Research Article Study of Triangular Fuzzy Hybrid Nanofluids on the Natural Convection Flow and Heat Transfer between Two Vertical Plates Muhammad Nadeem, 1 Ahmed Elmoasry, 2 Imran Siddique , 1 Fahd Jarad , 3,4 Rana Muhammad Zulqarnain , 5 Jawdat Alebraheem , 2 and Naseer S. Elazab 6 1 Department of Mathematics, University of Management and Technology, Lahore 54770, Pakistan 2 Department of Mathematics, College of Science Al Zufli, Majmaah University, Majmaah 11952, Saudi Arabia 3 Department of Mathematics, Cankaya University, Etimesgut, Ankara, Turkey 4 Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan 5 Department of Mathematics, University of Management and Technology, Lahore, Sialkot Campus, Pakistan 6 Department of Mathematics, Faculty of Science, Cario University, Giza, Egypt Correspondence should be addressed to Fahd Jarad; fahd@cankaya.edu.tr Received 3 September 2021; Revised 22 September 2021; Accepted 27 September 2021; Published 11 November 2021 Academic Editor: Ahmed Mostafa Khalil Copyright © 2021 Muhammad Nadeem et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e prime objective of the current study is to examine the effects of third-grade hybrid nanofluid with natural convection utilizing the ferro-particle (Fe 3 O 4 ) and titanium dioxide (TiO 2 ) and sodium alginate (SA) as a host fluid, flowing through vertical parallel plates, under the fuzzy atmosphere. e dimensionless highly nonlinear coupled ordinary differential equations are computed adopting the bvp4c numerical approach. is is an extremely effective technique with a low computational cost. For validation, it is found that as the volume fraction of (Fe 3 O 4 + TiO 2 ) hybrid nanoparticles rises, so does the heat transfer rate. e current and existing results with their comparisons are shown in the form of the tables. e present findings are in good agreement with their previous numerical and analytical results in a crisp atmosphere. e nanoparticles volume fraction of Fe 3 O 4 and TiO 2 is taken as uncertain parameters in terms of triangular fuzzy numbers (TFNs) [0, 0.05, 0.1]. e TFNs are controlled by α − cut and the variability of the uncertainty is studied through triangular membership function (MF). 1. Introduction Researchers have been attracted by natural convection (NC) flow because of its numerous uses in engineering and sci- entific problems like heat exchangers, building ventilation, insulation, solar energy collection, refrigeration, nuclear waste repositories, petroleum reservoirs geothermal systems, and chemical catalytic reactors. Convection is used signif- icantly in the manufacturing of solar panels, microstructures during the cooling of molten metals, and free air cooling without the need for fans in real-world applications. Various researchers have looked into the NC-based flow of non- Newtonian and Newtonian fluids between two infinite parallel vertical plates such as Bruce and Na [1] who in- vestigated the heat transfer of NC between vertical flat plates using non-Newtonian Powell–Eyring fluids. Later on, Rajagopal and Na [2] studied the extensive thermodynamic analysis on fundamental functions. e influences of the third-grade non-Newtonian fluid on heat transfer (HT) were examined by Ziabakhsh and Domairry [3] through the homotopy analysis method (HAM). Using the least square method (LSM), Maghsoudi et al. [4] inspected the NC flow of third-grade fluid between two infinite vertical flat plates with a porous media. Mansoor et al. [5] studied the natural convective flow between two vertical plates with the help of the volume of parameter method (VPM) and Runge–Kutta method (RKM). ey show that VPM is better than RKM. Some researchers have explored different flows of fluids between vertical parallel plates analytically and numerically [6, 7]. Hindawi Computational Intelligence and Neuroscience Volume 2021, Article ID 3678335, 15 pages https://doi.org/10.1155/2021/3678335