Pressure Flow Rate Relationship Research Articles

Fully coupled simulation of dynamic characteristics of a backward bent duct buoy oscillating water column wave energy converter

In this paper, a fully coupled model for a backward bent duct buoy oscillating water column (BBDB-OWC) wave energy converter (WEC) is established, with the consideration of strong transient nonlinear interactions among ocean waves, BBDB hull motion, mooring system, internal water column oscillation, aerodynamics, turbine rotation and the damping effect of the generator. The model is validated by comparison with experimental results, and then used to investigate the transient characteristics and periodic average performance of the WEC under regular wave conditions. The differences in transient hydrodynamic characteristics and air pressure-flow rate relationship between the fully coupled model and the orifice model are compared. The transient characteristics of an impulse turbine under reciprocating and transient airflows are studied. And the effect of wave period, wave height and load torque coefficient on the average performance of the WEC is investigated.

Precision flow rate control during micro-scale material extrusion by iterative learning of pressure-flow rate relationships

Despite its low-cost and broad material capability, material extrusion-based additive manufacturing suffers from low process resolution and dimensional accuracy, due to challenges with precisely controlling the ink flow rate during the printing process, particularly while using small nozzles and complex inks. In this paper, we present a novel approach to control the ink flow rate by utilizing (1) a printhead capable of concurrently monitoring and controlling the printing pressure (P) and steady-state flow rate (Q) and (2) an automatic iterative learning approach to elucidate the flow rate-pressure relationships for the system in the form of a Q-P relator model. Our studies showed that flow rate accuracy within 10% can be achieved with nozzles as small as 100 microns in diameter through implementation of the trained Q-P relator with both pressure and piston velocity-controlled printing. Particularly, Q-P relator enables proper selection of printing pressure to achieve desired flow rate during pressure-controlled printing, while providing a means of smart-priming of the system prior to velocity controlled printing to overcome the system transients. We also characterized the performance of the iterative learning process, focusing on time to convergence, effect of steady-state detection, and accuracy variation across various time scales. Presented results indicate that the proposed method will increase the microscale material extrusion process resolution and accuracy, and minimize material waste and reduce time to production.

Dynamic modelling and engineering simulation of fluid mechanics in water injectors

To study the fluid dynamic response mechanism under the working condition of water injection well borehole, based on the microelement analysis of fluid mechanics and the classical theory of hydrodynamics, a fluid microelement pressure-flow rate relationship model is built to derive and solve the dynamic distribution of fluid pressure and flow rate in the space of well borehole. Combined with the production data of a typical deviated well in China, numerical simulations and analyses are carried out to analyze the dynamic distribution of wellbore pressure at different injection pressures and injection volumes, the delayed and attenuated characteristics of fluid transmission in tube, and the dynamic distribution of wellbore pressure amplitude under the fluctuation of wellhead pressure. The pressure loss along the wellbore has nothing to do with the absolute pressure, and the design of the coding and decoding scheme for wave code communication doesn't need to consider the absolute pressure during injecting. When the injection pressure is constant, the higher the injection flow rate at the wellhead, the larger the pressure loss along the wellbore. The fluid wave signal delay amplitude mainly depends on the length of the wellbore. The smaller the tubing diameter, the larger the fluid wave signal attenuation amplitude. The higher the target wave code amplitude (differential pressure identification root mean square) generated at the same well depth, the greater the wellhead pressure wave amplitude required to overcome the wellbore pressure loss.

Clogging of a Rectangular Slit by a Spherical Soft Particle.

The capture of a soft spherical particle in a rectangular slit leads to a nonmonotonic pressure-flow rate relation at low Reynolds number. Simulations reveal that the flow induced deformations of the trapped particle focus the streamlines and pressure drop to a small region. This increases the resistance to flow by several orders of magnitude as the driving pressure is increased. As a result, two regimes are observed in experiments and simulations: a flow-dominated regime for small particle deformations, where flow rate increases with pressure, and an elastic-dominated regime in which solid deformations block the flow.

Complex ink flow mechanisms in micro-direct-ink-writing and their implications on flow rate control

Despite its simplicity, low cost, and ability to process a wide range of materials, direct-ink-writing (DIW) is an additive manufacturing process with low resolution and accuracy, in the multiple hundred microns to millimeter range. One of the main sources for this issue is the difficulty with accurately controlling ink flow rate at smaller size scales. Towards addressing this limitation, this paper elucidates complex ink flow mechanisms that renders flow rate control difficult and explores printing implementations to increase flow rate accuracy in direct-ink-writing at the micro scale. To this end, a DIW system utilizing hybrid pressure and velocity-controlled extrusion is used to obtain pressure-flow rate relationships for a water-based sodium carboxymethyl cellulose (NaCMC) solution ink, as a function of printing nozzle diameter (510–100 µm). These studies showed that the transient response of piston velocity-controlled extrusion significantly slows down with decreasing nozzle diameter. For pressure-controlled extrusion, the wall slip increases with decreasing nozzle diameter and the constant slip velocity assumption no longer holds as nozzle size decreases below a certain diameter. To contextualize the influence of such behavior on flow rate accuracy, temperature-controlled parallel plate rheometry was performed on the inks and rheological ink models were accordingly determined. It was shown that the associated flow rate predictions under predicted flow rates due to lack of wall-slip consideration, particularly for smaller nozzle sizes. Lastly, an iterative pressure-controlled DIW implementation was explored to address the accuracy issues for micro-DIW. Our results indicated significant improvement in the transient response and flow rate accuracy for nozzle diameters as small as 100 µm using this approach compared to both of the conventional pressure and velocity control approaches.

Pumping of concrete: Understanding a common placement method with lots of challenges

Several million cubic meters of concrete are pumped daily, as this technique permits fast concrete placement. Fundamental research has been performed and practical guidelines have been developed to increase the knowledge of concrete behavior in pipes. However, the pumping process and concrete behavior are not fully understood. This paper gives an overview of the current knowledge of concrete pumping. At first, the known physics governing the flow of concrete in pipes are introduced. A series of experimental techniques characterizing concrete flow behavior near a smooth wall to predict pressure-flow rate relationships are discussed, followed by recent developments in the use of numerical simulations of concrete behavior in pipes. The influence of the pumping process on concrete rheology and air-void system is reviewed, and the first developments in active rheology control for concrete pumping are introduced. The last section of this paper gives an overview of open research questions and challenges.

Dimensional analysis modeling of spraying operation – Impact of fluid properties and pressure nozzle geometric parameters on the pressure-flow rate relationship

In food industry, atomization is an essential process as a large range of products are manufactured by spray drying of concentrated solutions. The pressure drop inside the nozzle, and its relation with the flowrate, is of prime importance to size an efficient continuous process. This work thus aims at both studying liquid atomization using pressure nozzles with throttle inserts and proposing a ready-to-use pressure/flowrate correlation from a series of experimental data. Beside the process parameters (flowrate) and fluid parameters (viscosity, density) of prime importance, the geometrical parameters of the nozzle were also accounted for to obtain a generic correlation. Using Newtonian maltodextrin aqueous solutions with viscosity ranging from 1 to 70.10-3 Pa s and eleven nozzle geometries, 264 experiments were performed. Through the use of a dimensionless pressure drop number (Euler number), all the experimental points gathered on a single Eu* vs. Re curve where conventional atomization regimes could be clearly identified. A comprehensive dimensional analysis, relying on the Vashy-Buckingham theorem, was performed. A set of dimensionless correlations, allowing to predict the pressure loss over a wide range of Reynolds number from parameters linked to the fluid, process and nozzle geometry, was then deduced from experimental data.

Corrigendum to "Evaluating the Hemodynamical Response of a Cardiovascular System under Support of a Continuous Flow Left Ventricular Assist Device via Numerical Modeling and Simulations".

[This corrects the article DOI: 10.1155/2013/986430.].

Cilia-assisted hydromagnetic pumping of biorheological couple stress fluids

A theoretical study is conducted for magnetohydrodynamic pumping of electro-conductive couple stress physiological liquids (e.g. blood) through a two-dimensional ciliated channel. A geometric model is employed for the cilia which are distributed at equal intervals and produce a whip-like motion under fluid interaction which obeys an elliptic trajectory. A metachronal wave is mobilized by the synchronous beating of cilia and the direction of wave propagation is parallel to the direction of fluid flow. A transverse static magnetic field is imposed transverse to the channel length. The Stokes’ couple stress (polar) rheological model is utilized to characterize the liquid. The normalized two-dimensional conservation equations for mass, longitudinal and transverse momentum are reduced with lubrication approximations (long wavelength and low Reynolds number assumptions) and feature a fourth order linear derivative in axial velocity representing couple stress contribution. A coordinate transformation is employed to map the unsteady problem from the wave laboratory frame to a steady problem in the wave frame. No slip conditions are imposed at the channel walls. The emerging linearized boundary value problem is solved analytically and expressions presented for axial (longitudinal) velocity, volumetric flow rate, shear stress function and pressure rise. The flow is effectively controlled by three geometric parameters, viz cilia eccentricity parameter, wave number and cilia length and two physical parameters, namely magnetohydrodynamic (MHD) body force parameter and couple stress non-Newtonian parameter. Analytical solutions are numerically evaluated with MATLAB software. Axial velocity is observed to be enhanced in the core region with greater wave number whereas it is suppressed markedly with increasing cilia length, couple stress and magnetic parameters, with significant flattening of profiles with the latter two parameters. Axial pressure gradient is decreased with eccentricity parameter whereas it is elevated with cilia length, in the channel core region. Increasing couple stress and magnetic field parameter respectively enhance and suppress pressure gradient across the entire channel width. The pressure-flow rate relationship is confirmed to be inversely linear and pumping, free pumping and augmented pumping zones are all examined. Bolus trapping is also analyzed. The study is relevant to MHD biomimetic blood pumps.

Numerical solution of hydromagnetic peristaltic flow in a porous-saturated heated channel

The hydromagnetic-flow in sinusoidally heated porous channel is studied by utilizing Darcy-Forchiemmer law with Joule heating effect. The Darcy?s resistance term in the momentum equation is acquired by using modified Darcy?s law. The governing equations for flow velocity, temperature, and mass concentration are developed under lubrication approximation, commonly known as long wavelength assumption in the realm of peristaltic flows. A well-tested implicit finite difference scheme is employed to solve the set of these equations along with appropriate boundary conditions. The governing equations involve important parameters namely, Forchiemmer parameter, dimensionless radius of curvature, permeability parameter, Hartmann, Brinkmann, Schmidt, and Soret numbers. The effect of these important parameters on velocity, temperature and mass concentration is illustrated through graphs. The pressure-flow rate relationship and streamlines are also shown. The presence of porous matrix inside the channel impedes the flow velocity and reduces the peristaltic transport and mingling. Moreover, temperature of the fluid rises with decreasing permeability of porous-matrix and Hartmann number.

Neutral Network Models for Predicting Wellhead Pressure-Flow Rate Relationship for Niger Delta Oil Wells

Neutral Network Models for Predicting Wellhead Pressure-Flow Rate Relationship for Niger Delta Oil Wells

Caracterização hidráulica de tubos porosos oriundos de pneus reciclados utilizados em irrigação subsuperficial

Mesmo diante do apelo ecológico pelo reaproveitamento de resíduos, os produtos de irrigação, como é caso de tubos porosos oriundos de pneus reciclados, devem ser avaliados quanto à sua viabilidade técnica. A caracterização hidráulica é um dos requisitos necessários para tal finalidade além de fornecer dados essenciais ao dimensionamento de sistemas de irrigação. Diante do exposto objetivou-se caracterizar tubos porosos quanto aos fatores perda de carga, vazão em função da pressão e variação de vazão. Foram utilizadas cinco amostras de tubo para determinação da perda de carga e oito para a determinação da curva vazão-pressão e do coeficiente de variação, sendo ensaiados sete níveis de pressão. A perda de carga foi determinada com tubo impermeabilizado e com distribuição de vazão para diferentes vazões. O tubo poroso apresentou coeficiente de variação de vazão em torno de 5%, considerado resultado satisfatório. O modelo potencial não se ajustou aos dados da curva característica vazão-pressão. Os fatores de atrito e de redução de perda de carga apresentaram comportamento divergente da literatura em que outros fatores, como a variação do diâmetro, devem ser estudados com maiores detalhes.

Evaluating the Hemodynamical Response of a Cardiovascular System under Support of a Continuous Flow Left Ventricular Assist Device via Numerical Modeling and Simulations

Dilated cardiomyopathy is the most common type of the heart failure which can be characterized by impaired ventricular contractility. Mechanical circulatory support devices were introduced into practice for the heart failure patients to bridge the time between the decision to transplant and the actual transplantation which is not sufficient due to the state of donor organ supply. In this study, the hemodynamic response of a cardiovascular system that includes a dilated cardiomyopathic heart under support of a newly developed continuous flow left ventricular assist device—Heart Turcica Axial—was evaluated employing computer simulations. For the evaluation, a numerical model which describes the pressure-flow rate relations of Heart Turcica Axial, a cardiovascular system model describing the healthy and pathological hemodynamics, and a baroreflex model regulating the heart rate were used. Heart Turcica Axial was operated between 8000 rpm and 11000 rpm speeds with 1000 rpm increments for assessing the pump performance and response of the cardiovascular system. The results also give an insight about the range of the possible operating speeds of Heart Turcica Axial in a clinical application. Based on the findings, operating speed of Heart Turcica Axial should be between 10000 rpm and 11000 rpm.

MR Görüntülerine Dayalı Hesaplamalı Akışkanlar Dinamiği Yöntemi ile Non-İnvazif Ürodinamik Analiz

Objective: The pressure-flow rate test is invasive. In addition, several nomograms are used and an exact standardization cannot be provided. For this reason, the search for new methods that are called non-invasive by several authorities, and that will provide clinical data similar to urodynamics, is ongoing. The aim of this study is to report a non-invasive, newly developed technique for the assessment of bladder pressure and flow rate using Computational Fluid Dynamics (CFD). Material and Methods: Participants consisted of 10 voluntary males. All data referring to volunteer demographics were recorded. Magnetic resonance imaging (MRI) was performed for the reconstruction of the bladder. After the MRI process, the peak flow-rates were measured with a uroflowmeter. Using CFD, first, by applying a pressure of 20 cm H2O to the bladder wall the geometry of the bladder was obtained from processing of MR images and flow rates were determined. Secondly, the wall pressures needed to provide flow rates obtained from uroflowmetry were calculated. Results: The average values of the measured flow rate and the computed flow rate were calculated as 21.9 ± 7.8 ml/s and 24.6 ± 2.4 ml/s, respectively. It was found that the flow rates obtained from the uroflowmetry and the flow rates calculated by CFD were consistent with each other (p< 0.05). The average value of the computed bladder pressure was found to be 16.8 ± 9.6 cm H2O. Conclusion: CFD, which is widely used in biomechanical applications as well as engineering problems, was used to simulate the flow inside three dimensional bladder models obtained from MR images. By comparing the results achieved by this method and the results obtained by uroflowmetry, a significant correlation was found. A novel non-invasive alternative method was developed to investigate the pressure-flow rate relationship in the bladder which may also provide a basis for theoretical analysis.

Modeling and Identification of an Intra-Aorta Pump

The intra-aorta pump is a novel left ventricular assist device (LVAD) that assists the heart without the need for percutaneous wires and conduits. It is implanted between the radix aortae and the aortic arch to avoid damage to the aortic valve. To predict the mean pressure head and blood flow, a nonlinear lumped parameter model, which does not need the parameters of the circulatory system, is established. The model includes a speed-controlled current source, an internal resistor, and an inductance for simulating the pressure-flow rate relationship. The speed-controlled current source is used to represent the blood flow caused by the kinetic energy from the impeller, the internal resistor is used to stimulate the resistance character of the radial clearance of the intra-aorta pump, and the inductance is used to model the inertia of the blood that passes through the radial clearance. Each part of the model has clear physical significance, which is helpful for extending the model to other blood pumps. It can generate all status of the pump from suction to pulmonary congestion. The model is summarized as a function of the pressure head, the blood flow, and rotational speed of which the values of parameters in the model are determined by experiment. The model and prediction method are tested experimentally on an in vitro mock loop. A comparison of the predicted pressure head obtained from our model with experimental data shows that our model can predict the differential pressure accurately with error <5% for all experimental conditions over the entire range of intended use of the intra-aorta pump.

Abrupt contraction flow of magnetorheological fluids

Contraction and expansion flows of magnetorheological fluids occur in a variety of smart devices. It is important therefore to learn how these flows can be controlled by means of applied magnetic fields. This paper presents a first investigation into the axisymmetric flow of a magnetorheological fluid through an orifice (so-called abrupt contraction flow). The effect of an external magnetic field, longitudinal or transverse to the flow, is examined. In experiments, the pressure-flow rate curves were measured, and the excess pressure drop (associated with entrance and exit losses) was derived from experimental data through the Bagley correction procedure. The effect of the longitudinal magnetic field is manifested through a significant increase in the slope of the pressure-flow rate curves, while no discernible yield stress occurs. This behavior, observed at shear Mason numbers 10&amp;lt;Mnshear&amp;lt;100, is interpreted in terms of an enhanced extensional response of magnetorheological fluids accompanied by shrinkage of the entrance flow into a conical funnel. At the same range of Mason numbers, the transverse magnetic field appears not to influence the pressure drop. This can be explained by a total destruction of magnetic particle aggregates by large hydrodynamic forces acting on them when they are perpendicular to the flow. To support these findings, we have developed a theoretical model connecting the microstructure of the magnetorheological fluid to its extensional rheological properties and predicting the pressure-flow rate relations through the solution of the flow equations. In the case of the longitudinal magnetic field, our model describes the experimental results reasonably well.

Nonlinear pressure-flow relationships for passive microfluidic valves

An analytical solution is presented for the nonlinear pressure-flow relationship of deformable passive valves, which are formed by bonding a deformable film over etched channels separated by a weir. A fluidic pathway connecting the channels is opened when the upstream pressure creates a tunnel along a predefined narrow strip where the film is not bonded to the weir. When the width of the strip is comparable to the inlet channel width, the predicted closed-form pressure-flow rate relationship is in excellent agreement with experiments, which determine pressures by measuring film deflections for prescribed flow rates. The validated closed-form models involve no fitting parameters, and provide the foundation to design passive diodes with specific nonlinear pressure-flow characteristics.

Pulmonary Vascular Resistance and Impedance in Isolated Mouse Lungs: Effects of Pulmonary Emboli

To study pulsatile pressure-flow rate relationships in the intact pulmonary vascular network of mice, we developed a protocol for measuring pulmonary vascular resistance and impedance in isolated, ventilated, and perfused mouse lungs. We used pulmonary emboli to validate the effect of vascular obstruction on resistance and impedance. Main pulmonary artery and left atrial pressures and pulmonary vascular flow rate were measured under steady and pulsatile conditions in the lungs of C57BL/6J mice (n = 6) before and after two infusions with 25 microm-diameter microspheres (one million per infusion). After the first and second embolizations, pulmonary artery pressures increased approximately two-fold and three and a half-fold, respectively, compared to baseline, at a steady flow rate of 1 ml/min (P < 0.05). Pulmonary vascular resistance and 0 Hz impedance also increased after the first and second embolizations for all flow rates tested (P < 0.05). Frequency-dependent features of the pulmonary vascular impedance spectrum were suggestive of shifts in the major pulmonary vascular reflection sites with embolization. Our results demonstrate that pulmonary artery pressure, resistance, and impedance magnitude measured in this isolated lung setup changed in ways consistent with in vivo studies in larger animals and humans and demonstrate the usefulness of the isolated, ventilated, and perfused mouse lung for investigating steady and pulsatile pressure-flow rate relationships.

A new quantitative filtration apparatus to evaluate erythrocyte deformability.

We have developed a quantitative filtration apparatus to evaluate erythrocyte deformability, using a precision metal filter which we developed. The test material is sucked into the filter through the action of decreasing negative pressure. The device automatically gives a liquid level (height)-time relation and a pressure-flow rate relation, similar to gravity-based filtration. Unlike the gravity-based system, the experimental performance of this system is very good and reproducible.

Periodic oscillations in a horizontal single boiling channel with thermal wall capacity

The dynamic behavior of a horizontal boiling channel with a surge tank is investigated through nonlinear analysis. The model involves a surge tank that is subject to inlet mass flow rate and a constitutive model containing a cubic nonlinearity is used to describe the outlet pressure-flow rate relation of the downstream boiling regime. The model also includes boiling heat transfer process and incorporates the effect of the wall thermal capacity which allows the temperature and heat transfer coefficient of the heater wall to vary with time. Within certain operating regimes, the model exhibits self-excited periodic oscillations, which can be identified with pressure-drop oscillations. In this study, these oscillations are described as relaxation oscillation and the qualitative features of the response can be understood in terms of the underlying model. Finally, the present model is compared with the experimental data available in literature to investigate that transient effects of temperature heater walls, pressure, and mass flow rate.