Transp Porous Med (2016) 111:681–699 DOI 10.1007/s11242-015-0620-8 Role of Heat Generation/Absorption on Mixed Convection Flow in a Vertical Tube Filled with Porous Material Having Time-Periodic Boundary Condition: Steady-Periodic Regime Basant K. Jha 1 · Deborah Daramola 1 · Abiodun O. Ajibade 1 Received: 7 May 2015 / Accepted: 14 December 2015 / Published online: 18 January 2016 © Springer Science+Business Media Dordrecht 2016 Abstract This paper discusses the hydrodynamic and thermal behaviours of a fully devel- oped mixed convective flow of a viscous incompressible heat generating/absorbing fluid in a vertical tube filled with isotropic porous material having time-periodic boundary condition. The dimensionless governing equations of motion and energy subjected to the Boussinesq approximation and asymmetric heat conditions are solved analytically. Closed-form solutions are expressed in terms of modified Bessel function of first kind. The solutions obtained are graphically represented, and the effects of the dimensionless heat generation/absorption H , the dimensionless frequency  and the Darcy number Da on the fluid flow are investigated. It is discovered that velocity is maximum at two different locations in the flow domain, one near the surface of the tube and another at the axis of the tube. The presence of the heat generation parameter is seen to enhance the temperature distribution and this is reflected as increase in the magnitude of the oscillation dimensionless velocity, whereas in the presence of heat absorption a reversed trend occurs. Keywords Tube · Mixed convection · Darcy · Heat generation/absorption · Porous material · Steady-periodic Nomenclature A(t ) Function of time Da Darcy number f Fanning friction factor B Deborah Daramola debola32000@yahoo.com Basant K. Jha basant777@yahoo.co.uk Abiodun O. Ajibade olubadey2k@yahoo.com 1 Department of Mathematics, Ahmadu Bello University, Zaria, Kaduna, Nigeria 123