论文标题
倾斜对加热肥皂气泡的湍流热对流的影响
The effect of tilt on turbulent thermal convection for a heated soap bubble
论文作者
论文摘要
我们使用直接的数值模拟(DNS)来探索倾斜度对二维湍流热对流的影响,对在其赤道处加热的半肥皂气泡。 $ ra \ in [3 \ times10^6,3 \ times10^9] $,prandlt的数字定为$ pr = 7 $。dns揭示了两个质量不同的流动状态:动态羽流体(DPR)和稳定的羽流体(spr)。在这两个方案中,以一个大型稳定的羽流从气泡的下边缘升起。考虑$ re $,dpr的比例在于$ re \ propto ra^{0.48} $和$ re \ propto ra^{0.53} $,取决于$ ra $和$δ$,而在spr中,缩放率在$ re \ re propto re \ propto ra^0.44} $ ra^$ ra^$ ra^0.455^0.4555555.455555555555555555555555。热能和动能耗散率($ε_{t^{\ prime}} $和$ε_{u^{u^{\ prime}} $在DPR和spr中也非常不同。 $ \logε_{u^{\ prime}} $接近用于小波动的高斯pdf,但在DPR中很大的波动下偏离了高斯。
We use direct numerical simulation (DNS) to explore the effect of tilt on two-dimensional turbulent thermal convection on a half-soap bubble that is heated at its equator.In the DNS, the bubble is tilted by an angle $δ\in[0^{\circ},90^{\circ}]$, the Rayleigh number is varied between $Ra\in[3\times10^6, 3\times10^9]$, and the Prandlt number is fixed at $Pr=7$.The DNS reveals two qualitatively different flow regimes: the dynamic plume regime (DPR) and the stable plume regime (SPR).In the DPR, small dynamic plumes constantly emerge from random locations on the equator and dissipate on the bubble.In the SPR, the flow is dominated by a single large and stable plume rising from the lower edge of the bubble.The scaling behaviour of the Nusselt number $Nu$ and Reynolds number $Re$ are different in these two regimes,with $Nu\propto Ra^{0.3}$ for the DPR and $Nu\propto Ra^{0.24}$ for the SPR. Concerning $Re$, the scaling in the DPR lies between $Re\propto Ra^{0.48}$ and $Re\propto Ra^{0.53}$ depending on $Ra$ and $δ$,while in the SPR, the scaling lies between $Re\propto Ra^{0.44}$ and $Re\propto Ra^{0.45}$ depending on $δ$.The turbulent thermal and kinetic energy dissipation rates ($ε_{T^{\prime}}$ and $ε_{u^{\prime}}$, respectively) are also very different in the DPR and SPR.The probability density functions (PDF) of the normalized $\logε_{T^{\prime}}$ and $\logε_{u^{\prime}}$ are close to a Gaussian PDF for small fluctuations, but deviate considerably from a Gaussian at large fluctuations in the DPR.