Hiroyuki Haniu

The formation mechanism and shedding frequency of vortices from a sphere in uniform shear flow

Experiments to investigate the formation mechanism and frequency of vortex shedding from a sphere in uniform shear flow were conducted in a water channel using flow visualization and velocity measurement. The Reynolds number, defined in terms of the sphere diameter and approach velocity at its centre, ranged from 200 to 3000. The shear parameter K, defined as the transverse velocity gradient of the shear flow non-dimensionalized by the above two parameters, was varied from 0 to 0.25. The critical Reynolds number beyond which vortex shedding from the sphere occurred was found to be lower than that for uniform flow and decreased approximately linearly with increasing shear parameter. Also, the Strouhal number of the hairpin-shaped vortex loops became larger than that for uniform flow and increased as the shear parameter increased.The formation mechanism and the structure of vortex shedding were examined on the basis of series of photographs and subsequent image processing using computer graphics. The range of Reynolds number in the present investigation, extending up to 3000, could be classified into three regions on the basis of this study, and it was observed that the wake configuration did not differ substantially from that for uniform flow. Also, unlike the detachment point of vortex loops in uniform flow, which was irregularly located along the circumference of the sphere, the detachment point in shear flow was always on the high-velocity side.

Properties of sugarcane waste-derived bio-oils obtained by fixed-bed fire-tube heating pyrolysis.

Agricultural waste in the form of sugarcane bagasse was pyrolyzed in a fixed-bed fire-tube heating reactor under different pyrolysis conditions to determine the role of final temperature, sweeping gas flow rate and feed size on the product yields. Final temperature range studied was between 375 and 575 degrees C and the highest liquid product yield was obtained at 475 degrees C. Liquid products obtained under the most suitable conditions were characterized by physical properties, elemental analysis, GCV, FT-IR, (1)H NMR analysis and distillation. The empirical formula of the bio-oil with heating value of 23.5MJ/kg was established as CH(1.68)O(0.557)N(0.012). Comparison with other approaches showed that the liquid product yield by this simpler reactor system was higher with better physico-chemical properties as fuel. These findings show that fixed-bed fire-tube heating pyrolysis is a good option for production of bio-oils from biomass solid wastes.

Pyrolysis decomposition of tamarind seed for alternative fuel.

The conversion of tamarind seed into bio-oil by pyrolysis has been taken into consideration in the present work. The major components of the system were fixed bed fire-tube heating reactor, liquid condenser and collector. The crushed tamarind seed in particle form was pyrolyzed in an electrically heated fixed bed reactor. The products were liquid, char and gasses. The parameters varied were reactor temperature, running time, gas flow rate and feed particle size. The maximum liquid yield was 45 wt% at 400°C for a feed size of 3200 μm diameter at a gas flow rate of 6l/min with a running time of 30 min. The obtained pyrolysis liquid at these optimum process conditions were analyzed for physical and chemical properties to be used as an alternative fuel. The results show the potential of tamarind seed as an important source of alternative fuel and chemicals as well.

Feasibility study for thermal treatment of solid tire wastes in Bangladesh by using pyrolysis technology.

In this study on the basis of lab data and available resources in Bangladesh, feasibility study has been carried out for pyrolysis process converting solid tire wastes into pyrolysis oils, solid char and gases. The process considered for detailed analysis was fixed-bed fire-tube heating pyrolysis reactor system. The comparative techno-economic assessment was carried out in US

Pyrolysis kinetics behavior of solid tire wastes available in Bangladesh.

for three different sizes plants: medium commercial scale (144 tons/day), small commercial scale (36 tons/day), pilot scale (3.6 tons/day). The assessment showed that medium commercial scale plant was economically feasible, with the lowest unit production cost than small commercial and pilot scale plants for the production of crude pyrolysis oil that could be used as boiler fuel oil and for the production of upgraded liquid-products.

Arch-type vortex formed behind a normal plate placed in a laminar boundary layer.

Pyrolysis kinetics of available bicycle/rickshaw, motorcycle and truck tire wastes in Bangladesh have been investigated thermogravimetrically in a nitrogen atmosphere at heating rates of 10 and 60 degrees C/min over a temperature range of 30-800 degrees C. The three tire wastes exhibited similar behaviors in that, when heating rate was increased, the initial reaction temperature decreased but the reaction range and reaction rate increased. The percentage of total weight loss was higher for truck tire waste and lower for bicycle/rickshaw tire waste. The pyrolysis of truck tire waste was found to be easier than that of bicycle/rickshaw and motorcycle tire wastes while it was comparatively more difficult for motorcycle tire waste. The overall rate equation for the three tire wastes has been modeled satisfactorily by one simplified equation from which the kinetic parameters of unreacted materials based on the Arrhenius form can be determined. The predicted rate equation compares fairly well with the measured TG and DTG data. DTA curves for all of the samples show that the degradation reactions are three main exotherms and one endotherm.

Technology development for bio-crude oil from pyrolysis of renewable biomass resource

Characteristics of arch-type vortex formed behind a plate of aspect ratio h/w = 0.8 (h: hight, w: width) which is placed vertically in a laminar boundary layer had been investigated. Flow visualization and analysis on velocity signals yielded following some new under standings. (i) The variation of Strouhal number St (=fcw/U0) with Reynolds number Re (=wU0/v) can be classified into three regions. (ii) Arch-type vortex formed behind a plate shows inconsistency in its periodicity and strength, and have no regular mode vortex shedding like two-dimensional circular cylinders. (iii) Different tendency of Strouhal number distribution for Reynolds number is due to the different time rate of intermittent vortex shedding. (iv) Arch-type vortex formed behind a plate starts to dissipate in the very vicinity of the downstream of the plate before convected to far downstream.

Fluctuating Lift Acting on a Square Prism with Attacking Angle Commencing Its Motion in Still Water : Suppression of Nonrepeatability in Fluctuating Lift Produced by Vortex Formation(Fluids Engineering)

The objective of this study is to provide an innovation in pyrolysis technology to the recovery of liquid hydrocarbons from biomass solid wastes. A fixed-bed fire-tube heating pyrolysis reactor system has been designed and fabricated considering all of the process parameters and present engineers challenge. The available agricultural waste-jute stick in Bangladesh has been pyrolyzed in the internally heated fire-tube heating reactor system under N2 atmosphere. The effects of operating temperature on the yields of product liquids were investigated. Characterization of the whole pyrolysis liquids obtained at optimum operating conditions has been carried out including physical properties, elemental analyses and GCV. The results show that fixed-bed fire-tube heating pyrolysis is a good option to obtain bio-oils from biomass solid wastes.

Vortical Structures in a Two-Dimensional Jet Under Flapping Motion Generated by a Wake of a Cylinder Installed in a Nozzle Contraction (2nd Report, Flow Visualization and Image Correlatioin Analysis)

静水 中で移動 を開始する迎え角のある正方形角柱 に作用する変動揚力* (渦形成に基づいて生じる変動揚力の非再現性の抑制) 羽二 生 博 之*1, 呉 平*2 宮 越 勝 美*1, 鈴 木 聡 一郎*1 Fluctuating Lift Acting on a Square Prism with Attacking Angle Commencing Its Motion in Still Water (Suppression of Nonrepeatability in Fluctuating Lift Produced by Vortex Formation) Hiroyuki HANIU*3, Ping WU, Katsumi MIYAKOSHI and Soichiro SUZUKI *3 Department of Mechanical Engineering, Kitami Institute of Technology, 165 Koen-cho, Kitami-shi, Hokkaido, 090-8507 Japan

Development of Analyzing Technique for Ice Movements in Okhotsuk Sea Using Satellites' Millimeter Radar Images

When a plane jet exhibits flapping motion, two distinctive peaks, f1 and f2, appear in the spectrum of fluctuating velocity. The mean frequency is half of the frequency, fv, of vortices shedding from a two-dimensional body that is installed in a jet nozzle contraction. Jet mixing has been enhanced by the flapping motion with a low frequency, f3=f1-f2, which is considered to be caused by an inharmonic excitation. Vortical structures in the flapping jet are investigated by using flow visualization, image correlation and laser Doppler velocimetry. Vortices are seen to roll up asymmetrically at the jet nozzle exit, at a double frequency of that of the vortex shedding from the cylinder. Two types of vortices are formed by coalescence between these vortices and the vortices shedding from the cylinder. The periodicities of these two types of vortices are found to be equal. It is noted that vortices with f1 or f2 do not exist in the flow. The f1 and f2 are caused by the modulation of amplitude of the coalesced vortical structures with half of the flapping frequency, f3.