Research Article Heat and Mass Transfer in Three-Dimensional Flow of an Oldroyd-B Nanofluid with Gyrotactic Micro-Organisms
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Hindawi Mathematical Problems in Engineering Volume 2018, Article ID 6790420, 15 pages https://doi.org/10.1155/2018/6790420 Research Article Heat and Mass Transfer in Three-Dimensional Flow of an Oldroyd-B Nanofluid with Gyrotactic Micro-Organisms M. Sulaiman,1,2 Aamir Ali ,1 and S. Islam 2 1 Department of Mathematics, COMSATS University Islamabad, Attock Campus, Attock, 43600, Pakistan 2Department of Mathematics, Abdul Wali Khan University, Mardan, Khyber Pakhtunkhwa, 23200, Pakistan Correspondence should be addressed to Aamir Ali; aamir [email protected] Received 10 December 2017; Revised 28 February 2018; Accepted 29 April 2018; Published 6 September 2018 Academic Editor: Efstratios Tzirtzilakis Copyright © 2018 M. Sulaiman et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tis paper discusses the three-dimensional fow of the gyrotactic bioconvection of an Oldroyd-B nanofuid over a stretching surface. Teory of microorganisms is utilized to stabilize the suspended nanoparticles through bioconvection induced by the efects of buoyancy forces. Analytic solution for the governing nonlinear equations is obtained by using homotopy analysis method (HAM). Te efects of involved parameters on velocity, temperature, nanoparticles concentration, and density of motile microorganisms are discussed graphically. Te local Nusselt, Sherwood, and motile microorganisms numbers are also analyzed graphically. Several known results have been pointed out as the particular cases of the present analysis. It is found that the non-Newtonian fuid parameters, i.e., relaxation time parameter �1 and retardation time parameter �2, have opposite efects on the velocity profle. Te velocity of the fuid and boundary layer thickness decreases for increasing relaxation time while it decreases for increasing retardation time efects. 1. Introduction non-Newtonian fuid models [2–10]. However, in practical applications sometimes, the fow is three-dimensional. In In recent years the signifcance of the study of non- view of such motivation, researchers have studied the three- Newtonian fuids has remarkably increased due to its appli- dimensional fow for diferent fow geometries (see ref. [11– cations in engineering, industry, and biological sciences, e.g., 17]). in material processing, food, and cosmetic industries [1]. Te problem of heat and mass transfer analysis over a Tese applications generally involve complex geometries and stretched boundary layer is of great interest to researchers due require that the response of the fuid to given temperature to its engineering and industrial applications like glass fber, conditions is controlled. Te basic equations that governs manufacture and drawing of plastics and rubber sheets, paper the fow of non-Newtonian fuids are highly nonlinear. Te production, cooling of continuous stripes and an infnite mathematical description of a non-Newtonian fuid requires metallic sheet, the continuous casting, polymer extrusion a constitutive equation that determines the rheological prop- process, heat treated materials travelling on conveyer belts, erties of the fuid. Due to the complexity, the aforementioned food processing, and many others. Sakiadis [18] has done the fuids are generally divided into three types, namely, the pioneer work in the analysis of the boundary layer fow on diferential type, the rate type, and the integral type. Te a moving surface, which was later extended by Crane [19] simplest example of rate type fuid is Maxwell fuid model by considering the linearly stretching surface. Rashad and which narrates the properties of relaxation time. But it cannot Kabeir [20] studied the heat and mass transfer in transient predict the retardation time efects. Te Oldroyd-B fuid fow by mixed convection boundary layer over a stretching is one subclass of the rate type fuid which describes the sheet embedded in a porous medium with chemically reactive properties of both the relaxation time and the retardation species. Sandeep and Sulochana [21] studied the general- time. Tere are several investigations in this direction for two- ized model for momentum and heat transfer behavior of dimensional fow confgurations with diferent features of the Jefrey, Maxwell, and Oldroyd-B nanofuids over a stretching 2 Mathematical Problems in Engineering →∞,→ ∞,→ ∞ →0, v → 0 Nanoparticles and micro-organisms = w = w = w v=v(y) =by = () = Figure 1: Geometry of the problem. surface with nonuniform heat source/sink. Afer that, several In present study, we have entered a new concept in the investigations have been done by considering diferent fow problem of boundary layer fow passing a stretching sheet. We confgurations [22–28]. have considered the three-dimensional bioconvection fow of With the advent of nanoscience, nanofuids have become an Oldroyd-B nanofuid which contains self-impelled motile a focus of attention in the study of fuid fow in the presence gyrotactic microorganisms, over a bidirectional stretching of nanoparticles. Nanofuids can be used to increase the surface.TisworkisanextensionoftheworkofW.A. thermal conductivity of the fuids and are stable fuids having Khan et al. [16] by considering the gyrotactic microorganisms much better writing, dispersion, and spreading properties in the three-dimensional fow of Oldroyd-B nanofuid. Te on solid surfaces. Choi and Eastman [29] initially presented problem is formulated in terms of governing equations of the idea of suspension of nanoparticles in base fuids. Later, motion with appropriate boundary conditions, which are Buongiorno [30] extended the concept by considering Brow- then transformed into a system of ordinary diferential nian motion and thermophoresis movement of nanoparticles equations using similarity transformations. Te analytical in view of application in hybrid power engine, thermal solution is found using Homotopy Analysis Methods (HAM). management, heat exchanger, domestic refrigerators, etc. Te efects of involved physical parameters on the fow felds Tey have enhanced heat conduction power as compared to are analyzed with the help of graphs. base fuids and are useful in cancer therapy and medicine. With the presentation of a reliable model of nanofuid 2. Problem Formulation given by Buongiorno [30], nanofuids have become a subject of great interest for researchers in the last few decades We have considered the steady, incompressible three- [31–34]. Recently, Nabwey et al. [35] studied the group dimensional fow of an Oldroyed-B nanofuid containing method analysis of mixed convection stagnation-point fow gyrotactic microorganisms past a stretching surface. Te sur- of non-Newtonian nanofuid over a vertical stretching sur- face is maintained at constant temperature ��, the nanopar- face. ticlevolumefraction��, and the number of motile microor- Bioconvection is a phenomenon that is used to describe ganisms ��; the ambient values of temperature, nanoparticle the unstructured pattern and instability produced by the volume fraction, and number of motile microorganisms are microorganisms, which are swimming to the upper part of denoted by �∞, �∞,and�∞, respectively, while the reference a fuid and has a lesser density. Due to swimming upwards, values are by �0, �0,and�0, respectively. Te microorganisms these involved microorganisms such as gyrotactic microor- are taken into the nanofuid to stabilize the nanoparticles due ganisms like algae tend to concentrate in the upper part of the to bioconvection. Te mechanical analog for the Oldroyd- fuid layer, causing unstable top heavy density stratifcation B model and the geometry of the present analysis is shown (see [36]). Nanofuid bioconvection phenomenon describes in Figure 1. Te boundary layer form of the continuity, the unstructured density stratifcation and formation of momentum, energy, nanoparticle concentration, and density patterns due to synchronized interaction of the nanoparticles, of microorganisms for three-dimensional Oldroyd-B fuid is thicker self-propelled microorganisms and buoyancy forces. as follows ([16, 37, 50]): Brownian motion and thermophoresis efect produce the motion of these particles, which is independent of the move- �� �V �� + + =0, (1) ment of motile microorganisms. Tat is why the combined �� �� �� interface of bioconvection and nanofuids becomes signif- 2 2 2 icant for microfuidic appliances. Uddin et al. studied the �� �� �� 2 � � 2 � � 2 � � � + V +� +�1 (� + V +� computational investigation of Stefan blowing and multiple- �� �� �� ��2 �� 2 ��2 slip efects on buoyancy-driven bioconvection nanofuid fow �2� �2� �2� �2� with microorganisms [37] and numerical solutions for gyro- +2�V +2V� +2�� )=] [ tactic bioconvection in nanofuid saturated porous media ���� ���� ���� ��2 with Stefan blowing and multiple slip efects [38]. Diferent �3� �3� �3� �� �2� types of microorganisms, theoretical biconvection models, +� (� + V +� − have been studied [39–51]. 2 ����2 ���� 2 ��3 �� ��2 Mathematical Problems in Engineering 3 �� �2V �� �2� 1 � � � − − )] + [� �(1−� )(� 1 and 2 are the relaxation time and retardation time, � is 2 2 � ∞ �� �� �� �� �� the density of nanofuid, �� is the density of nanoparticles, �� is the density of microorganisms particles, � is the gravity, −�∞)−(�� −��)(�−�∞)−�(�� −��)(� �=(��)�/(��)� is the heat capacity ratio, �� and �� are the stretching velocities, �, � > 0 are the stretching rate, and � ,� ,� −�∞)] g, 1 1 1 are the