激波沿H_2/空气界面绕圆、方柱强化混合的数值研究

NUMERICAL STUDY ON A MOVING SHOCK DIFFRACTED OVER THE CYLINDER/SQUARE COLUMN IN HYDROGEN AIR MIXTURE

用迎风TVD格式求解二维、层流全N S方程 ,对激波沿H2 和空气界面绕圆、方柱流动及其诱导的剪切混合进行了数值模拟 ,得到了流场的压力和组分密度分布 .计算结果表明 :激波在H2 传播得快 ,剪切层中出现卷吸涡和调节激波 .卷吸涡与柱体撞击后 ,反射出一道激波 ,H2 沿柱体表面向下游扩散 .H2 /空气接触面与柱体分离后 ,形状畸变并产生新的卷吸涡 .H2 分布表明 :在界面上加圆柱或方柱 ,可有效地强化燃料混合 ,方柱的增强效果更明显些 .在圆柱表面 ,H2 、空气中激波均发生由RR向MR的转变 ,两Mach杆在下游相互透射 .对于方柱 ,H2 中激波沿下表面传播几乎不受影响 ,空气中激波沿上表面发生Mach反射 ,其Mach杆和H2 中绕射激波相互透射 .柱体左侧最终形成一脱体激波 ,流场存在激波、卷吸涡、接触面间的相互作用 ,但波系结构相似 .

Upwind TVD scheme is used to solve laminar, 2D fully N\|S equations. A shock diffracted by a cylinder or square cylinder along hydrogen air interface, and mixing enhancement in a shear flow are numerically studied. The results indicate that the shock travels faster in hydrogen. An adjustable shock and a swirling ovrtex appear in the shear region. After the swirling vortex impacts the cylinders, a reflected shock is formed, and hydrogen diffuses downstream in the region near cylinder walls. Contact surfaces are deformed and another vortex is generated. The distribution of hydrogen shows that the mixing is enhanced effectively by inserting cylinders along the interface, expecially for a square cylinder. The transition from RR to MR can be found for shocks traveling both in air and in hydrogen for a cylinder. Two Mach stems will transmit each other at the downstream. But in the case of a square column , the shock is almost not affected along the lower wall but Mach reflection takes place along the upper wall, then a diffracted shock and a Mach stem transmit each other finally. For both cases, the detached shock occurs on the right of cylinders. Similar shock structures arise, and contributions of cylinder shape are eventually forgotten. [