牛！高產(chǎn)棉花糖機(jī)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(shí)候,女盆友經(jīng)?？匆娒藁ㄌ遣环?誰知道生產(chǎn)棉花糖的機(jī)器,里面可是有大學(xué)問!

棉花糖機(jī)器的中央部位是一個(gè)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(dāng)糖在加熱腔中高速旋轉(zhuǎn)的時(shí)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(guó)棉花糖流行于大街小巷的時(shí)候,國(guó)外已經(jīng)有人對(duì)這種機(jī)器進(jìn)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(qǐng)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(duì)轉(zhuǎn)子定子混合器(Rotor-Stator Mixer)進(jìn)行詳細(xì)研究。首先我們先看幾何模型:

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

預(yù)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(jìn)行了加密。模擬的機(jī)器CPU為8核XEON處理器,內(nèi)存為512G。

牛！高產(chǎn)棉花糖機(jī)器，CFD來幫你！【轉(zhuǎn)發(fā)】ansys結(jié)果圖片3

網(wǎng)格示意圖,每個(gè)齒的黑影部分為加密區(qū)域

模擬首先采用MRF穩(wěn)態(tài)計(jì)算,大約用了2天。然后采用滑移網(wǎng)格法,每時(shí)間步旋轉(zhuǎn)0.1度。非穩(wěn)態(tài)計(jì)算也大約使用了2-3天。梯度計(jì)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(jiǎn)要結(jié)果:

牛！高產(chǎn)棉花糖機(jī)器，CFD來幫你！【轉(zhuǎn)發(fā)】ansys結(jié)果圖片4

6000rpm的徑向速度矢量圖

6000rpm的alpha等值面動(dòng)態(tài)圖

結(jié)論:由于較為消耗計(jì)算資源,CFD以及群體平衡模型(PBM)目前很少用于工業(yè)設(shè)計(jì)。因此,對(duì)模型進(jìn)行簡(jiǎn)化并提出基于半經(jīng)驗(yàn)常數(shù)的模型可以用于工業(yè)上的計(jì)算模擬。本文采用單相模型結(jié)合液滴破碎模型進(jìn)行模擬來預(yù)測(cè)轉(zhuǎn)子定子混合器的液滴直徑。相關(guān)模型以及預(yù)測(cè)對(duì)以后類似設(shè)備的設(shè)計(jì)有較好的指導(dǎo)作用。Blah, blah, blah....

CFD界:Janssen and Mayer的研究實(shí)際上是使用CFD對(duì)轉(zhuǎn)子定子混合器進(jìn)行模擬。這種設(shè)備和我們的棉花糖機(jī)器非常的相似。CFDer是否感興趣找個(gè)棉花糖機(jī)器來模擬一下呢?

轉(zhuǎn)自公眾號(hào):CFD界

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