Radial Jet Research Articles

CFD modelling of flow and mixing characteristics for multiple rows jets injected radially into a non-reacting crossflow

CFD parametric study was done of flow and mixing characteristics of coolant radial jets injected outwardly from a centerline multiple rows diffuser into a heated non-reacting crossflow in a cylindrical chamber in three-dimensional model using ANSYS-FLUENT 14.5. The effects of jet-mixing ratio, nozzles diameter, diffuser diameter, number of nozzles rows number of nozzles per row on the penetration depth and mixing quality through chamber cross section were parametrically studied. The simulation results were validated with the available experimental data and good agreement was obtained. The results showed that the nozzle diameter, the diffuser diameter and the jet-mixing ratio have remarkable effects on the penetration depth and the mixing quality compared to the effects of number of nozzles per row and the number of nozzle rows. The penetration depth at downstream, the jet diffuser exit and the mixing quality at centerline of chamber exit are increased ≅46% & ≅49%, respectively, with increasing the jet-mixing ratio from 0.1 to 0.5. Dimensionless correlations in terms of the studied parameters for predicting the penetration depth, mixing quality and maximum temperature difference were developed and presented.

О механизме автоколебаний сверхзвуковой радиальной струи, истекающей в затопленное пространство

О механизме автоколебаний сверхзвуковой радиальной струи, истекающей в затопленное пространство

The flow external to a rotating torus

Imparting a sudden rotation to a torus (or other symmetric smooth object) in an otherwise quiescent, viscous fluid serves to generate boundary layers at the object’s surface. These boundary layers are known to exhibit a finite-time singularity at the equator which manifests in a thickening of the boundary layer and subsequent development of an equatorial jet. Here we consider the post-collision flow dynamics, demonstrating that the equatorial jet serves to shed a finite amplitude toroidal vortex pair. The radial jet is also shown to develop an absolute instability at suitably high Reynolds numbers.

Study and application of a high-pressure water jet multi-functional flow test system.

As the exploration and development of oil and gas focus more and more on deeper formation, hydraulic issues such as high-pressure water jet rock breaking, wellbore multiphase flow law, cuttings carrying efficiency, and hydraulic fracturing technique during the drilling and completion process have become the key points. To accomplish related researches, a high-pressure water jet multi-functional flow test system was designed. The following novel researches are carried out: study of high-pressure water jet characteristics under confining pressure, wellbore multiphase flow regime, hydraulic pressure properties of down hole tools during jet fracturing and pulsed cavitation jet drilling, and deflector's friction in radial jet drilling. The validity and feasibility of the experimental results provided by the system with various test modules have proved its importance in the research of the high-pressure water jet and well completion technology.

Gas dynamics of a supersonic radial jet. Part I

The paper presents the radial distributions of the pressure measured with a Pitot tube for the case of a radial jet with/without swirling of the input flow in the pre-chamber; the length of the supersonic part of the jet, dependency of the jet thickness as a function of the distance from the nozzle outlet, and approximating analytical formula for the jet thickness that generalizes the experimental data. Experimental data demonstrated that at the deposition distances lower than 4-6 gauges from the nozzle outlet, the solid particle velocity and temperature are almost uniform over the jet cross section. This means that the target surface can be allocated here without loss in coating quality and deposition coefficient. The maximal recommended distance where the deposition is still possible is the length of l s0 ~ 16 gauges.

Experimental investigation on turbulence modification in a dilute gas-particle axisymmetric opposed jets flow

Turbulence modifications in an axisymmetric opposed jets flow are experimentally investigated by means of a simultaneous two-phase PIV measurement technique. The measurements are conducted at a Reynolds number of 14,500. Glass beads with an averaged diameter of 100μm (corresponding to a Stokes number of 59.5) are used as dispersed phase. Relatively low mass loading ratios (0.04) and large nozzle separation (12 times nozzle diameter) are tested. It is found that the presence of the particles can distinctly modify the gas-phase characteristics, including both macroscopic turbulence statistics and mesoscopic turbulence structures. In the present dilute gas-particle opposed jets flow, inter-particle collision can be neglected, and particles can penetrate into the opposite stream until to the vicinity of the opposite nozzle. The penetrating and counter-moving particles bring about a lower particle velocity and a larger relative velocity between gas- and particle-phase, which result in a more noticeable modulation of opposed jets. The presence of particles decreases the time-averaged velocity of the opposed jets, increases the turbulence in the axial jet and suppresses the transfer between gas reactants in the impingement region. Moreover, the presence of particles also significantly modifies the axial jet structures, representing the coherent vortex elongating in streamwise direction and shortening in transverse direction, meanwhile noticeably suppresses the turbulence kinetic energy transport from the axial jet to the radial jet.

섬광 X선과 잔류관통깊이 분석을 통한 성형작약탄 제트에 대한 펄스전류 효과

In this paper, the effect of high voltage current pulse against shaped charge jet was analyzed through the visualization of jet behavior using flash X-ray and comparison of depth of penetration(DOP) into RHA(Rolled Homogeneous Armor) witness plates. The behavior of jet particles has been acquired using a flash X-ray equipment when current pulse was applied into the metal jet of a shaped charge(SC) warhead. Typical results such as jet breakup and radial jet dispersion, which are due to electromagnetic pressure by current pulse, have been obtained. Dozens of penetration experiments using a shaped charge with 55 mm diameter were performed according to various combinations of major parametric variables such as electrode spacing, standoff distance from SC warhead to electrode, and charge voltage. Subsequently, interrelations between major parametric variables and DOPs into RHA were analyzed.

The unsteady flow due to an impulsively rotated sphere

We consider the flow induced by a sphere, contained in an otherwise quiescent body of fluid, that is suddenly imparted with angular momentum. This classical problem is known to exhibit a finite-time singularity in the boundary-layer equations, due to the viscous boundary layer, induced by the sudden rotation, colliding at the sphere's equator. We consider this flow from the perspective of the post-collision dynamics, showing that the collision gives rises to a radial jet headed by a swirling toroidal starting vortex pair. The starting vortex propagates away from the sphere and, in doing so, loses angular momentum. The jet, in turn, develops an absolute instability which propagates back towards the sphere's equator. The starting vortex pair detaches from the jet and expands as a coherent (non-swirling) toroidal vortex pair. We also present results of some new experiments which show good qualitative agreement with our computational results.

On jet structure in heavy ion collisions

The LHC data on jet fragmentation function and jet shapes in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted in the frameworks of PYQUEN jet quenching model. A specific modification of longitudinal and radial jet profiles in most central PbPb collisions as compared with pp data is close to that obtained with PYQUEN simulations taking into account wide-angle radiative and collisional partonic energy loss. The contribution of radiative and collisional loss to the medium-modified intra-jet structure is estimated.

Steady and unsteady modelling of the float height of a rotating air hockey disk

A similarity reduction of the Navier–Stokes equations for the motion of an infinite rotating disk above an air-bearing table yields a coupled pair of ordinary differential equations governed by a Reynolds number $Re=Wh/{\it\nu}$ and a rotation parameter $S=\sqrt{2}h{\it\Omega}/W$, where $h$ is the float height, $W$ is the air levitation velocity, ${\it\Omega}$ is the disk rotation rate, and ${\it\nu}$ is the kinematic viscosity of air. After deriving the small- and large-Reynolds-number behaviour of solutions, the equations are numerically integrated over a wide range of $Re{-}S$ parameter space. Zero-lift boundaries are computed as well as the boundaries separating pure outward flow from counter-flow in the gap. The theory is used to model the steady float height of a finite-radius air hockey disk under the assumption that the float height is small relative to the diameter of the disk and the flow is everywhere laminar. The steady results are tested against direct numerical simulation (DNS) of the unsteady axisymmetric Navier–Stokes equations for the cases where the disk rotates at constant angular velocity but is either at a fixed height or free to move axially. While a constant shift in the gap pressure conforms closely to that found using steady theory, the interaction of the radial jet emanating from the gap with a vertical transpiration field produces vortex rings which themselves propagate around to interact with the jet. Although these structures diffuse as they propagate up and away from the gap, they induce a departure from the steady-flow assumption of atmospheric pressure at the gap exit, thus inducing small irregular axial oscillations of the floating disk.

Maximum drillable length of the radial horizontal micro-hole drilled with multiple high-pressure water jets

Radial horizontal jet drilling technology is designed to provide multiple lateral micro-holes to enhance petroleum production by using high-pressure water jets to break the rock formation. The micro-hole length is a key parameter in this technology, and it has a significant influence on the design of drilling operation and petroleum production. This paper presents a model for calculating the maximum drillable micro-hole length by combining a theoretical analysis and experimental methods. The pressure loss of the circulation system, the pressure and flow rate of the pump, and the self-propulsion effect of the multiple-jet nozzle are included in the model. The results indicate that the flow rate is the dominant factor in the radial horizontal jet drilling process, and a high flow rate contributes to the creation of long micro-holes. The jetting force generated by multiple water jets is the only propulsion used to elongate the micro-hole. However, the friction of the flexible hose moving in the diverter and micro-hole is the main resistance limiting the length of the micro-hole. A comparison of this model with a field case result indicates that the model is sufficiently accurate for predicting the maximum drillable length of the micro-hole. The model and results presented in this paper can provide guidelines for the design of radial horizontal jet drilling operations.

Measurement of charged jet production cross sections and nuclear modification in p–Pb collisions at [formula omitted

Charged jet production cross sections in p–Pb collisions at sNN=5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-kT algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R=0.2 and R=0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, RpPb, of charged jets in p–Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at s=7 TeV. In the transverse momentum range 20≤pT,chjet≤120 GeV/c, RpPb is found to be consistent with unity, indicating the absence of strong nuclear matter effects on jet production. Major modifications to the radial jet structure are probed via the ratio of jet production cross sections reconstructed with the two different resolution parameters. This ratio is found to be similar to the measurement in pp collisions at s=7 TeV and to the expectations from PYTHIA pp simulations and NLO pQCD calculations at sNN=5.02 TeV.

Pressure Loss in a Cylindrical Duct with Sudden Section Enlargement During Intake of Radial Gas Jets into an Axial Cross-Flow

Results are presented for experimental investigations of pressure loss in a cylindrical duct with sudden section enlargement and interaction between an axial gas cross-flow and several rows of radial gas jets. The influence exerted by basic structural parameters, and also the velocities of the axial cross-flow and jets on hydraulic characteristics of the process is examined.

A numerical investigation on heat transfer and emissions characteristics of impinging radial jet reattachment combustion (RJRC) flame

Radial Jet Reattachment combustion (RJRC) flame jet is used in applications where the impingement surface is delicate and demands low impingement pressure. In the present study, a two dimensional axisymmetric computational fluid dynamics (CFD) simulation is carried out. The turbulence–combustion interaction in the flame field is modeled in a k−ε/EDM framework. The distribution of heat flux, pressure coefficient and emissions is presented for varying Reynolds number (Re = 1000 to 30,000) and different non-dimensional nozzle tip to plate spacing (X/R = 0.5 to 3). It is found that the peak heat flux increases and pressure coefficient reduces significantly with the increase in Reynolds number. However, with the increase in the nozzle tip to plate spacing the peak heat flux and the pressure coefficient decrease. Furthermore, the concentrations of NOx and CO emissions increase with the increase in Reynolds number and the distance of the location of the nozzle tip from the impingement plate.

Experiment research on the rock blasting effect with radial jet cracker

Due to the low efficiency problem of cut blasting in rock drivage, a new type of jet cracker is invented. There are three development stages of this new type of radial jet cracker, and each stage has its corresponding experiment, and optimal design will be carried out based on the problems of the previous stage, but experimental principles of these radial jet crackers are still the same. The main structure of the radial jet cracker is circular tube, and there are several shaped rings designed on it, which not only can reduce charge quantity but also raise the utilization ratio of explosive energy. Experimental results show that, with this cracker, the utilization ratio of blasting hole is 98%, and the blasting efficiency and the length of cyclical footage had been improved.

Experimental and numerical study of a small-scale and low-velocity indoor diffuser for displacement ventilation: Isothermal floor

The accurate knowledge of the dynamics and heat transfer of an attached cool radial jet in a laminar regime, discharging onto an isothermal floor and undisturbed atmosphere, is crucial to better control the parameters and reach a comfortable environment. In the present study, we first analyze a simple geometry of a small-scale, indoor displacement ventilation diffuser, by means of flow visualizations, and the PIV technique. In addition, we have carried out axisymmetric numerical simulations that show excellent agreement with qualitative and quantitative experimental data. Finally, we provide correlations of the heat flux as a function of non-dimensional parameters, finding out that the Nusselt number has a strong dependence on the Grashof number rather than the Reynolds number in this configuration. This simple model is a relevantly simple tool for practical engineering purposes such as the conditioning of large public areas with displacement ventilation systems.

A study of cavitation in a vortex generator of flow-through type

The results of experimental study of cavitation in a vortex generator of flow-through type are presented. It is shown that when high-pressure tangential or radial jets are injected into a generator chamber a cavitation develops in it. The most intense cavitation processes occur in the bottom region. The cavitation intensity in this part of the generator depends significantly on the kind of the jets, the locations of the jet injection relative to the bottom, the geometry of the flow-through section, and the pressures at the inlet and outlet of the generator.

Sensitivity study with respect to direction of ADI method during re-flooding in AHWR

Abstract The Advanced Heavy water Reactor (AHWR) is a natural circulation vertical pressure tube type boiling light water cooled and heavy water moderated reactor. As the AHWR fuel bundle quenching under accident condition is designed primarily with radial jets at several axial locations, bottom re-flooding still remain open as another option. Radial direction injection of emergency core cooling leads to rewetting of AHWR fuel cluster in circumferential direction. A 3D fuel pin model has been developed by using Finite Difference Method (FDM) of transient heat conduction equation. Alternating Direction Implicit technique of Finite Difference Method (FDM) has been used for discretisation of numerical equation in different time step at different direction. Sensitivity numerical study with respect to direction of ADI method has been carried out to optimize the time step during the transient as well as steady state and is found that it is insensitivity with direction of solution. Further, to assess influence of circumferential rewetting vis-à-vis axial rewetting. Both the analyses are carried out with same fluid temperature and heat transfer coefficients as boundary conditions. It has been found from the analyses that for radial jet, the circumferential conduction is significant and overall the fuel temperature falls in the quench plane with the initiation of quenching event. The paper discusses the sensitivity study with respect to direction of ADI solution and comparison of numerical results for circumferential and axial rewetting for single pin.

The self-propelled force model of a multi-orifice nozzle for radial jet drilling

Radial jet drilling (RJD) is an effective method for the stimulation, exploration, and development of oil and gas resources. The multi-orifice nozzle is a type of highly efficient nozzle applied in RJD. It generates the self-propelled force to pull a connected hose moving forward to form a radial hole. However, there are few studies on the self-propelled ability of the nozzle, and there is no model for the calculation of the self-propelled force. This paper developed a convenient model to calculate the self-propelled force and defined a factor to represent the self-propelled ability of the nozzle. The proposed model was validated by means of experiment and numerical simulation. To achieve a stronger self-propelled ability, we investigated the effects of the number, angle, and diameter of the orifices on its self-propelled ability. The results show that the forward orifices exert a negative effect on the self-propelled ability, whereas their angles present a positive effect. With an optimal angle, the backward orifices primarily generate the self-propelled force. Although an enlarged orifice diameter can improve the performance of the nozzle, it still has an optimal value for the limitation of flow rate and jet pressure. This study provides a reference for the design of multi-orifice nozzles and hydraulic parameters for radial jet drilling technology.

Interaction of inner and outer layers in plane and radial wall jets

Large eddy simulations of turbulent radial and plane wall jets were performed at different Reynolds numbers using the Lagrangian dynamic eddy viscosity subgrid-scale model. The results were validated with experimental data available in the literature. Compared to the plane ones, the radial wall jets have an extra direction for expansion, which causes faster decay rates. Thus, the resulting pressure gradient distributions are different. However, the comparison of the results with the turbulent boundary layers under adverse and favourable pressure gradients reveals that these pressure gradients are not strong enough to cause any fundamental physical difference between plane and radial wall jets. In both cases, the local Reynolds number is an important determining factor in characterisation of the flow. The joint probability density function analysis shows that the local Reynolds number determines the level of intrusion of the outer layer into the inner layer: the lower the local Reynolds number, the stronger is the interaction of the inner and outer layers. These results can be used to clarify the scatter of the reported log-law constants in the literature.