Local Mass Flow Research Articles

The Origin of Kinematically Persistent Planes of Satellites as Driven by the Early Evolution of the Cosmic Web in ΛCDM

Kinematically persistent planes (KPPs) of satellites are fixed sets of satellites co-orbiting around their host galaxy, whose orbital poles are conserved and clustered across long cosmic time intervals. They play the role of “skeletons,” ensuring the long-term durability of positional planes. We explore the physical processes behind their formation in terms of the dynamics of the local cosmic web (CW), characterized via the so-called Lagrangian volumes (LVs) built up around two zoom-in, cosmological hydro-simulations of Milky Way–mass disk galaxy + satellites systems, where three KPPs have been identified. By analyzing the LV deformations in terms of the reduced tensor of inertia (TOI), we find an outstanding alignment between the LV principal directions and the KPP satellites’ orbital poles. The most compressive local mass flows (along the eˆ3 eigenvector) are strong at early times, feeding the so-called eˆ3 -structure, while the smallest TOI axis rapidly decreases. The eˆ3 -structure collapse marks the end of this regime and is the timescale for the establishment of satellite orbital pole clustering when the Universe is ≲4 Gyr old. KPP protosatellites aligned with eˆ3 are those whose orbital poles are either aligned from early times or have been successfully bent at eˆ3 -structure collapse. KPP satellites associated with eˆ1 tend to have early trajectories already parallel to eˆ3 . We show that KPPs can arise as a result of the ΛCDM-predicted large-scale dynamics acting on particular sets of protosatellites, the same dynamics that shape the local CW environment.

A homogeneous relaxation model algorithm in density-based formulation with novel tabulated method for the modeling of CO2 flashing nozzles

Accurate prediction of the flow physics within nozzles and ejectors working with two-phase carbon dioxide remains particularly challenging. Indeed, the flashing phenomenon in the device often comes along with the formation of the metastable phase, which can severely affect both the flow physics, and the flow rate. Due to the particular challenges associated with building and operating two-phase carbon dioxide experimental setups, computational fluid dynamics constitutes a compelling alternative to study and predict nozzle and ejector flows. In this work, the metastability effects are modeled through a Homogeneous Relaxation Model for the first time expressed in density-based formulation, within the SU2 solver. The thermodynamic relations for the equation of state are tabulated using a novel quad-tree algorithm and directly coupled to the solver, ensuring fast and accurate predictions. The simulation tool is then validated against experimental nozzle pressure profiles and used to compare the commonly used Homogeneous Equilibrium Model to the Homogeneous Relaxation Model in terms of local flow topology and mass flow rates. Most notably, it was found that the Homogeneous Relaxation Model was able to better fit the experimental pressure profiles within the first part of the expansion.

The impact of second-harmonic tip clearance distributions caused by casing Ovalization and blade height variation in a large-scale compressor stage

Affected by extreme operating conditions, external loading and casing stiffness, the casing ovalization will potentially occur for the axial compressor, resulting in a second harmonic distribution of rotor tip clearances over the full annulus. The same clearance layout can be reproduced by varying the blade height over the circumference with a circular casing. In this paper, both of these non-axisymmetric configurations are respectively modelled with full-annulus simulations in the first 1.5 stage of the large-scale research compressor at Shanghai Jiao Tong University (SJTU-LSRC), with the blade adjustment item further complemented by experimental measurements.The impacts are evaluated and compared in terms of compressor performance and flow mechanisms. Ovacasing case leads to a 32.57 % stall margin (SM) benefit compared to the prototype, while ovablade experiences a 31.75 % SM extension. Both configurations cause a 4 % efficiency decrease at the design conditions. The second-harmonic clearance distribution results in a 15 lag in ovablade and a 30 lag in ovacasing for the total pressure ratio at the rotor exit, due to local mass flow adaptation related to circumferential tip clearances. Ovacasing configuration exhibits substantial reverse flow and a low-velocity region in the tip of large clearance sector, while ovablade shows reduced reverse flow and secondary leakage flow. This underscores the impact of blade tip relationships and height differences from adjacent rotors on leakage flow and its secondary behavior, even with identical clearances. There exists a critical clearance (2.57 % span), below which adjusting blade heights effectively simulates the performance impact and flow field redistribution caused by casing ovalization and rotor eccentricity.

Local mass transfer and flow visualization around a cylinder in a liquid-solid fluidized bed

Adsorption method has been used for flow visualisation and determination of the local and average mass transfer coefficients around a horizontal cylinder in a liquid-solid fluidized bed. The obtained concentration fields on the adsorbent (silica-foils) represent a clear qualitative flow pattern around the cylinder. By comparison of the concentration fields around the cylinder in the single-phase flow and in the fluidized bed, a significant disturbance of the boundary layer by fluidized particles can be observed. Local mass transfer coefficients were shown to be dependent on the angular position around the cylinder with the maximum determined at the angle 140? (measured from the stagnant point 0?). Selected correlations were applied to predict the average mass transfer coefficients and the two best have shown deviations from the experimental data up to 5 %.

Spherical Diffusion Flames of Ethylene in Microgravity: Multidimensional Effects

The joint American–Russian Space Experiment Flame Design (Adamant) was implemented on the International Space Station (ISS) in the period from 2019 to 2022. The objectives of the experiment were to study the radiative extinction of spherical diffusion flames (SDF) around a porous burner (PB) under microgravity conditions, as well as the mechanisms of control of soot formation in the SDF. The objects of the study were the normal and inverse SDFs of gaseous ethylene in an oxygen atmosphere with nitrogen dilution at room temperature and pressures ranging from 0.5 to 2 atm. The paper presents the results of transient 1D and 2D calculations of 24 normal and 13 inverse SDFs with and without radiative extinction. The 1D calculations revealed some generalities in the evolution of SDFs with different values of the stoichiometric mixture fraction. The unambiguous dependences of the ratio of flame radius to fluid mass flow rate through the PB on the stoichiometric mixture fraction were shown to exist for normal and inverse SDFs. These dependences allowed important conclusions to be made on the comparative flame growth rates, flame lifetime, and flame radius at extinction for normal and inverse SDFs. The 2D calculations were performed for a better understanding of the various observed non-1D effects like flame asymmetry with respect to the center of the PB, flame quenching near the gas supply tube, asymmetrical flame luminosity, etc. The local mass flow rate of fluid through the PB was shown to be nonuniform with the maximum flow rate attained in the PB hemisphere with the attached fluid supply tube, which could be a reason for the flame asymmetry observed in the space experiment. The evolution of 2D ethylene SDFs at zero gravity was shown to be oscillatory with slow alterations in flame shape and temperature caused by the incepience of torroidal vortices in the surrounding gas. Introduction of the directional microgravity, on the level of 0.01g , led to the complete suppression of flame oscillations.

Effects of Local Mixing Ratios and Mass Flow Rates on Combustion Performance of the Fuel-Rich LOX (Liquid Oxygen)/kerosene Gas Generator in the ATR (Air Turbo Rocket) Engine

This paper presents a numerical simulation analysis of the flow and combustion characteristics of a fuel-rich LOX (liquid oxygen)/kerosene gas generator in an ATR (air turbo rocket) engine, examining the effects of local parameters on the combustion flow field and performance. The analysis considers variations in unit injector mixing ratios and unit mass flow rates. The results indicate that as the mixing ratio in the inner-ring injectors increases (while the mixing ratio in the middle-ring injectors decreases), the oxygen concentration area near the axis zone and the 50% radius zone of the gas generator expands. Conversely, the kerosene concentration area near the axis zone decreases while gradually increasing near the 50% radius zone. In the flow direction section, there is an inverse relationship between the variation trend of local temperature and the oxygen concentration in the local area. As the oxygen concentration increases, the temperature decreases. The temperature distribution across the cross-section of the gas generator exhibits a circular pattern. When the mixing ratio (or mass flow rates) of the unit injector are perfectly balanced, the temperature distribution becomes highly uniform. A larger disparity in flow rate between the inner ring injector and the middle ring injector leads to a lower combustion efficiency. This effect differs from the effect of the mixing ratio difference between the two injector rings. Increasing the mixing ratio in the inner-ring injectors (or decreasing the mixing ratio in the middle-ring injectors) initially leads to a rise in combustion efficiency, followed by a subsequent decline. The maximum combustion efficiency of 89.10% is achieved when the mixing ratio is set to Km-1 = 0.7 and Km-2 = 2.79, respectively. Increasing the flow rate in the inner-ring injectors (or decreasing the flow rate in the middle-ring injectors) initially leads to an improvement in combustion efficiency, followed by a subsequent reduction. The maximum combustion efficiency of 86.13% is achieved when the mass flow rate is set to m-1 = m-2 = 0.1 kg/s.

Transport of chemical species alongside magnetic pseudoplastic nanomaterial through a porous surface

Pseudoplastic fluids are non-Newtonian fluids with intriguing uses in current research and industry. Among many other extant models, the Sutterby fluid model is an essential viscoelastic fluid model that demonstrates shear thinning and shear thickening properties in high polymer aqueous solutions by manifesting viscous and elastic aspects during deformation. The magneto hydrodynamic effects of Sutterby nanofluid on porous elastic surfaces in the presence of chemical processes are examined in this theoretical study. By using similarity transformation, the mathematical model of a governed problem is converted into a collection of differential equations. A shooting strategy is used to solve these nonlinear coupled ordinary differential equations. The velocities, temperatures, and chemical species concentrations of fluids are graphically shown. Physical quantities of importance, such as local heat and mass flow, are visually represented using bar charts. Heat and mass transport, as well as chemical species concentration, decrease with Hartman number in both suction and injection. Chemical concentration of governed fluid rises for homogeneous reactions but drops for heterogeneous reactions. Temperature and concentration of fluid increases for thermophoresis parameter but decreases for Brownian motion parameter, also the effects of injection are much stronger and higher than suction.

Study on the effect of rotor tip fillet edge in axial compressor

The compressor flowfield is sensitive to the small geometry in the tip region. The blade tip edge, which was usually idealized as “sharp” edge in the numerical simulation, had been actually filleted during the process of machining, coating, and wearing. However, the fillet edge was completely neglected in the compressor performance estimation. Thus, in this paper, the effect of the fillet edge is evaluated by establishing several models with tip fillet edges as well as tip sharp edge in a transonic axial compressor. By the comparison of the flowfield between models with fillet edge and sharp edge, it was found that the tip fillet edge can eliminate the separation bubble at the pressure side of the tip clearance. Also, it can affect the tip clearance outflow by changing the reversed flow. As a result, the leakage flow is increased and the compressor performance is decreased in efficiency and pressure ratio. The local leakage mass flow rate along the camber line can be increased up to 40% when the fillet radius is as much as 20% of the tip clearance size. The flowfield in the downstream is also affected by the fillet edge. By the comparing among the models with different working conditions, it is found that the sensitivity of the performance to the fillet edge is different between design and off-design conditions. Furthermore, the effect of the tip fillet edge on the leakage flow is qualified and compared with the effect of the tip clearance.

Characterization of dissolved organic matter at urban and industrial rainwater of Bangladesh by fluorescence spectroscopy and EEM-PARAFAC modeling

Fluorescent dissolved organic matter (fDOM) was characterized seasonally in urban and industrial rainwater in one of the most polluted countries in the world, Bangladesh, using excitation-emission matrix (EEM) fluorescence spectroscopy and Parallel factor analysis (PARAFAC). EEM and PARAFAC modeling enabled identification of six fluorophores (peaks: A, C, M, T, Tuv, Wuv) and five fDOM components (humic-like, protein-like, fulvic acid (C)-like, humic (M)-like, and detergent-like), in both urban and industrial rain. The concentration of dissolved organic carbon (DOC) varied between 0.2–37.9 mg/L and 0.3–39.4 mg/L in urban and industrial rainwater, respectively. DOC concentration and fDOM component intensity were higher in the dry than in the wet season. DOC concentration was higher in urban than industrial rain in maximum months of the year. However, the higher intensity of fDOM components in industrial rainwater than in urban indicated that the industrial atmosphere might contain more nitrogenous organic compounds besides carbonaceous. The anthropogenic detergent-like component was present throughout the year with high intensity both at urban and industrial rain. fDOM indices and principal component analysis (PCA) described that organic components were not fresh, and originated from both allochthonous and autochthonous sources, and affected by microbial decomposition. fDOM components had strong positive correlations with gases (SO2, NOX, CO, and O3) and particulate matters (PM2.5 and PM10), indicating that they originated from similar local and distant sources. The Hybrid Single-Particle Lagrangian Integrated (HYSPLIT) back trajectory model described the local and distant air mass flow direction around sampling stations and interpreted their role in fDOM intensity fluctuations.

Near Tip Loss Control With a Winglet Baffle Cavity Tip in a Turbine Cascade

Abstract The aerodynamic performance of a winglet baffle cavity tip is investigated at different inlet incidences from −12.5 to +12.5 deg. This blade tip shows a geometry feature with a pressure side winglet and a baffle within the tip cavity. The experimental studies were carried out in a large-scale linear cascade. Numerical methods were also used to obtain the detail flow physics. The baffle on the tip divides the cavity vortex into two main parts, and enhances flow mixing over the tip. As the tip leakage flow exits the tip near the baffle and the cavity corner, flow separation occurs over the suction side and its blockage effect reduces the local tip leakage mass flow rate. The additional pressure side winglet reduces the contraction coefficient on the pressure side squealer. Compared with the squealer tip, the winglet baffle cavity tip reduces the tip leakage mass flow by 12.1% and the near tip loss by 4.2%. Removing the baffle on the tip also results in an increase of the loss. As the incidence of the incoming flow decreases, the loss near the tip reduces mainly due to a reduction of the strength of the passage vortex, which develops from the casing endwall. At all incidences studied, the winglet baffle cavity tip shows better aerodynamic performance than the squealer tip.

Granular flow behavior in a conveyor system: From local velocity profiles to mass flow rates

Predictability of consistent granular flow is critical in many industries. This exploration of behavior in a conveyor apparatus aims to fill a gap in knowledge of achieving a uniform mass flow rate by correlating local velocity profile data with summative mass measurements in both experiments and simulations. Differences between the two types of flow measurements indicate unwanted energy dissipation. In experiments, image data was collected for uniformly-sized particles in the bottom-driven flow conveyor belt system for which edge velocity profiles could be produced to measure local shear rates and estimate mass flow. These velocity relationships under different speeds of the belt and varied outlet sizes are compared to shear rates from gravity driven flow. Similarity in the linear profile transitioning to an exponential decay are observed but at shear rates substantially lower than dilated, free-surface flows. Simulations were conducted using LIGGGHTS discrete element model framework using the same dimensions for the conveyor system and particle sizes. Results show unique three-dimensional velocity profiles can produce similar mass flow rate behavior. The work continues to demonstrate computational models of granular flows with experimental validations can be used to evaluate customized designs in industrial applications, such as feeding unsteady biomass conversion reactors. Future work can be developed to evaluate granular materials that have random distribution of sizes, aspect ratios, and orientation.

A microchannel shell-and-tube absorber for ammonia-water absorption

A shell-and-tube absorber with microscale geometric features that yields significant volumetric heat duties is investigated. A vertically-oriented baffled shell-and-tube heat exchanger with a tightly packed tube bundle is designed to serve as the absorber for a 10.5 kW nominal cooling capacity absorption chiller. The heat and mass transfer in this absorber is investigated experimentally at operating conditions spanning a wide range of working fluid and coupling fluid flow rates and ambient temperatures. An experimental facility is fabricated to closely simulate the operating conditions in an absorption refrigeration system. Absorption heat duties in the range of 5–15 kW are measured. In addition to operating the absorber in the baseline co-current flow configuration with premixed inlet, fluid ports are provided to enable operation in counter-current flow, where the dilute solution enters from the top and vapor enters from the bottom. The performance of these two flow configurations is compared. A preliminary heat and mass transfer model is developed to quantify the local temperatures, concentrations, and mass flow rates of the solution and vapor streams along the length of the absorber. The model predictions for total heat duty agree with the experimental results within 10% for almost all the data points, with an AAD of ~ 3.4%. The results of this study, along with the modeling framework, can guide further development of highly compact and efficient absorbers absorption systems.

Experimental investigations of local friction factors of laminar and turbulent gas flows in smooth micro-tubes

Local friction factors of laminar and turbulent gas flows including choked flows through micro-tubes were experimentally investigated under atmospheric back pressure and variable inlet pressure. The experiments were carried out using two glass micro-tubes with D = 265.7 and 399.9 μm and a fused silica micro-tube with D = 531.2 μm. Two to three pressure tap holes were drilled into the micro-tube wall at intervals of 5 ~ 6 mm to measure local pressures. The local Mach numbers, temperatures and friction factors were obtained by using stagnation temperatures and pressures, local pressures and mass flow rates. The results for wide range of Reynolds numbers and Mach numbers were obtained including choked flows. Both the local Fanning and the local Darcy friction factors were obtained under the assumption of both Fanno flow (adiabatic wall) and isothermal flow, respectively. Since the measured values of the inner relative surface roughness of the micro-tubes were less than 0.02 %, only the effect of compressibility on friction factors was assessed. The difference between Fanning and Darcy friction factors was described and compared with the ff and fd correlation as a function of Mach number. The friction factor difference obtained under the assumption of Fanno and isothermal flows was also compared with the available literature and numerical results. In the turbulent flow region including the choked flow, the local Fanning friction factors under the assumption of Fanno flow nearly coincided with Blasius correlation.

Thermal counterflow and electrical activity of superfluid systems in a magnetic field

The thermal counterflow in superfluid helium placed in a magnetic field is shown to lead to the emergence of an electric field in the surrounding space. This effect is caused by the counterflow nature of thermal conductivity in superfluid systems: heat transfer in such systems is associated with the motion of the normal component, while the average mass flow transported by the normal component is compensated by the mass flow carried by the superfluid component. The local mass flow is nonzero. The effect occurs in case of stationary and non-stationary (second-sound) heat flows. The features of the effect for a number of samples with various geometries are considered. It was established that the magnitude of the arising electric field substantially depends on the shape of the sample containing helium and the direction of the magnetic field.

Application of the Transient Heat Transfer Measurement Technique Using Thermochromic Liquid Crystals in a Network Configuration With Intersecting Circular Passages

The present study deals with the application of the transient thermochromic liquid crystal (TLC) technique in a flow network of intersecting circular passages as a potential internal turbine component cooling geometry. The investigated network consists of six circular passages with a diameter d = 20 mm that intersect coplanar at an angle θ = 40 deg, the innermost in three, the outermost in one intersection level. Two additional nonintersecting passages serve as references. Such a flow network entails specific characteristics associated with the transient TLC method that have to be accounted for in the evaluation process: the strongly curved surfaces, the mixing and mass flow redistribution at each intersection point, and the resulting gradients between the wall and passage centerline temperatures. All this impedes the choice of a representative fluid reference temperature, which results in deviations using established evaluation methods. An alternative evaluation approach is introduced, which is supported by computational results obtained from steady-state three-dimensional (3D) Reynolds-averaged Navier–Stokes equations (RANS) simulations using the shear-stress transport (SST) turbulence model. The presented analysis uncouples local heat transfer (HT) coefficients from actually measured local temperatures but uses the time information of the thermocouples (TC) instead that represents the fluid temperature step change and evolution along the passages. This experimental time information is transferred to the steady-state numerical bulk temperatures, which are finally used as local references to evaluate the transient TLC experiments. As effective local mass flow rates in the passage sections are considered, the approach eventually allows for a conclusion whether HT is locally enhanced due to higher mass flow rates or the intersection effects.

Linking lava flow morphology, water availability and rootless cone formation on the Younger Laxá Lava, NE Iceland

It is well established that rootless cones and associated deposits are the result of explosive interactions between lava flows and environmental water, but there is substantial uncertainty about the dynamics of rootless eruptions, particularly the relative importance of lava supply, water availability and the conditions under which they meet. Here we present a case study of the Younger Laxá Lava in NE Iceland, and the >6500 rootless cones that it created. Critically, this long (63 km) lava flow interacted with water along its length, from flow through/around a large lake (Mývatn), down a narrow river gorge (Laxárdalur) and across a broad glacial valley with wetlands and rivers (Aðaldalur). Using high-resolution digital terrain models and aerial photographs, we map the flow surface morphology, and classify, measure and analyse the rootless cone type, size and spatial distribution in the context of both lava and water availability. We find that rootless cone size is controlled by the combined availability of lava and water: large rootless cones require sustained, high volumes of lava (related to proximity to vent) and water (e.g., Lake Mývatn), whereas limited supplies of lava (with distance from the vent and from the centre of the flow) and water (particularly in dammed river valleys) build smaller cones. Where we infer that where water was distributed in sediment, the lava–water interaction style changed to low-energy and distributed bubble bursts that created >3000 hornitos in the lower reaches of Aðaldalur. The distribution of rootless cones around Mývatn also defines the pre-eruption extent of the lake and suggests substantial lake level changes during the course of the eruption. By looking at the variation in rootless cone type and size in the context of the parent lava flow and the local environment, we explain how the availability of water and local mass flow rate of lava affect the dynamics of rootless eruptions.

Estimation of the solid circulation rate in circulating fluidized bed systems

The results of experiments performed in four different fluidized bed units (two pilot plants and two cold flow models, with a wide range of operating conditions) together with correlations from literature are used to establish methods to estimate the solid circulation rate in a circulating fluidized bed system. The estimation is based on the measured pressure drop in the upper part of the riser as well as particle properties and geometry of the riser exit. Investigations included smooth as well as abrupt riser exit configurations.In case of a smooth riser exit geometry (direct gas solids separation exit), the assumption of a uniformly upflow of solids in the riser is sufficient for the estimation of the solid circulation rate. Further, for an abrupt exit (L-shape exit), two methods were developed. Both methods are based on the assumption that the rate of reflected particles at the top of the riser increases with the so-called exit Froude number. One method is based on a correlation between interstitial gas velocity in the riser, slip velocity, mean particle velocity in the riser, and exit Froude number where it was possible to keep the difference between measured and estimated solid circulation rate in the range of approximately +75% and −40%. Further, this method is not able to consider the local mass flow distribution in the riser. For the other method, the output of a detailed mathematical model, based on information from literature, was used to establish a correlation between, exit Froude number, exit reflecting coefficient and local mass flow to estimate the solid circulation rate. Using this method it was possible to keep the difference between measured and estimated solid circulation rate in the range of ±40%. For both methods, the accuracy of the measurement of the pressure drop in the upper part of the riser is a significant parameter for the prediction of the solid circulation rate.

CFD prediction of critical heat flux in vertical heated tubes with uniform and non-uniform heat flux

In this paper, Eulerian Two-fluid model coupled with extended wall boiling model was used to simulate the departure from nucleate boiling (DNB) in vertical heated tubes under high pressures by using STAR-CCM+ 10.04. Based on CFD approach, new methods were developed to predict the critical heat flux (CHF) in both uniform and non-uniform heated tubes. The results showed some differences between the uniform and non-uniform heated cases. The transition in boiling curves was used as the criterion of DNB for uniform heat flux while the peaks of wall temperature and near wall void fraction were used for non-uniform cases. Good agreement was obtained between the predictions and experimental data, including both the values of critical heat flux and their locations. For uniform heat flux, sensitivity analysis for pressure, local quality and mass flow rate were performed, and the results showed that the new prediction method could work well under a wide range of conditions except under the high local quality and low mass flow rate conditions. The mechanism of this prediction method was discussed as well.

Rarefaction cloaking: Influence of the fractal rough surface in gas slider bearings

For ultra-thin gas lubrication, the surface-to-volume ratio increases dramatically when the flow geometry is scaled down to the micro/nano-meter scale, where surface roughness, albeit small, may play an important role in gas slider bearings. However, the effect of surface roughness on the pressure and load capacity (force) in gas slider bearings has been overlooked. In this paper, on the basis of the generalized Reynolds equation, we investigate the behavior of a gas slider bearing, where the roughness of the slider surface is characterized by the Weierstrass-Mandelbrot fractal function, and the mass flow rates of Couette and Poiseuille flows are obtained by deterministic solutions to the linearized Bhatnager-Gross-Krook equation. Our results show that the surface roughness reduces the local mass flow rate as compared to the smooth channel, but the amount of reduction varies for Couette and Poiseuille flows of different Knudsen numbers. As a consequence, the pressure rise and load capacity in the rough bearing become larger than the ones in the smooth bearing in the slip and early transition flow regimes, e.g., a 6% roughness could lead to an increase of 20% more bearing load capacity. However, this situation is reversed in the free-molecular flow regime, as the ratio of the mass flow rates between Couette and Poiseuille flows is smaller than that in the smooth channel. Interestingly, between the two extremes, we have found a novel “rarefaction cloaking” effect, where the load capacity of a rough bearing equals to that of a smooth bearing at a certain range of Knudsen numbers, as if the roughness does not exist.

Direct numerical simulation of the flow in the intake pipe of an internal combustion engine

The incompressible flow in the intake pipe of a laboratory-scale internal combustion engine at Reynolds numbers corresponding to realistic operating conditions was studied with the help of direct numerical simulations. The mass flow through the curved pipe remained constant and the valve was held fixed at its halfway-open position, as is typically done in steady flow engine test bench experiments for the optimization of the intake manifold. The flow features were identified as the flow evolves in the curved intake pipe and interacts with the cylindrical valve stem. The sensitivity of the flow development on the velocity profile imposed at the inflow boundary was assessed. It was found that the flow can become turbulent very quickly depending on the inflow profile imposed at the pipe inlet, even though no additional noise was added to mimic turbulent velocity fluctuations. The transition to turbulence results from competing and interacting instability mechanisms both at the inner curved part of the intake pipe and at the valve stem wake. Azimuthal variations in the local mass flow exiting the intake pipe were identified, in agreement with previously reported measurement results, which are known to play an important role in the charging motion inside the cylinder of an internal combustion engine.