Oscillatory Rayleigh-Bénard Convection in elasto-viscoplastic gels

Abstract Rayleigh-Benard convection (RBC) is studied in an elasto-viscoplastic (EVP) gel, the widely used and studied Carbopol gel. The transition from conductive to convective regime is determined by the Schmidt-Milverton principle which leads to a critical value of the inverse of the Yield number 1 ∕ Y c . However, an oscillatory motion in the gel is observed below 1 ∕ Y c ≈ 60 when smooth and untreated walls are used. Particles within the gel describe periodical loops close to their initial positions for 16 . 5 1 ∕ Y 25 . For larger values of 1 ∕ Y ≈ 50 1 ∕ Y c , loops are still obtained but particles move away progressively from their initial position. The oscillations take the form of periodic traveling waves (TW). We demonstrate that elastic effects play the major role in the occurence of oscillations.