Radiative bioconvection nanofluid squeezing flow between rotating circular plates: Semi-numerical study with the DTM-Padé approach

2021 ◽  
Author(s):  
A. Zeeshan ◽  
M. B. Arain ◽  
M. M. Bhatti ◽  
F. Alzahrani ◽  
O. Anwar Bég
Keyword(s):  
Reynolds Number ◽  
Thermal Radiation ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Axial Flow ◽  
Radiative Flux ◽  
Squeezing Flow ◽  
Circular Plates ◽  
Flux Approximation ◽  
The Impact

Modern biomedical and tribological systems are increasingly deploying combinations of nanofluids and bioconvecting microorganisms which enable improved control of thermal management. Motivated by these developments, in this study, a new mathematical model is developed for the combined nanofluid bioconvection axisymmetric squeezing flow between rotating circular plates (an important configuration in, for example, rotating bioreactors and lubrication systems). The Buongiorno two-component nanoscale model is deployed, and swimming gyrotactic microorganisms are considered which do not interact with the nanoparticles. Thermal radiation is also included, and a Rosseland diffusion flux approximation is utilized. Appropriate similarity transformations are implemented to transform the nonlinear, coupled partial differential conservation equations for mass, momentum, energy, nanoparticle species and motile microorganism species under suitable boundary conditions from a cylindrical coordinate system into a dimensionless nonlinear ordinary differential boundary value problem. An efficient scheme known as differential transform method (DTM) combined with Padé-approximations is then applied to solve the emerging nonlinear similarity equations. The impact of different non-dimensional parameters i.e. squeezing Reynolds number, rotational Reynolds number, Prandtl number, thermophoresis parameter, Brownian dynamics parameter, thermal radiation parameter, Schmidt number, bioconvection number and Péclet number on velocity, temperature, nanoparticle concentration and motile gyrotactic microorganism density number distributions is computed and visualized graphically. The torque effects on both plates, i.e. the lower and the upper plate, are also determined. From the graphical results, it is seen that momentum in the squeezing regime is suppressed clearly as the upper disk approaches the lower disk. This inhibits the axial flow and produces axial flow retardation. Similarly, by enhancing the value of squeezing Reynolds number, the tangential velocity distribution also decreases. More rigorous squeezing clearly therefore also inhibits tangential momentum development in the regime and leads to tangential flow deceleration. Tables are also provided for multiple values of flow parameters. The numerical values obtained by DTM-Padé computation show very good agreement with shooting quadrature. DTM-Padé is shown to be a precise and stable semi-numerical methodology for studying rotating multi-physical flow problems. Radiative heat transfer has an important influence on the transport characteristics. When radiation is neglected, different results are obtained. It is important therefore to include radiative flux in models of rotating bioreactors and squeezing lubrication dual disk damper technologies since high temperatures associated with radiative flux can impact significantly on combined nanofluid bioconvection which enables more accurate prediction of actual thermofluidic characteristics. Corrosion and surface degradation effects may therefore be mitigated in designs.

On the Axisymmetric Vortex Flow Over a Flat Surface

1969 ◽  
Vol 36 (3) ◽  
pp. 614-619 ◽  
Author(s):  
E. W. Schwiderski
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Critical Reynolds Number ◽  
Numerical Study ◽  
Lower Boundary ◽  
Tangential Velocity ◽  
Slow Motion ◽  
Boundary Layer Separation ◽  
Local Boundary ◽  
Self Similar

The numerical study of the interaction of a potential vortex with a stationary surface recently published by Kidd and Farris [1] is extended through a transformation of the boundary-value problem to Volterra integral equations. The new calculations verified the results by Kidd and Farris and improved the bounds of the critical Reynolds number Nc, beyond which no self-similar vortex flows exist, to 5.5 < Nc < 5.6 The breakdown of the self-similar motions develops through an instability in the lower boundary layer, which is indicated by two inflection points in the tangential velocity profile. At the critical Reynolds number the lower inflection point reaches the surface and indicates the beginning of boundary-layer separation in the wake-type flow. If the Stokes linearization is applied, one arrives at a new Stokes paradox. However, this “paradox” can be resolved by correcting the free-stream pressure distortion of the Stokes approximation. The new slow-motion approximation is nonlinear and yields an integral which is also free of the Whitehead paradox. The properties of the new exact solution confirm the novel flow features previously detected in almost self-similar motions, which were constructed by adjustable local boundary-layer approximations.

scholarly journals Numerical study on the energy cascade of pulsatile Newtonian and power-law flow models in an ICA bifurcation

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245775
Author(s):  
Samar A. Mahrous ◽  
Nor Azwadi Che Sidik ◽  
Khalid M. Saqr
Keyword(s):  
Reynolds Number ◽  
Power Law ◽  
Numerical Study ◽  
Carotid Bifurcation ◽  
Shear Thinning ◽  
Energy Cascade ◽  
Hemodynamic Parameters ◽  
Vortex Identification ◽  
Newtonian Viscosity ◽  
The Impact

The complex physics and biology underlying intracranial hemodynamics are yet to be fully revealed. A fully resolved direct numerical simulation (DNS) study has been performed to identify the intrinsic flow dynamics in an idealized carotid bifurcation model. To shed the light on the significance of considering blood shear-thinning properties, the power-law model is compared to the commonly used Newtonian viscosity hypothesis. We scrutinize the kinetic energy cascade (KEC) rates in the Fourier domain and the vortex structure of both fluid models and examine the impact of the power-law viscosity model. The flow intrinsically contains coherent structures which has frequencies corresponding to the boundary frequency, which could be associated with the regulation of endothelial cells. From the proposed comparative study, it is found that KEC rates and the vortex-identification are significantly influenced by the shear-thinning blood properties. Conclusively, from the obtained results, it is found that neglecting the non-Newtonian behavior could lead to underestimation of the hemodynamic parameters at low Reynolds number and overestimation of the hemodynamic parameters by increasing the Reynolds number. In addition, we provide physical insight and discussion onto the hemodynamics associated with endothelial dysfunction which plays significant role in the pathogenesis of intracranial aneurysms.

Numerical Study of Tip Leakage Vortex Around a NACA0009 Hydrofoil

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Zhen Bi ◽  
Xueming Shao ◽  
Lingxin Zhang
Keyword(s):  
Axial Velocity ◽  
Numerical Study ◽  
Axial Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Vortex Center ◽  
Long Distance ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
The Impact

Abstract In the tip clearance flow, the dominant vortex is the tip leakage vortex (TLV), which has a significant impact on the hydraulic and cavitation performance of axial flow machineries. In order to reveal the impact mechanism of the gap size on the TLV, gap flows with two gap sizes, i.e., τ=0.2 (2 mm) and τ=1.0 (10 mm), are numerically investigated. A NACA0009 hydrofoil is selected to create the gap flow, with an incoming velocity of 10 m/s and an attack angle of 10 deg. The results show that the two flow cases are significantly different in terms of vortex feature and the leakage flow distribution. In the small gap, a type of jet-pattern flow appears, whereas a type of rolling-pattern flow passes over the large gap. The vertical velocity gradient of the leakage flow has a decisive influence on the TLV trajectory. In addition, for the large gap, the axial velocity in the vortex center exceeds the incoming flow. This jet-like state of axial velocity can be maintained for a long distance, making the vortex more stable. However, the axial velocity in the case of τ=0.2 cannot stay at the jet-like state and rapidly switches to a wake-like state.

scholarly journals Water washing of axial flow compressors: numerical study on the fate of injected droplets

2020 ◽  
Vol 197 ◽  
pp. 11015
Author(s):  
Giuliano Agati ◽  
Francesca Di Gruttola ◽  
Serena Gabriele ◽  
Domenico Simone ◽  
Paolo Venturini ◽  
...  
Keyword(s):  
Numerical Study ◽  
Axial Flow ◽  
Rotor Blades ◽  
Injection System ◽  
Asymmetric Distribution ◽  
Wall Functions ◽  
Erosion Risk ◽  
Water Washing ◽  
Washing Process ◽  
The Impact

In turbomachinery applications blade fouling represents a main cause of performance degradation. Among the different techniques currently available, online water washing is one of the most effective in removing deposit from the blades. Since this kind of washing is applied when the machine is close to design conditions, injected droplets are strongly accelerated when they reach the rotor blades and the understanding of their interaction with the blades is not straightforward. Moreover, undesirable phenomena like blades erosion or liquid film formation can occur. The present study aims at assessing droplets dragging from the injection system placed at the compressor inlet till the first stage rotor blades, with a focus on droplets impact locations, on the washing process and the associated risk of erosion. 3D numerical simulations of the whole compressor geometry (up to the first rotor stage) are performed by using Ansys Fluent to account for the asymmetric distribution of the sprays around of the machine struts, IGV and rotor blades. The simulations are carried out by adopting the k-ε realizable turbulence model with standard wall functions, coupled with the discretephase model to track injected droplets motion. Droplets-wall interaction is also accounted for by adopting the Stanton-Rutland model which define a droplet impact outcome depending on the impact conditions. The induced erosion is evaluated by adopting an erosion model previously developed by some of the authors and implemented in Fluent through the use of a User Defined Function (UDF). Two sets of simulations are performed, by considering the rotor still and rotating, representative of off-line and on-line water washing conditions, respectively. In the rotating simulation, the Multiple Reference Frame Model is used. The obtained results demonstrate that the washing process differs substantially between the fixed and the rotating case. Moreover, to quantify the water washing effectiveness and the erosion risk, new indices were introduced and computed for the main components of the machine. These indices can be considered as useful prescriptions in the optimization process of water washing systems.

Numerical Study of the Steady-State Tip Vortex Flow Over a Finite-Span Hydrofoil

1998 ◽  
Vol 120 (2) ◽  
pp. 345-353 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Vortex Core ◽  
Axial Velocity ◽  
Stokes Equations ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Tangential Velocity ◽  
Tip Vortex ◽  
Finite Span

The flow over a finite-span hydrofoil creating a tip vortex was numerically studied by computing the full Navier-Stokes equations. A good agreement in pressure distribution and oil flow pattern was achieved between the numerical solution and available experimental data. The steady-state roll-up process of the tip vortex was described in detail from the numerical results. The effect of the angle of attack, the Reynolds number, and the hydrofoil planform on the tip vortex was investigated. The axial and tangential velocities within the tip-vortex core in the near-field wake region were greatly influenced by the angle of attack. A jet-like profile in the axial velocity was found within the tip-vortex core at high angle of attack, while a wake-like profile in the axial velocity was found at low angle of attack. Increasing the Reynolds number was found to increase the maximum axial velocity, but only had a slight impact on the tangential velocity. Finally, a swept hydrofoil planform was found to attenuate the strength of the tip vortex due to the low-momentum boundary layer traveling into the tip vortex on the suction side.

scholarly journals Numerical Study on Sloshing Characteristics with Reynolds Number Variation in a Rectangular Tank

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 53 ◽  
Author(s):  
Hyunjong Kim ◽  
Mohan Dey ◽  
Nobuyuki Oshima ◽  
Yeon Lee
Keyword(s):  
Reynolds Number ◽  
Pressure Fluctuation ◽  
Numerical Study ◽  
Amplitude Spectrum ◽  
Linear Solution ◽  
Rectangular Tank ◽  
Large Pressure ◽  
Pressure Cycle ◽  
Number Variation ◽  
The Impact

A study on sloshing characteristics in a rectangular tank, which is horizontally excited with a specific range of the Reynolds number, is approached numerically. The nonlinearity of sloshing flow is confirmed by comparing it with the linear solution based on the potential theory, and the time series results of the sloshing pressure are analyzed by Fast Fourier Transform (FFT) algorithm. Then, the pressure fluctuation phenomena are mainly observed and the magnitude of the amplitude spectrum is compared. The results show that, when the impact pressure is generated, large pressure fluctuation in a pressure cycle is observed, and the effects of the frequencies of integral multiples when the fundamental frequency appears dominantly in the sloshing flow.

The Stability of Viscous Axial Flow in the Entry Region of an Annulus with a Rotating Inner Cylinder

1976 ◽  
Vol 18 (5) ◽  
pp. 221-228 ◽  
Author(s):  
B. W. Martin ◽  
M. A. Hasoon
Keyword(s):  
Reynolds Number ◽  
Axial Length ◽  
Axial Velocity ◽  
Tangential Velocity ◽  
Axial Flow ◽  
Radius Ratio ◽  
Neutral Stability ◽  
Hot Wire ◽  
Core Rotation ◽  
The Stability

The stability of developing tangential flow induced by the imposition of an axial velocity on the tangential velocity distribution created by core rotation is theoretically and experimentally investigated. A linear stability analysis is used to examine the influence of axial length, axial Reynolds number and annulus radius ratio on the critical Taylor number for neutral stability when the axial velocity is assumed uniform. Predictions compare favourably with measurements obtained by hot-wire anemometer for air flowing in an annulus of radius ratio 0·9, particularly at small Reynolds number and large values of the axial length parameter.

scholarly journals Impact of Lorentz Force in Thermally Developed Pulsatile Micropolar Fluid Flow in a Constricted Channel

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2173
Author(s):  
Muhammad Umar ◽  
Amjad Ali ◽  
Zainab Bukhari ◽  
Gullnaz Shahzadi ◽  
Arshad Saleem
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Thermal Radiation ◽  
Lorentz Force ◽  
Axial Velocity ◽  
Micropolar Fluid ◽  
Rotation Velocity ◽  
Micropolar Fluid Flow ◽  
The Impact ◽  
Constricted Channel

This work aimed to analyze the heat transfer of micropolar fluid flow in a constricted channel influenced by thermal radiation and the Lorentz force. A finite difference-based flow solver, on a Cartesian grid, was used for the numerical solution after transforming the governing equations into the vorticity-stream function form. The impact of various emerging parameters on the wall shear stress, axial velocity, micro-rotation velocity and temperature profiles is discussed in this paper. The temperature profile is observed to have an inciting trend towards the thermal radiation, whereas it has a declining trend towards the Hartman and Prandtl numbers. The axial velocity profile has an inciting trend towards the Hartman number, whereas it has a declining trend towards the micropolar parameter and Reynolds number. The micro-rotation velocity escalates with the micropolar parameter and Hartman number, whereas it de-escalates with the Reynolds number. The Nusselt number is observed to have a direct relationship with the Prandtl and Reynolds numbers.

scholarly journals Elliptic instability in a strained Batchelor vortex

2007 ◽  
Vol 577 ◽  
pp. 341-361 ◽  
Author(s):  
LAURENT LACAZE ◽  
KRIS RYAN ◽  
STÉPHANE LE DIZÈS
Keyword(s):  
Reynolds Number ◽  
Strain Field ◽  
Flow Parameter ◽  
Numerical Study ◽  
Normal Modes ◽  
Axial Flow ◽  
Base Flow ◽  
Large Reynolds Number ◽  
Resonant Coupling ◽  
Flow Parameters

The elliptic instability of a Batchelor vortex subject to a stationary strain field is considered by theoretical and numerical means in the regime of large Reynolds number and small axial flow. In the theory, the elliptic instability is described as a resonant coupling of two quasi-neutral normal modes (Kelvin modes) of the Batchelor vortex of azimuthal wavenumbers m and m + 2 with the underlying strain field. The growth rate associated with these resonances is computed for different values of the azimuthal wavenumbers as the axial flow parameter is varied. We demonstrate that the resonant Kelvin modes m = 1 and m = −1 which are the most unstable in the absence of axial flow become damped as the axial flow is increased. This is shown to be due to the appearance of a critical layer which damps one of the resonant Kelvin modes. However, the elliptic instability does not disappear. Other combinations of Kelvin modes m = −2 and m = 0, then m = −3 and m = −1 are shown to become progressively unstable for increasing axial flow. A complete instability diagram is obtained as a function of the axial flow parameter for several values of the strain rate and Reynolds number.The numerical study considers a system of two counter-rotating Batchelor vortices in which the strain field felt by each vortex is due to the other vortex. The characteristics of the most unstable linear modes developing on the frozen base flow are computed by direct numerical simulations for two axial flow parameters and compared to the theory. In both cases, a very good agreement is obtained for the most unstable modes. Less unstable modes are also identified in the numerics and shown to correspond to peculiar resonances involving Kelvin modes from branches of different labels.

scholarly journals Thermally Enhanced Darcy-Forchheimer Casson-Water/Glycerine Rotating Nanofluid Flow with Uniform Magnetic Field

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 605
Author(s):  
Anum Shafiq ◽  
Ghulam Rasool ◽  
Hammad Alotaibi ◽  
Hassan M. Aljohani ◽  
Abderrahim Wakif ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Velocity Profile ◽  
Radial Velocity ◽  
Skin Friction ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Nanofluid Flow ◽  
Porosity Parameter ◽  
Forchheimer Number ◽  
The Impact

This numerical study aims to interpret the impact of non-linear thermal radiation on magnetohydrodynamic (MHD) Darcy-Forchheimer Casson-Water/Glycerine nanofluid flow due to a rotating disk. Both the single walled, as well as multi walled, Carbon nanotubes (CNT) are invoked. The nanomaterial, thus formulated, is assumed to be more conductive as compared to the simple fluid. The properties of effective carbon nanotubes are specified to tackle the onward governing equations. The boundary layer formulations are considered. The base fluid is assumed to be non-Newtonian. The numerical analysis is carried out by invoking the numerical Runge Kutta 45 (RK45) method based on the shooting technique. The outcomes have been plotted graphically for the three major profiles, namely, the radial velocity profile, the tangential velocity profile, and temperature profile. For skin friction and Nusselt number, the numerical data are plotted graphically. Major outcomes indicate that the enhanced Forchheimer number results in a decline in radial velocity. Higher the porosity parameter, the stronger the resistance offered by the medium to the fluid flow and consequent result is seen as a decline in velocity. The Forchheimer number, permeability parameter, and porosity parameter decrease the tangential velocity field. The convective boundary results in enhancement of temperature facing the disk surface as compared to the ambient part. Skin-friction for larger values of Forchheimer number is found to be increasing. Sufficient literature is provided in the introduction part of the manuscript to justify the novelty of the present work. The research greatly impacts in industrial applications of the nanofluids, especially in geophysical and geothermal systems, storage devices, aerospace engineering, and many others.

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