Precession effects on a liquid planetary core

• 来源期刊: 天文和天体物理学研究
• 年，卷（期）: 2018,（2）
• 页码范围: 115-124
• 页数: 10页
• 语种: 英文
• DOI: 10.1088/1674-4527/18/2/23

摘要

Motivated by the desire to understand the rich dynamics of precessionally driven flow in a liquid planetary core,we investigate,through numerical simulations,the precessing fluid motion in a rotating cylindrical annulus,which simultaneously possesses slow precession.The same problem has been studied extensively in cylinders,where the precessing flow is characterized by three key parameters:the Ekman number E,the Poincaré number Po and the radius-height aspect ratio F.While in an annulus,there is another parameter,the inner-radius-height aspect ratio T,which also plays an important role in controlling the structure and evolution of the flow.By decomposing the nonlinear solution into a set of inertial modes,we demonstrate the properties of both weakly and moderately precessing flows.It is found that,when the precessional force is weak,the flow is stable with a constant amplitude of kinetic energy.As the precessional force increases,our simulation suggests that the nonlinear interaction between the boundary effects and the inertial modes can trigger more turbulence,introducing a transitional regime of rich dynamics to disordered flow.The inertial mode u111,followed by u113 or u112,always dominates the precessing flow when 0.001 ≤ Po ≤ 0.05,ranging from weak to moderate precession.Moreover,the precessing flow in an annulus shows more stability than in a cylinder which is likely to be caused by the effect of the inner boundary that restricts the growth of resonant and non-resonant inertial modes.Furthermore,the mechanism of triadic resonance is not found in the transitional regime from a laminar to disordered flow.