Wide Range Of Flow Rates Research Articles

Microhemodynamic parameters quantification from intravital microscopy videos

Blood flow and blood–endothelium interactions correspond with the genesis of cardiovascular diseases. Therefore, quantitative analysis of blood flow dynamics at the microcirculation level is of special interest. Regulatory mechanisms mediated by blow flow have been studied in detail using in vitro approaches. However, these mechanisms have not been fully validated in vivo due to technical limitations that arise when quantifying microhemodynamics with the required level of detail. Intravital microscopy combined with high-speed video recordings has been used for the analysis of blood flow in small blood vessels of chronic and acute experimental tissue preparations. This tool can be used to study the interaction between the flowing blood and the vessel walls of arterioles and venules with sufficient temporal and spatial resolution. Our objective was to develop a simple and robust cross-correlation algorithm for the automatic analysis of high-speed video recordings of microcirculatory blood flow. The algorithm was validated using in vitro and in vivo systems. Results indicate that the algorithm's ability to estimate the velocity of local red blood cells as a function of blood vessel radius is highly accurate. They thereby suggest that the algorithm could be used to explore dynamic changes in blood flow under different experimental conditions including a wide range of flow rates and hematocrit levels. The algorithm can also be used to measure volumetric flow rates, radial velocity profiles, wall shear rate, and wall shear stress. Several applications are presently explored, including the analysis of velocity profiles in the branches of arterial bifurcations. This work demonstrates the robustness of the cross-correlation technique in various flow conditions and elucidates its potential application for in vivo determination of blood flow dynamics in the microcirculation.

Mathematical modeling of flow discharge over compound sharp-crested weirs

Water measurements play a pivotal role in hydraulic and environmental management of river systems, irrigation and drainage networks, and sewer conduits. Due to effective limitations of simple sharp crested weirs, recently compound sharp crested weirs have attracted great attention of civil engineers. With this type of weir, flow discharge is measured with a reasonable sensitivity over a wide range of flow rates. In this paper, the Shiono and Knight (SKM) quasi 2-D mathematical model has been numerically solved for discharge prediction of compound weirs, based on the assumption of flow similarity between compound sharp crested weirs and compound open channels. The modeled results are compared with the experimental data and the conventional method (linear combination of theoretical equations of simple weirs). The comparisons revealed that the proposed method shows improved discharge calculation within 3.8 percent absolute mean error while the traditional method has more than 12.5 percent error.

Numerical investigation of base-setting of stator’s stagger angles for a 15-stage axial-flow compressor

A 15-stage axial-flow compressor utilized in steel industry was studied in this paper. All the stator’s stagger angles of the compressor are variable to ensure the multistage compressor operate effectively within a wide range of flow rate and meanwhile satisfy the demand for sufficient pressure ratio, adiabatic efficiency and stall margin. Three in all different base-settings of stator’s stagger angles were presented and commercial CFD software was applied to obtain the overall performance characteristics. The results showed that both of the optimized base-settings improved the performances both in summer and winter conditions, although the adiabatic efficiency was somewhat decreased. Taking incidence angle and stage loading into consideration, differences among the three cases were analyzed in detail. On the basis of numerical computations, the performance could be effectively improved through adjusting the base-setting of stator’s stagger angles.

Highly Flexible Hot Gas Generation System for Turbocharger Testing

The paper presents the design and prototyping of a gas generator system for turbocharger experimental testing capable of delivering a wide range of flow rates with adequate thermodynamic characteristics. The system feeds the turbocharger test section with an hot gas stream of prescribed mean and time varying pressure and temperature in order to fully span the operating domain of the device with controlled accuracy. Compared with the more conventional gas combustor system, it allows for a safer rig operation ensured by the structural robustness of a four stroke diesel engine and an easier turbine inlet flow control. The latter is achieved by means of an external supercharging station and a modern ICE electronic control unit so that mass flow rate, pressure and temperature values can be set independently.The steady compressor and turbine performance maps can be obtained operating the rig according to a conventional procedure, i.e. collecting a set of flow rate pressure ratio data points (mg, π) for given hot gas properties. Alternatively using more advanced operating modes unsteady testing is possible to reproduce the complexities characterizing the driving cycles required by the latest European regulations.

Experimental and numerical analysis of unsteady behaviour of high efficiency mixed-flow pump

This work deals with the experimental and numerical investigation of cavitating and noncavitating flow inside a mixed-flow pump and its influence on performance curves of this pump. The experimental research has been carried out in the closed horizontal loop with the main tank capacity of 35 m 3 . The loop is equipped with both the compressor and the vacuum pump capable of creating different pressure levels while maintaining constant volume flow rate. Pump investigated in this project has been equipped with transparent windows, which enabled the visualization of flow and cavitation phenomena for a wide range of flow conditions. A comprehensive CFD analysis of tested pump has been done both in the cavitating and noncavitating regimes. The ANSYS CFX commercial CFD package has been used to solve URANS equations together with the Rayleigh-Plesset model and the SST-SAS turbulence model. Both the experimental research and the CFD analysis have provided a good illustration of the flow structures inside the pump and their dynamics for a wide range of flow rates and NPSH values. Flow and cavitation instabilities have been detected at suboptimal flow rates which correspond to increased values of noise and vibrations. The calculated results agree well with the measurements.

Pumps used as turbines power recovery, energy efficiency, CFD analysis

As the global demand for energy grows, numerous studies in the field of energy efficiency are stimulated, and one of them is certainly the use of pumps in turbine operating mode. In order to reduce time necessary to determine pump characteristic in turbine operating mode problem was studied by computational fluid dynamics approach. The paper describes various problems faced during modeling (pump and turbine mode) and the approaches used to resolve the problems. Since in the majority of applications, the turbine is a pump running in reverse, many attempts have been made to predict the turbine performance from the known pump performance, but only for best efficiency point. This approach does not provide reliable data for the design of the system with maximum energy efficiency and does not allow the determination of the head for a wide range of flow rates. This paper presents an example of centrifugal norm pump operating in both (pump and turbine) regime and comparison of experimentally obtained results and computational fluid dynamics simulations.

Design and validation of a uniform flow microreactor

We present a design method to characterize uniform flows in a microreactor for high performance surface plasmon resonance (SPR) a general-purpose biosensor chips. The shape of the microreactor is designed based on an approximate pressure drop model. The number of micro-pillars and the slopes of the inlet and outlet linear chambers are two dominant parameters used to minimize the velocity difference in the microreactor. The flow uniformity was examined quantitatively by numerical and experimental visualization methods. A computational fluid dynamics (CFD) analysis demonstrates that the designed microreactor has a fairly uniform velocity profile in the reaction zone for a wide range of flow rates. The velocity field in the fabricated microreactor was measured using the micro-particle image velocimetry (μ-PIV) method, and the flow uniformity was confirmed experimentally. The performance of the uniform flow microreactor was verified using the fluorescence antibody technique.

Multi-Regime Shape Optimization of Fan Vanes for Energy Conversion Efficiency using CFD, 3D Optical Scanning and Parameterization

An enhanced reverse engineering procedure was developed for roof fan re-design. An original numerical workflow for robust shape optimization based on maximum energy conversion efficiency was developed. It operates using a sample of multiple operating regimes coupled with CFD simulations. The initial shape solution was originally obtained in point cloud form by optical 3D scanning and subsequent B-spline based parameterization of shape. The CFD simulation of the scanned shape using 3D RANS based software was shown to agree very well with the measured features, experimentally obtained in our lab with the actual initial-shape fan. By manipulating the control points of parametric curves, the developed evolutionary optimization workflow was subsequently able to create shape-optimized vanes. This original procedure was applied to cases of constant-thickness and profiled single curvature vanes, both for single-regime and robust multi-point operating conditions. The corresponding increase in efficiency gained by our computational procedure was correlated with respective velocity and pressure distributions and suppression of flow separation. The novel numerical procedure developed here therefore provides a numerical framework for generic object geometry to re-shape itself autonomously. The change in shape ensures maximum energy conversion efficiency for a given composition of operating regimes. The gain in efficiency with optimized vane shapes proves to be significant in the wide range of flow rates around the best efficiency point.

Rational selection of substrates to improve color intensity and uniformity on microfluidic paper-based analytical devices.

A systematic investigation was conducted to study the effect of paper type on the analytical performance of a series of microfluidic paper-based analytical devices (μPADs) fabricated using a CO2 laser engraver. Samples included three different grades of Whatman chromatography paper, and three grades of Whatman filter paper. According to the data collected and the characterization performed, different papers offer a wide range of flow rate, thickness, and pore size. After optimizing the channel widths on the μPAD, the focus of this study was directed towards the color intensity and color uniformity formed during a colorimetric enzymatic reaction. According to the results herein described, the type of paper and the volume of reagents dispensed in each detection zone can determine the color intensity and uniformity. Therefore, the objective of this communication is to provide rational guidelines for the selection of paper substrates for the fabrication of μPADs.

WGC Based Robust and Gain Scheduling PI Controller Design for Condensing Boilers

This paper addresses the water temperature PI control in condensing domestic boilers. The main challenge of this process under the controller design perspective is the fact that the dynamics of condensing boilers are strongly affected by the demanded water flow rate. First, a robust PI controller based on weighted geometrical center method is designed that stabilizes and achieves good performance for closed-loop system for a wide range of the water flow rate. Then, it is shown that if the water flow rate information is used to update the controller gains, through a technique known as gain scheduled control, the performance can be significantly improved. Important characteristics of these PI design approaches are that the resulting parameters are calculated numerically without using any graphical method or iterative optimization process and that it guarantees the stability of the closed-loop. Significantly, simulation results have demonstrated that the proposed tuning techniques can perform better for set point changes and load disturbance than other available methods in the literature.

Formation and dynamics of partially wetting droplets in square microchannels

Droplet motion and dynamic wetting transitions are experimentally investigated over a wide range of viscosities and flow rates in square microchannels

Standing surface acoustic wave (SSAW)-based microfluidic cytometer.

The development of microfluidic chip-based cytometers has become an important area due to their advantages of compact size and low cost. Herein, we demonstrate a sheathless microfluidic cytometer which integrates a standing surface acoustic wave (SSAW)-based microdevice capable of 3D particle/cell focusing with a laser-induced fluorescence (LIF) detection system. Using SSAW, our microfluidic cytometer was able to continuously focus microparticles/cells at the pressure node inside a microchannel. Flow cytometry was successfully demonstrated using this system with a coefficient of variation (CV) of less than 10% at a throughput of ~1000 events s(-1) when calibration beads were used. We also demonstrated that fluorescently labeled human promyelocytic leukemia cells (HL-60) could be effectively focused and detected with our SSAW-based system. This SSAW-based microfluidic cytometer did not require any sheath flows or complex structures, and it allowed for simple operation over a wide range of sample flow rates. Moreover, with the gentle, bio-compatible nature of low-power surface acoustic waves, this technique is expected to be able to preserve the integrity of cells and other bioparticles.

Characteristics of a micro-hydro turbine

Computational Fluid Dynamics, a crucial tool in exploring designs of hydraulic machinery, is used to evaluate the design of a non-uniform Archimedean spiral rotor. A transient simulation method is implemented using a frame of reference change between time-steps to capture the flow field correctly. The boundary conditions for this method are discussed and are validated with previously published experimental data using a flat plate propeller turbine. A spectral and temporal convergence study for the non-uniform Archimedean spiral rotor is performed to verify solution independence of mesh and time-step selection. Performance characteristics of the rotor are provided over a wide range of volumetric flow rates and rotation rates. The best hydraulic efficiency point is determined to be 72% for the presented rotor design and is compared with the performance of similar micro-hydro turbines.

Investigation of the mobile granular layer in bedload transport by laminar shearing flows

AbstractThe mobile layer of a granular bed composed of spherical particles is experimentally investigated in a laminar rectangular channel flow. Both particle and fluid velocity profiles are obtained using particle image velocimetry for different index-matched combinations of particles and fluid and for a wide range of fluid flow rates above incipient motion. A full three-dimensional investigation of the flow field inside the mobile layer is also provided. These experimental observations are compared to the predictions of a two-phase continuum model having a frictional rheology to describe particle–particle interactions. Different rheological constitutive laws having increasing degrees of sophistication are tested and discussed.

A wearable intravenous infusion device facilitating ambulation: a pre-clinical report

A wearable ambulatory intravenous infusion device (AIVD) has been developed to facilitate the ambulation of patients. To enhance ambulation, a wearable AIVD was designed and a prototype was developed that consists of an air bag, a reciprocating air pump, a drip rate sensor, and a microprocessor-based controller. Using air pressure as a source for actuation greatly contributes to decreasing the weight of the proposed device and the power consumption. Experimental results show that the proposed infusion device can provide a variety of flow rates ranging from 36–90 mL h−1 with less than a 10% error. A series of experiments were performed with the prototype of the proposed device at a wide range of flow rates and the results verify that the accuracy and controllability of the prototype is comparable with those of the current intravenous infusion devices available. It is expected that the AIVD significantly contributes to the early recovery of patients by offering a convenient and cost-effective means of ambulation.

A Microfluidic Device with 3-D Hydrogel Villi Scaffold to Simulate Intestinal Absorption

The absorption of drugs via oral route is a subject of a great interest in drug development process. The current in vitro method for measuring the kinetics of drug absorption relies on 2-D monolayer culture of Caco-2 cells on a porous membrane, but physiologically unrealistic environment provided by this method often results in inaccurate drug absorption kinetics. Here we report a novel microfluidic system which better mimics the physiological environment of the human small intestine. Three dimensional geometries of villi of the small intestine were reproduced via novel hydrogel microfabrication technique, and the fluid flow in the apical and basolateral sides of intestinal tract was reproduced with a two-layer microfluidic device. A wide range of flow rates was achieved by using gravity-induced flow, potentially facilitating easier high-throughput implementation. The kinetics of diffusion process through the 3-D villi scaffold in the microfluidic device was measured and mathematically modeled. When combined with intestinal cell culture model, this novel 3-D microfluidic system can serve as an in vitro platform that better mimics the in vivo environment.

A mechanistic model for hydrocarbon plumes rising through water

For releases of hydrocarbons from a subsea pipeline, riser, or production facility, the shape of the plume rising through the water must be predicted prior to any assessment of gas dispersion, liquid pools, or fire above the water surface. The location and size of the plume at the water surface are key parameters for subsequent consequence modeling. A mechanistic model has been developed to predict the plume trajectory and size, based on mass and momentum balances and an empirical water entrainment ratio from the literature. With suitable physical property values available, the model is applicable to releases of gas and/or liquid hydrocarbons, predicting the vaporization and vapor expansion due to decreasing hydrostatic pressure as the plume rises through the water. Some validation of the model was obtained with 16 tests in a small-scale transparent tank. The data cover a wide range of flow rates, including both choked and unchoked flow. The predicted and measured trajectories (centerline displacement) agreed reasonably well. Predictions of the model are presented for three fluids. The model is valuable for assessing the consequences of underwater hydrocarbon releases, providing input for subsequent modeling of gas dispersion or liquid pools and pool fires.

A new type of flow structure in cocurrent adiabatic vertically downward air–water flow: Membrane flow

A new type of flow structure has been observed in cocurrent adiabatic vertically downward air–water flow and is described here. Membranes, in the form of thin liquid films spanning the channel cross-section and horizontally dividing the gas core were visualised over a wide range of air and water flow rates. Videos recorded with a high-speed digital camera showed that these membranes formed by the coalescence of dispersed bubbles, from the interaction between large entrained bubbles and the annular liquid film, or from the shrinkage of the liquid slugs. The objectives of this paper are to describe the characteristics of these membranes, to present how they interact with other two-phase flow structures, and to investigate how they form and develop as they are convected along the annular liquid film by the air core. The influence of the air–water mixer, the test section geometry, and the operating conditions on the formation of these thin liquid membranes are also assessed.

DNA-based highly tunable particle focuser

DNA is distinguished by both long length and structural rigidity. Classical polymer theories predict that DNA enhances the non-Newtonian elastic properties of its dilute solution more significantly than common synthetic flexible polymers because of its larger size and longer relaxation time. Here we exploit this property to report that under Poiseuille microflow, rigid spherical particles laterally migrate and form a tightly focused stream in an extremely dilute DNA solution (0.0005 (w/v)%). By the use of the DNA solution, we achieve highly efficient focusing (>99.5%) over an unprecedented wide range of flow rates (ratio of maximum to minimum flow rates ~400). This highly tunable particle-focusing technique can be used in the design of cost-effective portable flow cytometers, high-throughput cell analysis and also for cell sorting by size. We demonstrate that DNA is an efficient elasticity enhancer, which originates from its unique structural properties.

Effect of fluid rheology on enhanced oil recovery in a microfluidic sandstone device

As global energy usage increases, maximizing oil recovery from known reserves becomes crucial to meet the rising demand. In this work, we present the development of a microfluidic sandstone platform capable of quickly and inexpensively testing the performance of fluids with different rheological properties on the recovery of oil. Specifically, in this study we utilized these microfluidic devices to examine how shear-thinning, shear-thickening, and viscoelastic fluids affect oil recovery. Initial baseline experiments were performed by displacing oil with both water and a water–surfactant solution over a wide range of flow rates. The surfactant was found to reduce the interfacial tension of the water by a factor of ten and increased oil recovery by approximately 15% when compared to oil displaced by water at the same flow rates. Flopaam, a commercially available fluid thickener that is shear-thinning and viscoelastic was also studied. It was found to displace more oil then either the water or the surfactant solution and increase oil recovery at all flow rates studied. Finally, a shear-thickening nanoparticle solution was studied which was designed to thicken at a shear rate of approximately 10s−1. The shear rate corresponds to typical shear rates in the oil reservoirs, and values easily attainable in our microfluidic sandstone device. These shear-thickening fluids were found to be particularly effective at oil recovery. This was especially true for flowrates that closely matched the shear rates associated with the shear-thickening regime. When the appropriate choice of shear rate dependent viscosity was used to the capillary number, the oil recovery obtained from both the Newtonian and non-Newtonian was found to collapse quite well onto a single master curve. Additionally, it was shown that a two-stage recovery process that starts with an initial water flood followed by a flood with a secondary fluid can recover as much oil as a single stage recovery with that secondary fluid alone. These results clearly demonstrate that the microfluidic sandstone devices presented in this paper both reduce the time and cost required to investigate the effectiveness of enhanced oil recovery fluids using traditional methods, and can serve to quickly focus searches for customized oil recovery fluid selection.