Transportation of particulate suspension in a Newtonian fluid by dilating peristaltic waves in a tube of uniform cross-section: Application to flows in normal oesophagus

In this paper, we investigate the characteristics of the flow behaviour of suspended particles swallowing in a Newtonian fluid through oesophagus. The peristaltic waves travelling along the walls of a circular cylindrical tube are supposed to be progressively dilating. It is observed that the fluid axial velocity exceeds the solid particle velocity almost everywhere. However, at the wall the axial velocity of the fluid is zero due to the no-slip condition imposed on it; but the suspended particulate material has non -zero positive axial velocity. It is further observed that the axial velocity is negative in the regions near maximum occlusions paving way to instantaneous backward flow. It is also concluded that the maximum axial velocity with particulate suspension with non-zero wave number leaves the particle-free fluid with zero wave number behind. Rising volume fraction diminishes pumping performance and also the axial and radial velocities. The results confirm doctor's views to prescribe liquid or food items with lesser solid contents for achalasia patients and also those who suffer from oesophageal stricture and oesophageal tumours. Streamline patterns are altered by changes in flow rates while trapping takes place at high flow rates.