NUMERICAL INVESTIGATION OF FLOW TRANSITION FOR NACA-4412 AIRFOIL USING COMPUTATIONAL FLUID DYNAMICS

ABSTRACT: Numerical investigation of aerodynamics phenomena in the post stall region using Computational Fluid Dynamics is critical task due to the strong vortex dynamics involved. Literatures cited in this filed indicates that the Turbulence models employed in most of the commercial CFD software's will assume the boundary layer around the airfoil as fully turbulent and hence the physical phenomena is wrongly addressed and also this approximation will lead to deviation in results from experimentally measured data in the post stall region. Research in this area concluded that the flow transition (boundary layer transition) from laminar to turbulent around the surface of the airfoil needs to be properly implemented in CFD analysis in order to have a reliable prediction in post stall region. This work aims in predicting the flow transition from laminar to turbulent for flow over NACA4412 airfoil in the incompressible flow regime.CFD analysis methodology involves the use of Mentors Shear Stress Transport Turbulence model(k-ω model)with transitional flow option.CFD analysis results are compared with wind tunnel test data.CFD analysis is also carried out with Spalart allmaras turbulence model which assumes the boundary layer as fully turbulent

Multicentric variant of peripheral ossifying fibroma

Peripheral ossifying fibroma (POF) is a solitary over growth of the gingiva known to arise from the cells of the periodontal ligament. The lesions usually start as a painless overgrowth of the interdental papilla unless associated with trauma and gradually involve the other counter parts of the gingiva. The lesion is more considered to be an inflammatory or reactive process rather than to be neoplastic. Here, the authors present a unique case of multiple POF in a young male adult aged 24 years where surgical excision was carried out quadrant wise. The biopsy specimen from multiple sites revealed similar histopathologic features consistent with POF, but also with the multicentric presentation of POF, which is a unique phenomenon. Multicentric variant of POF is indeed a rare case being only the second case so far which has been documented. Management of such case needs a multidisciplinary approach to prevent the recurrence along with regular long time follow-up

Heat transmission and air flow friction in a solar air heater with a ribbed absorber plate: A computational study

The influence of geometrical parameters of V-symmetry ribs on heat flow and fluid flow characteristics of solar air heater (SAH) rectangular duct with ribbed absorber is investigated theoretically. Fabrication of ribs in repeated artificial protrusions pattern on the absorber surface appears as a simple approach for increasing the solar collectors radiation harnessing capacity. The various characteristics of artificial roughness protrusions include relative roughness height (e/Dh), relative roughness pitch (p/e), and angle of attack of flow (α), and the span of these parameters is determined based on experimental considerations of the device and working circumstances. To measure the improvement in the coefficient of heat transfer and friction factor, the outcomes were correlated to those of a smooth conduit under identical flow characteristics. The greatest increase in Stanton number and friction factor is 1.13 and 1.19 folds that of the smooth SAH duct, correspondingly

Enhancing solar air heater efficiency with 3D cylinder shaped roughness elements

Solar air heaters (SAHs) harness solar radiation to warm the air. This study investigates the efficacy of 3D cylindrical roughness features in enhancing heat transfer and reducing friction losses within SAHs. The configuration involves inline and staggered placement of 3D cylindrical roughness elements beneath the absorber surface. Through ASHRAE standard 93–77 testing, heat transfer and friction factors are examined across various cylinder roughness setups, with parameters such as relative roughness pitch (p/h) and gap (w/h) considered. The channel aspect ratio (W/B) is set at 5, and a relative roughness height (h/D) of 0.06 is maintained and flow Reynolds number (Re) is varied from 3000 to 8000. Regression analysis reveals a significant relationship between heat transfer and friction. Notably, at Re = 7910, p/h = 20, and w/h = 8 for staggered cylinder roughness, average friction factor (fav) increases by 171.3 %, and average nusselt number (Nuav) increases by 69.7 %. Similarly, the efficiency index (η) peaks at 0.8192 with inline roughness at Re = 2969, p/h = 20, and w/h = 8. The introduced 3D cylinder roughness elements disrupt the laminar sub-layer, amplifying convective heat transfer while curbing friction losses. This approach optimizes SAH performance within the studied parameter range, showcasing potential improvements for utilizing solar energy. Experimental results, along with expressions for average friction factor (fav) and average Nusselt number (Nuav), underscore the benefits of cylinder-shaped roughness geometries while maintaining h/D = 0.06. These findings introduce an innovative convective heat transfer method, enhancing SAH efficiency. Furthermore, the anticipated average friction factor (fav) and average Nusselt number (Nuav) values align within error limits of ±6.63 % and ±6.62 %, respectively, with improved regression coefficients indicating the stronger relationship and the influence of independent variables on dependent variables