Experimental investigation of relaminarizing and transitional channel flows

A hot-wire measurement was conducted in a planar channel flow that originated from a strongly disturbed flow in an entrance channel followed by an expansion channel used to reduce the Reynolds number (Re). From ceasing decrease of the streamwise velocity fluctuation energy and the linear extrapolation of the intermittency factor, the lower marginal Re, which is defined as the minimum Re for partial existence of sustainable turbulence, is estimated around 1400 based on the channel width and the bulk velocity. The upper marginal Re at which the intermittency factor reaches one is about 2600. The flow fields passing a turbulent patch were reconstructed with conditional sampling of the streamwise velocity data based on the time of laminar-turbulence interfaces and the reconstructed flow fields indicate a large-scale flow structure across laminar and turbulent parts. This large structure makes it possible for some regions to be at higher Re than the average, so that turbulence can partly survive. The moderate-scale disturbances larger than the turbulent one appear in the non-turbulent parts of the transitional flow, and in these cases the non-turbulent velocity profile is almost identical to the turbulent one. The large-scale fluctuation is observed even over Re = 2600. This leads to the conclusion that a turbulent channel flow close to the upper marginal Re becomes inhomogeneous. (C) 2012 American Institute of Physics. [https://doi.org/10.1063/1.4772065]ArticlePHYSICS OF FLUIDS. 24(12):124102 (2012)journal articl

Effect of expansion coefficient difference between machine tool and workpiece to the thermal deformation induced by room temperature change

9th CIRP Conference on High Performance Cutting (HPC 2020)In the precision machining process, ambient temperature is maintained to 20 °C to minimize the thermal deformations. Much energy is consumed to maintain ambient temperature. The use of thermal compensation systems can minimize the energy consumption of room cooling systems. However, the influence of thermal deformation induced by room temperature upon workpieces is not clear. This paper investigates the effect of the linear expansion coefficient difference between a machine tool and workpieces to the thermal deformation induced by room temperature change. Machining experiments are conducted for steel and aluminum workpieces. The results agree with the calculation

Evaluation of on-machine measuring method for dynamic stiffness of thin-walled workpieces

8th CIRP Conference on High Performance Cutting (HPC 2018)Machining of thin-walled workpieces is a popular issue due to its static and dynamic displacements during machining. It is required to set machining conditions sufficiently considering the vibration characteristics of the workpiece. An automatic on-machine system to measure the dynamic stiffness of the workpiece enables a reliable and frequent measurement. In this study, an on-machine measurement device for workpiece dynamic stiffness is evaluated. The cause of the difference in natural frequency between the on-machine measurement method and impact test is investigated. The influence of the additional mass by a shaker and accelerometer on the natural frequency is investigated using the Rayleigh-Ritz method. A cutting test is conducted to verify whether appropriate cutting conditions can be set from the measurement results of the on-machine dynamic stiffness measurement. The natural frequency difference between the on-machine measurement method and impact test was caused by the additional mass by the contact of the piezoelectric actuator. When the additional mass is 5% or less of the workpiece equivalent mass, the difference in natural frequency was as small as 10 Hz or less. In the cutting test using the workpiece with the sufficiently large mass, the compliance between the on-machine measurement method and impact test was comparable. When the forced vibration was small, the stability limit was correctly estimated from the on-machine dynamic stiffness measurement

Renaturation of the mature subtilisin BPN' immobilized on agarose beads

AbstractWe report here another example of renaturation of subtilisin BPN′(Sbtl) by using an immobilized preparation instead of applying a digestible mutant of Streptomyces subtilisin inhibitor (SSI), a proteinaceous inhibitor of Sbtl [M. Matsubara et al. (1994) FEBS Letters 342, 193–196]. The mature Sbtl was immobilized on agarose beads employing the amino group of the protein. After thorough washing, the immobilized Sbtl was subjected to denaturation in 6 M guanidine hydrochloride (GdnHCl) at pH 2.4 for 4 h, followed by renaturation in 2 M potassium acetate at pH 6.5 for 24 h. This denaturation/renaturation cycle was repeated five times. The recovered activity of the renatured immobilized Sbtl settled at a constant level after the third denaturation/renaturation cycle, demonstrating that almost 100% renaturation was attained by use of the immobilized Sbtl. This immobilized Sbtl preparation could well be utilized for the mechanistic study of protein folding. We then found that 2 M potassium acetate was superior to 2 M potassium chloride as a refolding medium and that the ability of SSI to induce the correct shape of the mature Sbtl was lacking in several refolding media in both thermodynamic and kinetic criteria. Thus the main cause for the increase of refolding yield of Sbtl by coexistence of SSI was prevention of the autolysis of Sbtl

Interplay between Geometry, Fluid Dynamics, and Structure in the Ventricles of the Human Heart

Natural structures conveying fluid flow exhibit an interplay between flow-mediated forces and long-term adaptation. This phenomenon is relevant in the cardiovascular system where the geometric remodelling of the heart chambers is the main mechanism underlying pathological progression leading to hearth failure. Cardiac adaptation is analyzed here in children with a single right ventricle (SRV) in their heart. In these patients, the left ventricle (LV) is not well-developed and the healthy right ventricle (RV) is surgically reconnected, early after birth, to take the functional role of the systemic ventricle. Such a condition represents a special model to investigate cardiac adaptation and this study takes advantage of the availability of an uncommon dataset (64 normal RV, 64 normal LV, 64 SRV with clinically normal function). The ventricular functional performance is analyzed in terms of fluid dynamics and tissue deformation with the objective of verifying to which degree the SRV configuration adapts from the original RV and progresses toward the function of a LV. Results show that SRV immediately assumes a larger volume and a wider geometry due to the higher operating pressure. However, the fluid dynamics is weakly turbulent and produces a reduced propulsion. The surrounding tissue develops muscular thickening with multi-directional orientation of myofibers that mimic a LV. However, the reduced flow performance and a lower structural consistency makes the SRV at higher risk of progressive dysfunctional adaptations. This study demonstrates how the interplay between cardiac flow and tissue response represents the driving macroscopic factor underlying the development of heart failure. More in general, the combined evaluation of fluid dynamics and structural functional properties can be a requirement for the exploration of of the adaptation processes across the different time-scales

Ordering of the Heisenberg Spin Glass in High Dimensions

Ordering of the Heisenberg spin glass with the nearest-neighbor Gaussian coupling is investigated by equilibrium Monte Carlo simulations in four and five dimensions. Ordering of the mean-field Heisenberg spin-glass is also studied for comparison. Particular attention is paid to the nature of the spin-glass and the chiral-glass orderings. Our numerical data suggest that, in five dimensions, the model exhibits a single spin-glass transition at a finite temperature, where the spin-glass order accompanying the simultaneous chiral-glass order sets in. In four dimensions, by contrast, the model exhibits a chiral-glass transition at a finite temperature, not accompanying the standard spin-glass order. The critical region associated with the chiral-glass transition, however, is very narrow, suggesting that dimension four is close to the marginal dimensionality.Comment: 18 pages, 12 figure

Experimental investigation of relaminarizing and transitional channel flows

A hot-wire measurement was conducted in a planar channel flow that originated from a strongly disturbed flow in an entrance channel followed by an expansion channel used to reduce the Reynolds number (Re). From ceasing decrease of the streamwise velocity fluctuation energy and the linear extrapolation of the intermittency factor, the lower marginal Re, which is defined as the minimum Re for partial existence of sustainable turbulence, is estimated around 1400 based on the channel width and the bulk velocity. The upper marginal Re at which the intermittency factor reaches one is about 2600. The flow fields passing a turbulent patch were reconstructed with conditional sampling of the streamwise velocity data based on the time of laminar-turbulence interfaces and the reconstructed flow fields indicate a large-scale flow structure across laminar and turbulent parts. This large structure makes it possible for some regions to be at higher Re than the average, so that turbulence can partly survive. The moderate-scale disturbances larger than the turbulent one appear in the non-turbulent parts of the transitional flow, and in these cases the non-turbulent velocity profile is almost identical to the turbulent one. The large-scale fluctuation is observed even over Re = 2600. This leads to the conclusion that a turbulent channel flow close to the upper marginal Re becomes inhomogeneous. (C) 2012 American Institute of Physics. [https://doi.org/10.1063/1.4772065]ArticlePHYSICS OF FLUIDS. 24(12):124102 (2012)journal articl

Small Intestinal Neuroendocrine Tumour Incidentally Diagnosed Along with Large Mesenteric Lymph Node Metastasis: A Case Report

Small intestinal neuroendocrine tumours (NETs) are rare malignancies that occur in the small intestine. The incidence of small intestinal NETs has increased substantially in recent decades. Similar to that of general NETs, the diagnosis rate of small intestinal NETs is increasing continuously. Small intestinal NETs often metastasize to the lymph nodes, even when the lesions are small. Surgical resection of the primary tumour and associated mesenteric lymph nodes is recommended. We present a case of a NET in the ileum that was incidentally diagnosed along with large mesenteric lymph node metastasis. Abdominal computed tomography for examination of urinary frequency revealed an intra-abdominal mass, measuring 80 mm in diameter. The patient was intraoperatively diagnosed with an ileocaecal mesenteric mass, and ileocaecal resection with lymph node dissection was performed. The resected specimen incidentally showed a NET measuring 14 mm in diameter in the ileum, located 90 cm from the ileocaecal valve. The ileocaecal mesenteric mass was histopathologically diagnosed as lymph node metastasis of the NET. This case confirms the importance of making an immediate intraoperative pathological diagnosis and performing a thorough examination of small intestinal lesions when a large mesenteric tumour is suspected