The Thesis Presents Numerical Investigation Of Various Aspects Of °Uid °Ow And Heat Transfer From A Heated Blu® Body. The Mathematical Model Is Based On The Coupling Of Navier Stokes Equations And Energy Equation. The Darcy-Brinkman Model Is Used To Formulate The °Ow Problems Through The Porous Layers. A Pressure Correction-Based Iterative Algorithm, Simple, Is Used To Compute The Governing Equations In Their Full Form. We Have Also Used The Vorticity-Stream Function Formulation For Solving Vorticity And Energy Equations Along With The Poisson Equation For Stream Function To Analyze The Axi-Symmetric/ Two-Dimensional °Ow Problems. In Chapter 2, Numerical Study On Mixed Convection Around A Hot Spherical Particle Falling In A Still °Uid Is Made. The Form Of The Wake And The Thermal ¯Eld Is Analyzed For Several Values Of Grashof Number And The Reynolds Number. The Dependence Of Vortex Shedding Frequency And Heat Transfer On The E®Ective Reynolds Number For Mixed Convec- Tion Around A Heated Cylinder Is Investigated In Chapter 3. The Validity Of Correlations Proposed By Several Authors Based On The Experimental Studies Is Investigated. Chapter 4 Deals With The °Ow And Heat Transfer From A Porous Layer Coated Solid Cylinder Placed Horizontally In A Cross-°Ow Due To A Uniform Stream. The Aim Is To Investigate The Heat Transfer Augmentation Through The Inclusion Of A Porous Wrapper. The Porous Layer Is Of Foam Material With High Porosity And Thermal Conductivity. The Mixed Convection Is Studied For Di®Erent Values Of °Ow Parameters Such As Reynolds Number, Grashof Number, Permeability And Thermal Conductivity Of The Porous Material. We Analyzed The Natural Convection Around A Heated Square Structure Placed Within Sediment In Chapter 5. The Sediment Underlies A Clear °Uid/ Air Column. Flow ¯Eld And Heat Transfer Is Analyzed For Di®Erent Values Of The Buried Depth. The Dependency Of °Uid-Sediment Interface Temper- Ature On Buried Depth Is Investigated. In Chapter 6, We Investigate The °Ow Structure And The Conjugate Heat Transfer Due To A Heated Spherical Viscous Droplet Falling In Air. The Mixed Convection E®Ect On The °Ow ¯Eld Is Considered. The Unsteady Planar Laminar Incompressible Viscous °Uid °Ow Past Thin Blades In Sequence, Aligned Or Nearly Aligned Over °At Moving Ground In Two-Dimensional Is Examined Numerically In Chapter 7. Com- Parisons Of The Numerical Results Are Then Made With The Recent Analytical Predictions. Keywords : Buoyancy, Mixed Convection, Heat Transfer, Vortex Shedding, Thermal Plume, Steady/ Unsteady Separation, E®Ective Reynolds Number, Porous Foam, Hill Vortex, E®Ective Thermal Conductivity, Rotorcraft, Slip-Streaming.