共查询到18条相似文献，搜索用时 328 毫秒
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高密度盐水排放是海水淡化领域一个复杂和常见的物理现象。为研究波浪作用下盐水射流的水动力特性,建立了规则波作用下垂直圆管负浮力射流三维水动力数学模型。利用试验数据对数值计算结果进行验证,两者吻合较好。基于数值计算结果,分析规则波作用下垂直圆管负浮力射流流体扩散特征,研究规则波对负浮力射流三维时均速度以及瞬时浓度的影响。结果发现:入射波波高和周期对射流中轴上量纲一平均垂向速度的衰减指数影响不大,而对衰减系数影响较大;随着波高或波周期的增加,射流特征速度半宽增加,射流中轴上量纲一平均垂向速度的衰减系数减小,有助于射流流体在环境水体中的扩散。另外,建立了考虑浮力效应的波-射流动量比影响的射流中轴上量纲一平均速度衰减系数、平均特征半宽公式,可以为相关实际工程提供一定的参考。 相似文献
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对流动控制方程即连续方程、动量方程和能量方程进行坐标转化,将带有自由表面和不平坦底面的不规则物理区域转变为规则的矩形计算区域.应用大涡模拟Smagorinsky模型对控制方程进行模化,根据破裂算子法将动量方程和能量方程分解成对流、扩散和传播三步进行顺序求解.利用该模型对静止和规则波环境下二维窄缝热浮力射流进行数值模拟,比较了两种环境下速度场、温度场、轴线速度衰减规律、垂向流速的自相似分布等特性,分析了浮力的作用以及射流速度、窄缝宽度等因素对射流掺混过程中温度场分布的影响.数值模拟结果得到已有理论及试验成果的验证. 相似文献
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海啸波作用下泥沙运动——Ⅰ.岸滩剖面变化分析 总被引：1，自引：0，他引：1
在波浪水槽实验的基础上,对海啸波作用下的岸滩剖面演变规律开展研究。实验采用1/10~1/20的组合坡度,考虑3种不同的水深,选取N波作为入射波,同时采用规则波和非规则波进行对比研究。实验对波高、波浪的上爬、回落和水跃过程、每个波作用后的地形进行了测量和记录。研究结果表明,水动力特性的不同造成了N波与规则波和不规则波作用下不同的岸滩剖面演变特点。N波作用下发生了明显的岸滩冲刷和淤积,水流回落时滩肩发生冲刷,高速薄层回流和出渗水流作用是滩肩冲刷的主要原因,离岸区水跃发生水流挟沙力降低,泥沙淤积呈沙坝剖面。 相似文献
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开发建立了近岸波生流运动三维数值计算模式。模式中,引入了三维时均剩余动量、破波表面水滚、波浪水平与垂向紊动作为主要驱动力,同时考虑了波流共同作用的底部剪切力。推导了可综合反映底坡、能量传递率和密度影响的水滚能量传输方程;将Larson-Kraus的二维波浪水平紊动系数表达式拓展至三维。采用大量实测数据和文献资料测试验证了所建模式,表明所建模式可有效模拟波浪增减水、底部离岸流、沿岸流、裂流、堤后环流等不同维度的波生流现象。此外,研究也表明破波水滚效应可解释波生流峰值向岸推移的物理现象,从而在模拟中不能忽略;破波带内沿岸流速垂向较为均匀的现象与波浪附加垂向紊动有关。 相似文献
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通过在波浪水槽中进行一系列物理模型试验研究规则波作用下刚性挺水植物波生流特性,测试了2种水深和不同入射波况条件下的波生时均流速并对比了挺水植物有茎与无茎时波生流的情况,基于假设检验分别对挺水植物的拖曳力长度尺度、植物特征参数建立模型。研究结果表明:在茎密度为60株/m2时,波生流仍以根部作用为主要因素,对沉水植物公式进行拓展,据此提出挺水植物时均流速最大值预测公式;茎部对时均流速均方根具有衰减作用,且茎部在根部及根部上方区域产生的相对衰减强度,与厄塞尔数呈抛物线函数关系;在簇状根系分布下,茎部对垂向流速结构起稳定作用,尤其是在时均流速最大值所对应的量纲一垂直位置。 相似文献
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波浪增水抬升了岸礁礁坪的平均水位,对岸礁后方陆域安全有重要影响。通过水槽试验,研究了不规则波况下岸礁礁坪的增水。试验组次为3种礁坪水深、4种有效波高和4种谱峰周期的组合。试验结果表明:①岸礁地形上的波浪要素需至少统计200个波才能达到稳定;②不规则波列在岸礁上破碎过程比规则波列复杂,同一波列中波高较大的波以卷破形式在礁前斜坡上破碎,波高较小的波以崩破形式在礁坪上破碎或者不破碎;③礁坪上最大增水值随入射波周期的增大而增大、随礁坪水深的增大而减小,并与入射波波高呈正比。结合试验数据,发现基于规则波试验得出的Gourlay礁坪增水公式,在使用有效波高和谱峰周期作为代表波要素时,公式能良好地预测不规则波在岸礁礁坪上的最大增水值。 相似文献
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岩石孔隙流体对纵横波速度影响的实验研究及意义 总被引：16，自引：0，他引：16
我们用ＭＴＳ的超声波测试系统研究了地表岩样饱和水及孔隙压力对纵横波速度的影响。在实验研究中,分别在常温常压条件下测量了干燥岩石和完全饱水岩石的纵横波速度,并在模拟地层条件下,测量了岩石纵横波速度随孔隙压力的变化。实验结果显示：（１）岩石完全饱和水后,与干燥时相比,纵波速度将明显增加,最大可增加３０％,且岩石在干燥时的纵波速度越低速度增大的比例越大,但纵波速度增大的比例与孔隙度无明显关系。饱水前后横波速度几乎保持不变。（２）在模拟地层的温压条件下,当孔隙压力由低到高,纵横波速度均将线性减小,且横波速度比纵波速度下降的比例更大。据此,得到了识别地层异常高压和地层含气的地震速度标志。 相似文献
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速度分析是多波资料处理的核心问题之一,在高精度地震勘探的今天,建立在各向同性假设条件下的速度分析已经不能满足高精度勘探要求。这里以自然界广泛存在的具有垂直对称轴的横向各向同性（VTI）介质为基础,研究各向异性条件下P波和P～SV转换波旅行时公式,并进一步研究了P波和P～SV转换波速度分析的方法步骤,在此基础上用QT开发出一套各向异性介质多波速度分析的交互处理软件。用该方法及软件对理论资料和实际资料进行处理,取得了较好的处理效果,验证了该方法及软件的正确性。 相似文献
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AbstractCompaction driven fluid flow is inherently unstable such that an obstruction to upward fluid flow (i.e. a shock) may induce fluid-filled waves of porosity, propagated by dilational deformation due to an effective pressure gradient within the wave. Viscous porosity waves have attracted attention as a mechanism for melt transport, but are also a mechanism for both the transport and trapping of fluids released by diagenetic and metamorphic reactions. We introduce a mathematical formulation applicable to compaction driven flow for the entire range of rheological behaviors realized in the lithosphere. We then examine three first-order factors that influence the character of fluid flow: (1) thermally activated creep, (2) dependence of bulk viscosity on porosity, and (3) fluid flow in the limit of zero initial connected porosity. For normal geothermal gradients, thermally activated creep stabilizes horizontal waves, a geometry that was thought to be unstable on the basis of constant viscosity models. Implications of this stabilization are that: (1) the vertical length scale for compaction driven flow is generally constrained by the activation energy for viscous deformation rather than the viscous compaction length, and (2) lateral fluid flow in viscous regimes may occur on greater length scales than anticipated from earlier estimates of compaction length scales. In viscous rock, inverted geothermal gradients stabilize vertically elongated waves or vertical channels. Decreasing temperature toward the earth’s surface can induce an abrupt transition from viscous to elastic deformation-propagated fluid flow. Below the transition, fluid flow is accomplished by short wavelength, large amplitude waves; above the transition flow is by high velocity, low amplitude surges. The resulting transient flow patterns vary strongly in space and time. Solitary porosity waves may nucleate in viscous, viscoplastic, and viscoelastic rheologies. The amplitude of these waves is effectively unlimited for physically realistic models with dependence of bulk viscosity on porosity. In the limit of zero initial connected porosity, arguably the only model relevant for melt extraction, travelling waves are only possible in a viscoelastic matrix. Such waves are truly self-propagating in that the fluid and the wave phase velocities are identical; thus, if no chemical processes occur during propagation, the waves have the capacity to transmit geochemical signatures indefinitely. In addition to solitary waves, we find that periodic solutions to the compaction equations are common though previously unrecognized. The transition between the solutions depends on the pore volume carried by the wave and the Darcyian velocity of the background fluid flux. Periodic solutions are possible for all velocities, whereas solitary solutions require large volumes and low velocities. © Elsevier, Paris 相似文献
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为研究风浪作用下水生植物对水流结构的影响,选取太湖中两种典型沉水植物(苦草与马来眼子菜)为研究对象,分别对苦草植物斑块与马来眼子菜植物斑块内外水体的瞬时流速进行野外现场测量,利用瞬时流速的能量谱分布将波浪流速与紊动流速分离,分别分析水生植物对时均流速、波浪流速以及紊动能的影响。风浪影响下,水体中存在流向与测量时近水面处盛行风向一致的水流;波浪流速以垂向流速为主,且波浪流速自水面向床底逐渐减小;紊动能在水面处达到最大值,并向床底方向逐渐减小。与无植被条件相比,苦草与马来眼子菜的存在减小了时均流速、波浪流速以及紊动能。两种植物形态上的差异,导致其对水流结构的影响不同:苦草叶片阻流面积在冠层中部达到最大,使得时均流速与波浪流速在苦草中部位置的减小程度最大;马来眼子菜叶片主要集中于冠层顶部(水面附近),其对时均流速以及波浪流速的减小作用在水面处达到最大。 相似文献
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采用粒子图像测速和平面激光诱导荧光技术对波浪环境中倾斜射流的运动和稀释特性进行了实验研究,对比分析了排放角度对射流瞬时运动形态、时均速度场和时均浓度场的影响。实验结果表明排放角度的变化对波浪环境中射流的运动形态、速度分布和混合范围等均有显著影响。当射流顺波浪方向运动时,射流主体段速度剖面呈双峰分布,达到初始浓度20%、30%、40%和50%的混合范围随排放角度增加而先增大后减小;当射流逆波浪方向运动时,射流速度剖面双峰分布不明显,相应的混合范围随排放角度增加而减小。在波浪牵引和射流卷吸的共同作用下,逆向射流的稀释效果总体上优于与垂线方向相同夹角的顺向射流。 相似文献
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为研究风浪作用下水生植物对水流结构的影响，选取太湖中两种典型沉水植物（苦草与马来眼子菜）为研究对象，分别对苦草植物斑块与马来眼子菜植物斑块内外水体的瞬时流速进行野外现场测量，利用瞬时流速的能量谱分布将波浪流速与紊动流速分离，分别分析水生植物对时均流速、波浪流速以及紊动能的影响。风浪影响下，水体中存在流向与测量时近水面处盛行风向一致的水流；波浪流速以垂向流速为主，且波浪流速自水面向床底逐渐减小；紊动能在水面处达到最大值，并向床底方向逐渐减小。与无植被条件相比，苦草与马来眼子菜的存在减小了时均流速、波浪流速以及紊动能。两种植物形态上的差异，导致其对水流结构的影响不同：苦草叶片阻流面积在冠层中部达到最大，使得时均流速与波浪流速在苦草中部位置的减小程度最大；马来眼子菜叶片主要集中于冠层顶部（水面附近），其对时均流速以及波浪流速的减小作用在水面处达到最大。 相似文献
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S. M. Bawiskar M. D. Chipade D. K. Paul S. S. Singh 《Journal of Earth System Science》1995,104(4):613-634
Kinetic energy exchange equations (Saltzman 1957) in wave number domain are partitioned into standing, transient and standing-transient
components following Murakami (1978, 1981). These components are computed for the 1991 summer monsoon using dailyu andv grid point data at 2.5° latitude-longitude interval between the equator and 40°N at 200 hPa and 850 hPa levels for the period
June through August. The data are obtained from NCMRWF, New Delhi.
The study shows that at 200 hPa wave number 1 over Region 3 (30°N to 40°N), wave number 2 over Region 2 (15°N to 30°N) and
wave number 3 over Region 1 (equator to 15°N) dominate the spectrum of transport of momentum and wave to zonal mean flow interaction.
Wave number 1 over Region 1 and Region 3 and wave number 2 over Region 2 are the major sources of kinetic energy to other
waves via wave-to-wave interaction. At 850 hPa wave number 1 over Region 3 has maximum contribution in the spectrum of transport
of momentum and kinetic energy and more than 90% of its contribution is from the standing component. This indicates that standing
wave number 1 over Region 3 plays a very important role in the dynamics of monsoon circulation of the lower troposphere.
The study further shows that although the circulation patterns at 200 hPa and 850 hPa levels are opposite in character, a
number of energy processes exhibit a similar character at these levels. For example, (i) transport of momentum by most of
the waves is northward, (ii) small scale eddies intensify northward, (iii) eddies are sources of kinetic energy to zonal mean
flow over Region 1 and (iv) standing eddies are sources of kinetic energy to transient eddies. Besides the above similarities
some contrasting energy processes are also observed. Over Region 2 and Region 3 standing and transient eddies are sources
of kinetic energy to zonal mean flow at 200 hPa, while at 850 hPa the direction of exchange of kinetic energy is opposite
i.e. zonal mean flow is a source of kinetic energy to standing as well as transient eddies. L(n) interaction indicates that at 200 hPa waves over R2 maintain waves over R1, while at 850 hPa waves over R1 maintain waves
over R2.
It has been found that the north-south gradient of zonal mean of zonal wind is the deciding factor of wave to zonal mean flow
interaction. 相似文献
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Radial anisotropy in the crust and upper mantle beneath the Qinghai-Tibet Plateau and surrounding regions 总被引：7，自引：0，他引：7
Relative SV and SH wave speeds are generally attributed to radial seismic anisotropy which can be used as the indicator of crust/mantle deformation styles. Surface wave data were initially collected from events of magnitude Ms 5.0 and shallow or moderate focal depth occurring between 1980 and 2002: 713 of them generated Rayleigh waves and 660 Love waves, which were recorded by 13 broadband digital stations in Eurasia and India. Up to 1525 source-station Rayleigh waveforms and 1464 Love wave trains were earlier analysed by multiple filtering to obtain Love- and Rayleigh wave group velocity curves in the broad period range 10–105 s. We have performed tomographic inversion to obtain period-dependent group velocity and further shear wave velocity at 2° × 2°-sized grid-cells of a mesh covering the model region, after averaging azimuthal effects. Horizontally and vertically varying shear-wave velocities are observed, but the models of isotropic seismic velocity in the crust and upper mantle cannot fit simultaneously the inverted group-velocity dispersion curves due to the discrepancy in the transmission velocities of Love and Rayleigh waves, whose likely origin is the existence of radial anisotropy in the continental crust and topmost mantle. The strength of radial anisotropy computed from the Love–Rayleigh discrepancy and its spatial extent beneath the Qinghai-Tibet Plateau are shown as maps of percentage anisotropy at various depths down to 170 km and cross-sections along five profiles of reference. Areas in which radial anisotropy is in excess of 6% are found in the crust and upper mantle underlying most of the plateau, and even up to 10% in some places. The strength and spatial configuration of radial anisotropy seem to indicate the existence of a regime of horizontal compressive forces in the frame of the convergent Himalayan–Tibetan orogen, the laterally variation of the lithospheric rheology and the differential movement as regards the compressive driving forces. 相似文献
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为探明滚波的演变过程及产生机理,采用定床阻力试验和超声波测量技术,研究了5种糙度、5种能坡、8种单宽流量下滚波水力参数的变化规律。结果表明:在固定断面,波速随单宽流量增加呈幂函数关系增大,相对波速反之,波高与相对波高先增大后减小;随糙度增加,波速减小,相对波速增大,波高及相对波高均减小;能坡对滚波的影响也与糙度有关,小糙度下,波速随能坡增加呈幂函数关系增大,相对波速反之,波高先增大后减小,相对波高持续增大;而大糙度下,随能坡增加,相对波速增加,波高整体不变,相对波高增加趋势变缓甚至有所减小。分析可知,相对波速、相对波高考虑了平均水力参数的变化,可以更好地反映各因素对滚波演变过程的影响。 相似文献