The Experts below are selected from a list of 34440 Experts worldwide ranked by ideXlab platform
Keizo Watanabe - One of the best experts on this subject based on the ideXlab platform.
-
LIMITING MAXIMUM DRAG REDUCTION ASYMPTOTE FOR THE MOMENT COEFFICIENT OF AN ENCLOSED Rotating Disk WITH FINE SPIRAL GROOVES
MAKARA of Technology Series, 2010Co-Authors: Budiarso Budiarso, Keizo Watanabe, Satoshi OgataAbstract:In this study, the limiting maximum drag reduction asymptote for the moment coefficient of an enclosed Rotating Disk with fine spiral grooves in turbulent flow region were obtained analytically. Analysis which were based on an assumption for a simple parabolic velocity distribution of turbulent pipe flow to represent relative tangential velocity, was carried out using momentum integral equations of the boundary layer. For a certain K- parameter the moment coefficient results agree well with experimental results for maximum drag reduction in an enclosed Rotating Disk with fine spiral grooves and drag reduction ratio approximately was 15 %. Additionally, the experimental results for drag reduction on a Rotating Disk can be explained well with the analytical results.
-
Limiting maximum drag-reduction asymptote for the moment coefficient of a Rotating Disk in drag-reducing surfactant solution
Journal of Fluid Mechanics, 2002Co-Authors: Satoshi Ogata, Keizo WatanabeAbstract:In this study, the limiting maximum drag-reduction asymptote for the moment coefficient of a Rotating Disk in a surfactant solution was obtained analytically. The analysis, which was based on the logarithmic velocity profile of turbulent pipe flow in the surfactant solution, was carried out using momentum integral equations of the boundary layer, and the moment coefficient results agreed with experimental results for maximum drag reduction in surfactant solution. Additionally, flow visualization was performed using the tracer and the tuft techniques, which revealed that the direction of flow of surfactant solution on the Disk was turned towards the circumferential direction and the amplitude of the circular vortex on the Rotating Disk was reduced by addition of surfactant solution. The experimental results for flow angle on a Rotating Disk can be explained well with the analytical results.
Qixing Zhou - One of the best experts on this subject based on the ideXlab platform.
-
the combination of Rotating Disk photocatalytic reactor and tio2 nanotube arrays for environmental pollutants removal
Journal of Hazardous Materials, 2011Co-Authors: Aiyong Zhang, Minghua Zhou, Lu Han, Qixing ZhouAbstract:A combined photocatalytic system on one single TiO(2)-nanotube (TNT)/Ti photocatalyst, which was indeed the functional combination of photon-efficient thin-film and conventional bulk-phase photocatalysis processes, was effectively developed in Rotating Disk photocatalytic reactor for environmental purification applications. The TNT/Ti Rotating Disk, of uniform size and well-aligned, was successfully prepared by direct anodic oxidation on a dominantly large surface area of 38 cm(2), compared to the typical 1 cm(2) in available literature. To estimate the potentials of combined photocatalytic system for environmental applications, the degradation of rhodamine B was carried out under the optimized conditions, a substrate removal efficiency of nearly 90% and a mineralization efficiency of 56% were observed for initial 20 mg/L solution after 3 h treatment. Compared with the combined photocatalytic system on TiO(2) nanoparticle Disk, a significant improvement in substrate removal efficiency of about 25-40% was observed on TNT/Ti Disk. It was confirmed that the main degradation of rhodamine B occurred on the upper half of TNT/Ti Disk above the heavily colorized sample solution, which was attributed to the superior UV utilization efficiency and the resultant high interfacial photoactivity.
Jinping Jia - One of the best experts on this subject based on the ideXlab platform.
-
degrading organic pollutants and generating electricity in a dual chamber Rotating Disk photocatalytic fuel cell rpfc with a tio2 nanotube array anode
Research on Chemical Intermediates, 2015Co-Authors: Chen Yang, Yalin Wang, Ye Yao, Ruqiong Cao, Jinping JiaAbstract:This work reports a dual-chamber photocatalytic reactor with a TiO2 nanotube array (TNA) Rotating-Disk electrode to treat organic pollutants. The TNA was prepared using electrochemical anodization on the surface of a Ti Rotating-Disk electrode in ethylene glycol solution containing 0.3 wt% NH4F and 2 wt% H2O. The TNA Rotating-Disk electrode was employed as a photoanode. This reactor actually functioned as a fuel cell because it was able to generate and output electricity through degradation, or “burning,” of organic pollutants. Compared with conventional photocatalytic reactors, the proposed dual-chamber reactor with the TNA anode features improved light utilization efficiency and better hole–electron separation and mass transfer. Another important new characteristic of this reactor is that organic pollutants were degraded not only by photocatalytic degradation but also by additional oxidation provided by electrochemically generated H2O2 and ·OH in the system, resulting in superior overall performance. This is the first Rotating-Disk photocatalytic fuel cell realizing degradation of organic pollutants through multiple oxidation pathways with simultaneous generation of usable electricity.
-
novel wedge structured Rotating Disk photocatalytic reactor for post treatment of actual textile wastewater
Chemical Engineering Journal, 2015Co-Authors: Hongbo Zhang, Diwen Ying, Yalin Wang, Tiantian Tang, Tonghua Sun, Jinping JiaAbstract:Abstract A wedge structured Rotating Disk photocatalytic (PC) reactor was used for post-treatment of actual textile wastewater collected after activated sludge treatment. Compared with a conventional planar Disk, the wedge structured Disk had larger surface area and exhibited better light utilization efficiency. Treatment conditions such as pH and Rotating speed were optimized. The COD content in effluent was reduced from 380 mgO 2 L −1 to 109 and 56 mgO 2 L −1 respectively after 3 h and 5 h treatment at pH 6.0 and Rotating speed of 20 rpm. The effect of anions (NO 3 − , SO 4 2− and Cl − ) in actual textile wastewater on treatment was investigated. Benefit from high light utilization efficiency, the wedge Rotating Disk reactor could compensate COD removal inhibition caused by anions. A 1.5 V voltage was also applied to perform photoelectrocatalysis process to further improve the performance, and no additional electrolyte was needed. COD in effluent was reduced to as low as 75 mgO 2 L −1 after 3 h treatment. In addition, this reactor was used to treat other water samples including the actual textile wastewaters collected before activated sludge treatment (initial COD of 880 mgO 2 L −1 ) and after activated carbon adsorption post-treatment (initial COD of 108 mgO 2 L −1 ). Experimental results suggested that wedge structured Rotating Disk photocatalysis process was stable, efficient and worth further scale-up investigation.
-
photocatalytic degradation and electricity generation in a Rotating Disk photoelectrochemical cell over hierarchical structured biobr film
Applied Catalysis B-environmental, 2015Co-Authors: Hongbo Zhang, Yanping Tang, Diwen Ying, Yalin Wang, Jinping JiaAbstract:Abstract A double hierarchical structured BiOBr film was prepared on Ti substrate through hydrolysis of Bi2O3 film in the presence of Br− and H+. The prepared BiOBr film exhibited much better photocatalytic (PC) activity on Rhodamine B (RhB) degradation than Bi2O3 film in a Rotating Disk PC reactor. The double hierarchical structure could not only enhance the surface area, but also exhibited strong RhB adsorption capacity and high light utilization efficiency due to multiple reflections of incident light. Due to similar hierarchical structure, BiOCl film was also used to compare the PC activity of BiOBr film. Because the band gap energy of BiOBr (2.5 eV) was narrower than that of BiOCl (3.2 eV), weaker PC activity was obtained for BiOBr film under UV light. However, besides RhB photosensitization degradation, BiOBr could also be excited by part of visible light to generate •OH, resulting in a better RhB removal under visible light. A Pt cathode was further connected to BiOBr/Ti photoanode to establish a Rotating Disk BiOBr/Ti–Pt photoelectrochemical cell to generate electricity with the degradation of pollutants simultaneously. 0.77 and 0.74 V open-circuit voltage, 0.019 and 0.010 mA cm−2 short-circuit current density were obtained under UV and visible light irradiation, respectively, with 50 mL 5 mg L−1 RhB as “fuel”. The PC activity was also improved due to the efficient separation of electrons and holes. The total current generated was stable but gradually decreased with treatment time due to the consumption of “fuel”.
-
cu tio2 ti dual Rotating Disk photocatalytic pc reactor dual electrode degradation facilitated by spontaneous electron transfer
Environmental Science & Technology, 2009Co-Authors: Jinping Jia, Dengjie Zhong, Yali WangAbstract:A Cu-TiO2/Ti dual Rotating Disk photocatalytic (PC) reactor has been developed based on our single Rotating Disk photoelectrocatalytic (PEC) reactor (Y. Xu, et. al, Environ. Sci. Technol. 2008, 42, 2612−2617), and successfully applied to the treatment of laboratory and industrial dye wastewater. Round TiO2/Ti and Cu Disks of the same size are connected by a Cu wire and fixed parallel on an axis continually Rotating at 90 rpm. High treatment efficiency is obtained due to direct photooxidation on the TiO2/Ti photoanode as well as additional degradation on the Cu cathode, which is speculated via indirect hydrogen peroxide (H2O2) oxidation and direct electro-reduction of dye on cathode. The mechanism of the Cu-TiO2/Ti dual Rotating Disk PC reactor was investigated. In a 20 mg L−1 Rhodamine B (RB) solution, approximately 100 mV of potential and 10 μA of current were measured between the Cu and TiO2/Ti electrode during PC treatment. Such phenomenon was explained by spontaneous electron transfer based on the sam...
-
tio2 ti Rotating Disk photoelectrocatalytic pec reactor a combination of highly effective thin film pec and conventional pec processes on a single electrode
Environmental Science & Technology, 2008Co-Authors: Xinde Cao, Dengjie Zhong, Jinping JiaAbstract:A TiO2/Ti Rotating Disk photoelectrocatalytic (PEC) reactor has been developed and successfully applied to degrade Rhodamine B (RB) and other dyes in textile effluents. The innovative concept behind the reactor design is to simultaneously perform two processes on one electrode. These two processes are (1) highly effective thin-film PEC, in which the upper half of the round Disk photoanode was coated with a thin layer of wastewater and exposed to UV radiation in air; and (2) the conventional PEC, in which the other half of the Disk was immersed in bulk wastewater and irradiated by the same light source. The average aqueous film thickness was about 75 microm. The Disk electrode was kept Rotating at 90 rpm to continuously refresh the thin aqueous film for the upper side of the electrode and to promote the mass transfer of the target pollutants and the degradation products on the lower part of the Disk. Using 20-150 mg L(-1) RB solutions as a model system, thin-film PEC removed total color and total organic carbon (TOC) by 27-84% and 7-48%, respectively, within 1 h, much higher than 3-55% and 0-30% removal by conventional PEC under the same treatment conditions. Results also suggest that the thin-film process was especially superior for treating high concentration solutions. Application of the Rotating Disk PEC reactor in industrial textile effluents showed a satisfactory result. The recycle experiments demonstrated excellent stability and reliability of the Rotating Disk PEC electrode. This study proposed a new concept for designing a PEC reactor applicable to industrial wastewater treatment.
Satoshi Ogata - One of the best experts on this subject based on the ideXlab platform.
-
LIMITING MAXIMUM DRAG REDUCTION ASYMPTOTE FOR THE MOMENT COEFFICIENT OF AN ENCLOSED Rotating Disk WITH FINE SPIRAL GROOVES
MAKARA of Technology Series, 2010Co-Authors: Budiarso Budiarso, Keizo Watanabe, Satoshi OgataAbstract:In this study, the limiting maximum drag reduction asymptote for the moment coefficient of an enclosed Rotating Disk with fine spiral grooves in turbulent flow region were obtained analytically. Analysis which were based on an assumption for a simple parabolic velocity distribution of turbulent pipe flow to represent relative tangential velocity, was carried out using momentum integral equations of the boundary layer. For a certain K- parameter the moment coefficient results agree well with experimental results for maximum drag reduction in an enclosed Rotating Disk with fine spiral grooves and drag reduction ratio approximately was 15 %. Additionally, the experimental results for drag reduction on a Rotating Disk can be explained well with the analytical results.
-
Limiting maximum drag-reduction asymptote for the moment coefficient of a Rotating Disk in drag-reducing surfactant solution
Journal of Fluid Mechanics, 2002Co-Authors: Satoshi Ogata, Keizo WatanabeAbstract:In this study, the limiting maximum drag-reduction asymptote for the moment coefficient of a Rotating Disk in a surfactant solution was obtained analytically. The analysis, which was based on the logarithmic velocity profile of turbulent pipe flow in the surfactant solution, was carried out using momentum integral equations of the boundary layer, and the moment coefficient results agreed with experimental results for maximum drag reduction in surfactant solution. Additionally, flow visualization was performed using the tracer and the tuft techniques, which revealed that the direction of flow of surfactant solution on the Disk was turned towards the circumferential direction and the amplitude of the circular vortex on the Rotating Disk was reduced by addition of surfactant solution. The experimental results for flow angle on a Rotating Disk can be explained well with the analytical results.
Boumediene Chentouf - One of the best experts on this subject based on the ideXlab platform.
-
stabilization of memory type for a Rotating Disk beam system
Applied Mathematics and Computation, 2015Co-Authors: Boumediene ChentoufAbstract:In this article, a Rotating Disk-beam system is considered. Specifically, the system consists of a flexible beam and a rigid Disk which rotates with a time-varying angular velocity. The beam, free at one end and clamped at the other one to the center of the Disk, is supposed to rotate with the Disk in another plane perpendicular to that of the Disk. To stabilize the system, we propose a feedback law which consists of a control torque applied on the Disk, while either a boundary or distributed internal control with memory is exerted on the beam. Then, it is shown, in both cases, that the closed-loop system is stabilized under suitable conditions on the angular velocity and the memory terms.
-
stabilization of the Rotating Disk beam system with a delay term in boundary feedback
Nonlinear Dynamics, 2014Co-Authors: Boumediene ChentoufAbstract:In this article, the stabilization problem of a Rotating Disk-beam system is addressed. It is assumed that the flexible beam is free at one end, whereas the other end is attached to the center of the Rotating Disk whose angular velocity is time-varying. The proposed feedback law consists of a torque control which acts on the Disk, whereas a delayed boundary force control is exerted at the free end of the beam. Thereafter, it is proved that the presence of such controls in the system guarantees the exponential stability of the system under a realistic smallness condition on the angular velocity of the Disk as well as the feedback gain in the delay term. This result is illustrated by numerical examples.
