Effect of boundary absorption on dispersion in Casson fluid flow in an annulus: application to catheterized artery

The combined effect of annular gap, yield stress and irreversible boundary reaction on the dispersion process in a Casson fluid flow is studied using generalized dispersion model. The study describes the development of dispersive transport following the injection of a tracer in terms of the three effective transport coefficients viz. absorption, convection and dispersion coefficients. The combined effect of annular gap, yield stress and wall absorption parameter on the above three effective transport coefficients is discussed. It is observed that the absorption coefficient is independent of the yield stress of the fluid and depends on the annular gap and wall absorption parameter. It is also observed that the asymptotic convection, dispersion coefficients are dependent on the yield stress of the fluid, annular gap and wall absorption parameter. The effect of the flow parameters on the mean concentration is studied. Application of this model for understanding the dispersion of solute in blood in a catheterized artery is discussed.     

Buoyancy forces and activation energy on the MHD radiative flow over an exponentially stretching sheet with second‐order slip

The current study explores the effects of second‐order slip and activation energy (AE) on the magnetohydrodynamic and radiative fluid flow caused by a surface with exponential stretching. The binary chemical reaction with mixed convection is considered in this physical model to discover the heat transfer phenomenon. The governing system of equations leads to a set of nonlinear ordinary differential equations by using scaling analysis. The transformed system is calculated computationally by using the most powerful Shooting procedure with the support of MATLAB software. The characteristics of various flow parameters on the governing flow field are exhibited pictorially and deliberated. The results revealed that the coefficient of heat and mass transfer upsurge with growing values of the second‐order slip parameter and skin friction coefficient has a reverse effect on the first‐order slip parameter. The thermal measure of the fluid in the presence of suction and slip conditions is seen to be lesser than that with the nonslip and nonsuction conditions. The heat measure of the fluid augments with the rising buoyancy parameter. The influence of slips coupled with AE is significant in the fluid flow and heat transfer characteristics. The outputs of the current investigation are validated by comparing the Nusselt number with the available results and are found to closely agree as a limiting case.     

Exact analysis of unsteady convective diffusion in Casson fluid flow in an annulus – Application to catheterized artery

Summary The dispersion of a solute in the flow of a Casson fluid in an annulus is studied. The generalized dispersion model is employed to study the dispersion process. The effective diffusion coefficient, which describes the whole dispersion process in terms of a simple diffusion process, is obtained as a function of time, in addition to its dependence on the yield stress of the fluid and on the annular gap between the two cylinders. It is observed that the dispersion coefficient changes very rapidly for small values of time and becomes essentially constant as time takes large values. In non–Newtonian fluids the steady state is reached at earlier instants of time when compared to the Newtonian case and the time taken to reach the steady state is seen to depend on the values of the yield stress. It is observed that a decrease in the annular gap inhibits the dispersion process for all times both in Newtonian as well as in non–Newtonian fluids. When the yield stress is 0.05, depending upon the size of the annular gap (0.9–0.7) the reduction factor in the dispersion coefficient varies in the range 0.58–0.08. The application of this study for understanding the dispersion of an indicator in a catheterized artery is discussed.     

Coupled effect of multislips and activation energy in a micropolar nanoliquid on a convectively heated elongated surface

This research communication explores the impact of wall slips along with the suspension of nanomaterials in a chemically reactive micropolar liquid stream on a stretched surface with convective heating. Activation of energy is analyzed through the modified Arrhenius function. Radiative heat flux with nonlinearity and temperature-dependent thermal source (sink) are considered in the heat transmission process. The Cattaneo–Christov approach featuring the time of thermal relaxation is employed. Successive application of scaling analysis followed by the Runge–Kutta–Fehlberg numerical approach delivered computational solutions for the partial differential equations delineating the problem under study. The response of flow variables for different values of various emerged physical variables is elaborated in detail via graphical and numerical presentations. Comparison of the outcome of the current analysis for certain cases is in accordance with the outcomes available in the literature. The findings reveal that pairs of velocity, microrotation, temperature, and species concentration oppositely reacted to both parameters of slip. The temperature of the nanofluid is improved by 18.5%, for specified values of radiation and temperature ratio parameters over that of the pure base liquid. Activation energy augments concentration. The drag coefficient declines with growing thermal and solutal Grashof numbers. Sherwood number is enhanced for higher values of the temperature difference and chemical reaction parameters.     

Effect of body acceleration on dispersion of solutes in blood flow

The unsteady dispersion of a solute in blood flow modeling blood as a Newtonian fluid under the influence of a body acceleration is studied using the generalized dispersion model proposed by Gill and Sankarasubramanian [13]. As a result, the total process of dispersion can be described in terms of a simple diffusion process with the effective diffusion coefficient as a function of time. The model brings out mainly the effect of body acceleration and radius of the artery on the overall dispersion process. In the absence of body acceleration, the dispersion coefficient is found to increase rapidly and maintains a steady value in aorta while in other arteries it oscillates about a mean value after reaching it. Body acceleration is observed to enhance the value of the dispersion coefficient in all arteries. The effective diffusivity is found to depend on body acceleration. In the presence of body acceleration, it is noticed that there is a decrease in the effective diffusivity in aorta, femoral, and carotid while in coronary it is increased.     

Transport of thermal energy in the magnetohydrodynamic oblique stagnation point flow in a hybrid nanofluid with nanoparticle shape effect

In the present paper, the augmented heat characteristics of a hybrid nanofluid which is a blend of Al₂O₃ (alumina) and Ag (silver) in the host hybrid fluid (C₂H₆O₂-H₂O) (50%–50%) impinging obliquely on an elastic surface with magnetic lines of force are investigated. The properties of the nanofluid are assessed through the computational solutions established with the aid of the popular Runge–Kutta–Fehlberg fifth-order (RKF 5) numerical technique. Outputs of the analysis reveal that the rate of thermal energy transport in the hybrid (mono) nanofluid is enhanced by 11.5% (5.8%) by using blade-shaped nanoparticles in comparison to that of the spherical particles. Stream contours of both nanofluids are inclined to the left (right) of the stagnation-point for positive (negative) values of the stagnation flow parameter.     

Effect of thermophoresis and Brownian motion on the melting heat transfer of a Jeffrey fluid near a stagnation point towards a stretching surface: Buongiorno's model

This analysis intends to address the coupled effect of phase change heat transfer, thermal radiation, and viscous heating on the MHD flow of an incompressible chemically reactive nanofluid in the vicinity of the stagnation point toward the stretching surface, taking a Jeffrey fluid as the base fluid. Convergent analytical solutions for the nonlinear boundary layer equations are obtained by the successive application of scaling variables and the highly efficacious homotopy analysis method. Error analysis is implemented to endorse the convergence of the solutions. Through parametric examination, influence of various physical parameters occurring in analysis of the profiles of velocity, temperature, and nanoparticle concentration, coefficient of surface drag, rates of mass and heat transfer is explored pictorially. The Deborah number and the melting parameter are found to enhance velocity, and the associated momentum boundary layers are thicker, whereas the magnetic field depreciates the flow rate. Temperature is observed to enhance with the thermophoresis parameter, Prandtl number and Eckert number, whereas a reduction is seen with the thermal radiation parameter and Brownian motion parameter. Nanoparticle concentration is depleted by the chemical reaction parameter, the thermophoresis parameter, and the Lewis number.     

Heat transfer in the flow of blood‐gold Carreau nanofluid induced by partial slip and buoyancy

Dynamics of blood containing gold nanoparticles on a syringe and other objects with a nonuniform thickness is of importance to experts in the industry. This study presents the significance of partial slip (i.e. combination of linear stretching and velocity gradient) and buoyancy on the boundary layer flow of blood‐gold Carreau nanofluid over an upper horizontal surface of a paraboloid of revolution (uhspr). In this report, the viscosity of the Carreau fluid corresponding to an infinite shear‐rate is assumed as zero, meanwhile, the viscosity corresponding to zero shear‐rate, density, thermal conductivity, and heat capacity were assumed to vary with the volume fraction of nanoparticles. The governing equation that models the transport phenomenon were non‐dimensionalized and parameterized using suitable similarity variables and solved numerically using classical Runge–Kutta method with shooting techniques and MATLAB bvp4c package for validation. The results show that temperature distribution across the flow decreases more significantly with buoyancy‐related parameter when the influence of partial slip was maximized. Maximum velocity of the flow is ascertained at larger values of partial slip and buoyancy parameters. At smaller values of Deborah number and large values of volume fraction, maximum local skin friction coefficient, and local heat transfer rate are ascertained.