Research on Relaxation Environment and Natural Drying of Food by Using Control of Vortical Fluctuation

本研究着重探讨各种物体所产生的旋涡脉动现象。这种波动可以为人类提供放松。用PIV测量了瞬时速度和涡量的脉动，并对不同模型进行了FFT分析。结果表明，在所有模型中，1/f波动的范围都很大，且波动区间很小。小间距模式产生的涡量较小，大间距模式产生的涡量较大，本研究旨在将模拟自然风的涡流应用于食品干燥，以缩短食品干燥时间。以胡萝卜、甘薯、菠萝和苹果为试验食品，在风洞中进行了恒风速下的食品干燥试验。采用方形圆柱体产生涡流，在涡流的下游放置试验食品。结果表明，旋转脉动流使胡萝卜和甘薯的含水率迅速下降。

This study focuses on the phenomenon of vortex fluctuation generated by various bodies. This fluctuation may provide relaxation for human. The fluctuations of instantaneous velocity and vorticity are measured by PIV and are analyzed by FFT for various models. It is found that 1/f fluctuation occurs in a wide range for small interval of all models. The low vorticity is generated by the small interval models, and the high vorticity is generated by the large interval models.This study aims at applying the vortex flow simulating a natural wind to dry food in order to decrease the time of food drying. The experiment of food drying was performed in a wind tunnel at a constant air velocity, and carrot, sweet potato, pineapple and apple were used as test foods. A square cylinder was adopted to generate vortex flow and test foods were setup at the downstream of vortex flow. It is found that the vortical fluctuation flow decreases the moisture content of carrot and sweet potato quickly.