Abstract

The rotating Rayleigh-Bénard convection in the presence of helical force is modeled by a four mode Lorenz model. This model is extended to study how this force affects the onset of Küppers-Lortz (KL) instability. We observed that when S < 3, the critical Taylor number and the critical angle for the onset of KL instability decrease as helical force intensity S increases. This influence of helical force is similar to that obtained in rotating fluid layer under periodic modulation of the rotation rate (Bhattacharjee, 1990). In the range 3 S 14.9246, the system exhibits the reentrant behavior of rolls demonstrating the constructive and destructive role of rotation in the KL instability apparition. In this case, we observed that the application of this force allows the KL instability for small values of Taylor number. In addition, it has been found that there exists a threshold (14.9246) in the magnitude of the helical force that allows suppressing the KL instability in the system for any value of Taylor number.

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