Axial Turbulence Research Articles

Breakdown of the velocity and turbulence in the wake of a wind turbine – Part 2: Analytical modelling

Abstract. This work aims to develop an analytical model for the streamwise velocity and turbulence in the wake of a wind turbine where the expansion and the meandering are taken into account independently. The velocity and turbulence breakdown equations presented in the companion paper are simplified and resolved analytically, using shape functions chosen in the moving frame of reference. This methodology allows us to propose a physically based model for the added turbulence and thus to have a better interpretation of the physical phenomena at stake, in particular when it comes to wakes in a non-neutral atmosphere. Five input parameters are used: the widths (in vertical and horizontal directions) of the non-meandering wake, the standard deviation of wake meandering (in both directions) and a modified mixing length. Two calibrations for these parameters are proposed: one if the users have access to velocity time series and the other if they do not. The results are tested on a neutral and an unstable large-eddy simulation (LES) that were both computed with Meso-NH. The model shows good results for the streamwise velocity in both directions and can accurately predict modifications due to atmospheric instability. For the axial turbulence, the model misses the maximum turbulence at the top tip in the neutral case, and the proposed calibrations lead to an overestimation in the unstable case. However, the model shows encouraging behaviour as it can predict a modification of the shape function (from bimodal to unimodal) as instability and thus meandering increases.

Performance and wake interaction between two aligned vertical axis turbines

Performance and wake interaction between two aligned vertical turbines are investigated by solving the three-dimensional Navier-Stokes equations with the k−ω SST IDDES turbulence model. Specifically, the impact of longitudinal spacing between the upstream and downstream turbines is examined. The numerical results show that as the longitudinal distance increases, the performance of the downstream turbine shows a quadratic growth. This is phenomenon is strongly correlated to the wake recovery of the upstream turbine. Based on the velocity and turbulence distribution, the wake of the upstream turbine could be divided into three distinct zones. However, the zone characterized by low axial velocity and turbulence level is not observed in the wake of the downstream turbine. This difference primarily arises from the high turbulence present in the incoming wake from the upstream turbine, combined with the turbulence generated by the downstream turbine. Interestingly, regardless of the longitudinal distances between the turbines, the downstream turbine displays similar wake patterns for different streamwise distances between turbines. This consistency is attributed to the influence of the upstream turbine's wake on the stability of the downstream turbine's wake. The downstream turbine is suggested to be positioned in the zone where the upstream turbine's wake has fully developed.

Direct numerical simulations of turbulent pipe flow up to

Well-resolved direct numerical simulations (DNS) have been performed of the flow in a smooth circular pipe of radius $R$ and axial length $10{\rm \pi} R$ at friction Reynolds numbers up to $Re_\tau =5200$ using the pseudo-spectral code OPENPIPEFLOW. Various turbulence statistics are documented and compared with other DNS and experimental data in pipes as well as channels. Small but distinct differences between various datasets are identified. The friction factor $\lambda$ overshoots by $2\,\%$ and undershoots by $0.6\,\%$ the Prandtl friction law at low and high $Re$ ranges, respectively. In addition, $\lambda$ in our results is slightly higher than in Pirozzoli et al. (J. Fluid Mech., vol. 926, 2021, A28), but matches well the experiments in Furuichi et al. (Phys. Fluids, vol. 27, issue 9, 2015, 095108). The log-law indicator function, which is nearly indistinguishable between pipe and channel up to $y^+=250$ , has not yet developed a plateau farther away from the wall in the pipes even for the $Re_\tau =5200$ cases. The wall shear stress fluctuations and the inner peak of the axial turbulence intensity – which grow monotonically with $Re_\tau$ – are lower in the pipe than in the channel, but the difference decreases with increasing $Re_\tau$ . While the wall value is slightly lower in the channel than in the pipe at the same $Re_\tau$ , the inner peak of the pressure fluctuation shows negligible differences between them. The Reynolds number scaling of all these quantities agrees with both the logarithmic and defect-power laws if the coefficients are properly chosen. The one-dimensional spectrum of the axial velocity fluctuation exhibits a $k^{-1}$ dependence at an intermediate distance from the wall – also seen in the channel. In summary, these high-fidelity data enable us to provide better insights into the flow physics in the pipes as well as the similarity/difference among different types of wall turbulence.

Effect of the Axially Inserted Solid Rod on the Flow Field Characteristics and Separation Performance of a Hydrocyclone.

In this paper, the experimental validation and numerical simulation were used to investigate the effect of the inserted solid rod on the separation process of the hydrocyclone. The simulation results are analyzed in terms of the pressure drop, air core, velocity component, turbulence intensity, and separation performance when the air core is completely inhibited or not. The results indicate that the solid rod with the smaller size cannot completely inhibit the air core, but it can still affect the separation process. The variable diameter inserted solid rod (dvr) could inhibit the air core and ensure a larger effective separation space, which could improve the separation performance of the hydrocyclone. Specifically, the dvr could improve energy conversion ability, tangential velocity, and separation sharpness and decrease axial velocity and turbulence intensity. Therefore, inhibiting the air core is conducive to the separation process of hydrocyclone, and the variable diameter inserted solid rod has better inhibited effect.

Tangential leakage flow control with seal-grooves on the static scroll of a CO2 scroll compressor

• The seal-grooves are arranged on the sidewall of the static scroll. • Tangential leakage flow is reduced by the seal-grooves on the static scroll. • The seal-grooves arranged in the compression chamber brings more benefit. • Multi seal-grooves prolongs the energy dissipation of the tangential leakage flow. • Both streamwise and secondary axial vortex contribute to the sealing effect. Tangential leakage is an important factor affecting the aerothermodynamic performance of the scroll compressor, and existing methods to reduce tangential leakage usually aim at narrowing leakage path. In this paper, continuous seal-grooves arranged on the sidewall of static scroll was proposed, in order to achieve the passive flow control of the tangential leakage. Numerical methods were conducted to investigate the flow characteristics of tangential leakage in the radial clearance with seal-grooves. The impacts of diverse geometric parameters and arrangement schemes on the performance of the scroll compressor were also discussed. Results showed that throttling effect, flow separation of tangential leakage, and secondary axial turbulence was the main influence mechanism of the seal-grooves. Appropriate groove depth and spacing contributes to the developments of flow separation and secondary axial turbulence in seal-grooves, while increasing seal-groove number brought better flow control effect. Based on the above results, the seal-grooves arranged on the sidewall of compression chamber increased separately the volumetric efficiency and isentropic efficiency by 1.63% and 1.32%, and the volumetric efficiency also improved by 0.99% when the seal-grooves were arranged in the suction chamber. This work may provide a new flow control method of tangential leakage in the scroll compressor.

The Effects of Turbulence Intensity and Tip Speed Ratio on the Coherent Structure of Horizontal-Axis Wind Turbine Wake: A Wind Tunnel Experiment

The evolution laws of the large-eddy coherent structure of the wind turbine wake have been evaluated via wind tunnel experiments under uniform and turbulent inflow conditions. The spatial correlation coefficients, the turbulence integral scales and power spectrum are obtained at different tip speed ratios (TSRs) based on the time-resolved particle image velocity (TR-PIV) technique. The results indicate that the large-eddy coherent structures are more likely to dissipate with an increase in turbulence intensity and TSR. Furthermore, the spatial correlation of the longitudinal pulsation velocity is greater than its axial counterpart, resulting into a wake turbulence dominated by the longitudinal pulsation. With an increase of turbulence intensity, the integral scale of the axial turbulence increases, meanwhile, its longitudinal counterpart decreases. Owing to an increase in TSR, the integral scale of axial turbulence decreases, whereas, that of the longitudinal turbulence increases. By analyzing the wake power spectrum, it is found that the turbulent pulsation kinetic energy of the wake structure is mainly concentrated in the low-frequency vortex region. The dissipation rate of turbulent kinetic energy increases with an increase of turbulence intensity and the turbulence is transported and dissipated on a smaller scale vortex, thus promoting the recovery of wake.

Computational fluid dynamics based numerical study to determine the performance of triangular solar air heater duct having perforated baffles in V-down pattern mounted underneath absorber plate

In the current analysis, the effect of perforated baffles in V-down pattern as artificial roughness on the thermal and hydraulic response of a solar air heater having equilateral triangular passage has been examined. A thorough numerical investigation has been done using ANSYS FLUENT-19.0. Effect of change in roughness parameters, viz., baffle height (e) and open area ratio (β) on thermo-hydraulic performance has been explored. Flow Reynolds number is systematically varied. Study reveals that upon varying the baffle height from 5 mm to 11 mm and open area ratio from 20% to 29%, maximum heat transfer rate is attained at e = 9 mm and β = 20%, respectively. Axial Velocity and Turbulence Kinetic Energy have been plotted for clear view of change in variables. Also, the correlations have been developed for Nusselt number and Friction factor. The thermo-hydraulic performance factor of proposed perforated baffle geometry has been observed to be 2.54 at e = 9 mm and β = 20%. Performance of the SAH with suggested roughness is found to be advantageous than other type of roughness elements studied in recent times.

Enhancement of heat transfer in a synthetic jet actuated by piston cylinder

Modern electronics demand more powerful cooling systems due to an increase in heat dissipation. The traditional cooling techniques reached their limit and the synthetic jet impingement arises as a promising method for cooling of modern electronic systems. This paper presents the experimental studies on the heat transfer characteristics of a synthetic jet. The synthetic jet is driven by a piston actuator. The effects of dimensionless parameters like the distance between the orifice and heater plate (Z/D), the ratio of stroke length to diameter of orifice ( L/D), Stokes number, and Reynolds number are discussed. The effect of orifice geometry, number of orifices are also presented. The results indicate that the Z/D and Stokes number have a significant influence on the heat transfer rate. As the Stokes number increases the heat transfer increases due to an increase in axial momentum and turbulence in the flow direction. For circular orifice and at high Z/D, the L/D ratio should be higher for better heat transfer. Rectangular orifice performs better than square and circular geometries. When compared to single jet multiple jets have a higher heat transfer rate. Maximum and minimum values of normalized pressure ( Pnr) are achieved for high Stokes number and smaller areas of the orifice.

Effects of backward inclination on a pulsed jet in crossflow

The effects of the backward inclination angle on the flow and jet dispersion characteristics of a pulsed jet in crossflow were studied experimentally in an open-loop wind tunnel. The pulsations were created by a loudspeaker which installed at the bottom of a nozzle assembly. The instantaneous and time-averaged flow patterns were obtained using the laser-light sheet assisted smoke flow visualization method. The instantaneous and average velocities, turbulence intensities, integral turbulence time scales were probed using a hot-wire anemometer. The tracer-gas detection technique was applied to examine the fluid dispersion capability of the jet. With excitation, the axial jet pulsations were transferred to transverse oscillations after the jet was deflected by the crossflow. A small jet backward inclination angle could lead to an increase of jet-fluid dispersion and transverse jet spreading width. There existed a critical jet backward inclination angle of 20° at which the jet-fluid dispersion index and transverse jet spreading width attained the maximum values. Arranging the jet backward inclination angle at values smaller than 20° could induce an increase in dispersion of the pulsed jet in crossflow and benefit the industrial applications which required fast and efficient jet-fluid dispersion and mixing. • Jet backward inclination angle presented significant effects on axial mean velocities, turbulence intensities, and dispersion properties. • There existed a critical jet backward inclination angle of 20° at which the jet spreading width and dispersion attain maximum values. • At jet backward inclination angle smaller than critical value, increasing inclination angle could increase jet-fluid dispersion. • At jet backward inclination angle larger than critical value, increasing inclination angle would significantly decrease jet-fluid dispersion. • Arranging jet backward inclination angle at critical value could benefit industrial applications.

Hydrodynamic Modeling of Turbulence Modulation by Particles in a Swirling Gas-Particle Two-Phase Flow.

Turbulence modulations by particles of a swirling gas–particle two-phase flow in an axisymmetric chamber are numerically simulated. To fully consider the preferential concentrations and the anisotropic dispersions of particles, a second-order moment model coupling particle–particle collision model was improved. Experimental validation for the proposed model, algorithm, and in-house codes by acceptable match was carried out. The effects of ultralight-expanded graphite and heavy copper particles with a large span of Stokes number on gas velocities and fluctuations, Reynolds shear stresses and tensor invariants, turbulence kinetic energies, and vortice structures are investigated. The results show that turbulent modulation exhibits strong anisotropic characteristics and remains in a close relationship with the flow structure. Modulation disturbances and vortex evolution are enforced by heavy-large particles with higher Stokes numbers. Preferential accumulations of ultralight particles in shear stress regions at lower vortices are weaker than those of heavy particles. For axial turbulence modulations, a heavy particle plays the primary role in the inhibition action because of larger inertia, and a light particle contributes to the enhancement effect due to excellent followability. The instantaneous flow information and coherent turbulent structure are failed to be acquired due to the limitation of the Reynolds time-averaged algorithm.

Experimental and Numerical Analysis of Gas Premix Turbulent Flames Stabilized in a Swirl Burner With Central Bluff Body

Abstract Lean premixed gas turbulent flames stabilized in the flow generated by an industrial swirl burner with a central bluff body are experimentally found to behave bistable. This bistable behavior, which can be triggered via a small change in some of the controlling parameters, for example, the bulk equivalence ratio, consists in a rather sudden transition of the flame from completely lifted to well attached to the bluff body. This has impact on combustion dynamics, emissions, and pressure losses. While several experimental investigations exist on this topic, numerical analysis is limited. This work is therefore also of numerical nature, with a twofold scope: (a) simulation and validation with experiments of the bistable flame behavior via computational fluid dynamics (CFD) in the form of large eddy simulation (LES) and (b) analysis of CFD results to shed light on the flame stabilization properties. LES results, in case of the lifted flame, show that the vortex core is sharply precessing at a given frequency. Phase averaging these results at the frequency of precession clearly indicates a counterintuitive and unexpected presence of reverse flow going all the way through the flame apex and the bluff body tip. The counterintuitive presence of a lifted flame is explained here in terms of the phase averaged data, which show that the flame apex is not placed at the center of the spinning reverse flow region. It is instead slightly shifted radially outward where the axial velocity recovers to low positive values of the order of the turbulent burning rate. A simple one-dimensional flame stabilization model is applied to explain this peculiar flame behavior. This model provides first an estimation of the flame radius of curvature in terms of axial velocity and turbulence quantities. This radius is therefore used to determine the total flux of reactants into the flame, given by an axial convection and radial diffusion contributions. Subsequently, the possibility of the flame positioned at the center of the vortex is excluded based on the balance between this flux and the turbulent burning rate. A clear explanation of the mechanism leading to the sudden flame jump has instead not been identified and only some hypotheses are provided.

The influence of waves propagating with the current on the wake of a tidal stream turbine

The presence of the wind-waves enhances the flow turbulent complexity and modifies the dynamic behaviour of the tidal-stream turbine and causes extra challenges for its performance and survivability. A sign of these effects is the modification of the turbine wake under the action of wind-waves, thus assessing the resulting wake characteristics is fundamental for technological development of such devices in single or array configurations. Laboratory experiments, involving regular waves propagating with the current, were conducted to describe the wake structure of a fixed scale model tidal-stream turbine. In order to highlight wave effects, the laboratory measurements are analysed in term of: (i) time-mean velocity profiles, (ii) swirl numbers, (iii) turbulence intensities and (iv) turbulent anisotropy maps. In each case, distinctive features are discussed in the downstream rotor near and far fields. The velocity profile is slightly affected by the waves in both near and far fields. The swirl number in the near field is drastically influenced by waves presence where a significant correlation with the wave-steepness is highlighted. Wave presence also affects the turbulence intensities both in the near and far field. This phenomenon is more evident at the top-tip and rotor–centreline water depth instead of in the bottom-tip level. The analysis of turbulent anisotropy maps shows that waves act on the wake flow leading to axisymmetric turbulent conditions mainly dominated by the axial turbulence component. These results constitute an initial step toward the understanding of unsteady wake interactions, in arrays of tidal stream turbines.

Numerical Investigation of Turbulent Premixed Combustion of Methane / Air in Low Swirl Burner under Elevated Pressures and Temperatures

Turbulent combustion modeling of lean premixed methane/air gas mixture in a low swirl burner is carried out using Large Eddy Simulation (LES). The operating conditions of the experiment as well as simulation are carried out at elevated pressure and temperature. The first case-simulation is a premixed combustion model based on C-equation formulation, the second one is based on species transport – Eddy Dissipation Concept (EDC) model. Numerical results for axial velocity and turbulence intensity along the centerline showed a good agreement against the experimental data. Quantitative results of OH mass fraction contour showing the flame structure are in a plausible agreement compared to the experimental measurement.

Comparación numérico experimental de la caída de presión a través de un hidrociclón

This paper shows the comparative results of an experimental and numerical study. The numerical simulations were performed with the ANSYS/Fluent software by means of CFD applying RNG k-ε and standard k-ω turbulence models. Experimental data were recorded of a hydrocyclone mounted on a test bench which operates with a water flow. The values extracted are the inlet pressure, outlet pressure, inlet velocity and outlet velocity. In order to investigate the pressure drop underwent by a hydrocyclone, a pressure assessment was carried out in different areas of the divice geometry. The results of the numerical study were compared and correlated with the experimental data. The numerical values report a percentage difference of 10.45% for the RNG k-ε model and 1.57% for the standard k-ω model, with respect to the experimentally obtained output pressure. The percentage difference between experimental and numerical pressure drop is 0.04% for standard k-ω model and 0.24% for RNG k-ε model. By studying finite volumes, the components of axial velocity, tangential velocity and turbulence intensity are calculated. These phenomena are studied simultaneously in this work. The turbulence models used to generate the corresponding analyzes in this work show similarity between both results and flow behavior. The concordance between the computational results and the experimental data is acceptable, so that the numerical simulations applied reach the purpose of this investigation.

Flow field characteristics, mixing and emissions performance of a lab-scale rich-quench-lean trapped-vortex combustor utilizing a quench orifice plate combined with a bluff-body

In this study, the low emission combustion technology of Rich-Quench-Lean (RQL) has been applied in Trapped-Vortex Combustor (TVC), and the combinative RQL-TVC shows a promising low emissions performance. By utilizing a quench orifice plate combined with a bluff-body, a lab-scale RQL-TVC was designed. The flow fields of RQL-TVC were measured by 2-D PIV and predicted by 3-D numerical simulation. Flow structures, radial profiles of normalized mean axial velocity, turbulence intensity and mixing level of the quench zone were analyzed. Results reveal that the dual-vortex and the single-vortex flow patterns both exist in cavities and quench zone of RQL-TVC, and the turbulence intensity is strong in the quench zone with some reverse flows. The spiral vortex was discussed by 3-D streamlines and the detail flow structures of the quench zone were analyzed based on the numerical results. The mixing level of the quench zone was determined, and results show that the quench device enhances the mixing level compared with TVC. Combustion efficiency and emissions performance were investigated experimentally, and results demonstrate that RQL-TVC has relatively higher combustion efficiency and lower emission index of CO, UHC and NOx than the same size lab-scale TVC in present work.

System optimization for effective hydrogen production via anaerobic digestion and biogas steam reforming

To construct a system for the effective hydrogen production from food waste, the conditions of anaerobic digestion and biogas reforming have been investigated and optimized. The type of agitator and reactor shape affect the performance of anaerobic digestion reactors. Reactors with a cubical shape and hydrofoil agitator exhibit high performance due to the enhanced axial flow and turbulence as confirmed by simulation of computational fluid dynamics. The stability of an optimized anaerobic digestion reactor has been tested for 60 days. As a result, 84 L of biogas is produced from 1 kg of food waste. Reaction conditions, such as reaction temperature and steam/methane ratio, affect the biogas steam reforming reaction. The reactant conversions, product yields, and hydrogen production are influenced by reaction conditions. The optimized reaction conditions include a reaction temperature of 700 °C and H2O/CH4 ratio of 1.0. Under these conditions, hydrogen can be produced via steam reforming of biogas generated from a two-stage anaerobic digestion reactor for 25 h without significant deactivation and fluctuation.

Effects of Reynolds number on flow and mixing characteristics of a self-sustained swinging jet

The effects of Reynolds number on flow and mixing characteristics of a merged single swinging jet induced by a V-shaped fluidic oscillator were studied experimentally. The jet Reynolds number was varied from 80 to 3000. A high-speed digital camera was used to capture the instantaneous flow evolution processes using the laser light-sheet-assisted flow visualisation method. Long-exposure images together with the binary edge detection technique were used to identify the jet spread width. The velocities, turbulence intensities, as well as turbulence macro time and length scales in the central axis were measured using a one-component hot-wire anemometer. Measurement results using the tracer-gas concentration detection method provided information on the dispersion characteristics of the merged swinging and non-swinging jets. Four characteristic flow modes (non-swinging, subcritical swinging, critical swinging, and supercritical swinging jets) were identified within different ranges of jet Reynolds number. At Reynolds numbers <150 ± 10, no jet swinging happened. At Reynolds numbers between 150 ± 10 and 1200 ± 23, the instantaneous velocities of the merged jet presented periodic oscillations of small amplitudes and was denoted as the subcritical swinging jet. At Reynolds numbers between 1200 ± 23 and 2350 ± 50, the merged jet proceeded irregular swinging motion and was called the critical jet. At Reynolds numbers higher than 2350 ± 50, the time-evolving velocities of the merged jet presented periodic oscillations of large amplitudes imposed by large turbulent fluctuations and was termed the supercritical swinging jet. The measured results of the axial velocities and turbulence intensities in the central axis revealed that in the regime of the supercritical swinging jet, the momentum conversion from the axial to transverse direction was rapidly performed in the near field at the axial distance <2.4 times of the jet exit width due to the induced transverse jet oscillation. The transverse oscillations of the swinging jets induced large turbulence intensities and small turbulence macro time and length scales, and led to large jet mass dispersion. Therefore, the mixing characteristics of the flow was significantly improved due to large jet mass dispersion.

Flow and spreading behaviors of coaxial jets wake

Flow and spreading behaviors of swirling jets using a dual-blockage disk are studied experimentally. The control and blockage disks are placed concentrically in tandem. The smoke flow patterns are obtained using the flow visualization technique. The axial velocity and turbulence intensity are detected using a 1-D hot-wire sensor. The jet spreading characteristics are illustrated by using an Edge Detection Method. Two pairs of lung-formed vortices and triangle-formed vortices are induced in downstream wake at Rec ≤ 200. Two vortices are found near the field at 200 &lt; Rec &lt; 700, while no toroidal structure was found above the reflected jet at Rec ≥ 700. The recirculation bubble length was increased with increasing Rec until Rec &lt; 700. The axial velocity and turbulence intensity at 200 &lt; Rec &lt; 700 are significantly greater than those in other modes. At Rec ≥ 700, the shear-layer vortices are found far away from the control disk.

250 kHz three-component Doppler velocimetry at 32 simultaneous points: a new capability for high speed flows

Time-resolved Doppler global velocimetry (TRDGV) is used to demonstrate three-component velocity measurements of 32 planar points, acquired simultaneously at 250 kHz. Photomultiplier tube arrays are used to detect the flow signal, with each array having eight rows of four pixels. The system utilizes frequency scanning of a continuous wave laser, allowing for simple calibration of the signals used to determine the incident and Doppler-shifted frequency. The TRDGV system is used to measure an unheated, Mach 0.91 free jet downstream of the potential core collapse. Axial mean velocities were measured within a root-mean-square error of 7 m s−1 compared to Pitot probe validation measurements. Additionally, axial turbulence intensities showed agreement to hot wire validation measurements and exhibited typical magnitudes reported in the literature. Velocity spectra were obtained for the three components of velocity, revealing a − 5/3 decay in the axial velocity spectra in the inertial subrange frequencies, and generally less decay present in the transverse component spectra. Hot wire measurements and spectra from literature were used for validation of the TRDGV spectral results, showing broadband spectral agreement. The instrument described in this work shows promising capability for multi-point, time-resolved velocity vector measurement in high speed compressible flows with acceptable levels of uncertainty.

Diagnosing Magnetic Field Geometry in Blazar Jets Using Multi-Frequency, Centimeter-Band Polarimetry and Radiative Transfer Modeling

We use multi-frequency linear polarization observations from the University of Michigan blazar program (UMRAO), in combination with radiative transfer simulations of emission from a relativistic jet, to investigate the time-dependent flow conditions, including magnetic field geometry, in an example blazar OT 081. We adopt a scenario incorporating relativistic shocks during flaring, and both ordered axial and helical magnetic field components and magnetic turbulence in the underlying flow; these constituents are consistent with the observed periods of ordered behavior in the polarization intermixed with stochastic variations. The simulations are able to reproduce the global features of the observed light curves, including amplitude and spectral evolution of the linear polarization, during four time periods spanning 25 years. From the simulations, we identify the signature of a weak-to-strong helical magnetic field on the polarization, but conclude that a dominant helical magnetic field is not consistent with the UMRAO polarization data. The modeling identifies time-dependent changes in the ratio of the ordered-to-turbulent magnetic field, and changes in the flow direction and Lorentz factor. These suggest the presence of jet-like structures within a broad envelope seen at different orientations.