PERISTALTIC FLOW CHARACTERSTICS OF MAXWELL AND MAGNETOHYDRODYNAMIC FLUIDS IN FINITE CHANNELS: MODELS FOR OESOPHAGEAL SWALLOWING

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This is an attempt to investigate swallowing of a food bolus through oesophagus by modelling it as an unsteady peristaltic transport of Maxwell and magnetohydrodynamic (MHD) fluids in channels of finite length. The walls of the channels are subjected to progressive transverse contraction waves so that the natural oesophageal wall contractions are matched. The analysis is carried out in non-dimensional form by using long wavelength approximations. The expressions for axial and transverse velocities are derived and pressure across a wavelength is estimated. The reflux limit is determined for both the fluids. Mechanical efficiency for MHD fluids is also obtained. Physical interpretations reveal the behaviour of the flows of masticated viscoelastic food materials such as bread, white eggs etc. and saline water that is represented by MHD model in the oesophagus. It is found that fluids represented by Maxwell fluid are more swallow-friendly than Newtonian fluids while normal water is easier to swallow than saline water which is an MHD fluid. It is also revealed that relaxation time, a parameter of Maxwell model, has no effects on local wall shear stress and reflux limit whereas magneto-hydrodynamic parameters make the fluid more prone to flow reversal. It is found that if the transverse magnetic field and the electric conductivity increase, the pumping machinery requires more pressure for pushing the fluid forward. In other words, pumping has to work more efficiently. Finally, it is revealed that the peaks of pressure are identical, in case, an integral number of waves propagate along the channel while the peaks are of unequal size in the non-integral case.