Direct Velocity Measurements Research Articles

Digital stability of the Furuta pendulum based on angle detection

The digital balancing of the Furuta pendulum is studied when the time delay related to the digital control and the dynamics of the actuator have essential effects on stability. Such cases occur when the sampling rate of the digital control is low, that is, the control cycles are slow due to complex signal processing strategies and/or the implementation of cheap low-capacity microprocessors. A corresponding difficulty is that no direct velocity measurement is available. Critical sampling times are identified and stability charts are constructed and validated by experiments including the possible existence of quasi-periodic self-excited oscillations.

DOPPLER OPTICAL PROBE FOR DROP SIZE, VELOCITY, AND FLUX MEASUREMENTS IN ASSISTED ATOMIZATION

For research as well as for process control, reliable drop size, velocity, and flux measurements are desirable in particular in dense, high-speed flows. A new optical probe has been recently manufactured by A2 Photonic Sensors company that combines an accurate phase detection capability (its latency length is small, about 6 µm) with the collection of a Doppler signal that provides the absolute velocity of an incoming gas-liquid interface. In this article, raw signals acquired over diverse flow conditions in terms of gas velocity and liquid concentration are analyzed. A dedicated signal processing routine is then proposed and optimized. The latter provides statistics on drop velocity and size. It also gives access to local liquid concentration and liquid flux. This Doppler probe combined with its processing has been tested in sprays produced from assisted atomization over a wide range of flow conditions. Transverse profiles of spray characteristics are presented for gas injection velocities ranging from 32 m/s to 283 m/s, for drops Sauter mean diameters D<sub>32</sub> varying from 37 µm to 275 µm, and for number densities-as estimated from liquid concentration and D<sub>32</sub>-comprised between 1 #/mm<sup>3</sup> and 218 #/mm<sup>3</sup>. The Doppler probe happens to be able to consistently detect chords as small as 4 µm, and to ensure a significant (up to 70%) fraction of direct velocity measurements. Besides, the injected liquid flow rate is recovered from the spatial integration of local liquid fluxes within 8% for gas velocities up to 50 m/s and within 17% for gas velocities above 90 m/s. Hence, the new Doppler probe combined with the proposed processing provides reliable statistics on drop velocity, size, and flux, and is a valuable tool for investigating dense, high-velocity, and fine sprays.

СЕЗОННАЯ ИЗМЕНЧИВОСТЬ ВОДООБМЕНА МЕЖДУ ТИХИМ И ИНДИЙСКИМ ОКЕАНАМИ ПО ДАННЫМ АРГО И ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Circulation associated with the Indonesian Troughflow (ITF) is studied using the Argo-based Model for Investigation of the Global Ocean (AMIGO). The model consists of a block for variational interpolation to a regular grid of Argo floats data and a block for model hydrodynamic adjustment of variationally interpolated fields. The seasonal and monthly mean temperature, salinity and velocity fields were calculate for the period of 2005–2014 using such an aproach. The mean ITF mass, heat, and salt transports over a period of 2005–2014 based on the AMIGO data is diagnosed as 15.2 ± 2.3 Sv. The maximum value of mass transport was diagnosed in August as 18.8 ± 1.4 Sv, the minimum value of 11.8 ± 2.1 Sv was found in January. The detailed analisys of seasonal variability of the mass transport through the Makassar Strait (Makassar throughflow or MT), the primary inflow path of Pacific water into the Indonesian Seas, were performed. The maximum and minimum values of MT were also diagnosed in August and January as 22.1 ± 1.2 Sv and 9.8 ± 2.1 Sv respectively. It was found significant changes in the MT sutface layer flow during boreal winter (with total reverse in January) associated with the intrusion of the low surface salinity waters of the Java and South China Seas. These modeling results agree very well with the direct velocity measurements.

Failure characteristics of reinforced concrete circular slabs subsequently subjected to fire exposure and static load: An experimental study

AbstractThis study investigated the effect of fire on the ultimate load‐bearing capacity of reinforced concrete (RC) slabs. The structural response of RC circular specimens subjected to static load conditions after exposure to a hydrocarbon fire on one side of the specimen was examined. Two fire exposure times were considered (60 and 120 min) in addition to reference non‐exposed specimens. The static response was evaluated in the damaged specimens in residual conditions after natural cooling from the elevated temperatures. The temperature distribution across the thickness of the slabs and their load–displacement response was measured. The decrease in the stiffness of the slabs due to the thermal exposure was studied by means of direct ultrasonic pulse velocity (UPV) measurements made before and after the fire tests. The decrease in global stiffness was partially accounted for by UPV measurements. The experimental results showed two peaks in the load‐deflection response of the slabs. The first peak was related to an arching mechanism introduced by the specific set‐up used. The second peak, corresponding to the ultimate load, occurred due to tensile membrane action at large deflections. While the former was strongly affected by the fire exposure, with the load being halved after the 120‐min exposure, the latter was not greatly affected by either the presence of fire or the exposure time. Simplified mechanical models were used to explain the behavior of the RC slabs during the tests.

Determination of River Hydromorphological Features in Low-Land Rivers from Aerial Imagery and Direct Measurements Using Machine Learning Algorithms

Hydromorphology of rivers assessed through direct measurements is a time-consuming and relatively expensive procedure. The rapid development of unmanned aerial vehicles and machine learning (ML) technologies enables the usage of aerial images to determine hydromorphological units (HMUs) automatically. The application of various direct and indirect data sources and their combinations for the determination of river HMUs from aerial images was the main aim of this research. Aerial images with and without the Sobel filter, a layer of boulders identified using Yolov5x6, and a layer of direct measurements of depth and streamflow velocity were used as data sources. Three ML models were constructed for the cases if one, two, or three data sources were used. The ML models for HMU segmentation were constructed of MobileNetV2 pre-trained on ImageNet data for the feature extraction part and U-net for the segmentation part. The stratified K-fold cross-validation with five folds was carried out to evaluate the performance of the model due to the limited dataset. The analysis of the ML results showed that the measured metrics of segmentation using direct measurements were close to the ones of the model trained only on the combination of boulder layer and aerial images with the Sobel filter. The obtained results demonstrated the potential of the applied approach for the determination of HMUs only from the aerial images, and provided a basis for further development to increase its accuracy.

Ship Berthing and Unberthing Monitoring System in the Ferry Terminal

This paper presents a monitoring system designed to increase the safety of the quay structure in ferry terminals, in which, during berthing and unberthing maneuvers, propeller and thruster-generated jets may damage the seabed protection, threatening the stability of the berth structure. Direct measurement of flow velocity on the seabed is not possible due to the possibility of its damage, therefore dynamic pressure measurement of the quay wall was used within the system. The relationship between the pressure on the quay wall and flow velocity on the seabed was determined using real-scale CFD simulation of the flow field generated during berthing and unberthing maneuvers. The paper focuses on the computations of the pressure distribution generated by bow thrusters. These computations made it possible to determine the velocity field in the time domain. Their results, verified using real-scale measurements, are in line with generally accepted empirical methods.

Estimating Sheet Flow Velocities Using Quinine as a Fluorescent Tracer: Bare, Mulched, Vegetated and Paved Surfaces

When direct flow velocity measurements are not feasible, the use of tracers can be a valuable tool. In the present study, both laboratory and field experiments were conducted to evaluate the applicability of quinine as a fluorescent tracer for estimating mean sheet flow velocities in different ambient light and surface morphology conditions. Quinine excels in low-light conditions when exposed to UVA light. This tracer was compared with dye and thermal tracers, all in liquid form. In these tracing techniques the tracers were injected into the flow, after which surface velocity was estimated by tracking the leading edge of the tracer plumes and applying a correction factor to calculate the mean velocity (in a water column). The visibility of the tracers was evaluated by measuring the relative luminance and contrast ratio of the quinine and dye tracer plumes. Results show that the quinine tracer can be used to estimate sheet flow velocities over a wide variety of soil and urban surfaces; it has better visibility in comparison to the dye tracer but, in some conditions, lower visibility than the thermal tracer. Although quinine is invisible under bright ambient light conditions, this tracer technique requires low-cost experimental setup and is useful in low-light conditions (e.g., night; twilight; shielded environments).

Fracture mechanics properties of fused silicas used for international space station windowpanes

AbstractThe fracture toughness and slow crack growth (SCG) parameters of a quartz‐based silica and a high‐purity fused silica were measured as part of a program to review the reliability of the International Space Station windows. The materials exhibit the same fracture toughness (.75 MPa m1/2 in N2) and very similar SCG parameters. The literature on fused silica indicates excellent agreement of fracture toughness, but a very wide range of SCG parameters, even from the same institution, with strength‐based methods usually yielding a lower power law exponent than direct crack velocity measurements. Use of the exponential function is shown to provide better agreement between test methods, with velocity curves derived from strength tests of bare fiber and polished or ground test specimens paralleling those from wide‐range, direct crack velocity observations, implying that constant stress rate tests can predict long lifetime via the exponential function. However, much variation still exists. SCG parameters for soda–lime silicate are much less sensitive to the test method than fused silica. Static load tests and stress intensity measurements resulted in a fatigue threshold of .3 MPa m1/2 for fused silica.

High-speed astigmatic dual-beam interferometric particle imaging for direct depth displacement and velocity measurement of metal droplet

High-speed astigmatic dual-beam interferometric particle imaging (HADIPI) is adopted to simultaneously measure the three-dimensional (3D) position, velocity and size of spherical metal droplets. We propose to infer the depth displacement of the droplet directly from the angle shift of the interference fringe. Angular cross power spectral density is used to detect the angular shifts of the interference fringe. The depth displacements and velocities can be further obtained from the obtained angular shifts. Proof-of-concept experiments are conducted on micron-sized gallium droplets, demonstrating that the 3D trajectories of the droplets can be accurately obtained, with depth displacement accuracy of tens of microns, improving accuracy in depth position measurement compared to the traditional Lagrangian framework. Different from traditional imaging methods, HADIPI can directly display the 3D movement of droplets, including in the depth direction. In the combustion measurements of the solid rocket motor, the motion state of metal droplets can be precisely determined, demonstrating the feasibility and practicality.

Predicting In-Situ Physical Properties for Gas Condensates From Fluid Pressure Gradients

New hybrid EOS-PVT models have been developed for estimating in-situ fluid properties for retrograde gas condensate fluids. The hybrid models are based on tuned equation of state (EOS) properties for a globally distributed set of quality-controlled (QC) pressure-volume-temperature (PVT) analyses of gas condensates in which the condensate-to-gas ratio (CGR) ranges from ~5 to 350 bbl/MMscf and for which in-situ fluid densities range from ~0.2 to 0.6 g/cm3. The hybrid EOS-PVT models are based on the observation that in-situ fluid densities derived from measured fluid pressure gradients (FPG) are highly correlated with EOS-derived in-situ fluid densities obtained from tuned EOS models and QC PVT data. Using fluid density values calculated using in-situ FPG data, it is now possible to estimate a variety of gas condensate fluid properties such as viscosity, mole fraction of methane (XCH4), density, acoustic velocity, and adiabatic fluid moduli, the latter being a critical input for Gassmann fluid substitution models. The utility of the new hybrid EOS-PVT models lies in their ability to facilitate rapid evaluation of stranded gas resources without having to take a fluid sample for laboratory PVT analysis. Properly executed FPG data also have great utility as a reliable QC for laboratory-measured PVT properties. We present hybrid EOS-PVT models for CGR, viscosity, in-situ fluid density, and acoustic velocity for a broad suite of gas condensates. A significant contribution of this work is the development of a new fluid acoustic properties model that enables estimation of the adiabatic fluid modulus (Kad) for retrograde gas condensates. Using predictive models reported here for fluid density [ρ] and velocity [Vp], the adiabatic fluid modulus is easily calculated. The model reported for fluid velocity was validated with direct measurements of fluid acoustic velocity on a live sample, at in-situ conditions, from the HP/HT Shearwater Field in the Central North Sea (CNS).

Characterization of Fine-Scale Turbulence Generated in a Laboratory Orbital Shaker and Its Influence on Skeletonema costatum

Turbulence is one of the ubiquitous aspects of aquatic systems and affects many physical and biological processes. Based on direct velocity measurements and a computational fluid dynamics (CFD) simulation, we characterized the distribution of the turbulent kinetic dissipations rates (ε) in an orbital shaker system within a range of rotation frequencies. CFD was able to estimate the ε distribution in containers accurately, which was confirmed by other two methods and was independent of velocity measurement. The results showed that ε was linearly correlated with the rotational frequencies. Despite the existence of gradients of ε and the fact that a mean circular horizontal flow was formed within the tank, the energy levels of the whole tank varied spatially within an order of magnitude and the ε distributions at different rotational frequencies were similar, suggesting that the ε distribution in the whole tank could be seen as quasi-homogeneous. To investigate the influence of turbulence on algae growth, culture experiments of a typical diatom—Skeletonema costatum were carried out under different turbulence conditions. Our results suggested turbulence mixing promoted nutrient uptake and growth of Skeletonema costatum, which could be attributed to the break of the diffusion-limited resource concentration boundary layer surrounding phytoplankton.

A novel objective function DYNO for automatic multivariable calibration of 3D lake models

Abstract. This study introduced a novel Dynamically Normalized Objective Function (DYNO) for multivariable (i.e., temperature and velocity) model calibration problems. DYNO combines the error metrics of multiple variables into a single objective function by dynamically normalizing each variable's error terms using information available during the search. DYNO is proposed to dynamically adjust the weight of the error of each variable hence balancing the calibration to each variable during optimization search. DYNO is applied to calibrate a tropical hydrodynamic model where temperature and velocity observation data are used for model calibration simultaneously. We also investigated the efficiency of DYNO by comparing the calibration results obtained with DYNO with the results obtained through calibrating to temperature only and with the results obtained through calibrating to velocity only. The results indicate that DYNO can balance the calibration in terms of water temperature and velocity and that calibrating to only one variable (e.g., temperature or velocity) cannot guarantee the goodness-of-fit of another variable (e.g., velocity or temperature) in our case. Our study implies that in practical application, for an accurate spatially distributed hydrodynamic quantification, including direct velocity measurements is likely to be more effective than using only temperature measurements for calibrating a 3D hydrodynamic model. Our example problems were computed with a parallel optimization method PODS, but DYNO can also be easily used in serial applications.

Isotope effect in turbulent transport in high density FT-2 tokamak discharges

A detailed study of the general transport properties of the FT-2 tokamak shows significant isotopic difference in ohmically heated quasi-stationary plasma in high density regimes 〈n e〉 ≈ (6–9) × 1019 m−3. For deuterium, the signatures of a transition to the H-mode are found at a plasma density exceeding a certain value, while hydrogen plasma remains in L-mode in all comparable discharge scenarios. The origin of this isotopic discrepancy is studied both with energy transport analysis and direct turbulence and plasma velocity measurements performed with Langmuir probes and microwave diagnostics. A special, more complicated dynamic experimental series with current ramp up, performed in these high density regimes, demonstrated the stability and robustness of an improved energy confinement in deuterium, whereas a comparable confinement improvement in hydrogen plasma was observed.

Seasonal circulation and volume transport of the Bransfield Current

We present the first observational-based assessment of the seasonal circulation and volume transport driven by the Bransfield Current (BC), a surface-intensified coastal jet which flows northeastward along the southern slope of the South Shetland Islands (SSI) in the Bransfield Strait (BS). To this aim, we construct a seasonal climatology based on an extensive dataset of direct velocity measurements which were routinely collected along ship tracks from 375 cruises between 1999 and 2014. A major finding is that the BC is a year-round feature of the circulation in the BS, flowing persistently towards the northeast along the southern slope of the SSI. Along its full path, core velocities of the BC deepen down to at least 200–250 m depth. Maximum velocities are found to reach 60 cm s−1 during summer, and 40 cm s−1 during autumn and spring. Available measurements confirm the BC also flows northeastward during wintertime, at least from Nelson Island to King George Island, with maximum core velocities about 40 cm s−1. The spatial variability along the SSI shelf suggests two distinct regions for the BC: a narrower jet of ∼20–30 km upstream of Nelson Strait, and a wider jet of ∼40 km downstream. Upstream of Nelson Strait, the BC transports about 0.93 ± 0.15 Sv in summer, 0.88 ± 0.19 Sv in autumn and 0.65 ± 0.13 Sv in spring. Available observations during winter lead to weaker transports about 0.50 ± 0.04 Sv from Greenwich Island to Nelson Strait. Downstream of Nelson Strait, volume transport estimates show no significant differences among seasons being on average 1.31 ± 0.20 Sv. As compared to upstream of Nelson Strait, the year-round average volume transport is weaker and about 0.74 ± 0.13 Sv. A mass balance analysis supports that this downstream increase in volume transport is likely due to a recurrent inflow passing through Nelson Strait and feeding the BC with source waters coming from the northern slope of the SSI. These results highlight that future observational efforts must focus on assessing the seasonal hydrography of the BC with mesoscale-solving measurements, especially when noting that the BC has been shown in the past to behave as a summertime buoyancy-driven coastal jet driving relatively warm and fresh Transitional Zonal Water with Bellingshausen influence (TBW), whose presence in the BS might be limited during winter.

Geostatistics of the Borden Aquifer: High‐Resolution Characterization Using Direct Groundwater Velocity Measurements

AbstractIn 1986, a seminal data set from the Canadian Forces Base (C.F.B.) Borden aquifer, Ontario, Canada, was published, illustrating, in unprecedented detail, the spatial distribution of hydraulic conductivity (K). Among many contributions attached to that data set was a geostatistical examination of field‐based data for comparison with theoretical predictions of macro‐dispersivity. However,that work treatedKas a static parameter and the sole source of flow variability. Here, point velocity probes (PVPs) are used to extend the earlier work by collecting a novel high‐resolution data set of groundwater velocity (v) measurements in the C.F.B. Borden aquifer. Velocity is a dynamic parameter of fundamental importance, closely tied to solute dispersion. Over 400 velocity measurements were collected along a transect perpendicular to flow, analyzed geostatistically, and compared with the analysis of the B‐B′ cross‐section ofKreported by Sudicky (1986),https://doi.org/10.1029/wr022i013p02069. The PVP measurements exhibited geostatistics similar to those previously estimated by Sudicky (1986),https://doi.org/10.1029/wr022i013p02069. This finding suggests, as implicitly assumed in the previous work, the distribution ofvis primarily controlled byK. PVPs also provided a novel, high‐resolution data set of groundwater flow directions. Since the ultimate objective of aquifer characterization includes the definition of velocity fields, this work not only extends the 1986 work, but also demonstrates a viable alternative for characterizing flow patterns in aquifers—with the advantage thatdirect vmeasurements reflect variability in porosity and hydraulic gradient, as well asK. This could ultimately be advantageous at sites with greater heterogeneity or other dynamic hydrogeological variabilities more pronounced than those at the Borden site.

Shoaling Wave Shape Estimates from Field Observations and Derived Bedload Sediment Rates

The shoaling transformation from generally linear deep-water waves to asymmetric shallow-water waves modifies wave shapes and causes near-bed orbital velocities to become asymmetrical, contributing to net sediment transport. In this work, we used two methods to estimate the asymmetric wave shape from data at three sites. The first method converted wave measurements made at the surface to idealized near-bottom wave-orbital velocities using a set of empirical equations: the “parameterized” waveforms. The second method involved direct measurements of velocities and pressure made near the seabed: the “direct” waveforms. Estimates from the two methods were well correlated at all three sites (Pearson’s correlation coefficient greater than 0.85). Both methods were used to drive bedload-transport calculations that accounted for asymmetric waves, and the results were compared with a traditional excess-stress formulation and field estimates of bedload transport derived from ripple migration rates based on sonar imagery. The cumulative bedload transport from the parameterized waveform was 25% greater than the direct waveform, mainly because the parameterized waveform did not account for negative skewness. Calculated transport rates were comparable to rates estimated from ripple migration except during the largest event, when calculated rates were as much as 100 times greater, which occurred during high period waves.

Transports and Pathways of the Tropical AMOC Return Flow From Argo Data and Shipboard Velocity Measurements

AbstractThe upper‐ocean circulation of the tropical Atlantic is a complex superposition of thermohaline and wind‐driven flow components. The resulting zonally and vertically integrated upper‐ocean meridional flow is referred to as the upper branch of the Atlantic Meridional Overturning Circulation (AMOC)—a major component and potential tipping element of the global climate system. Here, we investigate the tropical part of the northward AMOC branch, that is, the return flow covering the upper 1,200 m, based on Argo data and repeated shipboard velocity measurements. The western boundary mean circulation at 11°S is realistically reproduced from high‐resolution Argo data showing a remarkably good representation of the volume transport of the return flow water mass layers when compared to results from direct velocity measurements along a repeated ship section. The AMOC return flow through the inner tropics (11°S–10°N) is found to be associated with a diapycnal upwelling of lower central water into the thermocline layer of ∼2 Sv. This is less than half the magnitude of previous estimates, likely due to improved horizontal resolution. The total AMOC return flow at 11°S and 10°N is derived to be similar in strength with 16–17 Sv. At 11°S, northward transport is concentrated at the western boundary, where the AMOC return flow enters the inner tropics at all vertical levels above 1,200 m. At 10°N, northward transport is observed both at the western boundary and in the interior predominantly in the surface and intermediate layer indicating recirculation and transformation of thermocline and lower central water within the inner tropics.

Inner core composition paradox revealed by sound velocities of Fe and Fe-Si alloy

Knowledge of the sound velocity of core materials is essential to explain the observed anomalously low shear wave velocity (VS) and high Poisson’s ratio (σ) in the solid inner core. To date, neither VS nor σ of Fe and Fe-Si alloy have been measured under core conditions. Here, we present VS and σ derived from direct measurements of the compressional wave velocity, bulk sound velocity, and density of Fe and Fe-8.6 wt%Si up to ~230 GPa and ~5400 K. The new data show that neither the effect of temperature nor incorporation of Si would be sufficient to explain the observed low VS and high σ of the inner core. A possible solution would add carbon (C) into the solid inner core that could further decrease VS and increase σ. However, the physical property-based Fe-Si-C core models seemingly conflict with the partitioning behavior of Si and C between liquid and solid Fe.

Kinematic properties of white dwarfs

Context. Kinematic and chemical tagging of stellar populations have both revealed much information on the past and recent history of the Milky Way, including its formation history, merger events, and mixing of populations across the Galactic disk and halo. Aims. We present the first detailed 3D kinematic analysis of a sample of 3133 white dwarfs that used Gaia astrometry plus radial velocities, which were measured either by Gaia or by ground-based spectroscopic observations. The sample includes either isolated white dwarfs that have direct radial velocity measurements, or white dwarfs that belong to common proper motion pairs that contain nondegenerate companions with available radial velocities. A subset of common proper motion pairs also have metal abundances that have been measured by large-scale spectroscopic surveys or by our own follow-up observations. Methods. We used the white dwarfs as astrophysical clocks by determining their masses and total ages through interpolation with dedicated evolutionary models. We also used the nondegenerate companions in common proper motions to chemically tag the population. Combining accurate radial velocities with Gaia astrometry and proper motions, we derived the velocity components of our sample in the Galactic rest frame and their Galactic orbital parameters. Results. The sample is mostly located within ∼300 pc from the Sun. It predominantly contains (90–95%) thin-disk stars with almost circular Galactic orbits, while the remaining 5–10% of stars have more eccentric trajectories and belong to the thick disk. We identified seven isolated white dwarfs and two common proper motion pairs as halo members. We determined the age – velocity dispersion relation for the thin-disk members, which agrees with previous results that were achieved from different white dwarf samples without published radial velocities. The age – velocity dispersion relation shows signatures of dynamical heating and saturation after 4–6 Gyr. We observed a mild anticorrelation between [Fe/H] and the radial component of the average velocity dispersion, showing that dynamical mixing of populations takes place in the Galactic disk, as was detected through the analysis of other samples of FGK stars. Conclusions. We have shown that a white dwarf sample with accurate 3D kinematics and well-measured chemical compositions enables a wider understanding of their population in the solar neighborhood and its connection with the Galactic chemodynamics. The legacy of existing spectroscopic surveys will be boosted by the availability of upcoming larger samples of white dwarfs and common proper motion pairs with more uniform high-quality data.

CLOSURE LAW MODEL UNCERTAINTY QUANTIFICATION

The prediction uncertainty in simulators for industrial processes is due to uncertainties in the input variables and uncertainties in specification of the models, in particular the closure laws. In this work, the uncertainty in each closure law was modeled as a random variable and the parameters of its distribution were optimized to correctly quantify the uncertainty in predictions. We have developed two methods for optimization, based on the integrated quadratic distance and the energy score. The proposed methods were applied to the commercial multiphase flow simulator LedaFlow with the liquid volume fraction and pressure gradient as output variables. Two datasets were analyzed. Both describe two-phase gas-liquid flow, but are otherwise fundamentally different. One is gas-dominated stratified/annular flow and the other is liquid-dominated slug flow. The closure law for the gas-wall friction factor is decisive for the gas-dominated predictions, and the estimated relative standard deviation is 4.5% or 8.0% depending on method. The liquid-dominated study showed that the liquid-wall friction factor and the slug bubble velocity are the closure laws with the greatest impact. Moreover, the estimated relative standard deviation in the liquid-wall friction factor is 5%, and the deviation in the slug bubble velocity is 4%. We used direct measurements of the slug bubble velocity to validate the estimated uncertainty.