Mixed convective flow stability of nanofluids past a square cylinder by dynamic mode decomposition

• We investigate mixed convective flow stability of nanofluids past a square cylinder by Dynamic mode decomposition.
• A symmetric distribution of most dominant real and complex eigen modes appeared at the critical nanofluid volume fraction.
• Energy content in the Cu-water nanofluids is higher than that of Al-water nanofluids.
• There is a reduction in energy content of higher frequency modes compared to that of most dominant lower frequency mode.

The mixed convective flow stability of nanofluids past a square cylinder is investigated by Dynamic Mode Decomposition (DMD). The energy content in the individual modes for Cu–water nanofluids is found to be higher than that of Al2O3–water nanofluids. DMD results showed the fact that Cu–water nanofluids have more small-scale structures of higher frequency modes compared to that of Al2O3–water nanofluids. The most dominant temporal dynamic mode corresponds to the lower-frequency eigenvalue λ=(0.99374,±0.1117)λ=(0.99374,±0.1117) for Al2O3–water nanofluids and λ=(0.99451,±0.10464)λ=(0.99451,±0.10464) for Cu–water nanofluids. Energy content in the mean flow of the base fluid at Richardson number of −0.5 is found to be maximum compared to that of nanofluids.