Turbulent channel flow of an elastoviscoplastic fluid
Turbulent channel flow of an elastoviscoplastic fluid
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DOI：
10.1017/jfm.2018.591
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发表时间：
2018-07
影响因子：
3.7
通讯作者：
M. Rosti;D. Izbassarov;O. Tammisola;S. Hormozi;L. Brandt
中科院分区：
文献类型：
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作者：
M. Rosti;D. Izbassarov;O. Tammisola;S. Hormozi;L. Brandt
本文对弹粘塑性流体的层流和湍流槽道流动进行了数值模拟。非牛顿流动通过求解完全不可压Navier-Stokes方程和弹粘塑性应力张量的演化方程来模拟。层流模拟进行了广泛的雷诺数，宾汉数和比的流体和总粘度，而湍流模拟进行固定的体积雷诺数等于2800和弱弹性。我们表明，在层流状态下的摩擦系数单调增加与宾汉数（屈服应力）和粘度比减小，而在湍流状态下的摩擦系数几乎是独立的粘度比和宾汉数减小，直到流最终返回到一个充分的层流条件足够大的屈服应力。三个主要制度被发现在湍流的情况下，取决于宾汉数：对于低的值，摩擦雷诺数和湍流的统计只有轻微的不同，从牛顿流体;对于中间值的宾汉数，波动增加和惯性平衡范围丢失。最后，对于更高的值，流动完全分层。这些不同的行为与流体不屈服的体积的逐渐增加有关，随着宾汉数的增加，从中心线向壁生长。未屈服区域与近壁结构相互作用，优先在高速条纹上方形成。特别是，近壁条纹和相关的准流向涡强烈增强在一个高度弹粘塑性流体和流动变得更加相关的流向方向。
We present numerical simulations of laminar and turbulent channel flow of an elastoviscoplastic fluid. The non-Newtonian flow is simulated by solving the full incompressible Navier–Stokes equations coupled with the evolution equation for the elastoviscoplastic stress tensor. The laminar simulations are carried out for a wide range of Reynolds numbers, Bingham numbers and ratios of the fluid and total viscosity, while the turbulent flow simulations are performed at a fixed bulk Reynolds number equal to 2800 and weak elasticity. We show that in the laminar flow regime the friction factor increases monotonically with the Bingham number (yield stress) and decreases with the viscosity ratio, while in the turbulent regime the friction factor is almost independent of the viscosity ratio and decreases with the Bingham number, until the flow eventually returns to a fully laminar condition for large enough yield stresses. Three main regimes are found in the turbulent case, depending on the Bingham number: for low values, the friction Reynolds number and the turbulent flow statistics only slightly differ from those of a Newtonian fluid; for intermediate values of the Bingham number, the fluctuations increase and the inertial equilibrium range is lost. Finally, for higher values the flow completely laminarizes. These different behaviours are associated with a progressive increases of the volume where the fluid is not yielded, growing from the centreline towards the walls as the Bingham number increases. The unyielded region interacts with the near-wall structures, forming preferentially above the high-speed streaks. In particular, the near-wall streaks and the associated quasi-streamwise vortices are strongly enhanced in an highly elastoviscoplastic fluid and the flow becomes more correlated in the streamwise direction.