Effect Of Aperture Size Research Articles

Macro-microscopic mechanical behavior of geogrid reinforced calcareous sand subjected to triaxial loads: Effects of aperture size and tensile resistance

Reinforcing calcareous sands with geogrids is a potentially effective method for large-scale geotechnical constructions in coastal lands. The breakable nature of polygonal calcareous sands determines the complex particle-geogrid interactions. A three-dimensional numerical model of geogrid reinforced calcareous sand (GRCS) was established to investigate the potential mechanical laws based on the discrete element method (DEM), and the reasonableness of the numerical model was verified by comparing with the indoor triaxial test. It follows that the macro-microscopic mechanical behavior of GRCS under the influence of aperture size and tensile resistance of geogrids was further investigated via effective DEM simulations. The presented results show that the decreased aperture size and increased tensile resistance are beneficial to enhance the macro-mechanical properties of GRCS, including strength, internal friction angle and pseudo cohesion. Particle crushing is mainly affected by shear strain and confining pressure. The bulging deformation of GRCS is partially suppressed due to the confining effect of geogrids. Besides, the source of strength enhancement of GRCS is revealed based on the microscopic particle-geogrid interactions, and the calculation method of horizontal and vertical additional stresses in the reinforced soil element considering the effects of tensile resistance and aperture size is further established.

CFD-DEM investigation of the effects of aperture size for a capsule-based dry powder inhaler

Capsule based dry powder inhalers (DPIs) often require piercing of the capsule before inhalation, and the characteristics of the apertures (punctured holes) affect air flow and the release of powders from the capsule. This work develops a numerical model based on the two-way coupling of computational fluid dynamics and discrete element method (CFD-DEM) to investigate the effect of aperture size on powder dispersion in the Aerolizer® device loaded with only carrier particles (lactose). Powders (carrier particles) in the size range 60–140 μm (d50: 90 μm and span: 0.66) were initialized in a capsule which had a circular aperture at each end. Boundary conditions corresponding to an air flow rate of 45 L/min were specified at each inlet to the mixing chamber (i.e., a total flow rate 90 L/min), and a capsule spin speed of ∼ 4050 rpm. The velocity magnitudes inside the capsule were considerably lower than those in the mixing chamber in the vicinity of the rotating capsule, with the exception of the capsules featuring 2.5 mm and 4 mm apertures. Larger apertures reduced the capsule emptying time and increased the particle evacuation velocity; the fluid drag force on the particles issuing from the capsule peaked for an aperture of 1.3 mm. Inside the capsule, particle–particle (PP) collisions were more frequent than particle–wall (PW) collisions due to high concentration of powder, but PP collisions had smaller (median) impact energy than PW collisions. Larger apertures resulted in fewer collisions in the capsule with higher PW and virtually unchanged PP collision energies. Outside the capsule (i.e., in the inhaler mixing chamber), PW collisions occurred more frequently than PP collisions with median collision energies typically two orders of magnitude higher than inside the capsule. Larger apertures resulted in more collisions with slightly reduced collision energy, but this effect plateaued for aperture sizes larger than 1.3 mm. Powder dispersion, expressed as the fine particle fraction (FPF) of the powder, was predicted using an empirical equation based on carrier PW collisions. Therefore, consistent with the model prediction of the effect of aperture sizes on the chamber collision frequency, FPF increased with aperture size but plateaued beyond 1.3 mm.

An IFS-based fractal discrete fracture network for hydraulic fracture behavior of rock mass

The discrete fracture network (DFN) model is applied for fluid flow and transport simulations in fractured rock masses. In this study, a novel two-dimensional fractal DFN generation method was proposed based on the iterative function system (IFS). To achieve the fine mesh for the DFN model, a refinement technique was presented to remove the short edges and small gaps. Subsequently, the zero-thickness flow cohesive element was inserted at the adjacent edge of elements for the hydraulic fracture modeling. The results indicated that the injection pressure of hydraulic fracture had three phases: Sudden increase, rapid drop-off, and stabilization. Compared with the traditional linear DFN model, the injection pressure evolution and fracture propagation of fractal DFN were significantly affected. In addition, the fracture aperture variation was an important factor influencing hydraulic fracturing in the rock mass. Considering the complexity of the hydraulic fracturing process, the effects of mesh sensitivity and fracture aperture size were also analyzed based on two-dimensional simulation results. This study presents a novel 2D DFN model for an accurate description of fracturing and provides a valuable simulation method for hydraulic fracturing.

The role of capsule aperture size on the dispersion of carrier-based formulation at different air flowrates

The effect of capsule aperture size on the aerosol performance of lactose blend formulation was studied using Foradil® (containing 12 μg of formoterol fumarate (FF11A list of all acronyms used in this paper can be found in the section “Abbreviations & Symbols.”.) and 24 mg of lactose) dispersed with a powder inhaler Aerolizer® at increasing air flowrates. Apertures sizes of 0.4, 1.0, 1.5, 2.5, and 4.0 mm were introduced at the opposite ends of the capsule. The formulation was dispersed into a Next Generation Impactor (NGI) at 30, 60 and 90 L/min, with the fine particle fractions (FPFrec and FPFem) measured by chemical assay of FF and lactose using high-performance liquid chromatography. Particle size distribution (PSD) of FF particles dispersed in wet media was also characterized by laser diffraction. FPFrec showed a stronger dependency on the flowrate than the capsule aperture size. The most efficient dispersion was achieved at 90 L/min. At a given flowrate, FPFem remained broadly constant across different aperture sizes. The laser diffraction studies demonstrated the presence of large agglomerates.

Large-Array Deep Abdominal Imaging in Fundamental and Harmonic Mode.

Deep abdominal images suffer from poor diffraction-limited lateral resolution. Extending the aperture size can improve resolution. However, phase distortion and clutter can limit the benefits of larger arrays. Previous studies have explored these effects using numerical simulations, multiple transducers, and mechanically swept arrays. In this work, we used an 8.8-cm linear array transducer to investigate the effects of aperture size when imaging through the abdominal wall. We acquired channel data in fundamental and harmonic modes using five aperture sizes. To avoid motion and increase the parameter sampling, we decoded the full-synthetic aperture data and retrospectively synthesized nine apertures (2.9-8.8 cm). We imaged a wire target and a phantom through ex vivo porcine abdominal samples and scanned the livers of 13 healthy subjects. We applied bulk sound speed correction to the wire target data. Although point resolution improved from 2.12 to 0.74 mm at 10.5 cm depth, contrast resolution often degraded with aperture size. In subjects, larger apertures resulted in an average maximum contrast degradation of 5.5 dB at 9-11 cm depth. However, larger apertures often led to visual detection of vascular targets unseen with conventional apertures. An average 3.7-dB contrast improvement over fundamental mode in subjects showed that the known benefits of tissue-harmonic imaging extend to larger arrays.

Sand-geogrid interfacial shear response revisited through additive manufacturing

Though it is known that the geometric features of geogrids are crucial for deriving optimal interface shear strength, not much work is done to optimize the size and shape of the apertures relative to the particle size of the soils in contact. Most of the commercial geogrids have rectangular or square apertures, which are many times bigger than the soil particles. The present study explores the effects of aperture size and shape of geogrids relative to the size of the sand particles on their interface shear response through direct shear tests and digital image analysis. Geogrids of different aperture sizes and shapes were manufactured using a 3D printer. Shear tests were carried out on three sands of different grain sizes interfacing with geogrids of five different aperture sizes and three different aperture shapes. Through these tests, interface shear response with a wide range of aperture ratio and different shapes of geogrids is understood. Shear zone thickness of different sand-geogrid interfaces was computed through Particle image velocimetry (PIV). Based on the tests and analyses, triangular apertures are found to be more efficient compared to other apertures. The optimal range of aperture ratio is found to be 2–11.29.

Congenital nasal pyriform aperture stenosis; our experience of 34 cases.

To study our population of patients with congenital nasal pyriform aperture stenosis (CNPAS) in terms of incidence and socioeconomic status; the effect of pyriform aperture size, gestational age, birth weight, and whether congenital abnormalities are associated with surgical requirement. Retrospective case note review of all patients treated for CNPAS at a single tertiary paediatric referral site was undertaken. Diagnosis was made on the basis of a pyriform aperture of <11mm on CT scanning; patient demographics were collected to explore risk factors for surgery and surgical outcomes. 34 patients were included in the series, 28 (84%) of whom underwent surgery. 58.8% of subjects had an associated mega central incisor. A smaller pyriform aperture size was seen in neonates requiring surgery (4.87mm±1.24mm vs 6.55mm±1.41mm, p=0.031). There was no difference in gestational age in neonates requiring surgery (p=0.074). Requirement for surgery was not associated with co-existing congenital anomalies (p=0.297) or lower birth weight (p=0.859). Low socioeconomic status was not significantly associated with requiring surgery but a potential link between CNPAS and deprivation was identified (p=0.0583). These results suggest that a pyriform aperture of less than 6mm requires surgical intervention. Associated birth anomalies add additional management considerations but in this cohort were not associated with increased need for surgery. A potential association between CNPAS and low socioeconomic status was identified.

Impact of Dimensions, Apertures and Terminals on Stray Inductance of the Laminated Busbar

This paper presents a systematic investigation of the impact of physical parameters such as dimensions, apertures and terminals, on the busbar inductance. A planar laminated busbar with copper conductors and a polyamide insulator is studied using a 3D FEM (Finite Element Modelling) based simulation software. The impact of dimensions such as conductor length, width and thickness, depth of insulator, the effects of aperture number, size, position and connection terminals on the busbar inductance are examined. The magnetic flux density, current density involved and its dependence on the self and mutual inductance of the laminated busbar is analyzed. Laminated busbars provided lower inductance with decreased conductor length, thickness, aperture diameter and depth of insulator. Also, the increased width of the busbar is of the essence for the design of a low inductance busbar. Low inductance laminated busbars are highly beneficial in power converters, powertrain inverters in electric vehicles, photovoltaic converters.

Investigation of the Effects of Anode Geometry on the Electrochemical Degradation of Ni-Ethylenediaminetetraacetic Acid Complexes Using Computational Fluid Dynamics Simulation

Anodic oxidation is a viable technology for the degradation of contaminants such as Ni-ethylenediaminetetraacetic acid (Ni-EDTA) complexes which are commonly found in wastewaters from the electroless plating industry. In an anodic oxidation process, the convective transport of the contaminant to the anode, which is affected by the hydrodynamic characteristics of the reactor and geometry of the electrodes, is crucial to the overall contaminant removal efficiency. In this work, a three-dimensional computational fluid dynamics (CFD) model was successfully developed to investigate flow behavior and its impact on the concentration profiles of Ni-EDTA complexes in a flow-through reactor during anodic oxidation of a synthetic wastewater containing these complexes. The CFD model was used to investigate the effect of electrode aperture size and shape on Ni-EDTA degradation with both simulation and experimental results indicating that, for the investigated system, the reduction of electrode aperture size enhanced the Ni-EDTA degradation rate by up to 1.4 times due to the increased rate of Ni-EDTA mass transfer to the electrode surface. A woven electrode exhibited the highest rate of Ni-EDTA degradation of the different anodes examined with the good performance in this case attributed particularly to the much more uniform Ni-EDTA concentration distribution and surface shear stress on the electrode surface. The CFD model developed in this study provided insights into the effect of electrode aperture geometry on mass transfer and subsequent contaminant removal efficiency and can be used more broadly for the optimization of anode design and reactor operation in electrochemical advanced oxidation processes.

Receiver aperture and multipath effects on power loss and modal crosstalk in a THz wireless link using orbital-angular-momentum multiplexing

The channel capacity of terahertz (THz) wireless communications can be increased by multiplexing multiple orthogonal data-carrying orbital-angular-momentum (OAM) beams. In THz links using OAM multiplexing (e.g., Laguerre-Gaussian {mathrm{LG}}_{ ell,p} beams with p = 0), the system performance might degrade due to limited receiver aperture size and multipath effects. A limited-size aperture can truncate the received beam profile along the radial direction. In addition, due to beam divergence, part of the beam might interact with reflectors in the environment, causing the signal to reflect and interfere at the receiver with the directly propagating part of the beam; this is known as the multipath effect. In this paper, we simulate and analyze the impact of both effects on the equality of the THz OAM link by considering a full two-dimensional (2-D) LG modal set. The simulation results show (i) a limited-size receiver aperture can induce power loss and modal power coupling mainly to LG modes with the same ℓ but p > 0 for directly propagated OAM beams; (ii) the multipath effect can induce modal power coupling across multiple 2-D LG modes, which leads to inter-channel coupling among the different channels in an OAM multiplexed link; (iii) the interference between the reflected and direct beams can induce intra-channel coupling between the received signals from the reflected and direct beams; and (iv) beams with a higher OAM order (e.g., from ± 1 to ± 5) or a lower carrier frequency (e.g., from 0.1 to 1 THz) experience larger intra- and inter-channel coupling. The intra- and inter-channel coupling in an OAM-multiplexed THz link can degrade the signal-to-noise ratio (SNR) and induce SNR penalty when compared to a single-channel system.

Geogrid-soil interaction: experimental analysis of factors influencing load transfer

This paper presents interaction experiments with transparent soil to investigate the load transfer at the interface of different geosynthetic reinforcements. Microscopic interaction performance was evaluated in terms of mobilised tensile loads and interfacial shear stresses resulting from the relative movement between geosynthetic and soil. The effects of geogrid aperture size, tensile stiffness, geogrid type and reinforcement configurations on the load transfer were analysed. It was found that with increasing soil deformation, the contribution of friction to the total load transfer decreased and the transverse ribs were increasingly activated. The interfacial shear stresses were reduced as the ratio of geogrid aperture to mean particle size increased, resulting in lower geogrid loads. Higher geogrid loads were mobilised with increasing tensile stiffness of the reinforcement, but lower displacements of geogrid and adjacent soil occurred. Consistent results were found for woven PET and laid PP geogrids. The most effective load transfer was obtained for the aperture configuration with two closely spaced transverse members at each rib, as the soil particles were additionally confined. When the geogrid was attached to a nonwoven geotextile, the separation function was enabled, but the reinforcement performance of the geocomposite was lower due to reduced particle-aperture interaction.

Experimental investigation of shear strength parameters of ballast encased with geogrid

So far, significant studies have been performed to increase the shear strength (τ) of ballast by reinforcing it with geogrid, though ballast encasement with geogrid, which could provide substantial confining pressure, has not yet been considered. Therefore, in this study, using a large-scale direct shear apparatus, effect of encasement of ballast with geogrid on shear behavior were investigated. For this purpose, two groups of ballast with average particle size (D50); 41.31 mm and 31.55 mm, and three types of biaxial geogrids GP35/35, GP40/20, and GP60/20, were considered. These two sets of experiments were carried out under normal stresses (σn) of 50, 100, and 150 kPa and with a shear rate of 1 mm/min. Experimental results showed that in the non-encased case, τ was affected by nominal maximum particle size (Dmax), uniformity coefficient (Cu) as well as the applied σn. According to the results σn was increased ​​from 50 to 150 kPa, the internal friction angle (φ) for group 1 decreased from 65.56° to 54.39° and for group 4 it decreased from 63.90° to 52.16°. Similarly, for the above-mentioned gradation groups, the dilation angle (ψ) decreased by 16.69% and 12.85% on average for all σn s, respectively. On the other hand, ballast encasement with geogrid improved its shear behavior, as for gradation group 1, the maximum effect of encasing on the φ corresponding to σn alteration from 50 to150 kPa was 74.5° for group 1 and 68.96° for group 4. While, the maximum reduction in ψ was 32.22% on average under these conditions, moreover for ballast group 4, the mentioned changes were 30.13%, 14.67%, and 27.86%, respectively. Also, in this study, the efficiency factor (α), varied in the range of 1.11–1.91. The effect of geogrid aperture size (A) on τ of encased ballast was investigated, too.

A Mechanically Rollable Reflectarray With Beam-Scanning Capabilities

A novel 1-D beam-steerable reflectarray antenna (RA) is proposed for the Ku-band. The RA aperture consists of 24×48 variable size square patch elements printed on a flexible plastic substrate. The aperture is wrapped around two cylinders to create a 12λ×12λ illumination window at the operating frequency of 14 GHz. Beam-steering is achieved by mechanically rolling the aperture. To mitigate antenna pattern degradation, an aperture phase distribution optimization technique is presented. The performance of this RA system is studied analytically using array theory. The effects of aperture size and unit-cell size are also discussed. The performance of the proposed RA is validated using simulations and measurements. The results illustrate that our design achieves 1-D beam-steering from -21∘ to +21∘ in the elevation plane while maintaining towards the broadside direction a maximum realized gain of 25.1 dBi. In this beam-scanning range, the gain variation is less than 1.5 dB, beamwidth variation is less than 1.6∘, and the side lobe level is maintained below -15 dB. In summary, the main advantage of our design is its ability to steer its high gain beam without using complicated feed networks or complex mechanical systems. Such antennas are especially needed in SmallSat and space applications.

Multicolor Patterning of 2D Semiconductor Nanoplatelets.

Nanocrystal micro/nanoarrays with multiplexed functionalities are of broad interest in the field of nanophotonics, cellular dynamics, and biosensing due to their tunable electrical and optical properties. This work focuses on the multicolor patterning of two-dimensional nanoplatelets (NPLs) via two sequential self-assembly and direct electron-beam lithography steps. By using scanning electron microscopy, atomic force microscopy, and fluorescence microscopy, we demonstrate the successful fabrication of fluorescent nanoarrays with a thickness of only two or three monolayers (7-11 nm) and a feature line width of ∼40 nm, which is three to four NPLs wide. To this end, first, large-area thin films of red-emitting CdSe/ZnyCd1-yS and green-emitting CdSe1-xSx/ZnyCd1-yS core/shell NPLs are fabricated based on Langmuir-type self-assembly at the liquid/air interface. By varying the concentration of ligands in the subphase, we investigate the effect of interaction potential on the film's final characteristics to prepare thin superlattices suitable for the patterning step. Equipped with the ability to fabricate a uniform superlattice with a controlled thickness, we next perform nanopatterning on a thin film of NPLs utilizing a direct electron-beam lithography (EBL) technique. The effect of acceleration voltage, aperture size, and e-beam dosage on the nanopattern's resolution and fidelity is investigated for both of the presented NPLs. After successfully optimizing EBL parameters to fabricate single-color nanopatterns, we finally focus on fabricating multicolor patterns. The obtained micro/nanoarrays provide us with an innovative experimental platform to investigate biological interactions as well as Förster resonance energy transfer.

Effect of Aperture Size on the Performance of Bamboo Mat Reinforced Soil Bed

ABSTRACT Soil reinforcement using natural materials has become popular due to the concern over the environmental issues associated with geosynthetics. Bamboo is one of the fine materials used as soil reinforcement in different forms. This paper investigates the efficacy of bamboo mats with different aperture sizes for soil reinforcement. In India, handwoven mats are utilized from ancient times onwards for various households and other applications. Bamboo mats with rectangular weaving patterns with and without aperture were used for the study. The aperture sizes are expressed in terms of the width of each strip in the bamboo mat (w). The bamboo mat with a square aperture of 0.5 w × 0.5 w, 1 w × 1 w, 2 w × 2 w, 3 w × 3 w and 4 w × 4 w were used for the study. Series of laboratory model tests were performed to assess the performance of bamboo mat reinforced soil bed. The test results show that the inclusion of bamboo mat improves the bearing capacity and reduces footing settlement. The effect of aperture size on the performance of bamboo mat reinforced soil is studied in detail and the results are presented in the paper. The formation of surface heave is considerably reduced and heave reduction factors for different mat types are also reported.

Heat Dissipation Performance of Micro-channel Heat Sink with Various Protrusion Designs

This research will focus on studying the effect of aperture size and shape of the micro-channel heat sink on heat dissipation performance for chip cooling. The micro-channel heat sink is considered to be a porous medium with fluid subject inter-facial convection. Derivation based on energy equation gives a set of governing partial differential equations describing the heat transfer through the micro-channels. Numerical simulation, including steady-state thermal analysis based on CFD software, is used to create a finite element solver to tackle the derived partial differential equations with properly defined boundary conditions related to temperature. After simulating three types of heat sinks with various protrusion designs including micro-channels fins, curly micro-channels fins, and Micro-pin fins, the result shows that the heat sink with the maximum contact area per unit volume will have the best heat dissipation performance, we will interpret the result by using the volume averaging theorem on the porous medium model of the heat sink.

Polarimetric Synthetic Aperture Radar Imaging With Radially Polarized Antennas

A polarimetric 3-D synthetic aperture radar (SAR) imaging method using a radially polarized antenna is described. The advantages of the radially polarized antenna, mainly that polarimetric SAR imaging can be performed without requiring additional measurements compared to traditional SAR, are discussed. A general target model is developed that includes information about target orientation and degree of polarization (i.e., how well and in what direction the target polarizes a signal). Image reconstruction algorithms were developed to allow polarimetric imaging to be performed with radially polarized antenna imaging data, enabling the estimation of target orientation and degree of polarization. The effect of scan step size and scan aperture size is studied on the accuracy of the estimation of these parameters, and guidelines were established as to the proper step size and scan aperture size to be used to keep estimation error below a specific threshold. Subsequently, a radially polarized antenna was designed, fabricated, and used to image several samples containing various types of point targets, by which the capability of this technique to enable accurate estimation of target orientation and degree of polarization is successfully demonstrated.

Study the effect of changing aperture size on linear and nonlinear properties of wheat germ oil

Thespectroscopic and nonlinearproperties of wheat germ oil have been investigated. Two different sources of oil (weight 3.33gm),locally (Emad) and global (Hemani) were used in this work. Theabsorption and fluorescence spectra of the two types of oil were carried out to calculate thequantum efficiencyof them. Nonlinear characteristics were measured by z-scan. The results showed that high quantum efficiency (91.5 for the local oil and 76.6 for the other) As for the non-linear properties, it was measured for wheat germ oil (Emad) by scanning technology (by changing the value of the closed hole (pin hole), the value of (n2) the non-linear refractive index changes with the size of the aperture (1, 1.5, 2, 2.5) mm.

Optimization of Slotted Liner in Rubiales Field: Trade-Off between Sand Control, Flow Performance, and Plugging Tendency

SummaryDesigning and selecting the proper sand control mechanism for horizontal wells in unconsolidated heavy-oil reservoirs tend to be underlooked in some cases. Standalone completions pose some sand control challenges, which could jeopardize the oil production or even lead to critical problems. Massive sand production, screen/formation plugging, hot spots, and mechanical integrity failures are some of the well-known issues. This study attempts to optimize the slotted liner design for horizontal wells in a heavy-oil field in Colombia.A careful selection of representative core data was made to study the variation of sand particle-size distribution (PSD) within the development area. Reservoir fluid properties were analyzed. Based on PSD variation and current design criteria in the industry, several seamed slotted-liner configurations were proposed as an alternative completion for testing. Later, a series of large-scale sand retention tests (SRTs) were performed to assess the selected alternatives under typical field production conditions. The effects of aperture size and open-to-flow area were investigated to evaluate flow and sand control performance.This investigation started with a detailed study of the PSD, particle shape variation, and composition of fines in the development area. The PSD then classified into four distinct minor and major sand facies, ranging from medium to very coarse sand with different fines content. Further investigations have shown that current design is only suitable for a limited number of the PSDs, while the overall PSD classes indicate the requirement for wider slot aperture sizes. The results of the SRTs indicated that the flow performance of the screen is mainly controlled by the slot aperture. Choosing the optimized aperture size avoids unacceptable sanding even for the multiphase flow scenarios with gas. Results also indicated that by increasing the aperture size and application of the seamed slots for the studied formation, plugging could be mitigated.A comprehensive sand control design workflow for cold primary heavy-oil production in horizontal wells is presented in this work. The current study is one of the first that investigates and compares conventional straight slotted liners with seamed slotted liners at a larger scale for this field. Moreover, this study helps to better understand the effect of design parameters of seamed slotted liners on sand control, flow performance, and plugging tendency.

Effects of flow constriction on foamed viscous shear-thinning fluids downstream of a continuous multi rotor-stator foaming device

Foam flow through processing equipment can seriously affect the structure of the foam and its quality attributes. In the design of a foam formulation and its flow system, it is therefore important to consider the possible implications on the end-of-pipe structure of the foam to ensure preservation of product quality. We study the flow through a straight pipe with and without the presence of a narrow orifice plate and, hence, the dynamic stability of wet food relevant foams of fine texture and high static stability generated from complex formulations of viscous shear-thinning fluids in a continuous multi rotor-stator device. The effects of fluid formulation, gas-liquid ratio, rotor speed and constriction aperture size are investigated. Constricted foam flow can cause important transformations in the foam due to significant bubble coalescence and loss of air volume resulting in much coarser and much less stable foam. Increased surfactant content, liquid viscosity and rotor speed reduce bubble coalescence and help preserve foam structure. • A continuous multi rotor-stator device generates foam of fine and stable structure. • Foam flow through a constriction causes bubble coalescence and loss of air volume. • Constricted foam flow leads to coarser unstable foam. • The higher the local pressure drop the more severe the foam damage incurred. • Increased surfactant content, liquid viscosity and rotor speed help preserve foam.