Showing papers by "Kuvempu University published in 2021"

Non-Newtonian hybrid nanofluid flow over vertically upward/downward moving rotating disk in a Darcy-Forchheimer porous medium

Abstract: Researchers and engineers working in the field of thermal analysis are pursuing new ways to improve the performance of electrical devices by improving their thermal properties. Impressed by these applications, in this paper, we examined the influence of activation energy over Darcy–Forchheimer flow of Casson fluid with suspension of Graphene oxide and Titanium dioxide nanoparticles considering 50% of Ethylene glycol as base fluid in a porous media. The problem is basically an extension of the well-known problem of von Karman’s viscous pump in a situation where the disk rotates. The modelled equations are converted to ODEs using the similarity transformations. The numerical solution is obtained using the RKF-45 method by adopting shooting technique. The calculation of mass and heat transfer rate is analysed through graphs. It is observed that the upward and downward motion of the disk exerts similar effects to that of the injection/suction through the wall. The downward motion of the disk causes reduction in velocity and temperature fields. Furthermore, variation in velocity, thermal, and concentration gradients for several non-dimensional parameters are studied briefly and demonstrated with the help of graphs. The obtained result reveals that increase in Casson parameter reduces the velocity of the fluid.

Theoretical Study of Convective Heat Transfer in Ternary Nanofluid Flowing past a Stretching Sheet

Abstract: A new theoretical tri-hybrid nanofluid model for enhancing the heat transfer is presented in this article. This model explains the method to obtain a better heat conductor than the hybrid nanofluid. The tri-hybrid nanofluid is formed by suspending three types of nanoparticles with different physical and chemical bonds into a base fluid. In this study, the nanoparticles TiO2, Al2O3 and SiO2 are suspended into water thus forming the combination TiO2-SiO2-Al2O3-H2O. This combination helps in decomposing harmful substances, environmental purification and other appliances that requires cooling. The properties of tri-hybrid nanofluid such as Density, Viscosity, Thermal Conductivity, Electrical Conductivity and Specific Heat capacitance are defined mathematically in this article. The system of equations that governs the flow and temperature of the fluid are converted to ordinary differential equations and are solved using RKF-45 method. The results are discussed through graphs and it is observed that the tri-hybrid nanofluid has a better thermal conductivity than the hybrid nanofluid.

Bioconvection of a Radiating Hybrid Nanofluid Past a Thin Needle in the Presence of Heterogeneous–Homogeneous Chemical Reaction

Abstract: The photocatalytic nature of TiO2 finds applications in medicinal field to kill cancer cells, bacteria, and viruses under mild ultraviolet illumination and the antibacterial characteristic of Ag makes the composition Ag−TiO2 applicable for various purposes. It can also be used in other engineering appliances and industries such as humidity sensor, coolants, and in footwear industry. Hence, this study deals with the analysis of the effects of magnetic field, thermal radiation, and quartic autocatalysis of heterogeneous–homogeneous reaction in an electrically conducting Ag−TiO2−H2O hybrid nanofluid. Furthermore, the gyrotactic microorganisms are used as active mixers to prevent agglomeration and sedimentation of TiO2 that occurs due to its hydrophobic nature. The mathematical model takes the form of partial differential equations with viscosity and thermal conductivity being the functions of volume fraction. These equations are converted to ordinary differential equations by using similarity transformation and are solved by RKF-45 method with the aid of shooting method. It is observed that the increase in the size of the needle enhances the overall performance of the hybrid nanofluid. Furthermore, the temperature of the hybrid nanofluid increases with the increase in volume fraction. It is observed that the friction produced by the Lorentz force increases the temperature of the nanofluid. It is further observed that the heterogeneous reaction parameter has more significant effect on the concentration of bulk fluid than the homogeneous reaction parameter.

Significance of buoyancy and Lorentz forces on water-conveying iron(III) oxide and silver nanoparticles in a rectangular cavity mounted with two heated fins: heat transfer analysis

Abstract: During the production of iron(iii) oxide and silver nanoparticles where water is inevitable, little is known on the transport phenomenon in a rectangular cavity mounted with two heated fins on the bottom wall where buoyancy and Lorentz forces are significant. The natural convection heat transfer of hybrid nanofluid flow in a rectangular cavity mounted with two heated fins on the bottom wall is studied. The hybrid nanofluid containing the nanoparticles of $${\text{Fe}}_{3} {\text{O}}_{4}$$ and $${\text{Ag}}$$ with water as base fluid is considered for the analysis. The derived governing partial differential equations are non-dimensionalized and solved numerically by applying the finite element method. It was concluded that at lower Rayleigh number and higher Hartmann number laminar flow is visible and at higher $${\text{Ra}}$$ and lower $${\text{Ha}}$$ , turbulent flow is seen. The intensity of the velocity profile and streamline function rises with the Rayleigh number. The nanoparticle volume fraction also affects the thermal profile and streamlined function.

Exponential space-dependent heat generation impact on MHD convective flow of Casson fluid over a curved stretching sheet with chemical reaction

Abstract: The present article focuses on the effect of exponential space-dependent heat source on magneto-hydrodynamic Casson fluid flow over a curved stretching sheet along with chemical reaction and convective heat and mass flux boundary conditions. The equations that govern the flow are reduced from system of partial differential equations to system of ordinary differential equations with the assistance of similarity transformations, and after that, they are solved using the numerical technique Runge–Kutta–Fehlberg fourth–fifth-order method. The obtained numerical values are plotted through graphs for velocity, temperature and concentration profiles with various parameters, and the variations based on these plots are discussed. Here, it is incurred that the velocity and concentration fields increase with increasing curvature parameter, whereas temperature profile shows inverse relation. Also, increment of Casson parameter shows the significant change in all flow profiles. Both thermal Biot number and concentration Biot number have increasing impact on temperature and concentration profiles, respectively.

Thermal and entropy generation of non-Newtonian magneto-Carreau fluid flow in microchannel

Abstract: The heat flow in microchannels can be established in numerous applications such as micro air vehicles, mechanical–electromechanical systems, cooling of electronic devices and micro heat exchanger systems. Heat flow optimization deliberates the function of entropy generation minimization (EGM) in engineering applications. Hence, this paper investigates the heat transport of non-Newtonian magneto-Carreau fluid in a microchannel with EGM. Mathematical modeling incorporates the Carreau fluid model. Further, viscous heating, Joule heating and convective heating aspects are also analyzed. The physical features of entropy production in the flow of non-Newtonian Carreau fluid in a microchannel are the major focus of this model. Dimensionless variables are executed for the simplicity of basic equations. The subsequent system is treated by using finite element method. Behaviors of effective parameters on velocity, Bejan number, entropy generation rate and temperature are interpreted. It is established that EGM is occurred for larger values of Weissenberg number. The Carreau fluid exponent is positively related to Bejan number, whereas it is negatively related to EG, temperature and velocity fields.

Aggregation induced emission based active conjugated imidazole luminogens for visualization of latent fingerprints and multiple anticounterfeiting applications.

Abstract: Aggregation-induced emission based organic heterocyclic luminogens bearing conjugated electronic structures showed much attention due to its excellent fluorescence in aggregation state. In this communication, a novel conjugated blue light emitting imidazole molecule is synthesized by one pot multicomponent reaction route is reported for the first time. The prepared molecule exhibits a strong fluorescence in aggregation state with exceptional properties, such as high purity, inexpensive, eco-friendly, large scale production, high photostability, etc. By considering these advantages, a new fluorescence based platform has been setup for in-situ visualization of latent fingerprints and its preservation by spray method followed by Poly(vinyl alcohol) masking. A clear and well defined fluorescence fingerprint images are noticed on variety of surfaces by revealing level 1–3 ridge features upon ultraviolet 365 nm light exposure. The dual nature of binding specificity as well as excellent fluorescence properties permits the visualization of latent fingerprints for longer durations (up to 365 days) with superior contrast, high sensitivity, efficiency, selectivity and minimal background hindrance. We further fabricated unclonable invisible security ink for various printing modes on valuable goods for protection against forging. The developed labels are displaying uniform distribution of ink and exceptional stability under various atmospheric environments. The development of long preservative information using aggregation-induced emission based luminogen opens up a new avenue in advanced forensic and data security applications.

Riemann Soliton within the framework of contact geometry

Abstract: In this paper, we study contact metric manifold whose metric is a Riemann soliton. First, we consider Riemann soliton (g; V ) with V as contact vector eld on a Sasakian manifold (M; g) and in this case we prove that M is either of constant curvature +1 (and V is Killing) or D-homothetically xed -Einstein manifold (and V leaves the structure tensor φ invariant). Next, we prove that if a compact K-contact manifold whose metric g is a gradient almost Riemann soliton, then it is Sasakian and isometric to a unit sphere S2n+1. Further, we study H-contact manifold admitting a Riemann soliton (g; V ) where V is pointwise collinear with .Key words: Contact metric manifold, Riemann soliton, gradient almost Riemann soliton.

Darcy-Forchheimer flow of dusty tangent hyperbolic fluid over a stretching sheet with Cattaneo-Christov heat flux

Abstract: The current investigation explores the impact of Darcy-Forchheimer flow and Cattaneo-Christov heat transfer of dusty tangent hyperbolic fluid over a stretching sheet. The problem of the model is re...

An unsteady thermal investigation of a wetted longitudinal porous fin of different profiles

Abstract: The unsteady thermal behavior of a porous longitudinal fin in a fully wet circumstance in the existence of convection as well as radiation effect is modeled in the present analysis The thickness of the fin is assumed to vary with the length of the fin Therefore, different profiles of the fin such as rectangular, convex, as well as triangular-shaped fin have been considered Darcy’s model is imposed to study porous nature The derived nonlinear partial differential equation is non-dimensionalized and solved numerically with the help of Maple software by the Finite Difference Method The transient thermal response and fin efficiency for diverse values of the significant parameters have been discussed graphically A comparative analysis of three different shaped fins has been performed It is found that the temperature drop rate is faster in triangular fin and efficiency is higher in rectangular fin

Antimicrobial activity and metabolite profiling of endophytic fungi in Digitaria bicornis (Lam) Roem. and Schult. and Paspalidium flavidum (Retz.) A. Camus.

Abstract: Endophytic fungal occurrences were studied in aerial regions of Digitaria bicornis and Paspalidium flavidum by three isolation methods: potato dextrose agar (PDA), malt extract agar (MEA), and moist blotters. Seventy species of 29 genera of endophytic fungi in D. bicornis and 71 species of 30 genera in P. flavidum were documented. Endophytic fungal communities were grouped into 40 and 43 anamorphic ascomycetes (21 and 23 genera) and 20 teleomorphic ascomycetes (6 and 7 genera) in D. bicornis and P. flavidum, respectively. PDA supported the expression of larger number of fungal communities than MEA and MB; and P. flavidum hosted more number of endophytic fungi than D. bicornis. Seasons played an important role in supporting the assemblage of fungal endophytes. Endophytic fungal species richness and assemblages in plant regions were determined for alpha, beta, and gamma diversities. The ethyl acetate followed by methanolic extracts of certain fungal species showed good antagonistic and antibacterial activities. Among fungal endophytes, Curvularia protuberata and Penicillium citrinum exhibited high antagonistic and antibacterial activities. The high-resolution orbitrap liquid chromatography-mass spectrometry of ethyl acetate crude extracts of C. protuberata and P. citrinum revealed the presence of antifungal and antimicrobial, besides a host of compounds in the extracts. The present study indicated that grass endophytes are the sources of compounds with antimicrobial and other pharmacological activities.