High Flow Regions Research Articles

Адаптивный алгоритм оценки частоты вихреобразования в вихреакустических расходомерах

The article focuses on the development of vortex shedding frequency estimation algorithm. It shows the difficulties of the application of classical algorithms (moving average and median filtering) for whole measurement range of vortex sonic flowmeter. These algorithms are effective at the high flow region, where frequency of arrival of information about vortex frequency is high. However, at the low flow region where aforementioned frequency equals to tenths of hertz these algorithms are ineffective. A new adaptive algorithm is offered which can operate in a whole range of flowmeter measuring. It combines an ability to react immediately if a flow starts changing, and to provide stable measurements if the flow is stable. The simulation of the proposed algorithm is implemented and its advantages over the algorithms used in serial manufacture are shown. It is noted that the developed algorithm does not need in powerful computing facilities.

Anisotropic grid generation for dynamic simulation in heterogeneous hydrocarbon reservoirs

Coarsening from fine geological model to coarse dynamic model is one of the main practical stages in reservoir simulation process in order to minimize simulation run time. In order to preserve accuracy and minimize simulation run time simultaneously, non-uniform element distribution is required to capture dynamic interest and high-flow regions in heterogeneous porous media. In this paper, an automatic coarsening method has been developed to generate anisotropic unstructured mesh with high aspect ratio elements to minimize total number of elements in dynamic model. A high resolution indicator which is called Metric Indicator is generated based on permeability and well effect parameters. Metric Indicator guides the mesh generator to create elements with the desired size, shape and orientation. Single phase gas flow and two-phase gas-water flow equations in a heterogeneous porous media have been solved using Control Volume Finite Approximation (CVFA) method. The comparison between the simulation results of the proposed method in this study and fine-grid model as a reference model demonstrates that the presented method can obtain high accuracy results with the minimum number of elements and the minimum simulation run time.

Magnetic resonance temperature imaging-based quantification of blood flow-related energy losses.

This study presents a new approach for evaluating bioheat transfer equation (BHTE) models used in treatment planning, control and evaluation of all thermal therapies. First, 3D magnetic resonance temperature imaging (MRTI) data are used to quantify blood flow-related energy losses, including the effects of perfusion and convection. Second, this information is used to calculate parameters of a BHTE model: in this paper the widely used Pennes BHTE. As a self-consistency check, the BHTE parameters are utilized to predict the temperatures from which they were initially derived. The approach is evaluated with finite-difference simulations and implemented experimentally with focused ultrasound heating of an ex vivo porcine kidney perfused at 0, 20 and 40 ml/min (n = 4 each). The simulation results demonstrate accurate quantification of blood flow-related energy losses, except in regions of sharp blood flow discontinuities, where the transitions are spatially smoothed. The smoothed transitions propagate into estimates of the Pennes perfusion parameter but have limited effect on the accuracy of temperature predictions using these estimates. Longer acquisition time periods mitigate the effects of MRTI noise, but worsen the effect of flow discontinuities. For the no-flow kidney experiments the estimates of a uniform, constant Pennes perfusion parameter are approximately zero, and at 20 and 40 ml/min the average estimates increase with flow rate to 3.0 and 4.2 kg/m(3) /s, respectively. When Pennes perfusion parameter values are allowed to vary spatially, but remain temporally constant, BHTE temperature predictions are more accurate than when using spatially uniform, constant Pennes perfusion values, with reductions in RMSE values of up to 79%. Locations with large estimated perfusion values correspond to high flow regions of the kidney observed in T1 -weighted MR images. This novel, MRTI-based technique holds promise for improving understanding of thermal therapy biophysics and for evaluating biothermal models.

Mapping molecular differences and extracellular matrix gene expression in segmental outflow pathways of the human ocular trabecular meshwork.

Elevated intraocular pressure (IOP) is the primary risk factor for glaucoma, and lowering IOP remains the only effective treatment for glaucoma. The trabecular meshwork (TM) in the anterior chamber of the eye regulates IOP by generating resistance to aqueous humor outflow. Aqueous humor outflow is segmental, but molecular differences between high and low outflow regions of the TM are poorly understood. In this study, flow regions of the TM were characterized using fluorescent tracers and PCR arrays. Anterior segments from human donor eyes were perfused at physiological pressure in an ex vivo organ culture system. Fluorescently-labeled microspheres of various sizes were perfused into anterior segments to label flow regions. Actively perfused microspheres were segmentally distributed, whereas microspheres soaked passively into anterior segments uniformly labeled the TM and surrounding tissues with no apparent segmentation. Cell-tracker quantum dots (20 nm) were localized to the outer uveal and corneoscleral TM, whereas larger, modified microspheres (200 nm) localized throughout the TM layers and Schlemm’s canal. Distribution of fluorescent tracers demonstrated a variable labeling pattern on both a macro- and micro-scale. Quantitative PCR arrays allowed identification of a variety of extracellular matrix genes differentially expressed in high and low flow regions of the TM. Several collagen genes (COL16A1, COL4A2, COL6A1 and 2) and MMPs (1, 2, 3) were enriched in high, whereas COL15A1, and MMP16 were enriched in low flow regions. Matrix metalloproteinase activity was similar in high and low regions using a quantitative FRET peptide assay, whereas protein levels in tissues showed modest regional differences. These gene and protein differences across regions of the TM provide further evidence for a molecular basis of segmental flow routes within the aqueous outflow pathway. New insight into the molecular mechanisms of segmental aqueous outflow may aid in the design and delivery of improved treatments for glaucoma patients.

Flow-induced signal misallocation artifacts in two-point fat-water chemical shift MRI.

Two-point fat-water separation methods are increasingly being used for chest and abdominal MRI and have recently been introduced for use in MR angiography of the lower extremities. With these methods, flowing spins can accumulate unintended phase shifts between the echo times. The purpose of this study is to demonstrate that these phase shifts can lead to inaccurate signals in the water and fat images. In vitro experiments were conducted at 1.5T and 3.0T using a stenosis-mimicking phantom and a computer-controlled pump to image a range of physiologically relevant velocities. In the phantom images acquired using bipolar readout gradients, fat-water signal inaccuracies were visible in regions of flow, with increasing severity as the flow rate was increased. Additionally, similar effects were observed in regions of high flow in clinical chest and liver exams. In the phantom images, the effect was eliminated by using a dual-pass method without bipolar readout gradients. When using fat-water separation methods with bipolar readout gradients, phase shifts caused by the motion of spins can lead to signal inaccuracies in the fat and water images. These artifacts can be mitigated by using approaches that do not use bipolar readout gradients.

The hydraulic conductivity structure of gravel-dominated vadose zones within alluvial floodplains

The floodplains of many gravel-bed streams have a general stratigraphy that consists of a layer of topsoil covering gravel-dominated subsoil. Previous research has demonstrated that this stratigraphy can facilitate preferential groundwater flow through focused linear features, such as paleochannels, or gravelly regions within the vadose zone. These areas within the floodplain vadose zone may provide a route for interactions between the floodplain surface and alluvial groundwater, effectively extending the hyporheic zone across the floodplain during high stream stage. The objective of this research was to assess the structure and scale of texture heterogeneity within the vadose zone within the gravel subsoils of alluvial floodplains using resistivity data combined with hydraulic testing and sediment sampling of the vadose zone. Point-scale and broad-scale methodologies in combination can help us understand spatial heterogeneity in hydraulic conductivity without the need for a large number of invasive hydraulic tests. The evaluated sites in the Ozark region of the United States were selected due to previous investigations indicating that significant high conductivity flow zones existed in a matrix which include almost no clay content. Data indicated that resistivity corresponded with the fine content in the vadose zone and subsequently corresponds to the saturated hydraulic conductivity. Statistical analysis of resistivity data, and supported by data from the soil sampling and permeameter hydraulic testing, identified isolated high flow regions and zones that can be characterized as broad-scale high hydraulic conductivity features with potentially significant consequences for the migration of water and solutes and therefore are of biogeochemical and ecological significance.

Fluid-to-fluid scaling for convective heat transfer in tubes at supercritical and high subcritical pressures

Following a review of two recent sets of fluid-to-fluid scaling laws for supercritical heat transfer and a discussion of their possible limitations, we have proposed two additional sets of scaling laws, which take into account empirically adjustable versions of the Dittus–Boelter correlation and which are applicable to both the supercritical and the high subcritical flow regions. We have compiled a database of heat transfer measurements in carbon dioxide flowing upwards in vertical heated tubes that are free of deterioration or enhancement. We then applied the four sets of scaling laws to these data to compute values of the water-equivalent heat transfer coefficient and compared these values to predictions of a transcritical look-up table, which was earlier shown to represent well a large compilation of measurements in water at supercritical and high subcritical pressures. It was shown that the two earlier methods systematically overestimated the heat transfer coefficient in water and also introduced significant imprecision. In contrast, the two proposed methods of scaling introduce no bias and have lower precision uncertainties than those of the previous scaling methods.

North Cascadia heat flux and fluid flow from gas hydrates: Modeling 3‐D topographic effects

AbstractThe bottom‐simulating reflector (BSR) of gas hydrate is well imaged from two perpendicular seismic grids in the region of a large carbonate mound, informally called Cucumber Ridge off Vancouver Island. We use a new method to calculate 3‐D heat flow map from the BSR depths, in which we incorporate 3‐D topographic corrections after calibrated by the drilling results from nearby (Integrated) Ocean Drilling Program Site 889 and Site U1327. We then estimate the associated fluid flow by relating it to the topographically corrected heat flux anomalies. In the midslope region, a heat flux anomaly of 1 mW/m2 can be associated with an approximate focused fluid flow rate of 0.09 mm/yr. Around Cucumber Ridge, high rates of focused fluid flow were observed at steep slopes with values more than double the average regional diffusive fluid discharge rate of 0.56 mm/yr. As well, in some areas of relatively flat seafloor, the focused fluid flow rates still exceeded 0.5 mm/yr. On the seismic lines the regions of focused fluid flow were commonly associated with seismic blanking zones above the BSR and sometimes with strong reflectors below the BSR, indicating that the faults/fractures provide high‐permeability pathways for fluids to carry methane from BSR depths to the seafloor. These high fluid flow regions cover mostly the western portion of our area with gas hydrate concentration estimations of ~6% based on empirical correlations from Hydrate Ridge in south off Oregon, significantly higher than previously recognized values of ~2.5% in the eastern portion determined from Site U1327.

Augmenting the Structures in a Swirling Flame via Diffusive Injection

Small scale experimentation using particle image velocimetry investigated the effect of the diffusive injection of methane, air, and carbon dioxide on the coherent structures in a swirling flame. The interaction between the high momentum flow region (HMFR) and central recirculation zone (CRZ) of the flame is a potential cause of combustion induced vortex breakdown (CIVB) and occurs when the HMFR squeezes the CRZ, resulting in upstream propagation. The diffusive introduction of methane or carbon dioxide through a central injector increased the size and velocity of the CRZ relative to the HMFR whilst maintaining flame stability, reducing the likelihood of CIVB occurring. The diffusive injection of air had an opposing effect, reducing the size and velocity of the CRZ prior to eradicating it completely. This would also prevent combustion induced vortex breakdown CIVB occurring as a CRZ is fundamental to the process; however, without recirculation it would create an inherently unstable flame.

High flow conditions increase connexin43 expression in a rat arteriovenous and angioinductive loop model.

Gap junctions are involved in vascular growth and their expression pattern is modulated in response to hemodynamic conditions. They are clusters of intercellular channels formed by connexins (Cx) of which four subtypes are expressed in the cardiovascular system, namely Cx37, Cx40, Cx43 and Cx45. We hypothesize that high flow conditions affect vascular expression of Cx in vivo. To test this hypothesis, flow hemodynamics and subsequent changes in vascular expression of Cx were studied in an angioinductive rat arteriovenous (AV) loop model. Fifteen days after interposition of a femoral vein graft between femoral artery and vein encased in a fibrin-filled chamber strong neovascularization was evident that emerged predominantly from the graft. Blood flow through the grafted vessel was enhanced ∼4.5-fold accompanied by increased pulsatility exceeding arterial levels. Whereas Cx43 protein expression in the femoral vein is negligible at physiologic flow conditions as judged by immunostaining its expression was enhanced in the endothelium of the venous graft exposed to these hemodynamic changes for 5 days. This was most likely due to enhanced transcription since Cx43 mRNA increased likewise, whereas Cx37 mRNA expression remained unaffected and Cx40 mRNA was reduced. Although enhanced Cx43 expression in regions of high flow in vivo has already been demonstrated, the arteriovenous graft used in the present study provides a reliable model to verify an association between Cx43 expression and high flow conditions in vivo that was selective for this Cx. We conclude that enhancement of blood flow and its oscillation possibly associated with the transition from laminar to more turbulent flow induces Cx43 expression in a vein serving as an AV loop. It is tempting to speculate that this upregulation is involved in the vessel formation occuring in this model as Cx43 was suggested to be involved in angiogenesis.

Operating characteristics of a loop heat pipe-based isothermal region generator

An isothermal region of a finite size is an important requirement for precision metrology and its related industries. In this work, a loop heat pipe (LHP)-based isothermal region generator was devised in which a high speed vapor flow region of the LHP was utilized to achieve the isothermal region. To this end, a stainless steel LHP employing water as a working fluid was designed and fabricated. In particular, an annular type vapor flow region was configured in the vapor transport line to accommodate the isothermal region with dimensions of 50 mm×360mm (diameter×height). Temperature uniformity testing demonstrated that the maximum temperature difference and the effective thermal conductivity of the isothermal region at the maximum heat load were 0.56°C and 311 000W/(mK), respectively. The temperature uniformity improved with increasing mass flow rate and showed a dependence on the speed of the working fluid. The steady state operating temperature of the isothermal region ranged from 47.1°C to 64.0°C with temperature hysteresis at low heat loads. Details of the design and operating characteristics of the LHP-based isothermal region generator are provided and discussed.

Study on the effects of vegetation density in reducing bed shear stress on the downstream slope of earthen embankment

River bank, coastal erosion and embankment failures are endemic and recurrent natural hazards, causing loss of lands and livelihoods along major rivers and coastlines. Overflow is the most damaging factor for earthen embankments on the downstream (d/s) slope due to the erosion of surface material which is caused by the high bed shear stress and supercritical flow over the entire d/s slope. Vegetation planted on d/s slope may have a considerable effect in reducing bed shear stress which makes erosion. However,the influence of vegetation for flow resistance as well as bed shear stress control has been studied a little. Therefore, the aim of this research is to introduce the use of natural resources like vetiver grass for controlling bed shear stress which actually causes embankment erosion starts from the high flow region that is, in supercritical flow state. A small-scale experiment is performed with four different densities of vegetal cover considering different discharges on d/s slope. Vegetative barrier affect the mean flow rate by induced drag force against hydraulic forces. Hydraulic characteristics and mechanism of vegetation in open channel during overflow are studied through flume experiment. Results demonstrated that vegetation markedly reduced the effective bed shear stresses which are the influencing factor for causing erosion on the d/s slope, toe and bed of embankment. Results also revealed a significant reduction of damage due to erosion and risk of failure from overtopping flow can be achieved by providing dense vegetation cover on the d/s slope of earthen embankment. Key words: Embankment, downstream slope, drag force, bed shear stress, vegetation density.

Distribution of venous remodeling in exercise-induced pulmonary hemorrhage of horses follows reported blood flow distribution in the equine lung

Exercise-induced pulmonary hemorrhage (EIPH), which has been reported in humans and a variety of domestic animals following strenuous exercise, is most often documented in racehorses. Remodeling of pulmonary veins (VR) in equine EIPH was recently described, suggesting that it contributes to the pathogenesis of the disease. The cause of VR is unknown. We tested the hypothesis that the development of VR follows pulmonary blood flow distribution, preferentially occurring in the caudodorsal lung region. Furthermore, we hypothesized that VR underpins development of the other lesions of EIPH pathology. The lungs of 10 EIPH-affected horses and 8 controls were randomly sampled for histopathology (2,520 samples) and blindly scored for presence and severity of VR, hemosiderin (H), and interstitial fibrosis (IF). Mean sample score (MSS), mean lesion score, and percent samples with lesions were determined in four dorsal and three ventral lung regions, and the frequency, spatial distribution, and severity of lesions were determined. MSS for VR and H were significantly greater dorsally than ventrally (P < 0.001) and also decreased significantly in the caudocranial direction (P < 0.001). IF decreased only in the caudocranial direction. The percent samples with lesions followed the same distribution as MSS. VR often was accompanied by H; IF never occurred without VR and H. Similarity of the distribution of EIPH lesions and the reported fractal distribution of pulmonary blood flow suggests that VR develops in regions of high blood flow. Further experiments are necessary to determine whether VR is central to the pathogenesis of EIPH.

Effects of Number of Circumferential Casing Grooves on Stall Flow Characteristics of a Transonic Axial Compressor

This work investigates the effects of circumferential casing grooves on stall flow characteristics of a transonic axial compressor. Numerical analysis is conducted by solving three-dimensional steady Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. The results of flow analysis for an axial compressor with smooth casing are validated in comparison with experimental data for the pressure ratio and adiabatic efficiency. The numerical stall inception point is identified from the last converged point by convergence criteria, and the stall margin is predicted numerically. The peak adiabatic efficiency point is also obtained by reducing the normalized mass flow in the high mass flow region. In order to explore the influence of number of the circumferential casing grooves on the performance of the compressor, the stall margins and peak adiabatic efficiencies are evaluated compared to the case smooth casing. The stability of the axial compressor with circumferential casing grooves is found to be sensitively influenced by the number of grooves.

The stability of direct carbon fuel cells with molten Sb and Sb–Bi alloy anodes

The long‐term stability of direct carbon fuel cells, based on solid oxide fuel cells with molten Sb and Sb–Bi anodes, was examined for operation with activated charcoal, rice starch, and bio‐oil fuels at 973 K. With intermittent stirring of the fuel–metal anode interface, the anode performance was stable, and reasonable power densities (∼250 mW/cm2) were achieved for periods up to 250 h. With Sc‐stabilized zirconia, severe thinning of the electrolyte occurred in regions of high current flow. No electrolyte thinning was observed with yttria‐stabilized zirconia as the electrolyte operating at the same current densities. © 2012 American Institute of Chemical Engineers AIChE J, 59: 3342–3348, 2013

Comparative Study of Gasification Performance between Bituminous Coal and Petroleum Coke in the Industrial Opposed Multiburner Entrained Flow Gasifier

A comprehensive three-dimensional numerical model for simulating Shenfu bituminous coal and petroleum coke in the industrial opposed multiburner (OMB) gasifier is established. The “effectiveness factor” method is used to extrapolate the intrinsic char reactivity data to industrial gasifier conditions. With the proposed models, the predicted gasification performance of Shenfu coal is in good agreement with industrial operating data, and the predicted carbon conversion of petroleum coke is about 96.7%. Comparing with Shenfu coal, the specific solid fuel consumption of petroleum coke is lower, while the specific oxygen consumption is higher. The characteristic of char gasification in the entrained flow gasifier is investigated. In the high temperature jet flow region and impinging flow region, when the particle diameter is above 200 μm, the Thiele modulus of the char gasifying with steam for Shenfu coal and petroleum coke are 15.4 and 4.8, respectively. Therefore, pore diffusion has a significant effect on the apparent char reactivity. While for the char gasifying with CO2, the Thiele modulus is below 5 in different regions of the OMB gasifier, and the apparent char reactivity is affected by the chemical reaction and pore diffusion. When the char reactivity of petroleum coke is accelerated at 5 times by catalysis effects, the carbon conversion reaches 99.2% and the consumption of oxygen and feedstock decrease obviously. Importantly, the temperature at the dome of the gasifier decreases to 1345 °C, which prolongs the life of refractory wall and favors a long period of availability for the gasifier.

Mapping the ECG in the live rabbit heart using Ultrasound Current Source Density Imaging with coded excitation.

Ultrasound current source density imaging (UCSDI) is a noninvasive technique for mapping electric current fields in 4D (space + time) with the resolution of ultrasound imaging. This approach can potentially overcome limitations of conventional electrical mapping procedures often used during treatment of cardiac arrhythmia or epilepsy. However, at physiologic currents, the detected acoustoelectric (AE) interaction signal in tissue is very weak. In this work, we evaluated coded ultrasound excitation (chirps) for improving the sensitivity of UCSDI for mapping the electrocardiogram (ECG) in a live rabbit heart preparation. Results confirmed that chirps improved detection of the AE signal by as much as 6.1 dB compared to a square pulse. We further demonstrated mapping the ECG using a clinical intracardiac catheter, 1 MHz ultrasound transducer and coded excitation. B-mode pulse echo and UCSDI revealed regions of high current flow in the heart wall during the peak of the ECG. These improvements to UCSDI are important steps towards translation of this new technology to the clinic for rapidly mapping the cardiac activation wave.

SIRT of liver metastases: physiological and pathophysiological considerations

Available literature on the differences in circulation and microcirculation of normal liver and liver metastases as well as in rheology of the different radiolabelled microspheres [(99m)Tc-labelled macroaggregates of albumin (MAA), (90)Y-TheraSpheres and (90)Y-SIR-spheres] used in selective internal radiation therapy (SIRT) are reviewed and implications thereof on the practice of SIRT discussed. As a result of axial accumulation and skimming, large microspheres are preferentially deposited in regions of high flow, whereas smaller microspheres are preferentially diverted to regions of low flow. As flow to normal liver tissue is considerably variable between segments and also within one segment, microspheres will be delivered heterogeneously within the microvasculature of normal liver tissue. This non-uniformity in microsphere distribution in normal liver tissue has a significant "liver-sparing" effect on the dose distribution of (90)Y-labelled microspheres. Arterial flow to liver metastases is most pronounced in the hypervascular rim of metastases, followed by the smaller metastases and finally by the central hypoperfused region of the larger metastases. Because of the wide variability in size of labelled MAAs and because of the skimming effect, existing differences in flow between metastatic lesions of variable size are likely exaggerated on (99m)Tc-MAA scintigraphy when compared to (90)Y-TheraSpheres and (90)Y-SIR-spheres (smaller variability in size and probably also in specific activity). Ideally, labelled MAAs would contain a size range similar to that of (90)Y-SIR-spheres or (90)Y-TheraSpheres. Furthermore, the optimal number of MAA particles to inject for the pretreatment planning scintigraphy warrants further exploration as it was shown that concentrated suspensions of microspheres produce more optimal tumour to normal liver distribution ratios. Finally, available data suggest that the flow-based heterogeneous distribution of microspheres to metastatic lesions of variable size might be optimized, that is rendered more homogeneous, through the combined use of angiotensin II and degradable starch microspheres.

Measurement of pollen clump release and breakup in the vicinity of ragweed (A. confertiflora) staminate flowers

Pollen dispersal is fundamental in a plant's reproductive ecology and as a result of fragmentation of the landscape, questions have been raised on how isolated plant populations can still exchange genetic information. A common mechanism for gene exchange is wind pollination (anemophily). A successful anemophilous species native to North America is ragweed (Ambrosia), a weed that is hard to eradicate after it takes root on crop fields and its pollen causes very strong allergenic effects (hay fever). Despite the extremely clumpy nature of ragweed pollen that should limit its long distance dispersal, ragweed has spread rapidly across the world during the last century while maintaining a high genetic diversity. One of the reasons for its success may be prolific pollen production as well as an efficient pollen clump release and breakup mechanism. Efficient pollen entrainment and dispersal into the atmosphere is highly influenced by flow field characteristics as pollen released into the atmosphere initially encounters flow structures created by the plant's morphology. Here, the flow field in the wake of a mature ragweed spike having multiple staminate flowers as well as pollen release was studied using Particle Image Velocimetry and high-speed, inline holographic cinematography. The latter enabled to track the pollen in a 3D volume. The spike was set up in a wind tunnel and exposed to wind speeds ranging from 1 to 2 m/s. Results indicated that ragweed pollen was released in multiple sized clumps containing tens to several thousand single grains. Clumps were both “pulled apart” at the point of entrainment while exiting the flowers as well as broke up in smaller sized clumps in high shear rate flow regions not far from the spike. In addition, the largest clumps that did not travel far, deposited in the vicinity of the spike, breaking apart into many small clumps upon deposition. Based on our results, initial release and dispersal of ragweed pollen clumps is characterized by three concomitant mechanisms of clump breakup occurring at entrainment, in mid-air and on deposition, which make it perfectly suited to disperse pollen over a wide range of spatial scales.

The benefits of planar circular mouths on suction feeding performance

Suction feeding is the most common form of prey capture across aquatic feeding vertebrates and many adaptations that enhance efficiency and performance are expected. Many suction feeders have mechanisms that allow the mouth to form a planar and near-circular opening that is believed to have beneficial hydrodynamic effects. We explore the effects of the flattened and circular mouth opening through computational fluid dynamics simulations that allow comparisons with other mouth profiles. Compared to mouths with lateral notches, we find that the planar mouth opening results in higher flow rates into the mouth and a region of highest flow that is positioned at the centre of the mouth aperture. Planar mouths provide not only for better total fluid flow rates through the mouth but also through the centre of the mouth near where suction feeders position their prey. Circular mouths are shown to provide the quickest capture times for spherical and elliptical prey because they expose the prey item to a large region of high flow. Planar and circular mouths result in higher flow velocities with peak flow located at the centre of the mouth opening and they maximize the capacity of the suction feeders to exert hydrodynamic forces on the prey.