Presence Of Crossflow Research Articles

Simulation study of water shut-off treatment for heterogeneous layered oil reservoirs

The purpose of this paper is to develop a hydrodynamic model of two-phase, three-component fluid flow in a heterogeneous layered reservoir, taking into account cross-flow between layers, and to predict the process of oil displacement by water under conditions of water shut-off in the vicinity of injection or production wells. Numerical calculations at different water cuts (38%, 50%, 96%) showed that in the presence of cross-flow between layers, the current oil recovery coefficient of the reservoir at water shut-off in the vicinity of the producing well increases by 0.3254, 0.3067, and 0.0429 respectively, compared to water shut-off in the vicinity of the injection well. In the absence of cross-flow between layers, there is a decrease in oil recovery coefficient by 0.0082 and 0.0072 at 38 and 50% water cut, respectively. Additionally, there is an increase in recovery coefficient by 0.007 at 96% water cut. It was also obtained that in the presence of cross-flow between layers the gel washout period at water shut-off in the vicinity of the injection well is less at different water cut in 1.24–1.81 times than in the vicinity of the production well. In the absence of cross-flow between layers, the washout time at 38 and 50% water cut is almost the same, but increases by 1.084 times at 96% water cut. Comparison of results of water shut-off prediction using proposed hydrodynamic model and real data showed that calculations describe real data with an average error of about 7%.

Effect of injector geometry in breakup of liquid jet in crossflow – insights from POD

The present study aims to investigate the role of injector geometry, particularly injector tube length to diameter ratio (L/D) in liquid jet stability and breakup in presence of crossflow. Water is injected into a crossflow of air. Aerodynamic Weber number (We) and liquid Reynolds number (Rel) are systematically varied to observe various breakup modes. Bag breakup and surface stripping is observed for different operating conditions. Time-resolved jet trajectory images are processed using Proper Orthogonal Decomposition (POD) algorithm. POD mode shapes and corresponding Power Spectral Density (PSD) plots are analyzed to study breakup process and probe role of injector geometry effects. Further, high-resolution images are captured for the near-nozzle region. Detailed comparison is made for various cases. It is observed that with increase in (L/D), the jet surface becomes more turbulent and unstable. This results in early breakup and lower jet penetration

Identifying Average Reservoir Pressure in Multilayered Oil Wells Using Selective Inflow Performance (SIP) Method

The downhole flow profiles of the wells with single production tubes and mixed flow from more than one layer can be complicated, making it challenging to obtain the average pressure of each layer independently. Production log data can be used to monitor the impacts of pressure depletion over time and to determine average pressure with the use of Selective Inflow Performance (SIP). The SIP technique provides a method of determining the steady state of inflow relationship for each individual layer. The well flows at different stabilized surface rates, and for each rate, a production log is run throughout the producing interval to record both downhole flow rates and flowing pressure. PVT data can be used to convert measured in-situ rates to surface conditions. Different types of Inflow Performance Relationship (IPR) equations can be used for SIP interpretation, including the Straight-line method, Fetkovitch method, and Laminar Internal Turbulent (LIT) relations. Although the SIP method can be used for single-phase flow, the interpreter can restrict the IPR’s calculations to a particular phase. This research discusses the difficulties in estimating the average reservoir pressure in multilayered reservoir completed wells over their production life. The SIP technique has been applied to some producing wells in the south of Iraq, which are completed in multiple producing reservoirs previously tested with a formation tester to estimate reservoir pressure and other parameters. Two wells are taken in the south of Iraq region, Zubair Oil Field, one with cross flow between perforations and the other well with no cross flow. An average pressure is not calculated for layer A in Well-1, because there is no contribution rate. While the average pressure for Well-1, layer B is 3414.49 psia. Also, the average pressure for Well-2, layer H is not calculated because there is no rate contribution from this layer, and the maximum average pressure was calculated in layer G, which is about 2606.26 psia. It is also found that the presence of cross flow has no effect on SIP calculations.

Investigation of the Formation and Further Development of Longitudinal Disturbances and Their Secondary Instability on the Flying Wing Model

Detailed investigation of two-dimensional roughness element influence on the flow behind three-dimensional roughness element was carried out. For the first time studies were conducted on the windward side of the flying wing in the range of free-stream 7,2 – 20 m/s in the favourable gradient region behind roughness elements. Secondary instability mechanisms of disturbances leading to turbulence stage were investigated. It was shown that longitudinal structure forming behind three-dimensional roughness element grows downstream and has its trajectory slightly bend. The longitudinal structure consists of two stationary disturbances different in size. This can be explained by presence of cross flow and secondary disturbances leading to the transition. On the straight wing model, influence of the distributed suction on the stationary disturbance development was investigated and quantitatively determined. It was shown that suction is able to relaminarize the flow and eliminate the separation of the boundary layer.

Numerical simulation of water shut-off performance for heterogeneous layered oil reservoirs

This paper proposes a hydrodynamic model of two-phase three-component fluid filtration in a layered heterogeneous reservoir that takes into account cross-flows between layers and allows prediction of the process of oil displacement by water under conditions of water shut-off near injection and production wells. The numerical calculations show that, in the absence of cross-flow between layers, the oil recovery factor for the entire reservoir is higher with water shut-off near the injection well than with water shut-off near the production well, and this effect grows as the water cut of the high permeability layer decreases. In the event of cross-flow across layers, the oil recovery factor in the entire reservoir is higher with water shut-off near the production well than with water shut-off near the injection well, and this impact grows when water cut in the high-permeability layer decreases. In the absence of crossflow, the gel washout time during water shut-off in the region of both injection and production wells is substantially longer than in the presence of crossflow. Keywords: hydrodynamic model; water shut-off; oil reservoir; gel; well.

DYN3D and CTF Coupling within a Multiscale and Multiphysics Software Development (Part II)

Traditionally, the complex coupled physical phenomena in nuclear reactors has resulted in them being treated separately or, at most, simplistically coupled in between within nuclear codes. Currently, coupling software environments are allowing different types of coupling, modularizing the nuclear codes or multi-physics. Several multiscale and multi-physics software developments for LWR are incorporating these to deliver improved or full coupled reactor physics at the fuel pin level. An alternative multiscale and multi-physics nuclear software development between NURESIM and CASL is being created for the UK. The coupling between DYN3D nodal code and CTF subchannel code can be used to deliver improved coupled reactor physics at the fuel pin level. In the current journal article, the second part of the DYN3D and CTF coupling was carried out to analyse a parallel two-way coupling between these codes and, hence, the outer iterations necessary for convergence to deliver verified improved coupled reactor physics at the fuel pin level. This final verification shows that the DYN3D and CTF coupling delivers improved effective multiplication factors, fission, and feedback distributions due to the presence of crossflow and turbulent mixing.

Flow Field and Heat Transfer of an Impinging Synthetic Jet in the Presence of Cross-Flow: Application of SAS and DES Approaches

Nowadays, synthetic jets have various applications such as cooling enhancement and active flow control. In the present paper, the capability of two turbulence modelling approaches in predicting thermal performance of an impinging synthetic jet is investigated. These two approaches are scale adaptive simulation (SAS) and detached eddy simulation (DES). Comparisons between numerical data and experimental studies reveal that the ability of DES in predicting the asymmetrical trend of heat transfer profiles is better than SAS in almost all the study cases. Although, near the stagnation zone, the performance of SAS is superior. Results show that the effects of parameters such as frequency, cross-flow velocity and suction duty cycle factor are well predicted by both approaches. An increase of cross-flow velocity from 1.81 m/s to 2.26 m/s results in an improvement of [Formula: see text] near the stagnation point by almost 16.3% and 9.2% using DES and SAS, respectively.

Influence of sub boundary layer vortex generator height and attack angle on cross-flows in the hub region of compressors

It has been recently shown that Sub Boundary layer Vortex Generator (SBVG, abbreviated as VG hereafter) can suppress the Cross-Flow (CF), and therefore, can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages. However, when VGs are applied in high-load compressors, it is difficult to achieve ideal results. This is because the definition of the VG attack angle in the presence of CF in existing research is confusing, and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle. Therefore, this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate. The differences in the flow phenomena around a VG both with and without CF are also studied. The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect. However, the cross velocity increases when surmounting the primary vortex induced by the VG, except that this enhanced CF is less conspicuous for larger VG heights. Compared to the cases without CF, the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF.

Effect of Guide Vane on Turbulence Characteristics for Single-Phase Flow through a 90-Degree Pipe Bend

The present study expresses the turbulent flow characteristics through a 90° pipe bend using a numerical ‎method by determining the solutions for Reynolds Averaged Navier-Stokes (RANS) expression using the k-ω ‎‎(SST) turbulence model. For that purpose, numerical analysis has been carried out by solving RANS equations ‎using ANSYS FLUENT 16.2, considering incompressible fluid in turbulent flow conditions. Simulations have ‎been carried out for three different Reynolds number ranging from 1×105 to 10×105 at three different bend ‎curvature ratios (Rc/D = 1, 1.5, and 2). Pipe bends with guide vane are generally used where flow separation ‎and space problem makes an issue in mechanical design. The presence of guide vane inside the bend ‎positively suppressed the flow separation and presence of cross-flow which can cause the engine to run off ‎design, thus reducing the engine efficiency. So, to observe the effect of guide vane and its position on ‎turbulence characteristics, four different positions of guide vane inside the bend are considered in the present ‎study. At first, an analysis was led to make sure that the results obtained from the present numerical model are ‎reliable and in line with previous results obtained from similar published experiments and numerical work. ‎Research has been conducted to find out the impact of Reynolds number, bend curvature ratio and position of ‎guide vane on different turbulence characteristics namely; turbulent kinetic energy, turbulent intensity, and ‎wall shear stress at bend outlet position. In general, the turbulent intensity is found larger for the lower bend ‎curvature ratio at the inner wall curvature side. Results for turbulent kinetic energy have similarities in results ‎with turbulent intensity. Significantly, the wall shear stress represented a strong dependency on the ‎circumferential angle at the bend outlet cross-section, and curvature ratio rather than Reynolds number and ‎guide vane positions‎‎.

Taylor dispersion in the presence of cross flow and interfacial mass transfer

A solute flowing in a pressure-driven channel flow experiences an enhanced effective axial dispersion coefficient due to the transverse velocity gradients. An investigation shows how this phenomenon, known as Taylor dispersion, is affected by cross flow and mass transfer at the wall.

Interpretation of interwell chemical tracer tests in layered reservoirs with limited crossflow

This paper presents a systematic approach to evaluate limited crossflow between layers of a stratified reservoir using interwell chemical tracer test. Previous analytic studies either entail no cross-flow between layers or assumes an established vertical equilibrium across transverse direction (owing to viscous/capillary/gravity driving mechanisms); however, they fail to detect the presence of limited crossflow between layers through a “bridge”; ‘bridge’ in this study is defined as a pathway through which crossflow takes place with an adjacent layer. Obviously, crossflow may take place through several bridges along a layer. A new formulation is developed to study and detect the limited crossflow. The presence of crossflow is confirmed by a zero-sum change of fraction of total fluid flowing through system layers. We employed both numerical simulation and field examples to verify the proposed method. A transition period is identified during which the fraction of fluid flowing through each layer significantly changes because of crossflow. Our results indicate that tracer test data can be used to evaluate number of bridges and possibly their location(s) along the layer. Identification of crossflow between layers and evaluation of transition zone significantly improves the current efforts to understand reservoir heterogeneity and sweep efficiency. It is expected that the outcome of this research can help design much successful EOR processes.

Interpretation of interwell tracer tests using discrete fracture model

Well-to-well tracer tests are used for getting knowledge about the flow behavior in the reservoir. The results of interpretation of these tests are especially important when enhanced oil recovery techniques that use expensive fluids such as surfactants, micellar fluids, or polymers are modeled. The classical method of quantitative interpretation assumes that the tracer filtration channels are completely isolated from the formation. In this paper, an alternative method for interpreting the results of well-to-well tracer tests is proposed. High-permeability channels are represented as discrete fractures that connect producing and injection wells. A numerical solution of the convective transport equation is used for modeling the tracer flow. The flows between the fracture and the reservoir are fully resolved, so the above-described drawback of the classical technique is overcome. The interpretation is carried out by constructing a reservoir model and determining the model parameters by solving the inverse problem. The model is verified, the well-posedness of the inverse problem is analyzed, and the comparison of the method with the classical interpretation method is performed. Using two fractures as an example, it is shown that the quasi-solution of the inverse problem exists and continuously depends on the input data. The interpretation results with this method are shown to be similar to the results of the classical interpretation in the absence of crossflows between the fracture and the reservoir. It was found that the presence of crossflows can increase the estimated fracture volume by 200 or more times. It is also shown that the crossflows between the fracture and the formation can completely prevent water breakthrough along the fracture into the production well.

Determination of the transfer coefficients of natural turbulence occurring near the solid-propellant gasification zone. II. hydrodynamic instability in the presence of cross-flow

A solution is obtained to the problem of determining the conditions of hydrodynamic stability in the presence of flow of gaseous combustion products over the propellant gasification surface. The cross-flow has a small gradient along the direction of motion. Analysis of the obtained dispersion equation shows that hydrodynamic instability with oscillations develops. The transfer coefficients of natural turbulence are represented as the sum of two terms: the first is responsible for the transfer in the absence of cross-flow, and the second takes into account the enhancement of transport processes in the case of cross-flow. Their dependence on the initial temperature of solid propellant combustion predicts a reduction in the negative erosion effect in accordance with experimental data. Accounting for the relaxation time of the evaporation process has a stabilizing effect. In the limit of strong relaxation, this leads to oscillatory stability (in the absence of crossflow) where the perturbations neither grow nor decay. However, arbitrarily weak cross-flow leads to instability.

Three-Dimensional Study of Multiple-Jet Cross Flow Cooling System with Single Array of Heat Sources

ABSTRACTThe objective of this study is to predict fluid flow and thermal characteristics associated with forced convection cooling of an array of heat sources mounted in a three-dimensional duct by impinging jets in the presence of cross flow. The equations governing fluid flow and heat transfer are solved using Streamline Upwind / Petrov - Galerkin based finite element method. The role of three dimensional flow structures, horseshoe vortex and counter rotating vortex pair in overall heat transfer distribution is examined. A parametric study is performed to analyze the performance of jets in cross flow for various Reynolds numbers (Re = 100, 250, 500) and velocity ratios (VR = 1.0, 5.0, 10.0). It is observed that with the increase in velocity ratio, the enhancement of heat transfer from heat sources occurs due to increase in the dominance of jet flow accompanied by an unfavorable reduction in heat transfer owing to the increase in size of horseshoe vortex. From numerical studies, it can be concluded that VR = 5.0 exhibits higher overall surface averaged Nusselt number (51.7% over VR = 1.0 and 44.1% over VR = 10.0 for Re = 500) compared to other velocity ratios considered in this study.

Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in the presence of cross flow

Experimental tests are carried out to investigate the convective heat transfer performances on a flat surface around the vibration envelope of a vertically-oriented piezoelectric fan in the presence of cross flow. Distinct behaviors of convective heat transfer are illustrated under the present conditions of piezoelectric-fan excitation voltage (U = 50, 150, 250 V) or characteristic velocity (u PF = 0.83, 1.67, 2.34 m/s) fan tip-to-heated surface gap (G = 3, 5, 7 mm) and cross flow velocity (u CH = 0.94, 1.56 m/s). In addition, three-dimensional flow field simulations are conducted to illustrate the instantaneous flow fields around the vibrating fan. By comparing with the pure piezoelectric fan, the vortex induced by the vibrating fan is pushed downward by the cross flow and a series of vortices are displayed down the vibrating fan. It is confirmed that the presence of cross flow is contributive to the improvement of convective heat transfer in the rear zone downstream fan vibration envelope. The impingement role of streaming flow induced by piezoelectric fan is reduced by the presence of cross flow in the fan vibration envelope. On the other hand, the oscillating movement of the piezoelectric fan promotes the disturbance intensity of cross flow passing through the fan vibration envelope. These two aspects make the conjugated convective heat transfer in the vicinity of fan vibration envelope complicated. In general, the convective heat transfer in the vicinity of fan vibration envelope is mostly improved by the combined action of fan-excited steaming flow and cross flow in the situation where the piezoelectric fan is placed very close to the heated surface.

Linear development of controlled disturbances in the supersonic boundary layer on a swept wing at Mach 2

Experimental results are presented on the linear development of a wave train in a three-dimensional supersonic boundary layer on a swept wing with 45°-sweep angle at Mach number M = 2.0. Artificial disturbances in the boundary layer were excited by periodical glow discharge mainly at frequencies 10 and 20 kHz. The maximum of the controlled pulsation amplitude was localized in the boundary layer in normal to the swept-wing surface direction for spatial amplitude distributions as well as for the amplitude wave spectra. The asymmetry of the wave characteristics of the unstable disturbances in the boundary layer of a swept wing caused by the presence of crossflow is confirmed. The stability characteristics, including dispersion relations and amplification rates over a wide range of wave inclination angles, are obtained for disturbances with prescribed frequencies 10 and 20 kHz.

Peclet number analysis of cross-flow in porous gas diffusion layer of polymer electrolyte membrane fuel cell (PEMFC).

Adoption of hydrogen economy by means of using hydrogen fuel cells is one possible solution for energy crisis and climate change issues. Polymer electrolyte membrane (PEM) fuel cell, which is an important type of fuel cells, suffers from the problem of water management. Cross-flow is induced in some flow field designs to enhance the water removal. The presence of cross-flow in the serpentine and interdigitated flow fields makes them more effective in proper distribution of the reactants on the reaction layer and evacuation of water from the reaction layer than diffusion-based conventional parallel flow fields. However, too much of cross-flow leads to flow maldistribution in the channels, higher pressure drop, and membrane dehydration. In this study, an attempt has been made to quantify the amount of cross-flow required for effective distribution of reactants and removal of water in the gas diffusion layer. Unit cells containing two adjacent channels with gas diffusion layer (GDL) and catalyst layer at the bottom have been considered for the parallel, interdigitated, and serpentine flow patterns. Computational fluid dynamics-based simulations are carried out to study the reactant transport in under-the-rib area with cross-flow in the GDL. A new criterion based on the Peclet number is presented as a quantitative measure of cross-flow in the GDL. The study shows that a cross-flow Peclet number of the order of 2 is required for effective removal of water from the GDL. Estimates show that this much of cross-flow is not usually produced in the U-bends of Serpentine flow fields, making these areas prone to flooding.

Turbulent Boundary Layer Synthetic Jet Interaction: Slot Inclination Effects

The present paper deals with synthetic jet actuators. The synthetic jet actuator is a low power, highly compact fluidic system and efficient to control a boundary layer. In this study, the development of synthetic jet is first analysed and characterized then its interaction with boundary layer along a flat plate is studied. The designed actuator is used in a wind tunnel. Different inclinations of the jet are investigated for a fixed forcing frequency (60 Hz). Both hot wire anemometer and the Particle Image Velocimetry (PIV) are used. First, the synthetic jet normal to the wall without cross flow is characterised. The inclination effect is then examined. The same situations are studied in presence of cross flow. For the normal jet, the PIV results show a decrease of the mean wall velocity. The phase-averaged velocity profiles revealed that spanwise large-scale vortices are generated downstream of the slot and persist farther downstream. The inclination of the synthetic jet has an important effect on the expansion of the jet. It has been observed that the interaction with the wall modify strongly this expansion. The modification induced by the jet angle variation will be analysed in details in this paper. We will focus on the wall behaviour.

Investigation of aerodynamics of a recessed rectangular slot-burner used in tangentially-fired furnaces by varying jet velocity ratio in the presence of cross-flow

The power generation industry throughout the world stands to gain significantly from process improvements and optimization which can potentially lead to cleaner production of cost effective electricity. The efficient operation of lignite-based tangentially-fired combustion systems, as commonly used in Victoria, Australia, depends on critical issues such as ignition and combustion of the fuel, which are largely controlled by burner aerodynamics. The geometry of the burner and the ratio of velocities between the primary and secondary jets play an important role in achieving stable combustion, high burnout of fuel, low production of pollutants and control of fouling. Slot-burners are vertically aligned stacks of rectangular nozzles delivering primary fuel and secondary air jets, and are commonly used in tangentially-fired boilers. To obtain a better understanding of the overall combustion process, it is important to understand the aerodynamics of jet development from these burners. This paper reports an experimental investigation into the aerodynamics of a recessed rectangular slot-burner of the type used in the Yallourn stage-2 tangentially-fired furnace. The 1:15 scale model burner consisted of a central (primary) rectangular fuel nozzle with two secondary rectangular air jets positioned above and below it. The burner jets were at an angle of 60° to the wall and were diffused and mixed in a recess before entering into the measurement vessel. A cross-flow jet was attached to the wall of the vessel to simulate the recirculation similar to tangentially-fired furnaces. Experiments for both single and two-phase flow were performed. For single-phase flow, the air flow was seeded with a fine mist of sugar particles (mean diameter 1μm) introduced into the primary, secondary and cross-flow ducts. For two-phase flow, solid glass spheres (mean diameter 66μm, density 2450kg/m3) were used as the representative of the coal particles and were introduced only at the centre of the primary duct from a bubbling fluidized bed. Experiments were conducted using a primary to cross-flow jet velocity ratio (φ) of 1.0 and secondary to primary jet velocity ratios (ϕ) of 1.0 and 3.0 as found in real furnaces. Laser Doppler Anemometry (LDA) was used to measure mean and turbulent velocity components in the near field and downstream regions of the jets. The flow pattern inside the recess was very complex and greatly influenced the flow where it entered the measurement vessel. For single-phase flow and ϕ=1.0, the jets diverged completely from the geometric axis of the burner and attached to the wall. The degree of deflection of the lower secondary jet was slightly more than the primary jet. For ϕ=3.0, after exiting from the nozzle, the primary jet diffused outwards and mixed with the higher momentum secondary jets in the recess and came out with the secondary jets. For two-phase flow and ϕ=1.0, in the mixing region between the primary and cross-flow jet, the gas-phase velocities were higher than the particle-phase. Further downstream the peak velocities of the particle-phase slightly deviated and occurred farther from the wall. For ϕ=3.0, downstream of the nozzle there was a tendency of separation for the gas-phase near the wall while the particle-phase was attached to the wall.

Stability of Flow Past Alternate Rigid and Porous Panels in Boundary Layer Flow and in Channel Flow

Propagation of two-dimensional small amplitude Tollmien-Schlichting (TS) waves has been investigated over a rigid panel followed by a porous panel in the presence of cross-flow. In the present work boundary layer flow over alternate rigid-porous panels in which suction is applied through the porous panel is investigated.Also investigated is the problem of flow past alternate rigid and porous panels with cross flow. A general space marching solution has been discussed for calculating the mean velocity profile for the above case, in the developing region of mean flow in the porous panel, following the rigid-porous junction. Numerical solutions are obtained using a finite difference method for the suitably simplified Navier Stokes equations, using appropriate boundary conditions.Detailed two-dimensional analyses have been done for the disturbance waves using both the quasi-parallel (QP) approximation, and more accurately, using the non-parallel (NP) approach. The non-parallel approach has been carried out over the developing mean-flow region of the porous panel, following the rigid-porous junction.Numerical solutions have been obtained by finite difference procedures. In some of the cases results have been validated with the available literature. Finally, the jumps in the amplitude of the disturbance waves across the rigid- porous junction were calculated using the theory of Sen et al.[6].The important outcome from this work is in optimizing the length of the porous panel, following the rigid-porous junction. It is seen that, as compared to the length required to approach the asymptotic mean flow state to within 99%, only a very short porous panel length is sufficient to stabilize the disturbances.Hence, it is foreseen that alternate long rigid panels, with in-between short porous panels, could be a very effective way of stabilizing the disturbances, and thus delaying laminar to turbulent transition.