Mean Axial Velocity Research Articles

Scaling and Numerical Analysis of Nonuniform Waterjet Pump Inflows

Numerical simulations of the velocity fields entering the pump of a waterjet propelled ship have been performed to evaluate the level of nonuniformity in axial velocity. Nonuniform axial velocity entering the pump causes unsteady loading of the rotor blades resulting in noise and vibrations, and can increase the risk of rotor cavitation. The hull form modeled in this study is the R/V Athena, fitted with a waterjet propulsion system. Ship speeds correspond to Froude numbers between 0.34 and 0.84 and Reynolds numbers between 3.6 $\,\times {\hbox {10}}^{8}$ and 9.0 $\,\times {\hbox {10}}^{8}$ . The pump flow rate and shaft speed are determined via calm water resistance data from experiments and the pump curves for the axial flow pump. The numerical simulations are for steady, single phase flow and do not include free surface effects. In all of the numerical simulations, the hull draft is constant and the trim angle is fixed at 0 $^{\circ}$ (even keel). The variation in axial velocity is quantified by total distortion coefficient, harmonic components, and rotor section inflow angles. Using harmonic analysis, it is shown that the nondimensional wake entering the pump exhibits a mean axial velocity component that varies proportionally to nozzle velocity ratio (NVR) and harmonics of constant amplitude and phase, for all ship speeds. Thus, the wake pattern at any ship speed can be approximated using the harmonic content of the wake at one ship speed, and scaling the mean component of axial velocity. It is found that this hull and pump configuration resulted in the pump operating at a fixed pump flow coefficient for all ship speeds simulated. Thus, the average rotor section inflow angles are also constant over the speed range examined, which would be ideal for a rotor with a fixed pitch distribution as the mean angle of attack on a given rotor section will be independent of ship speed.

Velocimetry of cathode particles in a magnetoplasmadynamic thruster discharge plasma.

With high-speed imaging, it is possible to directly observe the time-evolution of the macroscopic behavior of the discharge plasma in a magnetoplasmadynamic thruster (MPDT). By utilizing direct high-speed imaging capable of capturing many images over the course of a single discharge, the velocity of the cathode erosion particles can be measured, opening the possibility of a novel, noninvasive technique for discharge plasma flow field velocimetry. In this work, an 8 kA argon MPDT discharge is imaged at 26 173 fps utilizing a 0.9 neutral density filter. The camera is aligned with thruster centerline 4 m downstream of the thruster exit plane. By tracking visible particles appearing in the multiple images, the particle motion in the radial and azimuthal directions is directly imaged. Through the use of traditional techniques in digital particle image velocimetry, the cathode particles emanating from the discharge are measured to have a mean radial velocity of 44.6 ± 6.0 m/s with a 95% confidence interval and a statistically insignificant azimuthal velocity. The setup and analysis employed permits measurement of the particle velocity in orthogonal direction to the image sensor plane using a single camera. By combining a background removal subtraction technique and knowledge of the optical focal plane, the estimated mean axial velocity of the particles is 1.59 km/s. This investigation ends with a discussion of important factors to consider for future MPDT high-speed imaging particle velocimetry, such as frame-rate, image size, spatial resolution, optics, and data handling selections.

Large eddy simulation of flame structure and combustion mode in a hydrogen fueled supersonic combustor

In this study, Large Eddy Simulation (LES) of supersonic turbulent mixing and combustion adopting a Partially Stirred Reactor (PaSR) sub-grid combustion model is performed for a hydrogen fueled model scramjet combustor. The compressible LES solver, which adopts a skeleton of 27 steps and 9 species hydrogen chemical kinetics model, is used to simulate the flowing and combustion processes based on structured hexahedral grids. The code is implemented in an Open Source Field Operation and Manipulation (OpenFOAM) solver, and validated against experimental data in terms of mean axial velocity and static temperature at different cross-sections, all show good predictions. An analysis of the flow field is carried out to investigate the supersonic turbulent flame structure and combustion mode in the combustor. Mixture fraction is extracted to indicate the reaction progress at different sites, which donates the most likely flame locations when at stoichiometric. Comparison of combustion parameters including OH mass fraction, scalar dissipation rate, flame index and heat release rate spatial distribution reveals that the supersonic combustion has the characteristics of a turbulent diffusion flame, where combustion is held at non-premixed mode controlled by turbulent mixing in the shear layers. A time scale analysis, the Damköhler Number is performed to examine these reactive zones in more detail. The role of auto-ignition in flame stabilization and lift-off is revealed.

Reynolds-Averaged Navier–Stokes and Large-Eddy Simulation Investigation of Lean Premixed Gas Turbine Combustor

Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulations (LES) of a Siemens scaled combustor are compared against comprehensive experimental data. The steady RANS simulation modeled one quarter of the geometry with 8 M polyhedral cells using the shear stress transport (SST) k-ω model. Unsteady LES were performed on the quarter geometry (90 deg, 8 M cells) as well as the full geometry (360 deg, 32 M cells) using the wall-adapting local eddy-viscosity (WALE) subgrid model and dynamic evaluation of model coefficients. Aside from the turbulence model, all other models are identical for the RANS and LES. Combustion was modeled with the flamelet generated manifold (FGM) model, which represents the thermochemistry by mixture fraction and reaction progress. RANS simulations are performed using Zimont and Peters turbulent flame-speed (TFS) expressions with default model constants, as well as the kinetic rate from the FGM. The flame-speed stalls near the wall with the TFS models, predicting a flame brush that extends to the combustor outlet, which is inconsistent with measurements. The FGM kinetic source model shows improved flame position predictions. The LES predictions of mean and rms axial velocity, mixture fraction, and temperature do not show improvement over the RANS. All three simulations overpredict the turbulent mixing in the inner recirculation zone, causing flatter profiles than measurements. This overmixing is exacerbated in the 90 deg case. The experiments show evidence of heat loss, and the adiabatic simulations presented here might be improved by including wall heat-loss and radiation effects.

Large-Eddy simulation of turbulent pipe flow of power-law fluids

Fully developed turbulent flows of power-law fluids in a cylindrical stationary pipe are investigated numerically by the use of large eddy simulation (LES) for various power law index (0.5⩽n⩽1.4) at different Reynolds numbers (4000⩽Res⩽12,000). To validate the present computations, the predictions are compared to the results reported in the archival literature for laminar and turbulent flows. The LES predictions agree reasonably favourably with the findings of the literature. The log-region of the mean axial velocity profile expands with increasing Res and decreasing power-law index n. The predicted friction factor for n⩽1 at Res=4000 is slightly overestimated in comparison with Dodge and Metzner correlation, and is better interpolated by Gomes correlation. With increasing n the apparent viscosity increases close to the wall and decreases for y+>30. This implies that the turbulent fluctuations develop and are more intense further from the wall when n>1 and closer to the wall when n<1. The influence of Res and n on the higher-order statistics (skewness and flatness) is analyzed. Visualizations of the instantaneous filtered velocity fields exhibit turbulent patterns which develop more as n increases.

Unsteady RANS and detached eddy simulation of the multiphase flow in a co-current spray drying

A detached eddy simulation (DES) and a k-ε-based Reynolds-averaged Navier–Stokes (RANS) calculation on the co-current spray drying chamber is presented. The DES used here is based on the Spalart–Allmaras (SA) turbulence model, whereas the standard k-ε (SKE) was considered here for comparison purposes. Predictions of the mean axial velocity, temperature and humidity profile have been evaluated and compared with experimental measurements. The effects of the turbulence model on the predictions of the mean axial velocity, temperature and the humidity profile are most noticeable in the (highly anisotropic) spraying region. The findings suggest that DES provide a more accurate prediction (with error less than 5%) of the flow field in a spray drying chamber compared with RANS-based k-ε models. The DES simulation also confirmed the presence of anisotropic turbulent flow in the spray dryer from the analysis of the velocity component fluctuations and turbulent structure as illustrated by the Q-criterion.

Effects of Flow Ratio of Transverse Jet on Flow and Heat Transfer : A LBE Study

A Lattice Boltzmann Equation (LBE) method is utilized to simulate a transverse jet in cross flow (TJiCF) to investigate the interaction between the transverse jet and the main flow by using the TD2G9 model. Seven cases of different flow ratios (Jr = 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.0) are simulated. The influences of flow ratio (Jr) of the transverse jet to the main flow on vortex streets and temperature fields are studied. The characteristics of fluid vortex, mean axial velocity, mean temperature, fluctuating velocity, etc., are studied in details to show the effects of Jr. Significant changes of velocity and temperature fields are found in TJiCFs for Jr > 1, i.e. the turbulence is augmented significantly and the convective and conductive heat transfer are enhanced greatly too. The turbulence augmentation is especially evident in the recirculation zone after the transverse jet. The conductive heat transfer is enhanced by thinning the thermal boundary layer near the wall, and the convective heat transfer is enhanced by intensive fluid mixing between the transverse jet and main flow.

Turbulent models of oil flow in a circular pipe with sudden enlargement

We describe three-dimensional calculations of oil flow in a circular pipe with an abrupt expansion, using the commercial code Fluent 6.3, to evaluate the performance of three turbulence closures: the standard k–∊, the Realizable k–∊, and the RNG-based k–∊ models. The effect of near-wall modelling in any of these closures is also investigated using the Standard Wall Functions (SWF) and the Enhanced Wall Treatment (EWT) approaches. The axial mean velocity, the turbulence kinetic energy, and the reattachment length are compared among the different models and with experimental measurements of oil flow through a 90° diffuser. Based on the standard deviation of the numerical profiles from the experimental data, we find that on average the RNG k–∊ model gives slightly better results regardless of the near-wall treatment. However, the Realizable k–∊ closure gives standard deviations comparable to the RNG k–∊ model when the EWT approach is implemented. Concerning the reattachment length, the standard k–∊ and the RNG k–∊ models match very well the experimental value when used in combination with the SWF approach, while the best prediction with the EWT method is provided by the RNG k–∊ closure.

Induced Pressure Fields of Power-law Fluids Electroosmotic Flow in Micro-diffuser at Different Angles

This paper describes the induced pressure of power-law fluids electroosmotic flow (EOF) in micro-diffuser at different angles such as 30° and 60°. Ostwald-De Wael model is used to describe the power-law fluids, and high accuracy compact difference algorithm is used to solve complete Poisson-Boltzmann equations and modified two-dimension Cauchy momentum equations. Poisson equation of pressure is solved by the velocity and pressure method. Dimensionless induced pressure nephogram and mean axial velocity are shown in this study. While the diffuser angles is 30° or 60°, the impact of induced pressure is much more significant than that without pressure gradient. Dimensionless mean velocity profiles with induced pressure have a larger error than the situation without it. Shear thinning fluid is sensitive to the change of flow filed while shear thickening fluid is the opposite. For EOF in variable section, the influence of induced pressure should not be neglected. Especially for less viscous fluid such as shear thinning fluid, it has a larger error with induced pressure compared without it.

Numerical Investigation of MILD Combustion Using Multi-Environment Eulerian Probability Density Function Modeling

In the present paper, the flames imitating Moderate and Intense Low Oxygen Dilution (MILD) combustion are studied using the Probability Density Function (PDF) modeling approach. Two burners which imitate MILD combustion are considered for the current study: one is Adelaide Jet-in-Hot-Coflow (JHC) burner and the other one is Delft-Jet-In-Hot-Coflow (DJHC) burner. 2D RANS simulations have been carried out using Multi-environment Eulerian Probability Density Function (MEPDF) approach along with the Interaction-by-Exchange-with-Mean (IEM) micro-mixing model. A quantitative comparison is made to assess the accuracy and predictive capability of the MEPDF model in the MILD combustion regime. The computations are performed for two different jet speeds corresponding to Reynolds numbers of Re = 4100 and Re = 8800 for DJHC burner, while Re = 10000 is considered for the Adelaide burner. In the case of DJHC burner, for Re = 4100, it has been observed that the mean axial velocity profiles and the turbulent kinetic energy profiles are in good agreement with the experimental database while the temperature profiles are slightly over-predicted in the downstream region. For the higher Reynolds number case (Re = 8800), the accuracy of the predictions is found to be reduced. Whereas in the case of Adelaide burner, the computed profiles of temperature and the mass fraction of major species (CH4, H2, N2, O2) are found to be in excellent agreement with the measurements while the discrepancies are observed in the mass fraction profiles of CO2 and H2O. In addition, the effects of differential diffusion are observed due to the presence of H2 in the fuel mixture.

Development of a portable power system with meso-scale vortex combustor and thermo-electric device

In this study, a small scale power generation system with a meso-scale vortex combustor has been developed. The system was consisted of a couple of thermo-electric device and a heat medium. The medium was made of duralumin, 40 × 40 × 20 mm and 52 g weight, and the vortex combustion chamber of 7 mm inner diameter was embedded in it. It was found that a stable flame could be established in the narrow 7 mm channel even the mean axial velocity reached 1.2 m/s. And furthermore, the vortex flow significantly enhanced the heat transfer from the burned gas to combustion chamber, and as a result, the medium was heated to 300°C quickly (within 5 minutes) by the combustion of propane / air mixture for 145W input energy. The system could successfully generate 1.98 W (4.3 V and 0.46 A), which corresponded to the energy conversion rate of 0.7 % per unit thermo-electric device.

Assessment of Turbulence-Chemistry Interaction Models in MILD Combustion Regime

The present paper reports on the assessment of different turbulence-chemistry interaction closures for modeling turbulent combustion in the Moderate and Intense Low oxygen Dilution combustion regime. 2D RANS simulations have been carried out to model flames issuing from two burners DJHC burner and Adelaide JHC burner which imitate the MILD combustion. In order to model these flames, two different approaches of turbulence-chemistry interaction models are considered; while in the PDF based modeling, two different variants are invoked to understand the applicability of the PDF based models in the MILD regime: one is based on presumed shape PDF approach and the other one is transported PDF approach. A comprehensive study has been carried out by comparing the results obtained from these different models. For the DJHC burner, the computations are carried out for a jet speed corresponding to Reynolds numbers of Re=4100, whereas the Adelaide JHC burner computations are performed for a jet speed corresponding to Reynolds number of Re=10000. The effects of molecular diffusion on the flame characteristics are also studied by using different micro-mixing models. In the case of DJHC burner, it has been observed that the mean axial velocity and the turbulent kinetic energy profiles are in good agreement with the measurements. However, the temperature profiles are over-predicted in the downstream region by both EDC and the PDF based models. In the context of Adelaide JHC burner, the profiles of the temperature and the mass fraction of major species (CH4, H2, O2, H2O, CO2) obtained using LPDF approach are in better agreement with the measurements compared to those obtained using EDC model; although, both the solution approaches fail to capture CO and OH radical profiles.

Near field vorticity distributions from a sharp-edged rectangular jet

Experimental results on the near field development of a free rectangular jet with aspect ratio 10 are presented. The jet issues from a sharp-edged orifice attached to a rectangular settling chamber at Reh∼23,000, based on slot width, h. Measurements on cross plane grids were obtained with a two-component hot wire anemometry probe, which provided information on the three dimensional characteristics of the flow field. Two key features of this type of jet are mean axial velocity profiles presenting two off axis peaks, commonly mentioned as saddleback profiles, and a predominant dumbbell shape as described by, for example, a contour of the axial mean velocity. The saddleback shape is found to be significantly influenced by the vorticity distribution in the transverse plane of the jet, while the dumbbell is traced to two terms in the axial mean vorticity transport equation that diffuse fluid from the centre of the jet towards its periphery. At the farthest location where measurements were taken, 30 slot widths from the jet exit, the flow field resembles that of an axisymmetric jet.

Effect of turbulence non-isotropy modeling on spray dynamics for an evaporating Acetone spray jet

The effect of turbulence closure on spray dynamics is studied for three dilute Acetone spray jets using an Eulerian–Lagrangian approach with two-way coupling. A stochastic random walk algorithm is employed to model the droplets’ dispersion. Simulations using different turbulence closure models (i.e. the isotropic SST-k-ω, and the k-∊ realizable models, and the non-isotropic Reynolds Stress Model (RSM)) are compared with the Sydney spray measurements for SP2,SP6, and SP7 spray conditions (Gounder et al., 2012). The experimental mass flow rate, spray mean and rms data are injected for each available size bin during the numerical simulations. Overall, the simulations show good comparisons with the mean and rms spray measurements. The turbulence closure non-isotropy modeling shows relatively weak effect on the spray mean velocity and size profiles predictions, where the RSM predictions was slightly better at the centerline at x/D=10 and x/D=20 for the SP2 mean axial velocity, with similar predictions to the k models for the SP6 and SP7. The RSM, however, consistently predicts better rms axial and radial spray velocity distribution, which indicates more realistic droplet dispersion than the isotropic SST-k-ω and the k-∊. The RSM gas phase shear stresses show that close to the nozzle (i.e. at x/D=5 and x/D=10) the turbulence non-isotropy increases as we approach the centerline and is maximum at the shear layer location at x/D=5. On the other hand, at the downstream locations at x/D=30 the turbulence field non-isotropy increases at the jet edge. A conical region of large size mean droplets (D10>26μm) is observed around the SP2 jet edge. This region disappears quickly for the SP6 and SP7 after the inflow section. The data analysis exhibits that the RSM predicts higher Stokes number than the SST-k-ω due to faster mixing time scales. For the impact on dynamics, at the centerline the SST-k-ω and k-∊ models, predict higher droplets’ slip velocity, higher drag force, and faster droplet’s response than the RSM. The droplets’ tendency for cross-stream dispersion is also found to vary with the turbulence model. The fan spreading phenomenon is observed at the down stream locations away from the nozzle. The results show that the spray turbulence is non-isotropic and lags the gas phase rms values, especially at the centerline. This discrepancy decreases downstream and towards the jet edge. The study shows the importance of non-isotropy modeling on the droplets dispersion and spray dynamics predictions.

Dispersion of negatively buoyant effluent jetted from ORV

Most of the previous studies on negatively buoyant jets were limited to the relationships between the effluent trajectory and inclination angle. Therefore, the influence of diffuser types on the dispersion of cooled water discharge, and the prediction of further dilution by ocean turbulence are not clearly investigated. Present study mainly focuses on the dispersion simulation of the cooled water effluent discharged from the LNG terminal located at Manzanillo, Mexico. To select the efficient diffuser type to minimize the temperature differential, the dilution by various outfall structures such as tee diffuser, staged diffuser, and single port diffuser were examined. Then, to examine whether the cooled water discharge from ORV (Open Rack Vaporizers) conforms to the environmental standard, numerical simulations by CORMIX and VISJET models were performed to compute the dispersion characteristics for varying ambient currents, effluent discharges, and discharging depths. Furthermore, dispersion analysis was made regarding the further dilution by ocean turbulence. In addition, the effect of effluent discharge on conveyance was checked by the calculation of the decay of mean axial velocity along the longshore direction.

Viscoelasticity in Achilles tendonopathy: quantitative assessment by using real-time shear-wave elastography.

To investigate the differences in viscoelastic properties between normal and pathologic Achilles tendons (ATs) by using real-time shear-wave elastography (SWE). The institutional review board approved this study, and written informed consent was obtained from 25 symptomatic patients and 80 volunteers. One hundred eighty ultrasonographic (US) and SWE studies of ATs without tendonopathy and 30 studies of the middle portion of the AT in patients with tendonopathy were assessed prospectively. Each study included data sets acquired at B-mode US (tendon morphology and cross-sectional area) and SWE (axial and sagittal mean velocity and relative anisotropic coefficient) for two passively mobilized ankle positions. The presence of AT tears at B-mode US and signal-void areas at SWE were noted. Significantly lower mean velocity was shown in tendons with tendonopathy than in normal tendons in the relaxed position at axial SWE (P < .001) and in the stretched position at sagittal (P < .001) and axial (P = .0026) SWE. Tendon softening was a sign of tendonopathy in relaxed ATs when the mean velocity was less than or equal to 4.06 m · sec(-1) at axial SWE (sensitivity, 54.2%; 95% confidence interval [CI]: 32.8, 74.4; specificity, 91.5%; 95% CI: 86.3, 95.1) and less than or equal to 5.70 m · sec(-1) at sagittal SWE (sensitivity, 41.7%; 95% CI: 22.1, 63.3; specificity, 81.8%; 95% CI: 75.3, 87.2) and in stretched ATs, when the mean velocity was less than or equal to 4.86 m · sec(-1) at axial SWE (sensitivity, 66.7%; 95% CI: 44.7, 84.3; specificity, 75.6%; 95% CI: 68.5, 81.7) and less than or equal to 14.58 m · sec(-1) at sagittal SWE (sensitivity, 58.3%; 95% CI: 36.7, 77.9; specificity, 83.5%; 95% CI: 77.2, 88.7). Anisotropic results were not significantly different between normal and pathologic ATs. Six of six (100%) partial-thickness tears appeared as signal-void areas at SWE. Whether the AT was relaxed or stretched, SWE helped to confirm and quantify pathologic tendon softening in patients with tendonopathy in the midportion of the AT and did not reveal modifications of viscoelastic anisotropy in the tendon. Tendon softening assessed by using SWE appeared to be highly specific, but sensitivity was relatively low.

English

Laser Doppler anemometry (LDA) has been employed to quantify the liquid velocity field around a single bubble in its generating and accelerating stage in carboxymethylcellulose (CMC) aqueous solution. The instantanoues velocities were treated by Reynolds time-averaged method, and mean velocities and its contours in both axial and radial directions were investigated. The results show that in vertical direction, the flow field characteristics of the liquids around the bubble are determined by bubble formation-rise mechanism, whereas in horizontal direction they are governed by the relative position with the bubble shear radius. The contours of axial and radial mean velocity in the test section take on the shapes of inverted trapezoid and butterfly forewing, respectively.

Temperature, velocity and air entrainment of fire whirl plume: A comprehensive experimental investigation

Comprehensive measurements were performed to examine the temperature, velocity (in axial and tangential directions) and air entrainment of propane fire whirl plume in a medium-scale fixed-frame facility. It is found that the radial profile of excess temperature varies consistently with the continuous flame shape and the radial decay rate of excess temperature decreases in the intermittent flame and plume. The centerline axial velocity depends on both the buoyancy and the axial pressure gradient related to the tangential velocity. A weak annular reverse flow is found outside the upward core at z/D⩽1.0, while the absolute axial velocity slightly increases with fire size. The growth of axial velocity core is found to be constrained by the reverse flow. The mean axial velocity radius is confirmed to be greater than the mean excess temperature radius in the continuous flame. The radial profile of tangential velocity varies steadily with height, and is little affected by heat release rate. The radial swirl flow consists of the vortex core, the quasi-free vortex and the near wall region, and the active reaction occurs in the vortex core. The plume growth rate increases with decreasing RiB (Richardson number) and three distinct regions are identified in different RiB ranges. The air entrainment is strong at the bottom inflow boundary layer, while the mass flow rate increases slowly with height as compared to buoyant pool fires. The suppression of air entrainment may be attributable to the radial force balance and stable stratification in the centrifugal acceleration filed. The entrainment coefficient in the continuous flame is about one to two orders of magnitude lower than that in a buoyant pool fire, and it generally increases with height in the plume of fire whirl, approaching the value for pure buoyant plume. The mean entrainment coefficient depends on the mean RiB by −1 power law for z⩽Hf.

Experimental and numerical investigation of turbulent nanofluid flow in helically coiled tubes under constant wall heat flux using Eulerian–Lagrangian approach

In the present study, turbulent flow in helically coiled tubes under constant wall heat flux is numerically and experimentally investigated. Pressure drop and convective heat transfer behavior of water and water–silver nanofluid are studied. In experimental section, the pressure drop measurements as well as the average convective heat transfer coefficient calculations are carried out. The numerical computations are performed by Eulerian–Lagrangian two-phase approach in connection with an RNG k–ε turbulence model accounting for four-way coupling collisions using ANSYS CFX software. The Brownian motion of nanoparticles is taken into account. Single-phase approach (homogeneous model with constant effective properties) is also used. Two-phase approach predicted much more accurate results than the homogeneous model. More enhanced heat transfer was observed for tubes with greater curvature ratio. The results showed that the nanoparticles did not change the axial velocity and turbulent kinetic energy significantly, while the micrometer-sized particles increased mean axial velocity and suppressed turbulence. It was found that the utilization of the base fluid in helical pipe with greater curvature ratio compared to the use of nanofluid in straight tubes increased heat transfer more effectively. Based on the numerical results validated by the experimental ones, two correlations were developed to predict the ratio of the mean heat transfer coefficient and the pressure drop of nanofluid to water in helical tubes.

Comparative study of a vertical round jet in regular and random waves

The hydrodynamic behaviors of a vertical round jet in regular and random waves are comparatively investigated. The regular and the random waves are chosen based on the concept of equivalent energy density and energy flux. The experimental study is first carried out to compare the lateral profiles of jet mean axial velocity at various vertical levels. The results show that, under the present experimental conditions, the phenomenon of “twin peaks” appears in the regular waves, but virtually does not exist in the corresponding random waves. This results in a lower axial velocity along the centerline for the jet in the regular waves. A large eddy simulation (LES) model is subsequently developed to quantify the difference of jet half-width under the same wave conditions as those in the laboratory. The numerical results show that the jet in the random waves has a larger jet half-width than that in the regular waves, which is consistent with the visual observations in laboratory experiments. More scenarios of the jet in different regular and random waves are numerically investigated and the results show that the “twin peaks” may also appear under the condition of random waves, but requiring a larger wave-to-jet momentum ratio.