Multilayered oesophageal flow in the presence of a balloon catheter: application to achalasia Sanjay Kumar Pandey and Anupam Kumar Pandey Eur. Phys. J. Plus, 140 6 (2025) 572 Published online: 23 June 2025 DOI: 10.1140/epjp/s13360-025-06508-5