Typical Flow Structures Research Articles

Research on velocity measurements of the hypersonic turbulent boundary layer based on the nano-tracer-based planar laser scattering technique

As one of the most typical flow structures in hypersonic flow, the hypersonic turbulent boundary layer (TBL) is of great significance in the optimization of the aerodynamic configuration design of hypersonic vehicles. The nano-tracer-based planar laser scattering technique was utilized to obtain velocity results of the fully developed hypersonic (Mach 6.0) TBL. The scale-invariant feature transformation algorithm was used to obtain velocity information. Based on the results of mean velocity and fluctuating velocity distribution, the feasibility of this method has been verified.

The near wake of three circular cylinders in an equilateral triangular arrangement at a low Reynolds number Re=100

Two-dimensional numerical simulations are conducted at a low Reynolds number Re = 100 to investigate the near wake of three identical circular cylinders that are arranged in an equilateral triangular configuration. The incident angle of the three-cylinder configuration with respect to incoming flow is varied from θ= 0° to 60°, while the spacing between adjacent cylinders (L) covers a wide range of L/D = 1.25-7.0, where D is diameter of the cylinder. Typical flow structures in the near wake of the three-cylinder configuration are identified, including a single Karman vortex street, bistable flip-flopping near wake, anti-phase and/or in-phase vortex shedding, shear layer reattachment, and vortex impingement, depending on the configuration (L/D, θ). The behavior of Strouhal number (St) is discussed in detail, echoing the distinct structures of near wake. Furthermore, fluid forces on the individual cylinders are examined, which, though highly depending on (L/D, θ), exhibit a close correlation to the near wake behavior.

Investigation of flow structure and heat transfer enhancement in rectangular channels with dimples and protrusions using large eddy simulation

Large-eddy simulations are used to investigate flow structures and heat-transfer enhancements in rectangular channels with dimples and protrusions as Reynolds number varies from 5600 to 22,000. Roughness elements adopt sharp edges and are arranged inline, the ratios of their depths or heights to their respective print diameters are 0.1, and the ratio of channel height to dimple print diameter is 1.0. Comparisons are carried out between effects of Reynolds number and the gap between roughness elements, and the data presented include thermal performances, flow structures, local Nusselt numbers, local spatial correlation coefficients, characteristic frequencies, and turbulent kinetic energy. Results show that thermal performances can be increased considerably by either increasing Reynolds number or decreasing the gap ratio, but the type of flow structure is only related to Reynolds number. And inline arrangements for dimples and protrusions in many ways are equivalent to deepening the depth of the dimple, especially along the centerline of the arrangement, such that they can achieve higher thermal performances than a denser arrangement of dimples with a corresponding depth ratio. Meanwhile, sampling grids are deployed in the spacings between roughness elements to obtain local spatial correlation coefficients and characteristic frequencies. Frequent passing of vortical structures from roughness elements results in local minima of spatial correlation coefficients and protruding characteristic frequencies, and results show that contours of peak Nusselt numbers are in good correlation with them and thus directly resulting from these vortical structures and their enhancing effects. And it is found that the asymmetry in Nusselt number contours in the wake of the dimple is resulted from the combined influences of sizes of primary passages for vortical structures from dimples, shedding frequencies, and the turbulent kinetic energy carried by these vortical structures.

Experimental Investigation of the Flow Mechanisms and the Performance Change of a Highly Loaded Axial Compressor Stage with/without Stator Hub Clearance

Three-dimensional corner separation is common in axial compressors, which can lead to large flow loss and blockage especially when it evolves into the corner stall (open separation). In this paper, the evolution of the three-dimensional flow structures inside a cantilevered stator of a 1.5 stage low-speed highly loaded axial compressor as the stator hub clearance varies, and its effect on the whole compressor performance are investigated experimentally. Firstly, when the stator hub is sealed, the hub corner stall will occur at small mass flow rate conditions. Then, when a very small stator hub clearance is introduced, the leakage flow tends to strengthen the hub corner separation at large mass flow rate conditions and prompts the occurrence of hub corner stall as the mass flow rate decreases. This is mainly caused by the fact that the leakage flow has relatively low energy due to the viscosity effect in the clearance and large flow loss generation as the clearance flow comes across and mixes with the transverse secondary flow. Finally, when the stator hub clearance increases, the effect of the flow viscosity becomes very weak and could be ignored, so the enhanced leakage flow can suppress the transverse migration of the low energy flow near the hub, and the hub corner separation at large mass flow rate conditions could be weakened and the hub corner stall at small mass flow rate conditions could be removed or delayed. As the stator hub clearance varies, the flow structures inside the stator passage could be summarized into five typical flow structures, and this is closely associated with the performance of the compressor.

Numerical investigations on detonations in a condensed-phase explosive and oblique shock waves in surrounding fluids

In this work, we studied detonation in condensed-phase explosives of PETN and the oblique shock waves in the surrounding fluid. The surrounding fluid was modeled as an ideal gas equation of state using the specific heat ratio as a parameter. Depending on the specific heat ratio, four types of flow structures were observed behind the oblique shock wave in the ideal gas. We measured the detonation/shock angles and the contact angle between the detonation products and the ideal gas. When the specific heat ratio was greater than the critical value, the oblique shock wave was detached from the detonation front at the PETN/ideal gas interface. When attached, three types of waves are observed, depending on the specific heat ratio: a strong oblique shock wave, strong and weak oblique shock waves which meet at the triple point as well as a weak oblique shock wave. To understand the properties of the flow near the detonation and the oblique shock waves, they were modeled as planar Chapman–Jouguet (CJ) detonation in PETN and as oblique shock waves in ideal gas. They were theoretically estimated as (1) Prandtl–Meyer expansion of the detonation products from the CJ state, and (2) oblique shock waves around a wedge using oblique shock theory or around a cone using the Taylor–Maccoll equation. From the flow models, we obtained a solution for the pressure equilibrium and parallel flows between the detonation products and ideal gas under the assumption that the wedge and cone angles correspond to the contact angle between them. For the attached cases, the solution was consistent with the simulated observations at the PETN/ideal gas interface. From the flow models, the maximum deflection angles for the detonation products and the ideal gas were obtained, and their magnitude correlations used to classify the four types of flow.

Fine structures of self-sustaining dual jets in supersonic crossflow

The interaction between self-sustaining dual jets and supersonic laminar boundary layer is experimentally studied using the nanoparticle-based planar laser scattering in a Ma 2.95 supersonic low-turbulence wind tunnel for the first time. The typical fine flow structures, such as separation shock, “W” bow shock, barrel shock, horseshoe vortex, large-scale vortex structures and counter-rotating vortex pairs, are clearly identified by streamwise and spanwise flowfield images. The curves of jet penetration depth are fitted at the momentum ratio of 0.55 between self-sustaining dual jets and supersonic crossflow. The results play a significant role in further and comprehensive exploration of the active flow control for a supersonic flow.

Effects of spiral start number and depth ratio of corrugated tube on flow and heat transfer characteristics in turbulent flow region

Influence of spirally-corrugated tubes on heat transfer (Nu), pressure loss (f) and thermal enhancement factor (TEF) characteristics was numerically investigated. The physical models of spirally-corrugated tubes and also a straight circular tube were built for the comparative study. The predictions were performed for the spirally-corrugated tubes with spiral start numbers (N) of 2, 3, 4 and 5 and depth ratios (DR = e/D) of 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14 and 0.16 at Reynolds numbers of 5000, 8000, 14000 and 20000. The numerical results show that the spiral corrugated tubes created two types of flow structures: main swirl flows (appear around the core) and secondary swirl flows (appear near tube wall) which facilitate heat transfer between the fluid and the tube walls. The overall heat transfer depends on the competition between two effects: the positive effect of the stronger swirl intensity by increasing start number and the negative effect of the difficulty of fluid transfer into grooves by increasing depth ratio. For the investigated range, the corrugated tubes yield Nusselt numbers and thermal performance factors varying from 0.82 to 2.16 times and 0.66–1.2 times of the straight circular tube, respectively. The highest thermal enhancement factor (TEF) of 1.2 is achieved by using the tube with spiral start number of 4 having moderate depth ratio of 0.08 at Re = 5000.

Direct numerical simulation of a supersonic turbulent boundary layer subject to adverse pressure gradient induced by external successive compression waves

A freestream Mach 2.9 flat-plate supersonic turbulent boundary layer subject to a “pure” adverse pressure gradient (APG) without the impact of wall curvatures is studied by direct numerical simulation and compared with a benchmark flow with zero pressure gradient. Due to APG, the streamwise velocity shows an increase in the near-wall region and a reduction in the outer boundary layer. The principal strain rate shows a sandwich distribution along the wall-normal direction. The mismatch between the temperature and velocity fluctuations in both the inner and the outer layer is observed. Enhanced LSMs (large-scale motions) and large velocity patches are the typical flow structures in the outer and inner boundary layer subject to APG, respectively. From the analysis of quadrant decomposition, the sweep events dominate in the near-wall region while ejection events dominate the rest of the boundary layer. It is found that the baroclinicity plays a significant role in the formation of the enhanced LSMs in the outer boundary layer and the near-wall velocity patches. The resulting amplified vorticity further drives the interactive motions of the outer fluid and inner fluid. The turbulent kinetic energy and turbulent Mach number profiles are amplified by APG and a second peak is observed in both profiles. Turbulent energy budget analysis demonstrates that both the production and viscous effects are strengthened in the near-wall region while in the outer layer, the production is significantly amplified and balanced by the increased convection and turbulent transport.

The structure of viscoplastic fluid flow during filling of a circular pipe / plane channel

The investigation of a viscoplastic fluid flow initiated in a circular pipe/plane channel during its filling in the gravity field at the flow rate specified at the inlet section is carried out. A mathematical formulation of the problem is developed using complete equations of motion, continuity equation, natural boundary conditions on the free surface, and no-slip boundary conditions on the solid wall. The rheological behavior of the medium is described by the Shvedov-Bingham law, which implies the existence of zones with quasi-solid motion (unyielded zones) in the regions of low strain rate. The numerical solution of the problem is based on the finite-difference approach with an application of the finite volume method and SIMPLE algorithm for calculating velocity and pressure fields at the internal nodes of a staggered grid. The method of invariants is used to satisfy the boundary conditions on the free surface. To provide a through computation of the flow with unyielded regions, a regularization of the rheological equation is implemented. The investigation of the free boundary behavior, flow structure, and flow characteristics as a function of the main parameters is carried out. It was found that in the course of time the initially flat free boundary assumes a stationary convex shape, which remains invariant moving through the pipe/channel at an average velocity. In the flow near and far away from the free boundary one can distinguish the fountain flow zones and the one-dimensional flow regions, respectively. The typical flow structures with different number and various locations of unyielded regions in the flow are shown. The topograms of the above mentioned flow structures are plotted as a function of the ratio of viscous and gravity forces and plasticity in the fluid flow. The stable and unstable behavior of the free boundary shape is shown to be related to the values of the constitutive parameters.

Characteristics of a Cavity-Stabilized Hydrogen Jet Flame in a Model Scramjet Combustor

The characteristics of a hydrogen jet flame in a one-sided divergent scramjet combustor are investigated using both experiments and large-eddy simulations. Optical observations provide macroscopic insight into the typical flow structures and reaction zone. The combustor operates in a cavity-stabilized combustion mode, in which a stable flame is anchored in the cavity shear layer and spreads into the jet wake. Particular attention is paid to the effect of turbulence on hydrogen combustion, which is often difficult or impossible to measure experimentally. Therefore, a high-fidelity simulation of sonic hydrogen jet injection into a scramjet combustor is conducted to provide a detailed description of the three-dimensional unsteady reacting flow. Autoignition occurs along the windward jet boundary, but the flame cannot be sustained due to the high local scalar dissipation rate. Two pairs of large-scale recirculation zones are generated in the cavity. Reflux with a long-flow residence time entrains hot intermediate products into the cavity, which continuously ignite the mixture in the jet wake. Then, the steady turbulent diffusion flame governs the combustion downstream of the cavity, and a large amount of chemical heat is released close to the stoichiometric mixture fraction.

PIV measurements of the K-type transition in natural convection boundary layers

The K-type transition of a natural convection boundary layer of Ra = 9.8 × 109 is studied by PIV (Particle Image Velocimetry) measurements. To excite the transition, Tollmien-Schlitchting (TS) and oblique waves of the same frequency are introduced into the upstream boundary layer in the form of velocity perturbations. It is found that resonant interactions between the characteristic frequency of the natural convection boundary layer and the superimposed TS and oblique waves are present, which trigger the K-type transition of the boundary layer. The typical aligned Λ-shaped flow structures characterising the K-type transition present in the transition of Blasius boundary layers are also observed in the present natural convection boundary layers. They occur when the primary instability grows to a certain extent. The appearance of the spanwise mode characterised by the aligned Λ-shaped flow structures is found to be an ‘abrupt’ process, although the development of the three-dimensionality in the natural convection boundary layer is found to be a ‘gradual’ process. A peak in the typical profile of the Root-Mean-Square (RMS) of the amplitude of streamwise velocity is also noted around the transition point, beyond which distinct three-dimensional Λ-shaped flow structures are observed. The transition point has been determined consistently using different approaches. A Bicoherence analysis suggests that the interaction between the external excitation frequency and the characteristic frequency of the boundary layer is responsible for the production of new harmonic frequencies and resonance groups. The PIV measurements have been extended to a range of perturbation frequencies for the boundary layer, and the dependence of the K-type transition on the perturbation frequency is discussed.

Experimental and numerical investigation on the pressure pulsation and instantaneous flow structure in a nuclear reactor coolant pump

Abstract The instantaneous vortical flow structure is one of the typical flow structures inside the nuclear reactor coolant pump (RCP), which would cause the unsteady pressure pulsations, vibrations of the unit and fatigue of components. Due to high safety requirement of the RCP during the actual operation of the nuclear power plants (NPPs), revealing instantaneous nature of vortical flow structure and its pressure pulsation becomes a crucial issue for studying the internal flow mechanism of the RCP. The purpose of this study is to shed comprehensive light on the pressure pulsation and instantaneous vortical flow structure in the RCP by using the experimental method and the numerical simulation method. Based on the result of comparison with the experiment and numerical simulation, it can be considered that the LES method can better identify instantaneous nature of vortical flow structures in the low frequency band. The instantaneous vortical flow structure is attached to the impeller RBPS (rotor blade pressure surface) and transient jet wake vortex flow structures between the impeller and diffuser under the rotor-stator interaction effect are fairly obvious by Q-criterion. On the other hand, in the axial-vorticity component distribution, the rotor-stator interaction effect between the impeller and diffuser cannot be clearly revealed. From the three-dimensional structures, the main vortex structures are in the front and back cavity of the right-hand side near the discharge nozzle and the right-hand side below the discharge nozzle in the spherical casing. Meanwhile, combined with pressure spectrum, it is convinced that their unsteady characteristic is the main reason that causes complex excitation frequencies in the low frequency band of the right-hand side near the discharge nozzle.

Experimental exploration of inlet start process in continuously variable Mach number wind tunnel

The flow structures of the inlet in continuously variable Mach number inflow are studied experimentally to evaluate accurately the performance of scramjet inlet during acceleration/deceleration in ground experiments. To break the limitation in which majority of supersonic wind tunnels operate at a fixed Mach number condition, a continuously variable Mach number wind tunnel has been built. The running Mach number of the wind tunnel varies continuously from 2.0 to 3.0 under suction mode. The experiments of the inlet at fixed and variable Mach number inflows are conducted successively in the continuously variable Mach number wind tunnel. In the fixed Mach number experiment, the typical flow structures of the inlet under the unstart/start conditions are captured. The pressure distributions on the lower wall of the inlet, which were obtained from the experiments, are consistent with numerical ones. Thus, the effectiveness and accuracy of the experiments and numerical simulations were verified. In the continuously variable Mach number wind tunnel experiment, we found the inlet suffers from four flow structures. With the exception of typical unstart/start flow structures, the inlet undergoes pseudo unstart/start conditions under the influence of the wind tunnel unstart. By analyzing the pressure and Schlieren result, variations in the flow structures are observed in detail, which can provide useful references for the subsequent experiments in continuously variable Mach number wind tunnels. In particular, pseudo unstart/start conditions must be distinguished from real ones in the case wrong experimental data are obtained in the following experiments.

CALCULATION OF ROCKET NOSE FAIRING SHELLS AERODYNAMIC CHARACTERISTICS

The aerodynamic characteristics of the detachable elements of transport systems are introduced, they allow to calculate the trajectories of these elements after their separation and determine the size of elements impact areas. Special consideration is given to head fairing shells, containing cylindrical, conical and spherical sections. Head fairing shells have high lift-to-drag ratio and the widest impact areas. Aerodynamics of bodies of such configurations has been insufficiently studied. The paper presents the numerical results of modeling the flow around a typical head fairing shell in free flight. Open source OpenFOAM package is used for numerical simulation. The aerodynamic characteristics at trans- and supersonic velocities are obtained, flow pattern transformation with the change of the angle of attack and Mach number is analyzed. The possibility of OpenFOAM package for aerodynamic calculations of thin shells is shown. The analysis of the obtained results demonstrate that there are many complex shock waves interacting with each other at flow supersonic speeds, at subsonic speeds vast regions of flow separations are observed. The authors identify intervals of angles of attack, where different types of flow structures are realized, both for trans- and supersonic flow speeds. The flow pattern change affects the aerodynamic characteristics, the aerodynamic coefficients significantly change with increase of the angle of attack. There are two trim angles of attack at all examined flow velocities. The results obtained can be used to develop a passive stabilization system for fairing shell that will balance the body at the angle of attack with minimum lift-to-drag ratio and will reduce random deviations.

Experimental and numerical evaluation of slugs in a vertical air–water flow

Multiphase flows are often present in chemical processes and they include gas-liquid transport, which may become intermittent depending on the operating conditions. One type of flow structure is the presence of large gas bubbles that can occupy the entire duct diameter, separated by liquid portions. This can result in large pressure fluctuations, which are normally associated with damage to equipment over time. The intermittent nature and the chaotic distribution of the phases in a turbulent flow complicate the design and optimization of the equipment. In this context, computational fluid dynamics is a useful technique since it can provide important information on several flow conditions, but the use of suitable models and boundary conditions is required. In this study, an air and water flow with the presence of slugs is evaluated in a system consisting of horizontal and vertical ducts, with an inner diameter of 94 mm. Experimental data on the pressure and void fraction were analyzed and compared to the predictions obtained from numerical simulations, obtained considering the VOF approach. It was observed that the use of the geometrical reconstruction scheme to simulate a compressible flow resulted in a better agreement with the experimental results. Using this setup, the average volume fraction and pressure values showed the expected behavior. The frequency of slugs, established using three different methods, was around 1.5 Hz for the evaluated conditions evaluated. The pressure probability density function (PDF) indicated good agreement between numerical simulations and experimental data, while the volume fraction PDF indicated that the flows evaluated have the characteristics of a churn flow regime. Moreover, it was found that an increase in the water flow rate can lead an increase or a decrease in the average velocity.

Numerical simulation and analysis of condensation shocks in cavitating flow

We analyse unsteady cavity dynamics, cavitation patterns and instability mechanisms governing partial cavitation in the flow past a sharp convergent–divergent wedge. Reproducing a recent reference experiment by numerical simulation, the investigated flow regime is characterised by large-scale cloud cavitation. In agreement with the experiments, we find that cloud shedding is dominated by the periodic occurrence of condensation shocks, propagating through the two-phase medium. The physical model is based on the homogeneous mixture approach, the assumption of thermodynamic equilibrium, and a closed-form barotropic equation of state. Compressibility of water and water vapour is taken into account. We deliberately suppress effects of molecular viscosity, in order to demonstrate that inertial effects dominate the flow evolution. We qualify the flow predictions, and validate the numerical approach by comparison with experiments. In agreement with the experiments, the vapour volume fraction within the partial cavity reaches values${>}80\,\%$for its spanwise average. Very good agreement is further obtained for the shedding Strouhal number, the cavity growth and collapse velocities, and for typical coherent flow structures. In accordance with the experiments, the simulations reproduce a condensation shock forming at the trailing part of the partial cavity. It is demonstrated that it satisfies locally Rankine–Hugoniot jump relations. Estimation of the shock propagation Mach number shows that the flow is supersonic. With a magnitude of only a few kPa, the pressure rise across the shock is much lower than for typical cavity collapse events. It is thus far too weak to cause cavitation erosion directly. However, by affecting the dynamics of the cavity, the flow aggressiveness can be significantly altered. Our results indicate that, in addition to classically observed re-entrant jets, condensation shocks feed an intrinsic instability mechanism of partial cavitation.

Visualization of Supersonic Low-Noise Flow Over Surface-Mounted Two-Dimensional Prisms

An experimental study of supersonic flow over two-dimensional surface-mounted prisms is carried out in a Mach 3 low-noise wind tunnel. The noise level of this supersonic wind tunnel, defined as the root mean-square Pitot pressure fluctuation normalized by the mean Pitot pressure, can be reduced to about 0.37%. The nanotracer planar laser scattering (NPLS) technique is used to analyze the influence of the prism geometry and the oncoming flow conditions on the typical flow structures including separation and reattachment shocks. With increase in the prism height the induced shocks move upstream. At a constant streamwise length L of a prism the timeaveraged NPLS images show that the length of the downstream recirculation region increases from 0.8L to 1.2L, when the prism height H changes from 3 to 5 mm. As compared with the flow structures occurring downstream of the prisms, the upstream flow structures are more susceptible to the oncoming boundary layer and are considerably different in laminar and turbulent flows. The separation shock wave is clearly visible in turbulent flow even for the 1-mm prism, whereas in the case of laminar flow there is no a distinct shock wave upstream of this prism. At the same time, the location of the flow reattachment and the angle of the reattachment shock wave in the downstream flow remain almost the same in both two flow regimes.

Hydrodynamics in a jet bubbling reactor: Experimental research and mathematical modeling

The radial distribution of liquid velocity in the axial direction of a jet bubbling reactor has been measured by experimentation. Three different typical flow structures controlled by liquid jet, gas bubbling, and liquid jet coupled with bubbling are observed. A tank in series model is established on this basis. Calculated values in each region are in good agreement with measured values in jet, bubbling, and wall effect controlled areas. Axial flow rate, radial exchange rate, and jet controlled volume η are analyzed from energy input aspect under different ug and uj. Simulation results indicate that under the synergetic action of the liquid jet and gas bubbling effect, jet controlled area exhibits a “spindle” structure, and its size decreases with the increase of ug. When gas input power occupies about 67% of total energy consumption, the best synergy of liquid jet and gas bubbling is obtained. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1814–1827, 2018

Geometry of tracer trajectories in rotating turbulent flows

The geometry of passive tracer trajectories is studied in two different types of rotating turbulent flows; rotating Rayleigh-Benard convection (RBC; experiments and direct numerical simulations) and rotating electromagnetically forced turbulence (EFT; experiments). This geometry is fully described by the curvature and torsion of trajectories, and from these geometrical quantities we can subtract information on the typical flow structures at different rotation rates. Previous studies, focusing on nonrotating homogeneous isotropic turbulence (HIT), show that the probability density functions (PDFs) of curvature and torsion reveal pronounced power laws. However, the set-ups studied here involve inhomogeneous turbulence, and in RBC the flow near the horizontal plates is definitely anisotropic. We investigate how the typical shapes of the curvature and torsion PDFs, including the pronounced scaling laws, are influenced by this level of anisotropy and inhomogeneity and how this effect changes with rotation. A first effect of rotation is observed as a shift of the curvature and torsion PDFs towards higher values in the case of RBC and towards lower values in the case of EFT. This shift is related to the length scale of typical vortical structures that decreases with rotation in RBC, but increases with rotation in EFT, explaining the opposite shifts of the curvature (and torsion) PDFs. A second remarkable observation is that in RBC the HIT scaling laws are always recovered, as long as the boundary layer (BL) is excluded. This suggests that these scaling laws are very robust and hold as long as we measure in the turbulent bulk. In the BL of the RBC cell, however, the scaling deviates from the HIT prediction for lower rotation rates. This scaling behavior is found to be consistent with the coupling between the boundary layer dynamics and the bulk flow, which changes under rotation. In particular, it is found that the active coupling of the Ekman-type boundary layer with the bulk flow suppresses anisotropy in the BL region for increasing rotation rates.

Supercritical flow simulation at a right channel junction. Comparison between a uniform and a sparse mesh

This technical note studies the supercritical junction flow occurring at the right-angled confluence of four equal-width channels in which two upstream channels carry flow towards the junction. The note seeks to investigate, firstly, the pertinence of a 2D shallow water equation model to reproduce the typical flow structures at the junction. The second objective is to build a computationally efficient model with more resolution applied at critical point i.e. junction and less in areas where the flow is primarily 1D i.e. channels and compare such model, named, ‘sparse’ with a uniformly meshed model regarding solution accuracy and computational efficiency. The results indicate that the sparse model is able to reproduce typical flow structures appearing at the channel junction in an adequate manner. The discharge distribution is fairly well predicted. The jump angles are almost the same in the two models as well as the location and size of the recirculation zones and the flow depth super-elevation areas. However, the two models diverge in the prediction of very small depths in the recirculation zone where the sparse model overestimates the depths. As regards, computational efficiency, the sparse model is found to be 61% more efficient than the uniform mesh model.