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Effects of notch geometry and sharpness on turbulent jets issuing from indeterminate-origin notched nozzles

机译:切口几何形状和清晰度对不确定来源的切口喷嘴发出的湍流射流的影响

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An experimental investigation using hot-wire anemometry to identify the effects of notch configuration and relative sharpness on notched indeterminate-origin turbulent jets at Re = 20,500 was carried out. The notches are characterized by their V- and A-shaped cuts, as well as their relative sharpness due to the design aspect ratio (AR = 2 and 4) of the notch. Regardless of exact notch geometry, high aspect-ratio nozzles are shown to produce significant flow differences between measurements taken along peak and trough planes, in contrast to low aspect-ratio nozzles. Half-jet width results demonstrate that as the aspect-ratio increases, smooth peaks result in a constant increase within the measurement range while sharp peaks produce an initial decrease till some downstream location before increasing thereafter. In contrast, smooth and sharp trough produces significant nonlinear increases in the half-jet widths with the aspect-ratio increment. Cross-over points linked to axis-switching behaviour are observed for all nozzles except AR = A A-notched nozzle, when half-jet widths along peak and trough planes for each nozzle are compared. Increasing the aspect ratio also results in a 50% reduction in the distance away from the nozzle origin where the cross-over point occurs for V-notched nozzles. On the other hand, similar increase in the aspect ratio produces no cross-over point for A-notched nozzles. These results indicate that suitably configured notched nozzles are able to impart significant control over circular jet flow behaviour by inducing and manipulating axis-switching behaviour typically found in noncircular jets.
机译:进行了一项实验研究,使用热线风速仪确定了缺口构型和相对清晰度对Re = 20,500时不确定的起源于湍流的湍流射流的影响。凹口的特征在于其V形和A形切口,以及由于凹口的设计纵横比(AR = 2和4)而引起的相对清晰度。不管确切的缺口几何形状如何,与低纵横比的喷嘴相比,高纵横比的喷嘴显示出在沿峰平面和波谷平面进行的测量之间会产生明显的流量差异。半喷射宽度的结果表明,随着纵横比的增加,平滑的峰会导致测量范围内的恒定增加,而尖锐的峰会导致初始减小,直到某些下游位置,然后才增加。相反,光滑而尖锐的波谷会随着纵横比的增加在半射流宽度上产生明显的非线性增加。当比较每个喷嘴沿峰和谷平面的半喷射宽度时,对于所有喷嘴(除了AR = A形缺口的喷嘴),都观察到与轴切换行为相关的交叉点。增加长宽比还会导致距喷嘴起点的距离减少50%,在该点处,V形喷嘴会出现交叉点。另一方面,纵横比的类似增加不会为A形喷嘴产生交叉点。这些结果表明,适当配置的凹口喷嘴能够通过诱导和操纵通常在非圆形喷嘴中发现的轴转换行为,来对圆形喷嘴的流动行为进行有效控制。

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