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Swirl number and nozzle confinement effects in a flatvane axial swirler Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210805
I.V. Litvinov, D.A. Suslov, E.U. Gorelikov, S.I. ShtorkThis paper presents the results of a parametric experimental study of free swirling flow at the exit of a flatvane axial swirler. A total of 16 data sets were acquired by combining four swirler vane angles (22°, 29°, 50.5°, and 58.3°) and four exit nozzles of different diameters (30, 40, 52, and 76 mm). Sophisticated pressure probes consisting of precise microphones and a twocomponent LDV system

The influence of wall heating on turbulent boundary layer characteristics during mixed convection Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210729
Kadeem Dennis, Kamran SiddiquiAn investigation on the modification of turbulent boundary layer characteristics by wall heating was conducted on the mixed convection turbulent boundary layer flow. The multiplane particle image velocimetry (PIV) technique was used to characterize turbulent boundary layer dynamics. Experiments were performed over a range of mixed convection flow conditions, quantified by the Richardson number (Ri)

Direct numerical simulation of the twodimensional speed bump flow at increasing Reynolds numbers Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210722
Mikhail L. Shur, Philippe R. Spalart, Mikhail Kh. Strelets, Andrey K. TravinThe Speed Bump flow model was designed by Boeing to provide a mildly threedimensional flow with separation from a very smooth surface, strongly controlled by the turbulence. Experiments are conducted by several teams, as are simulations, over a range of Reynolds numbers. Direct Numerical Simulations (DNS) are not possible for the full 3D geometry of width L, leading several groups to conduct DNS over

RANS simulations for transition and turbulent flow regimes in wirewrapped rod bundles Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210707
Octavio Bovati, Mustafa Alper Yildiz, Yassin Hassan, Rodolfo VaghettoInternal flows through rod assemblies are commonly found in heat exchangers, steam generators, and nuclear reactors. One of the fuel assembly designs considered for liquid metalcooled reactors utilizes wires helically wrapped around each fuel rod as spacers. The wires keep the fuel pins separated, enhancing the turbulent mixing, and heat transfer, but also affecting the pressure drop. It is of interest

Velocity and concentration field measurements and large eddy simulation of a shaped film cooling hole Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210628
Ian E. Gunady, Pedro M. Milani, Andrew J. Banko, Christopher J. Elkins, John K. EatonThe 3D velocity and scalar concentration fields from a laidback fanshaped film cooling hole are measured using Magnetic Resonance Velocimetry (MRV) and Magnetic Resonance Concentration (MRC). The velocity and scalar concentration fields of the same geometry are also obtained using Large Eddy Simulation (LES). The geometry under consideration features a single film cooling hole with a 30° inclination

Flow through an elbow: A direct numerical simulation investigating turbulent flow quantities Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210628
Ravon Venters, Brian T. Helenbrook, Goodarz Ahmadi, Douglas Bohl, Andrew BluesteinTurbulent flow in a sharp 90° elbow in a square duct was numerically investigated by performing a direct numerical simulation (DNS) and the results were compared to experimental and Reynolds Averaged Navier–Stokes (RANS) data. This is the first part of an effort to expand the understanding of particle transport in complex geometries. The paper is divided into two parts: a validation of the flow, and

A new numerical method for determining heat transfer and packing distribution in particle heat exchangers for concentrated solar power Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210624
Sahan Trushad Wickramasooriya Kuruneru, Yen Chean Soo Too, JinSoo KimThe complex nature of the physics of solidgas interactions in concentrated solar particle heat exchangers signifies the need to develop new and cuttingedge numerical models to understand these interactions with the overarching goal of optimizing industrial solar thermal processes. To this end, a coupled computational fluid dynamics and discrete element method is developed to unravel nearwall particle

Experimental investigation of the effect of cross wire on the flow field of elliptic jet Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210617
Mohammed Faheem, Aqib Khan, Rakesh Kumar, Sher Afghan Khan, Waqar Asrar, Mohd Azan Mohammed SapardiThe effectiveness of cross wire in controlling the mixing characteristics of a circular and an equivalent elliptic jet is investigated experimentally. While circular jets are conventional, elliptic jets have gained attention due to their better mixing characteristics and faster decay. To further explore and augment the capabilities of elliptic jets for practical utility, it is investigated whether

Direct numerical simulation of fluid flow in a 5x5 square rod bundle Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210617
Adam Kraus, Elia Merzari, Thomas Norddine, Oana Marin, Sofiane BenhamadoucheCharacterization of parallel flow through rod bundles is of key importance in assessing the performance and safety of several engineering systems, including a majority of nuclear reactor concepts. Inhomogeneities in the bundle crosssection can present complex flow phenomena, including varying local conditions of turbulence. With the everincreasing capabilities of highperformance computing, Direct

Direct numerical simulation of a turbulent plane CouettePoiseuille flow with zeromean shear Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210615
Yun Kyung Choi, Jae Hwa Lee, Jinyul HwangDirect numerical simulations of a turbulent CouettePoiseuille flow with zeromeanshear at the moving wall (SLflow) is performed to examine flow features compared to those for a turbulent pure Poiseuille flow (Pflow). Profiles of the streamwise mean velocity, indicator function and ratio of production to dissipation show that the logarithmic region is significantly elongated for the SLflow compared

Impact of density stratification on the global mode in a swirling jet: Stochastic modelling and Lagrangian coherent structures Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210614
Moritz Sieber, Cristian Oliver Paschereit, Kilian OberleithnerIn an experimental investigation, the stochastic dynamics of the global mode in a turbulent swirling jet are considered. From the application of the swirling jet in gas turbine combustors, it was observed that a specific density gradient in the flow leads to a suppression of the global mode. This phenomenon was replicated in a generic swirling jet using an electrical heating coil placed inside the

Aerodynamic drag reduction by means of platooning configurations of light commercial vehicles: A flow field analysis Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210611
J.J. Cerutti, G. Cafiero, G. IusoPlatooning configurations of two, three and four commercial vehicles were tested at a Reynolds number based on the vehicle’s length (L) of230000. The platoon configurations were obtained using an instrumented model, and three wooden replicas located at different positions with respect to the instrumented one. The reference model presents a slant angle at the leading edge, which can produce, in principle

Evolution of a wallattached buoyant plume in confined boxes: Direct numerical simulations, entrainment coefficient and an integral model Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210611
Nitheesh George, Andrew Ooi, Jimmy PhilipThe evolution of a wallattached plume in a confined box is studied here with the aid of three dimensional direct numerical simulations (DNS). The plume originates from a local line heat source of length, L, placed at the bottom left corner of the box. The Reynolds number of the wall plume, based on box height and buoyant velocity scale, is ReH=14530 and boxes of two different aspect ratios (ratio

Numerical analysis of the flow pattern in convergent vortex tubes for cyclone cooling applications Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210607
Florian Seibold, Bernhard WeigandThe use of swirling flows in cyclone cooling systems is a promising method for internal cooling applications for instance in the leading edge of gas turbine blades. However, vortex breakdown can occur in such flows, which is associated with an axial flow reversal. Within the scope of this investigation a numerical parameter study was conducted in order to explore the impact of convergent tube geometries

Benchmark PIV database for the validation of CFD simulations in a transitional cavity flow Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210529
A. Sciacchitano, F. Arpino, G. CortellessaWe present an experimental benchmark database for the transitional cavity flow. The database is obtained by planar Particle Image Velocimetry measurements at the median plane of the cavity model, for Reynolds numbers between 6300 and 19,000 based on the cavity height. A detailed uncertainty analysis of the experimental results is performed via the correlation statistics method for PIV uncertainty quantification

An iterative machinelearning framework for RANS turbulence modeling Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210524
Weishuo Liu, Jian Fang, Stefano Rolfo, Charles Moulinec, David R EmersonMachinelearning (ML) techniques provide a new and encouraging perspective for constructing turbulence models for Reynoldsaveraged NavierStokes (RANS) simulations. In this study, an iterative MLRANS computational framework is proposed that combines an ML algorithm with transport equations of a conventional turbulence model. This framework maintains a consistent procedure for obtaining the input

Flow investigation of circular cylinder having different cavities in shallow water Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210524
Atakan Tantekin, N. Filiz Tumen Ozdil, Hüseyin Akilli, Meltem CaliskanThe control of the unsteady flow structure formed behind a cylinder placed horizontally in shallow water was analyzed experimentally using bare cylinder and cylinders with cavities having square and rectangular geometries, respectively. Reynolds number, Froude number and water height had been chosen as 5000, 0.27 and 90 mm, respectively and also these parameters were kept constant for all experiments

On the use of a twolayer model for largeeddy simulations of supersonic boundary layers with separation Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210521
B. Zebiri, A. Piquet, A. HadjadjThe twolayer modeling approach has become one of the most promising and successful methodology for simulating turbulent boundary layers in the past ten years. In the present study, a mixed wall model for largeeddy simulations (LES) of highspeed flows is proposed which combine two approaches; the thinBoundary Layer Equations (TBLE) model of Kawai and Larsson (1994) and the analytical walllayer

Simulation of RayleighBenárd convection at up to Ra=1016 by generalized ellipticrelaxation hybrid RANSLES model Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210520
M. Hadžiabdić, M. Borrelli, B. NičenoWe performed simulations of RayleighBenárd convection (RBC) for very high Ra number, 109,1012,1013,1014 and 1016, thus beyond the reach of classical LES, by using an ellipticrelaxation hybrid RANSLES (ERHRL) model paired with a compound wall treatment that allows much coarser mesh resolution in the near wall region. The standard switching criterion used in the hybrid RANSLES modeling based on

An extensive numerical benchmark of the various magnetohydrodynamic flows Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210518
Artem Blishchik, Mike van der Lans, Saša KenjerešThere is a continuous need for an updated series of numerical benchmarks dealing with various aspects of the magnetohydrodynamics (MHD) phenomena (i.e. interactions of the flow of an electrically conducting fluid and an externally imposed magnetic field). The focus of the present study is numerical magnetohydrodynamics (MHD) where we have performed an extensive series of simulations for generic configurations

Recurrent neural networks and Koopmanbased frameworks for temporal predictions in a loworder model of turbulence Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210517
Hamidreza Eivazi, Luca Guastoni, Philipp Schlatter, Hossein Azizpour, Ricardo Vinuesa 
An improved kω turbulence model for FENEP fluids without friction velocity dependence Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210513
M. McDermott, P.R. Resende, M.C.T. Wilson, A.M. Afonso, D. Harbottle, G. de BoerAn improved kω turbulence model for viscoelastic fluids is developed to predict turbulent flows, with polymeric solutions described by the finitely extensible nonlinear elasticPeterlin constitutive model. The kω model is tested against a wide range of direct numerical simulation data in fullydeveloped channel flow, with different rheological parameter combinations, and can predict all regimes of

The uniformmomentum zones and internal shear layers in turbulent pipe flows at Reynolds numbers up to Reτ=1000 Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210507
Xue Chen, Yongmann M. Chung, Minping WanThe statistical characteristics of the internal shear layers (ISL) and the coherent structures around the ISLs in turbulent pipe flows are examined using direct numerical simulation data at four Reynolds numbers Reτ=180, 360, 500 and 1000. The ISLs are defined by the peaks on the velocity gradients with no ad hoc filter applied on the ISL selection. This is different from the previous studies where

Extension of the partially integrated transport modeling method to the simulation of passive scalar turbulent fluctuations at various Prandtl numbers Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210430
Bruno Chaouat, Roland SchiestelThe present work aims to extend the hybrid non zonal RANS/LES partially integrated transport modeling (PITM) method to turbulent flows in the presence of passive scalar contaminant for simulating large scales of turbulent flows. Focussing on the methodological aspects, we derive the basic transport equations both for the scalar variance of fluctuations and dissipationrate of the variance. The basis

A broad reconsideration of antivortex film cooling method using numerical optimization and an improved heatflux model Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210429
K. Chaharlang Kiani, K. MazaheriThis paper represents the detailed results of an evolutionary optimization framework towards the exploration of vortex mechanisms leading to effective antivortex film cooling. In this regards, several arrangements of triple cooling holes were studied on flat and curved geometries using differentialevolution optimization algorithm and a modified Reynoldsstress based flow solver. Depending on the

Experimental investigation of forced flow regime transition in a dual bell nozzle by secondary fluidic injection Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210428
L. Léger, V. Zmijanovic, M. Sellam, A. ChpounExperiments on an axisymmetric dualbell nozzle were performed at EDITH nozzle test facility of CNRS in Orléans, France. The main purpose of the study was to explore the possibility of controlling the flow regime transition by a secondary fluidic injection in the dual bell nozzle. The main focus of the present paper is to investigate the impact of the secondary injection parameters on the flow regimes

Numerical and experimental analysis of flow and heat transfer in a fuel assembly mockup with transverse flow above the rods Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210426
Tobias Hanisch, Patrick Zedler, Antonio Hurtado, Frank Rüdiger, Jochen FröhlichThermalhydraulic conditions in a partially uncovered nuclear fuel assembly mockup are studied with particular focus on the influence of the horizontal air flow above the rod bundle. The investigations are performed at the ALADIN test facility, which models a boiling water reactor fuel assembly at a 1:1 scale both axially and radially. In the scenario studied, the main heat transfer mechanisms – conduction

Analysis of turbulence structures and the validity of the linear Boussinesq hypothesis for an infinite tube bundle Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210424
Philipp Wellinger, Philipp Uhl, Bernhard Weigand, Jose RodriguezThe basis of many turbulence models in computational fluid dynamics is the linear Boussinesq hypothesis that assumes an alignment between the mean strain rate tensor and the Reynolds stress tensor. The validity of this main assumption is analyzed for the test case of an infinite tube bundle with periodic boundary conditions at Reb≈34,800. This work focuses on the application of five methods based on

Direct numerical simulation of turbulent heat transfer in a square duct with transverse ribs mounted on one wall Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210422
S.V. MahmoodiJezeh, BingChen WangTurbulent heat transfer in a ribbed square duct of three different blockage ratios are investigated using direct numerical simulation (DNS). The results of ribbed duct cases are compared with those of a heated smooth duct flow. It is observed that owing to the existence of the ribs and confinement of the duct, organized secondary flows appear as large streamwiseelongated vortices, which intensely

Large eddy simulation and experiment of shear breakup in liquidliquid jet: Formation of ligaments and droplets Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210422
Cosan Daskiran, Xinzhi Xue, Fangda Cui, Joseph Katz, Michel C. BoufadelUnderstanding the shear breakup in jet flows and the formation of droplets from ligaments is important to determine the final droplet size distribution (DSD). The initial droplet size, which affects the final DSD, is considered to be generated by the shear breakup. Large eddy simulation (LES) was performed to investigate the shear breakup in liquidliquid jet flows. The explicit Volume of Fluid (VOF)

Modelling turbulent heat flux accounting for TurbulenceRadiation Interactions Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210421
S. Silvestri, D.J.E.M. Roekaerts, R. PecnikThe present work investigates the modeling of turbulent heat transfer in flows where radiative and convective heat transfer are coupled. In high temperature radiatively participating flows, radiation is the most relevant heat transfer mechanism and, due to its nonlocality, it causes counter intuitive interactions with the turbulent temperature field. These socalled TurbulenceRadiation Interactions

Effect of largescale structures on bursting phenomenon in turbulent boundary layer Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210416
Xiaonan Chen, Koji Iwano, Yasuhiko Sakai, Yasumasa ItoThis study investigated the effect of largescale structures including largescale motions (LSMs) and hairpin vortex in the logregion on the bursting phenomenon in the buffer layer using the simultaneous measurement of the streamwise velocity fluctuation in the logregion and buffer layer of the turbulent boundary layer (TBL) with a multichannel hotwire probe. The Reynolds number in the present

A CFD model of frost formation based on dynamic meshes technique via secondary development of ANSYS fluent Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210416
Yonghua You, Sheng Wang, Wei Lv, Yuanyuan Chen, Ulrich GrossTo simulate the nonuniform frost growth in flow direction for humid air flowing through a freezing channel, a 2D numerical frosting model based on dynamic meshes technique is developed in the current work via the secondary development of commercial ANSYS Fluent. The computation domain consists of both frost layer and humid air regions, and the local heat and vapor fluxes at the surface of frost layer

Numerical study of flow and heat transfer during a highspeed microdrop impact on thin liquid films Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210414
Swati Singh, Arun K. SahaNumerical simulation of highspeed microdroplet impingement on thin liquid film covering a heated solid surface has been carried out. Effect of droplet Weber number and liquid film thickness on the characteristics of flow and heat transfer has been investigated using the coupled level set and volume of fluid method. The code is validated against both the experimental and numerical results from the

Conjugate heat transfer in the unbounded flow of a viscoelastic fluid past a sphere Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210412
F. Pimenta, M.A. AlvesThis work addresses the conjugate heat transfer of a simplified PTT fluid flowing past an unbounded sphere in the Stokes regime (Re = 0.01). The problem is numerically solved with the finitevolume method assuming axisymmetry, absence of natural convection and constant physical properties. The sphere generates heat at a constant and uniform rate, and the analysis is conducted for a range of Deborah

Wakes of thin flat plates: Intermittency, cessation of vortex shedding and the emergence of an intermediatewake instability Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210412
Man Mohan RaiThe near and intermediate wake regions of thin flat plates with both sharp and circular trailing edges (TEs) are investigated with direct numerical simulations (DNSs). The TE is circular in two of the cases (IN & NS) and sharp in one of them (ST). The separating boundary layers are turbulent in all cases. The main objective here is to explore the effect of significantly reducing the Reynolds number

LES analysis of fire source aspect ratio effects on firewind enhancement Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210409
Esmaeel Eftekharian, Fatemeh Salehi, Yaping He, Kenny C.S. KwokEnhancement of wind by bushfire, referred to as bushfirewind enhancement phenomenon, causes damages to buildings located in bushfireprone areas by increasing pressure load around the structures. This study focuses on the effects of point source aspect ratio (AR) on the wind enhanced by fire. FireFOAM solver of OpenFOAM platform is used to perform Large Eddy Simulation analysis for different fire

LES study on the influence of the diffuser inlet angle of a centrifugal pump on pressure fluctuations Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210331
Antonio PosaLargeEddy Simulations are conducted on a centrifugal pump at design and reduced flowrates for three diffuser geometries, to investigate the effect of changing the diffuser inlet angle on the overall performance and the pressure fields. In particular, pressure fluctuations are investigated, which affect the unsteady loads acting on the pump, as well as vibrations, noise and cavitation phenomena. The

Intense reynoldsstress events in turbulent ducts Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210321
Marco Atzori, Ricardo Vinuesa, Adrián LozanoDurán, Philipp SchlatterThe aim of the present work is to investigate the role of intense Reynolds shearstress events in the generation of the secondary flow in turbulent ducts. We consider the connected regions of flow where the product of the instantaneous fluctuations of two velocity components is higher than a threshold based on the longtime turbulence statistics, in the spirit of the threedimensional quadrant analysis

Analysis of highorder velocity moments in a strained channel flow Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210318
Svetlana V. Poroseva, Scott M. MurmanIn the current study, model expressions for fifthorder velocity moments obtained from the truncated GramCharlier series expansions model for a turbulent flow field probability density function are validated using data from direct numerical simulation (DNS) of a planar turbulent flow in a strained channel. Simplicity of the model expressions, the lack of unknown coefficients, and their applicability

Heat transfer and skinfriction in a turbulent boundary layer under a nonequilibrium longitudinal adverse pressure gradient Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210313
N.A. Kiselev, A.I. Leontiev, Yu.A. Vinogradov, A.G. Zditovets, S.S. PopovichThe experimental data on the effect of weak and moderate nonequilibrium adverse pressure gradients (APG) on the parameters of dynamic and thermal boundary layers are presented. The Reynolds number based on the momentum thickness at the beginning of the APG region was Re** = 5500. The APG region was a slot channel with upper wall expansion angles from 0 to 14°. The profiles of the mean and fluctuation

Electrothermoconvection in a differentially heated square cavity under arbitrary unipolar injection of ions Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210309
R. Deepak Selvakumar, Jian Wu, Junyu Huang, Phillipe TraoréA numerical investigation of electrothermoconvection in a 2D differentially heated square cavity filled with a dielectric liquid is presented. Fully coupled governing equations of electric potential, charge transport, Navier–Stokes equations, and the energy equation are implemented in the finitevolume framework of OpenFOAM®. For this kind of electrothermoconvection, previous studies mainly focused

Onset of shearlayer instability at the interface of parallel Couette flows Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210309
Kalluri M. Teja, Vagesh D. Narasimhamurthy, Helge I. Andersson, Bjørnar PettersenA nonplanar or a bilateral mixinglayer is studied by means of a series of direct numerical simulations (DNSs). This mixinglayer forms at the interface of two cocurrent plane Couette flows of different Reynolds numbers. The current DNS study determined the conditions for the onset of shearlayer instability at the interface. The influence of different Reynolds number (of the cocurrent plane Couette

Largeeddy simulation of turbulent channel flow at transcritical states Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210305
A. Doehring, T. Kaller, S.J. Schmidt, N.A. AdamsWe present wellresolved largeeddy simulations (LES) of a channel flow solving the fully compressible Navier–Stokes equations in conservative form. An adaptive lookup table method is used for thermodynamic and transport properties. A physically consistent subgridscale turbulence model is incorporated, that is based on the Adaptive Local Deconvolution Method (ALDM) for implicit LES. The wall temperatures

Dynamics of the jet flow issued from a lobed Nozzle: Tomographic particle image velocimetry measurements Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210304
Chuangxin He, Yingzheng Liu, Lian GanThis study focuses on the dynamics of the threedimensional jet flow issued from a lobed nozzle. Flow field measurements were performed using a splitscreen dualcamera tomographic particle image velocimetry (tomoPIV) system. The lobed nozzle was constructed using threecircle configuration at the nozzle exit, where the ratio of the circular centre offset to the circle radius was a/b=0.8. Two highspeed

Experimental study on the intrusion and stratification produced by confined laminar and turbulent round fountains Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210219
Liqiang Dong, Wenxian Lin, Mehdi KhatamifarIn this paper, highspeed cameras and flow visualization techniques are used to investigate the behavior of the ‘fountain filling box’ flow resulted from releasing a round fountain in a homogeneous quiescent fluid in a cylindrical container over the ranges of 1.0⩽Fr⩽20.0,102⩽Re⩽1502, and 27.9⩽λ⩽48.75, where Fr,Re and λ are the Froude number, the Reynolds number, and the dimensionless radius of the

Large eddy simulations of forced and stably stratified turbulence: Evolution, spectra, scaling, structures and shear Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210218
Rahul Agrawal, Abhilash J. ChandyLarge eddy simulations (LES) of forced stratified turbulence in a triplyperiodic box at multiple Froude numbers (Fr0) are carried out to study the effect of stratification on energy evolution, spectra, scaling, vortical structures and shear for flows at Re=25000. The dynamic Smagorinsky model is used as the subgrid scale (SGS) closure with a grid density of 963. A threedimensional (3D) continuous

Lower drag and higher lift for turbulent airfoil flow by moving surfaces Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210205
Marian Albers, Wolfgang SchröderLargeeddy simulations of the flow over an actuated NACA4412 airfoil at a chordbased Reynolds number Rec=400,000 are conducted. These solutions extend the previous analysis of an actuated DRA2303 airfoil flow since both flow configurations possess completely different pressure distributions. The technique of spanwise traveling transversal surface waves is used to improve the aerodynamic efficiency

Prediction of the drag reduction effect of pulsating pipe flow based on machine learning Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210205
Wataru Kobayashi, Takaaki Shimura, Akihiko Mitsuishi, Kaoru Iwamoto, Akira MurataPrediction of drag reduction effect caused by pulsating pipe flows is examined using machine learning. First, a large set of flow field data is obtained experimentally by measuring turbulent pipe flows with various pulsation patterns. Consequently, more than 7000 waveforms are applied, obtaining a maximum drag reduction rate and maximum energy saving rate of 38.6% and 31.4%, respectively. The results

A drag coefficient model for Lagrangian particle dynamics relevant to highspeed flows Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Raghava S.C. Davuluri, Sean C.C. Bailey, Kaveh A. Tagavi, Alexandre MartinAbstract A blended drag coefficient model is constructed using a series of empirical relations based on Reynolds number, Mach number, and Knudsen number. When validated against experiments, the drag coefficient model produces matching values with a standard deviation error of 2.84% and a maximum error of 11.87%. The model is used in a Lagrangian code which is coupled to a hypersonic aerothermodynamic

Determination of groove shape with strong destabilization and low hydraulic drag Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Nikesh Yadav, S.W. Gepner, J. SzumbarskiAbstract Flow through a channel equipped with plane, longitudinal grooves is investigated. We focus on determining changes to the flow dynamics due to applied wall manipulations, especially the possibility of dragreduction, potential for hydrodynamic destabilization and onset of secondary, nonlinear flow solutions. Considered patterns of geometrical manipulation consist of plane walled grooves of

The wake flow downstream of a propellerrudder system Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Antonio Posa, Riccardo Broglia, Elias BalarasAbstract We report wallresolved, largeeddy simulations for the case of a propeller operating upstream of a hydrofoil, mimicking a rudder. Our primary objective is the identification of wake features that are unique to this coupled system, when compared to openwater cases, which are usually the focus of experiments and computations in the literature. We were able to achieve unprecedented levels of

Linear control of coherent structures in wallbounded turbulence at Reτ=2000 Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Stephan F. Oehler, Simon J. IllingworthWe consider linear feedback flow control of the largest scales in an incompressible turbulent channel flow at a friction Reynolds number of $Re_\tau = 2000$. A linear model is formed by augmenting the NavierStokes equations with an eddy viscosity and linearizing it about the turbulent mean. Velocity perturbations are then generated by stochastically forcing the linear operator. The objective is to

Direct numerical simulation of turbulent flow separation induced by a forwardfacing step Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Xingjun Fang, Mark F. Tachie, Donald J. BergstromAbstract Direct numerical simulation is used to investigate turbulent flow separations generated by a forwardfacing step exposed to an incoming fullydeveloped turbulent plane channel flow at Re τ = 180 . The step height is 25% of the inlet channel height. The results are analyzed in terms of the topology of the Reynolds stresses, transport of turbulence kinetic energy (TKE) and unsteadiness of separation

Large eddy simulation of compressible round jets with coflow Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Parth Thaker, Somnath GhoshAbstract Large eddy simulations of subsonic round jets are carried out using high order compact finite difference scheme and an explicit filtering based approximate deconvolution method. The jets have a Mach number of 0.9 and Reynolds number of 4.5 × 10 5 based on jet diameter and centerline velocity at inflow. Results obtained for the mean flow and turbulence intensities agree well with those in existing

LES investigation on the dependence of the flow through a centrifugal pump on the diffuser geometry Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Antonio PosaAbstract LargeEddy Simulation is utilized to investigate the rotor–stator interaction within a centrifugal pump. Comparisons are presented across diffuser geometries for two values of the flowrate. Decreasing the incidence angle on the diffuser blades at offdesign is found the main source of higher pressure rise and lower overall values of turbulent kinetic energy within the pump, resulting in efficiency

On the onset of instability in the wake of superhydrophobic spheres Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210201
Marco Castagna, Nicolas Mazellier, Azeddine KourtaAbstract We report an experimental investigation of free falling superhydrophobic (SH) spheres in glycerinewater mixtures over a wide range of Reynolds number. SH coatings have the ability to reduce the contact area between the surrounding liquid and the solid surface by entrapping an air layer in the surface roughness. We investigate the effect of this air plastron on the hydrodynamic performance

Production and migration of turbulent kinetic energy in bluff body shear layers Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210123
D.M. Moore, M. AmitayAn experimental campaign on a bluff body of rectangular cross section, having a sidelength ratio of 5:1 was carried out using both particle image velocimetry and hot wire anemometry at a Reynolds number of 3.04×104. Results show that under a slight angle of attack, the development of unsteadiness in the form of turbulent kinetic energy is significantly amplified on the pressure side of the body. A

Flow development over isolated dropletinspired shapes Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210123
Xueqing Zhang, Burak A. Tuna, Serhiy Yarusevych, Sean D. PetersonFlow development over isolated, surfacemounted, dropletinspired threedimensional obstacles submerged in a laminar boundary layer is investigated at a Reynolds number based on obstacle height of Reh=2070 using particle image velocimetry. Three geometries are considered, a sessile droplet; a droplet on the verge of runback (depinning); and a spherical cap, which serves as a first order approximation

Impact of vacuum degree on the aerodynamics of a highspeed train capsule running in a tube Int. J. Heat Fluid Flow (IF 2.789) Pub Date : 20210120
Yang Sui, Jiqiang Niu, Pierre Ricco, Yanping Yuan, Qiujun Yu, Xiaoling Cao, Xiaofeng YangMotivated by the growing scientific and engineering interest in evacuated tube railway transportation systems, in this paper we numerically study the influence of the vacuum degree on the flow field around a train capsule running in an evacuated tube with circular section. The vacuum degree is increased by lowering the nominal pressure inside the tube. The numerical simulations are fully verified by