Multiple-relaxation-time lattice Boltzmann simulation of viscoplastic Bingham nanofluids in a suddenly expanded channel: a systematic numerical study

IF 1.9 4区 物理与天体物理 Q2 PHYSICS, MULTIDISCIPLINARY
Pramana Pub Date : 2024-08-12 DOI:10.1007/s12043-024-02795-2
Muhammad Zawad Mahmud, Md Mahadul Islam, Md Mamun Molla, Md Farhad Hasan, Sadia Siddiqa
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引用次数: 0

Abstract

The multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) is used in a suddenly expanded channel to demonstrate the flow of viscoplastic Bingham nanofluid with Al\(_2\)O\(_3\) nanoparticles. The geometry has two sections namely, inlet and outlet, and the corresponding heights are denoted by h and H, respectively. The length of the entire channel is 20H, and the expanded channel has a height of 16H. The purpose of the MRT-LBM simulation is to investigate the impact of changing the Bingham number (\( 0 \le Bn \le 200\)), keeping the Reynolds number (Re) fixed for different volume fractions (\(\phi =\) 0.00 and 0.04). In addition, the consequences of variations in the Reynolds number (\( 50 \le Re \le 1000 \)) at constant Bingham number (Bn) are also studied for those two different volume fractions. The results demonstrate that with fixed \(Bn=2\), \(Re=400\) is the point where the flow pattern and recirculation regions are exactly the same for both volume fractions. An increase in Re causes the recirculation regions to grow for a fixed Bn for both volume fractions as Re’s rise increases the velocity and decreases the viscous force. Bn’s increment with Re and volume fraction unchanged lowers the recirculation region’s size due to a rise in viscous force. Higher Re and lower Bn cause the more significant recirculation regions to break down into smaller areas. Incrementing the volume fraction lowers size of the recirculation region. An unstable flow was observed for higher Bn (e.g., \(Bn \ge 100\)) and lower Bn (e.g., \(0 \le Bn \le 10\)) when \(Re \ge 500\) for both volume fractions in maximum cases. Unstable flow for lower Bn makes the recirculation regions asymmetric, and when Re is high, the recirculation regions break down for the base fluid (\(\phi =0.00\)). When \(Re=300\) and \(Bn=2\), the length of the recirculation region of the upper wall decreases by \(28.58\%\), and the length of the lower wall falls a bit less by \(26.37\%\) when \(\phi \) is increased from 0.00 to 0.04. For \(x/h=2\), the nanoparticle mixed fluid’s velocity (\(\phi =0.04\)) never gets a negative magnitude till the final position for \(Re=700\). In most situations, an increased volume fraction increases the skin-friction effect on both walls.

Abstract Image

Abstract Image

突然膨胀通道中粘塑性宾汉纳米流体的多重松弛时间晶格玻尔兹曼模拟:系统数值研究
多重松弛时间(MRT)晶格玻尔兹曼法(LBM)被用于一个突然扩大的通道中,以演示含有Al(_2\)O(_3\)纳米颗粒的粘性宾汉纳米流体的流动。几何形状有两个部分,即入口和出口,相应的高度分别用 h 和 H 表示。整个通道的长度为 20H,扩展通道的高度为 16H。MRT-LBM 模拟的目的是研究在雷诺数(Re)固定的情况下,改变宾汉数(0 \le Bn \le 200\)对不同体积分数(\(\phi =\) 0.00 和 0.04)的影响。此外,还研究了在宾汉数(Bn)不变的情况下,雷诺数(50 \le Re \le 1000 \)的变化对这两种不同体积分数的影响。结果表明,在固定(Bn=2)的情况下,(Re=400)是两个体积分数的流动模式和再循环区域完全相同的点。在两个体积分数的 Bn 都固定的情况下,Re 的增加会导致再循环区域扩大,因为 Re 的增加会提高速度并降低粘性力。在 Re 值和体积分数不变的情况下,Bn 的增加会因粘滞力的增加而减小再循环区域的面积。更高的 Re 值和更低的 Bn 值会使更大的再循环区域缩小。增加体积分数会减小再循环区域的面积。在最大情况下,当两种体积分数都为\(Re \ge 500\) 时,较高 Bn(例如,\(Bn \ge 100\) )和较低 Bn(例如,\(0 \le Bn \le 10\) )的流动不稳定。较低Bn的不稳定流动使得再循环区域不对称,当Re较高时,基本流体的再循环区域破裂(\(\phi =0.00\))。当(Re=300)和(Bn=2)时,当(phi)从0.00增加到0.04时,上壁的再循环区域长度减少了(28.58%),下壁的长度减少了(26.37%)。对于(x/h=2),纳米粒子混合流体的速度((\phi =0.04))直到(Re=700)的最终位置都不会变为负值。在大多数情况下,体积分数的增加会增加两面壁的集肤摩擦效应。
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来源期刊
Pramana
Pramana 物理-物理:综合
CiteScore
3.60
自引率
7.10%
发文量
206
审稿时长
3 months
期刊介绍: Pramana - Journal of Physics is a monthly research journal in English published by the Indian Academy of Sciences in collaboration with Indian National Science Academy and Indian Physics Association. The journal publishes refereed papers covering current research in Physics, both original contributions - research papers, brief reports or rapid communications - and invited reviews. Pramana also publishes special issues devoted to advances in specific areas of Physics and proceedings of select high quality conferences.
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