model beams carrying twist phase is characterized by calculating the scintillation index and intensity line profiles. Our analysis proves the resilience of Gaussian-Schell model vortex beams to the impact of dynamic turbulence. Simulation studies are further used to validate the experimental results. Because of the resemblance between our investigation conditions and real-world atmospheric turbulence, these findings have potential applications in free-space communication systems.

Characteristics of Turbulence Intermittency, Fine Structure, and Flux Correction in the Taklimakan Desert

Abstract The Taklimakan Desert is one of key climate regions in East Asia, both highly influencing and highly sensitive to local/regional climate change. Based on a comprehensive observation experiment from 1 to 31 May 2022 in the hinterland of the Taklimakan Desert, the characteristics and mechanisms of turbulence intermittency are investigated in this study, with the purpose to correct turbulent fluxes. Using an improved algorithm to decompose turbulence and submeso motions, two intermittency regimes are recognized in the Taklimakan Desert, namely, D and T intermittency and onD intermittency. The former occurs under strongly stable conditions, characterized by the coexistence of dynamic and thermodynamic turbulence intermittency. The latter occurs under strongly unstable conditions and represents only dynamic turbulence intermittency. Physically, the D and T intermittency regime is related to submeso waves, whereas the onD regime is caused by the horizontal convergence/divergence of convective circulations. With the influence of intermittency and submeso motions, the observed turbulent statistics deviate from reality, which would mask the similarity relationships. To overcome the problem, turbulent statistics are corrected by removing submeso components from original fluctuations. The effectiveness of this method is demonstrated based on the flux–gradient relationships. It is also suggested that, for a big dataset, the impact of onD intermittency can be simply corrected by a correction factor while that of D and T intermittency cannot. The results of this study are helpful to develop the parameterization of turbulent exchange processes in the Taklimakan Desert, which is significant to improve the accuracy of weather forecasting and climate prediction. Significance Statement The Taklimakan Desert plays an important role in the evolution of weather and climate in East Asia. With strong surface thermal forcing, turbulence often shows distinctive intermittency, which largely constrains the evaluation of land–atmosphere exchange in this key climate region. This study aims to understand the characteristics of turbulence intermittency and its physical mechanisms, and further to correct the influence of turbulence intermittency on turbulent fluxes in the Taklimakan Desert. This is significant because the results are helpful to improve the parameterization of subgrid processes in the key climate region for atmospheric models, which points the way toward enhancing the accuracy of weather forecasting and climate prediction.

Statistical moments for simulation calibration with model-bridge

Computer simulations are actively used for analyzing complex phenomena, especially in fields where access to their real-world counterparts is not feasible, such as physics, chemistry, material science, and others. The key to executing successful simulations is making sure that the parameters of a simulator reflect real-world scenarios, a tedious and error-prone effort addressed through simulation calibration. Recently, several methods have been proposed to automatize this task by learning from previously calibrated simulations using a model-bridge paradigm: a complex simulation is replaced by a simpler surrogate model, which can then be bridged to the calibrated simulation parameters. However, designing the surrogate model is a non-trivial problem involving trade-offs between simplicity of representation, interpretability and calibration accuracy, as well as the complexity of the bridge model required to map the surrogate to calibrated parameters. Further, while effective, such approaches can be non-intuitive for practitioners due to their distance from the simulation. In this paper, we view a simulation as a distribution of output variables, which can be easily represented by statistical moments. This yields a very simple and interpretable surrogate that can be bridged to calibrated parameters with a simple linear regression. We show that our method outperforms previous approaches, in terms of calibration accuracy and time, through experiments on simulations of turbulent flow dynamics and synthetic signals.

Random Fourier Surrogate for simulation calibration

In this paper we propose Random Fourier Surrogate (RFS) as a method for simulation calibration. Computer simulations are actively used in various fields to model and analyze complex real-world phenomena, enabling practitioners to explore situations inaccessible by other means. To create a simulation that accurately reflects the desired real-world scenario requires calibrating the simulation parameters, a non-trivial process that requires domain expertise and iterative trial-and-error. The model-bridge paradigm has been proposed to automatize this process, where a more computationally efficient surrogate model is used in lieu of the real simulation, and a bridge model is used to map the noninterpretable surrogate parameters to calibrated simulation parameters, which are physically interpretable. Recently an efficient solution called tangent slope-intercept (TSI) descriptors has been proposed, where tangent lines of a principal curve are used to represent the simulation in low dimensionality. However, we find that it has two key problems: it is prone to overfitting and is sensitive to initialization. We address these issues using Random Fourier Features to construct a surrogate model, thereby reducing calibration time by avoiding complex computations, while retaining high accuracy. We evaluate the effectiveness of our method with different experiments on synthetic signal simulations and physical simulations of turbulent flow dynamics.

An effect of dynamic logistics capabilities on courier’s business performance

Courier companies face environmental challenges influenced by the development of e-commerce businesses, demanding high service quality and reliability in meeting consumer demand. Courier companies demand to<br />immediately adjust company strategies to be able to survive in competitive market conditions, the only way is to continue to keep dynamic on internal capability. This study develops and tests a model of the relationship between dynamic logistic capabilities, environmental turbulence, and business performance. As quantitative research, a survey was used to collect data. A sample of 70 valid answers from courier company members of the Association of Indonesian Express Delivery, Postal, and Logistics Services Companies(ASPERINDO) was treated through the Partial Least Square (PLS) method. The research results show a full mediation relationship between dynamic logistics capability and business performance, given the proportion of the impact of dynamic logistics capabilities on business performance (72.7%) identified in this study. As a result, the main result points out that the positive correlation between dynamic logistics capabilities and business performance strengthens the relationship evidence in the literature that dynamic logistics capabilities contribute to business performance, that is, sales growth, delivery reliability and security.

Magnetic power spectrum variability with large-scale total magnetic field fluctuations

The Parker Solar Probe (PSP) is operational since 2018 and has provided invaluable new data that measure the solar vicinity in situ at smaller heliocentric distances than ever before. These data can be used to shed new light on the turbulent dynamics in the solar atmosphere and solar wind, which in turn are thought to be important to explain long-standing problems of the heating and acceleration in these regions. In recent years, it was realized that background inhomogeneities in magnetohydrodynamics could influence the development of turbulence and might enable other cascade channels, such as the self-cascade of waves, in addition to the well-known Alfvén collisional cascade. This phenomenon has been called uniturbulence. However, the precise influence of the background inhomogeneity on turbulent spectra has not been not studied so far. In this work, we study the influence of background roughness on the turbulent magnetic field spectrum in PSP data, including data from encounter 1 up to and including encounter 14. The magnetic spectral index $ receives our highest attention. Motivated by the presumably different turbulent dynamics in the presence of large-scale inhomogeneities, we searched for correlations between the magnetic power spectra and a measure for the degree of inhomogeneity. The latter was probed by taking the standard deviation (STD) of the total magnetic field magnitude after applying an appropriate averaging. The data of each PSP encounter were split into many short time windows, of which we subsequently calculated both $ and background STD. We find a significant impact of the background STD on $ As the variations in the background become stronger, $ becomes more negative, indicating a steepening of the magnetic power spectrum. We show that this effect is consistent in all investigated PSP encounters, and it is unaffected by heliocentric distance up to $50 R_ By making use of artificial magnetic field data in the form of synthetic colored noise, we show that this effect is not simply due to the fluctuations imposed on the total magnetic field, but must have another as yet unidentified cause. There is a strong indication that the background inhomogeneity affects the turbulent dynamics, possibly through uniturbulence. This leads to a different power spectrum in the presence of large-scale total magnetic field variations. The fact that it is present in all investigated encounters and at all radial distances up to $50 R_ suggests that it represents a general and ubiquitous feature of solar wind dynamics. The analysis with the synthetic colored noise indicates that the observed steepening effect is not to be attributed simply to the small-scale fluctuations superposed on the total magnetic field. This conclusion is confirmed by the fact that no similar consistent steepening trend is observed for the magnetic compressibility $C_b$ instead of background STD. The steepening trend is instead a real physical effect induced by the large-scale variations in the background magnetic field.

Analysis of the Relationship Between the Morphological Characteristics of Lightning Channels and Turbulent Dynamics Based on the Localization of VHF Radiation Sources

AbstractLightning channel morphology depends on the thunderstorm cloud charge structure, which in turn is influenced by the thunderstorm dynamics. In this paper, based on three‐dimensional radiation source localization data from the Lightning Mapping Array and radar‐based data, our analysis shows that the overall morphology and detailed morphology of the lightning channel correspond to different eddy dissipation rate (EDR) characteristics. Lightning with complex channel morphology occurs in regions with large EDRs. In single lightning events, channels that extend directly within a certain height range without significant bifurcation and turning tend to propagate in the direction of decreasing EDRs, while channel bifurcations and turns usually occur in regions with large radial velocity gradients and large EDRs. This study shows the relationship between channel morphology and thunderstorm dynamics and provides a new method for the direct application of channel‐level localization data to understand thunderstorm dynamics characteristics.

Impact of urban canopy characteristics on turbulence dynamics: Insights from large eddy simulation

In this study, a series of large-eddy simulations are conducted to explore the dynamics of turbulence within the urban canopy. Two idealized urban-like geometries (staggered and aligned arrays of cubes) and one real urban region (located on the Southern University of Science and Technology campus in China) are simulated under neutral atmospheric conditions. The results show a significant difference in the dispersive momentum fluxes between OpenFOAM and PALM within the ultra-dense arrays. Furthermore, it is found that the spatial layout does not exert a significant effect on the budget of turbulent kinetic energy. Instead, it mainly depends on the ratio of the building surface area to the total surface area, i.e., packing density. In addition, a multi-scale coupled inflow boundary condition is introduced in this study to simulate the flow in a real urban area. This boundary condition yields a better match to the LiDAR measurements than the Weather Research and Forecasting model data. Finally, this study shows that the mean velocity obtained from the campus of SUSTech is in satisfactory agreement with the data from low-density idealized cube arrays and the corresponding urban canopy model. This observation suggests that mean wind speeds within partially occupied urban areas are relatively independent of wind direction, thus greatly improving the application of urban canopy models to such scenarios.

Four-dimensional variational data assimilation of a turbulent jet for super-temporal-resolution reconstruction

The super-temporal-resolution (STR) reconstruction of turbulent flows is an important data augmentation application for increasing the data reach in measurement techniques and understanding turbulence dynamics. This paper proposes a data assimilation (DA) strategy based on weak-constraint four-dimensional variation to conduct an STR reconstruction in a turbulent jet beyond the Nyquist limit from given low-sampling-rate observations. Highly resolved large-eddy simulation (LES) data are used to produce synthetic measurements, which are used as observations and for validation. A segregated assimilation procedure is realised to assimilate the initial condition, inflow boundary condition and model error separately. Different types of observational data are tested. The first type is down-sampled LES data containing many small-scale turbulence structures with or without synthetic noise. The DA results show that the temporal variation of the small-scale structures is well recovered even with noise in the observations. The spectra are resolved to a frequency approximately one order of magnitude higher than what can be captured within the Nyquist limit. The second type of observation is low-sampling-rate tomographic particle image velocimetry (tomo-PIV) data with or without the injection of small-scale structures. The modulation between the large-scale structures contained in the tomo-PIV fields and the small scales injected from the observations is improved. The resultant small scales in the STR reconstruction have the characteristics of authentic turbulence to a considerable extent. Additionally, DA yields much smaller errors in the prediction of particle positions when compared with the Wiener filter, demonstrating the great potential for Lagrangian particle tracking in measurement techniques.

Structures of Lateral Flow and Turbulence in a Breaking Tidal Bore Rushing through a Curved Channel of the Qiantang Estuary

Abstract Tidal bores form in distinct funnel-shaped estuaries and bays initially and cause unique flow and turbulence dynamics when passing through meandering channels, such as in the Qiantang Estuary, Amazon River Estuary, and Seine River Estuary. To understand the lateral currents and turbulence processes of tidal bores in curved channels, velocity profiles and free-surface elevations are sampled for four semidiurnal tidal cycles in a curved channel located upstream of the Qiantang Estuary. During flood tides, the evolution of lateral currents experiences three distinct phases: first, there are inner-bank-toward lateral currents at the front of tidal bores, followed by two-layer helical currents in the middle of the flood tides, and finally, outer-bank-pointing lateral currents at the end of flood tides. Tidal bore breaking creates outbursts of turbulent kinetic energy. The enhanced turbulence emerges above the middle layers and persists for more than 10 minutes after the breaking front. The lateral momentum balance indicates that the decreasing lateral barotropic pressure gradient (LBTPG) and the increasing summation of centrifugal and Coriolis acceleration give rise to the variation in lateral currents. The phase lead of bores near the outer bank induced by shoal-channel topography generates an inner-bank-pointing LBTPG at the bore front and then gradually weakens it. Significant turbulence following bore breaking may be induced via the wave-induced turbulence mechanism by violent secondary waves. This research shows that complicated lateral currents are an important component of tidal bores flowing through meandering channels and that secondary waves after bore breaking can continually feed turbulence. Significance Statement The purpose of this study is to discern and explain the variation in lateral flows and turbulence when tidal bores rush through a curved estuarine channel. Lateral currents and turbulence play important roles in momentum exchange, scalar dispersion, and transverse topography evolution. Moreover, the discussion on lateral flows is necessary to extend the understanding of tidal bore hydrodynamics from the x–z dimension to the x–y–z dimension. In situ observations reveal that a complicated but regular pattern of lateral currents occurred in every tidal cycle and that there was significant turbulence at the tidal bore front. Our findings show that the lateral difference in tidal bore propagation speed caused by shoal-channel topography in the curved bend is an essential reason for the generation of lateral currents and that the secondary waves simulated by bore breaking can continuously feed tidal bore turbulence.

Can't read my broker face?—Tracing a motif and metaphor of expert knowledge through audiovisual images of the financial crisis

AbstractBased on the question of the representability of economy and economics in audiovisual media, developments on the financial markets have often been discussed as a depiction problem. The abstractness and complexity of economic interrelations seem to defy classical modes of storytelling and dramatization. Nevertheless, public opinion about economic changes and dependencies crucially relies on audiovisual media. But how can the public communicate in images, sounds, and words about forces that are out of sight and out of reach, and can supposedly only be adequately grasped by experts? In a case study on audiovisual images of the global financial crisis (2007–), this paper tracks and analyzes a recurring motif: the staging of expert knowledge as close‐ups of expressive faces vis‐à‐vis computer screens in television news, documentaries, as well as feature films. It draws on the use of digital tools for corpus exploration (reverse image search) and the visualization of video annotations. By relating and comparing different staging strategies by which these “broker faces” become embodiments of turbulent market dynamics, the paper proposes to not regard them as repeated instantiations of the same metaphor, but as a developing web of cinematic metaphors. Different perspectives (news of market developments or historical accounts of crisis developments) and affective stances toward the global financial crisis are expressed in these variations of the face‐screen constellation. The paper thus presents a selection of different appearances of “broker faces” as a medium for an audiovisual discourse of the global financial crisis. A concluding analysis of a scene from Margin Call focuses on its specific intertwining of expert and screen as an ambivalent movement figuration of staging insight. Between the feeling of discovery (of a potential future threat) and the sense of being haunted (by a menacing force), the film stages the emergence of a “broker face” in an atmospheric tension between suspense and melancholy. We argue that the film thereby reframes the motif and poses questions of agency, temporality, and expert knowledge.

Extinction of buoyant turbulent non-premixed flames under reduced oxygen concentrations

Local and global extinction of 10 kW buoyant turbulent non-premixed flames of methane from a 13.7 cm diameter burner under oxygen concentrations (OCs) from 20.9 % to 12 % are investigated using a combination of OH* chemiluminescence imaging and exhaust-gas sampling. Local flame extinction, indicated by holes or discontinuities in the OH* images, is only observed at OC lower than 17 %. For OC below 16 %, large-scale turbulent flow dynamics causes rapid creation of large extinction holes that do not reclose, and the overall combustion efficiency (η) decreases rapidly as local extinction becomes more probable. Direct observation of local extinction in buoyant turbulent flames provides important physical insights and validation data for models of extinction and re-ignition by distinguishing their respective contributions to η. We observe that local extinction events are associated with large-scale flow features, leading us to hypothesize that extinction behavior correlates with resolved-scale strain rates from large-eddy simulation (LES) in excess of the laminar extinction limit. This idea is investigated by performing LES for the target flame, extracting strain-rate statistics on the flame surface, and comparing these to both the extinction limits for canonical counterflow diffusion flames and to the experimentally observed extinction behavior. Results show that the cumulative distribution of turbulent flame strain rates up to the laminar extinction limit closely follows the measured OC dependence of η. This approach to η works well for different OCs and other fuels such as propane and ethylene, which suggests great potential for the development of computationally efficient extinction models for fire suppression.

Comparison of numerical results of turbulence models for the problem of heat transfer in turbulent molasses

The study introduces Malikov's two-fluid methodology along with the RSM turbulence model for simulating turbulent heat transfer phenomena. It elucidates that temperature fluctuations within turbulent flows arise from temperature differentials between the respective fluids. Leveraging the two-fluid paradigm, the researchers develop a mathematical framework to characterize turbulent heat transfer dynamics. This resultant turbulence model is then applied to analyze heat propagation in turbulent flows around a flat plate and in scenarios involving submerged jets. To validate the model's efficacy, numerical outcomes are juxtaposed against established RSM turbulence models and experimental findings. The comparative analysis reveals that the two-fluid turbulent transport model aptly captures the thermodynamic behaviors inherent in turbulent flows with exceptional precision.

Designing a Convection‐Cloud Chamber for Collision‐Coalescence Using Large‐Eddy Simulation With Bin Microphysics

AbstractCollisional growth of cloud droplets is an essential yet uncertain process for drizzle and precipitation formation. To improve the quantitative understanding of this key component of cloud‐aerosol‐turbulence interactions, observational studies of collision‐coalescence in a controlled laboratory environment are needed. In an existing convection‐cloud chamber (the Pi Chamber), collisional growth is limited by low liquid water content and short droplet residence times. In this work, we use numerical simulations to explore various configurations of a convection‐cloud chamber that may intensify collision‐coalescence. We employ a large‐eddy simulation (LES) model with a size‐resolved (bin) cloud microphysics scheme to explore how cloud properties and the intensity of collision‐coalescence are affected by the chamber size and aspect ratio, surface roughness, side‐wall wetness, side‐wall temperature arrangement, and aerosol injection rate. Simulations without condensation and evaporation within the domain are first performed to explore the turbulence dynamics and wall fluxes. The LES wall fluxes are used to modify the Scalar Flux‐budget Model, which is then applied to demonstrate the need for non‐uniform side‐wall temperature (two side walls as warm as the bottom and the two others as cold as the top) to maintain high supersaturation in a tall chamber. The results of LES with full cloud microphysics reveal that collision‐coalescence is greatly enhanced by employing a taller chamber with saturated side walls, non‐uniform side‐wall temperature, and rough surfaces. For the conditions explored, although lowering the aerosol injection rate broadens the droplet size distribution, favoring collision‐coalescence, the reduced droplet number concentration decreases the frequency of collisions.

Numerical Analysis of Turbulent Air Flow Dynamics in a Rectangular Channel with Perforated Nozzle-Shaped Vertical Baffles

Numerical Analysis of Turbulent Air Flow Dynamics in a Rectangular Channel with Perforated Nozzle-Shaped Vertical Baffles