Coupled Level Set Research Articles

Shear-induced oil separation from a sand particle moving in water

Removing oil attached to fine solid particles in water purification presents challenging technical, economic, and ecological issues. The present work numerically investigates the shear effect on oil that contains a 100-μm-diameter sand particle in a water medium. In this research, we employ the coupled level set and volume of fluid method to track interface evolution accurately. An adaptive mesh refinement technique allows us to resolve an interface down to 60 nm. Computations at various particle Reynolds numbers (Rep=2−200) and oil film thicknesses (5%, 10%, 20%, and 40% of the diameter) reveal four coating behaviour scenarios: deformation, tail formation, partial separation, and full separation. The oil film negligibly deforms at Rep≤5 at most film thicknesses. The separation occurs in full or partial regimes at higher Rep and thicker films. A thinner film forms a tail that periodically fluctuates. The analysis shows that these fluctuations uniquely reshape the oil tail at each time period.

Numerical study of effective parameters on deformation and coalescence of ferrofluid droplets under uniform magnetic field

This research examines different numerical techniques for modeling ferrofluids in a non-magnetic liquid subjected to homogeneous and steady magnetic field. It particularly compares the conservative level set method with the Volume of Fluid (VOF) and Simple Coupled Level Set and Volume of Fluid (SCLSVOF) methods. By comparing these methods with experimental data, we established the superiority of the utilized method in this study. Several case studies were conducted to evaluate how a homogeneous magnetic actuation affects ferrofluid dynamics, considering parameters such as initial droplet size, surface tension coefficient, and magnetic susceptibility. Additionally, the study explored the coalescence of two falling ferrofluid droplets under the combined effects of an external magnetic field and gravity. The conservative level set method was shown to be extendable to three-dimensional environments, unlike the standard level set method. The novelty of this work lies in demonstrating that the conservative level set method is particularly effective for ferrofluids, accurately capturing their complex dynamics. The main novelty of this article lies in demonstrating the precision of Conservative Level Set Method while utilizing a reduced number of equations compared to other works. This reduction in complexity enhances the method's efficiency without compromising precision, making it especially suited for applications requiring both speed and accuracy, such as model-based control systems.

Numerical Simulation of Gas Atomization and Powder Flowability for Metallic Additive Manufacturing

The quality of metal powder is essential in additive manufacturing (AM). The defects and mechanical properties of alloy parts manufactured through AM are significantly influenced by the particle size, sphericity, and flowability of the metal powder. Gas atomization (GA) technology is a widely used method for producing metal powders due to its high efficiency and cost-effectiveness. In this work, a multi-phase numerical model is developed to compute the alloy liquid breaking in the GA process by capturing the gas–liquid interface using the Coupled Level Set and Volume-of-Fluid (CLSVOF) method and the realizable k-ε turbulence model. A GA experiment is carried out, and a statistical comparison between the particle-size distributions obtained from the simulation and GA experiment shows that the relative errors of the cumulative frequency for the particle sizes sampled in two regions of the GA chamber are 5.28% and 5.39%, respectively. The mechanism of powder formation is discussed based on the numerical results. In addition, a discrete element model (DEM) is developed to compute the powder flowability by simulating a Hall flow experiment using the particle-size distribution obtained from the GA experiment. The relative error of the time that finishes the Hall flow in the simulation and experiment is obtained to be 1.9%.

Numerical study of two equal-sized miscible drops undergoing head-on collision

The numerical analysis focuses on investigating head-on collisions between two miscible drops composed of distinct fluids, specifically ethanol and water. The simulations are performed using a coupled level set and volume of fluid approach with different Weber numbers to study the effect of drop inertia. The code is validated against experimental and numerical results from earlier investigations. Additionally, a comparative study involving both water drops and ethanol–water drops is conducted to explore the impact of varying surface tension ratios on collision outcomes. Results show that when miscible drops collide, the merged liquid drop exhibits asymmetric behavior, such as an asymmetric combined drop shape in cases of permanent coalescence or an asymmetric end droplet breakup in cases of reflexive separation. The collision outcome undergoes significant variation as the Weber number changes. At lower Weber numbers, permanent coalescence is observed, while at medium Weber numbers, reflexive separation occurs without the formation of a secondary drop. For medium to large Weber numbers, reflexive separation with the generation of one secondary drop becomes prominent, and in the case of very large Weber numbers, multiple satellite drops form. The maximum vertical elongation of the merged drop and corresponding surface energy increase as the surface tension ratio rises, irrespective of the Weber number. However, for a fixed surface tension ratio, the maximum vertical elongation and associated surface energy vary with an increase in the Weber number. The findings also shed light on the enhanced internal mixing arising from the mismatched surface tension of the colliding drops as the Weber number increases. Furthermore, the study explores the effect of drop inertia on various aspects, including asymmetric collision behavior, energy budget, and mixing index.

Computational fluid dynamics simulation of cryogenic vertical upflow boiling under Earth gravity

This study presents numerical simulations and their validation for flow boiling of liquid nitrogen (LN2) in a vertical upflow orientation, with a primary aim to understand the complex two-phase flow and heat transfer phenomena important to space applications. The computational fluid dynamics (CFD) model utilized the coupled level set volume of fluid (CLSVOF) method, incorporating additional source terms for bubble collision dispersion force and shear lift force in the momentum conservation equation to enhance simulation accuracy. The simulations were conducted for two mass velocities (G = 526 and 804 kg/m2s) and three different heat flux levels (approximately 10%, 30%, and 70% of critical heat flux (CHF) under Earth gravity. The model was validated against measured wall temperature data acquired from the authors’ previous experimental studies, demonstrating average deviations of less than 2.8 K across all operating conditions. The simulated two-phase flow contours illustrated various flow patterns, including bubbly, slug, churn, and annular. Both mass velocity and heat flux were observed to impact the onset of nucleate boiling (ONB), bubble nucleation, growth, and coalescence, and overall vapor structure. The simulations also offered insight into axial and radial void fraction and velocity profiles, revealing local flow acceleration trends synchronized with void fraction development. A comparison between predicted and measured bulk fluid temperature profiles showed excellent agreement, further validating the CFD model’s accuracy and practical usefulness for two-phase cryogenic flow boiling simulations in space applications.

Spatial characteristics study of hydrodynamics and bubble dynamics in baffled stirred tank based on CLSVOF method

The limited understanding of intricate mesoscale bubble structures in stirred tank reactors under forced convection poses significant challenges to the design and optimization of related agitation systems. In this study, the coupled level set with volume of fluid (CLSVOF) method is employed to investigate bubble dynamics and macroscopic hydrodynamics in a gas–liquid stirred tank after model validation. The results demonstrate that: i) based on the dynamics of bubble clusters within the system, the stirred tank can be categorized into four distinct regions: the dispersal region, accumulation region, rising wall-region, and reflex region; ii) in the dispersal region, the rear of impeller blade generates large-scale vortex. Two merging modes are identified during the bubble rupture process: the merging of bubbles at adjacent orifices and the merging of discrete bubbles with the back of impeller blade due to negative pressure. Two bubble breakup modes are observed: bubble breakup at the back of the impeller blade due to stretching and the breakup of bubbles growing at orifices due to disturbance caused by the impeller blade; iii) the inertial forces predominantly control most bubbles in the system. A predictive correlation for bubble velocity is proposed; iv) elevating the stirring speed increases bubble number in the accumulation region. Moreover, enlarging gas flow rate and fluid viscosity leads to a discernible augmentation of overall bubble size; v) at the macroscopic scale, the radial, axial, and tangential velocities of the system exhibit an increase with enlarging stirring speed, while showing no significant change with the increase in gas flow rate. Additionally, as fluid viscosity and density increase, the flow undergoes a transition from turbulent flow to laminar flow.

Morphology and heat transfer of a train of microdroplets impinging on the heated surface for spray cooling

Owing to the superior cooling performance of the droplet impingement process, the spray cooling is widely used in various industries including aerospace, e-motors, data centres and so on. In the present study, the morphological evolution and heat transfer characteristics of vertical and oblique impacts on the heated surface were investigated experimentally and numerically. A droplet generation system and a substrate heating system were designed to observe continuous vertical and oblique droplets impinging on the hot surface by a high-speed camera. The coupled Level Set and VOF (CLS-VOF) model and adaptive mesh refinement technique were used to establish a mathematical model for a train of micro-sized droplets impinging on the heated surface, which was validated by experimental data. The film that spreads on the surface exhibits asymmetry due to the horizontal velocity of the droplets. When continuous droplets impinge vertically on the heated wall, the evolution of the crown and the wall temperature appear periodic. The effects of impingement angles on morphological patterns and heat transfer of a train of micro-sized monodispersed droplets with the same Weber numbers were analyzed further. The results indicated that with a smaller angle of impingement, the crown is more likely to splash, and the crown asymmetry is less obvious.

A mass-momentum consistent THINC-scaling scheme for CLSVOF method on co-located grid

Accurate numerical simulation of practical two-phase flows characterized by high density ratios are indeed challenging as spurious interfacial currents may disrupt the solution. To address such complexities, the present work considers a conservative discretization of the incompressible Navier-Stokes equation that advects the mass and momentum consistently on a co-located grid. An algebraic Coupled Level Set and Volume Of Fluid (CLSVOF) approach, based on THINC (Tangent of the Hyperbola for INterface Capturing)-scaling scheme is used to capture the interface. The numerical methodology relies on a balanced treatment of the pressure and other interfacial forces at the discrete level while emphasizing a compatible calculation of mass and momentum fluxes. Effectiveness of the present Consistent Mass-Momentum Transport (CMMT)-based THINC-scaling method is demonstrated by the thorough numerical analysis of advection of a high density drop. The obtained results signify the requirement of a balanced force CMMT framework for accurate and stable simulation of multiphase flows. Furthermore, performance of the present in-house multiphase solver is evaluated from practical tests like capillary wave, dam break, bubble rise and Rayleigh-Taylor instability. The present work is significant as it presents the capability of the CMMT-based THINC-scaling method to resolve precise interface profiles while preserving close to second order spatial accuracy.

Flow film boiling on a sphere in the mixed and forced convection regimes

Saturated flow film boiling on a sphere has been numerically studied in this work for both vertical and horizontal flow configurations. The simulations were performed using a numerical methodology developed by the authors for boiling flows on three-dimensional unstructured meshes. For interface capturing, the coupled level set and volume of fluid method is used. The interface evolution, vapour wake dynamics and heat transfer have been thoroughly investigated by varying the saturated liquid flow velocity, sphere diameter and wall superheat. The relative importance of both the buoyancy and the inertial forces is described in terms of the Froude number $(Fr)$ . The vapour bubble evolves periodically at low $Fr$ values, while a stable vapour column develops at high $Fr$ values. The interface evolution pattern obtained in the present work is in good agreement with the results of experimental studies available in the literature. For all the values of $Fr$ , a stable vapour column develops for a large-diameter sphere and releases vapour bubbles of varying sizes. Furthermore, for a large-diameter sphere, surface capillary waves are observed at the interface, similar to the observations of some of the experimental studies available in the literature. The flow in the liquid and vapour wakes appears to be strongly coupled. The heat transfer in the present work is estimated using the spatially and temporally averaged Nusselt numbers. Finally, an fast Fourier transform analysis of the space-averaged Nusselt number reveals a strong interaction among the different forces.

Air-Film Coupling in Prefilming Airblast Atomisers and the Implications for Subsequent Atomisation

AbstractPrefilming airblast atomisers are commonly used in gas turbine combustion system fuel injectors. As the film propagates across the prefilmer it interacts with the high velocity gas stream above it. In this paper a numerical investigation into this interaction is presented. A Coupled Level Set & Volume of Fluid method is used to simulate the development of the film along the KIT-ITS planar prefilmer (Gepperth et al., in: 23rd European conference on liquid atomization and spray systems (ILASS-Europe 2010), Brno, Czech Republic, September, 2010). Initial results showed the importance of correctly specifying the contact angle as too high a value leads to the formation of rivulets instead of a continuous film. An analysis of the film and air showed two-way coupling. The presence of the film increases the growth rate of the gas phase boundary layer, and the strength and size of the turbulent structures within it. Surface waves form in the film, initially driven by the turbulent fluctuations, but developing into transverse waves. These waves are shown to be independent, stochastic events instead of a periodic wave system. At the trailing edge of the prefilmer the increased turbulence level in the air, the variations in the film thickness and the associated change in fuel mass flow and momentum will have large implications for the atomisation process and subsequent fuel spray. These will also impact simulation of the atomisation, as the boundary condition complexity is much greater than commonly used, and the variations will require larger domains and longer simulation times to obtain fully converged atomisation statistics.

Numerical Simulation of Friction Stir Welding of Dissimilar Al/Mg Alloys Using Coupled Level Set and Volume of Fluid Method.

The coupled level set and volume of fluid (CLSVOF) method is proposed to simulate the material distribution and physical properties during dissimilar aluminum/magnesium friction stir welding (FSW) process more accurately. Combined with a computational fluid dynamics model, the FSW process is numerically simulated and the heat transfer and material flow are analyzed. The results show that heat transfer and material flow have great influence on the Al/Mg bonding. In order to verify the accuracy of the model, the calculated results based on different methods are compared with the experimental results, and the Al/Mg interface simulated by the CLSVOF method is in better agreement with the experimental results. Finally, the material distribution and interface evolution near the tool at different times were studied based on the CLSVOF method.

Full-scale study on the coupling settling behavior of droplets and PM10 particles based on the CLSVOF method and wetting experiments

Coal mines produce large quantities of dust during production and transportation of coal, especially respirable particulate matter of diameter < 10 µm (PM10). This not only jeopardizes the health of workers but also pollutes the environment. Currently, spraying is the most commonly used dust reduction technology. Traditional spraying techniques use pure water; however, the wetting and condensing of dust by pure water droplets is poor, resulting in low dust reduction efficiency. To address this issue, we used orthogonal tests to determine the optimal ratio of composite dust-reducing agents. Using the coupled level set and volume of fluid (CLSVOF) method, we investigated the dynamic wetting process of PM10 when using solutions of dust-reducing agents. We found that a particle size ratio of ≥ 2 and an initial velocity of droplets of 20–40 m/s resulted in optimal wetting and encapsulation of dust particles by droplets. We then conducted macroscopic experiments and found that the settling efficiency of PM10 reached 88.98 % when using a 1.5-mm caliber fine atomizing nozzle and a spray pressure of 6 MPa. Our findings reveal the dynamic wetting law of droplets and dust during the process of spray dust reduction, which could lead to improved efficiency of dust-reducing agents and better management of respirable dust. These findings will help to improve clean production in coal mines and the occupational health of coal miners.

Dynamics of oil separation from sand particle moving in the water at the Reynolds number of 500

This work represents studies of bitumen separation from a single bitumen-coated sand particle moving in a stream of water at the particle Reynolds number of 500. The transient dynamics of separation processes are calculated numerically using a three-dimensional computational fluid dynamics based model coupled with the combination of level set and volume of fluid models, known as the coupled level set volume of fluid model. The sand particle diameter is 10−4 m. The bitumen layer thickness comprises 10% of the particle diameter. The simulation results show that 20% of bitumen is removed during the onset of the water flow around the particle. Further, a bitumen layer is transformed into a bitumen tail with 77% of the original bitumen volume.

The Effect of Film Development on Primary Breakup in a Prefilming Airblast Atomizer

Abstract Liquid fueled gas turbines are likely to remain a dominant force in aviation propulsion for the foreseeable future, and therefore understanding the atomization process is key to meeting future emissions and performance legislation. To make experiments and simulations possible, simplified geometry and boundary conditions are often used, for example, simulations of primary atomization often use a fixed film height and velocity. This paper aims to quantify the effect of a fully developed unsteady film on the atomization process. A custom Coupled Level Set &amp; Volume of Fluid (CLSVOF) solver with adaptive meshing built in OpenFOAM v9 is used. A simulation of the atomization process in the Karlsruhe Institute of Technology atomization experiment (Warncke et al., 2017, “Experimental and Numerical Investigation of the Primary Breakup of an Airblasted Liquid Sheet,” Int. J. Multiphase Flow, 91, pp. 208–224) is presented. A precursor simulation of the film development is used to provide accurate, temporally and spatially resolved inlet boundary conditions. These results are compared to previous CLSVOF simulations from Wetherell et al. (2020, “Coupled Level Set Volume of Fluid Simulations of Prefilming Airblast Atomization With Adaptive Meshing,” ASME Paper No. GT2020-14213)” using traditional boundary conditions. The unsteady film has doubled the modal ligament length and widened the distribution, and is now in better agreement with experimental measurements. A clear correlation in both time and space is observed between the film, atomization process, and spray. The sauter mean diameter (SMD) is significantly increased, again giving better agreement with the experiment. A discussion of extracting statistical descriptions of the spray is given, outlining the unfeasible computational cost required to converge droplet diameter distributions and other high order statistics for a case such as this.

Experimental and Computational Investigation of Flow Boiling in a 52 μm Hydraulic Diameter Microchannel Evaporator With Inlet Restrictions and Heat Spreading

Abstract Microchannel flow boiling presents an effective thermal management strategy for high heat flux (&amp;gt;1 kW/cm2) devices. Fundamental mechanisms of microchannel flow boiling behaviors are difficult to determine due to macroscopic limitations of experimental hardware. In addition, flow stabilizing features of microchannel evaporators such as inlet restrictions and heat spreading further complicate fluid flow and heat transfer dynamics. Computational models, when utilized with experiments, can provide a more detailed understanding of behaviors which cannot be determined experimentally. The present study developed a computational model for flow boiling heat transfer in a 52 μm silicon microchannel evaporator designed to cool a laser diode bar, with inlet restrictions and a nonuniform heating profile at the channel level. A conjugate heat transfer model along with a coupled level set and volume of fluid (CLSVOF) model was created in ansysfluent and compared with experimental flow boiling data to gain further insights into the performance of a realistic microdevice. Heat spreading in the channel outside of the heater footprint was observed due to the high thermal conductivity of the silicon substrate. The inlet orifices impacted local flow patterns by creating a large pressure drop and forming a recirculation zone immediately downstream. This behavior resulted in pressure recovery zones and regions of separated flow boiling behavior. Bubbly, slug, and churn flows were seen to be dominant flow regimes. The heat transfer coefficient was found to be dependent on heat flux and flow regime, and more weakly on mass flux and outlet vapor quality.

Numerical simulation of macroscopic viscoelastic melt filling and mesoscopic spherulite growth

Abstract In this work, a non-isothermal viscoelastic computational framework is proposed for macroscopic polymer melt filling and mesoscopic spherulite growth. Firstly, the macroscopic viscoelastic governing equation is solved by coupled level set immersed boundary and finite-volume (LS-IB-FV) method. The melt-air interface is captured by the coupled level-set and volume-of-fluid (CLSVOF) method. And the mesoscopic crystallization behavior is predicted by the phase field model. Then, the numerical simulation for melt filling process is compared with experimental one to validate the coupled method. And it is simulated that the melt filling stage in a complex annular cavity with 17 small solid discs for the semi-crystalline polymer of isotactic polystyrene, and it is studied that the impacts of three different injection velocities on the flow modes, temperature distribution and solidified layers. Finally, in the regions of solidified layers, the growth of spherulites is simulated with/without melt flows at two different points. Numerical results show that the injection velocities can affect the flow modes and temperature distribution significantly. The morphology of polymer spherulite that is consistent with the experimental result can be observed clearly. With flow fields, the spherulites grow faster and densely towards the upstream direction.

Numerical investigation on the effects of wave suppression baffles in vehicle-integrated water tanks

The danger of liquid sloshing in pump-driven water tanks has significantly increased due to the growing need to integrate a water tank into new energy vehicles. The best approach to reduce the negative effects of liquid sloshing is to add baffles to the integrated water tank. The addition of baffles to integrated water tanks to reduce liquid sloshing is investigated in this study using the discontinuous mesh approach and the coupled level set and volume of fluid (CLSVOF) method. Comparative experiments and simulations are used to confirm the reliability of the method. In this study, the length ratio, distance to initial free surface, and angle of the added baffle are taken into consideration. The free surface height, magnitude velocity, turbulence energy, and flow field are used to assess the impact of the baffle on the suppression of liquid sloshing. The addition of baffles can improve the liquid sloshing phenomenon caused by the pump excitation conditions in the integrated water tank, increase the volume suction of liquid, inhibit the height of the wave and reduce the liquid flow rate in the tank. Also, at the depth where the baffle has the most obvious suppression effect, the deeper the baffle, the lower the height of the free surface in the tank and the lower the average magnitude velocity in the tank cross-section. The baffle reduces the height of the free surface in the tank to 6.39 mm, and the magnitude of maximum average velocity in the tank cross-section is reduced to 0.12 m/s.

Simulation of the Asphaltene Deposition Rate in Oil Wells under Different Multiphase Flow Condition

As the wellbore pressure falls below the bubble point pressure, the light components in the oil phase are liberated, forming additional vapor, and the single-phase flow becomes a gas–liquid two-phase flow. However, most studies simplify the multiphase flow to a single-phase flow to study asphaltene deposition in wellbores. This assumption under multiphase conditions may lead to inaccurate prediction results and a substantial economic and operational burden for the oil and gas industry. Therefore, it is crucial to predict the deposition rate of asphaltene in a multiphase flow to assist in minimizing this issue. To do so, the volume of fluid coupling level-set (VOSET) model was used to obtain the flow pattern (bubble, slug, churn, and annular) in the current work. In the next step, the VOSET + k-ε turbulent + DPM models were used to simulate asphaltene deposition in a multiphase flow. Finally, the effects of different parameters, such as the gas superficial velocity, liquid superficial velocity, particle diameter, interfacial tension, viscosity, and average deposition rate, were investigated. The findings revealed that the maximum average deposition rate of asphaltene particles in a bubble flow is 1.35, 1.62, and 2 times that of a slug flow, churning flow, and annular mist flow, respectively. As the apparent velocity of the gas phase escalates from 0.5 m/s to 4 m/s, the average deposition rate experiences an increase of 82%. Similarly, when the apparent velocity of the liquid phase rises from 1 m/s to 5 m/s, the average deposition rate is amplified by a factor of 2.1. An increase in particle diameter from 50 μm to 400 μm results in a 27% increase in the average deposition rate. When the oil–gas interfacial tension is augmented from 0.02 n/m to 0.1 n/m, the average deposition rate witnesses an 18% increase. Furthermore, an increase in crude oil viscosity from 0.012 mPa·s to 0.06 mPa·s leads to a 34% increase in the average deposition rate. These research outcomes contribute to a deeper understanding of the asphaltene deposition problem under multiphase flow conditions and offer fresh perspectives on the asphaltene deposition issue in the oil and gas industry.

An improved Coupled Level Set and Volume of Fluid (i-CLSVoF) framework for sessile droplet evaporation

Surface-tension-dominant droplet evaporation is ubiquitous and of importance to many applications. We present an improved Coupled Level Set and Volume of Fluid (i-CLSVoF) framework without explicit interface reconstruction for modelling micro-sized droplets with and without evaporation. In the i-CLSVoF framework, an improved surface tension force model with additional filtering steps to filter un-physical spurious velocities is developed and implemented. A simple, yet efficient, velocity-potential based approach is proposed to reconstruct a divergence-free velocity field for the advection of the free surface during droplet evaporation. This approach fixes the numerical issues resulting from the evaporation-induced velocity jump at the interface. The smeared mass source term approach incorporated in this work guarantees greater numerical stability than the non-smeared approach. Three different evaporation models (constant mass flux, thermally driven evaporation and droplet evaporation at room temperature) are implemented in the i-CLSVoF. Corresponding numerical benchmark cases (dam break, droplet relaxation and droplet evaporation subjected to different evaporation models) are conducted to validate the surface tension and the evaporation models. Good agreement between the numerical and corresponding analytical solutions is found. The model developed in this work shows convincing performance in modelling surface-tension-dominant flow with and without evaporation.

A coupled level-set and volume-of-fluid (CLSVOF) method for prediction of microgravity flow boiling with low inlet subcooling on the international space station

The present study is part of a series of NASA-supported investigations of flow boiling of n-perfluorohexane (n-PFH, C6F14) under microgravity on the International Space Station (ISS). The fluid physics and heat transfer characteristics of flow boiling with low inlet subcooling are explored using the Flow Boiling and Condensation Experiment (FBCE) (which is actual name of the test facility), the largest endeavor in microgravity two-phase research conducted to date. Experimental data are collected from the FBCE's Flow Boiling Module (FBM), which features a rectangular channel with 5.0-mm x 2.5-mm cross-section and 114.6-mm heated length. Results for three flow rates are used to explore the effects of mass velocity on flow structure and heat transfer characteristics in the absence of the body force. A Computational Fluid Dynamics (CFD) model is constructed to predict the measured FBM results. The CFD model employs the Coupled Level-Set and Volume-of-Fluid (CLSVOF) method, which is modified with improved interface capture and additional force terms in the momentum equation to determine the bubble dynamics more accurately. Validity of the CFD model is assessed in two ways, by comparing predictions against video-captured interfacial behavior and heat transfer data. The CFD model shows good ability to capture detailed evolution of the interfacial structure both across and along the flow channel, including bubble nucleation, growth, departure, and coalescence, as well as axial development of dominant flow patterns. Details of the flow structure are examined via axial development of both flow velocity and void fraction profiles. Similarly, heat transfer results are presented in terms of streamwise variations of both wall temperature and fluid temperature, which are also predicted accurately with the CFD model. Overall, this study proves the CFD model is an effective method for both design and performance assessment of flow boiling subsystems in space vehicles.