Investigation of Mixed Convection in a Lid-Driven Cavity with Sidewall Heating

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Investigation of Mixed Convection in a Lid-Driven Cavity with Sidewall Heating

ارائه دهنده: Provider: Morteza Nazarpour

اساتید راهنما: Supervisors: Dr. Mohammad Saeid Aghighi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: dr.habibAllah saye vand, dr amireh nourbakhsh

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: 51

چکیده: Abstract: Mixed convection in cavities with moving lids is an important problem in mechanical engineering and thermal sciences because of its role in heat transfer systems. This phenomenon arises from the interaction between natural convection induced by temperature differences and forced convection generated by lid motion, and it can significantly affect flow structure and heat transfer. Because many fluids used in industrial processes exhibit non-Newtonian behavior, their thermal and hydrodynamic characteristics warrant particular attention. In this study, mixed convection of a Casson viscoplastic fluid is investigated in a two-dimensional square cavity with a moving upper lid and sidewall heating. The left wall is heated, the right wall is cooled, and the horizontal walls are thermally insulated. Steady, laminar, incompressible flow is assumed, and buoyancy is modeled using the Boussinesq approximation. The zero-Bingham-number case is considered the Newtonian reference, and the effects of varying the Bingham number on flow behavior and heat transfer are examined. The governing equations are solved for Reynolds numbers of Re = 1, 10, and 100 and Richardson numbers of Ri = 0.1, 1, and 10. The mass, momentum, and energy conservation equations are discretized using the Galerkin finite element method (GFEM) with nine-node Lagrangian quadrilateral elements (Q9). The resulting nonlinear system is solved using the Newton–Raphson algorithm in an in-house MATLAB code. The results are analyzed in terms of streamlines, temperature contours, temperature profiles along the horizontal centerline, and variations in the average Nusselt number at the hot wall. The results show that increasing the Bingham number strengthens yield-stress effects and changes the distribution of unyielded regions within the cavity. It also reduces the average Nusselt number at the hot wall, indicating a smaller convective contribution to heat transfer. Over the investigated parameter range, increases in the Reynolds and Richardson numbers are accompanied by changes in vortex structure, deformation of isotherms, and an increase in the average Nusselt number. The temperature profiles further show that the influence of the Bingham number extends beyond reduced heat transfer to changes in the temperature distribution and thermal-field structure. These findings highlight the importance of the rheological behavior of Casson fluids in the thermal performance of lid-driven cavities and the need to account for this behavior when designing and optimizing thermal systems involving viscoplastic fluids.