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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

Resolventbased design and experimental testing of porous materials for passive turbulence control Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201029
Andrew Chavarin; Christoph Efstathiou; Shilpa Vijay; Mitul LuharAn extended version of the resolvent formulation is used to evaluate the use of anisotropic porous materials as passive flow control devices for turbulent channel flow. The effect of these porous substrates is introduced into the governing equations via a generalized version of Darcy’s law. Model predictions show that materials with high streamwise permeability and low wallnormal permeability (ϕxy=kxx/kyy≫1)

Leading edge vortex formation and detachment on a flat plate undergoing simultaneous pitching and plunging motion: Experimental and computational study Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201029
Johannes Kissing; Sebastian Wegt; Suad Jakirlic; Jochen Kriegseis; Jeanette Hussong; Cameron TropeaThis study focuses on the formation and detachment of a leading edge vortex (LEV) appearing on an airfoil when its effective angle of attack is dynamically changed, inducing additional forces and moments on the airfoil. Experimental measurements of the timeresolved velocity field using Particle Image Velocimetry (PIV) are complemented by a computational study using an URANS (Unsteady ReynoldsAveraged

Flow dynamics in the short asymmetric TaylorCouette cavities at low Reynolds numbers Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201019
E. TuliszkaSznitkoThis paper reports on the numerical investigations of TaylorCouette flow of radius ratio η = 0.25–0.6 performed at low Reynolds numbers Re = 100–200. The inner cylinder and the bottom endwall rotate, while the outer cylinder and the top endwall are held fixed. A fully 3D DNS code based on the spectral Chebyshev – Fourier approximation is used. This study is complementary to those of Mullin and Blohm

Aerodynamic drag improvements on a squareback vehicle at yaw using a tapered cavity and asymmetric flaps Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201026
Magnus Urquhart; Max Varney; Simone Sebben; Martin PassmoreEmissions of greenhouse gasses from passenger vehicles is a concern globally. One of the factors that influence the vehicles energy consumption is the aerodynamic drag, continuing to be an active topic of interest. This work investigates the vehicle wake in relation to aerodynamic drag in steady crosswind conditions. The vehicle used is a modified version of the generic Windsor geometry with wheels

Hairpin vortices in the largest scale of turbulent boundary layers Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201016
Yutaro Motoori; Susumu GotoWe have conducted direct numerical simulations of a turbulent boundary layer for the momentumthicknessbased Reynolds number Reθ = 180–4600. To extract the largestscale vortices, we coarsegrain the fluctuating velocity fields by using a Gaussian filter with the filter width comparable to the boundary layer thickness. Most of the largestscale vortices identified by isosurfaces of the second invariant

Inputoutput reducedorder modeling of unsteady flow over an airfoil at a high angle of attack based on dynamic mode decomposition with control Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201017
Chong Sun; Tian Tian; Xiaocheng Zhu; Zhaohui DuDue to the damage caused by stall flutter, the investigation and modeling of the flow over a wind turbine airfoil at high angles of attack are essential. Dynamic mode decomposition (DMD) and dynamic mode decomposition with control (DMDc) are used to analyze unsteady flow and identify the intrinsic dynamics. The DMDc algorithm is found to have an identification problem when the spatial dimension of

Effects of radius ratio on turbulent concentric annular pipe flow and structures Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201014
Edris Bagheri; BingChen WangThe effects of radius ratio on fullydeveloped turbulent concentric annular pipe flow and structures are investigated using direct numerical simulations (DNS). In order to study the radius ratio effects on the flow, four radius ratios of a concentric annular pipe (for Ri∕Ro=0.1–0.7) are compared at a fixed Reynolds number. Here, Ri and Ro are the radii of the inner and outer pipes, respectively. It

Experimental validation of a two equation RANS transitional turbulence model for compressible microflows Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201014
Danish Rehman; Gian Luca MoriniLaminartoturbulent flow transition in microchannels can be useful to enhance mixing and heat transfer in microsystems. Typically, the small characteristic dimensions of these devices hinder in attaining higher Reynolds numbers to limit the total pressure drop. This is true especially in the presence of a liquid as a working medium. On the contrary, due to lower density, Reynolds number larger than

NonDarcian Bénard convection in eccentric annuli containing spherical particles Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201013
Gazy F. AlSumaily; Hasanen M. Hussen; Wissam H. Alawee; Hayder A. Dhahad; Mark C. ThompsonIn this paper, a numerical investigation of natural convection in a porous medium confined by two horizontal eccentric cylinders is presented. The cylinders are impermeable to fluid motion and retained at uniform different temperatures. While, the annular porous layer is packed with glass spheres and fullysaturated with air, and the cylindrical packed bed is under the condition of local thermal nonequilibrium

Energybased decomposition of friction drag in turbulent squareduct flows Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201013
Yitong Fan; Weipeng Li; Sergio PirozzoliThe generation of friction drag in turbulent duct flows has direct connection with statistical quantities and corresponding turbulence dynamics in the duct crosssection. In this study, we generalize the RD identity (Renard and Deck, 2016) to a ‘twodimensional’ form which we exploit to decompose the mean friction drag in turbulent squareduct flows into contributions associated with viscosity, turbulence

A numerical study of a rectangular jet along a shear free boundary: Surface jet Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201010
Iftekhar Z. Naqavi; Paul G. Tucker; Eric Savory; Robert J. MartinuzziA numerical simulation of a rectangular surface jet is performed at a Reynolds number of Rej=4400. The global parameters of the jet e.g. maximum velocity decay, jet surface normal and lateral spread rates, entrainment, jet momentum flux and turbulent momentum flux are in agreement with several other studies reported in the literature. It is shown that the mean velocity and Reynolds stress profiles

Turbulence structure in nonequilibrium boundary layers with favorable and adverse pressure gradients Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201008
Ralph J. VolinoAn experimental study was conducted to document the turbulence in boundary layers on smooth walls subject to a favorable pressure gradient followed by a zero pressure gradient recovery and an adverse pressure gradient. Two component velocity profiles were acquired along the spanwise centerline of the test section, and velocity fields were obtained at the same locations in streamwise wallnormal and

Effect of surface topology on the galloping instability of rectangular cylinders Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20201006
Mark A. Feero; Ahmed M. Naguib; Manoochehr M. KoochesfahaniThe effect of geometry on the transverse galloping instability of rectangular cylinders was studied experimentally for Reynolds numbers between 1,000 and 10,000. In particular, a comparison was made between a rectangular cylinder with rounded corners and a smooth surface, and the same baseline geometry with added surface topology synthesized from twodimensional Fouriermodes. The effects of the topology

Aerofoil dipole noise due to flow separation and stall at a low Reynolds number Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200930
Jacob M. Turner; Jae Wook KimAerofoil selfnoise produced by flow separation and stall is relatively little understood regarding the underlying generation mechanisms. The focus of this work is to provide an improved level of understanding particularly with regard to the dipole noise sources utilising a highfidelity direct numerical simulation. A NACA0012 aerofoil is considered under three different flow conditions at a Reynolds

Experimental and numerical study on flow characteristics and heat transfer of an oscillating jet in a channel Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200928
Shabnam Mohammadshahi; Hadi SamsamKhayani; Tao Cai; Kyung Chun KimA fluidic oscillator can produce selfinduced and selfsustaining oscillating jet by fluid supply without moving parts. This device has attracted research interest in heat and mass transfer enhancement in recent years. In the current study, a doublefeedback fluidic oscillator was numerically investigated based on threedimensional unsteady Reynoldsaveraged NavierStokes equations (3DURANS) while

Effects of planar and nonplanar curved flow paths on the hemodynamics of helical conduits for coronary artery bypass grafting: A numerical study Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200929
Foo Kok; Roy Myose; Klaus A. HoffmannHelical geometries to induce swirling and spiral flow in prosthetic grafts have been hypothesized as a possible way to improve the clinical outcomes in patients undergoing coronary artery bypass grafting. In this paper, the transient flow behavior in helical bypass conduits with two different curved flow paths (planar and nonplanar) was investigated. Numerical methods were used to examine the flow

On the relationship between drag and vertical velocity fluctuations in flow over riblets and liquid infused surfaces Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200926
Simone Di Giorgio; Stefano Leonardi; Sergio Pirozzoli; Paolo OrlandiDirect numerical simulations (DNS) of flow over triangular and rectangular riblets in a wide range of size and Reynolds number have been carried out. The flow within the grooves is directly resolved by exploiting the immersedboundary method. It is found that the drag reduction property is primarily associated with the capability of inhibiting vertical velocity fluctuations at the plane of the crests

Timeaveraged flow characteristics and mixing properties of doubleconcentric jets Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200925
Sudharson Murugan; Rong Fung Huang; Ching Min HsuWe examined the flow behaviors and mixing characteristics of doubleconcentric jets using laserassisted smoke flow visualization method to analyze typical flow patterns and binary boundary detection technique to investigate jet spread width. Timeaveraged velocity vectors, streamline patterns, velocity distributions, turbulence properties, and vorticity contours were analyzed using Particle Image

Effect of pressure gradients on the different stages of roughness induced boundary layer transition Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200924
Saikishan Suryanarayanan; David B. Goldstein; Alexandre R. Berger; Edward B. White; Garry L. BrownThe physical mechanisms of roughnessinduced transition (RIT) in pressure gradient boundary layers are studied using direct numerical simulations. Recent investigations have examined RIT processes in zeropressuregradient boundary layers (Suryanarayanan et al., 2019). The present study uses a vorticity dynamics point of view to examine how these processes are altered by a locally accelerating or decelerating

The turbulent/nonturbulent interface in an adverse pressure gradient turbulent boundary layer Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200922
Jongmin Yang; Min Yoon; Hyung Jin SungThe turbulent/nonturbulent interface (TNTI) in an adverse pressure gradient (APG, β = 1.45) turbulent boundary layer (TBL) is explored here by using direct numerical simulation (DNS) data; β is the Clauser pressure gradient parameter. For comparison, the DNS data for a zero pressure gradient (ZPG) TBL is included. The interface is extracted with an approach based on enstrophy criteria. Depending on

End effects of nominally twodimensional thin flat plates Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200924
Eric Braun; Kaden Agrey; Robert J. MartinuzziDifferences in the structure and dynamics of nominally twodimensional turbulent wakes are investigated experimentally for a thin flat plate, normal to a uniform flow, with two different end conditions: with and without end plates. Both cases are characterized by Karmanlike vortex shedding with broadband low frequency unsteadiness. Both wakes evidence a low frequency flapping motion in addition to

A hybrid dynamic Smagorinsky model for large eddy simulation Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200924
Qingxiang Shui; Cuie Duan; Xinyi Wu; Yunwei Zhang; Xilian Luo; Chao Hong; Yuanping He; Nyuk Hien Wong; Zhaolin GuA hybrid dynamic subgridscale model (HDSM) pertaining to Largeeddy simulation (LES) has been developed. The coefficient obtained by German dynamic Smagorinsky model (DSM) was integrated with a new dynamic coefficient, based on the dynamic subgrid characteristic length and controlled by the subgridscale (SGS) motions. In HDSM, the characteristic wave number determining the characteristic length of

On the cylinder wake subjected to inphase and outofphase periodic forcing Int. J. Heat Fluid Flow (IF 2.073) Pub Date : 20200922
Anwar Ahmed; Samik Bhattacharya; Hamza Ahmed; Michael H. MooreExperiments were conducted in a wind tunnel to investigate the effect of periodic forcing on the wake of a circular cylinder specially designed for independent control of the phase of forcing from slits located on opposite sides. Tests were conducted at Reynolds number (Re) of 12,000, based on diameter (D). Wake was forced at subharmonic and harmonic frequencies at constant blowing coefficient. Measurements