Jet Penetration Length Research Articles

Optical diagnostics on the pre-chamber jet and main chamber ignition in the active pre-chamber combustion (PCC)

We studied the relationship between pre-chamber jet and main chamber ignition in the pre-chamber combustion (PCC) of an optical engine, fueled with methane and equipped with an active pre-chamber with two rows of orifices. Acetone planar laser-induced fluorescence (PLIF) and OH* chemiluminescence imaging techniques were simultaneously applied to visualize the pre-chamber jet and the reaction zone in the main chamber, respectively. The pre-chamber fueling was constant and the main chamber fueling was increased to form an ultra-lean case and a lean case with global excess air ratios (λ) of 2.3 and 1.8, respectively. Results indicate that a higher pressure difference between pre-chamber and main chamber (▵P) produces larger pre-chamber jet penetration speed; the maximum pre-chamber jet penetration speed appears at timing around the peak ▵P. Over enrichment of the pre-chamber charge reduces the peak ▵P and thus does not favor a faster pre-chamber jet discharge. In addition to the main pre-chamber jet, a weaker post jet discharge process is visualized; the former is due to the pre-chamber combustion while the latter due to the ▵P fluctuation and the cylinder volume expansion. The post pre-chamber jet is accompanied by a post reaction zone in the ultra-lean case (λ=2.3) and there are two unburned regions in the main chamber: one is around the pre-chamber nozzle and the other between the adjacent reaction zones. These two unburned regions are consumed by flame propagation in the lean case (λ=1.8). The weak pre-chamber jet from the upper-row orifice does not produce any distinct reaction zone, indicating that the pre-chamber orifice location and arrangement on the nozzle also matters in the pre-chamber design. The pre-chamber jet penetration length is longer than that of the reaction zone during pre-chamber discharge; the penetration length difference between the pre-chamber jet and reaction zone decreases with increasing main chamber fueling.

The innovative design of air caps for improving the thermal efficiency of CFB boilers

Air caps are an effective way of ensuring uniformity of air flow in Circulating Fluidized Bed (CFB) boilers. Published literature on the design and configuration of these air caps is severely limited. In this study, extensive theoretical as well as experimental investigations have been carried out to design novel air caps in order to improve efficiency of CFB boilers. A small-scale test bench of 220 t/h CFB boiler has been developed, integrated with novel air caps. It has been observed that inhomogeneity in air flow velocity decreases from 65.79% to 21.25%, while the pressure drop decreases by 20%. A mathematic model of air caps has been derived and its accuracy verified through cold tests. Two empirical correlations for calculating the pressure drop and the air jet penetration length of the novel air caps have been obtained and verified. Finally, in order to validate the innovative design of air caps, this methodology has been implemented to a full-scale 220 t/h CFB boiler. The hot test results depict that the thermal efficiency of the boiler has increased from 86.4% to 91.8% when tested with the novel air caps in-place, which is equivalent to a saving of 6000 tons of coal per year.

Simultaneous rainbow schlieren deflectometry and OH* chemiluminescence imaging of a diesel spray flame in constant pressure flow rig

The physical and chemical phenomena that take place during fuel injection, entrainment and fuel-air mixing, cool-flame and ignition reaction, and combustion in diesel sprays still require extensive study. Global parameters such as liquid and vapor jet penetration lengths and spreading rates render useful yet still limited information. Understanding of the temporal evolution of the spray as it progresses through various steps is needed to develop advanced clean combustion modes and high-fidelity predictive models with sufficient accuracy. In this study, high-speed rainbow schlieren deflectometry (RSD) and OH* chemiluminescence are used to simultaneously image fuel-air mixing, cool-flame reactions, ignition, flame propagation and stabilization, and combustion in a transient diesel-like flame. A constant pressure flow rig (CPFR) is used to conduct multiple injections in quick succession to obtain a statistically relevant dataset. n-heptane was injected at nominal supply pressure of 1000 bar from a single-hole diesel injector into ambient at pressure of 30 bar and temperature of 800 K. About 500 injections were performed and analyzed to reveal structural features of non-reacting and reacting regions of the spray, quantify jet penetration and spreading rates, and study cool-flame behavior, ignition, flame propagation and stabilization at lift-off length, and combustion at upstream and downstream locations.

A Computational Investigation of the Effects of Particle Diameter and Particle–Particle Interactions on Jet Penetration Characteristics in a Gas–Solid Fluidized Bed with a Central Jet

Particle–particle interactions, quantified by particle–particle restitution coefficient (e) and particle diameter ( $$d_s$$ ) are two crucial parameters governing the flow hydrodynamics of dispersed gas–particle flows. In this work, a detailed numerical analysis has been carried out in order to get an insight into the effects of these two parameters on the jet penetration characteristics inside a bubbling gas–solid fluidized bed with a central jet. Specifically, the studies have been conducted to find out the effects of variations of these two parameters on the jet penetration length. It has been found that an increase in the value of particle diameter leads to a significant decrease in the jet penetration length for all other flow and physical properties remaining invariant. On the other hand, a gradual but substantial decrease in the jet penetration length has been observed with an increase in the values of e. Numerical investigations further reveal that there is no significant variation in the jet penetration characteristics for change in particle-wall interactions, quantified by the specularity coefficient ( $$\phi$$ ).

Characteristics of two-dimensional counter-flowing wall jets

Wastewater plant effluents discharged into streams are expected to undergo dilution in a short reach. Jets provide rapid mixing and enhance dilution of the effluent discharged into the stream. The counter-flowing wall jet expansion angle, the geometry of the dividing streamline and the jet penetration length were found using the measured mean axial jet velocity data. These jet characteristics were expressed in terms of the jet velocity ratio (jet exit velocity against main stream velocity). A salt solution of known concentration was injected into the jet flow. The distribution of the salt concentration was determined at several cross-sections of the jet wake using a concentration meter. The standard deviation of the salt concentration provided a measure of jet mixing. When standard deviation reached zero at a cross-section, mixing was considered to be complete.

Experimental study of submerged gas jets in liquid cross flow

Gas jets submerged in the liquid cross flow are prevalent in the nature and essential in numerous industrial applications. The interaction between the gas jet and liquid cross flow is not well characterized for the difficulties in experimental research. In the present work, a new experimental method was designed and the evolution of the gas jet in liquid cross flow was captured by the high speed camera. Five experimental cases with different initial liquid cross flow velocities (0.35 m/s, 0.7 m/s, 1.0 m/s, 1.5 m/s, 2.0 m/s) were performed where the momentum ratio of the initial gas jet to liquid cross flow varies to highlight the effects of the liquid cross flow velocity on the flow characteristics. The summation and statistical methods were adopted to analyze the experimental sequences, and the results from the two methods showed good agreement. The gas jet morphology and the gas liquid interface were clearly identified from the experimental results, which showed that the gas jet deflected in a less pronounced manner with less unsteadiness generated at the gas liquid interface as the liquid cross flow velocity decreases. The gas jet penetration length in the momentum region was measured and it was found to be severely influenced by the liquid cross flow, and a power relationship was found between the gas jet penetration length and the cross flow velocity. The expansion angle of the gas jet in the upstream was also shown to grow in a power function with the liquid cross flow velocity. The gas jet diameter indicates the ambient liquid entrainments and the gas liquid interface evolution. In the region where the gas jet momentum is dominant, the evolution of the gas jet diameter followed a similar pattern with the submerged gas jets without liquid cross flow. Finally, empirical correlations were developed to predict the characteristic parameters of the submerged gas jet in liquid cross flow.

A quantification of penetration length of steam jet condensation in turbulent water flow in a vertical pipe

An experimental research is performed to investigate the penetration length of steam jet condensation in turbulent water flow in a vertical pipe. The penetration length of the condensing jet, with steam mass velocities ranging from subsonic to supersonic, was measured via utilizing a visualization window and a high-speed camera. At low steam flow rate a steam bubble plume forms, while at relatively high flow rate the bubbles in the plume coalesce and a steam jet is produced. Quantitative analyses of the interface behavior of the condensing jet are performed by exploring the transient and statistical characteristics of the jet penetration length. The waveforms of the transient jet penetration length exhibit that in the bubbling regime the period is approximately constant, while in the jetting regime the period varies a lot. The statistical analysis of the transient jet penetration length confirms that significant variations of the power distribution function (PDF) and power spectrum density (PSD) between the bubbling and jetting regimes occur at the transonic condition. The ratio of steam mass flux to critical steam mass flux at ambient pressure is found to have good linearity with the mean of the jet penetration length. And a linear correlation is fitted with a maximum absolute deviation of 5.5% between the measured and predicted values of mean of the jet penetration length. The relative unsteadiness of jet penetration length, defined as the ratio of the standard deviation to mean of transient penetration length, is approximately invariable in the bubbling and jetting regime. The bubbling regime contains more relative unsteadiness, while the jetting regime yield less relative unsteadiness. Because absolute instability exists in the subsonic region while no absolute instability occurs in the supersonic region, the transition from the bubbling to jetting regime occurs in the transonic region.

Soot formation and flame structure in swirl-stabilized turbulent non-premixed methane combustion

The relationships between flow field, flame structure, and soot distribution were investigated experimentally in turbulent 4 kW non-premixed swirl flames of methane and air at three different air supply rates. Auto-compensating laser-induced incandescence, particle image velocimetry, OH planar laser induced fluorescence, and OH* chemiluminescence techniques were used to measure soot volume fractions and primary soot particle size, velocity fields, OH, and OH* fields, respectively. While the instantaneous values of soot volume fractions were similar among the flames, the time-averaged soot volume fraction decreased by nearly a factor of three for a 7% increase in the air flow rate due to increased soot intermittency. Peak soot volume fractions occurred between two shear layers caused by the central fuel jet injection, recirculation zone, and swirling air jet interfaces. The decrease in soot towards the air side corresponded to locations with elevated OH, demonstrating its role in soot oxidation. The velocity measurements showed that engulfing the jet through a stronger recirculation rate induced by the higher air velocity enhanced the turbulent mixing between the recirculating fluid and fuel jet, and led to a shorter fuel jet penetration length. The reduction in soot volume fraction with air flow rate therefore is associated with greater turbulent mixing and higher oxidation rate in the recirculation zone. In contrast, the primary soot particle size, whose range was between 30 and 60 nm, did not show a dependence on the air flow rate. These results highlight the sensitivity of soot processes to fluid mechanics under turbulent conditions.

An Analysis of Turbulent Mixing Effects on the Soot Formation in High Pressure n-dodecane Sprays

An n-dodecane spray flame, known as Spray A, is simulated under the diesel engine conditions. The simulations are based on the well-mixed assumption where the turbulence-chemistry interactions are ignored, and employ the semi-empirical multi-step Moss-Brookes soot model coupled with the Reynolds-averaged turbulence model and a Lagrangian discrete phase spray model. A 54-species reduced n-dodecane chemical mechanism is employed in all simulations to evaluate the reaction rates. The importance of the turbulent mixing on the soot formation is analysed using three different turbulent Schmidt numbers; Sct = 0.7, 1.1 and 1.4. The non-reacting case is first validated using the mixture fraction and the velocity fields. It is found that the jet velocity and penetration length are unaffected by Sct for the inert case, however, the mixture fraction is sensitive to Sct where Sct = 1.1 leads to an excellent agreement with the measurements. Reacting simulations are compared with experimental data in terms of the ignition delay and the flame lift-off length. The results confirm the ignition delay time is marginally affected by changes in Sct. At the baseline condition, Sct = 0.7 and 1.1 result in a very similar value for the lift-off length which is in good agreement with the experiment although at higher ambient temperatures, only Sct = 0.7 agrees well with the measurements. It is found that the formation of formaldehyde and acetylene increases as the level of mixing decreases while the trend is opposite for the OH mass fraction. Consequently, with increasing Sct the soot volume fraction increases and the soot-containing region is extended. The results show that the development of the soot mass is not well captured, regardless of the value of the turbulent Schmidt number.

Experimental study on penetration characteristic of submerged steam jet in quiescent water

AbstractThe direct contact condensation is an effective way to rapid depressurization for light water reactor, such as pressure suppression pool, for which the characteristic of steam plume is a key parameter to evaluate the efficiency of depressurization. In this paper, a series of visualization experiments are described which investigate the characteristic of steam plume, the influence of jetting direction, air mass fraction, water temperature, diameter of jet on the steam plume were analyzed. The results show that, the dimensionless steam plume length increased with the increase of inlet pressure and water temperature for pure steam submerged jet, a correlation was set up to predict the dimensionless penetration length and the predicted errors were within the band of ±15%. Furthermore, the penetration length decreased with the rise of air mass fraction due to buoyancy force, the penetration length increased with the increase of inlet pressure, and the jet penetration length for vertical jet is longer than horizontal jet about 25% at the same inlet pressure and air mass fraction.

LES and RANS modelling of under-expanded jets with application to gaseous fuel direct injection for advanced propulsion systems

A density-based solver with the classical fourth-order accurate Runge-Kutta temporal discretization scheme was developed and applied to study under-expanded jets issued through millimetre-size nozzles for applications in high-pressure direct-injection (DI) gaseous-fuelled propulsion systems. Both large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) turbulence modelling techniques were used to evaluate the performance of the new code. The computational results were compared both quantitatively and qualitatively against available data from the literature. After initial evaluation of the code, the computational framework was used in conjunction with RANS modelling (k-ω SST) to investigate the effect of nozzle exit geometry on the characteristics of gaseous jets issued from millimetre-size nozzles. Cylindrical nozzles with various length to diameter ratios, namely 5, 10 and 20, in addition to a diverging conical nozzle, were studied. This study is believed to be the first to provide a direct comparison between RANS and LES within the context of nozzle exit profiling for advanced high-pressure injection systems with the formation of under-expanded jets. It was found that reducing the length of the straight section of the nozzle by 50% resulted in a slightly higher level of under-expansion (∼2.6% higher pressure at the nozzle exit) and ∼1% higher mass flow rate. It was also found that a nozzle with 50% shorter length resulted in ∼6% longer jet penetration length. At a constant nozzle pressure ratio (NPR), a lower nozzle length to diameter ratio resulted in a noticeably higher jet penetration. It was found that with a diverging conical nozzle, a fairly higher penetration length could be achieved if an under-expanded jet formed downstream of the nozzle exit compared to a jet issued from a straight nozzle with the same NPR. This was attributed to the radial restriction of the flow and consequently formation of a relatively smaller reflected shock angle. With the conical nozzle used in this study and a 30 bar injection pressure, an under-expanded hydrogen jet exhibited ∼60% higher penetration length compared to an under-expanded nitrogen jet at 100 μs after start of injection. Moreover, the former jet exhibited ∼22% higher penetration compared to a nitrogen jet issued through the conical profile with 150 bar injection pressure.

Experimental investigation of the flow characteristics of low-pressure drop air nozzles working with CFB boilers

The paper presents the most important flow characteristics of low-pressure drop primary air nozzles used in circulating fluidized bed boilers. The role of an air nozzle pressure drop, pressure fluctuation, as well as air jet penetration length, orifice outlet jet kinetic energy and aerodynamic drag force of the gas outlet jet have been discussed. For the purpose of cold model studies the Lagisza 966MWth supercritical CFB boiler operating at the company TAURON Wytwarzanie SA, Poland has been chosen as the reference facility. In the experimental tests, three types of primary air nozzles with comparable static pressure drop and varied aerodynamic drag force have been tested. The experiments clearly showed that the pressure drop cannot be the only parameter characterizing the operation of the primary air nozzle and the air jet penetration length is determined primarily by the orifice outlet jet kinetic energy and not by the outlet jet velocity.

Numerical simulation of flow behavior of top-gas jet in a gas-particles bubbling fluidized bed

Flow behavior of top-gas jet and particles is simulated by means of gas-solids two-fluid model incorporating the kinetic theory of granular flow (KTGF) in a top-gas jet bubbling fluidized bed. The RNG k-ε model is used to model gas turbulence of the top-gas jet. The effects of the top-jet gas velocity and fluidizing gas velocity on distributions of volume fractions and velocities of gas and particles are evaluated, and the results are quantified in terms of top-gas jet penetration length. Numerical simulations show that the fluidized gas-particle mixture along bed height is divided into three regions as (a) the top-gas jet region in the freeboard, (b) the concentrating region near the bed surface and (c) the diluting region near the bottom in terms of the axial distribution of solids volume fraction. By increasing the top-jet gas velocity, particles circulate through the down-flow at the center from the concentrating region to the diluting region and the up-flow near the walls from bottom to bed surface along bed height. The distributions of volume fraction and velocity of gas and particles considerably change with the variation of top-jet gas velocities. Moreover, the top-gas jet penetration length with the change of top-jet gas velocity and fluidizing gas velocity is identified and discussed.

The Effect of Splitting Timing on Mixing in a Jet with Double Injections

We present large-eddy simulation (LES) of a high-pressure gas jet that is injecting into a quiescent inert environment. The injection is through a nozzle with a diameter of 1.35 mm. Four injection strategies are considered in which the results of a single continuous injection case are compared with those of double injection cases with different injection splitting timing. In all double injection cases, the injection pulsing interval is kept the same, and the total injected mass is equal to that of the single injection case. On the other hand, the splitting timing is varied to investigate the effects of various injection splitting strategies on the mixture formation and the penetration length of the jet. Results show that the jet penetration length is not so sensitive to the splitting timing whereas the mixing quality can significantly change as a result of shifting the onset of injection splitting toward the end of injection. Especially, it is found that by adopting a post-injection strategy where a single injection splits into the main injection and late small injection near the end of injection period the mixing between the injected gas and ambient air is significantly improved. This trend is not as obvious when the injection splitting timing shifts toward the beginning or even in the middle of injection period. The increase of entrainment in the tail of each injection is one of the underlying physics in the mixing improvement in double injection cases. In addition to that, splitting a single injection into two smaller injections increases the surrounding area of the jet and also stretches it along the axial direction. It can potentially increase the mixing of injected gas with the ambient air.

Studies on injection and mixing characteristics of high pressure hydrogen and oxygen jet in argon atmosphere

Ar-circulated hydrogen engine replaces atmospheric nitrogen with Ar so as to increase engine efficiency and avoid NOx forming. Due to the differences in gas molecular weight of injection gas and ambient gas, two injection strategies were proposed for this engine. This study aims at measuring the characteristics of non-reactive H2 and O2 jets in Ar atmosphere by Schlieren method. The experimental results demonstrate that the increase of injection pressure or the decrease of ambient pressure leads to an increase of penetration. Jet penetration length of O2 is slightly lower than H2 by 0–6%. The dispersion angle of gas jet increases slightly with the increase of injection pressure and ambient pressure. Under all the experimental pressure boundary conditions, the dispersion angles of H2 jets are between 31° and 36° and the dispersion angles of O2 jets are between 22° and 28°. The entrainment rate of gas jet increases with the increase of injection pressure, ambient pressure and injection time. Jet entrainment rate of O2 is 2.43–2.98 times that of H2 jet because of the lower volume flow rate of O2 jet. H2 jet entrains more total argon volume for its higher penetration and dispersion angle. The actual engine prefers to use the hydrogen injection strategy.

Investigations on the penetration length of steam-air mixture jets injected horizontally and vertically in quiescent water

Gas submerged jet penetration length is a key parameter for many industrial applications. Many experimental and theoretical works have been performed on pure steam and non-condensable gas submerged jets. However, the steam-air mixture gas submerged jets are not yet fully understood. So, a series of visualization experiments are performed to investigate the effect of air mass fraction, jetting direction, water temperature and inlet pressure on mixture gas submerged jet penetration length. Two flow regimes are distinguished based on the evolution of the interface between water and mixture gas, which are referred to as stable regime and oscillation regime. A flow regime map is developed based on inlet pressure and air mass fraction. A momentum balance model for predicting jet penetration length is proposed. Results show that the mixture gas jet penetration length increases with the increasing inlet pressure and decreases with the increasing air mass fraction. The water temperature has little effect on the jet penetration length. A new correlation for dimensionless vertical jet penetration length is developed based on the form of model analysis. The discrepancy between predicted results and present experimental data is within ±5%. A new correlation for dimensionless horizontal jet penetration length is developed based on experimental results. The discrepancy between predicted dimensionless horizontal jet penetration length and experimental value is within ±18%.

Interfacial characteristics of steam jet condensation in crossflow of water in a vertical pipe

An experimental study is performed to investigate the interfacial characteristics of steam jet condensation in crossflow of water in a vertical pipe. A high-speed camera is applied to capture the raw images of the condensing jet in the flow visualization test section. According to both the gray and gray-gradient profiles of the original images, an interfacial identification method is proposed to reveal the interfacial characteristics, including the jet plume shape, jet centerline trajectory and jet penetration length. Based on the expansion features of the two phase interface, the condensation regimes are classified into five categories, including double expansion-contraction, expansion-contraction, cylinder, contraction and hemisphere shapes. The steam mass flux, scaled by critical steam mass flux at ambient pressure, is found to be irrelevant to the transitional lines among the hemisphere, conical and expansion-contraction shapes in the condensation regime map. The jet momentum ratio as a dominant factor is introduced to correlate the jet centerline trajectory, and the predicted results are within ±20% of the experimental data. The dimensionless jet penetration length decreases with increase of ambient pressure, and is found to be in the range of 0.58–6.49 in present experiments. A correlation for prediction of the dimensionless jet penetration length is established, and the discrepancies between the predicted results and experiments are within ±15%.

Simulations of vertical jet penetration using a filtered two-fluid model in a gas–solid fluidized bed

The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. The distributions of volume fraction and the velocity of particles along the lateral direction were investigated for different jet velocities by analyzing the simulated results. The vertical jet penetration lengths at the different gas jet velocities have been obtained and compared with predictions derived from empirical correlations; the predicted air jet penetration length is discussed. Agreement between the numerical simulations and experimental results has been achieved.

CPFD 시뮬레이션을 통한 Shroud 노즐 및 수직 구조물이 설치된 기포 유동층 반응기 내에서의 기포 흐름 해석

본 연구에서는 내경 0.3 m, 높이 2.4 m인 기-고 유동층 반응기 내에서 수직 방향의 내부 구조물과 shroud 노즐 분산판이 기포 흐름에 미치는 영향을 CPFD (Computational Particle-Fluid Dynamics)를 이용하여 모델링을 수행하였다. 층 물질로는 Metal-grade 실리콘 입자(MG-Si)가 사용되었으며 <TEX>$d_p=149{\mu}m$</TEX>, <TEX>${\rho}_p=2,325kg/m^3$</TEX>, <TEX>$U_{mf}=0.02m/s$</TEX>이다. 전체 층물질의 양은 75 kg이며 정적층(static bed) 높이는 0.8 m이다. 수직 내부 구조물이 기포 상승속도에 미치는 영향을 파악하였다. 내부 구조물이 분산판으로부터 0.45 m 높이에 설치되었을 때 기포의 분쇄가 일어났다. 유동층의 압력강하 및 수직 고체체류량 분포는 내부 구조물의 영향을 크게 받지 않는 것으로 나타났다. 하지만 내부 구조물이 제트에 너무 가까운 경우 기포가 분쇄되지 않고 내부 구조물을 우회하여 상승하였으며 내부 구조물이 없는 경우나 0.45 m 높이에 설치된 경우에 비해 더 빠른 속도로 상승하였다. The effect of internal and shroud nozzle distributor to bubbling fluidized beds which has the size of <TEX>$0.3m-ID{\times}2.4m-high$</TEX> column was modeled by CPFD (Computational Particle-Fluid Dynamics). Metal-grade silicon particles (MG-Si) were used as bed materials which have <TEX>$d_p=149{\mu}m$</TEX>, <TEX>${\rho}_p=2,325kg/m^3$</TEX> and <TEX>$U_{mf}=0.02m/s$</TEX>. Total bed inventory and static bed height were 75 kg and 0.8 m, respectively. Effect of vertical internal on the bubble rising velocity was investigated. Bubbles were split by internal when the axial position of the internal from the distributor, z = 0.45 m. Bed pressure drop and axial solid holdup were not affected by internal. However, in the case that axial distance of internal from distributor was too close to jet penetration length, bubbles were not separated and bypassed internal, and faster than without internal or z = 0.45 m.

Experimental Measurement of the Velocity Field of Round Wall Jet in Counterflow

Experimental investigations showing the mean and fluctuating velocity fields of a three-dimensional round wall jet in counterflow are presented. The ratios of jet to counterflow velocity ranged from 2.5 to 25 and the jet Reynolds numbers were from 1,000 to 10,000. The jet penetration length, which is the axial distance that the wall jet penetrates into the counterflow before stopping, was measured and scaled with a power-law relation. The decay of the jet velocity during its penetration into the oncoming flow was analyzed with proper scaling parameters. The results show that up to 70% of the wall jet penetration length, the velocity decay, and the spreading rate are effectively identical to those of a wall jet in quiescent ambient flow. Above this distance, the velocity decay is linear and the jet spreading rate increases sharply. The mean axial velocity profiles show self-similarity between 25 and 80% of the penetration distance and are similar to the case with no counterflow. The vortical structures from the jet and the opposing turbulent boundary layer interact in the stagnation area to provide a large recirculation region with stochastic oscillations that enhance the mixing of the wall jet and counterflow. These interactions result in a region of high turbulence intensity near the upstream extents of the wall jet. The profiles of Reynolds stresses are presented and discussed. It was observed that the normalized velocity fluctuation profiles show self-similarity for the region within 30 and 70% of the wall jet penetration length, which is shorter than the region for which the axial velocity profiles are self-similar.