互动科普

A dog’s sniff pulls a plume of fresh scents toward them, which fluid dynamicists say is a technique that could make for better bomb detectors. Christopher Intagliata reports.

狗通过嗅可以吸入新鲜空气，流体力学家们说这可应用于改善炸弹探测器。克里斯托弗·因塔利亚塔报道。

Old Yeller was a great smeller. Dogs in general have superior smelling abilities. They detect dead bodies, illegal drugs and explosives-even cancer. But dogs don’t just have great olfactory gear. Another reason they’re amazing chemical detectors? [sniffing sound] … is the sniff.

老黄狗有着出色的嗅觉。狗通常都有着相当优秀的嗅觉本领。它们可以探测尸体、非法药品、爆炸物，甚至癌症。但是狗并不只是嗅觉本领突出。它们惊人的化学物质探测本领还有其他原因吗？【嗅来嗅去的声音】…还有嗅的行为。

“And it turns out almost every breed of dog does this at 5 Hz. Five times a second.” Matthew Staymates, a mechanical engineer and fluid dynamicist at the National Institute of Standards and Technology. Sniffing, he says, is really a two-part process. “Inspiration, expiration, right? Inhale, exhale, inhale, exhale.” That second part, the exhale, is key.

“研究发现，每个品种的狗嗅频率大约都为5Hz，即每秒5次。”美国国家标准与技术研究所机械工程师和流体力学家马修·斯塔马特斯说。嗅的行为这个过程可分为2步。“吸气，呼气，是吧？吸气、呼气、吸气、呼气。”第二步呼气是关键。

“So when the dog is actively sampling or sniffing on the ground, there is a turbulent air jet that exits each nostril during the exhale phase. Just like when you and I exhale there’s an air jet that comes out of our nostrils. But the dog is down on the ground and those air jets are vectored down and toward its rear. And in the world of fluid dynamics, if I pulse an air jet in one direction I basically pull air with it.” So the dog is creating a pressure differential that effectively pulls new scents toward its nose.

“当狗积极地在地上嗅来嗅去时，呼气时鼻孔会喷出一股气流，就像你我呼气时从鼻孔向外呼出气流。但是因为狗是贴近地面，喷出的空气是向下和向后的。在流体力学中我们可以看到，如果我向一个方向喷出气体，那会推动空气。“所以狗是产生一个压力差让新的气体流入它的鼻子附近。

Staymates and his colleagues discovered that effect using a 3-D-printed model of a Labrador retriever’s nose, which they tested with fluid dynamics equipment. They then outfitted a commercial vapor detector with sniffing nostrils, inspired by the dog nose. And they found that the actively sniffing detector was 16 times better at picking up the scent of explosives, compared to just continuously drawing in air-the usual method. The results are in the journal Scientific Reports. [Matthew E. Staymates et al., Biomimetic Sniffing Improves the Detection Performance of a 3-D Printed Nose of a Dog and a Commercial Trace Vapor Detector]

斯塔马特斯和他的同事们使用一个拉布拉多寻回犬的3D打印模型在流体力学装置中测试，从而发现了这个效应。他们接着将一个商用蒸汽探测器和一个仿照狗鼻子的“探测鼻”结合，这样的探测器比起传统简单持续输入气体的方法，在采集爆炸物气味方面好了16倍。结果发表在期刊《科学报告》上。

Staymates says he hopes next-generation sensors take sniffing seriously. “There’s nanosensors out there that can detect very, very small amounts of materials. One of the things that’s been overlooked: is how do you get the molecules of interest to the detector? So you can have the most sophisticated detector in the world, but unless you can get material to it, it’s not very useful.” Adding a sniffer though…could be just the thing to make those detectors more dogged.

斯塔马特斯说他希望下一代探测器更加重视嗅探。“这些纳米探测器可以探测极其微量的物质。上述研究中最关键的一点是，如何把这些我们感兴趣的分子送到探测器中？所以你可以得到世界上最精确的探测器，但是如果你不能找到被探测物合适的输入方法，这并没什么用。“仅仅添加一个专门的嗅探器，就可以使这些探测器的能力提升一大步。

-Christopher Intagliata