Coupled Computational Fluid Dynamics Research Articles

Optimum design of stenter machine hot air supply chamber by coupling CFD & DOE

The efficiency of the textile hot air-drying process fundamentally requires the uniformity of the airflow that impinges on the textile fabric. Optimization of a stenter machine’s hot air supply chamber shape was conducted in this paper, based on the actual real-size model and considering both the outlet flow uniformity and the standard velocity deviation as responses. The purpose is to improve the airflow uniformity at the chamber outlet, and modifications applied to the baseline must be applicable to both old and next-generation stenter machines. Coupled Computational Fluid Dynamics and Design of Experiment (CFD-DoE) optimization on the stenter machine chamber geometry was carried out. The CFD model was validated by measuring the chamber outlet velocity using a 2D velocity scanner. After choosing seven factors based on mechanical manufacturing and fluid dynamics theories, a main effect screening design was conducted to highlight relevant factors that influence the outlet airflow distribution. By fixing the best categorical factors, a central composite design (CCD) was applied using three other continuous factors to generate a quadratic prediction model that could be used to simultaneously maximize and minimize the uniformity index (UI) and the standard deviation (SD), respectively. With the embedded JMP SAS desirability function, the optimal value was calculated based on a statistical approach. Those values were used to design an optimal stenter air supply chamber that has been simulated with Fluent CFD code to validate the statistical prediction model. Finally, optimized geometry was obtained and experimentally validated. Results show that this new chamber improved by 16.48% for the uniformity index and 38.07% for the standard deviation.

A hybrid domain overlapping method for coupling System Thermal Hydraulics and CFD codes

A hybrid multiscale coupling methodology based on a domain overlapping approach has been developed for coupling System Thermal Hydraulics (STH) and Computational Fluid Dynamics (CFD) codes. The method has been implemented between the modern STH code SAM and the CFD code NekRS, using the coupling tool Cardinal. The coupling aims to extend the STH code’s applicability to scenarios where local momentum and energy transfers are important yet difficult for STH codes to capture, such as three-dimensional mixing.Two coupling strategies are implemented and compared: a hybrid domain overlapping method and the conventional domain decomposition method. The strategies are applied to two closed-loop applications, and the present method shows superior stability behavior when compared to the domain decomposition method. Then, the present coupling method is validated against experimental data from a double T-junction experiment. The present STH/CFD coupling shows improved agreement with experimental data when compared to STH standalone simulations.

Optimization of the Thermal Environment of Large-Scale Open Space with Subzone-Based Temperature Setting Using BEM and CFD Coupling Simulation

A cruise ship, which has large-scale open spaces, has an uneven cabin thermal environment in the cruise public space, leading to overcooling or poor cooling issues. Therefore, optimizing the thermal environment of public spaces during a cruise should be the priority. According to the space functions of the cruise ship, the large public space is divided into three subzones: the entertainment area (Subzone I), the round-table dining area (Subzone II), and the square-table dining area (Subzone III). To create a uniform, stable, and comfortable thermal environment, this study proposes a subzone-based temperature setting approach to independently adjust the thermal environment of each subzone. Coupling simulation of building energy modeling (BEM) and computational fluid dynamics (CFD) was adopted in this study to determine proper temperature setpoints of the subzones under different occupancy rates. The results indicate that, compared with a single-temperature setpoint for the entire public space, the subzone-based temperature setpoints could achieve a uniform thermal environment. The average temperature difference among the three subzones was 0.68 °C. Moreover, the airflow between two adjacent subzones considerably affected the BEM results of energy consumption of the air-conditioning system.

Fluid-structure interaction analysis on the response of open-top, squat, circular tank due to wind-driven rain

Wind-driven rain (WDR) is a natural phenomenon, which occurs, when rain droplets descend through a wind flow field, creating an angle with the vertical and affects any structure by impingement through the structural envelope. Existing literatures on wind-driven rain effect on structure, are focused on building envelop only. There is a huge scope, left unexplored, on studying the interaction response of squat, open top, circular tank with wind-driven rain. This available scope is the main motivation of the present authors behind this study. The present study has been conducted through fluid–structure interaction (FSI) analysis, by coupling computational fluid dynamics (CFD) analysis of a multi-phase fluid system involving air and water to simulate wind-driven rain, with the mechanical analysis of the tank structure, by importing the wall pressure, assessed from CFD model of WDR. This study is focused on ground-supported, open-top, squat, circular tank with a slenderness ratio of 0.5. The internal and external pressure distributions on the tank wall have been assessed for WDR and compared with the same caused by wind. The radius (R): thickness (t) ratio of the tank wall has been varied from 125 to 500, in order to understand the impact of wind-driven rain on the tank wall deformation. The comparative study of pressure distribution between WDR and wind (only) cases clearly demonstrates that the wall pressure (internal and external) due to wind-driven rain, is higher than wind (only). It has been observed that the wall deformation is showing an incremental pattern with the decrement of wall thickness. The maximum deformation zone has been observed at the upper half of the frontal area. Higher deformation zone for R/t ratios 500, 250, 166.67, and 125, can be seen for 0° to 40°, 0° to 37°, 0° to 35°, and 0° to 32°, peripherally.

Shear stress and plaque microenvironment induce heterogeneity: A multiscale microenvironment evolution model

BackgroundBoth clinical images and in vivo observations have demonstrated the heterogeneity in atherosclerotic plaque composition. However, the quantitative mechanisms that contribute to the heterogeneity, such as the wall shear stress (WSS) and the interplays among microenvironmental factors are still unclear. MethodsWe develop a multiscale model coupling computational fluid dynamics, interactions of microenvironmental factors and evolutions of cellular behaviors to investigate the formation of plaque heterogeneity in a three-dimensional vessel segment. The model involves WSS, lipid deposition and inflammatory response to reveal the dynamic balance existed between the lipid metabolism and the phagocytosis of macrophages. ResultsThe dynamic balance in microenvironment is influenced by both the WSS and the interactions with microenvironmental factors, and consequently results in the longitudinal heterogeneity observed in plaque pathology. In addition, plaque heterogeneity can be reduced by decreasing low WSS area at downstream, as well as by altering the phagocytic abilities of macrophage on lipoproteins, which may be used to develop future plaque regression strategies. ConclusionsThis multiscale modeling provides a framework to understand the mechanisms in dynamics of plaque composition and also provides quantitative information to better risk stratification of plaque vulnerability in future clinical practice.

Development and Design of the First Industrial Magnetohydrodynamic Slag-Cleaning Reactor From Execution and Analysis of Pilot Plant Tests Through Coupled CFD Simulations

The future challenge for copper smelters is to increase metal yield by reducing copper losses and valorizing the slag as a marketable by-product. This can be achieved through further slag cleaning in a conventional submerged arc furnace (SAF) where remaining metallic oxides are reduced, and metal droplets have more settling time. Nevertheless, a significant amount of copper matte and metallic copper is still present as slight inclusions that cannot settle through the slag layer under simple gravity after SAF treatment. This work presents the development of a new industrial type of slag-cleaning concept, based on the magnetohydrodynamic (MHD) principle, that can be coupled downstream of conventional slag-cleaning technology (e.g., electric reduction furnace). The cleaning efficiency and operating conditions were evaluated in several pilot test campaigns using a SAF supplemented by an externally applied magnetic field (electromagnet), which interacts with electrodes generating Lorentz forces, which are responsible for an MHD stirring effect. In order to simulate experimental conditions and thus understand reaction kinetics and settle mechanisms during pilot tests, this work includes computational fluid dynamics (CFD) models. In order to represent these electromagnetic conditions, the focus of this work is to develop a new coupled CFD model. Numerical simulations showed the interactions between MHD flow field, slag properties, and metal recovery in an industrial slag-cleaning reactor and demonstrated the MHD cleaning effect on non-ferrous slags.

Open-source simulation of strongly-coupled fluid-structure interaction between non-conformal interfaces

Design code-based “life-safety” requirements for structural earthquake and tsunami design offer reasonable guidelines to construct buildings that will remain standing during a tsunami or seismic event. Much less consideration has been given to assessing structural resilience during sequential earthquake and tsunami multi-hazard events. Such events present a series of extreme loading scenarios, where damage sustained during the earthquake influences structural performance during the subsequent inundation. Similar difficulties exist with respect to damage sustained during tropical events, as wind and fluid loading may vary with structural response or accumulated damage. To help ensure critical structures meet a “life-safety” level of performance during such multi-hazard events, analysis software capable of simulating simultaneous structural and fluid dynamics must be developed. To address this gap in understanding of non-linear fluid-structure-interaction (FSI), an open-source tool (FOAMySees) was developed for simulation of tsunami and wave impact analysis of post-earthquake non-linear structural response of buildings. The tool is comprised of the Open-source Field Operation And Manipulation software package and OpenSeesPy, a Python 3 interpreter of OpenSees. The programs are coupled via preCICE, a coupling library for partitioned multi-physics simulation. FOAMySees has been written to work in a Linux OS environment with HPC clusters in mind. The FOAMySees program offers a partitioned conventional-serial-staggered coupling scheme, with optional implicit iteration techniques to ensure a strongly-coupled two-way FSI solution. While FOAMySees was developed specifically for tsunami-resilience analysis, it may be utilized for other FSI applications with ease. With this coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) program, tsunami and earthquake simulations may be run sequentially or simultaneously, allowing for the evaluation of non-linear structural response to multi-hazard excitation.

Effects of the mouthpiece and chamber of Turbuhaler® on the aerosolization of API-only powder formulations

Powder dispersion in dry powder inhalers (DPIs) is affected by powder formulations as well as the design of a device. This paper conducted a numerical investigation based on the coupled computational fluid dynamics (CFD) and discrete element method (DEM) to evaluate the changes of the design of a commercial DPI device Turbuhaler® on the aerosolization of an API-only formulation. Six different designs were proposed by modifying the mouthpiece and chamber of the original geometry which was reconstructed from a CT-scan of the Turbuhaler, and their performances in terms of powder deposition in the device and fine powder fraction (FPF) were evaluated. The resistance of the device was observed to vary with different designs. For the change of the mouthpiece, the device with a cylindrical mouthpiece had the least resistance and the lowest FPF emitted among all the devices, confirming the important role of the spiral mouthpiece on powder dispersion. Reducing the mouthpiece size caused more powder deposition in the inhaler due to higher airflow velocity, but FPF emitted increased compared to the original design as more powder dispersion occurred inside the mouthpiece. The half-length mouthpiece design reduced device resistance to increase airflow velocity and average collision energy, resulting in an increase in FPF loaded but a decrease in the number of collisions. For the change of the chamber, the domed chamber design increased the powder dispersion time and thus enhanced the frequency and energy of particle collisions, which eventually led to an increase in FPF loaded. At fixed flow rates, the powder dispersion efficiency was a function of the device resistance with higher device resistance causing an increase in the FPF loaded. However, it is important for the patient’s attainable pressure drop to be considered in this context. Correlations between the aerosolization efficiency and the ratio of the average collision energy and cohesion energy were established based on model-predicted quantities.

Aeroelastic analyses of functionally graded aluminium composite plates reinforced with graphene nanoplatelets under fluid-structural interaction

This study presents a comprehensive investigation on functionally graded (FG) graphene reinforced aluminium cantilever rectangular plates under aerodynamic loads. Two-way loosely coupled fluid structure interaction (FSI) is implemented by coupling finite element analysis (FEA) and computational fluid dynamics (CFD). FEA models are developed using FG graphene nanoplatelets (GPL) reinforced aluminium composite structures with different GPL distribution patterns. Fluid domain is modelled using finite volume method and FSI module is then used to connect FEA with the CFD code. The simulation results of FSI indicate that the maximum stress of the plate can be efficiently reduced with satisfactory aerodynamic performance after aeroelastic tailoring, depending on specific GPL distribution patterns. It is shown that in conjunction with aeroelastic tailoring technique, the composite plate can achieve optimized structural and aerodynamic performance. The present results of the FG graphene reinforced aluminium plates offer useful design guideline for their applications as the structural components in aeronautical fields.

Modelling Flocculation in a Thickener Feedwell Using a Coupled Computational Fluid Dynamics–Population Balance Model

The flocculation that takes place in the central feedwell of the thickener plays a crucial role in the coal-slurry thickening process, which is not only complex but also largely influenced by the flow characteristics. A coupled computational fluid dynamics–population balance model (CFD–PBM) was used to model the complex flocculation-thickening behaviour in an industrial-scale gravity thickener. The initialisation parameters of the inlet flow were obtained through self-designed image-recognition experiments, and then the effects of different types of conical deflectors on the floc distribution were simulated and analysed using them. The results showed that, under the condition that the angle of the conical deflector’s sides in the vertical plane was known, a reasonable increase in the height of the bottom surface could reduce the annular spanwise vortices at the underflow of the feedwell, thereby avoiding the erosion of the inlet flow and the annular spanwise vortex on the floc deposition layer. However, excessive height on the part of the conical deflector could affect the flocculation effect of solid particles. For the same central feedwell size of the thickener as in the simulation, the best flocculation effect was achieved at an angle of α = 24° in the vertical plane of the conical deflector. Turbulence regulation of the conical deflector promotes the aggregation of fine particles in the fluid of the feedwell, providing a new method for the intensification of the flocculation-concentration process.

Effects of Particle Diameter and Inlet Flow Rate on Gas-Solid Flow Patterns of Fluidized Bed.

The complex multiscale characteristics of particle flow are notoriously difficult to predict. In this study, the evolution process of bubbles and the variation of bed height were investigated by conducting high-speed photographic experiments to verify the reliability of numerical simulations. The gas-solid flow characteristics of bubbling fluidized beds with different particle diameters and inlet flow rates were systematically investigated by coupling computational fluid dynamics (CFD) and discrete element method (DEM). The results show that the fluidization in the fluidized bed will change from bubbling fluidization to turbulent fluidization and finally to slugging fluidization, and the conversion process is related to the particle diameter and inlet flow rate. The characteristic peak is positively correlated with the inlet flow rate, but the frequency corresponding to the characteristic peak is constant. The time required for the Lacey mixing index (LMI) to reach 0.75 decreases with increasing inlet flow rate; at the same diameter, the inlet flow rate is positively correlated with the peak of the average transient velocity; and as the diameter increases, the distribution of the average transient velocity curve changes from "M" to linear. The results of the study can provide theoretical guidance for particle flow characteristics in biomass fluidized beds.

Investigation of the Heat Storage Capacity and Storage Dynamics of a Novel Polymeric Macro-Encapsulated Core-Shell Particle Using a Paraffinic Core

Thermal energy storages represent important devices for the decarbonisation of heat; hence, enabling a circular economy. Hereby, important tasks are the optimisation of thermal losses and providing a tuneable storage capacity, as well as tuneable storage dynamics for thermal energy storage modules which are composed of either sensible or phase change-based heat storage materials. The thermal storage capacity and the storage dynamics behaviour are crucial for fulfilling certain application requirements. In this work, a novel macro-encapsulated and spherical heat storage core-shell structure is presented and embedded in a supercritical ammonia working fluid flow field. The core of the macro-capsule is built by an organic low molecular weight substance showing a solid–liquid phase transition in a respective temperature zone, where the shell structure is made of polyvinylidene fluoride. Due to the direct coupling of computational fluid dynamics and the simulation of the phase transition of the core material, the influence of the working fluid flow field and shell thickness on the time evolution of temperature, heat transfer coefficients, and accumulated heat storage is investigated for this newly designed material system. It is shown that due to the mixed sensible and phase change storage character, the shell architecture and the working fluid flow field, the heat storage capacity and the storage dynamics can be systematically tuned.

Numerical study of the thermo-mechanical behavior of steel–timber structures exposed to fire

The latest trends in the construction industry related to sustainable buildings, has driven the use of timber as a construction material. One example is the continuous increase of timber structural elements made of Cross-Laminated Timber (CLT) walls and floors. In this context, Steel–Timber Composite (STC) floors, composed of CLT slabs and steel beams, represent a new alternative to traditional floor systems. Some advantages of STC structures are a reduction of the building mass and better thermal insulation, among others. Despite these benefits, the response of timber structures under a fire scenario remains a consistent concern. To address this issue, in this paper the thermo-mechanical response of STC structures exposed to fire is investigated. To this end, a one way coupled Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) approach was employed. The software Fire Dynamics Simulator (FDS) was used for the CFD fire analyses and ANSYS for the FEM transient heat transfer and thermo-mechanical analyses. Three different STC floor structural configurations, having similar pre-fire performance, were proposed to assess their response when subjected to a given fire scenario. A representative room of a residential building was defined to simulate an accidental fire scenario to which the STC floor structures were exposed. The material properties and fire features were adopted in accordance with the Eurocode Standard and recent investigations found in the literature. The results indicated that after a 30 min fire exposure the CLT slabs showed a 25 mm thick charred layer on their exposed surface. Furthermore, compression failure was identified in the CLT slab upper fibres. Regarding to the steel beams, local buckling, and fracture in the area next to the end supports was observed. Overall, STC structures with closed cross sections steel beams showed a better fire performance than those that included open cross sections such as I-shaped ones.

Degradation of soil arching caused by suffusion in gap-graded soils

To investigate evolution of soil arching during suffusion in gap-graded soils, a new suffusion apparatus was developed for trapdoor tests under a horizontal seepage flow. Glass beads with fine-grain contents ranging from 15% to 45% were adopted to represent coarse-grain controlled soils and fine-grain controlled soils. Coupled computational fluid dynamics (CFD) and discrete element method (DEM) models were developed to further investigate the evolution of soil arching from microscopic views. At the early stage of suffusion, soil arching degraded rapidly under seepage loads in both coarse-grain controlled and fine-grain controlled soils due to the compaction of soil skeleton and the clogging of voids, which increased in the number of fine particles connected to the stress-transfer matrix. At the later stage, soil arching was nearly maintained as the soil skeleton became stable in the coarse-grain controlled soils. In the fine-grain controlled soils, soil arching degraded continuously due to continuous loss of fine particles connected to the stress-transfer matrix. The decrease in the contact number of fine particles also made the soil skeleton more vulnerable to suffusion. The degradation of soil arching resulted in an increase of surface displacement and a decrease of soil arching height in fine-grain controlled soils.

A Hybrid, Runtime Coupled Incompressible CFD-CAA Method for Analysis of Thermoacoustic Instabilities

Abstract Thermoacoustic instabilities in gas turbine engines are of increasing interest for design of future low-emission technology combustors. Numerical methods used to predict thermoacoustic instabilities often employ either fully compressible resource-intense computational fluid dynamics (CFD) simulations, or two-step approaches where source terms extracted from CFD simulations are supplied to subsequent computational aeroacoustics (CAA) simulations. This work demonstrates an analysis of self-excited thermoacoustic instabilities using a hybrid method based on runtime coupling of incompressible CFD and CAA simulations. A prior implementation for the computation of combustion noise through one-way coupling of CFD and CAA solvers has been extended to a two-way coupling that allows acoustics to influence the flow field. The resulting hybrid method couples acoustic and convective physical phenomena by using mean flow field quantities and the thermoacoustic energy source term obtained from the solution of the Navier–Stokes equations in the low Mach number limit as an input for the acoustic perturbation equations (APEs). The fluctuating acoustic quantities pressure and velocity obtained from the solution of the APE are in turn included in the solution of the low Mach number Navier–Stokes equations, influencing the convective dynamics of the flow field. The suitability of the present implementation to capture thermoacoustic feedback is demonstrated through analysis of the well-known self-excited instability observed in a Rijke tube. The results are presented and discussed in comparison with a fully compressible reference solution.

Performance improvement of a Wells turbine through an automated optimization technique

• A new and efficient Wells turbine blade geometry is proposed. • Computational Fluid Dynamics is coupled with multi-objective optimization tool. • Influence of ring-type endplate is quantified. • Improvement of peak torque coefficient by up to 120% & efficiency by up to 9% The present article reports optimization of the performance of a Wells turbine, which is an axial turbine utilized for wave energy conversion, through a computational fluid dynamics (CFD) based automated optimization technique. The in-house optimization library OPAL++ was coupled to a commercial CFD solver to get the Pareto front defining the relationships between two objectives. Four different geometric parameters of the turbine with ring-type endplate were used, and the objectives were to maximize the torque coefficient and simultaneously minimize the pressure drop coefficient. From the Pareto front, two designs (G1 and G2) were chosen for further analysis. G1 improved the peak torque-coefficient by more than 120% and delayed the stall point from φ = 0.225 to φ = 0.3, while the peak efficiency dropped. Whereas, G2 improved the peak efficiency by 9.1%, but the peak torque coefficient was reduced by about 50%. The main contribution of the study is to develop an optimum Wells turbine geometry through the coupling of CFD and automated optimization algorithm - first of its kind applied to a Wells turbine with endplate. A detailed flow analysis, the influence of the endplate, and a comparison of the optimized geometries are presented.

Surrogate modeling of pressure loss & mass transfer in membrane channels via coupling of computational fluid dynamics and machine learning

Spacers are integral to the operation of membrane systems for both structural purposes and improving mass transfer dynamics that drive water permeation at the cost of increased pressure losses. 321 computational fluid dynamics (CFD) simulations were performed to provide high-fidelity data on hydrodynamic and mass transport behavior of spacer-filled membrane channels. CFD simulations were used to investigate the impact of the geometric parameters of spacers on pressure loss and concentration polarization in membrane channels. Spacer designs were characterized using six parameters that were varied in simulations to sample the domain of commercially available designs. Machine learning models were trained on CFD data to produce surrogate models for predicting pressure loss and mass transfer coefficients. These surrogate models consider more geometric parameters than existing empirical equations resulting in more representative and flexible models that can be integrated into existing module-scale or system-scale modeling software. Surrogate models were coupled with a particle swarm optimization algorithm and found that spacer designs with a diameter of 0.3 mm, length of 3.6 mm, angle between 42 and 46°, and moderate diameter necking (~60 %) best balances the trade-off between reduced concentration polarization and increased pressure losses in membrane channels with channel velocities between 0.05 and 0.35 m/s.

A Fully Coupled CFD-DMB Approach on the Ship Hydroelasticity of a Containership in Extreme Wave Conditions

In this paper, we present a fully coupled computational fluid dynamic (CFD) and discrete module beam (DMB) method for the numerical prediction of nonlinear hydroelastic responses of a ship advancing in regular and focused wave conditions. A two-way data communication scheme is applied between two solvers, whereby the external fluid pressure exported from the CFD simulation is used to derive the structural responses in the DMB solver, and the structural deformations are fed back into the CFD solver to deform the mesh. We first conduct a series of verification and validation studies by using the present CFD–DMB method to investigate the global ship motion, vertical bending moments (VBMs), and green water phenomenon of the ship in different regular wave conditions. The numerical results agreed favourably with the CFD–FEA model and experimental measurements. Then, the extreme ship motions are studied in focused wave conditions to represent extreme sea conditions that a ship may experience in a real sea state. According to the conclusion drawn from the numerical simulations, it is founded that the focused wave case will lead to the increase of the longitudinal responses of the hull compared to regular wave condition, i.e., the heave, pitch, and total VBMs rise about 25%, 20% and 9%, respectively. In focused wave conditions, intensive ship responses and severe waves cause stronger slamming phenomena. It is found that the instantaneous impact pressure from the focused wave is higher and sharper compared to the regular waves and comes along with the obvious green-water-on-deck phenomena.

A computational framework for guiding the MOCVD-growth of wafer-scale 2D materials

Reproducible wafer-scale growth of two-dimensional (2D) materials using the Chemical Vapor Deposition (CVD) process with precise control over their properties is challenging due to a lack of understanding of the growth mechanisms spanning over several length scales and sensitivity of the synthesis to subtle changes in growth conditions. A multiscale computational framework coupling Computational Fluid Dynamics (CFD), Phase-Field (PF), and reactive Molecular Dynamics (MD) was developed – called the CPM model – and experimentally verified. Correlation between theoretical predictions and thorough experimental measurements for a Metal-Organic CVD (MOCVD)-grown WSe2 model material revealed the full power of this computational approach. Large-area uniform 2D materials are synthesized via MOCVD, guided by computational analyses. The developed computational framework provides the foundation for guiding the synthesis of wafer-scale 2D materials with precise control over the coverage, morphology, and properties, a critical capability for fabricating electronic, optoelectronic, and quantum computing devices.

Effect of Operating Parameters on the Coalescence and Breakup of Bubbles in a Multiphase Pump Based on a CFD-PBM Coupled Model

When the multiphase pump is running, the internal medium often exists as bubble flow. In order to investigate the bubble occurrence characteristics in the pressurization unit of the multiphase pump more accurately, this paper couples computational fluid dynamics (CFD) with a population balance model (PBM) to investigate the bubble size distribution law of the multiphase pump under different operating conditions, taking into account the bubble coalescence and breakup. The research shows that the mean bubble size in the impeller domain gradually decreases from 1.7013 mm at the inlet to 0.6179 mm at the outlet along the axis direction; the average bubble diameter in the diffuser domain fluctuates around 0.60 mm. The bubbles in the impeller region gradually change from the trend of coalescence to the trend of breakup along the axial and radial directions, and the bubbles in the diffuser tend to be broken by the vortex entrainment. The bubble size development law is influenced by the inlet gas volume fraction (IGVF) and the rotational speed, showing a more obvious rule, where the gas phase aggregation phenomenon enhanced by the increase in IGVF promotes the trend of bubble coalescence and makes the bubble size gradually increase. The increased blade shearing effect with the increase in rotational speed promotes the trend of bubble breakup, which gradually reduces the size of the bubbles. In addition, increasing the bubble coalescence probability is a key factor leading to changes in bubble size; the bubble size development law is not very sensitive to changes in flow, and the bubble size is at its maximum under design conditions. The research results can accurately predict the performance change of the multiphase pump and provide technical guidance for its safe operation and optimal design.