Browsing by Subject "Roughness."
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Item Convection from manufactured ice roughness with varying flux boundary conditions.(2014-09-05) Walker, Christopher Wade.; McClain, Stephen Taylor.; Mechanical Engineering.; Baylor University. Dept. of Mechanical Engineering.It is well understood that aircraft wing icing adds weight, increases drag coefficients, decreases lift coefficients, and reduces stall margin, which can lead to aircraft accidents. To predict the shape of these ice accretions, codes, such as the NASA LEWICE code, have been created that step through time and solve an energy balance for an iced airfoil. A critical part of this energy balance is convection over the initial ice roughness. However, determining the convective heat transfer over the initial ice roughness is difficult. Previous methods have been developed for measuring the convective heat transfer for ice roughness with constant thermal boundary conditions. This work investigates the effect of variable heat flux boundary conditions on convective heat transfer, and improves upon the techniques used to obtain convective heat transfer measurements for realistic ice roughness patterns.Item The effect of roughness element thermal conductivity on turbulent convection.(2011-05-12T15:41:42Z) Mart, Steven Robert.; McClain, Stephen Taylor.; Engineering.; Baylor University. Dept. of Mechanical Engineering.Many flows of engineering interest occur over surfaces that exhibit roughness with thermal conductivities much lower than common metals and alloys. This is especially true of in-service gas turbine blades with surface depositions. Depending on the local convection coefficients, low thermal conductivity deposits may create situations where temperature changes along the heights of the elements are important and must be considered in predicting the overall surface convection coefficient. Using four test plates constructed with hexagonal distributions of hemispheres or cones made of either aluminum or ABS plastic, a series of experiments were performed in the Baylor University Subsonic Wind Tunnel to investigate the effects of roughness element thermal conductivities on turbulent convection. Results indicate that the packing density of the elements and the enhancement on the floor of the roughness distribution compete with the roughness element thermal conductivity in determining the overall convection enhancement.