title: Exact solutions for unsteady free convection flow over an oscillating plate due to non-coaxial rotation.
abstract: BACKGROUND
  Non-coaxial rotation has wide applications in engineering devices, e.g. in food processing such as mixer machines and stirrers with a two-axis kneader, in cooling turbine blades, jet engines, pumps and vacuum cleaners, in designing thermal syphon tubes, and in geophysical flows. Therefore, this study aims to investigate unsteady free convection flow of viscous fluid due to non-coaxial rotation and fluid at infinity over an oscillating vertical plate with constant wall temperature.
  
  
  METHODS
  The governing equations are modelled by a sudden coincidence of the axes of a disk and the fluid at infinity rotating with uniform angular velocity, together with initial and boundary conditions. Some suitable non-dimensional variables are introduced. The Laplace transform method is used to obtain the exact solutions of the corresponding non-dimensional momentum and energy equations with conditions. Solutions of the velocity for cosine and sine oscillations as well as for temperature fields are obtained and displayed graphically for different values of time (t), the Grashof number (Gr), the Prandtl number ([Formula: see text]), and the phase angle ([Formula: see text]). Skin friction and the Nusselt number are also evaluated.
  
  
  RESULTS
  The exact solutions are obtained and in limiting cases, the present solutions are found to be identical to the published results. Further, the obtained exact solutions also validated by comparing with results obtained by using Gaver-Stehfest algorithm.
  
  
  CONCLUSIONS
  The interested physical property such as velocity, temperature, skin friction and Nusselt number are affected by the embedded parameters time (t), the Grashof number (Gr), the Prandtl number ([Formula: see text]), and the phase angle ([Formula: see text]).
authors.affiliation: Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai, 81310 Johor Bahru, Malaysia.
authors.forename: Ahmad Qushairi
authors.initials: AQ
authors.lastname: Mohamad
authors.affiliation: Basic Engineering Sciences Department, College of Engineering, Majmaah University, P.O. Box 66, Majmaah, 11952 Saudi Arabia.
authors.forename: Ilyas
authors.initials: I
authors.lastname: Khan
authors.affiliation: Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai, 81310 Johor Bahru, Malaysia.
authors.forename: Zulkhibri
authors.initials: Z
authors.lastname: Ismail
authors.affiliation: Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, Skudai, 81310 Johor Bahru, Malaysia.
authors.forename: Sharidan
authors.initials: S
authors.lastname: Shafie
keywords: Free convection; Laplace transform technique; Non-coaxial rotation; Oscillating