Investigation of thermal resistance and bridging in examples of contemporary and vernacular solid wall architecture

Contemporary architecture has tended to increase envelope insulation levels in an unceasing effort to reduce U-values. Traditional masonry architecture in contrast was devoid of insulation, except for the inherent insulative nature of vernacular materials. Also the consistency of the outer membrane of the building skin diminished any impact due to bridging. In contemporary highly insulated walls bridges are numerous due to the necessity to bind inner and outer structural skins through insulation layers. This paper examines thermal bridging in an example of contemporary façade design and compares it with an example of traditional vernacular architecture currently being researched which is characterized by a lack of bridging elements. Focus is given to heavy weight materials of high thermal mass, which appropriately for passive architecture help moderate fluctuations in internal temperature. In an extensive experimental study samples of highly insulated precast concrete sandwich panels and lime rendered masonry walls are tested in a guarded hot-box. The building construction methods are compared for static and dynamic thermal transmittance, via heat flux and surface temperature differential measurements. Focus is given to the differential heat loss due to the thermal bridging in the sandwich panels and its associated impact on overall heat loss relative to traditional masonry construction.

Slot width augmentation in a slotted-wall transonic linear cascade wind tunnel

Transonic tests in linear cascade wind tunnels can suffer
from significant test section boundary interference effects in pitch. A slotted tailboard has been designed and optimised with an in-house Euler numerical method to reduce such ef- fects. Wind tunnel measurements on an overspeed Mach 1.27 discharge from a Rolls-Royce T2 cascade, featuring strong end-wall shock-induced interference, showed a 77% reduction in the flow pitchwise periodicity error with the optimised tail- board, with respect to the baseline open-jet cascade flow. Two-dimensional Euler predictions were also cross-validated against a three-dimensional Reynolds averaged computation, to explore the three-dimensionality of the discharge

Effective end wall profiling rules for a highly loaded compressor cascade

This paper presents a numerical study of a linear compressor cascade to investigate the effective end wall profiling rules for highly-loaded axial compressors. The first step in the research applies a correlation analysis for the different flow field parameters by a data mining over 600 profiling samples to quantify how variations of loss, secondary flow and passage vortex interact with each other under the influence of a profiled end wall. The result identifies the dominant role of corner separation for control of total pressure loss, providing a principle that only in the flow field with serious corner separation does the does the profiled end wall change total pressure loss, secondary flow and passage vortex in the same direction. Then in the second step, a multi-objective optimization of a profiled end wall is performed to reduce loss at design point and near stall point. The development of effective end wall profiling rules is based on the manner of secondary flow control rather than the geometry features of the end wall. Using the optimum end wall cases from the Pareto front, a quantitative tool for analyzing secondary flow control is employed. The driving force induced by a profiled end wall on different regions of end wall flow are subjected to a detailed analysis and identified for their positive/negative influences in relieving corner separation, from which the effective profiling rules are further confirmed. It is found that the profiling rules on a cascade show distinct differences at design point and near stall point, thus loss control of different operating points is generally independent.