Turbulence Levels Research Articles

The effect of supply chain collaboration on firms’ risk management under technology turbulence

This study addresses the question of how supply chain collaboration affects a firm’s competitive advantage. Building on the social exchange theory, this study investigates the impact of supply chain collaboration on risk management capabilities (i.e. routine risk management capability and extraordinary risk management capability) that further influence competitive advantages. Moreover, building on a contingency perspective, this study investigates the condition (i.e. technological turbulence) under which supply chain collaboration is more effective in enhancing risk management capabilities. As a result of an analysis of survey data from 264 U.S. manufacturing firms, this study shows that supply chain collaboration positively impacts routine and extraordinary risk management capabilities that further promote competitive advantage. The results also reveal that the positive indirect effects of supply chain collaboration on firms’ competitive advantage via routine and extraordinary risk management capabilities are stronger under a higher level of technological turbulence. With the emphasis on the importance of supply chain collaboration under high technological turbulence, the results advise managers to design an implementable risk management framework and adopt specific mitigation strategies for supply chain risks.

Effect of deployment of strategic leadership in the horticulture industry: a case study of selected flower farms in Kenya

The paper reports empirical findings drawn from a study undertaken to understand the dimensions of strategic leadership deployed among flower farms and the benefits that the flower farms have derived from deployment of strategic leadership. The context was selected due to its significance in contributing to the national economy and the level of turbulence experienced by the farms that requires a leadership style entrenching strategic thinking. 43 flower farms were sampled and primary data obtained using a structured questionnaire from CEOs, Deputy CEOs and heads of functional areas. Two dimensions of strategic leadership have been deployed to a low extent while two have been implemented to a moderate extent. The deployed dimensions of strategic leadership have significantly contributed to the flower farms performance by enhancing their capacity to attain growth at the rate of 15-20%. The study concluded that strategic leadership is relevant for deployment by the flower farms and raised implications for its deployment among organizations facing complex and turbulent environments. The paper called on future research to consider expanding the scope of the context of the investigation and conceptualization of the dimensions of strategic leadership based on other relevant theoretical frameworks anchoring strategic leadership.

Turbulent cylindrical fire whirl

The cylindrical fire whirl, characterized by nearly constant flame width in the axial direction and open flame tip, is a unique flame pattern of the buoyant diffusion flame under strong imposed rotation. This paper presents a combined experimental and analytical study to investigate the formation and flame geometry of turbulent cylindrical fire whirls. A medium-scale rotating screen facility (diameter: 2.0 m, height: 10.0 m) was utilized for experiments with independently controlled and finely regulated imposed circulation (Γ) and heat release rate (Q˙=15–250 kW), by using propane as the fuel. It was found that the formation of cylindrical fire whirl is accompanied by the downward movement of the unstable flame bulge, and the propagation velocity agreed well with the predictions of the classical vortex breakdown theory. The physical analysis showed that the onsets of cylindrical fire whirls would occur at specific critical values of Re/Bm, where Re and B are the dimensionless imposed circulation and the dimensionless fire buoyancy flux, respectively. The analytical results agree well with data from small to medium-scale experiments and field observation, with m = 1/4 and 1/3 for laminar and turbulent fire whirls, respectively. Contrary to the general fire whirl, the mean flame height decreases, and the mean flame width increases steadily with Γ in the cylindrical fire whirl. A flame height correlation is derived from the radially-integrated momentum and mixture fraction equations, and a flame width correlation is developed based on the concept of equal axial convection and radial diffusion times for the turbulent cylindrical fire whirl. The two models both couple the heat release rate and the imposed circulation, and agree well with the experimental data of this work. The enhanced turbulence level induced by the flow instability of vortex breakdown is suggested to be the dominant mechanism for flame height reduction and flame width increase in the turbulent cylindrical fire whirl.

Numerical study on the atomization mechanism and energy characteristics of synthetic jet/dual synthetic jets

Due to high-frequency oscillating flow characteristic, the synthetic jet/dual synthetic jets (SJ/DSJ) can break up the liquid film into fine droplets. SJ/DSJ atomization nozzle has been designed and studied in the early stage, but its atomizing mechanism is still unclear. Through numerical and experimental methods, this study reveals how the unsteady jet with high turbulence level causes instability at the gas–liquid interface. The SJ/DSJ atomization during the blowing stroke is mainly divided into two stages, namely the primary breakup induced by K-H instability and secondary atomization induced by R-T instability. While the liquid fragmentation caused by the reverse jet during the suction stroke includes two modes: passive-fracture mode induced by the aerodynamic force and active-detachment mode induced by the velocity difference. The variation of spray particle number with time obeys the lognormal distribution. The particle size ranges from 4 to 150 μm, and 60% of the spray particles are fine droplets with diameter less than 50 μm. The traditional method to improve the atomization performance is to increase the gas–liquid two-phase pressure, which requires more energy consumption. In this study, by comparing the atomization characteristics of SJ/DSJ and continuous jet, it’s proved that the atomization performance can be enhanced by leaps and bounds through active flow control. 63% of the SJ/DSJ kinetic energy is fully converted into liquid kinetic energy to form high-speed spray.

Studying the effect of incoming turbulence level on the flow in the blade wake

Studying the effect of incoming turbulence level on the flow in the blade wake

Application of Factorial Analysis to the Study of Vented Dust Explosions in Large Biomass Storage Silos

Dust explosions are a major concern in many industrial facilities and particularly in storage areas of biomass materials. Although venting standards (EN 14491 and NFPA 68) provide satisfactory safety levels for most industrial applications, they present some limitations and there exist situations that they do not contemplate. Vented dust explosions in a 4500 m3 silo for the storage of wood pellets were simulated by computational fluid dynamics. Maximum overpressures were registered and compared. The influence of several parameters including initial turbulence level, dust concentration, ignition location, and vent area was studied. A factorial analysis was carried out to determine the importance of each of the four parameters, along with possible interactions between them. The results showed great variations in the overpressures between the different scenarios simulated. Vent area, ignition location, and dust concentration showed similar effects on the overpressure (around 25%), while initial turbulence had half this effect (13%). One interaction effect out of the eleven possible interactions was identified as relevant for this specific industrial scenario: the combination of the ignition location and the initial turbulence, with an additional effect of 5% on the overpressure. The factorial analysis applied in this study could be of interest to the risk assessment of industrial facilities.

Higher-order turbulence statistics and multiscale characterization of morphodynamics in a riverbank section with an upstream mining pit

Channel dredging has become a common phenomenon across several fluvial systems. Pits dredged in the riverbank can influence the downstream turbulence and affect the bank slope and central channel morphodynamics. Erodible bed experiments were conducted in a laboratory flume having a riverbank cross section with three different bank slopes, i.e., 25°, 31°, and 40° with and without a mining pit. Flow over the bank slope and near the bank toe was most affected by the pit excavation at the channel upstream. Turbulence levels were amplified within the flow over the slope and near the bank toe. The logarithmic scaling range of higher-order fluctuations at the bank toe is greater for with pit case. The complex interaction of simultaneous processes like pit migration, sliding failure and bank erosion, and fluvial erosion was studied at multiple length scales and time scales. A wavelet cross correlation analysis was used to calculate the celerity of bedform migration at the bank toe along the flow. Statistical celerity of bedforms with smaller scales (up to 15 mm length scales) is significantly higher due to pit interaction. The study reveals that instream mining has notable effects on the inherent nature of higher-order turbulence statistics, especially near the bank slope and toe, as well as the multiscale morphological structures.

Supervised Machine Learning for Refractive Index Structure Parameter Modeling

The Hellenic Naval Academy (HNA) reports the latest results from a medium-range, near-maritime, free-space laser-communications-testing facility, between the lighthouse of Psitalia Island and the academy’s laboratory building. The FSO link is established within the premises of Piraeus port, with a path length of 2958 m and an average altitude of 35 m, mainly above water. Recently, the facility was upgraded through the addition of a BLS450 scintillometer, which is co-located with the MRV TS5000/155 FSO system and a WS-2000 weather station. This paper presents the preliminary optical turbulence measurements, collected from 24 to 31 of May 2022, alongside the macroscopic meteorological parameters. Four machine-learning algorithms (random forest (RF), gradient boosting regressor (GBR), single layer (ANN), and deep neural network (DNN)) were utilized for refractive-index-structural-parameter regression modeling. Additionally, another DNN was used to classify the strength level of the optical turbulence, as either strong or weak. The results showed very good prediction accuracy for all the models. Specifically, the ANN algorithm resulted in an R-squared of 0.896 and a mean square error (MSE) of 0.0834; the RF algorithm also gave a highly acceptable R-squared of 0.865 and a root mean square error (RMSE) of 0.241. The Gradient Boosting Regressor (GBR) resulted in an R-squared of 0.851 and a RMSE of 0.252 and, finally, the DNN algorithm resulted in an R-squared of 0.79 and a RMSE of 0.088. The DNN-turbulence-strength-classification model exhibited a very acceptable classification performance, given the highly variability of our target value (Cn2), since we observed a predictive accuracy of 87% with the model.

Interaction between coherent and turbulent oscillations in non-reacting and reacting wake flows

The presence of large-scale coherent structures can significantly impact the dynamics of a turbulent flow field and the behaviour of a flame stabilized in that flow. The goal of this study is to analyse how increasing free-stream turbulence can change the response of the flow to longitudinal acoustic excitation of varying amplitudes. We study the flow in the wake of a cylindrical bluff body at both non-reacting and reacting conditions, as the presence of a flame can significantly alter the global stability of the flow. The frequency of longitudinal acoustic excitation is set to match the natural frequency of anti-symmetric vortex shedding for this configuration and we vary the free-stream turbulence using perforated plates upstream of the bluff body. The results show that varying the level of free-stream turbulence can influence not only the amplitude of the coherent flow response, but also the symmetry of vortex shedding in the presence of longitudinal acoustic excitation. Increasing the turbulence intensity can fundamentally change the structure of the time-averaged flow and can directly impact the coherent flow response in two ways. First, increasing turbulence intensity can enhance the amplitude of the natural anti-symmetric vortex shedding mode in the wake. Second, increasing turbulence intensity weakens the symmetric response of the flow to the longitudinal acoustic excitation. In the non-reacting and reacting conditions, both symmetric and anti-symmetric modes are present and are characterized using a spectral proper orthogonal decomposition. We see evidence of interaction between the symmetric and anti-symmetric modes, which leads to an interference pattern in the coherent vorticity response in the shear layers. We conclude by presenting a conceptual model for the influence that turbulence has on these flows.

CFD Assessment of the Bubble Flow in a 3D Rectangular Column

The purpose of this research is to better understand the characteristics of two-phase flow in a rectangular bubble column. Computational Fluid Dynamics (CFD) (ANSYS-FLUENT R15.0®) has been used to conduct numerical studies of the flow pattern. Furthermore, the experimental data is used to verify the accuracy of the numerical data. This unique CFD simulation research included a 3D system, Reynolds-Average, Navier-Stokes equations (RANS), k-turbulence model, and total interphase forces. Bulk flow patterns were revealed through CFD analysis. Total contact force, both constant and non-steady, is also analyzed for its impact. The data show liquid upflow in the column's bulk section and liquid downflow near the wall. In the gas phase, bubbles rose in the middle area and departed the bed. In addition, bubbles without enough velocity to leave the bed circulate towards the wall with liquid and follow a similar pattern. The results show that the phenomenon of the central peak can only be captured by using a single bubble and no drag forces. The correlation between simulation and experimental findings is excellent. Within the higher, middle, and nearby gas distributor height ranges, the outcome agrees extremely well with the experiment. In addition, the results of the experiments show that the level of turbulence has played a crucial role in dynamic behavior. The CFD model described qualitative and quantitative flow performance, producing excellent results. The results also gave a framework for comparing and evaluating future designs and gave insights into the fluid dynamics of the bubble column reactor. Efforts were made to compare and contrast the main operating modes of different reactor designs. Keywords: Two phase, Ansys, Bubble column, CFD, Drag force, Flow Pattern.

Transport-Equation-Based Shock Sensor for Shock–Turbulent Boundary-Layer Interaction

High-speed flows are often associated with shock–boundary-layer interaction (SBLI), which causes excessive vehicle surface heating and total pressure loss. Therefore, precise computational prediction of shock interactions becomes essential. Commonly used simulation techniques, including numerical schemes and turbulence models, give erroneous results at shock discontinuities. Local modifications are applied at shocks based on their location and strength. Most shock sensors in the literature predict shock location but do not give shock properties. We propose a shock function to locate shocks and estimate their strength in terms of density ratio by solving a transport equation, along with the governing equations of fluid flow. The sensitivity of the shock function to the transport equation’s parameters and grid resolution are explored. The shock function is used to define a shock sensor that can identify thin and sharp shocks. The shock function and shock sensor are then applied to an oblique shock impinging on a turbulent boundary layer. We use the shock unsteadiness modified model, which uses the estimated shock strength to predict the turbulence levels at shocks accurately. We study the effect of nonadiabatic wall temperature on the SBLI region, and the results are compared with available Direct Numerical Simulation (DNS) data.

Influence of boulder submergence ratio on local flow field: Implications for sediment and fish instream habitat

Boulder submergence ratio may influence surrounding flow structures and as a result, local sediment transport as well as instream habitat preference. In this work, particle image velocimetry (PIV) measurements were used to study the effects of varying submergence ratios in Regimes 2 (1.3 < submergence ratio < 4) and 3 (1 < submergence ratio < 1.3) on the local flow field downstream of a boulder within a rock-ramp boulder array. It was found that in the wake of a boulder, the mean and turbulent flow characteristics for the lowest submergence ratio (Regime 3) varied substantially from the higher ones in Regime 2. From the variations of principal Reynolds shear stress and turbulent bursting events, a higher likelihood of intense downstream erosion was predicted for the lowest submergence ratio. Increased levels of mean velocity and turbulence also indicated that the local flow in the lowest submergence ratio may provide a less preferred habitat for fish. The findings suggest that based on the most common flow stages using a boulder size that generates higher submergence ratios in Regime 2 may improve the performance of stream restoration projects.

On the wake characteristics of a model wind turbine and a porous disc: Effects of freestream turbulence intensity

Porous discs are the experimental counterparts of the numerical actuator disc concept and are frequently used in wind tunnel studies to reproduce the far-wake characteristics of wind turbines. The potential of using porous discs instead of wind turbines comes with the benefits such as operational easiness and design simplicity. This paper presents the results of an experimental study focusing on the wake development characteristics of a single porous disc and a single wind turbine under different freestream turbulence intensities but at similar Reynolds number conditions. The measurements are performed using two-dimensional two-component particle image velocimetry (2D2C PIV) technique up to seven diameters downstream distance in the wake of the models. The wake flows are analyzed in terms of the development of mean wake velocity deficit, wake decay, and wake turbulence characteristics. The results show that the wake recovery occurs faster for both the porous disc and the turbine with increasing freestream turbulence intensity. The wake width increases with the freestream turbulence intensity, indicating faster diffusion of the wake for both models. On the other hand, the wake width of the porous disc and the turbine is similar at the same turbulence intensity conditions, although they operate with slightly different thrust coefficients. Turbulent kinetic energy profiles in the far wake of the porous disc and the turbine, which are significantly different for the low turbulence intensity conditions, become similar for the high turbulence intensity case. The comparison of the turbulent kinetic energy, decay rate and production characteristics points to different turbulence mechanisms in the wake of the porous disc and the turbine. In the near wake, the wake decay rate and turbulent kinetic energy levels are higher in the porous disc case due to enhanced mixing levels associated with the grid-generated turbulence. In the far wake, the decay rate of the turbine wake is higher, most probably due to the breakdown of the tip vortices. When the freestream turbulence is increased, the differences in the turbulent wake flow characteristics diminish in the far wake, particularly after a 4.5-diameter downstream distance.

Transient behaviour of decelerating turbulent pipe flows

This investigation characterises the time response and the transient turbulence dynamics undergone by rapidly decelerating turbulent pipe flows. A series of direct numerical simulations of decelerating flows between two steady Reynolds numbers were conducted for this purpose. The statistical analyses reveal that rapidly decelerating turbulent flows undergo four coherent, unambiguous transitional stages: inertial (stage I), a dramatic change of sign in the viscous force associated with the decay of the viscous shear stress at the wall together with a mild turbulence decay in the viscous sublayer; friction recovery (stage II), a recovery in viscous force and progressive decay in the turbulent inertia at the near-wall region; turbulence decay (stage III), a balanced decay in both turbulent inertia and viscous force at the near-wall and overlap regions; core relaxation (stage IV), slow turbulence decay at the core region. The FIK identity derived by Fukagata, Iwamoto and Kasagi (Phys. Fluids, vol. 14, 2002, L73–L76) was used to understand further how the flow dynamics influence the time response of the skin friction coefficient ( $C_f$ ). The results show that although $C_f$ plateaus during the fourth stage, the turbulent contribution keeps decaying, undershoots and finally recovers to attain its final steady value. The time evolution of the azimuthal vorticity ( $\omega _\theta$ ) flux reveals that as the flow is decelerated, a layer of negative $\omega _\theta$ is produced at the wall during the flow excursion. As time progresses, this negative vorticity propagates in the wall-normal direction, attenuating the pre-existing vorticity and producing a decay in the turbulence levels.

The nature of the motions of multiphase filaments in the centers of galaxy clusters

The intracluster medium (ICM) in the centers of galaxy clusters is heavily influenced by the “feedback” from supermassive black holes (SMBHs). Feedback can drive turbulence in the ICM and turbulent dissipation can potentially be an important source of heating. Due to the limited spatial and spectral resolutions of X-ray telescopes, direct observations of turbulence in the hot ICM have been challenging. Recently, we developed a new method to measure turbulence in the ICM using multiphase filaments as tracers. These filaments are ubiquitous in cluster centers and can be observed at very high resolution using optical and radio telescopes. We study the kinematics of the filaments by measuring their velocity structure functions (VSFs) over a wide range of scales in the centers of ∼10 galaxy clusters. We find features of the VSFs that correlate with the SMBHs activities, suggesting that SMBHs are the main driver of gas motions in the centers of galaxy clusters. In all systems, the VSF is steeper than the classical Kolmogorov expectation and the slopes vary from system to system. One theoretical explanation is that the VSFs we have measured so far mostly reflect the motion of the driver (jets and bubbles) rather than the cascade of turbulence. We show that in Abell 1795, the VSF of the outer filaments far from the SMBH flattens on small scales to a Kolmogorov slope, suggesting that the cascade is only detectable farther out with the current telescope resolution. The level of turbulent heating computed at small scales is typically an order of magnitude lower than that estimated at the driving scale. Even though SMBH feedback heavily influences the kinematics of the ICM in cluster centers, the level of turbulence it drives is rather low, and turbulent heating can only offset ≲ 10% of the cooling loss, consistent with the findings of numerical simulations.

Experiments on upstream induction and wake flow for multirotor wind turbines

Multirotor wind turbine concepts are increasingly discussed as cost-effective alternatives for floating wind energy installations. When multiple smaller rotors are installed next to each other, the individual rotors experience local blockage from their neighbours. Depending on the rotor arrangement, the flow through and around the multirotors will differ leading to a local variation in axial forcing and power output on the individual rotors. In this lab-scale experiment, we investigate how the spacing between the single rotors in a multirotor of seven actuator discs affects the upstream flow, thrust force distribution and downstream wake flow. Reducing the inter-rotor spacing is observed to cause larger zones of upstream velocity reductions, both in streamwise and lateral direction. Consequently, the difference in thrust force between a locally blocked central rotor and the surrounding rotors also increases for smaller rotor spacing. Measurements of the downstream wake flow behind a multirotor model indicate a lower initial velocity deficit compared to a single rotor. Reduced rotor spacing is found to increase the wake’s initial velocity deficit and turbulence levels. Consequently, the wake recovers faster, resulting in similar velocity deficits independent of the rotor-spacing in the far wake region.

Proper Orthogonal Decomposition (POD) of the Wake Flow Field of a Model Wind Turbine and a Porous Disc under Different Freestream Turbulence Intensity Conditions

The effects of freestream turbulence intensity on the wake development of a model wind turbine and a porous disc are investigated through Proper Orthogonal Decomposition (POD) analysis. The capability of porous discs for reproducing far-wake characteristics of a model wind turbine is examined through coherent structures both in the near-wake and far-wake regions. Instantaneous velocity fields are obtained through wake measurements using two-dimensional two-component particle image velocimetry (2D2C PIV). These velocity fields are considered snapshots of the spatial domain. Results show inherent differences between coherent structures of a model wind turbine and porous disc in the near-wake region, especially when the freestream turbulent intensity level is low. However, these differences reduce, and coherent structures become more comparable when the freestream turbulence intensity level is higher. It is shown that the first five streamwise components of POD modes are paired for the model wind turbine and the porous disc cases under high freestream turbulence intensity conditions in the far-wake region.

Nepheloid layer dynamics overview of the Portuguese continental shelf

As part of project AQUIMAR, intensive CTD (conductivity, temperature and depth), and turbidity/particulate matter concentration (PMC) data were collected in four cruises along the Portuguese continental shelf, over three consecutive years under contrasting seasonal scenarios. Two of the cruises were carried out during Fall (5-26 October 2018 and 10 - 31 October 2019), one in Spring (18 April to 12 May 2019), and another under Winter conditions (24 February to 19 March 2020). Water samples were collected at the surface nepheloid layer (SNL) and bottom nepheloid layer (BNL) for evaluation particulate matter concentration (PMC) and composition. Differences found between the 5 sampled areas (Viana do Castelo-Porto; Aveiro-Figueira da Foz; Peniche-Santa Cruz; Setúbal-Sines; Sagres-Tavira), are well visible in T-S (temperature vs. salinity) diagrams based on CTD casts. PMC found in the study samples for all cruises was in the range of 0.1-10.2 g/m3. Turbidity meter data, calibrated and converted into inferred PMC values, showed that the study areas were generally characterized by low values, with the exception of some sporadic maxima found during Winter in the northern areas (between Minho River and the Cape Mondego). Particulate matter sample composition, obtained via X-ray diffraction, identified illite > chlorite > kaolinite > calcite > quartz > feldspars as major minerals, with clay minerals dominating and taking up more than 83% in average of the total identified mineral content. This analysis revealed that, for the Fall and Spring cruises, particles in the SNL were mainly biogenic, and for the BNL, the lithogenic material (average mica content of 71%) and biogenic calcite (average content of 10%) were dominant in all cruises. Cruise data also indicate that upwelling/downwelling and internal waves affected and promoted a higher level of turbulence in the water column, resulting in generally higher turbidity values, found in both the SNL and BNL.

Оценка цифрового потенциала стран БРИКС в условиях формирования нового геопорядка

The relevance of the research is determined by increasing trends in the changing landscape of the global economy and the redistribution of forces of economic influence between developed and developing countries. In this context, it is necessary to assess the digital potential of developing countries in order to determine the possibilities for their future development and achievement of global leadership. The purpose of the study is to analyze the specifics of the BRICS countries’ digital development at the current stage, which is characterized by a high level of turbulence, and to identify the areas of public policy that will help them build their digital potential. Research objectives are to analyze the main indicators that characterize the BRICS countries’ digital potential, to assess the impact of the COVID-19 pandemic on the BRICS countries’ digital potential and their position in the global economy, to identify the areas of public policy that contribute to building the BRICS countries’ digital potential in the global landscape. The authors evaluated the available digital potential of the BRICS countries and also carried out a comparative analysis of their capabilities with the potential of the most developed countries under conditions of external turbulence. It was revealed that the digital potential of the BRICS countries is lower than that of the most developed countries due to weaker digital infrastructure, but increasing digital activity in times of turbulence opens up new opportunities for them to realize their potential. The implementation of public policy in key areas of digital development will help align the BRICS integration association with the group of developed countries and may be the beginning of a new stage in the reconfiguration of the global economy.

Mass Transfer of Hydrogen Sulfide at Turbulent Water Surface by Falling Drops or a Single Jet

Hydrogen sulfide (H2S) is a primary cause of odor and corrosion in sewer systems. In drop structures, falling wastewater impinges the surface of bottom water pool as a jet or numerous drops, triggering a high level of turbulence and thus enhancing the emission of H2S and the absorption of oxygen (O2) at the pool surface. In this study, laboratory experiments were conducted to study the mass transfer at the pool surface with falling water drops or a single jet of water. In the test range of falling flow rate of 49–223 mm/h and falling velocity of 3.1–5.2 m/s [kinetic energy flux (KEF)=0.11–0.80 J/(m2·s)], the mass transfer coefficient KL for the pool surface was found to be 2.6–14.8×10−5 m/s for H2S. In addition, KL was found to be 76% larger when the pool surface was impinged by water drops than by a single jet. KL was 27%−47% larger in the half of the water surface directly receiving the drops or jet than the other half. The increase of water depth in the pool promoted the mass transfer, especially for the scenario of falling jet. Equations were proposed to predict KL under drops or jet. Moreover, KL for H2S and for O2 was found almost the same, indicating O2 can be a safe surrogate gas for H2S. Finally, the research results were applied to estimate H2S emissions at the pool surface of a prototype drop structure with a falling height of up to 10 m, which showed that turbulent wastewater surface can enhance mass transfer over 100 times compared with a quiescent surface.