Two-layer rotating hydraulics: Strangulation,remote and virtual controls   总被引：1，自引：0，他引：1  

Larry Pratt  Larry Armi 《Pure and Applied Geophysics》1990,133(4):587-617

The hydraulics of two-layer, rotating channel flow is examined in the limit where the channel width is large compared to the internal Rossby radius of deformation, but small compared to the external deformation radius. In this limit the baroclinic flow is contained in boundary layers along each side wall, while the barotropic flow is distributed over the width of the channel. Width variations along the channel cause the strength of the barotropic flow to vary and the barotropic variations influence the baroclinic boundary layers in two independent ways. The dual nature of this forcing gives rise to a new type of critical condition which we refer to as a remote control. Virtual and narrows controls also arise. Steady solutions can be obtained by solving a pair of simple quadratic equations and examples are given showing various combinations of controls.Woods Hole Oceanographic Institution Contribution No. 7252.  相似文献   

Turbulence Modelling of A Lock-Release Oil Slick     

陈国谦张立柱  李行伟 《中国海洋工程》2006,20(1):123-132

1 .IntroductionWiththe rapidincrease inthe scale of offshore oil depletion and marine oil transport ,the devas-tating and obnoxious effects of marine oil pollution due to oil spills become a matter of internationalconcern,and corresponding numerical simul…  相似文献   

海水液压水下作业工具系统的微生物污染和腐蚀   总被引：2，自引：0，他引：2  

刘银水  杨曙东  李壮云 《海洋技术学报》2002,21(1):49-52

海水液压水下作业工具直接用海水作为工作介质，具有许多用油作价质所不可比拟的优点。然而，用海水作为工作介质也面临着许多挑战，微生物的污染和腐蚀即是其中之一。本文在分析微生物造成的危害的基础上，对现有的防止办法进行了分析和比较，并提出了防止水下作业工具系统生物污染和腐蚀的措施。  相似文献   

Turbulent Evolution and Energetics of Lock-Release Gravity Currents     

林雯煊陈国谦  朱金波李植 王冠香 《中国海洋工程》2006,20(3):491-498

1 .Introduction Atypical case of gravity currents (Simpson,1997) that has been studied frequentlyis the lock-release gravity current .Asillustratedin Fig.1 ,twofluids of different densities are placedinarectan-gular channel ,beinginitially at rest andsepa…  相似文献   

Characterizing supraglacial meltwater channel hydraulics on the Greenland Ice Sheet from in situ observations          下载免费PDF全文

Colin J. Gleason  Laurence C. Smith  Vena W. Chu  Carl J. Legleiter  Lincoln H. Pitcher  Brandon T. Overstreet  Asa K. Rennermalm  Richard R. Forster  Kang Yang 《地球表面变化过程与地形》2016,41(14):2111-2122

Supraglacial rivers on the Greenland Ice Sheet (GrIS) transport large volumes of surface meltwater toward the ocean, yet have received relatively little direct research. This study presents field observations of channel width, depth, velocity, and water surface slope for nine supraglacial channels on the south‐western GrIS collected between July 23 and August 20, 2012. Field sites are located up to 74 km inland and span 494–1485 m elevation, and contain measured discharges larger than any previous in situ study: from 0.006 to 23.12 m³/s in channels 0.20 to 20.62 m wide. All channels were deeply incised with near vertical banks, and hydraulic geometry results indicate that supraglacial channels primarily accommodate greater discharges by increasing velocity. Smaller streams had steeper water surface slopes (0.74–8.83%) than typical in terrestrial settings, yielding correspondingly high velocities (0.40–2.60 m/s) and Froude numbers (0.45–3.11) with supercritical flow observed in 54% of measurements. Derived Manning's n values were larger and more variable than anticipated from channels of uniform substrate, ranging from 0.009 to 0.154 with a mean value of 0.035 ± 0.027 despite the absence of sediment, debris, or other roughness elements. Ubiquitous micro‐depressions in shallow sections of the channel bed may explain some of these roughness values. However, we find that other, unobserved sources of flow resistance likely contributed to these elevated Manning's n values: future work should explicitly consider additional sources of flow resistance beyond bed roughness in supraglacial channels. We conclude that hydraulic modeling for these channels must allow for both subcritical and supercritical flow, and most importantly must refrain from assuming that all ice‐substrate channels exhibit similar hydraulic behavior, especially for Froude numbers and Manning's n. Finally, this study highlights that further theoretical and empirical work on supraglacial channel hydraulics is necessary before broad scale understanding of ice sheet hydrology can be achieved. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Modelling extraordinary floods and sedimentological processes in a large channel-floodplain system of the Lower Paran River(Argentina)   总被引：1，自引：0，他引：1  

Marina L.Garcia  Pedro A.Basile  Gerardo A.Riccardi  José F.Rodriguez 《国际泥沙研究》2015,(2):150-159

A quasi-2D unsteady flow and sediment transport model suitable for the simulation of large lowland river systems,including their floodplains,is presented.The water flow and sediment equations are discretised using an interconnected irregular cells scheme,in which different simplifications of the 1D de Saint Venant equations are used to define the discharge laws between cells.Spatially-distributed transport and deposition of fine sediments throughout the river-floodplain system are simulated.The model is applied over a 208-km reach of the Parana River between the cities of Diamante and Ramallo(Argentina) comprising a river-floodplain area of 8100 km~2.After calibration and validation,the model is applied to predict water and sediment dynamics during synthetically generated extraordinary floods of100,1000,and 10,000 years return period.The potential impact of a 56-km long road embankment constructed across the entire floodplain is simulated and compared to model results without the embankment.The embankment results in increases in upstream water levels,inundation extent,flow duration,and sediment deposition.  相似文献   

Suspended load in flows on erodible bed   总被引：1，自引：0，他引：1  

Sujit K. BOSE  Subhasish DEY 《国际泥沙研究》2009,24(3):315-324

Steady state suspended-load of sediment transported in flow over erodible beds usually is treated by the advection-diffusion approach, though in recent years, it is being treated as a two-phase flow phenomenon incorporating kinetics of sediment particles. Among the advection-diffusion approaches, Rouse＇s equation is the well-known, although a number of researchers in later periods have attempted to improve it by modifying the mixing length concept taking into account other aspects. In this paper, the advection-diffusion approach and associated logarithmic law of flow velocity are revisited. It is concluded from the logarithmic law that the Reynolds shear stress is a linear function of height above the bed, which reduces to bed shear stress in the case of a long horizontal channel. As a consequence, it is shown that the volumetric concentration of sediment is best approximated by the sum of two power laws of height above the bed. An equation is derived for the suspended-load transport rate in terms of elementary functions.  相似文献   

Reconstructing extreme post‐wildfire floods: a comparison of convective and mesoscale events          下载免费PDF全文

Daniel J. Brogan  Peter A. Nelson  Lee H. MacDonald 《地球表面变化过程与地形》2017,42(15):2505-2522

In much of western United States destructive floods after wildfire are frequently caused by localized, short‐duration convective thunderstorms; however, little is known about post‐fire flooding from longer‐duration, low‐intensity mesoscale storms. In this study we estimate and compare peak flows from convective and mesoscale floods following the 2012 High Park Fire in the ungaged 15.5 km² Skin Gulch basin in the northcentral Colorado Front Range. The convective storm on 6 July 2012 came just days after the wildfire was contained. Radar data indicated that the total rainfall was 20–47 mm, and the maximum rainfall intensities (upwards of 50 mm h^?1) were concentrated over portions of the watershed that burned at high severity. The mesoscale storm on 9–15 September 2013 produced 220–240 mm of rain but had maximum 15‐min intensities of only 25–32 mm h^?1. Peak flows for each flood were estimated using three independent techniques. Our best estimate using a 2D hydraulic model was 28 m³ s^?1 km^?2 for the flood following the convective storm, placing it among the largest rainfall‐runoff floods per unit area in the United States. In contrast, the flood associated with the mesoscale flood was only 6 m³ s^?1 km^?2, but the long‐duration flood caused extensive channel incision and widening, indicating that this storm was much more geomorphically effective. The peak flow estimates for the 2013 flood had a higher relative uncertainty and this stemmed from whether we used pre‐ or post‐flood channel topography. The results document the extent to which a high and moderate severity forest fire can greatly increase peak flows and alter channel morphology, illustrate how indirect peak flow estimates have larger errors than is generally assumed, and indicate that the magnitude of post‐fire floods and geomorphic change can be affected by the timing, magnitude, duration, and sequence of rainstorms. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Soil erosion by surface water flow on a stony,semiarid hillslope     

M. A. Nearing  J. R. Simanton  L. D. Norton  S. J. Bulygin  J. Stone 《地球表面变化过程与地形》1999,24(8):677-686

Soil erosion on hillslopes occurs by processes of soil splash from raindrop impacts and sediment entrainment by surface water flows. This study investigates the process of soil erosion by surface water flow on a stony soil in a semiarid environment. A field experimental method was developed whereby erosion by concentrated flow could be measured in predefined flow areas without disturbing the soil surface. The method allowed for measurements in this study of flow erosion at a much wider range of slopes (2·6 to 30·1 per cent) and unit discharge rates (0·0007 to 0·007 m2 s−1) than have been previously feasible. Flow velocities were correlated to discharge and hydraulic radius, but not to slope. The lack of correlation between velocity and slope might have been due to the greater rock cover on the steeper slopes which caused the surface to be hydraulically rougher and thus counteract the expected effect of slope on flow velocity. The detachment data illustrated limitations in applying a linear hydraulic shear stress model over the entire range of the data collected. Flow detachment rates were better correlated to a power function of either shear stress (r2 = 0·51) or stream power (r2 = 0·59). Published in 1999 by John Wiley & Sons, Ltd.  相似文献   

Competition between topography- and compaction-driven flow in a confined aquifer: Some analytical results   总被引：1，自引：0，他引：1  

Henk Kooi 《Hydrogeology Journal》1999,7(3):245-250

 An analysis is presented of the competition between topography- and compaction-driven flow in a confined aquifer. The aquifer crops out and is unconfined in an area with an elevated water table. In the absence of compaction, the elevated water table drives the flow toward areas with a lower water table, and leakage occurs from the aquifer through an overlying aquitard. Under these conditions, recharge occurs in the outcrop area. When sedimentation occurs above the aquifer away from the outcrop area, compaction tends to reverse the flow direction in the aquifer, causing expulsion of groundwater in the outcrop area. The actual flow field arises from the competition between the two driving mechanisms. An analytical expression for the combined flow field is derived in which the contribution from both mechanisms is apparent. The expression is useful as a practical guideline for estimating whether or not compaction can be safely ignored in regional groundwater-flow studies of confined aquifers. Received, July 1998 / Revised, February 1999 / Acccepted, February 1999  相似文献