Simulation Of Three-dimensional Flow Research Articles

Predicting aerodynamic pressure on a square cylinder from wake velocity field by masked gated recurrent unit model

A masked gated recurrent unit (GRU) model is proposed to establish the mapping relationship between surface pressures on a square cylinder and wake velocities, which can be used to predict statistical and instantaneous aerodynamic pressure fields on a square cylinder from its wakefield. A novel mask net is proposed to figure out one or two wake points where the velocities contribute dominantly to the surface pressure field. A three-dimensional unsteady large-eddy simulation of flow around a square cylinder is performed at Re = 22 000 to generate data for training and validating the proposed models. Results show that local mean pressure coefficients can be well predicted from velocities at even one wake point, but the accuracies of predicting fluctuating pressure coefficients and time-series of local pressure coefficients depend on both the model and the surface pressure location, with more satisfactory predictions achieved in the cross-flow direction. High correlation coefficients of pressure coefficient distributions around a square cylinder between predicted and real distributions are achieved except for the masked GRU model with one wake point. Meanwhile, in terms of the temporal correlation coefficient, all models exhibit good prediction of time-series of pressure coefficients on the side and back surfaces where they are strongly affected by vortex shedding and lower accuracy on the front surface where the pressure coefficients deviate somewhat randomly around the mean value. Large prediction error occurs at the corners of the square cylinder. This study has potential application to risk analysis of structures subject to flow-induced loads.

Comparison of one-dimensional and three-dimensional glottal flow models in left-right asymmetric vocal fold conditions.

While the glottal flow is often simplified as one-dimensional (1D) in computational models of phonation to reduce computational costs, the 1D flow model has not been validated in left-right asymmetric vocal fold conditions, as often occur in both normal and pathological voice production. In this study, we performed three-dimensional (3D) and 1D flow simulations coupled to a two-mass model of adult male vocal folds and compared voice production at different degrees of left-right stiffness asymmetry. The flow and acoustic fields in 3D were obtained by solving the compressible Navier-Stokes equations using the volume penalization method with the moving vocal fold wall as an immersed boundary. Despite differences in the predicted flow pressure on vocal fold surface between the 1D and 3D flow models, the results showed reasonable agreement in vocal fold vibration patterns and selected voice outcome measures between the 1D and 3D models for the range of left-right asymmetric conditions investigated. This indicates that vocal fold properties play a larger role than the glottal flow in determining the overall pattern of vocal fold vibration and the produced voice, and the 1D flow simplification is sufficient in modeling phonation, at least for the simplified glottal geometry of this study.

Hole number effect on internal and discharged flow characteristics of diesel injector during transient operation

Selecting the proper number of nozzle holes is a critical matter to achieving optimal combustion in diesel engines. In recent years, short transient injections with ultra-high injection pressure have been adopted in diesel engines to achieve cleaner combustion but the effect of hole number on this transient diesel injection has not been thoroughly investigated. The current study performs an experimental observation of discharged flows from diesel injectors during transient operation using the X-ray phase-contrast imaging technique for six multi-hole injectors (three-, five-, six-, eight-, nine- and ten-hole). The observation results showed that discharged flows varied without any distinctive trends among the injectors. The largest spray dispersion angle and fastest velocity deceleration were observed in the 3-hole injector which showed an almost 3 times larger dispersion angle and 10% faster deceleration than the 10-hole injector. To understand possible factors governing such flow characteristics, three-dimensional internal flow simulations were conducted for the injectors. Unlike the results trend of discharged flows, the pressure and vorticity magnitude in the nozzle sac showed a linear change by altering the hole number. However, the hole-to-hole interaction of vortex flows varied in a complex way depending on the nozzle hole number. The nozzles with small and odd hole numbers, in general, showed a stronger hole-to-hole vortex interaction that can be the primary factor governing the discharged flow characteristics during the transient operation.

Two- and three-dimensional simulations of flow and heat transfer around rectangular cylinders

This numerical study investigates the forced convection heat transfer from and flow topology around isothermal rectangular cylinders. The effects of various cross-sectional aspect ratios (AR = 0.25–4), Reynolds numbers (Re = 30–200), and Prandtl numbers (Pr = 0.7, 5) are examined on the results. Two or three-dimensional simulations are conducted depending on the Re and AR employed. The results show that the near primary vortices (Kármán wake) undergo a downstream transition to the two-layered vortices, followed by a transition from the two-layered vortices to the secondary vortices for AR ≤ 1. For smaller aspect ratios, the prevailing of the secondary vortices is further accelerated, i.e., they emerge at a lower Re and a shorter downstream distance from the cylinder. Three types of secondary vortices distinguished based on their shape, strength, and generation mechanism were observed. A geometric criterion (spacing ratio) for the onset of evolution of the two-layer structure is proposed for each AR. It is observed that the sensitiveness of the Nusselt number to AR and Re can be ascribed to the change in the scenarios of the flow separation and reattachment (flow regimes), vortex strength, and wake-recirculation size (Lr). The Nusselt number grows with increasing Re and Pr but diminishes with AR. The relationship between the average Nusselt number and Lr is direct in the steady flow, while they are inversely linked in the two- and three-dimensional unsteady flow. Reducing AR from 4 to 0.25, depending on Re and Pr, leads to a 90%–170% enhancement in the Nusselt number, whereas increasing AR amplifies the total heat transfer due to an enlargement in the heat transfer surfaces. The second law of thermodynamics analysis reveals that cylinders with smaller AR generate lower entropy (destroy lower exergy); therefore, they are more efficient.

3D MODELING OF TURBULENT FLOWS USING LES AND RANS APPROACHES BASED ON FILTERED EXPEDITION DATA

The article describes the developed software that made it possible to process a large amount of data from observations of the movement and parameters of the aquatic environment in the Sea of Azov, which was obtained during expeditionary research using the ADCP hydrophysical probe, using the filtration procedure. The filtering procedure significantly reduces the spread of data and the amplitude of fluctuations, which, in turn, makes it possible to more adequately evaluate the information obtained during field experiments. For different filter widths, a box filter, a Gauss filter and a Fourier filter were used. In these calculations, the filter width was set based on the size of the hydrodynamics problem to be solved and the grid scale corresponding to this size. The obtained data are planned to be used for numerical simulation of three-dimensional turbulent flows using the LES approach and comparison with the results of averaging by RANS.

Influence of Different Flow Solvers and Off-Design Conditions On the Determination of Fan-Rotor Wakes for Broadband Noise Prediction

Abstract The acoustic interaction of fan-rotor wakes with the downstream stator vanes is considered as an important noise source of an aircraft engine. The turbulence induced by the rotor generates a stochastic acoustic source that appears as broadband noise in the acoustic spectrum. During the preliminary design phase of an engine, established meanline and throughflow solvers usually do not resolve turbulence and associated unsteady flow parameters. But such solvers provide rotor pressure losses that can be used to estimate the mean and turbulent rotor wakes. A crucial step is the deduction of turbulence parameters from the mean wakes. A semi-empirical model for rotor-wake turbulence estimation is presented in this paper. The meanline method and the throughflow solver are compared to three-dimensional computational flow simulations investigating the capabilities of the different solvers to provide flow data for broadband wake interaction noise prediction. The methods are applied to a representative modern fan stage at a comprehensive number of operating points, comprising several speed lines from surge to choking conditions. Microphone measurements are consulted to assess the noise predictions. The evaluation confirms the applicability of the meanline and throughflow method in combination with the turbulence model for broadband noise estimation during the preliminary design phase. The underestimated turbulence in the tip region of the fan is found to be negligible even during off-design conditions.

Vertical and torsional vibrations before the collapse of the Tacoma Narrows Bridge in 1940

We perform a three-dimensional direct numerical simulation of flow over the Tacoma Narrows Bridge to understand the vertical and torsional vibrations that occurred before its collapse in 1940. Real-scale structural parameters of the bridge are used for the simulation. The Reynolds number based on the free-stream velocity and height of the deck fence is lower ( ${Re}=10\ 000$ ) than the actual one on the day of its collapse ( ${Re}=3.06 \times 10^{6}$ ), but the magnitude of a fluid property is modified to provide the real-scale aerodynamic force and moment on the deck. The vertical and torsional vibrations are simulated through two-way coupling of the fluid flow and structural motion. The vertical vibration occurs from the frequency lock-in with the vortex shedding, and its wavelength and frequency agree well with the recorded data in 1940. After saturation of the vertical vibration, a torsional vibration resulting from the aeroelastic fluttering grows exponentially in time, with its wavelength and frequency in excellent agreement with the recorded data of the incident. The critical flutter wind speed for the growth of torsional vibration is obtained as $3.56 < U_c / (f_{nat} B) \le 4$ , where $U_{c}$ is the critical flutter wind speed, $f_{nat}$ is the natural frequency of the torsional vibration and $B$ is the deck width. Finally, apart from the actual vibration process in 1940, we perform more numerical simulations to investigate the roles of the free-stream velocity and vertical vibration in the growth of the torsional vibration.

Three-dimensional numerical simulation of heat transfer and flow of waxy crude oil in inclined pipe

The purpose of this study is to obtain the heat transfer and flow law of waxy crude oil in the inclined pipeline and to provide theoretical guidance for the safe operation of the pipeline. In this paper, three-dimensional numerical simulation of pipes with inclination angles of 0°, 25 °and 45 °is carried out by using CFD software. The temperature and velocity fields of waxy crude oil and the cooling gelation law of crude oil are basically the same in different cases. Affected by the initial temperature field of shutdown, the average temperature of horizontal pipeline decreases gradually along the flow direction of pipeline. The inclined pipe is mainly affected by the natural convection caused by gravity, and the temperature decreases gradually along the downward direction of the inclination of the pipe. The inclination angle of the pipe increases to 45°, the temperature difference between the highest and lowest points of the pipe increases to 5.012 °C, and the liquid volume fraction increases by 1.6%. Among them, the low-lying pipe section is more likely to cause pipeline blockage.

Global linear stability analysis of the flow inside a conical draft tube

The paper presents the numerical simulations of the flow inside the draft tube of Francis-99 turbine at the part load (PL) operating condition. The rotating vortex rope (RVR) is a phenomenon that occurs during the PL operating regime inside the draft tube of hydraulic turbines. To reduce the computational cost, the numerical simulations are carried out in two steps. Firstly, steady state numerical simulations are performed in a reduced geometry of the runner which is made of a runner passage and part of the draft tube. The velocity profiles from the steady state simulation are used as a boundary condition for unsteady numerical simulation on the inlet of the full draft tube geometry. The velocities from the numerical simulations are time-averaged over a period of 5 RVR rotations and validated with the experimental velocities averaged over the same period. Further, a two-dimensional (2D) linear global stability analysis is performed on a plane extracted from the cone of the draft tube using the time-averaged flow. The frequency of three-dimensional (3D) flow simulation and of the 2D stability analysis are found to be in good agreement with the experimental frequency.

Multi-objective optimization of guide vane closure scheme in clean pumped-storage power plant with emphasis on pressure fluctuations

In this study, multi-objective optimization was conducted for the guide vane closure scheme during the load-rejection process of a pump turbine, considering pressure fluctuation, maximum rotational speed, maximum pressure at the volute, and minimum pressure at the draft tube inlet to decrease the low-frequency high-amplitude pressure fluctuations at conditions near no-load. Two quantitative indicators, minimum discharge (Qmin) and the ratio of rotational speed to hydraulic head (NDH) of the pump turbine, were proposed to represent the backflow-induced pressure fluctuations. Two objective functions were defined to optimize the guide vane closure scheme and two optimized guide vane closure schemes, OPS-Q (based on Qmin) and OPS-NDH (based on NDH), were developed. The enhancements resulting from these vane closure schemes were verified using a one-dimensional–three-dimensional coupling flow simulation method. NDH was revealed to comprehensively represent backflow-induced pressure fluctuations, whereas Qmin partially represented the backflow. Consequently, OPS-NDH suppressed the pressure fluctuations by appropriately increasing the maximum pressure at the volute and the maximum vacuum at the draft tube inlet within the allowance ranges of the pumped-storage power plant. OPS-Q suppressed the pressure fluctuations; however, the minimum pressure at the draft tube inlet could not be controlled to satisfy the design requirements of the pumped-storage power plant. The findings of this study can be used as a theoretical reference for suppressing the pressure fluctuations in a clean pumped-storage power plant under near-no-load conditions.

An enhanced mesoscale model for laminar and turbulent three-dimensional simulations of the gas phase flow with concentration mixing in structured packing columns

This work presents a mesoscale model (MSM) simulating the laminar and turbulent gas phase fluid dynamics and concentration mixing in structured packings, used in absorption and distillation columns or static mixers. The MSM aims to provide computationally efficient predictions of the three-dimensional distributions of pressure, velocity and concentration in the structured packing’s gas phase. The MSM is successfully calibrated and validated with virtual experiments obtained from DNS (direct numerical simulations) of a single structured packing section featuring concentration mixing under uniform and maldistributed velocity inlet profiles. The packing section scenarios exhibit a variety of physical effects, like backflow, high-velocity fronts and blockage at the packing’s borders to the wall, which are all predicted correctly by the MSM. The physical effects have an impact on concentration mixing and velocity smoothing and are particularly interesting for applications of structured packings in dividing-wall columns or static mixers. Finally, the MSM is set up to simulate cylindrical columns with alternately rotated structured packing sections, including wall regions and wipers. MSM simulations of three packed columns of varying diameter are compared against experimental data and correctly predict the pressure drop dependence on the diameter, demonstrating the MSM’s potential for scale-up predictions.

The effect of static chamber base on N2O flux in drip irrigation

Abstract. Static chambers are commonly used to provide in situ quantification of nitrous oxide (N2O) fluxes. Despite their benefits, when left in the field, the physicochemical conditions inside the chamber's base may differ from the ambient, especially in drip-irrigated systems. This research aimed to study the effects of static chamber bases on water and N distribution and the subsequent impact on N2O fluxes. N2O emissions were measured in a drip-irrigated avocado orchard for 2 years, using bases with a dripper at their center (In) and bases installed adjacent to the dripper (adjacent). During the irrigation and fertigation season, the measured N2OIn fluxes were greater than the N2OAdjacent fluxes (0.015 ± 0.003 vs. 0.006 ± 0.001 g m−2 d−1). By contrast, during the winter, when the orchard is not irrigated or fertilized, insignificant differences were observed between the measured N2OAdjecent and N2OIn fluxes. Three-dimensional simulations of water flow, N transport, and N transformations showed two opposing phenomena: (a) increased water contents, N concentrations, and downward flushing when the dripper is placed inside the base, and (b) hampering of the lateral distribution of water and solutes into the most bio-active part of the soil inside the base when the base is placed adjacent to the dripper. It also showed that both “In” and “adjacent” practices underestimate the “true” cumulative flux from a dripper with no base by ∼ 25 % and ∼ 50 %, respectively. A nomogram in a non-dimensional form corresponding to all soil textures, emitter spacings, and discharge rates was developed to determine the optimal diameter of an equivalent cylindrical base to be used along a single dripline. Further studies under variable conditions (soil types, wetting patterns, nutrient availabilities), rather than a single study, are needed to test the constructiveness of the suggested methodologies.

Characteristics of thermal plume from an array of rectangular straight fins with openings on the base in natural convection

Straight rectangular fins with openings in the base surface in natural convection exhibit greater heat transfer than rectangular fins without openings in the base. In this paper, thermal plume arising from such fin configuration used as a heat sink for natural convection cooling of light-emitting diode (LED) grow lights is investigated using three-dimensional conjugate laminar flow simulations. Understanding of plume characteristics is crucial in optimizing the cooling performance as well as optimal placement of grow lights from ceilings and walls in proximity. A prototype LED grow light was designed and experimentally measured to assess the cooling performance, and numerical simulations were conducted to investigate the plume structure. The results showed that openings in the base enhanced vertical draft of air, mixing, and overall heat transfer rate. It was found that local pressure gradient is proportional to the degree of mixing of ambient air into the plume. Low pressure regions around the fins and channels showed upward convection of plume mass and a high pressure region below the fins indicated higher concentration of denser air mass. High pressure gradients were observed in the openings, which further justifies the significance of openings in improving mixing of ambient air with the plume to enhance heat transfer.

Turbulent flow simulations of the common research model on Cartesian grids using recursive fitting approach

In this study, we propose a new method that uses the recursive fitting method and wall function for the three-dimensional turbulent flow simulation. The recursive fitting method based on the Cartesian grid method is employed for the automatic generation around two- and three-dimensional geometries. The grid approximately represents the concave and convex features, i.e., a wing–fuselage juncture and wing trailing edges. The wall boundary conditions can be imposed on the wall faces; thus, the conservation laws are strictly satisfied. Meanwhile, using the wall function allows turbulent boundary layers to be accurately reproduced. The turbulent flow simulation using the wall function is straightforward because the flow variables at the first cell centroid are employed for friction velocity estimation. However, the distance between the body surface and the first cell centroid varies since cells with different shapes are generated. Therefore, the simulation using the proposed method is validated through turbulent flow simulations in two dimensions. The results show the accurate predictions of the turbulent boundary layers. To investigate the capacity of the proposed method, three-dimensional simulation around aircraft at a transonic cruise condition is conducted. The automatically generated grids by the proposed method approximately represent the geometric features. The results of flow simulation show that the surface pressure and skin friction coefficient distributions agree with those of the reference simulation on a conventional body-fitted grid. Further, predicted pressure and viscous drag coefficients are reasonable compared with those of the reference simulation.

On the origin of mode B instability of the wake of a square cylinder

Three-dimensional numerical simulations of flow passing a square cylinder are performed using a spectral element method. Reynolds numbers of 200 and 300, corresponding to modes A and B, respectively, are used to study the two- to three-dimensional transition of the wake flow. It is shown that the wake transition occurs in the early time prior to the onset of the vortex shedding event. For mode A, the spanwise instability grows exponentially downstream of the cylinder with constant wavelength in the early time dynamics and continues after the vortex separation. However, in the case of mode B, the exponential amplification reaches a saturation state before the vortex separation occurs. A splitting of the initially obtained wavelength of the spanwise instability occurs and is related to the splitting of spanwise vortical structures, which develops at the cores of the separation bubbles prior to the vortex shedding.

Non-isothermal non-Newtonian three-dimensional flow simulation of fused filament fabrication

This work investigates three-dimensional simulation of fused filament fabrication using the Cross-WLF model for the non-isothermal and shear thinning behavior of the melt. To realistically simulate the deposition flow, the acceleration, viscosity evolution, and flow front tracking models have been included with the pressure gradient in the deposited road and boundary modeling of the melt and air interface. The results indicate that the non-isothermal and shear thinning behaviors greatly affect the geometry of the deposited roads including the flow front and trailing cross-section shapes. The thermal footprint of the interface between the deposited melt and the substrate is also predicted as a function of the thermal contact conductance. The pressure distribution within the deposited road is also modeled and is found to be not symmetric with respect to the nozzle center-line. Rather, the pressure peak shifts slightly downstream due to redirection of the melt around a stagnation point opposite the nozzle exit. Furthermore, a negative stress is observed downstream the exterior nozzle face associated with the free expansion of the melt as the extruded material climbs and releases from the exterior nozzle face. The developed simulation is verified by comparison with experimental results providing contact pressures ranging from 5 to 132 kPa.

Speaker-wire vortices in stratified anabatic Prandtl slope flows and their secondary instabilities

Stationary longitudinal vortical rolls emerge in katabatic and anabatic Prandtl slope flows at shallow slopes as a result of an instability when the imposed surface buoyancy flux relative to the background stratification is sufficiently large. Here, we identify the self-pairing of these longitudinal rolls as a unique flow structure. The topology of the counter-rotating vortex pair bears a striking resemblance to speaker-wires and their interaction with each other is a precursor to further destabilization and breakdown of the flow field into smaller structures. On its own, a speaker-wire vortex retains its unique topology without any vortex reconnection or breakup. For a fixed slope angle $\alpha =3^{\circ }$ and at a constant Prandtl number, we analyse the saturated state of speaker-wire vortices and perform a bi-global linear stability analysis based on their stationary state. We establish the existence of both fundamental and subharmonic secondary instabilities depending on the circulation and transverse wavelength of the base state of speaker-wire vortices. The dominance of subharmonic modes relative to the fundamental mode helps to explain the relative stability of a single vortex pair compared to the vortex dynamics in the presence of two or an even number of pairs. These instability modes are essential for the bending and merging of multiple speaker-wire vortices, which break up and lead to more dynamically unstable states, eventually paving the way for transition towards turbulence. This process is demonstrated via three-dimensional flow simulations with which we are able to track the nonlinear temporal evolution of these instabilities.

Development of an OpenFOAM solver for numerical simulations of shell-and-tube heat exchangers based on porous media model

• An innovative OpenFOAM solver of shell-and-tube heat exchangers was developed. • The coupling between porous media and drift flux two phase model was realized. • The feasibility of new solver was validated by two international benchmarks. • The key three dimensional thermal parameters of heat exchanger were achieved. As one of the most widely used types of heat exchangers, the shell-and-tube heat exchanger (STHX) offers the advantages of being low-cost, easy to clean, and highly reliable under high pressure and temperature conditions. Generally, a large number of tube bundles are used in the STHX to increase the heat transfer capacity. The three-dimensional (3D) two-phase flow simulation of the STHX is made exceedingly difficult if the tube bundle region is full-size modeled. Therefore, simplified models and approaches are required to meet the urgent demands of STHX engineering numerical simulation, especially for 3D analyses. Herein, we have developed an OpenFOAM solver “PorousDriftFoam” suitable for the two-phase flow and the boiling heat transfer numerical simulation of the STHX. The porous media model was applied to simplify the tube bundle region and the drift-flux model (DFM) was adopted in the two-phase flow computational fluid dynamics (CFD) simulation for the STHX. The heat transfer tubes are regarded as the solid region of porous media, while the shell side is considered the fluid region. We calculate the coupling heat transfer between the tube and the shell sides and consider the resistance introduced by the heat transfer tubes and support plates in the STHX. Two international benchmarks, the FRIGG test and the MB-2 experiments, were selected to fully validate the solver. For the FRIGG experiment, the predicted void fraction stands in good agreement with the experimental data, with an average absolute error of 0.07 and an average relative error of 13.3%. For the MB-2 experiment, the predicted values of pressure drop and temperature fit well with the experimental data. The developed solver could be applied in the 3D two-phase flow and heat transfer numerical simulation of a typical STHX in the industry.

Resistance Loss in Cemented Paste Backfill Pipelines: Effect of Inlet Velocity, Particle Mass Concentration, and Particle Size.

Cemented paste backfill (CPB), a technology placing the solid waste into mined-out stopes in the mine through pipeline transportation, has been widespread all over the world. The resistance loss is an important parameter for pipeline transport, which is significantly affected by the slurry characteristics. However, the coupling effect of inlet velocity (IV), particle mass concentration (PMC), and particle size (PS) has not been well evaluated and diagnosed. Hence, the CFD-based three-dimensional network simulation of CPB slurry flow in an L-shaped pipe at different combinations of the three parameters was developed using COMSOL Multiphysics software, and the findings were validated through a loop experiment. The results show that increasing IV and reducing PS will contribute to the homogeneity of the slurry in the pipeline, while the PMC presents little effect. The pipe resistance loss is positively correlated with IV and PMC and negatively correlated with PS. The sensitivity to the three parameters is IV > PS > PMC. In particular, the resistance loss is minimal at IV of 1.5 m/s, PMC of 72%, and PS of 1000 um. The calculation model of resistance loss regressed from simulation presented a high accuracy with an error of 8.1% compared with the test results. The findings would be important for the design of the CPB pipeline transportation and provide guidance in the selection of transfer slurry pumps, prepreparation of backfill slurry, and pipe blockage, which will improve the safety and economic level of a mine.

Two-Phase Flow Simulations of Liquid/Gas Transport in Radial Centrifugal Pumps With Special Emphasis on the Transition From Bubbles to Adherent Gas Accumulations

Abstract In recent optical flow experiments on a transparent volute-type radial centrifugal pump, an accumulation of air bubbles to adherent gas pockets within the impeller blade channels was observed. A transition of unsteady bubbly flow toward an attached gas pocket at the blade suction side was found for increasing air loading of the liquid water phase. This steadily attached pocket shows a distinctive unsteady wake. A reproduction of the transition from bubbly to pocket flow in a three-dimensional (3D) flow simulation demands the treatment of dispersed bubbly flow, on the one hand, and of coherent air regions, on the other hand. Therefore, a hybrid flow solver is adopted based on an Euler–Euler two-fluid (EE2F) method for dispersed flows and features volume-of-fluid (VOF) properties when air accumulations form. A scale-adaptive simulation (SAS) turbulence model is utilized to account for highly unsteady flow regions. For the time being, a monodisperse bubble size distribution is assumed for the dispersed part of the flow. For an operation range close to the design point and rising air loading, the flow transition from bubbly to pocket flow is well captured by the hybrid simulation method. Even an alternating pocket flow in between bubbly and pocket flow regime is predicted. The simulation method is still limited by an appropriate choice of a monodisperse bubble diameter. Therefore, the disperse model part of the hybrid flow solver will be coupled with population balance and bubble interaction models in future studies.