牛！高產(chǎn)棉花糖機器，CFD來幫你！【轉(zhuǎn)發(fā)】

2017-02-24 by:CAE仿真在線來源:互聯(lián)網(wǎng)

想必大家出門逛街的時候,女盆友經(jīng)常看見棉花糖不放,誰知道生產(chǎn)棉花糖的機器,里面可是有大學問!

棉花糖機器的中央部位是一個溫度很高的加熱腔,通過加熱將糖變成了糖漿。加熱腔中有一些很小的孔。當糖在加熱腔中高速旋轉(zhuǎn)的時候,離心力將糖漿從小孔中噴射到“大碗”的附近。在逃脫縫隙之后,糖漿遇冷凝固。這些熱腔中的小孔直徑很小,從小孔中噴射出來的糖漿馬上就凝聚成固態(tài)的糖絲,就形成棉花糖了!

在我國棉花糖流行于大街小巷的時候,國外已經(jīng)有人對這種機器進行研究了,并且是逆天的CFD研究!糖絲的直徑如何?要旋轉(zhuǎn)多塊才行?

超屌!服了!

請下文作者收下我的膝蓋

Computational fluid dynamics (CFD)-based droplets size estimates in Emulsificaiton Equipment

J. Janssen, R.Mayer. Processes[J]. 2016, 4(50)

Abstract: While academic literature shows steady progress in combining multi-phase computational fluid dynamics (CFD) and population balance modelling (PBM) of emulsification processes, the computational burden of this approach is still too large for routine use in industry. The challenge, thus, is to link a sufficiently detailed flow analysis to the droplet behavior in a way that is both physically relevant and computationally manageable. In this research article we propose the use of single-phase CFD to map out the local maximum stable droplet diameter within a given device, based on well-known academic droplet break-up studies in quasi-steady 2D linear flows. The results of the latter are represented by analytical correlations for the critical capillary number, which are valid across a wide viscosity ratio range. Additionally, we suggest a parameter to assess how good the assumption of quasi-steady 2D flow is locally. The approach is demonstrated for a common lab-scale rotor-stator device (Ultra-Turrax, IKA-Werke GmbH, Staufen, Germany). It is found to provide useful insights with minimal additional user coding and little increase in computational effort compared to the single-phase CFD simulations of the flow field, as such. Some suggestions for further development are briefly discussed.

在這一篇文章中,Janssen and Mayer通過CFD來對轉(zhuǎn)子定子混合器(Rotor-Stator Mixer)進行詳細研究。首先我們先看幾何模型:

牛！高產(chǎn)棉花糖機器，CFD來幫你！【轉(zhuǎn)發(fā)】ansys結果圖片2
轉(zhuǎn)子、定子以及轉(zhuǎn)配圖

預處理:流變模型為牛頓流體。軟件為ANSYS Fluent 15。CFD網(wǎng)格分為三部分:轉(zhuǎn)子、定子、以及外圍的區(qū)域。Ko的碩士論文中表示轉(zhuǎn)子縫隙中的網(wǎng)格非常重要。因此這一部分的網(wǎng)格被進行了加密。模擬的機器CPU為8核XEON處理器,內(nèi)存為512G。

牛！高產(chǎn)棉花糖機器，CFD來幫你！【轉(zhuǎn)發(fā)】ansys結果圖片3

網(wǎng)格示意圖,每個齒的黑影部分為加密區(qū)域

模擬首先采用MRF穩(wěn)態(tài)計算,大約用了2天。然后采用滑移網(wǎng)格法,每時間步旋轉(zhuǎn)0.1度。非穩(wěn)態(tài)計算也大約使用了2-3天。梯度計算采用基于網(wǎng)格單元的最小二乘法,壓力速度耦合采用PISO算法。

簡要結果:

牛！高產(chǎn)棉花糖機器，CFD來幫你！【轉(zhuǎn)發(fā)】ansys結果圖片4

6000rpm的徑向速度矢量圖

6000rpm的alpha等值面動態(tài)圖

結論:由于較為消耗計算資源,CFD以及群體平衡模型(PBM)目前很少用于工業(yè)設計。因此,對模型進行簡化并提出基于半經(jīng)驗常數(shù)的模型可以用于工業(yè)上的計算模擬。本文采用單相模型結合液滴破碎模型進行模擬來預測轉(zhuǎn)子定子混合器的液滴直徑。相關模型以及預測對以后類似設備的設計有較好的指導作用。Blah, blah, blah....

CFD界:Janssen and Mayer的研究實際上是使用CFD對轉(zhuǎn)子定子混合器進行模擬。這種設備和我們的棉花糖機器非常的相似。CFDer是否感興趣找個棉花糖機器來模擬一下呢?

轉(zhuǎn)自公眾號:CFD界

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