Adjustable Frequency Fluidic Oscillator with Supermode Frequency

This paper presents the results of an experimental study on the control of the deflection and reattachment of a radial wall jet through comparatively wide spaced two parallel disks, with an additional control flow. The flow field may be considered as having properties including those of the deflected jet, reattached jet and wall jet. The effects of opposite wall height (distance of opposite wall surface from the nozzle center plane) and control flow rate (ratio of control flow rate to main jet flow rate) on the flow pattern near the nozzle outlet section were investigated. The velocity profile, shape and length of a jet potential core, and the deflection of a jet center axis depend mainly on the combination of the opposite wall height and the control flow rate.

A numerical investigation on the utilization of a depleted natural gas field for seasonal hydrogen storage: A case study for Değirmenköy gas field

Using the Ansys Fluent 2020 R2 computational fluid dynamics suite, a method for calculating the three-dimensional velocity field in helicoid-type turbine flowmeters has been developed, based on the torque balance equation, i.e. the equality of the driving and retarding torques on the turbine, which is achieved at an equilibrium rotation speed for a given constant volumetric flow rate (which is fulfilled when the angular acceleration is equal to zero). At constant flow rate, when the rotor speed changes, the moment on the rotor blade is determined. The value of the speed is found at which the moment changes sign. The dependence of the torque on the number of revolutions is plotted on a graph and the true number of revolutions is determined at which the torque is zero for a given flow rate. The basis for the mathematical description of turbulent three-dimensional flow in flow meters is a system of differential equations of conservation of mass (continuity equation), momentum and the standard k-ω turbulence model (based on the Wilcox model) with partial derivatives in cylindrical coordinates in a three-dimensional problem setting. The multiple reference frame method incorporated into the Ansys Fluent computing suite allows reducing a problem involving stationary and rotating elements to a stationary one. The numerical calculation was performed at various flow rates (from 354 to 1982 m3/h) and kinematic viscosity (from 0.2 to 140 cSt). The main characteristics of turbine flowmeters are determined: the specific meter factor (or K-factor), Strouhal and Roschko numbers. The greatest discrepancy between the numerical calculation and the experimental data on the K-factor value is obtained at low flow rates and at the highest viscosity of 140 cSt (which is beyond the scope of application of the researched flowmeter) and is no more than 5%.

With the use of theoretical models of filtration liquid flows in fractures of finite and infinite lengths, formed in an oil stratum, the problem on the production of oil from a well, operating in the regimes of constant differential pressure or constant flow rate in this stratum, was solved. On the basis of approximate solution of the problem on the flow of oil from a stratum into a fracture formed in it by the method of successive changing stationary states, fairly simple analytical formulas have been obtained. A comparison of the results of numerical calculations of the practically important parameters of an oil stratum and a hydraulic fracture in it by the approximate formulas constructed and the corresponding exact formulas, which are much more complex than the approximate formulas, has shown that these results are almost identical. In particular, the errors in determining the evolution of the pressure field in a well and its flow rate by the approximate formulas did not exceed several percent. On the basis of numerical analysis of the approximate solutions obtained, the influence of the porosity and permeability of the stratum, the length of a fracture in it, and the rheological properties of the liquid saturating the stratum on the evolution of the pressure in the fracture, the flow rate of a well operating in the regime of constant differential pressure in the stratum, and the changes in the pressures in the fracture and in the well at a constant well flow rate was investigated.

Vincristine has been proven promising regarding its safety and efficacy for the renal artery denervation both in experimental models and in humans. The aim of the study was to compare in an experimental model the efficacy of constant versus random flow rate delivery of vincristine on renal sympathetic denervation. We used 10 juvenile Landrace swine. After the introduction of a 7F sheath into the femoral artery, a guide wire was advanced into the distal part of the renal artery. Then the first delivery balloon catheter, which delivers vincristine in random flow rate, was advanced at the proximal part of the artery, and the balloon was inflated in order to locally deliver vincristine to the media of the renal artery. The process was repeated in the contralateral renal artery, with the use of the double balloon catheter that delivers vincristine with a constant flow rate. Euthanasia of the animals was performed at 28 days. All sections were processed for histological and immunohistochemical analysis. The delivery of vincristine with both catheters was successful and uncomplicated. Immunohistochemistry showed that the mean number of intact nerves in all sections was significantly lower in the group of vincristine delivered with constant flow catheter compared to the group that the delivery was performed in a random fashion. (1.48 ± 0.37 vs. 1.70 ± 0.41, p = 0.04). Chemical renal denervation with vincristine by a constant flow rate catheter is more effective compared to the denervation performed by a catheter that delivers vincristine in a random fashion.

An inexpensive and simple pumping principle is described that is capable of delivering both small and constant flow rates (10–1,000 nl/min) over a longer period of time (days to weeks). The concept is based on controlled evaporation of a liquid through a membrane into a gas space containing a sorption agent. As long as the sorption agent keeps the vapor pressure in the gas phase below saturation, fluid evaporated from the membrane is replaced by capillary forces inducing flow from a reservoir. In a feasibility study, a total volume of 300 μl of Ringer's solution has been continuously pumped over a period of six days, resulting in an constant average flow rate of 35 nl/min (590 pl/s). The maximum liquid volume transported is limited by sorption capacity and amount of the sorption agent. Low fabrication costs, high reliability (no moving parts), the suitability for integration into planar system architectures and the lack of a special external energy source besides an environment of regulated temperature are important features of the concept, in particular with regard to its potential application in continuous patient monitoring. Truly continuous flow can be achieved in contrast to many other pump mechanisms leading to discontinuous, pulse-type flow. A challenge for a broader range of applications is the inherent temperature dependence of the flow rate. In its current version, the pump can only be used in a suction-mode.

Without requiring any moving part or piezoelectrical elements, fluidic oscillators are actuators able to convert a steady jet into an oscillating one, only due to internal fluid dynamic mechanisms. Since the oscillations of such jets are self-induced and self-sustained, the interest in fluidic oscillators has grown over the last years, especially for film cooling, flow control and heat transfer applications. The oscillation frequency, the sweeping angle and the flow field characteristics of sweeping jets greatly depend on various geometric and fluid dynamic parameters. Therefore, in the current work, through the application of the planar PIV technique, the effects of nozzle-to-plate distance and feedback channel minimum cross-sectional area on the external flow field of impinging sweeping jets are investigated. Non-dimensional nozzle-to-plate distances H/w equal to 2, 4, 6, 8 and 10 are taken into account, being w the exit nozzle throat section width. To analyze the effects of the feedback channel minimum cross-sectional area, a fluidic oscillator having a mixing chamber length Lf/w = 4.5 is provided with threaded holes in correspondence of the feedback channels, in which a micrometric screw is fastened to vary the parameter g/w, being g the feedback channel minimum passage width; values of g/w equal to 0.17, 0.33, 0.50, 0.67 and 1 are considered. Time-averaged and phase-averaged analyses are performed; indeed, the pressure signal measured between the inlet and outlet sections of one feedback channel is used to identify the phase of each velocity snapshot, despite the velocity measurements are not time-resolved. Firstly, the configuration with g/w=1 is taken as reference case, thus analyzing the nozzle-to-plate distance effect. The phase-averaged velocity and fluctuating kinetic energy fields show that the jet sweeps in the external flow field, with a sweeping angle approximately equal to 25° and a frequency of 50 Hz. Due to this behavior, the time-averaged velocity field exhibits a twin-jet pattern, which can also be identified from the time-averaged Phase-correlated Kinetic Energy (PKE) distributions (see Figure 1, left). Indeed, the extreme positions of the oscillating motion are the zones in which the coherent oscillation of the velocity values is greater and, therefore, the PKE values are the greatest. Furthermore, while at H/w=2 the jet sweeps in an almost rigid-like way between the two extreme positions reached during its oscillating motion, at greater nozzle-to-plate distances a phase delay between the motion of the jet near the impinging plate and near the exit nozzle section can be observed. Considering the effects of the feedback channel minimum cross-sectional area, by reducing g/w the sweeping angle of the jet decreases, while the oscillation frequency increases. Still, a twin-jet pattern can be identified for g/w≥0.33, as it can be seen from the crosswise profiles of the dimensionless time-averaged axial velocity (see Figure 1, right), while for g/w=0.17 a single-jet velocity structure can be identified. Nevertheless, as g/w decreases the maximum values of the velocity increase while the oscillation intensity decreases, resulting in a decrease of the PKE values.

Accurate measurement of relative permeability curve is the basis for evaluating gas reservoir performance. The unsteady-state method could bring significant measurement error for low-permeability cores. However, it is difficult to control the constant gas flow rate in the traditional steady-state method, which obstacles the experimental operation. In this study, an improved steady-state method was proposed. First, the pressure value obtained from the experiment, when the gas permeability no longer changed with the average pressure on the rock core, was set as the testing pressure. Then, the gas was injected under constant pressure, and the water was injected with a constant flow rate. Finally, the relative permeability values of gas and water phases were calculated based on Darcy’s law. Comparative analysis of the results of the relative permeability curves under formation pressure and pressure with negligible slip effect indicates that the relative permeability curves are the same in gas and water phases, proving the feasibility of the new method. Further, the results were compared with those of the test method at normal pressure, the water-phase relative permeability showed no significant change, the relative permeability of gas phase was larger, the two-phase flow area became wider, and the irreducible water saturation was lower than that at the normal pressure. This result reflects that pressure does not significantly affect the flow of wetting phase but tremendously influences the nonwetted phase under low pressure. The relationship between relative permeability and water saturation is linear in the semilogarithmic coordinate diagram and can be described by using the following relationship: ln k rg / k rw = a S w + ln b . With the decrease in the core permeability, relative permeability curve, and isotonic point moved to the right, irreducible water saturation gradually increased, and residual gas saturation decreased, indicating that the smaller permeability induced a lower gas-phase flow capacity.

A capillary suction pump giving constant flow rates

Dehydrogenation performance of metal hydride container utilising MgH2-based composite

Determination of formation permeability and well skin factor is important for forecasting flow rates of oil and gas wells. A new technique for analysing test data for stimulated oil wells produced at a constant bottomhole pressure (BHP) has been developed. The method presented in this paper allows one to calculate the skin factor and estimate the formation permeability. It is assumed that the instantaneous flow rate and time data are available from a well produced against a constant bottomhole pressure. Only records of the flowing time and flow rate data are required to compute the values of the skin factor and formation permeability. A semi-theoretical equation is used to approximate the dimensionless flow rate. Our objective is to validate the new suggested method (prior to conducting a field test) by using a simulated example, where a numerical solution is used as an ‘exact’ solution.‘Bottomhole pressure’ means the pressure determined at the face of the producing horizon by means of a pressure-recording instrument. In the case of gas wells or wells having no liquid in the well bore, it means the pressure as calculated by adding the pressure at the surface of the ground to the calculated weight of the column of gas from the surface to the bottom of the hole. Determination of bottomhole pressure (BHP) is an important problem in the oil and gas industry (Akhter and Kreitler, 1990; Schechter, 1992; Yang et al., 2003). At present the majority of well tests are conducted at constant flow rates, where simple solutions of the diffusivity equation can be applied. However, many investigators (Ehlig-Economides and Ramey, 1981; Sengul, 1983; Uraiet and Raghavan, 1980 a.o.) hold to the idea that in practice it is easier to conduct well tests at a constant bottomhole pressure (BHP). It is very difficult to maintain a constant flow rate during long flowing times (especially when testing low permeability formations). The advantages of the constant BHP test are: (1) the fluid production can be easily controlled (at constant flow rate tests the BHP is changing with time); and (2) wellbore storage effects on the test data are short-lived. One of the reasons that constant BHP tests have not been utilized in reservoir engineering is that only numerical solutions of the diffusivity equation for a cylindrical source with a constant BHP have been available. Due to the similarity in Darcy’s and Fourier’s laws, the same differential diffusivity equation describes the transient flow of incompressible fluid in a porous medium and heat conduction in solids. As a result, a correspondence exists between the following parameters: volumetric flow rate, pressure gradient, mobility (formation permeability and viscosity ratio), hydraulic diffusivity coefficient and heat flow rate, temperature gradient, thermal conductivity and thermal diffusivity. Thus, the same analytical solutions of the diffusivity equation (at corresponding initial and boundary conditions) can be utilized for determination of the above-mentioned parameters. Earlier we suggested a semi-theoretical equation to approximate the dimensionless heat flow rate from an infinite cylindrical source with a constant bore-face temperature (Kutasov, 1987). This equation (in terms of pressure and flow rate) was used to process data of step pressure tests when fluid is produced at two successive bottomhole pressures (Kutasov, 1998). The same equation was used to estimate the efficiency of stimulating operations (Kutasov and Kagan, 2003). In both cases a technique for determining the formation permeability and skin factor from flow tests in stimulated wells was developed. The objective of this paper is to suggest a similar technique for determination of the values of formation permeability and skin factor from drawdown constant BHP tests in stimulated wells. We should also like to mention that for damaged wells, when the dimensionless time based on the apparent well radius is very large, a simple equation can be used to process field data (Sengul, 1983; Earlougher, 1977).

Summary This paper presents new guidelines for determining net pay thickness in low-permeability, multilayered gas wells. These criteria were developed from a sensitivity study performed with an analytical solution for compmlex multilayered reservoirs. The purpose of this study was to determine whether many layers now considered to contribute to net pay actually have transmissibilities too low for the layer to be productive, causing performance projections from current single-layer descriptive models to be too optimistic. Introduction Devonian shales are multilayered, frequently naturally fractured reservoirs with a large variance in permeability between layers. Many Devonian shale wells have had hydraulic fracture treatments to increase productivity; however, the fractures may exist only in some of the many layers of the reservoir. According to conventional post-fracture pressure-buildup test analysis, stimulation of the Devonian shale wells has fallen short of design expectations. This paper presents results from a study using an analytical solution for multilayered wells that suggest that conventional analysis of tests from these wells is inadequate because of the simplicity of the reservoir model used to describe them. We developed a new analytical solution, based on Laplace transform methods, similar to Spath et al.'s1 recent solution. This solution accurately models the complexity of Devonian shale wells. Devonian shale completions frequently consist of at least five layers commingled at the wellbore. Some layers are naturally fractured, interspersed with homogeneous-acting silt layers. Some or all of the layers may contain a hydraulic fracture, and some layers may be of limited areal extent. Gas production from these wells is at a constant bottomhole pressure (BHP). The analytical solution we have programmed can model all these conditions. We studied two-layer systems systematically to find a minimum transmissibility for a layer to be considered part of the net pay thickness. This study considered homogeneous or naturally fractured layers, with and without a hydraulic fracture in the layer. The results from this two-layer study were extended and confirmed for multilayered cases. Unless layers are tested individually, conventional pressure-buildup analysis results in a total transmissibility, kh, and an equivalent fracture half-length for the entire net pay zone. When these results are used in performance projections with a single-layer model, forecasts have consistently proved to be optimistic. We used the analytical solution to compare the impact of a fracture treatment that affects only one layer in a five-layer system with a fracture of the same length in the total system. The input parameters for the analytical simulation for the five-layer case were obtained from geophysical logs, production logs, and well tests in typical eastern Devonian shale wells. We illustrate the power of the model through a field case described with individual-layer test results. Here, we first describe the model used to simulate the complex Devonian shale formation. We verified this model using examples from the literature2-6 and a commercial analytical simulator; detailed results are given in Ref. 3. We then present our results from both the two-layer and the multi-layer studies. Finally, we state conclusions drawn from the results of the research. Model Description The analytical solution can model n layers. Each layer can be either naturally fractured, with pseudo-steady-state or transient interporosity flow, or homogeneous-acting. Individual layers may have hydraulic fractures of various lengths, with either infinite conductivity or uniform flux. The layers can be infinite-acting or can act as closed systems with various drainage areas. Each layer can have a different permeability, thickness, porosity, wellbore radius, skin, fracture half-length, or natural fracture characteristics. The multilayered system is commingled at the wellbore, with no crossflow between layers. The well may be produced at constant BHP or at constant total flow rate. The solutions were developed for slightly compressible liquids, but the use of normalized pseudopressure in the solution allowed us to consider gas production. Isothermal conditions, negligible gravitational effects, production of a single-phase fluid, laminar flow behavior (gas velocities low enough that non-Darcy flow effects are negligible), permeability independent of pressure, and a viscosity/compressibility, µct, product that is constant with pressure were assumed. The Appendix presents a derivation of the analytical solution. This reservoir model will have many applications in reservoir description beyond those discussed.

Cr-C coatings with gradient Cr/CrN/CrCN inter-layers were studied to elucidate the effects of carbon contained on the mechanical properties and microstructures of the deposited coatings. The coatings were deposited by using a reactive sputtering system with constant total flow rate, target current and substrate bias. Percentage of C2H2flow rates were varied from 10 % to 50 %. Carbon contains in the film were measure by EDS. Mechanical properties of the coatings were evaluated with micro-indentation, scratch tester, ball-on-disk tribo-tester. Microstructures of the films were characterized by SEM, TEM, and X-ray diffractermeter. The experimental results show that carbon contain increase from 21.6 %to 99.5 % with respect to C2H2flow rates varied from 10 %, 20 %, 30 %, 40 %, 50%. And the phase of coatings change from Cr solid solution to Cr+Cr23C6+ amorphous diamond like carbon (DLC) and then to DLC +Cr7C3and then to DLC+ Cr3C2+Cr7C3. The hardness of the coatings increase with C2H2flow rate increased and achieved the maximum value of Hv1815 at 50% C2H2flow rate. The coefficient of friction decreases from 0.630 to 0.285 when C2H2flow rate increased from 10% to 50%. The wear rate decreased with increasing the C2H2flow rate.

The compression resin transfer molding (CRTM) filling process involves two stages: the injection phase and the compression phase. Two injection modes are considered — constant volumetric flow rate and constant pressure — while the constant compression velocity is utilized in this study. Three typical cases are used to investigate the compression initiation effects on the filling process. When the inlet condition is a constant flow rate, the numerical results show that the compression has both increase and decrease effects on the inlet pressure. Thus, a discontinuity in the inlet pressure is present at the onset or the end of compression. Among three CRTM cases, the process with a simultaneous injection and compression end maximally reduces the inlet pressure by 80% but increases the mold filling time by 65% compared with the resin transfer molding (RTM). For the inlet condition being a constant pressure, the resin may flow out of the mold cavity through the inlet when an excessively low injection pressure and high compression speed are applied concurrently. Compared with RTM, the CRTM processes reduce the mold filling time by 68–76% but cannot ensure a reduction in inlet pressure.

The flow field in a wall attachment amplifier was visualized and analyzed numerically, and the flow pattern was made clear in the former studies (1) (2) (3). Also, the field-diving method using the k-εturbulent flow model was developed, and its effectiveness has been confirmed by the experiment of flow visualization and velocity measurement. In this study, the variations of the input and output static characteristics of a wall attachment device were made clear by numerical analysis and experiments changing the splitter distance, supply and control flow rate. In this case, a FLIP-FLOP-type logical device was used as the wall attachment device. The numerical method used was the flow-field diving method using the k-εturbulent model, as in the former reports. The input and output static characteristics were determined from the velocity and pressure distributions obtained by using this numerical analysis method. The experiments were performed by changing the Reynolds number, control flow rate and splitter distance. The results were compared with analytical values with which they were in good agreement. From these results, the effects that the variation of splitter distance, control flow rate and supply flow rate exerted on the characteristics of the device were made clear, and the effectiveness of the flow-field dividing method for the calculation of the characteristics was confirmed.