Microvascular and Macrovascular diseases are serious complications of diabetic mellitus, which significantly affect the life quality of diabetic patients. Quantitative description of the relationship between temperature and blood flow is considerably important for non-invasive detection of blood vessel structural and functional lesions. In this study, thermal analysis has been employed to predict blood flow alterations in a foot and a cubic skin model successively by using a discrete vessel-porous media model and further compared the blood flows in 31 diabetic patients. The tissue is regarded as porous media whose liquid phase represents the blood flow in capillaries and solid phase refers to the tissue part. Discrete vascular segments composed of arteries, arterioles, veins, and venules were embedded in the foot model. In the foot thermal analysis, the temperature distributions with different inlet vascular stenosis were simulated. The local temperature area sensitive to the reduction of perfusion was obtained under different inlet blood flow conditions. The discrete vascular-porous media model was further applied in the assessment of the skin blood flow by coupling the measured skin temperatures of diabetic patients and an inverse method. In comparison with the estimated blood flows among the diabetic patients, delayed blood flow regulation was found in some of diabetic patients, implying that there may be some vascular disorders in these patients. The conclusion confirms the one in our previous experiment on diabetic rats. Most of the patients predicted to be with vascular disorders were diagnosed as vascular complication in clinical settings as well, suggesting the potential applications of the vascular-porous media model in health management of diabetic patients.

This paper presents a continued study on a previously investigated novel winglet-shroud (WS) (or partial shroud) geometry for a linear turbine cascade. Various widths of double-side winglets (DSW) and different locations of a partial shroud are considered. In addition, both a plain tip and a full shroud tip are applied as the datum cases which were examined experimentally and numerically. Total pressure loss and viscous loss coefficients are comparatively employed to execute a quantitative analysis of aerodynamic performance. The effectiveness of various widths (w) of DSW set at 3%, 5%, 7%, and 9% of the blade pitch (p) is numerically investigated. Skin-friction lines on the tip surface indicate that different DSW cases do not alter flow field features including the separation bubble and reattachment flow within the tip gap region, even for the case with the broadest width (w/p = 9%). However, the pressure side extension of the DSW exhibits the formation of separation bubble, while the suction side platform of the DSW turns the tip leakage vortex (TLV) away from the suction surface (SS). Meanwhile, the horse-shoe vortex (HV) near the casing is not generated even for the case with the smallest width (w/p = 3%). As a result, both the tip leakage and the upper passage vortices are weakened and further dissipated with wider w/p in the DSW cases. Larger width of the DSW geometry is indeed able to improve the aerodynamic performance, but only to a slight degree. With the w/p increasing from 3% to 9%, the mass-averaged total pressure loss coefficient over an exit plane is reduced by only 2.61%. Therefore, considering both the enlarged (or reduced) tip area and the enhanced (or deteriorated) performance compared to the datum cases, a favorable width of w/p = 5% is chosen to design the WS structure. Three locations for the partial shroud (linkage segment) are devised, locating them near the leading edge, in the middle and close to the trailing edge, respectively. Results demonstrate that all three cases of the WS design have advantages over the DSW arrangement in lessening the aerodynamic loss, with the middle linkage segment location producing the optimal effect. This conclusion verifies the feasibility of the previously studied WS configuration.

This paper is a continuous study of a previously investigated novel winglet-shroud (WS) tip configuration. Two additional sealing fins are fixed on the WS tip to further reduce tip leakage. This configuration is referred to WS with seals (WSS) tip. Secondary flow structures and total pressure loss coefficients on a transverse plane downstream of the blade trailing edge are measured. Flow in a blade cascade is also numerically simulated to obtain more information of flow fields. Compared with the WS tip, both experimental and numerical results show that the WSS tip can further improve the aerodynamic performance as expected. Relative to the plain tip, the WSS and WS tips can reduce total pressure loss on one plane downstream of the blade trailing edge by 50% and 28%, respectively. This is mainly due to reduced intensity of tip leakage vortex (TLV). For the tip leakage mass flow rate, the WS tip decreases it by 33.6%, while the implement of two additional sealing fins contributes to an extremely high reduction of 88.7%. This demonstrates that the use of sealing fins is effective to control the tip leakage flow and improve flow fields. In addition, a deeper analysis by applying a normalized helicity scheme to identify the evolution of different vortices and by tracing trajectories of the fluid near the tip offers credible supports for results.