This paper reports on a numerical simulation of circumferential groove Casing Treatment in a high-speed axial fan. Four circumferential grooves of the same geometry are located over the tip of a NASA Rotor-67 and unsteady calculations are performed from choke to near-stall. Results show that circumferential grooves reduce the incidence angle near the pressure surface at the blade leading-edge. Furthermore, the passage shock and the leakage flow are pushed rearward in the passage. It is found that circumferential grooves increase the momentum in the streamwise direction (fluid is absorbed by the grooves from their downstream part and is injected from their upstream section). The grooves also provide a flow path between the suction and pressure surface, leading to a reduction in the pressure difference between them. At the near-stall point the flow field near the grooves was found to be highly unsteady. Maximum unsteadiness was observed in the first upstream groove: the circulated mass flow rate changed as high as roughly 30 percent of its time-averaged value. As a result, in order to simulate circumferential groove Casing Treatment in compressors, unsteady computations are required.

Time-accurate numerical calculations are performed to investigate the effect of air recirculation on NASA Rotor 37. An annular Casing-mounted recirculation passageway is designed and located over the blades. Because the investigated rotor does not have any stator, the bleed air has a high circumferential velocity component (in the same direction of the rotor). Therefore, the injected air would have a high swirl component, reducing the injection's effectiveness. As a result, anti-swirl blades have been installed within the recirculation duct, to reduce flow swirl and improve injector effectiveness. Different anti-swirl vanes have been simulated in order to determine the best vanes in terms of minimum pressure loss and zero injection yaw angle (axial injection). Results show that these vanes can effectively turn the circulated fluid to the axial direction and provide a high velocity axial injection upstream of the rotor blades. As a result of the effective injection, the leakage flow moves downstream, improving stability by shifting the stalling point to lower mass flow rates. Because the injection port is close to the blade, the interaction of the passage shock and the injection port causes unsteadiness in the injection mass flow, which is discussed in the paper.

In this paper, the influence of a shallow reversed slot-type Casing Treatment on the performance of a tip-critical transonic compressor has been numerically investigated. Firstly, the complex flow fields in the rotor tip region are studied in details. It shows the severe blockage induced by suction surface boundary separation triggers compressor stall at 100% design speed, while the blockage due to tip leakage vortex dominates at 80% design speed. Secondly, the mechanism of stability extension is presented at different rotating speeds. The Casing Treatment alleviates greatly the tip blockage by manipulating the tip leakage flow, accompanied by the redistribution of aerodynamic loading and mass flux. As a result, the Casing Treatment is more efficient for the blockage induced by tip leakage vortex (at 80% design speed). Further analysis of the pressure field and passage shock distribution demonstrates that the passage shock intensity and its location will affect the effectiveness of Casing Treatment. Finally, the instability characteristics of compressor with Casing Treatment are revealed. The numerical results reflect when the mass flow approaching the instability boundary, the stator passage blockage presumably is dominant for triggering the compressor stall.

Purpose: The aim of this study was to compare higher-order aberrations between personalized Treatment (PT) versus personalized Treatment advanced (PTA) photorefractive keratectomy (PRK) for myopia and myopic astigmatism.Methods: In this clinical trial, 80 eyes of 40 patients who met inclusion criteria were enrolled. They underwent PRK using PT or PTA algorithm randomly. Higher-order aberrations were measured and compared between the study groups pre-operatively and at months 3 and 6 postoperatively.Results: The two study groups were comparable in terms of preoperative higher-order aberrations.Compared to the preoperative values, higher-order aberrations were significantly increased in the PT group (p<0.001), but decreased in the PTA group (p<0.001). Spherical aberration exhibited a significant increase postoperatively in the PT group (p<0.001) but remained unchanged in the PTA group (P=0.57).Conclusion: PRK using PT algorithm resulted in an increase higher-order aberrations. PTA algorithm provided better results in terms of postoperative higher-order aberrations and could treat pre-existing higher-order aberrations.

Maximum pressure ratio and aerodynamic blades loading are the most important factors in designing axial compressor restricted by minimum airflow. The present work aims to stall margin and total pressure ratio in transonic axial compressor using circumferential groove Casing Treatment (CGCT). In the first step, untreated compressor was simulated, compared, and agreed well with the experimental data. Then the treated rotor was simulated and results indicated that using CGCT improves the stall margin and increases the rotor pressure ratio. Stall margin was improved by 8% and the pressure ratio before stall condition and at the design point increased by 2.6% and 2.8 %, respectively. Additionally, it replaces normal shock with oblique shock near instability, causing less total pressure drop, moreover, the oblique shocks occurrence restricts separation zones and assists the rotor to perform far from instability. Furthermore, axial speed passing through rotor in a certain mass flow increases by 15 m/s, and then kinetic energy and stability increased. However, total efficiency of rotor reduces near 1%. In the last step, engine was analyzed with the aid of cycle analysis and leads to 62kW increase in shaft power as well as 1.87 g/kNs less fuel consumption due to 2.8% increase in the rotor pressure ratio.

Axial slot CTs were designed and applied on Rotor 67 to understand the physical mechanisms responsible for the improvement of the stall margin. Unsteady Reynolds-averaged Navier-Stokes was applied in addition to steady Reynolds-averaged Navier-Stokes to simulate the flow field of the rotor. The results show that aerodynamic performance and the rotor stability were improved. Stall margin improvement (SMI) improved by 26. 85% after the CT covering 50% of the axial tip chord was applied, whereas peak efficiency (PE) decreased the least. The main reason for the rotor stall in the solid Casing is the blockage caused by tip leakage flow. After axial slot CTs were applied, the tip leakage flow in the front part of the chord was obviously reduced, and the majority of the blockages in the tip region were removed. The absolute value of the axial momentum before 45% axial chord in CT_50 was reduced by 50%, whereas the maximum tangential momentum value of CT_50 was decreased by 70% relative to the solid Casing. CT_50 configuration was located across the shock wave; thus, it can fully utilize the pressure gradient to bleed and remove the blockage region, and the across flow is considerably depressed.

Casing Treatment is an efficient technique which is used to increase the compressor stall margin with a minor reduction in the efficiency. Various researches have indicated that the interaction between the blade passage and the groove is the main cause of the stall margin improvement. In this study a numerical study is conducted on a single circumferential Casing groove using NASA rotor 37. The performance of the two circumferential groove models is studied by discretizing RANS 3D equations using a finite volume technique. The inception of the stall is predicted according to the criteria of convergence. Two models of the circumferential groove have been suggested and numerically tested. A single passage simulation is selected for the two models. The performance of the smooth Casing and the two models are analyzed. Moreover, the stall margin, total pressure ratio and peak adiabatic efficiency of the normal Casing, and the two models are analyzed to determine the influence of the groove on the axial compressor performance and stability. Models 1 and 2 stall margins are enhanced by 6. 62% and 4. 45% respectively. The adiabatic efficiency of Models 1 and 2 is decreased by 0. 79% and 1. 08% respectively.

Unsteady numerical simulation of single passage was carried out on NASA Rotor 35 to study the influence of the radial inclined angle of self-circulation Casing Treatment (SCT) on the performance and stability of a transonic compressor at 100% design speed. The radial inclined angles were set to 0°(D0), °(D30) and 60°(D60), respectively. The calculated result indicates an increase in the stall margin improvement (SMI) and the design efficiency improvement (DEI) as the radial inclined angle increases gradually. The SMI of the SCT with a 60° radial inclined angle is 12. 5%, the biggest among the three SCTs, and the peak efficiency improvements (PEI) of the SCTs are almost the same. The radial inclined angle is provided with the effect of strengthening the self-circulation Casing Treatment effect, which further improves the stable working range of the compressor, and the efficiency loss is also lower than that of the 0° angle structure. The flow conditions inside the bleeding part can be improved by radially skewing the self-circulating structure toward the rotor rotating direction.

People with Parkinson's disease (PD) often have walking difficulty in the advanced stages of the disease and also suffer from balance problems. They perform their functional movements in a smaller range and at a slower rate, which will cause difficulty in performing daily activities. Patients with PD face many difficulties in outdoor activities, community participation, personal tasks, and fine motor skills (e. g. writing). They usually need the help of others. For two decades, a new Treatment called Lee Silverman Voice Treatment (LSVT) has been used by the speech therapists to treat speech and swallowing disorders in PD patients based on evidence and principles of neuroplasticity. The BIG protocol was added to this method in 2010 (LSVT-BIG). In this method, the whole body is involved and its main focus is on motor skills, which are guided by a physiotherapist and occupational therapist. The main goal of this new method is to improve patient’ s skilled movement in PD, as opposed to the old methods that introduce muscle stiffness as the main problem in these patients. In this method, patients will be required to perform a series of special exercises in sitting and standing positions in a larger range than usual with a specific schedule and in a one-month intensive period. Doing the BIG protocol correctly can make the range of motion softer and larger. The studies also show that the LSVT BIG method is very effective for improving patients' walking patterns and daily activities and significantly increases the quality of life in PD patients. Eventually, the PD patients will be able to perform their motor tasks automatically. Considering the useful results of this method and also the growing trend of its application around the world, it is necessary to enable therapists with this new method and provide more complete services for PD patients.

Centrifugal pumps often deviate from its design condi-tion during its operation and work at low mass flow conditions. Under such circumstances, unstable flow phenomena may be generated, affecting the efficient and stable operation of pumps. In this paper, a self-circulating Casing Treatment in U-tube shape is employed on a centrifugal pump to study its effects on the pump’s performance by computational and experi-mental studies. CFD results show that as the flow rate decreases, the back-flow in the inlet pipe of the studied pump without Casing Treatment increases in intensity and spreads over an growing distance, interfering with the main flow. CFD results also reveal that the Casing Treatment has a sucking function to the back-flow due to the blade loading of the pump, and when the inlet bleed of the U-tube is placed above (in front of) the leading edge of the blades, the sucking is the strongest, and the control of the back-flow and the improvement to the head coefficient under low mass flow conditions is the best, as the vortex blockage caused by the sucked back-flow in the U-tube is the smallest, when the bleed is under (after) the leading edge of the blades, the effect of the Casing Treatment is the second best, and when the bleed is across the leading edge of the blades, the blockage in the U-tube is most severe, and the sucking function is the weakest, so there is little improvement to the back-flow and head coefficient. Finally, the relia-bility of this study was demonstrated employing an open pump experimental system with the original pump and the same pump with the Casing Treatment whose bleed is located above the leading edge of the impeller.