Laminar Jet Flow Research Articles

Experimental Investigation of the Impacts of Laminar and Turbulent Impinging Jet Flows on the Convective Heat Transfer in a Metal Plate

Experimental Investigation of the Impacts of Laminar and Turbulent Impinging Jet Flows on the Convective Heat Transfer in a Metal Plate

Viscous fluid flow and heat transfer past a permeable wall jet with convective boundary conditions

PurposeThe steady laminar wall jet flow over a stretching/shrinking surface in the presence of lateral suction or injection with a convective boundary condition is considered.Design/methodology/approachThe partial differential equations for mass, momentum and energy conservation are changed to the system of ordinary differential equations through similarity solution transformations. Solutions, both numerical and asymptotic, to these similarity equations are found in some new ranges of parameters in the governing equations.FindingsThe equations are solved both asymptotically and numerically for a range of the transpiration parameter S and the flow parameter λ given in Mahros et al. (2023), thus greatly extending the range of these previous solutions. Asymptotic solutions for both large and small values of the Prandtl number σ are derived, showing good agreement with additional numerical integrations. It should be noted that in Mahros et al. (2023), only the case when σ=1 was treated. A solution for large λ when S=1 is obtained, showing a different asymptotic form to the case when S>0 in Mahros et al. (2023). Multiple solutions were seen by them for S<0 and the nature of the lower solution branch as S→0 from below is discussed. The question as to whether the lower branch solutions join as λ>0 when S<0 is resolved through obtaining an asymptotic solution λ small.Originality/valueThe accuracy of the solutions has been checked through a detailed comparison between the solutions obtained numerically and analytically, where excellent agreement has been found. This study is important for scientists working in the area of jet flows to become familiar with the flow properties and behaviour of jets.

Heat and mass transfer analysis of a Maxwell-power-law fluid in a laminar planar jet flow with Cattaneo–Christov double diffusion theory

This paper focuses on the heat and mass transfer characteristics of a steady laminar planar jet flow of a Maxwell-power-law (MPL) fluid. MPL is a renowned fluid model with shear thinning and viscoelastic characteristics that can accurately exhibit the rheological features of polymer liquids. In the envisioned study, the MPL constitutive equation is introduced based on an experiment utilizing the Xanthan gum solution. The heat and mass equations are supported by the Cattaneo–Christov double diffusion (CCDD) concept with unique characteristics of thermal conductivity, mass diffusion, and chemical reaction. Thermal conductivity and mass diffusion coefficient are considered to be velocity gradient-dependent. The problem is addressed numerically by the bvp4c method in Matlab after applying the similarity transformations to the governing equations. The impacts of related parameters on velocity, temperature, and concentration are analyzed. Results show that an upsurge in the power-law index hinders momentum, energy, and mass transmission. An interesting phenomenon is that the variation in relaxation time can hinder or promote the heat and mass transfer of a Maxwell-power-law fluid jet before or after the intersection point, respectively. The study can provide a theoretical reference for engineering applications of jets.

Exact solutions for permeable wall laminar jet with velocity slip: Momentum and thermal profiles

This study presents exact analytical solutions for the two-dimensional laminar jet flow and heat transport of Casson fluid under velocity slip condition. The laminar wall jet of classical Glauert type is extended to the Casson fluid model considering the flow to be along a flat permeable surface. The roles of velocity slip, wall temperature, and mass transfer on the fluid flow and rate of thermal exchange are investigated. The outcomes for momentum and thermal fields, skin friction and heat transfer gradient are obtained analytically with numerical solutions of the suction-far stream velocity expression. It is noted that mass transfer and velocity slip have significant effects on the flow of fluid and heat transfer. Thermal profile varies significantly for increasing Prandtl values with small suction.

Wall laminar nanofluid jet flow and heat transfer

PurposeThis work aims to investigates exact solutions of the classical Glauert’s laminar wall jet mass and heat transfer under wall suction, wall contraction or dilation, and two thermal transport boundary conditions; prescribed constant surface temperature and prescribed constant surface flux in nanofluidic environment.Design/methodology/approachThe flow system arranged in terms of partial dif- ferential equations is non-dimensionalized with suitable dimensionless transformation variables, and this new set of equations is reduced into ordinary differential equations via a set of similarity transformations, where they are treated analytically for closed form solutions.FindingsExact solutions of nanofluid flow for velocity distributions, momentum flux, wall shear stress and heat transfer boundary layers for commonly studied nanoparticles; namely copper, alumina, silver, and titanium oxide are presented. The flow behavior of alumina and titanium oxide is identical, and a similar behavior is seen for copper and silver, making two pairs of identical traits. The mathematical expressions as well as visual analysis of wall shear drag and temperature gradient which are of practical interest are analyzed. It is shown that wall stretching or shrinking, wall transpiration and velocity slip together influences the jet flow mechanism and extends the original Glauert’s jet solutions. The exact solutions for the two temperature boundary layer conditions and temperature gradients are analyzed analytically. It is found that the effect of nanopar- ticles concentration on thermal boundary layer is intense, causing temperature uplift, whereas the wall transpiration causes a decrease in thermal layers.Originality/valueThe analysis carried out in nanofluid environment is genuinely new and unique, as our work generalizes the Glauert’s classical regular wall jet fluid problem.

Bioconvection in radiative Glauert wall jet flow of nanofluid: a Buongiorno model

The wall jet flow is obtained by leading a free jet to flow in an area of a surface normally. In the presence of microorganisms, particularly gyrotactic-type organisms, the suspension becomes very efficient due to their capabilities and the dilution of nanoparticles in base liquids. The scientific community, particularly those working in the fields of biomedical devices, biomicrosystems and biotechnology, bioconvection has taken notice of these characteristics. Numerous industrial procedures encompass convection based on bioconvection and motile density. In the present study, a laminar Glauert wall jet flow in the presence of bioconvection, slip and suction is investigated by using the Buongiorno model. The governing equations that state the flow problem are converted into ordinary differential equations (ODEs) by applying Glauert transformations. The ODEs are solved numerically by applying fourth fifth order of Runge–Kutta–Fehlberg (RKF-45) scheme along with the shooting method. The noteworthy results of the current study are that the rise in values of Brownian motion, radiation, and thermophoresis parameters enhances the thermal profile. The increase in values of concentration difference and bioconvection Peclet numbers decays the microorganism profile. The rate of heat transfer declines for rise in values of thermophoresis parameter and inclines for higher values of radiation parameter.

Experiments on the nonlinear interaction of crossed turbulent streaming jets: A case study in mentorship

During (2017–2018) co-author JMC began a mentorship at USNA as a HS senior. Projects led to developing an apparatus to study the interaction between crossed turbulent streaming jets in water. The ISNA 21 (Santa Fe) was an opportunity to present this research – which included a live demonstration. See [Proc. Mtgs. Acoust. 34, 045022 (2018)]. Majoring in material science at JHU, JMC worked as a college intern at USNA (during 4 summers) to further develop the turbulent streaming jets experiment which now included a LaVision 2-D PIV (particle imaging velocimeter). Home-made MOSFET power amplifiers, Langevin 28 kHz ultrasonic transducers and aluminum stepped horns, were replaced by kits developed by Sonics &amp; Materials. The kits including 40-kHz oscillators, 20 Watt amplifiers, impedance matching to the 40 kHz transducers CV245 and titanium 1/2, 1/4 and 1/8 inch diameter stepped horns Part # 630-0594 – to generate stronger downward East and West crossed turbulent jets (at a 60 deg angle) in an open 10 cc acrylic tank. As a by-product, cavitation bubbles allow flow visualization. Lighthill’s nonlinear theory of acoustic streaming (1978) for a single source will be discussed including “Stuart streaming,” Reichardt and Schlicting’s (turbulent jets) and Squire’s theory on nonlinear laminar jet flow.

Heat Transfer via Laminar Jet Flow from Upward-facing Triple-pipe System onto Hot Moving Thin Steel Sheet

Heat Transfer via Laminar Jet Flow from Upward-facing Triple-pipe System onto Hot Moving Thin Steel Sheet

The Okubo–Weiss criterion in hydrodynamic flows: geometric aspects and further extension

The Okubo (1970 Deep Sea Res. 17 445)–Weiss (1991 Physica D 48 273) criterion, has been extensively used as a diagnostic tool to divide a two-dimensional (2D) hydrodynamical flow field into hyperbolic and elliptic regions and to serve as a useful qualitative guide to the complex quantitative criteria. The Okubo–Weiss criterion is frequently validated on empirical grounds by the results ensuing its application. So, we will explore topological implications into the Okubo–Weiss criterion and show the Okubo–Weiss parameter is, to within a positive multiplicative factor, the negative of the Gaussian curvature of the vorticity manifold. The Okubo–Weiss criterion is then reformulated in polar coordinates, and is validated for several examples including the Lamb–Oseen vortex, and the Burgers vortex. These developments are then extended to 2D quasi-geostrophic (QG) flows. The Okubo–Weiss parameter is shown to remain robust under the β-plane approximation to the Coriolis parameter. The Okubo–Weiss criterion is shown to be able to separate the 2D flow-field into coherent elliptic structures and hyperbolic flow configurations very well via numerical simulations of quasi-stationary vortices in QG flows. An Okubo–Weiss type criterion is formulate for 3D axisymmetric slows, and is validated via application to the round Landau–Squire Laminar jet flow.

Demonstration of nonlinear interaction of crossed turbulent streaming jets

An experimental apparatus was built for demonstration purposes involving two mutually perpendicular crossed ultrasonic turbulent streaming jets in water. A 2D Particle Imaging Velocimeter (LaVision) measured the turbulent flow generated by their interaction. Experiments were performed in an open 10 cc acrylic water tank. The apparatus consisted of two Langevin ultrasonic transducers—both equipped with stepped horns with section diameters: 1/2, 1/4 and 1/8 in.2. A kit developed by Sonics and Materials included a 40-kHz oscillator driving a 20 W amplifier (impedance matched to the 40 kHz transducer CV245) and stepped horn (Part # 630-0594). Two such units were needed to generate the crossed ultrasonic turbulent streaming jets. In the viewing plane the axes of each streaming jet was—i cos30—j sin30, + i cos30—j sin30, respectively. The horn tips (1/8 inch) (slightly submerged in the water) also generated small cavitation bubbles. Lighthill’s theory of acoustic streaming (1978) for a single source will be discussed. Lighthill recognized the importance of “Stuart streaming,” Reichardt’s turbulent jet measurements, Schlicting’s turbulent jet theory (involving eddy viscosity) and Squire’s exact solution for a nonlinear laminar jet flow. Earlier, Lighthill predicted that a turbulent jet would generate aerodynamic sound.

Control of a Round Jet Intermittency and Transition to Turbulence by Means of an Annular Synthetic Jet

This paper deals with active control of a continuous jet issuing from a long pipe nozzle by means of a concentrically placed annular synthetic jet. The experiments in air cover regimes of laminar, transitional, and turbulent main jet flows (Reynolds number ranges 1082–5181). The velocity profiles (time-mean and fluctuation components) of unforced and forced jets were measured using hot-wire anemometry. Six flow regimes are distinguished, and their parameter map is proposed. The possibility of turbulence reduction by forcing in transitional jets is demonstrated, and the maximal effect is revealed at Re = 2555, where the ratio of the turbulence intensities of the forced and unforced jets is decreased up to 0.45.

The effects of thermal boundary conditions on the heat transfer characteristics of laminar flow in milli-scale confined impinging slot jets

This study experimentally investigated the effects of thermal boundary conditions on the laminar heat transfer characteristics of milli-scale, confined slot jets with flat, convex, and concave surfaces. We explored two thermal boundary conditions at the impinging surface: uniform heat flux and uniform wall temperature. The Reynolds number (Re) ranges from 120 to 600, the dimensionless nozzle-to-surface distance (H/B) from 2 to 10, and the dimensionless curved surface diameter-to-nozzle width (D/B) is 90. The results show that near the stagnation region, local Nusselt numbers for all three surfaces increase at each x/B location as H/B changes from 10 to 2 regardless of thermal boundary condition. In the wall jet region, However, in the wall jet region the uniform heat flux condition produces higher Nusselt numbers than the uniform wall temperature. As a result, local Nusselt numbers for both thermal boundary conditions show cross-over regions at x/B=1-5 where the dependence of local Nusselt number on H/B changes, depending upon the x/B location. These behaviors illustrate the sensitivity of Nusselt numbers for laminar boundary layer and laminar slot jet flows to thermal boundary condition. Empirical correlations for both stagnation and local Nusselt numbers with a concave surface are in an agreement with the experimental results to within ±15%.

Application of shear-thinning and shear-thickening fluids to computational fluid mechanics of high-Reynolds impinging turbulent jets for cooling engineering

In the present paper a numerical study on the heat transfer from a heated flat plate to a shear-thinning/shear-thickening high-Reynolds impinging jet is developed. Only laminar jet flows have been considered in the literature to date for this type of application. This investigation is focused on the study of the impact of nozzle-to-plate distance, generation of swirl and Power Law flow index in the quantities of interest for heat transfer. It has been found that the cooling of the plate is highly influenced by the shear-thinning and shear-thickening behaviour of the working fluid. The most relevant conclusion is that surface-averaged heat transfer is enhanced by a shear-thinning fluid, but the cooling at the stagnation point is enhanced by a shear-thickening fluid. Mathematical correlations are also provided based on the training data generated in the present investigation. Surprisingly, there are no engineering applications nor studies using high-Reynolds non-Newtonian jet flows yet, so this novel numerical investigation intends to show the advantages/drawbacks of several configurations.

Symmetry breaking in annular jets with different blockage ratio

We perform direct numerical simulations of the annular laminar jet flows for two inner-to-outer diameter (blockage) ratios br = d / D = 0.5, 0.9 in the range of the Reynolds number based on the bulk velocity inside the nozzle and its outer diameter Re = 200 – 400. In spite of the axisymmetric formulation, asymmetric states are observed for moderate and high Re. A gradual increase of the Reynolds number allow building a regime map. The symmetry-asymmetry transition Reynolds number decreases with the increase of br, while the steady-unsteady transition Reynolds numbers are close for both br. The degree of asymmetry increases with the increase of Re, leading to a shift of the global stagnation point from the axis of symmetry.

Corrigendum to "Local similarity solution for steady laminar planar jet flow of viscoelastic FENE-P fluids" [Journal of Non-Newtonian Fluid Mechanics 279 (2020) 104265

Corrigendum to "Local similarity solution for steady laminar planar jet flow of viscoelastic FENE-P fluids" [Journal of Non-Newtonian Fluid Mechanics 279 (2020) 104265

Local similarity solution for steady laminar planar jet flow of viscoelastic FENE-P fluids

Three local self-similar solutions are obtained for the laminar planar jet flow of viscoelastic fluids, described by the FENE-P constitutive equation, through an order of magnitude simplification of the governing equations. The more general solution is shown to be more accurate than two further simplified solutions, here called the delta and the Olagunju-type solutions, at least for the profiles of conformation tensor components. In the limit of vanishing viscoelasticity, all conformation tensor components reduce to the same low elasticity asymptotic behavior, and the polymer stresses become Newtonian-like. The general solution is then used to obtain the laws of the decay of the centerline velocity and of the growth of the jet half-width and to ascertain the effects of the Weissenberg number, maximum polymer extensibility parameter and the ratio of polymer to total viscosities upon the flow characteristics. The general local self-similar solution compares well with results of numerical simulations obtained by the RheoFoam module of the freeware OpenFoam code.

Holographic astigmatic particle tracking velocimetry (HAPTV)

The formation of twin images in digital inline holography (DIH) prevents the placement of the focal plane in the center of a sample volume for DIH-based particle tracking velocimetry (DIH-PTV) with a single camera. As a result, it is challenging to apply DIH-PTV for flow measurements in large-scale laboratory facilities or many field applications where it would otherwise be desirable due to the low cost and compact setup. Here we introduce holographic astigmatic PTV (HAPTV) by inserting a cylindrical lens in the optical setup of DIH-PTV, generating distorted holograms. Such distortion is subsequently utilized in a customized reconstruction algorithm to distinguish tracers positioned on different sides of the focal plane which can in turn be placed in the middle of a sample volume. Our HAPTV approach is calibrated under high (1 µm pixel−1) and low (10 µm pixel−1) magnifications with an error standard deviation of 4.2 µm (one particle diameter) and 120.7 µm (~5 times the particle diameter), respectively. We compare the velocity field of a laminar jet flow obtained using HAPTV and conventional PIV to illustrate the accuracy of the technique when applied to practical flow measurement applications. The work demonstrates that HAPTV improves upon the depth of field of conventional astigmatic PTV and enables the implementation of DIH-based PTV for in situ applications.

Deformation and breakup of single drop in laminar and transitional jet flows

Liquid drops were released in laminar and transitional jet flows to investigate their deformation and breakup characteristics. Silicone oil and deionized water were the dispersed phase and continuous phase, respectively. Calibration experiments of oil drops rising in quiescent ambient water were performed to benchmark the experimental system and the image processing method. In jet flow, drop breakup probability, breakup time, and the characteristics of daughter drops were investigated in detail. To address the underlying mechanisms of the drop breakup, visualization experiments and two-dimensional particle image velocimetry (PIV) experiments of the single-phase jet flow were performed. Visualization experiments show that the jet flow changes from laminar to transitional in the Reynolds number interval between 1283 and 1610. Critical capillary and Weber numbers for drop breakup were estimated based on the mean flow velocity and mean deformation and were found to be of the order of 0.2 and 30 respectively for this particular flow system.

A study of a conductive laminar jet flow in an applied magnetic field

This study investigates steady two-dimensional laminar confined jet flow in the presence of an applied magnetic field. The magnetohydrodynamic equations with the format of the stream function and vorticity formulation of the fluid flow are solved numerically. A numerical method was developed by using a first-order upwind scheme at the boundaries and a second-order finite control volume scheme in the flow field. The results show that the expansion region of the jet is moving downstream while the channel width and the Reynolds number are increasing. The vortex and the recirculation zone are stretched with increased Hartmann number, and the jet expansion region is moving upstream while the vortex and the recirculation zone are reduced. The channel width and the Reynolds number for the jet development are positive efforts and the Hartmann number has a suppressed effect in the present confined jet flow field.

Investigation of the effect of an acoustic field on the flow regime of a jet

The paper presents the results of visual study of the structure of a round minijet flowing into the atmosphere exposed to an acoustic field. The studies were performed with the laminar jet flow. According to the photo and video recording of the flow pattern we revealed characteristic features of the jet structure in the acoustic field. Characteristic vortex structures and zones with intense turbulent mixing were detected in the flow. We revealed the process of vortex structures formation in a laminar jet under the effect of the acoustic field, vibrational and rotational regimes of jet flows at the outlet of the pipe 1.35 mm in diameter. The present study is the continuation of the research on a minijet structure in an acoustic field [10].