Numerical study of nonlinear mixed convection inside stagnation-point flow over surface-reactive cylinder embedded in po
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Numerical study of nonlinear mixed convection inside stagnation‑point flow over surface‑reactive cylinder embedded in porous media Kun Hong1 · Rasool Alizadeh2 · Mostafa Valizadeh Ardalan3 · Amireh Nourbakhsh4 · Nader Karimi5 · Yang Yang6 · Qingang Xiong1,7 Received: 17 December 2019 / Accepted: 28 December 2019 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Nonlinear mixed convection of heat and mass in a stagnation-point flow of an impinging jet over a solid cylinder embedded in a porous medium is investigated by applying a similarity technique. The problem involves a heterogenous chemical reaction on the surface of the cylinder and nonlinear heat generation in the porous solid. The conducted analysis considers combined heat and mass transfer through inclusions of Soret and Dufour effects and predicts the velocity, temperature and concentration fields as well as the average Nusselt and Sherwood number. It is found that intensification of the nonlinear convection results in development of higher axial velocities over the cylinder and reduces the thickness of thermal and concentration boundary layers. Hence, consideration of nonlinear convection can lead to prediction of higher Nusselt and Sherwood numbers. Further, the investigation reveals that the porous system deviates from local thermal equilibrium at higher Reynolds numbers and mixed convection parameter. Keywords Nonlinear mixed convection · Stagnation-point flow · Local thermal non-equilibrium · Nonlinear heat generation · Soret effect · Dufour effect List of symbols a Cylinder radius (m) asf Interfacial surface area per unit volume of the porous medium (m−1) * Qingang Xiong [email protected]; [email protected] 1
National and Local Joint Engineering Research Center for Mineral Salt Deep Utilization, Key Laboratory for Palygorskite Science and Applied Technology of Jiangsu Province, Huaiyin Institute of Technology, Huai’an 223003, China
2
Department of Mechanical Engineering, Quchan Branch, Islamic Azad University, Quchan, Iran
3
Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
4
Department of Mechanical Engineering, Bu-Ali Sina University, Hamedan, Iran
5
School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK
6
Stanley Black & Decker, Inc., Townson, MD 21286, USA
7
IT Innovation Center, General Motors, Warren, MI 48092, USA
Bi Biot number Bi =
hsf asf ⋅a 4kf
C Fluid concentration (kg m−3) Cp Specific heat at constant pressure (J K−1 kg−1) Cs Concentration (kg m−3) D Molecular diffusion coefficient (m2 s−1) C D⋅k Df Dufour number Df = C ⋅Cf T −T∞ 𝜐 s p ( w ∞) f (𝜂) Function related to u-component of velocity f � (𝜂) Normalised velocity related to w component h Heat transfer coefficient (W K−1 m−2) hsf Interstitial heat transfer coefficient (W K−1 m−2) k Thermal conductivity (W K−1 m−2) k̄ Freestream strain rate (s−1) k1 Permeability of the porous medium (m2) km Mass transfer coefficient (m s−1) kR Kinetic constant (kg m−2 s−1) kT Thermal diffusion ratio N ∗
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