Natural convection and flow patterns of Cu–water nanofluids in hexagonal cavity: A novel thermal case study oleh Akram Mohammad, Benhanifia Kada, Brahim Mebarki, Rahmani Lakhdar, Ansari Abu Zaid, Eid Mohamed R., Hussain Syed M., Redouane Fares, Jamshed Wasim, Alraddadi Ibrahim