H-ADCP流速比测分析中误差校正的方法探讨

针对H-ADCP系统流速比测分析中方案合格率偏低的情况,以实测平均流速为水体传播速度对实测流量进行相关插补,校正H-ADCP设备安装断面与比测断面不重合导致的实测平均流速与指标流速拟合误差。通过水文调查,参考多年实测流量,校正比测资料不充分造成的流量资料整编误差,这一方法在宜州刘三姐水文站可行。

基于沙里寨水文站水面流速系数分析研究

在实测河道流量时,往往因为洪水涨落急剧、洪峰历时短无法采用多点法施测流速;或在采用浮标法及缆道流速仪法施测流量时,多采用水面一点法施测流速,而在计算垂线平均流速时涉及水面流速系数的问题。通过对大洋河沙里寨水文站实测的垂线五点流速,建立水面与垂线平均流速相关关系,确定该站水面流速系数。

基于水位流量单值化处理的测验条件分析

本文分析了流域、环境等影响下的水位流量单值化处理过程,通过对各基本水文测站流量影响关键因素的探究,寻求水位流量单值化处理下测验的共同条件,形成特定关系、促进测验成果转化,为水文巡测提供技术支撑。

Experimental Study on the Flow Around Two Tandem Cylinders with Unequal Diameters

In this paper, flow around two circular cylinders in tandem arrangement with unequal diameters has been investigated using the particle image velocimetry technique(PIV) in a water channel. The upstream to downstream diameter ratio was kept constant at d/D = 2/3, the centre-to-centre distance was varied from 1.2D to 5D and the Reynolds number was varied from 1200 to 4800. The flow characteristics were analyzed through ensemble-averaged patterns of velocity, vorticity, normalized Reynolds stress contours and streamlines. Based on ensemble-averaged and instantaneous flow fields, different flow patterns, including single-wakeshedding at small spacing ratio, bi-stable flow behavior(alternating behavior of reattachment and vortex shedding) at intermediate spacing ratio and co-shedding pattern at large spacing ratio were observed. The effects of Reynolds number and the centre-to-centre spacing ratio on flow patterns and turbulent characteristics were also investigated. It was found that the diameter ratio appears to have a certain effect on the flow patterns at intermediate spacing ratios, where the reattachment of shear layer depends on the lateral width of the wake flow in the lee of the upstream cylinder. Extensive discussion on the distributions of Reynolds stress and turbulent kinetic energy was presented.

Experimental Study of Airflow-Mixture in HVAC Unit by Using PIV

In this paper, experimental results are reported about, especially, effect of turbulence in airflow-mixture in HVAC （heating, ventilating, air-conditioning） unit. A flow channel in this study has same characters as actual HVAC unit, such as bent rectangular duct, a heater unit and a flow control door. The experiment was carried out to obtain verification data for analysis by using PIV （particle image velocimetry） system. Moreover, temperature map in the channel was also obtained by using thermocouples. Reynolds number is set to 12800. As a result of this study, representative velocity distributions and Reynolds stress distributions were obtained. It was found that stress value is quite high （maximum 1.4） by preliminary turbulence and mixture in the duct. In addition, it was also found that temperature diffusion is promoted by mixing around door.

Experimental Investigation of Solar Chimney Power Plant

The paper investigated the performance of a solar chimney, by measuring the chimney air temperature and velocity. A short solar chimney prototype was designed and constructed at Botswana Technology Center. A wind turbine was installed to rotate a small DC generator. Temperatures and velocities were measured at different times of the day with thermocouples and hotwire anemometer, respectively. Irradiance was measured with pyranometer. A Delta-T data logger was used to store data at intervals of 30 s. Various graphs depicting the influence of irradiance on temperature, velocity and power have been plotted. Irradiance was found to affect the chimney temperature and subsequently affects chimney air velocity and power produced. Ambient air （wind） velocity was found to have influence on the performance of the solar chimney by increasing chimney air velocity.

Experimental investigation of the unsteady flow in a double-blade centrifugal pump impeller

Particle Image Velocimetry (PIV) technology was used to study the unsteady internal flow in a double-blade centrifugal pump (DBCP) impeller at the design flow rate.Relative velocity distributions and turbulence intensity distributions in the DBCP impeller at six phase conditions were obtained.And mean dimensionless relative velocity,turbulence intensity,mean absolute flow angle,mean relative flow angle,mean dynamic pressure and mean angular momentum distributions at the different radii of impeller were calculated.Results show that from impeller inlet to impeller outlet,turbulence intensities gradually decrease.With the increase of radius r,mean dimensionless relative velocity first decreases and then increases,while variation tendencies of mean absolute flow angle and mean dynamic pressure are the opposite.With the increase of radius r,turbulence intensity and mean relative flow angle first decrease,then increase,and then decrease,while mean angular momentum gradually increases.

Experimental Study on Measurement and Calculation of Heat Flux in Supersonic Combustor of Scramjet

An experimental measurement and calculation method which consist of thermal response model, convergence criteria and control algorithms, is proposed in this paper for the determination of heat flux in a scramjet combus- tot. Numerical simulations are done to evaluate the effectiveness of the proposed method, and experiments are made in the direct-connect hydrocarbon fueled scramjet combustor of Mach-6 flight for different equivalence ra- tios. The distribution of heat flux along the axial and circumferential directions can be obtained using the pro- posed method. The distribution of heat flux is uneven which is caused by the aerodynamic heating, combustion heat release and changes of section area, and the peak heat flux can be more than 2MW/m^2 during the experi- ments. Heat flux increases with the increase in equivalence ratio for the same Mach number. And axial distribu- tion of heat flux is uniform for different equivalence ratios. In addition, the combustion heat release area of the combustion chamber can therefore be concluded which is useful for guiding the structural design of the thermal protection system.

Corner Separations around a NACA65 Blade in a Decelerating Flow (Experimental Investigations by Five-Hole Probe and PIV)

In order to examine the fundamental characteristics of corner separation in a decelerating cascade flow,the experimental apparatus was made and separations around a NACA65 blade in a decelerating channel flow were examined.Two-dimensional calculations show that the NACA65 cascade flow that has 45 deg.of turning,1.24 of solidity and 17 deg.of stagger angle is equivalent to the channel flow that has 14 deg.of stagger angle in terms of pitchwise blade force.Experimental investigation by five-hole probe shows that the accumulations of low energy fluid can be seen around the corner part and the overturning flow due to the secondary flow exists.And,as the periodicity of the blade wake in a pitchwise direction is comparably good,the wake of this channel flow is similar to the wake of the cascade flow for two pitch portion.PIV measurement results shows that a vortex pattern can be seen in the momentary streamline on the suction surface of the blade and in the averaged streamline on the perpendicular to both the suction surface and the endwall.

Development of the detonation-driven expansion tube for orbital speed experiments

The hypersonic flow at orbital speeds is a fundamental issue for the ground tests of aerospace crafts.The detonation-driven high-enthalpy expansion tube(JF16 expansion tube)was developed to investigate re-entry physics.A forward detonation cavity(FDC)driver was applied in the JF16 expansion tube to create stable driving flows.The sound speed ratio of the detonated to test gas was examined to minimize the magnitude of test flow perturbations.The acceleration section length,incident shock decay and diaphragms thickness were investigated in detail to obtain optimal operation parameters.Flow visualization was also carried out with schlieren system to demonstrate the test flow stability and the effective test duration.Experimental data showed that the test flow with a velocity of 8.3 km/s and a total enthalpy up to 40 MJ/kg can be generated successfully and the test duration lasts for more than 50μs.