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201.
202.
Modelling the motion of an internal solitary wave over a bottom ridge in a stratified fluid 总被引:1,自引:0,他引:1
Yakun Guo Johan Kristian Sveen Peter A. Davies John Grue Ping Dong 《Environmental Fluid Mechanics》2005,4(4):415-441
A series of laboratory experiments has been carried out to investigate the passage of an internal solitary wave of depression over a bottom ridge, in a two-layer fluid system for which the upper and lower layer is linearly-stratified and homogeneous respectively. Density, velocity and vorticity fields induced by the wave propagation over the ridge have been measured simultaneously at three locations, namely upstream, downstream and over the ridge crest, for a wide range of model parameters. Results are presented to show that wave breaking may occur for a sufficiently large wave amplitude and a strong ridge blockage factor, with accompanying mixing and overturning. Density field data are presented (i) to illustrate the overturning and mixing processes that accompany the wave breaking and (ii) to quantify the degree of mixing in terms of the wave and ridge parameters. For weak encounters, good agreement is obtained between the laboratory experimental results (velocity and vorticity fields induced by the wave propagation) and the predictions of a recently-developed fully nonlinear theory. Discrepancies between theory and experiment are discussed for cases in which breaking and mixing occur. 相似文献
203.
刘国海 《石油化工环境保护》1997,(4):23-24
介绍了螺旋式管道静态混合器的结构和原理.在PTA污水处理装置上,采用三级静态混合器进行得水混合,代替了均质池加搅拌机的传统混合方法.收到了良好的效果.实现了投资省、耗能低、维修容易、混合效果好的目的.为污水处理领域进行污水混合提供了新的行之有效的方法. 相似文献
204.
陈行水库氨氮完全混合模型研究 总被引:1,自引:0,他引:1
建立了陈行水库氨氮完全混合模型,对氨氮浓度进行了模拟预测,并讨论了结论. 相似文献
205.
The stability, mixing and effect of downstream control on axisymmetric turbulent buoyant jets discharging vertically into
shallow stagnant water is studied using 3D Reynolds-averaged Navier–Stokes equations (RANS) combined with a buoyancy-extended
k –ε model. The steady axisymmetric turbulent flow, temperature (or tracer concentration) and turbulence fields are computed using
the finite volume method on a high resolution grid. The numerical predictions demonstrate two generic flow patterns for different
turbulent heated jet discharges and environmental parameters (i) a stable buoyant discharge with the mixed fluid leaving the
vertical jet region in a surface warm water layer; and (ii) an unstable buoyant discharge with flow recirculation and re-entrainment
of heated water. A stratified counterflow region always appears in the far-field for both stable and unstable buoyant discharges.
Provided that the domain radius L exceeds about 6H, the near field interaction and hence discharge stability is governed chiefly by the jet momentum length scale to depth ratio
lM/H, regardless of downstream control. The near field jet stability criterion is determined to be lM/H = 3.5. A radial internal hydraulic jump always exists beyond the surface impingement region, with a 3- to 6-fold increase
in dilution across the jump compared with vertical buoyant jet mixing. The predicted stability category, velocity and temperature/concentration
fields are well-supported by experiments of all previous investigators. 相似文献
206.
The air quality in urban areas is on the one hand determined by the intensity of emissions. On the other hand atmospheric dispersion and chemical transformation conditions as well as topographic location have great influence on the ambient air concentrations. Within, this study the correlation between pollutant concentrations and the dynamics of atmospheric barrier and mixing layers has been experimentally investigated by tethered balloon soundings.The most important barrier layer is the surface inversion. During clear sky it develops in the late afternoon and is dissolved by warm air from the heated ground in the morning. Emitted pollutants are kept beneath this inversion. But, at the same time, the component ozone is depleted below and stored above the layer within the so called `ozone reservoir layer'. During night elevated mountain sites are decoupled from the ground conditions and stay within this reservoir without a remarkable nocturnal decrease of ozone concentration. The regularly observed ground level ozone increase in the morning hours is firstly caused by down mixing from the reservoir. The conditions and dynamics are illustratively depicted by vertical profiles of the different components and diagrams of temperature and concentration isopleths over the height and the experiment time lasting over five days. 相似文献
207.
逆流湍动床生物膜反应器液相混合特性的研究 总被引:2,自引:1,他引:1
研究了实验室规模逆流湍动床的水力学特性。以亚硝酸钠作为示踪剂,采用刺激响应技术,通过测定停留时间分布(RTD),考察了反应器的内部流动状况。考察了不同固含率(0~0.3)、表观气速(1.1~8.8 mm/s)和表观液速(0.66~1.7 mm/s)对RTD的影响。研究表明,表观气速增大、固含率减小和适当提高表观液速都会使反应器返混增强,更接近CSTR。反应器死区百分率低,结构性能良好;死区百分率与表观气速和液速相关性不强,而与固含率负相关。逆流湍动床的RTD可用轴向扩散模型、等体积多釜串联模型和不同体积2釜串联模型来模拟,这些模型的特征参数Pe、N和α分别为1.25~1.79、1.46~1.67和0.74~0.90。 相似文献
208.
N. Ali E.U. KhanP. Akhter N.U. KhattakF. Khan M.A. Rana 《Journal of environmental radioactivity》2011,102(1):35-42
Concentration of radionuclides 210Pb and 7Be, having half lives of 22.3 years and 53.29 days, respectively, in the surface air samples of Islamabad (33.38° N, 73.10° E and Altitude ∼536 m asl.) are measured. The non-destructive technique of gamma-spectrometry, with a high purity germanium HPGe detector, was employed for the analysis of all samples. The annual average concentrations of 210Pb and 7Be in the surface air samples were determined as 0.284 ± 0.15 and 3.171 ± 1.14 mBq m−3, respectively. Our results have shown a seasonal variation of the concentration of 7Be in air samples with high values for the spring season. High concentrations for 210Pb are obtained when air masses originate from plain areas of Pothohar region, located in the South-West, West and North West of Islamabad. Our values of concentrations show a nice agreement with the relevant reported results. 相似文献
209.
污染土体的工程特性已成为环境岩土工程领域的研究热点之一,如何制备重塑污染土样是决定实验结果是否能够真实反映污染土体实际情况的关键。介绍了3种重塑污染土样的室内实验方法,包括人工拌和-击实法、击实-浸泡法和固结-渗透淋滤法,并以Cu Cl2溶液为污染溶质进行实验,分析比较3种制样方法的优缺点及适用范围。人工拌和-击实法制备污染土样的速度最快,适用范围最广;击实-浸泡法适用于模拟污染液浓度已知的情况;固结-渗透淋滤法制备的污染土样最均匀,土样结构差异性较小,适用于研究污染土体的渗透问题以及涉及不同围压作用的情况。 相似文献
210.
分别以活性炭和陶粒作为载体,在无回流条件下研究了不同上升流速时,反应器的离散数D/μL和串联数N的变化规律.试验结果表明,上升流速,固体混合特性以及载体性质均对反应器离散程度产生影响.只要反应器达到一定的膨胀率,反应器的流态就比较接近完全混合型.活性炭为载体时,上升流速为0.29cm/s,膨胀率为9.5%,串联数N为2.17.说明用完全混合型反应器模拟生物流化床反应器是可行的. 相似文献