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The uniformmomentum zones and internal shear layers in turbulent pipe flows at Reynolds numbers up to Reτ=1000 Int. J. Heat Fluid Flow (IF 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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 2.073) 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

Production and migration of turbulent kinetic energy in bluff body shear layers Int. J. Heat Fluid Flow (IF 2.073) 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 2.073) 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 2.073) 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

Twophase cocurrent flow simulations using periodic boundary conditions in horizontal, 4, 10 and 90° inclined eccentric annulus, flow prediction using a modified interFoam solver and comparison with experimental results Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20210118
C. Friedemann, M. Mortensen, J. NossenTwophase oil and gas flow were simulated in an entirely eccentric annulus and compared with experimental data at horizontal, 4, 10, and 90° inclination. The gasphase was sulphur hexafluoride and the liquid phase a mixture of Exxsol D60 and Marcol 82 for the inclined cases (5–16), and pure Exxsol D60 for the horizontal cases (1–4). The diameter of the outer and inner cylinders was 0.1 and 0.04 m,

A hybrid immersed boundary/wallmodel approach for largeeddy simulation of highReynoldsnumber turbulent flows Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20210115
Ming Ma, WeiXi Huang, ChunXiao Xu, GuiXiang CuiWe propose an improved hybrid immersed boundary (IB)/wallmodel approach for highReynoldsnumber largeeddy simulations (LES). A preliminary test shows that the existing model that modifies subgrid viscosity based on the mixinglength model leads to deviation of the wall shear stress when implemented at high Reynolds numbers. To correct the deviation of the wall shear stress at high Reynolds numbers

Datadriven feature identification and sparse representation of turbulent flows Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20210112
Mohammad BeitSadi, Jakub Krol, Andrew WynnIdentifying coherent structures in fluid flows is of great importance for reduced order modelling and flow control. However, extracting such structures from experimental or numerical data obtained from a turbulent flow can be challenging. A number of modal decomposition algorithms have been proposed in recent years which decompose timeresolved snapshots of data into spatial modes, each associated

Nonequilibrium wall functions for large Eddy simulations of complex turbulent flows and heat transfer Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20210111
Yongxiang Li, Florian Ries, Wibke Leudesdorff, Kaushal Nishad, Andrea Pati, Christian Hasse, Johannes Janicka, Suad Jakirlić, Amsini SadikiIn this paper novel unified wall function formulations for large eddy simulation of complex turbulent flows and heat transfer are presented. In contrast to existing wall functions, the proposed analytical expressions for velocity and temperature are: (1) valid over the whole range of dimensionless wall distance y+, (2) applicable to complex flow situations that include local nonequilibrium effects

Wake dynamics and heuristic modelling in the desynchronization region of 1DOF VIV Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20210111
Christopher M. O’Neill, Graham Riches, Chris MortonVortexinduced vibrations of a circular cylinder has been investigated experimentally using a cyberphysical apparatus with m∗=8 and ζ=0.005. The Reynolds number is held fixed at Re=4000, with the reduced velocity being modified via a change in the structural natural frequency in a cyberphysical controller. The study focus is on a detailed analysis of the wake dynamics in the desynchronization region

Investigation of mixing processes of effusion cooling air and main flow in a single sector model gas turbine combustor at elevated pressure Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20210106
Max Greifenstein, Andreas Dreizler 
Swirling turbulent pipe flows: Inertial region and velocity–vorticity correlations Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201230
Rey C. Chin, Jimmy PhilipSwirling pipe flows are studied here with an aim towards understanding the onset of the inertial region — where the turbulentinertia term in the mean momentum equation is balanced by pressure gradient and viscous term is subdominant — as well as the clarifying the velocity–vorticity correlations that make up the turbulent inertia. To this end, we first manipulate the mean momentum equation in both

Wall modeling of turbulent methane/oxygen reacting flows for predicting heat transfer Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201226
Daiki Muto, Yu Daimon, Hideyo Negishi, Taro ShimizuThis paper presents a wall modeling study of turbulent reacting flows of CH4/O2 mixtures towards accurately predicting the wall heat flux in combustion chambers. The study focuses on the description of flow and chemistry within inner layers and compares the accuracy of wall functions and ordinary differential equation (ODE) based wall models assuming equilibrium and frozen chemistry. Two test cases

Heat transfer and fluid flow characteristics of a turbulent wall jet with a wavy wall Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201226
Archana Kumari, Amitesh KumarThe fluid flow and heat transfer characteristics of a turbulent wavy wall jet have been studied numerically using the low Reynolds number model. The three low Reynolds number models, Realizable, RNG and SST are used for code validation with the experimental results present in the literature for the plane wall jet. The best suited model is used further to study the wavy wall jet. The sinusoidal profile

Experimental investigation of turbulent flow characteristics in crossflow planes of a 5×5 rod bundle with a spacer grid Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201226
Camila F. Matozinhos, Gabriel C.Q. Tomaz, Thien Nguyen, Yassin HassanThis study summarizes experimental investigations of the flow field characteristics in the crossflow planes of a 5×5 rod bundle with spacer grid and splittype mixing vanes. Under the isothermal and atmospheric conditions, the velocity fields in the crossflow planes are obtained by applying the matchedindexofrefraction and timeresolved particle image velocimetry (TRPIV) techniques for Reynolds

Columnar heat transport via advection induced by inertial waves Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201224
A. Ranjan, P.A. DavidsonInertial waves are oscillations in a rotating fluid that arise due to the restoring action of the Coriolis force. Lowfrequency inertial waves are known to create columnar flow structures inrapidly rotating systems. Columnar heat transport away from the equator has been observed in some strongly forced, rapidlyrotating geodynamo simulations of the Earth’s core. In this study, we investigate the mechanism

A drag coefficient model for Lagrangian particle dynamics relevant to highspeed flows Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201217
Raghava S.C. Davuluri, Sean C.C. Bailey, Kaveh A. Tagavi, Alexandre MartinA 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 CFD code

Determination of groove shape with strong destabilization and low hydraulic drag Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201217
Nikesh Yadav, S.W. Gepner, J. SzumbarskiFlow 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 triangular

The wake flow downstream of a propellerrudder system Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201217
Antonio Posa, Riccardo Broglia, Elias BalarasWe 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 numerical

Linear control of coherent structures in wallbounded turbulence at Reτ=2000 Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201215
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 Reτ=2000. A linear model is formed by linearizing the Navier–Stokes equations about the turbulent mean and augmenting it with an eddy viscosity. Velocity perturbations are then generated by stochastically forcing the linear operator. The objective is to reduce

Direct numerical simulation of turbulent flow separation induced by a forwardfacing step Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201213
Xingjun Fang, Mark F. Tachie, Donald J. BergstromDirect numerical simulation is used to investigate turbulent flow separations generated by a forwardfacing step exposed to an incoming fullydeveloped turbulent plane channel flow at Reτ=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 bubbles

Large eddy simulation of compressible round jets with coflow Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201211
Parth Thaker, Somnath GhoshLarge 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 4.5×105 based on jet diameter and centerline velocity at inflow. Results obtained for the mean flow and turbulence intensities agree well with those in existing literature

LES investigation on the dependence of the flow through a centrifugal pump on the diffuser geometry Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201204
Antonio PosaLargeEddy 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 2.073) Pub Date : 20201203
Marco Castagna, Nicolas Mazellier, Azeddine KourtaWe 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 of spheres

Wall shear stress modified by bubbles in a horizontal channel flow of silicone oil in the transition region Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201121
Yoshihiko Oishi, Yuichi Murai, Yuji TasakaWe performed laboratory experiments on bubbly channel flows using silicone oil, which has a low surface tension and clean interface to bubbles, as a test fluid to evaluate the wall shear stress modification for different regimes of bubble migration status. The channel Reynolds numbers of the flow ranged from 1000 to 5000, covering laminar, transition and turbulent flow regimes. The bubble deformation

A methodology for coupling DNS and discretised population balance for modelling turbulent precipitation Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201119
Hin Yan Tang, Stelios Rigopoulos, George PapadakisIn this paper, we present a methodology for simulating nanoparticle formation in a turbulent flow by coupling Direct Numerical Simulation (DNS) and population balance modelling. The population balance equation (PBE) is solved via a discretisation method employing a composite grid that provides sufficient detail over the wide range of particle sizes reached during the precipitation process. The coupled

Global stability analysis of a 90°bend pipe flow Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201118
Valerio Lupi, Jacopo Canton, Philipp SchlatterThe present work investigates the stability properties of the flow in a 90°bend pipe with curvature δ=R/Rc=1/3, with R being the radius of the crosssection of the pipe and Rc the radius of curvature at the pipe centreline. Direct numerical simulations (DNS) for values of the bulk Reynolds number Reb=UbD/ν between 2000 and 3000 are performed. The bulk Reynolds number is based on the bulk velocity

Some new characteristics of the confined flow over circular cylinders at low reynolds numbers Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201116
A. Ooi, L. Chan, D. Aljubaili, C. Mamon, J.S. Leontini, A. Skvortsov, P. Mathupriya, H. HasiniThis study summarises some new characteristics of the fluid flow over a confined circular cylinder at low Reynolds numbers. Results from both two and threedimensional direct numerical simulations are presented at blockage ratio between 0.1 and 0.9 and Reynolds number between 120 and 500. Floquet stability analysis of selected cases will also be presented. From the twodimensional simulations, it

Lagrangian interpolation algorithm for PIV data Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201116
Maegan Vocke, Conrad Bingham, Graham Riches, Robert Martinuzzi, Chris MortonA new Lagrangian based interpolation scheme is proposed for recovering velocity field data from within masked regions in particle image velocimetry (PIV) experiments. As a first step, the mean field within the masked region is filled through an iterative convolution operation using an optimized kernel. Next, the Lagrangian interpolation scheme estimates velocity field data within the masked region

Experimental investigation of nosetip bluntness effects on the hypersonic crossflow instability over a cone Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201116
Haibo Niu, Shihe Yi, Xiaolin Liu, Junjie Huo, Long JinThe nosetip bluntness effects on the hypersonic crossflow instability were experimentally investigated over a 7∘ halfangle straight cone at 6∘ angle of attack. The experiments were conducted in a Mach 6 wind tunnel at Reynolds number of 7.94×106 m−1 using temperaturesensitive paint (TSP) and fastresponse pressure transducers. The wavelet transform was applied to obtain the most amplified wavenumber

An experimental study on boundary layer transition detection over a pitching supercritical airfoil using hotfilm sensors Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201116
Arshia Tabrizian, Massoud Tatar, Mehran Masdari, Hamidreza Eivazi, Mehdi SeddighiIn the present work, experimental tests are conducted to study boundary layer transition over a supercritical airfoil undergoing pitch oscillations using hotfilm sensors. Tests have been undertaken at an incompressible flow. Three reduced frequencies of oscillations and two mean angles of attack are studied and the influences of those parameters on transition location are discussed. Different algorithms

A mesoscopic modelling approach for direct numerical simulations of transition to turbulence in hypersonic flow with transpiration cooling Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201109
Adriano Cerminara, Ralf Deiterding, Neil SandhamA rescaling methodology is developed for highfidelity, costefficient direct numerical simulations (DNS) of flow through porous media, modelled at mesoscopic scale, in a hypersonic freestream. The simulations consider a Mach 5 hypersonic flow over a flat plate with coolant injection from a porous layer with 42 % porosity. The porous layer is designed using a configuration studied in the literature

Effects of buoyancy and thermophysical property variations on the flow of supercritical carbon dioxide Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201101
Jundi He, Junjie Yan, Wei Wang, Peixue Jiang, Shuisheng HeThe flow and heat transfer behaviours of fluids at supercritical pressure have been studied using direct numerical simulations (DNS), in which one or more thermal properties are artificially frozen to discern the various physical mechanisms from each other so as to better understand the complex phenomena. Different from previous similar studies on this topic, this study focuses on the axial flow development

Turbulent transport dissimilarity with modulated turbulence structure in channel flow of viscoelastic fluid Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201019
Shumpei Hara, Takahiro Tsukahara, Yasuo KawaguchiThis experimental study investigated the turbulent transport dissimilarity with a modulated turbulence structure in a channel flow of a viscoelastic fluid using simultaneous particle image velocimetry and planar laserinduced fluorescence measurements. An instantaneous dye concentration field with fluctuating velocity vectors showed that mass was transferred by hierarchically largescale wavy motions

Flow physics of normal and abnormal bioprosthetic aortic valves Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201022
JungHee Seo, Chi Zhu, Jon Resar, Rajat MittalFlow physics of transvalvular flows in the aorta with bioprosthetic valves are investigated using computational modelling. For the efficient simulations of flowstructureinteraction in transvalvular flows, a simplified, reduced degree of freedom valve model is employed with a sharp interface immersed boundary based incompressible flow solver. Simulations are performed for normal as well as abnormal