Journal articles on the topic 'Turbulence of the environment'
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HORCHANI, SAMAH CHEMLI, and MAHMOUD ZOUAOUI. "ENVIRONMENT TURBULENCE EFFECT ON THE DYNAMICS OF INTELLECTUAL CAPITAL ACCUMULATION AND AMBIDEXTROUS INNOVATION." International Journal of Innovation Management 25, no. 05 (February 5, 2021): 2150058. http://dx.doi.org/10.1142/s1363919621500584.
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The aim of this paper is to study the influence of the environment on the link between intellectual capital and ambidextrous innovation. The environment has been considered taking into account the technological turbulence and the market turbulence. Using a questionnaire survey approach, data were obtained from 155 directors representing Tunisian SMEs. Two main theoretical implications were highlighted. The first is the extent of the intellectual capital contribution, with its human, organizational and relational components, to the reading of the ambidextrous innovation within the organization. The second is the moderating role of environmental turbulence. From a practical side, the study tried to reap the intellectual capital benefits and the intermediate effect of environmental turbulence to improve the manager’s yields in term of innovation. Interestingly, results show that human capital affects ambidextrous innovation. It influences radical innovation more than incremental innovation. Relationship capital promotes only incremental innovation. Organizational capital influences ambidextrous innovation. Its effect on incremental innovation is greater than on radical innovation. Both technological and market turbulences moderate negatively the human capital effect on incremental innovation. Counter to our expectations, however, environmental turbulence does not moderate the interrelationships selectively between relational capital, organizational capital and ambidextrous innovation. The present study is one of the few studies conducted in Tunisia investigating the field of intellectual capital and the first studying its effect on the ambidextrous innovation in a turbulent environment.
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Hong, J., J. Kim, H. Ishikawa, and Y. Ma. "Surface layer similarity in the nocturnal boundary layer: the application of Hilbert-Huang transform." Biogeosciences 7, no. 4 (April 19, 2010): 1271–78. http://dx.doi.org/10.5194/bg-7-1271-2010.
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Abstract. Turbulence statistics such as flux-variance relationship are critical information in measuring and modeling ecosystem exchanges of carbon, water, energy, and momentum at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT), this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environments such as nocturnal stable boundary layer.
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Kharshiladze, O., and K. Chargazia. "Investigation of the strong turbulence in the geospace environment." Advances in Radio Science 13 (November 3, 2015): 243–50. http://dx.doi.org/10.5194/ars-13-243-2015.
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Abstract. Plasma vortices are often detected by spacecraft in the geospace (atmosphere, ionosphere, magnetosphere) environment, for instance in the magnetosheath and in the magnetotail region. Large scale vortices may correspond to the injection scale of turbulence, so that understanding their origin is important for understanding the energy transfer processes in the geospace environment. In a recent work, turbulent state of plasma medium (especially, ionosphere) is overviewed. Experimental observation data from THEMIS mission (Keiling et al., 2009) is investigated and numerical simulations are carried out. By analyzing the THEMIS data for that event, we find that several vortices in the magnetotail are detected together with the main one and these vortices constitute a vortex chain. Such vortices can cause the strong turbulent state in the different media. The strong magnetic turbulence is investigated in the ionsophere as an ensemble of such strongly localized (weakly interacting) vortices. Characteristics of power spectral densities are estimated for the observed and analytical stationary dipole structures. These characteristics give good description of the vortex structures.
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Stuck, Maxime, Alvaro Vidal, Pablo Torres, Hassan M. Nagib, Candace Wark, and Ricardo Vinuesa. "Spectral-Element Simulation of the Turbulent Flow in an Urban Environment." Applied Sciences 11, no. 14 (July 13, 2021): 6472. http://dx.doi.org/10.3390/app11146472.
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The mean flow and turbulence statistics of the flow through a simplified urban environment, which is an active research area in order to improve the knowledge of turbulent flow in cities, is investigated. This is useful for civil engineering, pedestrian comfort and for health concerns caused by pollutant spreading. In this work, we provide analysis of the turbulence statistics obtained from well-resolved large-eddy simulations (LES). A detailed analysis of this database reveals the impact of the geometry of the urban array on the flow characteristics and provides for a good description of the turbulent features of the flow within a simplified urban environment. The most prominent features of this complex flow include coherent vortical structures such as the so-called arch vortex, the horseshoe vortex and the roof vortex. These structures of flow have been identified by an analysis of the turbulence statistics. The influence of the geometry of urban environment (and particularly the street width and the building height) on the overall flow behavior has also been studied. Finally, the well-resolved LES results were compared with an available experimental database to discuss differences and similarities between the respective urban configurations.
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Wang, Zhenchuan, Guoli Qi, and Meijun Li. "Discussion on improved method of turbulence model for supercritical water flow and heat transfer." Thermal Science 24, no. 5 Part A (2020): 2729–41. http://dx.doi.org/10.2298/tsci190813007w.
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The turbulence model fails in supercritical fluid-flow and heat transfer simulation, owing to the drastic change of thermal properties. The inappropriate buoyancy effect model and the improper turbulent Prandtl number model are several of these factors lead to the original low-Reynolds number turbulence model unable to predict the wall temperature for vertically heated tubes under the deteriorate heat transfer conditions. This paper proposed a simplified improved method to modify the turbulence model, using the generalized gradient diffusion hypothesis approximation model for the production term of the turbulent kinetic energy due to the buoyancy effect, using a turbulence Prandtl number model for the turbulent thermal diffusivity instead of the constant number. A better agreement was accomplished by the improved turbulence model compared with the experimental data. The main reason for the over-predicted wall temperature by the original turbulence model is the misuse of the buoyancy effect model. In the improved model, the production term of the turbulent kinetic energy is much higher than the results calculated by the original turbulence model, especially in the boundary-layer. A more accurate model for the production term of the turbulent kinetic energy is the main direction of further modification for the low Reynolds number turbulence model.
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Falgarone, E., P. Hily-Blant, J. Pety, and G. Pineau des Forêts. "The turbulent environment of low-mass dense cores." Proceedings of the International Astronomical Union 2, S237 (August 2006): 24–30. http://dx.doi.org/10.1017/s1743921307001172.
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AbstractThe signatures of intermittent dissipation of turbulent energy have been sought in the translucent environment of a low-mass dense core. Molecular line observations reveal a network of narrow filamentary structures, found on statistical grounds to be the locus of the largest velocity shears. Three independent properties of these structures make them the plausible sites of intermittent dissipation of turbulence: (1) gas there is warmer and more diluted than average, (2) it bears the signatures of a non-equilibrium chemistry triggered by impulsive heating due to turbulence dissipation, and (3) the power that these structures radiate in the gas cooling lines (mostly H2) is so large that it balances the total energy injection rate of the turbulent cascade, for a volume filling factor of only a few percents, consistent with other observations in the Solar Neighborhood. These filamentary structures may act as tiny seeds of gas condensation in diffuse molecular gas. They do not exhibit the properties of steady-state low-velocity magneto-hydrodynamic (MHD) shocks, as presently modelled.
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Hong, J., J. Kim, H. Ishikawa, and Y. Ma. "Surface layer similarity in the nocturnal boundary layer: the application of Hilbert-Huang transform." Biogeosciences Discussions 6, no. 5 (October 8, 2009): 9677–99. http://dx.doi.org/10.5194/bgd-6-9677-2009.
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Abstract. Turbulence statistics such as flux-variance relationship is critical information in measuring and modeling carbon, water, energy, and momentum exchanges at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT), this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding of the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environment such as nocturnal stable boundary layer.
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Vohra, Veena. "Organizational environments and adaptive response mechanisms in India." Journal of Indian Business Research 7, no. 1 (March 16, 2015): 21–44. http://dx.doi.org/10.1108/jibr-01-2014-0001.
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Purpose – The purpose of this paper is to investigate the nature of the organizational environments of Indian business organizations and to identify the adaptive response mechanisms that organizations use to cope with their environments. This paper also examines in detail the causal texture of the organizational environments and attempts to build a conceptual model mapping adaptive responses of organizations to different types of organizational environments. Design/methodology/approach – A constructivist stance was adopted in this exploratory study to capture the perceptions of the organizational leaders through the multiple case study design to capture the features of the organizational environments and their causal texture. The multiple case study design used an embedded mixed-methods approach to collect data. Within-case analysis and cross-case analysis were conducted to draw out prominent themes across cases ordered for particular organizational environment types. The study was conducted by following construct validity, internal reliability and external validity guidelines. Findings – The study highlights and describes in detail the characteristics of the different organizational environment types in India. It is revealed that a majority of Indian organizations exist in turbulent environments. There are differences in the adaptive response mechanisms of organizations in the environment types studied. The study specially focuses on the strategies adopted by Indian organizations to adapt to turbulent environments. Practical implications – This study maps the causal texture of organizational environments in India and maps the organizational adaptive responses to the environment for greater effectiveness. This study offers various strategies to cope with turbulent organizational environments and adds to the research focus on causal texture and adaptive capacities of organizations across different types of environments. Originality/value – This study contributes to an ignored subject area of organizational environments. Managing organizations in uncertain and turbulent environments is complex, and this study provides an understanding about the various types of adaptive mechanism that are used to cope with environmental turbulence. This study also attempts to answer several questions that previous research works have raised about strategies that organizations use when they fail to cope with environmental turbulence.
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Chen, Sisi, Peter Bartello, M. K. Yau, P. A. Vaillancourt, and Kevin Zwijsen. "Cloud Droplet Collisions in Turbulent Environment: Collision Statistics and Parameterization." Journal of the Atmospheric Sciences 73, no. 2 (February 1, 2016): 621–36. http://dx.doi.org/10.1175/jas-d-15-0203.1.
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Abstract The purpose of this paper is to quantify the influence of turbulence in collision statistics by separately studying the impacts of computational domain sizes, eddy dissipation rates (EDRs), and droplet sizes and eventually to develop an accurate parameterization of collision kernels. Direct numerical simulations (DNS) were performed with a relatively wide range of EDRs and Taylor microscale Reynolds numbers . EDR measures the turbulence intensity levels. DNS model studies have simulated homogeneous turbulence in a small domain in the cloud’s adiabatic core. Clouds clearly have much larger scales than current DNS can simulate. For this reason, it is emphasized that obtained from current DNS is fundamentally only a measure of the computational domain size for a given EDR and cannot completely describe the physical properties of cloud turbulence. Results show that the collision statistics are independent of the domain sizes and hence of the computational for droplet sizes no bigger than 25 μm as long as the droplet separation distance, which is on the order of the Kolmogorov scale in real clouds, is resolved. Instead, they are found to be highly correlated with EDRs and droplet sizes, and this correlation is used to formulate an improved parameterization scheme. The new scheme well represents the turbulent geometric collision kernel with a relative uncertainty of 14%. A comparison between different parameterizations is made, and the formulas proposed here are shown to improve the fit to the collision statistics.
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Zimbardo, G., A. Greco, L. Sorriso-Valvo, S. Perri, Z. Vörös, G. Aburjania, K. Chargazia, and O. Alexandrova. "Magnetic Turbulence in the Geospace Environment." Space Science Reviews 156, no. 1-4 (September 25, 2010): 89–134. http://dx.doi.org/10.1007/s11214-010-9692-5.
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Balduzzi, Francesco, Marco Zini, Andreu Carbó Molina, Gianni Bartoli, Tim De Troyer, Mark C. Runacres, Giovanni Ferrara, and Alessandro Bianchini. "Understanding the Aerodynamic Behavior and Energy Conversion Capability of Small Darrieus Vertical Axis Wind Turbines in Turbulent Flows." Energies 13, no. 11 (June 8, 2020): 2936. http://dx.doi.org/10.3390/en13112936.
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Small Darrieus vertical-axis wind turbines (VAWTs) have recently been proposed as a possible solution for adoption in the built environment as their performance degrades less in complex and highly-turbulent flows. Some recent analyses have even shown an increase of the power coefficient for the large turbulence intensities and length scales typical of such environments. Starting from these insights, this study presents a combined numerical and experimental analysis aimed at assessing the physical phenomena that take place during the operation of a Darrieus VAWT in turbulent flows. Wind tunnel experiments provided a quantification of the performance variation of a two-blade VAWT rotor for different levels of turbulence intensity and length scale. Furthermore, detailed experiments on an individual airfoil provided an estimation of the aerodynamics at high turbulence levels and low Reynolds numbers. Computational fluid dynamics (CFD) simulations were used to extend the experimental results and to quantify the variation in the energy content of turbulent wind. Finally, the numerical and experimental inputs were synthetized into an engineering simulation tool, which can nicely predict the performance of a VAWT rotor under turbulent conditions.
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Barnett, Sasha, Joseph Blau, Paul Frederickson, and Keith Cohn. "Measurements and Modeling of Optical Turbulence in the Coastal Environment." Applied Sciences 12, no. 10 (May 12, 2022): 4892. http://dx.doi.org/10.3390/app12104892.
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The goal of this study was to characterize optical turbulence in the near-coastal environment. Measurements to obtain the refractive index structure parameter and other meteorological data were taken over the course of a month along the shore of Monterey Bay. The results were compared to a new version of the Navy Vertical Surface Layer Model (NAVSLaM), a model of turbulence originally developed for maritime environments but now extended to terrestrial environments. The new version has not been previously validated by comparisons to experiments, particularly in a complex environment such as near the coastline. Our experimental results showed generally good agreement between measured and modeled levels of turbulence. Specifically, the differences between experimental and modeled values of the refractive index structure parameter were less than an order of magnitude in most conditions and followed the same diurnal trend. There were some greater differences during near-neutral conditions, but this is a known limitation of the model. Overall, this extended model appears to do a good job of predicting turbulence in this environment for the observed time period.
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Barber, Katelyn A., and Gretchen L. Mullendore. "The Importance of Convective Stage on Out-of-Cloud Convectively Induced Turbulence from High-Resolution Simulations." Monthly Weather Review 148, no. 11 (November 2020): 4587–605. http://dx.doi.org/10.1175/mwr-d-20-0065.1.
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AbstractTurbulence (clear-air, mountain wave, convectively induced) is an aviation hazard that is a challenge to forecast due to the coarse resolution ultilized in operational weather models. Turbulence indices are commonly used to aid pilots in avoiding turbulence, but these indices have been designed and calibrated for midlatitude clear-air turbulence prediction (e.g., the Ellrod index). A significant limitation with current convectively induced turbulence (CIT) prediction is the lack of storm stage dependency. In this study, six high-resolution simulations of tropical oceanic and midlatitude continental convection are performed to characterize the turbulent environment near various convective types during the developing and mature stages. Second-order structure functions, a diagnostic commonly used to identify turbulence in turbulence prediction systems, are used to characterize the probability of turbulence for various convective types. Turbulence likelihood was found to be independent of region (i.e., tropical vs midlatitude) but dependent on convective stage. The probability of turbulence increased near developing convection for the majority of cases. Additional analysis of static stability and vertical wind shear, indicators of turbulence potential, showed that the convective environment near developing convection was more favorable for turbulence production than mature convection. Near developing convection, static stability decreased and vertical wind shear increased. Vertical wind shear near mature and developing convection was found to be weakly correlated to turbulence intensity in both the tropics and the midlatitudes. This study emphasizes the need for turbulence avoidance guidelines for the aviation community that are dependent on convective stage.
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Pécseli, Hans L., Jan K. Trulsen, Jan Erik Stiansen, and Svein Sundby. "Feeding of Plankton in a Turbulent Environment: A Comparison of Analytical and Observational Results Covering Also Strong Turbulence." Fluids 5, no. 1 (March 19, 2020): 37. http://dx.doi.org/10.3390/fluids5010037.
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The present studies address feeding of plankton in turbulent environments, discussed by a comparison of analytical results and field data. Various models for predator-prey encounters and capture probabilities are reviewed. Generalized forms for encounter rates and capture probabilities in turbulent environments are proposed. The analysis emphasizes ambush predators, exemplified by cod larvae Gadus morhua L. in the start-feeding phase (stage 7 larvae) collected in shallow waters near Lofoten, Norway. During this campaign, data were obtained at four sites with strongly turbulent conditions induced by tidal currents and long-wave swells, and one site where the turbulence had a lower level in comparison. The guts of the selected cod larvae were examined in order to determine the number of nauplii ingested. Analytically obtained probability densities for the gut content were compared with observations and the results used for estimating the rate of capture of the nauplii. This capture rate was then compared with analytical results using also data for the surroundings, such as measured prey densities and turbulence conditions, as quantified by the specific energy dissipation rate. Different from earlier studies, the presented data include conditions where the turbulence exceeds the level for optimal larval encounter-capture rates.
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Alhumairi, Mohammed, and Özgür Ertunç. "Active-grid turbulence effect on the topology and the flame location of a lean premixed combustion." Thermal Science 22, no. 6 Part A (2018): 2425–38. http://dx.doi.org/10.2298/tsci170503100a.
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Lean premixed combustion under the influence of active-grid turbulence was computationally investigated, and the results were compared with experimental data. The experiments were carried out to generate a premixed flame at a thermal load of 9 kW from a single jet flow combustor. Turbulent combustion models, such as the coherent flame model and turbulent flame speed closure model were implemented for the simulations performed under different turbulent flow conditions, which were specified by the Reynolds number based on Taylor?s microscale, the dissipation rate of turbulence, and turbulent kinetic energy. This study shows that the applied turbulent combustion models differently predict the flame topology and location. However, similar to the experiments, simulations with both models revealed that the flame moves toward the inlet when turbulence becomes strong at the inlet, that is, when Re? at the inlet increases. The results indicated that the flame topology and location in the coherent flame model were more sensitive to turbulence than those in the turbulent flame speed closure model. The flame location behavior on the jet flow combustor significantly changed with the increase of Re?.
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Watanabe, Tomoaki, James J. Riley, Koji Nagata, Ryo Onishi, and Keigo Matsuda. "A localized turbulent mixing layer in a uniformly stratified environment." Journal of Fluid Mechanics 849 (June 18, 2018): 245–76. http://dx.doi.org/10.1017/jfm.2018.400.
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Localized turbulence bounded by non-turbulent flow in a uniformly stratified environment is studied with direct numerical simulations of stably stratified shear layers. Of particular interest is the turbulent/non-turbulent interfacial (TNTI) layer, which is detected by identifying the turbulent region in terms of its potential vorticity. Fluid near the outer edge of the turbulent region gains potential vorticity and becomes turbulent by diffusion arising from both viscous and molecular effects. The flow properties near the TNTI layer change depending on the buoyancy Reynolds number near the interface,$Re_{bI}$. The TNTI layer thickness is approximately 13 times the Kolmogorov length scale for large$Re_{bI}$($Re_{bI}\gtrsim 30$), consistent with non-stratified flows, whereas it is almost equal to the vertical length scale of the stratified flow,$l_{vI}=l_{hI}Re^{-1/2}$(here$l_{hI}$is the horizontal length scale near the TNTI layer, and$Re$is the Reynolds number), in the low-$Re_{bI}$regime ($Re_{bI}\lesssim 2$). Turbulent fluid is vertically transported towards the TNTI layer when$Re_{bI}$is large, sustaining the thin TNTI layer with large buoyancy frequency and mean shear. This sharpening effect is weakened as$Re_{bI}$decreases and eventually becomes negligible for very low$Re_{bI}$. Overturning motions occur near the TNTI layer for large$Re_{bI}$. The dependence on buoyancy Reynolds number is related to the value of$Re_{bI}$near the TNTI layer, which is smaller than the value deep inside the turbulent core region. An imprint of the internal gravity waves propagating in the non-turbulent region is found for vorticity within the TNTI layer, inferring an interaction between turbulence and internal gravity waves. The wave energy flux causes a net loss of the kinetic energy in the turbulent core region bounded to the TNTI layer, and the amount of kinetic energy extracted from the turbulent region by internal gravity waves is comparable to the amount dissipated in the turbulent region.
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Bi, Cuicui, Chun Qing, Pengfei Wu, Xiaomei Jin, Qing Liu, Xianmei Qian, Wenyue Zhu, and Ningquan Weng. "Optical Turbulence Profile in Marine Environment with Artificial Neural Network Model." Remote Sensing 14, no. 9 (May 8, 2022): 2267. http://dx.doi.org/10.3390/rs14092267.
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Optical turbulence strongly affects different types of optoelectronic and adaptive optics systems. Systematic direct measurements of optical turbulence profiles [Cn2(h)] are lacking for many climates and seasons, particularly in marine environments, because it is impractical and expensive to deploy instrumentation. Here, a backpropagation neural network optimized using a genetic algorithm (GA-BP) is developed to estimate atmospheric turbulence profiles in marine environments which is validated against corresponding [Cn2(h)] profile datasets from a field campaign of balloon-borne microthermal measurements at the Haikou marine environment site. Overall, the trend and magnitude of the GA-BP model and measurements agree. The [Cn2(h)] profiles from the GA-BP model are generally superior to those obtained by BP and the physically-based (HMNSP99) models. Several statistical operators were used to quantify the GA-BP model performance on reconstructing the optical turbulence profiles in marine environments. The characterization of vertical distributions of optical turbulence profiles and the main integral parameters derived from [Cn2(h)] profiles are presented. The median Fried parameter, isoplanatic angle, and coherence time are 9.94 cm, 0.69″, and 2.85 ms, respectively, providing independent optical turbulence parameters for adaptive optics systems. The proposed approach exhibits potential for implementation in ground-based optical applications in marine environments.
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Li, Wangxu, Zhenggui Li, Ziyue Wang, Feng Wu, Lianchen Xu, and Shengyang Peng. "Turbulence Intensity Characteristics of a Magnetoliquid Seal Interface in a Liquid Environment." Coatings 11, no. 11 (October 30, 2021): 1333. http://dx.doi.org/10.3390/coatings11111333.
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In a liquid environment, the turbulence intensity of the interfacial layer between the magnetic and sealing medium fluids in magnetic liquid seals directly affects the layer stability. Reducing the maximum turbulence intensity of the fluid interface layer effectively improves the stability of the magnetic fluid rotary seal. In this study, we simulated magnetic fluid sealing devices with different structures in liquid environments using the FLUENT software. The simulation results were verified through experimental analyses of the turbulence intensity at the sealing interface. The maximum turbulence intensity of the liquid interface layer increased with increasing shaft speed. At the same speed, the turbulence intensity was maximized at the shaft interface before gradually decreasing in a multistage linear pattern along the radial direction. A magnetic liquid seal with an optimized structure (OS) in the liquid environment was designed based on these results. The maximum turbulence intensity of the liquid interface layer in the OS was independent of the rotation speed and was more than 20% lower than that that in the traditional structure. These results provide a reference for designing magnetic liquid sealing devices.
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Borque, Paloma, Edward P. Luke, Pavlos Kollias, and Fan Yang. "Relationship between Turbulence and Drizzle in Continental and Marine Low Stratiform Clouds." Journal of the Atmospheric Sciences 75, no. 12 (November 9, 2018): 4139–48. http://dx.doi.org/10.1175/jas-d-18-0060.1.
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Abstract Turbulence and drizzle-rate measurements from a large dataset of marine and continental low stratiform clouds are presented. Turbulence peaks at cloud base over land and near cloud top over the ocean. For both regions, eddy dissipation rate values of 10−5–10−2 m2 s−3 are observed. Surface-based measurements of cloud condensation nuclei number concentration NCCN and liquid water path (LWP) are used to estimate the precipitation susceptibility S0. Results show that positive S0 values are found at low turbulence, consistent with the principle that aerosols suppress precipitation formation, whereas S0 is smaller, and can be negative, in a more turbulent environment. Under similar macrophysical conditions, especially for medium to high LWP, high (low) turbulence is likely to lessen (promote) the suppression effect of high NCCN on precipitation. Overall, the turbulent effect on S0 is stronger in continental than marine stratiform clouds. These observational findings are consistent with recent analytical prediction for a turbulence-broadening effect on cloud droplet size distribution.
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Stamenkovic, Zivojin, Milos Kocic, and Jelena Petrovic. "The CFD modeling of two-dimensional turbulent MHD channel flow." Thermal Science 21, suppl. 3 (2017): 837–50. http://dx.doi.org/10.2298/tsci160822093s.
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In this paper, influence of magnetic field on turbulence characteristics of twodimensional flow is investigated. The present study has been undertaken to understand the effects of a magnetic field on mean velocities and turbulence parameters in turbulent 2-D channel flow. Several cases are considered. First laminar flow in a channel and MHD laminar channel flow are analyzed in order to validate model of magnetic field influence on electrically conducting fluid flow. Main part of the paper is focused on MHD turbulence suppression for 2-D turbulent flow in a channel and around the flat plate. The simulations are performed using ANSYS CFX software. Simulations results are obtained with BSL Reynolds stress model for turbulent and MHD turbulent flow around flat plate. The nature of the flow has been examined through distribution of mean velocities, turbulent fluctuations, vorticity, Reynolds stresses and turbulent kinetic energy.
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Slavec Gomezel, Alenka, and Darija Aleksić. "THE RELATIONSHIPS BETWEEN TECHNOLOGICAL TURBULENCE, FLOW EXPERIENCE, INNOVATION PERFORMANCE AND SMALL FIRM GROWTH." Journal of Business Economics and Management 21, no. 3 (April 24, 2020): 760–82. http://dx.doi.org/10.3846/jbem.2020.12280.
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The main objective of the paper is to address the question of how to foster innovation and small firm growth under different levels of technological turbulence. Specifically, the paper examines the relationship among risk-taking, arising from different levels of technological turbulence, flow experience, innovation and small firm growth (i.e. market share and ROI growth). The underlying premise of our research is that there are substantial differences in low and high technological environments in terms of the relationships of risk taking, flow at work, innovation and small firm growth. Based on a survey among 188 entrepreneurs, the paper tests the proposed relationships in technological diverse environments with structural equation modelling. The results show that, when the level of technological turbulence is high, flow experience is significantly related to innovation and small firm growth, while in low-technological turbulence environment such relationships are not present. The study contributes to the entrepreneurial literature by demonstrating that in highly turbulent environments, flow experience may promote entrepreneurs’ innovation and the efficiency of small firm performance. The study also provides new empirical insights about the relationship between entrepreneurs’ behaviour, which is influenced by environmental conditions, on the one hand and innovation and small firm growth on the other hand.
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Mclarney, Carolan. "Strategic Planning Processes in Chaotic Environments: How to Calm a Turbulent Sea?" Vikalpa: The Journal for Decision Makers 28, no. 1 (January 2003): 27–46. http://dx.doi.org/10.1177/0256090920030103.
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This study explored the linkages between environmental turbulence, strategic planning, and process effectiveness. Going beyond the traditional literature on the planning process, the present research included both an examination of the planning process itself and the external environment in which the organization of interest exists. The objective of this research was to examine the multi-dimensional treatments of environmental turbulence, strategic planning processes, and process effectiveness. It proposed to explore the planning-process effectiveness construct across two industries. By adding the aspect of environmental turbulence into the equation, the multi-dimensional treatments of planning and process effectiveness were broadened. This study examined the linkage between the external environment, the strategic planning process, and effectiveness of the process. It addressed two research questions: What components and contextual elements of the planning process are critical for that process to be effective? Are these components and contextual elements of the planning process different in various levels of environmental turbulence? The research model demonstrated that in different levels of environmental turbulence, the components and contextual elements of the strategic planning process would be stressed differently. Specifically, in more turbulent environments, the organization's strategic planning process would devote more resources to the planning function, be less resistant to planning, pay more attention to external and internal facets, employ more planning techniques, and encourage greater functional coverage and integration. All these were relative to another organization's planning process that was operating in a less turbulent environment. One of the aims of this research study was to develop concrete recommendations to the automotive and beverage industries. Based on the findings of the study, it was recommended that: The strategic planning managers in the beverage industry pay special attention to ensure that there is sufficient functional coverage in their strategic planning process. Sufficient resources be made available to the planning function. Also, the level of resistance to planning be monitored by which resistance should be an on-going process throughout the strategic planning process and in every functional area of the firm. The other aim of this research study was to explore the "black box" of strategic planning. The findings revealed that: Functional coverage was the key component in the process and that the adequate supply of resources to the planning function was the most critical contextual element for the effectiveness of the planning process. Organizations with highly turbulent environments tended to need more resources placed against the planning function and required extensive attention to the external facets of planning for their strategic planning process to be effective. At the same time, firms in lower turbulence industries such as paints and coatings, railroads, and forge casting could look to the beverage industry for a concrete action plan to improve the effectiveness of their planning processes.
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Trier, Stanley B., Robert D. Sharman, Domingo Muñoz-Esparza, and Todd P. Lane. "Environment and Mechanisms of Severe Turbulence in a Midlatitude Cyclone." Journal of the Atmospheric Sciences 77, no. 11 (November 2020): 3869–89. http://dx.doi.org/10.1175/jas-d-20-0095.1.
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AbstractA large midlatitude cyclone occurred over the central United States from 0000 to 1800 UTC 30 April 2017. During this period, there were more than 1100 reports of moderate-or-greater turbulence at commercial aviation cruising altitudes east of the Rocky Mountains. Much of this turbulence was located above or, otherwise, outside the synoptic-scale cloud shield of the cyclone, thus complicating its avoidance. In this study we use two-way nesting in a numerical model with finest horizontal spacing of 370 m to investigate possible mechanisms producing turbulence in two distinct regions of the cyclone. In both regions, model-parameterized turbulence kinetic energy compares well to observed turbulence reports. Despite being outside of hazardous large radar reflectivity locations in deep convection, both regions experienced strong modification of the turbulence environment as a result of upper-tropospheric/lower-stratospheric (UTLS) convective outflow. For one region, where turbulence was isolated and short lived, simulations revealed breaking of ~100-km horizontal-wavelength lower-stratospheric gravity waves in the exit region of a UTLS jet streak as the most likely mechanism for the observed turbulence. Although similar waves occurred in a simulation without convection, the altitude at which wave breaking occurred in the control simulation was strongly affected by UTLS outflow from distant deep convection. In the other analyzed region, turbulence was more persistent and widespread. There, overturning waves of much shorter 5–10-km horizontal wavelengths occurred within layers of gradient Richardson number < 0.25, which promoted Kelvin–Helmholtz instability associated with strong vertical shear in different horizontal locations both above and beneath the convectively enhanced UTLS jet.
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Xu, Manman, Liangping Zhou, Shiyong Shao, Ningquan Weng, and Qing Liu. "Analyzing the Effects of a Basin on Atmospheric Environment Relevant to Optical Turbulence." Photonics 9, no. 4 (April 2, 2022): 235. http://dx.doi.org/10.3390/photonics9040235.
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The performance of adaptive optics (AO) systems are highly dependent upon optical turbulence. Thus, it is necessary to have the appropriate knowledge of the spatiotemporal characteristics of optical turbulence strength. In this paper, the spatiotemporal distribution of meteorological parameters (wind and temperature) and optical turbulence parameters (turbulence strength, temperature gradient, and wind shear) derived from pulsed coherent Doppler lidar, a microwave radiometer, and ERA5 reanalysis data are investigated, and the results show that the meteorological parameters in a basin develop independently, while the external influence will increase above the basin. By fitting radiosonde data, an existing parameterized model was improved to be more in line with the evolutionary properties of local optical turbulence. The development of temperature gradient and wind shear is influenced by the basin, which ultimately leads to an optical turbulence vertical profile that is discrepant at different altitude layers. The results indicate that temperature gradient plays a dominant role in turbulence generation below 2 km, and wind shear increases its impact significantly above 2 km. Furthermore, the optical turbulence parameters (outer scale, turbulence diffusion coefficient, and turbulence energy dissipation rate) and optical turbulence strength have good consistency, which might be derived from the combined effect of terrain and complex environment. Finally, the integrated parameters for astronomy and optical telecommunication were derived from optical turbulence strength profiles. An appropriate knowledge of optical turbulence is essential for improving the performance of adaptive optics systems and astronomical site selection.
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Zhang, Haiping, Yafei Cui, Yuehong Zhang, Hanling Xu, and Feipeng Li. "Experimental Study of the Quantitative Impact of Flow Turbulence on Algal Growth." Water 13, no. 5 (February 28, 2021): 659. http://dx.doi.org/10.3390/w13050659.
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Flow turbulence has been widely accepted as one of the essential factors affecting phytoplankton growth. In this study, laboratory cultures of Microcystis aeruginosa in beakers were carried out under different turbulent conditions to identify the quantitative relationship between the algal growth rate and the turbulent intensity. The turbulent intensity (represented by energy dissipation rate, ε) was simulated with the software FLUENT. Daily measurement of the two parameters (algal biomass and chlorophyll-a concentration) was carried out during the experimental period to represent the algal growth rate. Meanwhile, the rates of photosynthetic oxygen evolution and chlorophyll fluorescence intensity were calculated to investigate the photosynthetic efficiency. The results indicated that the growth rate of Microcystis aeruginosa became higher in the turbulent environment than in the still water environment under the designed experimental conditions. The peak growth rate of Microcystis aeruginosa occurred when ε was 6.44 × 10−2 m2/s3, over which the rate declined, probably due to unfavorable impacts of strong turbulence. In comparison, the maximum rate of photosynthetic oxygen evolution occurred when ε was 0.19 m2/s3. Based on the findings of this study, an exponential function was proposed in order to incorporate the effect of flow turbulence into the existing algal growth models, which usually just consider the impacts of nutrient availability, illumination, and temperature.
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Sjeric, Momir, Darko Kozarac, and Rudolf Tomic. "Development of a two zone turbulence model and its application to the cycle-simulation." Thermal Science 18, no. 1 (2014): 1–16. http://dx.doi.org/10.2298/tsci130103030s.
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The development of a two zone k-? turbulence model for the cycle-simulation software is presented. The in-cylinder turbulent flow field of internal combustion engines plays the most important role in the combustion process. Turbulence has a strong influence on the combustion process because the convective deformation of the flame front as well as the additional transfer of the momentum, heat and mass can occur. The development and use of numerical simulation models are prompted by the high experimental costs, lack of measurement equipment and increase in computer power. In the cycle-simulation codes, multi zone models are often used for rapid and robust evaluation of key engine parameters. The extension of the single zone turbulence model to the two zone model is presented and described. Turbulence analysis was focused only on the high pressure cycle according to the assumption of the homogeneous and isotropic turbulent flow field. Specific modifications of differential equation derivatives were made in both cases (single and two zone). Validation was performed on two engine geometries for different engine speeds and loads. Results of the cyclesimulation model for the turbulent kinetic energy and the combustion progress variable are compared with the results of 3D-CFD simulations. Very good agreement between the turbulent kinetic energy during the high pressure cycle and the combustion progress variable was obtained. The two zone k-? turbulence model showed a further progress in terms of prediction of the combustion process by using only the turbulent quantities of the unburned zone.
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Bervida, Marija, Samo Stanič, Griša Močnik, Longlong Wang, Klemen Bergant, and Xiaoquan Song. "Bora Flow Characteristics in a Complex Valley Environment." Remote Sensing 13, no. 21 (October 29, 2021): 4363. http://dx.doi.org/10.3390/rs13214363.
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This paper complements the existing studies of Bora flow properties in the Vipava valley with the study of Bora turbulence in a lower region of the troposphere. The turbulence characteristics of Bora flow were derived from high resolution Doppler wind lidar measurements during eight Bora wind episodes that occurred in November and December 2019. Based on the vertical profiles of wind velocity, from 80 to 180 m above the valley floor, the turbulence intensity related to all three spatial directions and the along-wind integral length scales related to three velocity components were evaluated and compared to the approximations given in international standards. The resulting turbulence characteristics of Bora flow in a deep mountain valley exhibited interesting behaviour, differing from the one expected and suggested by standards. The intensity of turbulence during Bora episodes was found to be quite strong, especially regarding the expected values for that particular category of terrain. The specific relationship between along-wind, lateral and vertical intensity was evaluated as well. The scales of turbulence in the along-wind direction were found to vary widely between different Bora episodes and were rather different from the approximations given by standards, with the most significant deviations observed for the along-wind length scale of the vertical velocity component. Finally, the periodicity of flow structures above the valley was assessed, yielding a wide range of possible periods between 1 and 10 min, thus confirming some of the previous observations from the studies of Bora in the Vipava valley.
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Tang, Yongli, Matthias Thürer, Xinyue Hu, Haiwen Zhang, and Claudio Petti. "Institution Driven Innovation under Industrial Environment Turbulence." Academy of Management Proceedings 2017, no. 1 (August 2017): 10870. http://dx.doi.org/10.5465/ambpp.2017.10870abstract.
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Arslan, Kamil. "Three-dimensional numerical investigation of turbulent flow and heat transfer inside a horizontal semi-circular cross-sectioned duct." Thermal Science 18, no. 4 (2014): 1145–58. http://dx.doi.org/10.2298/tsci110724065a.
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In this study, steady-state turbulent forced flow and heat transfer in a horizontal smooth semi-circular cross-sectioned duct was numerically investigated. The study was carried out in the turbulent flow condition where Reynolds numbers range from 1?104 to 5.5?104. Flow is hydrodynamically and thermally developing (simultaneously developing flow) under uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition on the duct?s wall. A commercial CFD program, Ansys Fluent 12.1, with different turbulent models was used to carry out the numerical study. Different suitable turbulence models for fully turbulent flow (k-? Standard, k-? Realizable, k-? RNG, k-? Standard and k-? SST) were used in this study. The results have shown that as the Reynolds number increases Nusselt number increases but Darcy friction factor decreases. Based on the present numerical solutions, new engineering correlations were presented for the average Nusselt number and average Darcy friction factor. The numerical results for different turbulence models were compared with each other and similar experimental investigations carried out in the literature. It is obtained that, k-? Standard, k-? Realizable and k-? RNG turbulence models are the most suitable turbulence models for this investigation. Isovel contours of velocity magnitude and temperature distribution for different Reynolds numbers, turbulence models and axial stations in the duct were presented graphically. Also, local heat transfer coefficient and local Darcy friction factor as function of dimensionless position along the duct were obtained in this investigation.
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Bencherif, Mohamed, Mohand Tazerout, and Abdelkrim Liazid. "Turbulence-combustion interaction in direct injection diesel engine." Thermal Science 18, no. 1 (2014): 17–27. http://dx.doi.org/10.2298/tsci121210084b.
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The experimental measures of chemical species and turbulence intensity during the closed part of the engine combustion cycle are today unattainable exactly. This paper deals with numerical investigations of an experimental direct injection Diesel engine and a commercial turbocharged heavy duty direct injection one. Simulations are carried out with the kiva3v2 code using the RNG (k-?) model. A reduced mechanism for n-heptane was adopted for predicting auto-ignition and combustion processes. From the calibrated code based on experimental in-cylinder pressures, the study focuses on the turbulence parameters and combustion species evolution in the attempt to improve understanding of turbulence-chemistry interaction during the engine cycle. The turbulent kinetic energy and its dissipation rate are taken as representative parameters of turbulence. The results indicate that chemistry reactions of fuel oxidation during the auto-ignition delay improve the turbulence levels. The peak position of turbulent kinetic energy coincides systematically with the auto-ignition timing. This position seems to be governed by the viscous effects generated by the high pressure level reached at the auto-ignition timing. The hot regime flame decreases rapidly the turbulence intensity successively by the viscous effects during the fast premixed combustion and heat transfer during other periods. It is showed that instable species such as CO are due to deficiency of local mixture preparation during the strong decrease of turbulence energy. Also, an attempt to build an innovative relationship between self-ignition and maximum turbulence level is proposed. This work justifies the suggestion to determine otherwise the self-ignition timing.
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Jovanovic, Jovan, Bettina Frohnapfel, Mira Pashtrapanska, and Franz Durst. "The effect of polymers on the dynamics of turbulence in a drag reduced flow." Thermal Science 9, no. 1 (2005): 13–41. http://dx.doi.org/10.2298/tsci0501013j.
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An experimental investigation of a polymer drag reduced flow using state-of-the-art laser-Doppler anemometry in a refractive index-matched pipe flow facility is reported. The measured turbulent stresses deep in the viscous sublayer are analyzed using the tools of invariant theory. It is shown that with higher polymer concentration the anisotropy of the Reynolds stresses increases. This trend is consistent with the trends extracted from DNS data of non-Newtonian fluids yielding different amounts of drag reduction. The interaction between polymer and turbulence is studied by considering local stretching of the molecular structure of a polymer by small-scale turbulent motions in the region very close to the wall. The stretching process is assumed to re-structure turbulence at small scales by forcing these to satisfy local axisymmetry with invariance under rotation about the axis aligned with the main flow. It is shown analytically that kinematic constraints imposed by local axisymmetry farce turbulence near the wall to tend towards the one-component state and when turbulence reaches this limiting state it must be entirely suppressed across the viscous sublayer. Based on this consideration it is suggested that turbulent drag reduction by high polymers resembles the reverse transition process from turbulent to laminar. Theoretical considerations based on the elastic behavior of a polymer and spatial intermittency of turbulence at small scales enabled quantitative estimates to be made for the relaxation time of a polymer and its concentration that ensure maximum drag reduction in turbulent pipe flows, and it is shown that predictions based on these are in very good agreement with available experimental data.
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Sreenivasan, K. R., and C. Meneveau. "The fractal facets of turbulence." Journal of Fluid Mechanics 173 (December 1986): 357–86. http://dx.doi.org/10.1017/s0022112086001209.
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Speculations abound that several facets of fully developed turbulent flows are fractals. Although the earlier leading work of Mandelbrot (1974, 1975) suggests that these speculations, initiated largely by himself, are plausible, no effort has yet been made to put them on firmer ground by, resorting to actual measurements in turbulent shear flows. This work is an attempt at filling this gap. In particular, we examine the following questions: (a) Is the turbulent/non-turbulent interface a self-similar fractal, and (if so) what is its fractal dimension ? Does this quantity differ from one class of flows to another? (b) Are constant-property surfaces (such as the iso-velocity and iso-concentration surfaces) in fully developed flows fractals? What are their fractal dimensions? (c) Do dissipative structures in fully developed turbulence form a fractal set? What is the fractal dimension of this set? Answers to these questions (and others to be less fully discussed here) are interesting because they bring the theory of fractals closer to application to turbulence and shed new light on some classical problems in turbulence - for example, the growth of material lines in a turbulent environment. The other feature of this work is that it tries to quantify the seemingly complicated geometric aspects of turbulent flows, a feature that has not received its proper share of attention. The overwhelming conclusion of this work is that several aspects of turbulence can be described roughly by fractals, and that their fractal dimensions can be measured. However, it is not clear how (or whether), given the dimensions for several of its facets, one can solve (up to a useful accuracy) the inverse problem of reconstructing the original set (that is, the turbulent flow itself).
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Vázquez-Semadeni, Enrique. "Theory of Feedback in Clusters and Molecular Cloud Turbulence." Proceedings of the International Astronomical Union 6, S270 (May 2010): 275–82. http://dx.doi.org/10.1017/s1743921311000500.
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AbstractI review recent numerical and analytical work on the feedback from both low- and high-mass cluster stars into their gaseous environment. The main conclusions are that i) outflow driving appears capable of maintaing the turbulence in parsec-sized clumps and retarding their collapse from the free-fall rate, although there exist regions within molecular clouds, and even some examples of whole clouds, which are not actively forming stars, yet are just as turbulent, so that a more universal turbulence-driving mechanism is needed; ii) outflow-driven turbulence exhibits specific spectral features that can be tested observationally; iii) feedback plays an important role in reducing the SFR; iv) nevertheless, numerical simulations suggest feedback cannot completely prevent a net contracting motion of clouds and clumps. Therefore, an appealing source for driving the turbulence everywhere in GMCs is the accretion from the environment, at all scales. In this case, feedback's most important role may be to prevent a fraction of the gas nearest to newly formed stars from actually reaching them, thus reducing the SFE.
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Wall, Dylan, and Eric Paterson. "Anisotropic RANS Turbulence Modeling for Wakes in an Active Ocean Environment." Fluids 5, no. 4 (December 18, 2020): 248. http://dx.doi.org/10.3390/fluids5040248.
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The problem of simulating wakes in a stratified oceanic environment with active background turbulence is considered. Anisotropic RANS turbulence models are tested against laboratory and eddy-resolving models of the problem. An important aspect of our work is to acknowledge that the environment is not quiescent; therefore, additional sources are included in the models to provide a non-zero background turbulence. The RANS models are found to reproduce some key features from the eddy-resolving and laboratory descriptions of the problem. Tests using the freestream sources show the intuitive result that background turbulence causes more rapid wake growth and decay.
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Chen, Sisi, Man-Kong Yau, Peter Bartello, and Lulin Xue. "Bridging the condensation–collision size gap: a direct numerical simulation of continuous droplet growth in turbulent clouds." Atmospheric Chemistry and Physics 18, no. 10 (May 25, 2018): 7251–62. http://dx.doi.org/10.5194/acp-18-7251-2018.
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Abstract. In most previous direct numerical simulation (DNS) studies on droplet growth in turbulence, condensational growth and collisional growth were treated separately. Studies in recent decades have postulated that small-scale turbulence may accelerate droplet collisions when droplets are still small when condensational growth is effective. This implies that both processes should be considered simultaneously to unveil the full history of droplet growth and rain formation. This paper introduces the first direct numerical simulation approach to explicitly study the continuous droplet growth by condensation and collisions inside an adiabatic ascending cloud parcel. Results from the condensation-only, collision-only, and condensation–collision experiments are compared to examine the contribution to the broadening of droplet size distribution (DSD) by the individual process and by the combined processes. Simulations of different turbulent intensities are conducted to investigate the impact of turbulence on each process and on the condensation-induced collisions. The results show that the condensational process promotes the collisions in a turbulent environment and reduces the collisions when in still air, indicating a positive impact of condensation on turbulent collisions. This work suggests the necessity of including both processes simultaneously when studying droplet–turbulence interaction to quantify the turbulence effect on the evolution of cloud droplet spectrum and rain formation.
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MASON, ROGER B. "COPING WITH COMPLEXITY AND TURBULENCE - AN ENTREPRENEURIAL SOLUTION." Journal of Enterprising Culture 14, no. 04 (December 2006): 241–66. http://dx.doi.org/10.1142/s0218495806000155.
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This paper considers the adoption of an entrepreneurial orientation as a paradigm for companies operating in a complex and turbulent environment, viewing the environment as a complex and turbulent system in terms of chaos theory. Approaches suggested by chaos theory are compared with the entrepreneurial orientation to identify if such an orientation matches these suggested approaches. Literature on chaos theory and entrepreneurship is compared, and a short case is presented, providing an illustration of how a company operating successfully in a complex and turbulent environment has used the principles of an entrepreneurial orientation. The paper identifies considerable similarity between the management approaches suggested by chaos theory and the principles of the entrepreneurial orientation, indicating that chaos theory may provide the theoretical underpinning of the relationship between entrepreneurial orientation and turbulent environments. The case also shows how an entrepreneurial orientation has been successfully used in a complex and turbulent environment. The conclusion is that companies operating in a complex and turbulent environment could benefit from adopting an entrepreneurial orientation.
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Liang, Jiening, Qi Guo, Zhida Zhang, Min Zhang, Pengfei Tian, and Lei Zhang. "Influence of Complex Terrain on Near-Surface Turbulence Structures over Loess Plateau." Atmosphere 11, no. 9 (August 30, 2020): 930. http://dx.doi.org/10.3390/atmos11090930.
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To study the influence of complex terrain with different scales on the structure of near-surface turbulence, the turbulence observational data from Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) were analyzed. SACOL is located in typical Loess Plateau topography. The terrain around the site varies greatly with the direction. Representative data from the Northeast, Southeast, Southwest, and Northwest were selected to study the structure characteristics of the near surface turbulence. The complex topography within the flux footprint enhances the vertical scale of turbulence σw and thereby increases the vertical–longitudinal ratio of turbulence Ar. While the turbulent horizontal scale σu is also significantly affected by the distant terrain beyond the flux footprint. The upwind terrain undulation increases σu and reduces Ar. Affected by the complex terrain, the ratio of the spectrum of the vertical velocity to that of the longitudinal velocity, Sw(n)/Su(n), is far less than 4/3 in the southwest direction, and the turbulence is significantly anisotropic.
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Frehlich, Rod, Yannick Meillier, and Michael L. Jensen. "Measurements of Boundary Layer Profiles with In Situ Sensors and Doppler Lidar." Journal of Atmospheric and Oceanic Technology 25, no. 8 (August 1, 2008): 1328–40. http://dx.doi.org/10.1175/2007jtecha963.1.
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Abstract A new in situ measurement system and lidar processing algorithms were developed for improved measurements of boundary layer profiles. The first comparisons of simultaneous Doppler lidar–derived profiles of the key turbulence statistics of the two orthogonal horizontal velocity components (longitudinal and transverse) are presented. The instrument requirements for accurate observations of stably stratified turbulence were determined. A region of stably stratified low turbulence with constant gradients of temperature and velocity was observed above the nocturnal boundary layer using high-rate sensors. The important turbulence parameters were estimated, and turbulence spectra were consistent with new theoretical descriptions of stratified turbulence. The impact of removing the larger-scale velocity features in Doppler lidar estimates of turbulent velocity variance and length scales was investigated. The Doppler lidar–derived estimates of energy dissipation rate ε were found to be insensitive to spatial filtering of the large-scale atmospheric processes. The in situ and lidar-derived profiles were compared for the stable boundary layer in a suburban environment.
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Samsonov, Vladimir. "Ventilation currents in the turbulent environment of industrial premises." Construction and Architecture 10, no. 1 (March 20, 2022): 26–30. http://dx.doi.org/10.29039/2308-0191-2021-10-1-26-30.
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The turbulent air environment in industrial premises intensively affects the characteristics of air and heat and gas jets and thereby the effectiveness of various industrial ventilation devices. This effect manifests itself in the accelerated expansion of the main sections of the jets and in the reduction of their range of action. Until recently, the influence of the intensity of air turbulence was not taken into account in the corresponding calculation and design methods. The article proposes methods for calculating air jets and the efficiency of open local suction, taking into account the influence of a turbulized air environment.
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SCHWEITZER, FIONA M., OLIVER GASSMANN, and KURT GAUBINGER. "OPEN INNOVATION AND ITS EFFECTIVENESS TO EMBRACE TURBULENT ENVIRONMENTS." International Journal of Innovation Management 15, no. 06 (December 2011): 1191–207. http://dx.doi.org/10.1142/s1363919611003702.
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The paper focuses on the challenges of integrating external sources in the innovation process and investigates the role of environmental turbulence in this context. Building on the resources-based view and the dynamic capabilities perspective the authors propose that open innovation strategies assist companies in navigating through turbulent times. Empirical testing of this assumption in a sample of 101 manufacturing firms indicates that open innovation activities are more important in turbulent than in non-turbulent markets and that supplier integration is vital when technological turbulence is high, whilst customer integration is critical in environments characterized by high market turbulence. From a practical point of view, these findings highlight the importance of stakeholder integration in the innovation process and provide details on the successful implementation of this strategy under different environmental settings.
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Murray, Craig WA, and David Anderson. "A CFD-based procedure for airspace integration of small unmanned aircraft within congested areas." International Journal of Micro Air Vehicles 9, no. 4 (April 5, 2017): 235–52. http://dx.doi.org/10.1177/1756829316669957.
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Future integration of small unmanned aircraft within an urban airspace requires an a posteriori understanding of the building-induced aerodynamics which could negatively impact on vehicle performance. Moving away from generalised building formations, we model the centre of the city of Glasgow using Star-CCM+, a commercial CFD package. After establishing a critical turbulent kinetic energy for our vehicle, we analyse the CFD results to determine how best to operate a small unmanned aircraft within this environment. As discovered in a previous study, the spatial distribution of turbulence increases with altitude. It was recommended then that UAVs operate at the minimal allowable altitude within a congested area. As the flow characteristics in an environment are similar, regardless of inlet velocity, we can determine areas within a city which will have consistently low or high values of turbulent kinetic energy. As the distribution of turbulence is dependent on prevailing wind directions, some directions are more favourable than others, even if the wind speed is unchanging. Moving forward we should aim to gather more information about integrated aircraft and how they respond to turbulence in a congested area.
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AUGUSTINE, SHIVAN M., and NAVEN CHETTY. "EXPERIMENTAL VERIFICATION OF THE TURBULENT EFFECTS ON LASER BEAM PROPAGATION IN SPACE." Atmósfera 27, no. 4 (January 13, 2015): 385–401. http://dx.doi.org/10.20937/atm.2014.27.04.05.
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In this work, we have modified an existing experimental setup to fully classify the thermal effects on a laser beam propagating in air. Improvements made to the setup include a new, more powerful laser, a precision designed turbulence delivery system, an imbedded pressure sensor, and a platform for height adjustability between the laser beam and the turbulence model. The setup was not only able to reproduce previous results exactly but also allowed new data for the turbulence strength C2n, the Rytov variance (scintillation) and the coherence diameter (Fried’s parameter) to be successfully measured. Analysis of the produced interferograms has been discussed using fast Fourier transforms. The results confirm, within the Kolmogorov regime, that phase and intensity fluctuations increase relative to temperature. The turbulent region exhibited very strong disturbances, in the range of 1.1 × 10–12 m–2/3 to 2.7 × 10–12 m–2/3. In spite of the strong turbulence strength, scintillation proved otherwise, since the condition for a weak turbulence environment was determined in the laboratory and a low scintillation index was to be expected. This is as a result of the relatively short propagation distances achieved in the laboratory. In the open atmosphere, path lengths extend over vast distances and in order for turbulent effects to be realized, the turbulence model must generate stronger turbulence. The model was, therefore, able to demonstrate its ability to fully quantify and determine the thermal turbulence effects on a propagating laser beam.
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de Gouveia Dal Pino, E. M., R. Santos-Lima, G. Kowal, and D. Falceta-Gonçalves. "Turbulence and dynamo interlinks." Proceedings of the International Astronomical Union 8, S294 (August 2012): 337–48. http://dx.doi.org/10.1017/s174392131300272x.
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AbstractThe role of turbulence in astrophysical environments and its interplay with magnetic fields is still highly debated. In this lecture, we will discuss this issue in the framework of dynamo processes. We will first present a very brief summary of turbulent dynamo theories, then will focus on small scale turbulent dynamos and their particular relevance on the origin and maintenance of magnetic fields in the intra-cluster media (ICM) of galaxies. In these environments, the very low density of the flow requires a collisionless-MHD treatment. We will show the implications of this approach in the turbulent amplification of the magnetic fields in these environments. To finalize, we will also briefly address the connection between MHD turbulence and fast magnetic reconnection and its possible implications in the diffusion of magnetic flux in the dynamo process.
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Liu, Rui-Xi, and Lei Ma. "Effects of ocean turbulence on photon orbital angular momentum quantum communication." Acta Physica Sinica 71, no. 1 (2022): 010304. http://dx.doi.org/10.7498/aps.71.20211146.
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The effect of the turbulent motion of ocean on the quantum communication based on the orbital angular momentum in an underwater quantum channel is studied in this work. Based on the power spectrum model of ocean turbulence proposed by Elamassie, the quantitative relationships of different ocean turbulence parameters with the single photon detection probability of orbital angular momentum photons, the channel capacity, the key generation rate, the concurrence of two entangled photons are proposed. The maximum entanglement distance of the orbital angular momentum entangled photon-pairs in the ocean turbulence is further studied by the universal entanglement decay of the concurrence of entangled photon-pairs in the ocean turbulence. The results show that the detection probability of single photon, the channel capacity, the key generation rate, and the concurrence of entangled photon-pairs decrease with the increase of the dissipation rate of turbulent kinetic energy and the decrease of the rate of dissipation of mean-squared temperature. The influence of the temperature and salinity balance parameter of ocean turbulence on the performance of underwater quantum communication are significantly different under the condition of whether the stable stratification of seawater is assumed or not. In the ocean turbulent environment, the increasing of the initial orbital angular momentum quantum number of signal photons can improve the key generation rate of quantum key distribution and the resistance of entangled photons to entanglement decay.
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Rivera-Rodríguez, Hugo-Alberto, Teresa Garcia-Merino, and Valle Santos-Alvarez. "How to Thrive in Turbulent Business Environments: Case Colombia’s Mobile Telephony Industry." Mediterranean Journal of Social Sciences 8, no. 3 (May 24, 2017): 133–41. http://dx.doi.org/10.5901/mjss.2017.v8n3p133.
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Abstract Coevolution originated as a biological concept has traditionally been associated with the biological sciences to describe those cases of mutual evolutionary influence involving two (or more) species. This concept is fairly new in the study of organizations as it was introduced only two decades ago, specifically refers to a process involving successive changes between businesses and the environment. More recentrly, researchers began to employ the coevolution as an alternative to overcome the business turbulence with great success that would otherwise put its existence at risk. This article delimits the organizational coevolution concept making a direct association with business turbulence. It is being presented in the form of a multiple-case study of the mobile telephony industry in Colombia with a qualitative methodology. As part of the information-gathering process, approximately 300 public and private documents were consulted and 50 interviews with key stakeholders of the industry were conducted. Content analysis is the main data analysis technique, and the ATLAS/ti is used for processing. Thus, the final results show that when a sector faces turbulence, businesses can efficiently manage this phenomenon if they undertake a structural coupling process between the turbulent environment and strategic behaviour.
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Liu, Yonglei, Xianlong Liu, Lin Liu, Fei Wang, Yuping Zhang, and Yangjian Cai. "Ghost Imaging with a Partially Coherent Beam Carrying Twist Phase in a Turbulent Ocean: A Numerical Approach." Applied Sciences 9, no. 15 (July 26, 2019): 3023. http://dx.doi.org/10.3390/app9153023.
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Ghost imaging (GI) is an indirect imaging approach that can retrieve an object’s image even in a harsh environment through measuring the fourth-order correlation function (FOCF) between the signal and idle optical paths. In this paper, we study lensless GI with a partially coherent beam carrying twist phase, i.e., twisted Gaussian Schell-model (TGSM) beam, in the presence of oceanic turbulence. Explicit expression of the FOCF is derived based on the optical coherence theory and Rytov approximation, and the effects of the twist phase and the oceanic turbulence on the quality and visibility of image are investigated in detail through numerical examples. Our results show that the simulated oceanic turbulence strongly affects the GI. The quality of image decreases monotonously with an increase of the strength of turbulence whereas the visibility increases. When the illumination light carries a twist phase, the visibility of the image is improved while the quality of the image is reduced in contrast to those without a twist phase. By properly selecting the strength of the twist phase, the image can still be maintained at an acceptable level of quality with high visibility. Furthermore, it is found that the quality and visibility of the ghost image are less affected by the oceanic turbulence using a TGSM beam with larger twist factor. Our findings will be useful for the application of GI in an oceanic turbulent environment.
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KÖMÜRCÜ, Kıvanç. "A STUDY FOR BUSINESS INTERNAL ENVIRONMENT TURBULENCE MANAGEMENT." International Journal Of Eurasia Social Sciences 10, no. 37 (January 1, 2019): 783–808. http://dx.doi.org/10.35826/ijoess.2619.
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Hardisty, Jack, and Ross Jennings. "The parameterisation of turbulence in the marine environment." Journal of Marine Engineering & Technology 16, no. 3 (December 14, 2016): 114–20. http://dx.doi.org/10.1080/20464177.2016.1260892.
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Heinz, Julia, Max B. Schäfer, Kent W. Stewart, and Peter P. Pott. "Low-turbulence displacement-flow for an operating environment." Current Directions in Biomedical Engineering 5, no. 1 (September 1, 2019): 509–11. http://dx.doi.org/10.1515/cdbme-2019-0128.
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AbstractIn developing countries airborne micro-organisms are one of the most common causes of surgical wound infection. In the operating room low-turbulence displacementflow has been shown to reduce the influence of airborne bacteria. However, due to complexity and cost, current systems are not accessible to all potential users. In this paper a low-cost ventilation system is presented that provides lowturbulence displacement-flow over a surgical operating environment. A stand-alone, simple to assemble, mobile airflow system was developed using the principle of speed compensation for laminar airflow. From visual inspection and measurements, the system was seen to generate a continuous downwards displacement of air over the protected area around the situs. The entire system can be assembled quickly with minimal standard tools, making it very suitable for mobile use, such as in disaster areas. Future work is required to achieve the vertical dimension of a laminar flow field required by the DIN 1946-4. Overall, the low-cost and simple system could provide many potential users access to the technology and thus improving hygiene conditions in their operating environment.
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SCHRADER, LARS-UVE, SUBIR AMIN, and LUCA BRANDT. "Transition to turbulence in the boundary layer over a smooth and rough swept plate exposed to free-stream turbulence." Journal of Fluid Mechanics 646 (March 8, 2010): 297–325. http://dx.doi.org/10.1017/s0022112009993284.
Full textAbstract:
Receptivity, disturbance growth and transition to turbulence of the three-dimensional boundary layer developing on a swept flat plate are studied by means of numerical simulations. The flow is subject to a favourable pressure gradient and represents a model for swept-wing flow downstream of the leading edge and upstream of the pressure minimum of the wing. The boundary layer is perturbed by free-stream turbulence and localized surface roughness with random distribution in the spanwise direction. The intensity of the turbulent free-stream fluctuations ranges from conditions typical for free flight to higher levels usually encountered in turbo-machinery applications. The free-stream turbulence initially excites non-modal streak-like disturbances as in two-dimensional boundary layers, soon evolving into modal instabilities in the form of unsteady crossflow modes. The crossflow modes grow faster than the streaks and dominate the downstream disturbance environment in the layer. The results show that the receptivity mechanism is linear for the disturbance amplitudes under consideration, while the subsequent growth of the primary disturbances rapidly becomes affected by nonlinear saturation in particular for free-stream fluctuations with high intensity. Transition to turbulence occurs in the form of localized turbulent spots randomly appearing in the flow. The main features of the breakdown are presented for the case of travelling crossflow vortices induced by free-stream turbulence. The flow is also receptive to localized roughness strips, exciting stationary crossflow modes. The mode with most efficient receptivity dominates the downstream disturbance environment. When both free-stream fluctuations and wall roughness act on the boundary layer at the same time, transition is dominated by steady crossflow waves unless the incoming turbulence intensity is larger than about 0.5% for roughness amplitudes of about one tenth of the boundary-layer displacement thickness. The results show that a correct prediction of the disturbance behaviour can be obtained considering the receptivity and evolution of individual modes. In addition, we provide an estimate for the amplitudes of the external disturbance sources above which a fully nonlinear receptivity analysis is necessary.