Laminar Model Research Articles

A Data-Driven Approach for Generalizing the Laminar Kinetic Energy Model for Separation and Bypass Transition in Low- and High-Pressure Turbines

Abstract No common laminar kinetic energy (LKE) transition model has to date been able to predict both separation-induced and bypass transition, both phenomena commonly found in low-pressure turbines and high-pressure turbines. Here, a data-driven approach is adopted to develop a more general LKE transition model suitable for both transition modes. To achieve this, two strategies are adopted. The first is to extend the computational fluid dynamics (CFD)-driven model training framework for simultaneously training models on multiple turbine cases, subject to multiple objectives. By increasing the training data set, different transition modes can be considered. The second strategy employed is the use of a newly derived set of local non-dimensionalized variables as training inputs to reduce the search space. Because one of the training turbine cases is characterized by strong unsteady effects, for the first time an unsteady solver is utilized during the CFD-driven training, and the time-averaged results are used to calculate the cost function as part of the model development process. The results show that the data-driven models do perform better, in terms of their predictions of pressure coefficient, wall shear stress, and wake losses, than the baseline model. The models were then tested on two previously unseen testing cases, one at a higher Reynolds number and one with a different geometry. For both testing cases, stable solutions were obtained with results improved over the predictions using the baseline models.

Effect of two-phase flow lubrication on sealing performance of spiral groove mechanical seal under high speed and low temperature conditions

The function of the turbo-pump shaft within the liquid rocket engine is rendered exceedingly complex due to the operation in an environment characterized by drastically low temperatures, elevated velocities, and high pressures. Given these operational conditions, it is highly plausible that a two-phase flow might form within the liquid film located on the terminal face of the mechanical seal. This liquid-vapor mixture significantly modifies the fluid lubrication pattern across the end faces and poses consequential implications on the overall sealing stability. In this study, the phase change characteristics of the fluid in the seal clearance were investigated based on the Laminar and Mixture multi-phase flow models in a spiral groove mechanical seal. The behaviors of two-phase flow characteristics and phase transition under extreme temperature, rotational speed and pressure with liquid nitrogen media were studied. The sealing performance was quantified through metrics including the leakage rate, opening force, and internal gas phase volume ratio. The findings offered valuable insights into the role of operational conditions in influencing the phase change of the liquid film. Moreover, we discerned and explicated the intricate interconnections between the leakage rate, the opening force, and the phase change behavior of the liquid film.

An Eulerian–Lagrangian particle method for weakly compressible viscous flows using peridynamic differential operator

This study proposes a peridynamic differential operator (PDDO)-based Eulerian–Lagrangian hybrid particle method for weakly compressible viscous flows. The PDDO is utilized to transform the governing partial differential equations into their integral form; hence, the issue of local non-differentiability is eliminated. Both the Eulerian and Lagrangian formulations of particle methods for solving the governing integral equations are derived and then combined to propose the hybrid method. In the proposed method, the Eulerian and Lagrangian formulation is utilized to solve the governing equations in the inner computational domain and in areas with free surfaces, respectively. The results of these two domains are then merged to arrive at the solution. In such a way, the hybrid particle method effectively balances the computational demands and applicability. The numerical stability and interpolation consistency of the proposed method are shown by introducing the laminar viscosity model. A detailed numerical procedure is provided involving the boundary conditions and time-stepping strategy. The proposed method is validated by several benchmark problems. Furthermore, the method was applied to several benchmark problems including the hydrostatic test, Taylor–Green vortex, and numerical wave generation. The results of these numerical examples suggest that the proposed method is computationally less demanding while maintaining accuracy.

Numerical Simulation of the Influence of Non-Uniform ζ Potential on Interfacial Flow.

Zeta potential (ζ potential) is a significant parameter to characterize the electric property of the electric double layer (EDL), which is important at the solid-liquid interface. Non-uniform ζ potential could be developed on a chemically uniform solid-liquid interface due to external flow. However, its influence on the flow has never been concerned. In this investigation, we numerically studied the influence of non-uniform 2D ζ potential on the flow at the solid-liquid interface. It is found, that even without any external electric field and only considering the influence of 2D ζ potential distribution, swirling flow can be generated near EDL, according to the rotational electric volume force. The streamwise vortices, which are important in the turbulent boundary layer, are theoretically predicted in this laminar flow model when considering the 2D distribution of ζ potential, implying the necessity of considering the origin of streamwise vortices of the turbulent boundary layer from the perspective of electrokinetic flow. In addition, the ζ potential distribution can promote the wall shear stress. Therefore, more attention must be paid to shear-sensitivity circumstances, like biomedical, medical devices, and in vivo. We hope that the current investigation can help us to better understand the effect of charge distribution on interfacial flow and provide theoretical guidance for the development of related applications in the future.

The generalized Riemann problem scheme for a laminar two-phase flow model with two-velocities

In this paper, we propose a generalized Riemann problem (GRP) scheme for a laminar two-phase flow model. The model takes into account the distinctions between different densities and velocities, and is obtained by averaging vertical velocities across each layer for the two-phase flows. The rarefaction wave and the shock wave are analytically resolved by using the Riemann invariants and Rankine-Hugoniot condition, respectively. The source term is incorporated into the resolution of the GRP method. We further extend the GRP method to the two-dimensional (2-D) system, which is non-conservative. The Strang splitting method is applied, but it still can not provide explicit Riemann invariants and shock relations, which prevent us to apply the GRP method directly. Another splitting technique is also applied to the 2-D case, such that each split subsystem contains only one family of waves. Numerical experiments on some typical problems show that the proposed method achieves good performance.

Thermal performance of a solar water tank with variable inlet/outlet under various charging strategies

The plummet of the inflow temperature could cause dramatic temperature mixing during the charging process in a solar water storage tank, resulting in severe destruction of thermal stratification. To address this issue, two new charging strategies are proposed in this paper for the water tank with variable inlet and outlet ports. We study the charging process of the tank under various strategies using Computational Fluid Dynamics (CFD) simulation and assess the thermal performance improvement according to the numerical comparisons and theoretical analysis. A laminar numerical model considering gravity effect is built based on the experimental platform and is well validated against the experimental data. Energy and exergy analysis are conducted to evaluate the impact of the strategies on the thermal performance of the solar charging. The findings show that both the proposed charging strategies substantially mitigate the temperature mixing caused by the port switch and achieve a better thermal stratification with the reduction in exergy destruction by over 30%. Strategy A maintains better thermal stratification during the charging process, while strategy B prevails in inhibiting the temperature mixing after port switches. Nevertheless, the improvement in the overall thermal performance is relatively modest with the increment of less than 1% in energy efficiency and 0.02 in exergy efficiency.

Thermal enhancement of microchannel heat sink using pin-fin configurations and geometric optimization

The microchannel heat sink (MCHS) is a robust cooling technique that ensures the efficiency and reliability of compact electronic devices by dissipating a large amount of heat because of its high surface area-to-volume ratio. This study proposes a novel modification of the pin-fins geometry in MCHS, and geometric optimization using response surface methodology (RSM) to build a low thermal resistant MCHS with enhanced heat transfer efficiency with low-pressure drop. Three dimensional numerical simulations using ANSYS FLUENT 2021 R2 are performed on three pin-fins configurations, i.e., MC-BW (pins mounted transversely to the bottom wall), MC-SW (pins mounted transversely to the side wall), and MC-Mixed (pins mounted transversely to the bottom and side wall). The thermal and flow characteristics are investigated using a laminar conjugate heat transfer model at Reynolds numbers 100–1000. Results show that introducing pin-fins significantly enhances heat dissipation as it continuously breaks the boundary layer and generates flow separation downstream of the pin-fins, which enhances fluid mixing and increases heat transfer augmentation inside MCHS. Among different configurations, the MC-Mixed gives the highest improvement of 50% in the convective heat transfer coefficient at Re = 1000. The highest thermal enhancement factor of η = 1.4 is obtained for the MC-Mixed configuration at Re = 600. For the base wall pin fin configuration RSM yields optimized values of 2.50 mm, 0.25 mm, and 0.045 mm for transverse pitch, longitudinal pitch, and diameter of pin respectively, and for the mixed pin fin configuration it gives 1.0 mm, 0.150 mm, 0.035 mm and 1.250 mm values for transverse pitch, longitudinal pitch, diameter of pin and pitch of side wall pins respectively for the maximum heat transfer and minimum pressure drop.

Wind shadowing of a sonic anemometer in low Reynolds number flows

Computational Fluid Dynamics (CFD) simulations have been carried out to better understand the wind shadowing effects on a sonic anemometer system. The anemometer will measure wind speed on the surface of Mars and the stratosphere of Earth.The wind velocity vector is measured through the difference in acoustic time of flight in 3 directions. However, the structure itself disrupts the flow and creates an internal wake. To understand this and generate correction factors, CFD simulations were run under Mars surface conditions while varying incident angle and flow speed. Spalart-Allmaras turbulence models were employed in both steady and unsteady Reynolds Averaged Navier Stokes (RANS) frameworks and compared to a laminar model. Due to the low Reynold’s number (<150) we observe no shedding at speeds below 10 m/s. At speeds below 10 cm/s the flow diverts around the structure and sensitivity drops. At intermediate speeds near 5 m/s the wind shadow ratio (WSR) varies substantially with incident wind angle. Design changes to the structure allowed us to improve the worst WSR from 38% to 47%. We were also able to quantify correction factors. Validating comparisons to water tunnel and wind tunnel measurements will be presented.

A CFD study on the start-up hydrodynamics of fluid catalytic cracking regenerator integrated with chemical looping combustion

ABSTRACT The integration of chemical looping combustion with fluid catalytic cracking (CLC-FCC) is an innovative concept that serves as a cost-effective method for CO2 capture in refineries. This approach has the potential to reduce refinery CO2 emissions by 25–35%, offering a promising solution. As in the conventional FCC unit, it is common for CLC-FCC regenerators to be exposed to an on-off process while they are being maintained and cleaned. The novelty of this research lies in its specific focus on a less-explored phase (start-up) of CLC-FCC regenerators, the application of advanced CFD modeling, and the comprehensive analysis of operational parameters that influence the system’s performance. To validate the CFD simulations of the different drag models for solid-gas granular, bed density profiles under steady-state conditions, collected from industrial processes, were used. For the flow period based on the start-up process of the drag models, the fluidization gas inlet geometry of the regenerator, flow regime (laminar and turbulent), and superficial gas velocity were comprehensively investigated to reveal their effects on hydrodynamic characteristics. The results show that Gidaspow and Syamlal-O’Brien drag models of the solid-gas multiphase granular flow exhibited a better fit with industrial data. The Syamlal-O’Brien and Gidaspow models closely align with industrial data under steady-state conditions, displaying similar bed densities in the dense phase region (230–310 kg/m3 for Syamlal-O’Brien and 235–300 kg/m3 for Gidaspow). During the initial stage (less than 0.2 seconds), both laminar and turbulent models yield comparable bed density profiles, approximately 510 kg/m3 in the dense phase. However, as the process progresses, the dense phase density decreases to about 250–350 kg/m3 at around 0.5 seconds, with laminar flow models showing a slightly better fit with industrial data. Notably, at 0.5 seconds of fluidization time, inlet geometries having better gas distribution achieve a highly diluted phase with bed densities of 10–20 kg/m3. Reaching a steady state, the bed density decreases from around 400 kg/m3 to 260–300 kg/m3, expanding into a higher section of the regenerator where it aligns well with industrial data. The increase in superficial gas velocity would result in the clarification of the difference and well mixing of the solid-gas multiphase flow.

Numerical study of microalgae cultivation process in a batch liquid foam-bed photobioreactor using CFD approach

Microalgae have different uses as feedstock of beneficial chemicals such as polysaccharides, carotenoids, and polyunsaturated fatty acids. Furthermore, they have been applied in the renewable energy, food, agriculture and feed industries, and in wastewater treatment. The growth and cultivation of microalgae are highly regarded by researchers worldwide. So, a variety of systems and designs have been used to cultivate microalgae. A research team recently proposed a new experimental design of photobioreactors based on a liquid foam flow at Wageningen University in the Netherlands. In this study, a numerical study of hydrodynamics and mass transfer of this novel system was conducted using computational fluid dynamics (CFD). This method is based on the simultaneous solution of transfer equations including hydrodynamic equations, mass transfer, cell growth, and radiation transport equation. The simulation was performed in an unsteady and three-dimensional state in COMSOL 5.5 software. The flow regime was considered laminar and mixture model and transport dilution species physics were used to model the behavior of two-phase fluid. Manual geometry grid generation was performed after defining the velocity and concentration boundaries. The number of optimal meshes was determined to be approximately 1.2 × 105 using the mesh independence test. The simulation results were validated according to the concentration-time curve. The cell density, 22 g l−1, is minimal in the center. The maximum biomass is 30.9 g l−1 at the bed wall after 80 h at 1446 μmol photon. m−2. s−1 light flux for the minimal cell density.

Mechanical and moisture-related properties of selected dried tempera paints

Mechanical properties—modulus of elasticity and strain at break, water vapour sorption, and hygroscopic expansion of selected egg tempera and distemper paints were determined as a function of relative humidity (RH) filling in this way a critical gap in the knowledge required for the analysis of fracturing processes in paintings. The experimental work was made possible by the preparation of several tempera paints, mimicking the historical materials, in the form of large specimens. Lead white, azurite, and yellow ochre were selected as pigments, and egg yolk and rabbit skin glue as binding media. The water vapour sorption and the moisture-related swelling of the paints were dominated by the proteinaceous components of the binders. The linear hygroscopic expansion coefficient of the dried egg yolk binder was approximately 1 × 10−4 per 1% RH, several times less than the coefficient of the collagen glue (4 × 10−4 per 1% RH). The moduli of elasticity of egg tempera paints at the RH mid-range were comparable to the moduli of aged oil paints, whilst the modulus of elasticity of the distemper paint was close to values measured for animal glue-based grounds. The paints experienced the transition from brittle to ductile states on increasing RH. The egg tempera paints were found to be more brittle than the distemper paint, gessoes, and, generally, aged oil paints. The observations modify a frequently used laminar model of panel paintings in which the mismatch in the response of glue-based ground layer and wood substrate to variations in RH has been identified as the worst-case condition for the fracturing of the entire pictorial layer. This study demonstrated that tempera could be more brittle than the ground layer and in consequence more vulnerable to cracking.

Conversion of a Small-Size Passenger Car to Hydrogen Fueling: 0D/1D Simulation of EGR and Related Flow Limitations

Hydrogen is seen as a prime choice for complete replacement of gasoline so as to achieve zero-emissions energy and mobility. Combining the use of this alternative fuel with a circular economy approach for giving new life to the existing fleet of passenger cars ensures further benefits in terms of cost competitiveness. Transforming spark ignition (SI) engines to H2 power requires relatively minor changes and limited added components. Within this framework, the conversion of a small-size passenger car to hydrogen fueling was evaluated based on 0D/1D simulation. One of the methods to improve efficiency is to apply exhaust gas recirculation (EGR), which also lowers NOx emissions. Therefore, the previous version of the quasi-dimensional model was modified to include EGR and its effects on combustion. A dedicated laminar flame speed model was implemented for the specific properties of hydrogen, and a purpose-built sub-routine was implemented to correctly model the effects of residual gas at the start of combustion. Simulations were performed in several operating points representative of urban and highway driving. One of the main conclusions was that high-pressure recirculation was severely limited by the minimum flow requirements of the compressor. Low-pressure EGR ensured wider applicability and significant improvement of efficiency, especially during partial-load operation specific to urban use. Another benefit of recirculation was that pressure rise rates were predicted to be more contained and closer to the values expected for gasoline fueling. This was possible due to the high tolerance of H2 to the presence of residual gas.

Multiphysics modelling of constant power microwave heating of model juice

Constant power microwave heating (CPMH) based on solid-state generators, a new microwave heating system, shows better repeatability than traditional microwave heating (TMH) powered by magnetron when performing experiments, while its detailed heating patterns and field distribution are still not fully understood. In this study, numerical simulations for model juice (about 1–5 mL) heated by CPMH and TMH systems were carried out to compare the heating performance. The simulation was performed through coupling electromagnetic, thermal and fluid fields, using a laminar flow model to simulate the flow behaviour of the model juice during the heating operation. Both surface temperature distributions and inner point temperatures were investigated for model validation, and the simulated data agreed well with the experimental ones, indicating that the modelling was rational and correct. Results showed that CPMH gave higher heating efficiency and better temperature uniformity, which was verified by determining both inner point temperature and surface temperature distribution. Besides, influences of sample volume and microwave input power on the heating performance of the CPMH system were studied, suggesting that greater sample volume could cause worse temperature uniformity, although a faster temperature increase was observed. When fixing total microwave input energy to 3 kJ, different input powers were found to achieve similar final average volumetric temperatures (50.46 °C–51.22 °C) but significantly different heating uniformity (final coefficient of temperature variance: 0.065–0.115), indicating that smaller microwave input power could contribute to better heating uniformity. It is hoped that this study could provide references to further understand the heating effects of CPMH systems, leading to better design and upgrade for microwave heating systems.

Determination method of Markstein number based on wavenumber measurement of cellular flames at the onset of parametric instability of downward propagating flames

This work proposes a new method to estimate the Markstein number by investigating the thermoacoustic parametric instability of laminar premixed flames propagating downwards in an open-closed tube. Methane-air flames were propagated in a combustion tube to capture the flame evolution in transition to parametric instability. By synchronized high-speed imaging filming both lateral and longitudinal views of flame propagation, cellular flame wavenumbers are measured from the clear transition of flat flames to cellular flames visualized in the present approach. The Markstein number is indirectly determined from wavenumber measurements at the onset of parametric instability by employing a laminar flame model under acoustic excitation treating the Markstein number as a free parameter. Acoustic velocity fluctuation amplitudes obtained from pressure fluctuation measurements were determined to further evaluate the validity of wavenumber-derived Markstein numbers. Markstein numbers obtained in the present work are compared with Markstein numbers relative to fresh gases in the literature from indirect and computational methods.

Numerical Simulation of Pyrethrin Aerosol Deposition

Highlights A steady state, laminar CFD model was developed to simulate the airflow inside an aerosol exposure chamber. The CFD model predicted the droplet tracks and deposition of various sizes of aerosol droplets. Larger aerosol droplets had higher deposition efficiency. A Higher flow rate, but still within the laminar flow regime, caused lower deposition efficiency for all droplet sizes. Abstract. Aerosol insecticides (e.g., pyrethrin) are widely used for the control of stored products insects inside food facilities. To optimize pyrethrin aerosol application, computational fluid dynamics (CFD) was used to predict airflow and aerosol transport inside a vertical flow aerosol exposure chamber operated under laminar flow conditions. A discrete phase model in ANSYS FLUENT 2021 R1 was developed, and simulations were conducted to track pyrethrin droplets of various diameters (0.1 to 20 µm) and determine their deposition onto Petri dishes located near the center of the chamber. The deposition efficiency of the different aerosol droplet sizes and the effect of two flow rates (5 × 10-4 m3 s-1 and 4 × 10-4 m3 s-1) on deposition efficiency were determined. The results showed that the predicted deposition of pyrethrin aerosol increased with increasing droplet size, largely due to inertial and gravitational effects. Deposition efficiencies decreased with the higher flow rate—with 0.1% to 96.6% predicted deposition efficiencies for the low flow rate and 0.1% to 93.8% for the high flow rate. Results of this study can be used to improve aerosol application methods for stored product insect control. Keywords: Aerosol deposition, Aerosol insecticide, Computational fluid dynamics, Confused flour beetle, Deposition efficiency, Discrete phase model, Numerical simulation, Particle tracking, Pyrethrins, Stored product insect.

Comparison of Particle Motion Deposition Analyses in “Left-Two-Right-Three” Bronchial Laminar and Turbulent Models of Human Lungs

Comparison of Particle Motion Deposition Analyses in “Left-Two-Right-Three” Bronchial Laminar and Turbulent Models of Human Lungs

Multi-Element Gaseous Methane–Oxygen Rocket Combustor Optimization for Modern Space-Flight Technology

In the realm of reusable rocket technology, the methane–oxygen propellant combination has gained prevalence in recent years. However, understanding of design parameters affecting the combustion performance of a methane–oxygen combustor is currently limited. The present study proposes a novel analytical and computational approach to design and optimize a combustor. The design of a seven-shear coaxial injector-based combustion chamber is optimized using an in-house developed code line with the aim of minimizing chamber length while preserving chamber performance. Numerical simulations are then carried out to ensure complete combustion within the chamber. Methane–oxygen reactions are modeled using laminar finite-rate and eddy dissipation concept models. An optimized design for the combustion chamber shows maximum characteristic velocity and optimal chamber length near the oxygen-to-fuel mass ratio of 2. The computational study shows that the eddy dissipation concept model can accurately capture the effect of turbulent mixing on gaseous methane–oxygen reactions. The eddy dissipation concept model yielded notable differences in flame characteristics compared to the laminar finite-rate model. The study indicates a need to optimize injector configuration. An optimized injector configuration is proposed by varying its geometric parameters, which exhibits substantial improvement in combustion performance compared to the initial configuration, utilizing practical recess, divergence, and an increased velocity ratio.

An experimental investigation on the settling of disk particles in annular region: Wall effect and drag coefficient

Settling non-spherical and spherical particles in the annular region is common in many industrial applications. This work shows the intensification of the performance of settling particles in an annular channel by reducing the drag coefficient. The disk/cylinder particles settle in annular channels filled with Newtonian and non-Newtonian fluids. An aqueous solution of different concentrations of glycerin and Carboxymethylcellulose (CMC) was considered as the Newtonian and non-Newtonian fluids. The experimental results reported in the present work covered the 0.17 ≤ blockage ratio ≤0.55, 0.14 ≤ k (flow consistency index) ≤1.81 (Pa.sn), 0.64 ≤ n (flow behavior index) ≤1, and annular channel Reynolds number 0.40 ≤ Re ≤63.44 and 0.05 ≤ Re ≤43.02 in Newtonian and non-Newtonian fluids respectively. The wall factor, f, was increased with the increase in Re and the decrease in blockage ratio. At higher Reynolds numbers (Re), the particle’s wall factor was only influenced by the blockage ratio. The wall factor was reduced due to the particle’s shape change from cylinder to disk, i.e., decreasing the particle’s sphericity. The wall factor of particles is observed to be higher in non-Newtonian than in Newtonian fluids. The critical Reynolds number (Rec ) decreased with the H/d (Height/diameter of disk) ratio and sphericity of the studied particles. Both the drag coefficients, in the absence ( C D ∞ ) and presence ( C D ) of the wall effect, declined with the Reynolds number. Suitable correlations were developed for CD with low values of RMSLD (root mean square logarithmic deviation). The experimentally obtained drag coefficient data were also analyzed successfully using the laminar model available in Ansys (Fluent) −18.1. The computed velocity contours analyzed the wall effect and CD variations successfully. The use of the annular channel as a drag reduction device is encouraged due to the observed higher wall factor and decreased drag coefficient for particle settling in comparison to the non-annular channel.

Simulation of hydrogen leakage diffusion behavior in confined space

In this paper, the diffusion characteristics and laws of hydrogen leakage in confined spaces are investigated using a combination of numerical simulations and experiments, and a small-scale cube model (dimensions: 0.47 m×0.33 m × 0.20 m) is used. The effects of leak source location, obstacles, leak hole size and shape on hydrogen diffusion and concentration evolution were investigated. The results show that the top funnel is sprayed vertically downward, the diffusion velocity decreases rapidly under the blocking effect of air and buoyancy force, and the momentum of the airflow is exchanged. During the injection phase, the leaking gas is mainly subjected to strong buoyancy forces and the hydrogen concentration shows a stratification effect. When the injection stops, the concentration difference decreases and eventually the hydrogen concentration reaches a steady state. The obstacle model in turbulence (4.3%) increases the concentration difference by a factor of about three compared to the empty room model (1.7%), which seriously affects the diffusive behavior of hydrogen. The obstacle in laminar flow model (10.4%) has almost the same concentration difference as the empty room model (10.2%). Rectangular leakage holes have a greater initial kinetic energy and diffuse more widely and faster.

Improved representation of laminar and turbulent sheet flow in subglacial drainage models

Abstract Subglacial hydrology models struggle to reproduce seasonal drainage patterns that are consistent with observed subglacial water pressures and surface velocities. We modify the standard sheet-flow parameterization within a coupled sheet–channel subglacial drainage model to smoothly transition between laminar and turbulent flow based on the locally computed Reynolds number in a physically consistent way (the ‘transition’ model). We compare the transition model to standard laminar and turbulent models to assess the role of the sheet-flow parameterization in reconciling observed and modelled water pressures under idealized and realistic forcing. Relative to the turbulent model, the laminar and transition models improve seasonal simulations by increasing winter water pressure and producing a more prominent late-summer water pressure minimum. In contrast to the laminar model, the transition model remains consistent with its own internal assumptions across all flow regimes. Based on the internal consistency of the transition model and its improved performance relative to the standard turbulent model, we recommend its use for transient simulations of subglacial drainage.