Shear Environment Research Articles

The Formation of Stable Lung Tumor Spheroids during Random Positioning Involves Increased Estrogen Sensitivity.

The formation of tumor spheroids on the random positioning machine (RPM) is a complex and important process, as it enables the study of metastasis ex vivo. However, this process is not yet understood in detail. In this study, we compared the RPM-induced spheroid formation of two cell types of lung carcinoma (NCI-H1703 squamous cell carcinoma cells and Calu-3 adenocarcinoma cells). While NCI-H1703 cells were mainly present as spheroids after 3 days of random positioning, Calu-3 cells remained predominantly as a cell layer. We found that two-dimensional-growing Calu-3 cells have less mucin-1, further downregulate their expression on the RPM and therefore exhibit a higher adhesiveness. In addition, we observed that Calu-3 cells can form spheroids, but they are unstable due to an imbalanced ratio of adhesion proteins (β1-integrin, E-cadherin) and anti-adhesion proteins (mucin-1) and are likely to disintegrate in the shear environment of the RPM. RPM-exposed Calu-3 cells showed a strongly upregulated expression of the estrogen receptor alpha gene ESR1. In the presence of 17β-estradiol or phenol red, more stable Calu-3 spheroids were formed, which was presumably related to an increased amount of E-cadherin in the cell aggregates. Thus, RPM-induced tumor spheroid formation depends not solely on cell-type-specific properties but also on the complex interplay between the mechanical influences of the RPM and, to some extent, the chemical composition of the medium used during the experiments.

Analysis of grease mechanical degradation in standard equipment

As a grease is used in a bearing, its rheological properties may change substantially due to prolonged shear, causing it to no longer meet its application requirements. The change to grease structural integrity may be succinctly quantified by measuring the change in consistency, corresponding to shear/mechanical stability. There are only two standardized methods for measuring the mechanical stability of greases: prolonged working in a grease worker and subjecting to roller degradation in a roll stability test. This paper provides a detailed analysis of the shear environment of these two tests and uses recently identified measurement techniques to track the degradation of two different greases over time in each test. Results are then compared to shearing in a rheometer at shear rates that are estimated to be similar. It is shown that the shearing environments within the grease worker and roll stability test can be predicted and reproduced with reasonable accuracy in a rheometer. Various time scales of mechanical stability are identified, with the standard two-hour duration of the roll stability test found to exist within a transient time scale that may not accurately reflect the long-term mechanical stability of a grease. This study demonstrates that both tools can be used to reasonably estimate the changes to mechanical properties of a grease during the churning phase of a bearing or milling process during manufacturing, though it is recommended that the duration of the standard roll stability test be extended beyond the identified transient period.

Thermal Vibration of Thick FGM Conical Shells by Using Third-Order Shear Deformation Theory.

A time-dependent third-order shear deformation theory (TSDT) approach on the displacements of thick functionally graded material (FGM) conical shells under dynamic thermal vibration is studied. Dynamic equations of motion with TSDT for thick FGM conical shells are applied directly with the partial derivative of variable R*θ in the curve coordinates (x, θ, z) instead of y in the Cartesian coordinates (x, y, z) for thick FGM plates, where R* is the middle-surface radius at any point on conical shells. The generalized differential quadrature (GDQ) numerical method is used to solve the dynamic differential equations in equilibrium matrix forms under thermal loads. It is the novelty of the current study to identify the parametric effects of shear correction coefficient, environment temperature, TSDT model, and FGM power law index on the displacements and stresses in the thick conical shells only subjected to sinusoidal heating loads. The physical parts with values on the length-to-thickness ratio equals 5, and 10 FGMs can be used in an area of an airplane engine that usually operates near more than 1000 K of temperatures when the thermal stress is considered and affected. The important findings of the presented study are listed as follows. The values of normal stress are in decreasing tendencies with time in cases when the coefficient c1 equals 0.925925/mm2 in TSDT and length-to-thickness ratio equals 5. The shear stress values in x plane z direction on the minor middle-surface radius (r) equals the major middle-surface radius (R) over 8 and length-to-thickness ratio equals to 5 can withstand T = 1000 K of pressure.

Analyzing of hydrodynamic stress and mass transfer requirements of a fermentation process carried out in a coaxial bioreactor: a scale-up study.

Fluid hydrodynamic stress has a deterministic effect on the morphology of filamentous fungi. Although the coaxial mixer has been recognized as a suitable gas dispersion system for minimizing inhomogeneities within a bioreactor, its performance for achieving enhanced oxygen transfer while operating at a reduced shear environment has not been investigated yet, specifically upon scale-up. Therefore, the influence of the impeller type, aeration rate, and central impeller retrofitting on the efficacy of an abiotic coaxial system containing a shear-thinning fluid was examined. The aim was to assess the hydrodynamic parameters, including stress, mass transfer, bubble size, and gas hold-up, upon conducting a scale-up study. The investigation was conducted through dynamic gassing-in, tomography, and computational fluid dynamics combined with population balance methods. It was observed that the coaxial bioreactor performance was strongly influenced by the agitator type. In addition, coaxial bioreactors are scalable in terms of shear environment and oxygen transfer rate.

The Impact of High-Density Airborne Observations and Atmospheric Motion Vector Observation Assimilation on the Prediction of Rapid Intensification of Hurricane Matthew (2016)

Tropical cyclone rapid intensification (RI) prediction still remains a big international challenge in numerical weather prediction. Hurricane Matthew (2016) underwent extreme and non-classic RI, intensifying from a Category 1 storm to a Category 5 hurricane within 24 h under a strong vertical shear environment. However, most models failed to capture this RI, and limited or no inner core, and outflow observations were assimilated in the NWS operational HWRF Model before the onset of RI for Matthew (2016). The goals of the study are to (1) explore the best way to assimilate the High-Density Observations (HDOB, including FL and SFMR) and AMV data; (2) study the impact of assimilating these observations on the analysis of both the inner-core and outflow structures; and (3) examine the impact of assimilating these data on the prediction of RI for Matthew. The main results are as follows: (1) With proper pre-processing of the HDOB observations and by using a 4DEnVar method, the inner-core structure analysis was improved. And the RI prediction is more consistent with the best track without spin-down for the first 24 h. Assimilating CIMMS AMV observations on top of the HDOB observations further improves both the track and intensity forecasts. Specifically, both the magnitude and timing of the peak intensity are further improved. (2) Diagnostics are conducted to understand how the assimilation of these different types of observations impacts RI prediction. Without assimilating HODB and AMV data, baseline experimentover-predict the intensification rate during the first 18 h, but under-predict RI after 18 h. However, the assimilation of FL and SFMR and CIMMS AMV correctly weakens the upper-level outflow and improves the shear-relative structure of the inner-core vortex, such as reducing the low-level moisture in the downshear left quadrant. The deep convection on the downshear side is weaker than baseline for the first 18 h but keeps enhancing, later moving cyclonically to the USL quadrant, and then causes more subsidence warming, maximizing in the USL quadrant and the maximum wind increases faster. Moreover, the rapid intensification rate is much more consistent with the best track and the forecast skill of RI is improved. Therefore, 4DEnVar assimilation with proper pre-processing of the high-density observations can indeed correct the shear-relative moisture and structural distributions of both the inner core and environment for TCs imbedded in the stronger shear, which is important for shear-TC RI prediction.

Environmental ingredients that lead to tornado outbreak and tornado failure: A comparison between two similar recurving tropical cyclones

AbstractRecurving tropical cyclones (TCs) can sometimes produce tornado outbreaks, while some TCs with similar tracks and intensities may produce none of tornado, which makes it challenging to assess tornado risk within recurving TCs. This study investigates two recurving TCs, Typhoon Yagi (2018) and Typhoon In‐Fa (2021), that made landfall in eastern China. Despite the similar recurving tracks and intensities, Yagi produced 11 tornadoes while In‐Fa produced none. Results show that both TCs were characterized by similar large‐scale conditions that were dynamically favourable for tornadoes during the recurvature process. The non‐tornadic In‐Fa even featured a higher shear and helicity environment in its northeast sector than did the tornado‐productive Yagi. The greatest difference between Yagi and In‐Fa is the thermodynamic instability owing to the different lower–middle‐tropospheric lapse rates that are attributable to the differences in air trajectories at low levels. In‐Fa featured marginal instability due to the cooler air at low levels because almost all of the air parcels came from the Pacific Ocean while most air parcels for Yagi came from the warm land. The cooler low‐level air tends to create higher relative humidity in In‐Fa's interior and thus leads to widespread precipitation which in turn also contributes to the low‐level cooling. The different air trajectories are demonstrated related to the TC's translation speed, size and synoptic characteristics days before TC's landfall. Numerical simulations suggest that the upward motions within the widespread precipitation regions of In‐Fa are overall weaker than those of Yagi due to the limited instability in the former. These findings suggest that even though two TCs were characterized by similar tracks, intensities and large‐scale forcings, their different low‐level air pathways may have significant influence on priming the mesoscale environment for supercell or tornado formation.

Effect of bluff body embedded in flow channel on power performance of microbial fuel cell

The microbial fuel cell (MFC) has emerged as an eco-friendly method for generating clean energy from wastewater. However, its current power performance falls short of meeting commercial application requirements, highlighting the urgent need for power enhancement. To address this, the implementation of bluff bodies within the MFC channel is a proof of concept to enhance nutrient mass transport without the need for external energy input. In this study, fluid simulation was first conducted to analyze the impact of different bluff body designs on flow regimes. The results showing bluff body having spread-out six circles arrays with a height of 0.5 mm (6C_H5) led to a wide velocity distribution within the flow channel, high velocity, and no solute accumulation on the electrode surface, thereby facilitating increased nutrient coverage during transport. Through experimental confirmation, MFC with 6C_H5 achieved an impressive 154 % increase in maximum power density compared to without a bluff body. The outcome can be attributed to sufficient nutrient acquisition for the bacteria to generate more power due to better nutrient transport and a shear environment. The significant finding of the bluff body’s impact on the fluid dynamic aspect has proven the feasibility of enhancing MFC power performance.

Shear stress and microRNAs for better metastatic cancer management.

Metastasis is the process by which cancer cells move from the primary location to establish themselves in a new location in the human body. It is still a significant challenge in cancer management because it is responsible for 90% of cancer-related deaths. In this work, we present an idea to use shear stress encountered by all metastasizing cells as an elegant means to deactivate metastasizing cancer cells. Shear-induced ROS and cross-talk between ROS and miRNA play crucial roles in deactivating metastasizing cancer cells. In addition, there exists a vast therapeutic potential for miRNAs. Therefore, this study explores the effect of shear on miRNAs and reactive oxygen species (ROS), the two molecular mediators in the proposed {shear-stress}-{miRNA}-{metastasizing-cancer-cell-deactivation} approach. In this context, to understand the effect of defined shear on HCT116 colon cancer cells, they were cultivated in a defined shear environment provided by an appropriately designed and fabricated cone-and-plate device. Shear rate affected the culture growth characteristics and the specific intracellular reactive oxygen species level (si-ROS). HCT116 cell growth was observed at 0 and 0.63 s-1 but not at 1.57 s-1 or beyond. Shear rate induced upregulation of the hsa-miR-335-5p but induced downregulation of hsa-miR-34a-5p. Furthermore, the specific levels of hsa-miR-335-5p, hsa-miR-26b-5p, and hsa-miR-34a-5p negatively correlated with specific intracellular (si)-hydroxyl radical levels. In addition, some messenger RNAs (mRNAs) in HCT116 cells showed a differential expression under shear stress, notably the ROS-associated mRNA of PMAIP1. The above miRNAs (and possibly some mRNAs) could be targeted to manage colon cancer metastasis.

Lattice preferred orientation of quartz in granitic gneisses from Tso Morari Crystalline Complex, Eastern Ladakh, trans-Himalaya: evaluating effect of Dauphiné twin in dynamic recrystallization during exhumation

Abstract The Tso Morari Crystalline complex (TMCC) of eastern Ladakh, India, is part of the north Indian continental margin and is characterized by eclogitic enclaves embedded within ortho- and paragneisses known as the Puga Gneiss. Two fault zones bound the TMCC: the Karzok fault to the southwest and the Zildat fault to the northeast. In the present study, we carried out Electron Backscatter Diffraction study of quartz of 10 samples collected from the Puga Gneiss. The relict and recrystallized quartz grains were treated separately to understand the deformation conditions of the Puga Gneiss during early and late deformation stages related to UHP metamorphism and final stage of exhumation during retrogression, respectively. Microstructural observations suggest dynamic recrystallization in quartz and plagioclase at different temperature ranges. Misorientation analysis of both relict and recrystallized quartz grains reveals presence of Dauphiné Twins. Lattice preferred Orientation (LPO) of <c> axis of relict quartz grains generally shows more than one point maxima indicating that the relict grains preserve LPO developed during different stages of metamorphism/deformation. On the other hand, LPO of <c> axis of recrystallized grains from Karzok and Zildat fault zones shows asymmetric single girdle either normal or at an angle to the foliation plane, which suggests simple shear. We conclude that grain size reduction and recrystallization of the Puga Gneiss was greatly influenced by Dauphiné Twin and the final exhumation of the TMCC took place in a simple shear environment aided by activity along its two binding fault zones.

Insights into the relation between vertical cloud structure and dynamics of three polar lows: Observations from COMBLE

AbstractThe vertical structure of three polar lows is described using profiling radar, lidar, and passive remote sensors deployed at a coastal site in northern Norway. The data were collected as part of the Cold‐air Outbreaks in the Marine Boundary Layer Experiment (COMBLE). These data are examined in the context of satellite imagery, operational weather radar reflectivity imagery, and output from the AROME Arctic model. A comparison to satellite images shows that AROME‐Arctic captured the polar lows well. All three polar lows form in marine cold‐air outbreaks and are surrounded by open‐cellular convection typical of such outbreaks. Two of the lows form in a forward shear environment and one under reverse shear. Initially, the three polar lows are comma shaped; two of them transition to be more spiraliform at their mature stage and have mostly cloud‐free warm cores. The warm cores are the result of a warm‐seclusion process. All three lows have stratiform precipitation bands, marked by little cloud liquid water, and rather high surface precipitation rate. The vertical drafts and turbulence in these stratiform clouds are generally weak. All three lows also have convective clouds, which have stronger vertical drafts, stronger turbulence, and pockets of high liquid water content.

Initial platelet aggregation in the complex shear environment of a punctured vessel model

To analyze flow conditions and cellular behavior at the onset of a hemostatic response in the injury of a microneedle-induced vessel puncture, a combined in silico and in vitro platform is created. A cell-resolved blood flow model is utilized for in-depth flow profile and cell distribution analyses, and a novel punctured vessel flow chamber is set up to complement the simulations with the evaluation of platelet aggregation around the wound neck of the puncture. The respective setups of the platform are explained, and the results of both experiments and simulations with various puncture diameters and pressure drops are combined, providing detailed insight into the basic processes of platelet transport and aggregation in the wound area. A special emphasis of the simulation evaluation is put on the cell distributions and the magnitude of shear rate and elongational flow in the wound neck area, as well as downstream from the puncture. Additionally, possible implications of wound size and pressure difference on the hemostatic response are discussed. The simulations display asymmetric cell distributions between the proximal and distal sides of the wound neck in regard to the flow direction. The flow chamber with the puncture diameter closest to the simulated domains confirms this asymmetry by displaying increased platelet aggregation at the wound neck's distal side. The presented punctured vessel in silico and in vitro experimental setups offer a platform to analyze the hemostatic environment of a vessel injured by a puncture and might assist in identifying differentiating factors between primary hemostasis and arterial thrombosis.

Development of a scale-up strategy for an aerated coaxial mixer containing a non-Newtonian fluid: A mass transfer approach

Coaxial mixers have been shown to be effective in enhancing the hydrodynamic stress and shear environment inside the aerated systems. However, the scale-up study of the aerated coaxial mixing reactors based on a constant mass transfer coefficient has never been reported in the literature. In this study, for the first time, a practical technique is suggested to evaluate the scalability of these systems in terms of a constant mass transfer coefficient. The effects of impeller speed, impeller type, aeration rate, and pumping direction on the mass transfer, power consumption, gas holdup profile, fluid hydrodynamics, and energy dissipation rate were explored for gas dispersion in non-Newtonian fluids inside coaxial mixers through tomography, dynamic gassing-in, and computational fluid dynamics. It was found that a practical approach to preserve the mass transfer coefficient of the large-scale coaxial mixer the same as its small-scale counterpart was to maintain the volumetric aeration rate per working fluid volume constant.

Shear Enhanced Flotation Separation Technology in Winery Wastewater Treatment

The process of wine making is well known to produce large amounts of wastewater with highly variable characteristics. The disposal of untreated winery wastewater is strictly prohibited since it adversely affects the recipient environment. Due to the variability in characteristics of winery wastewater, developing a treatment system which can handle high organic and inorganic loads, especially during the vintage season, is a complex challenge. This study investigated the theory, methodology and implementation of a wastewater treatment technology called shear enhanced flotation separation (SEFS) as a potential primary treatment stage towards the treatment of winery wastewater. Winery effluent was subjected to a coagulation process in a high shear environment, with and without the introduction of air, followed by flocculation. Upon successful optimization of operating parameters, a polymeric-based coagulant AB121 and polyelectrolyte flocculant AB796 yielded the highest reduction in turbidity (95%) with typical values of 630 NTU for the raw wastewater and 25 NTU for the SEFS-treated effluent. A substantial reduction in total suspended solids (97%) was achieved with average raw winery wastewater values of 2275 mg/L compared to the 50 mg/L obtained for the SEFS-treated effluent. Furthermore, a notable reduction (54%) in COD (from 11,250 mg/L to 5220 mg/L) using SEFS technology was achieved.

Analysis of the Development Mechanisms of a Polar Low over the Norwegian Sea Simulated with the Canadian Regional Climate Model

Polar lows (PLs) are maritime mesoscale cyclones associated with severe weather. They develop during marine cold air outbreaks near coastlines and the sea ice edge. Unfortunately, our knowledge about the mechanisms leading to PL development is still incomplete. This study aims to provide a detailed analysis of the development mechanisms of a PL that formed over the Norwegian Sea on 25 March 2019 using the output of a simulation with the sixth version of the Canadian Regional Climate Model (CRCM6/GEM4), a convection-permitting model. First, the life cycle of the PL is described and the vertical wind shear environment is analysed. Then, the horizontal wind divergence and the baroclinic conversion term are computed, and a surface pressure tendency equation is developed. In addition, the roles of atmospheric static stability, latent heat release, and surface heat and moisture fluxes are explored. The results show that the PL developed in a forward-shear environment and that moist baroclinic instability played a major role in its genesis and intensification. Baroclinic instability was initially only present at low levels of the atmosphere, but later extended upward until it reached the mid-troposphere. Whereas the latent heat of condensation and the surface heat fluxes also contributed to the development of the PL, convective available potential energy and barotropic conversion do not seem to have played a major role in its intensification. In conclusion, this study shows that a convection-permitting model simulation is a powerful tool to study the details of the structure of PLs, as well as their development mechanisms.

The dispersion of Trichosporon fermentans was controlled by optimizing the shear environment in the reactor to improve the cell sedimentation and separation performance

The morphology of pseudomycelium in Trichosporon fermentans is not conducive to the accumulation of lipids and the recovery of yeast cells by sedimentation. In this study, the computational fluid dynamics method was used to study the effects of shear force on the flow field distribution and on the dimorphism transition and dispersion of yeast cells in a 5 L stirred bioreactor, and to explore the sedimentation performance of yeast cells in different forms. It was shown that under the condition of moderate shear force, such as 3.45 Pa corresponding to a stirring speed of 300 rpm as selected in this experiment, most of the yeast cells in the fermentation broth were spherical or short rod-shaped, and there were almost no pseudohyphal yeasts, which contributed to the good sedimentation performance of the yeast cells. The results showed that the appropriate shear force could effectively inhibit the transformation of yeast cells into pseudohyphae, retain a large number of cells in a single cell shape, enhance cell dispersion and facilitate cell contact, absorption and utilization of organic substrates, as well as increase the lipid accumulation in yeast cells. By controlling the shear force, after 40 h of treatment of RSOW using Trichosporon fermentans, the chemical oxygen demand and oil content removal were approximately 95.81% and 88.09%, respectively, which indicate a significant improvement compared with those before optimizing the shear environment. Therefore, based on shear control of the cell morphology to improve yeast cell dispersion and sedimentation performance, the oily wastewater treatment method established in this study can be used to guide the process design of fermented Trichosporon fermentans for the treatment of RSOW and the resource recycling of yeasts.

Oxygen transfer and gas holdup in airlift bioreactors assembled with helical flow promoters.

Bioreactors can perform biochemical conversions mediated by biocatalysts, such as enzymes, animal cells, plants, and microorganisms. Among several existing models, airlift bioreactors are devices with the low shear environment and good mass transfer with low energy consumption, employed in several biochemical processes. The fluid flow is enabled through air injection by the sparger located at the bioreactor base. Despite its simple geometry compared with the conventional bioreactors, airlift performance can be optimized via geometrical modifications. Therefore, the objective of this work was to evaluate the effects of the addition of helical flow promoters, positioned in the riser and/or downcomer regions of an airlift of concentric tubes measuring the volumetric oxygen coefficient (kLa) and gas holdup. The results obtained by varying the gas flow rate from 1.0 to 4.0 vvm allowed the system evaluation of oxygen transfer and gas holdup. The inclusion of helical flow promoters increased the kLa, reaching up to 23% in oxygen transfer compared to tests without helicoids and up to 14% increase in the gas holdup. The inclusion of helical flow promotors was beneficial for all gas flow rates. Thus, including these flow promoters is an effective strategy to increase the oxygen transfer rate for bioprocess optimization.

Design and engineering characterization of a horizontal tubular bioreactor with spiral impeller for cell cultivation

Aerated stirred tank bioreactors (STRs) are the norm for commercial production of biologicals but tend to exert high shear forces from high impeller tip speeds, direct sparging, bubble disruption at the surface and foam formation. In this work, a novel 5 liter horizontal tubular bioreactor (HTB) fitted with a spiral impeller was designed for cell cultures. The abiotic and engineering characterization of the HTB was undertaken in terms of fluid flow pattern, mixing time (θm), minimum agitation speed Njs, volumetric oxygen mass transfer coefficient (kLa), and power consumption (P). The bioreactor showed optimum operability between 2 and 3 litre, and comparable mixing time ranges, power consumption and volumetric oxygen mass transfer coefficients (kLa) between 5 and 16 h−1 to a STR and other conventional systems. An ANOVA analysis disseminated that impeller immersion and mixing speeds had significant effects on mixing times, while aeration rates and mixing speeds significantly impacted kLa. The abiotic and engineering characterization investigations revealed that the bioreactor design supported good surface aeration with bubble entrainment for oxygen mass transfer while imparting low energy into the system, which are key attributes in promoting a low shear environment for cell culturing.

Identification of seismically active areas of the Voronezh anteclise by geomorphological and tectonophysical methods

Using the method of cluster analysis of morphometric parameters of the relief, the areas within which most of the epicenters of modern earthquakes of the Voronezh anteclise are located are identified. With the help of computer modeling, the areas of possible formation of new small-length discontinuities in the modern stress field are outlined. On the basis of complex geological and geomorphological data we created a tectonophysical model that explains the nature of seismicity by the development of geodynamically active zones in a shear environment with the orientation of the axis of maximum compression in the north-west direction.

Study on the mass transfer characteristics of gas and liquid phases in a three-layer combined paddle fermenter

A three-layer combination paddle fermenter was proposed for improving the phenomenon of uneven gas dispersion and dead zones at the bottom of small and medium-sized gas-liquid fermenters. The population balance model (PBM) was used to numerically calculate the internal flow field of the fermenter, and the effects of the baffle and rotational speed on the turbulence intensity and mass transfer characteristics were systematically investigated. The results show that the addition of baffles in the three-layer combined paddle fermenter can increase the turbulence intensity and effectively improve the uneven gas dispersion. Increasing the rotational speed provides a better shear environment for bubble crushing and is conducive to enhancing the gas-liquid mass transfer capacity. The local KLa distribution in the fermenter with baffle is more uniform.

Enhancing bioflocculation in high-rate activated sludge improves effluent quality yet increases sensitivity to surface overflow rate

High-rate activated sludge (HRAS) relies on good bioflocculation and subsequent solid-liquid separation to maximize the capture of organics. However, full-scale applications often suffer from poor and unpredictable effluent suspended solids (ESS). While the biological aspects of bioflocculation are thoroughly investigated, the effects of fines (settling velocity < 0.6 m3/m2/h), shear and surface overflow rate (SOR) are unclear. This work tackled the impact of fines, shear, and SOR on the ESS in absence of settleable influent solids. This was assessed on a full-scale HRAS step-feed (SF) and pilot-scale HRAS contact-stabilization (CS) configuration using batch settling tests, controlled clarifier experiments, and continuous operation of reactors. Fines contributed up to 25% of the ESS in the full-scale SF configuration. ESS decreased up to 30 mg TSS/L when bioflocculation was enhanced with the CS configuration. The feast-famine regime applied in CS promoted the production of high-quality extracellular polymeric substances (EPS). However, this resulted in a narrow and unfavorable settling velocity distribution, with 50% ± 5% of the sludge mass settling between 0.6 and 1.5 m3/m2/h, thus increasing sensitivity towards SOR changes. A low shear environment (20 s−1) before the clarifier for at least one min was enough to ensure the best possible settling velocity distribution, regardless of prior shear conditions. Overall, this paper provides a more complete view on the drivers of ESS in HRAS systems, creating the foundation for the design of effective HRAS clarifiers. Tangible recommendations are given on how to manage fines and establish the optimal settling velocity of the sludge.