论文标题
使用同时的速度和密度场的锁交换重力电流的能量和混合效率
Energetics and mixing efficiency of lock-exchange gravity currents using simultaneous velocity and density fields
论文作者
论文摘要
针对一系列雷诺数字进行了一系列有关锁 - 交换设施中能源保存重力电流的实验实验，$ re = \ frac {u_fh}ν= $ 485-12270。使用PIV-PLIF系统同时捕获速度和密度场。采用移动平均方法来计算平均场和大量湍流统计数据，即动荡的动能（$ K $），剪切生产（$ p $），浮力通量（$ b $）和能量消散（$ε$）（$ε$）。 The subsequent findings are used to ascertain the quantitative values of mixing efficiency, $Ri_{f}$, Ozmidov length-scale ($L_O$), Kolmogorov length-scale ($L_κ$), and eddy diffusivities of momentum ($κ_m$) and scalar ($κ_ρ$). $ ri_ {f} $的两种不同形式在这项研究中表征，由$ ri_ {f}^i = \ frac {b} {p} {p} $和$ ri_ {f}^{ii} = \ frac {b} {b} {b+ε} $。结果涵盖了整个扩散性制度（3 $ <re_b <$ 10）和一部分中间政权（10 $ <re_b <$ 50），其中$ re_b = \fracε{νn^2} $是浮力reynolds数量，可以测量剪切的涡轮上的涡轮级水平。 $ p $，$ b $和$ε$的值在环境流体和电流的接口上显示出明显增加，这是由于剪切驱动的混合层的开发。根据湍流统计和长度尺度的变化，可以推断出湍流沿电流的长度衰减。混合效率单调地提高了扩散状态（$ re_ {b} <$ 10），并且发现具有$ ri_ {f}^{i} \ $ 0.15和$ ri_ {f}^ii}^{ii}^{II} \ of $ 0.2的上限。使用$ ri_ {f} $的值，动量的归一化涡流扩散率被称为$ \ frac {κ_M} {ν.Ri_{g}} $ = 1.2 $ re_ {b} $，$ \ freac $ \ frac {$ re________2 $ re______2 $ re_ {b} $
A series of laboratory experiments on energy conserving gravity currents in a lock-exchange facility are conducted for a range of Reynolds numbers, $Re= \frac{U_Fh}ν =$ 485-12270. The velocity and density fields are captured simultaneously using a PIV-PLIF system. A moving average method is employed to compute the mean field and a host of turbulence statistics, namely, turbulent kinetic energy ($K$), shear production ($P$), buoyancy flux ($B$), and energy dissipation ($ε$) during the slumping phase of the current. The subsequent findings are used to ascertain the quantitative values of mixing efficiency, $Ri_{f}$, Ozmidov length-scale ($L_O$), Kolmogorov length-scale ($L_κ$), and eddy diffusivities of momentum ($κ_m$) and scalar ($κ_ρ$). Two different forms of $Ri_{f}$ are characterized in this study, denoted by $Ri_{f}^I=\frac{B}{P}$ and $Ri_{f}^{II}=\frac{B}{B+ε}$. The results cover the entire diffusive regime (3 $<Re_b<$ 10) and a portion of the intermediate regime (10 $<Re_b<$ 50), where $Re_b=\fracε{νN^2}$ is the buoyancy Reynolds number that measures the level of turbulence in a shear-stratified flow. The values of $P$, $B$, and $ε$ show a marked increase at the interface of the ambient fluid and the current, owing to the development of a shear-driven mixed layer. Based on the changes in the turbulence statistics and the length scales, it is inferred that the turbulence decays along the length of the current. The mixing efficiency monotonically increases in the diffusive regime ($Re_{b}<$10), and is found to have an upper bound of $Ri_{f}^{I}\approx$ 0.15 and $Ri_{f}^{II}\approx$ 0.2 in the intermediate regime. Using the values of $Ri_{f}$, the normalized eddy diffusivity of momentum is parameterized as $\frac{κ_m}{ν.Ri_{g}}$=1.2$Re_{b}$ and normalized eddy diffusivity of scalar as $\frac{κ_ρ}ν$=0.2$Re_{b}$
