Applications of parabolized stability equation for predicting transition position in boundary layers

The phenomenon of laminar-turbulent transition exists universally in nature and various engineering practice. The prediction of transition position is one of crucial theories and practical problems in fluid mechanics due to the different characteristics of laminar flow and turbulent flow. Two types of disturbances are imposed at the entrance, i.e., identical amplitude and wavepacket disturbances, along the spanwise direction in the incompressible boundary layers. The disturbances of identical amplitude are consisted of one two-dimensional （2D） wave and two three-dimensional （3D） waves. The parabolized stability equation （PSE） is used to research the evolution of disturbances and to predict the transition position. The results are compared with those obtained by the numerical simulation. The results show that the PSE method can investigate the evolution of disturbances and predict the transition position. At the same time, the calculation speed is much faster than that of the numerical simulation.

Ionized gas clouds near the Sagittarius Arm tangent

Radio recombination lines（RRLs） are the best tracers of ionized gas. Simultaneous observations of multi-transitions of RRLs can significantly improve survey sensitivity. We conducted pilot RRL observations near the Sagittarius Arm tangent by using the 65-m Shanghai Tian Ma Radio Telescope（TMRT） equipped with broadband feeds and a digital backend. Six hydrogen RRLs（H96α-H101α）at C band（6289 MHz-7319 MHz） were observed simultaneously toward a sky area of 2°× 1.2° by using on-the-fly mapping mode. These transitions were then stacked together for detection of ionized gas. Star forming complexes G48.6＋0.1 and G49.5-0.3 were detected in the integrated intensity map.We found agreements between our measured centroid velocities and previous results for the 21 known HII regions in the mapped area. For more than 80 cataloged HII region candidates without previous RRL measurements, we obtained new RRL spectra at 30 targeted positions. In addition, we detected 25 new discrete RRL sources with spectral S/N 〉 5σ, and they were not listed in the catalogs of previously known HII regions. The distances for 44 out of these 55 new RRL sources were estimated.

Developing biophilic intermediate spaces for Arctic housing:Optimizing the thermal,visual,and energy performance

Connecting occupants to the outdoor environment and incorporating biophilic design principles are challenging in extreme Arctic climatic conditions.Existing Arctic housing models do not provide efficient thermal and daylight transitions which are essential for the well-being and cultural needs of their occupants.To address these challenges,this research develops free-running biophilic intermediate spaces,integrated into an existing Arctic housing model.Numerical simulation methods are employed to optimize the primary and secondary architectural design variables for 26 case studies of intermediate spaces.Primary variables include volume,transparency ratio,and orientation.Secondary variables include materials and physical adjacency.Temperature,Daylight Factor/Autonomy,and Energy Use are evaluated as performance indicators.Results reveal that free-running intermediate spaces with 6 meters depth and a transparency ratio above 50%provide efficient indoor–outdoor transitions regarding thermal,visual,and energy performance.Such architectural configurations contribute to an approximately 5%reduction in energy consumption within the housing unit compared to the baseline.Opening side windows prevents the risk of overheating during the summer by reducing the average indoor temperature of intermediate spaces by 7°C but increases the overall energy consumption.As a potential alternative to double-glazing,polycarbonate sheets enable efficient thermal performance by increasing the average indoor temperature of intermediate spaces by approximately 15°C during the cold Arctic seasons.Using polycarbonate sheets results in a 16.6%reduction in energy consumption compared to using double-glazing material in intermediate space,and a 26%reduction from the baseline.Research outcomes contribute to efficient indoor–outdoor connections and energy efficiency in Arctic housing.