No (235)
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235
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Long-term hydroecological monitoring in the Krkonoše Mts
Tesař, Miroslav; Šír, Miloslav
2013 - English
The cloud and fog water deposition proved to be important delivery mechanism for both water and pollutants in mountainous headwater regions. A fogwater study has been conducted in the Krkonoše Mts. since 1999 till the present time. The sampling site for the observation and evaluation occult precipitation in the Western region was established in the Modrý potok basin (1010–1554 m a.s.l., 2.62 km2) at the highest point of the watershed (passive cloud and fog water collector) while the bulk precipitation and throughfall samplers were installed near to the closure profile of the basin. Rain gauges are evenly situated at six altitudes of the watershed (from 1020 to 1365 m a. s. l.). In the Eastern region the both passive and active collectors were installed close to the Labská bouda chalet (1325 m a.s.l). The active collector (Eigenbrodt, Germany) is operated automatically by the PWD-11 sensor (Vaisala, Finland). Collected samples were stored in polyethylene bottles and transported as soon as possible to the laboratories of the Czech Geological Survey and Geological Institute of ASCR to the chemical analyses. The results for 1999–2011 will be presented in this article. A wide range of concentrations were encountered, most typically exceeding concentrations occurring in rain (so-called enrichment factors were evaluated) and the estimated wet deposition of the most important chemical compounds were calculated and compared with respect to weighted means of bulk precipitation collected in the open area. Based on the model predictions and on the water balance of the forest canopy the annual occult precipitation total for the Krkonoše Mts. was estimated by 20–25 % of the annual falling precipitation total. The research is supported by the Czech Science Foundation (205/09/1918).
Keywords:
occult precipitation; cloud and fog water deposition; water chemistry
Available at various institutes of the ASCR
Long-term hydroecological monitoring in the Krkonoše Mts
The cloud and fog water deposition proved to be important delivery mechanism for both water and pollutants in mountainous headwater regions. A fogwater study has been conducted in the Krkonoše Mts. ...
Coarse-grained particles conveying along a pipe bed
Vlasák, Pavel; Chára, Zdeněk; Konfršt, Jiří; Kysela, Bohuš
2013 - English
The paper describes the results of a flow visualisation of model coarse-grained fully stratified particle-water mixtures. Investigation was focussed on study of the particle behaviour and carrier liquid and conveyed particles local velocities. Glass balls and washed graded pebble gravel of mean diameter of 6 mm were conveyed by water in a horizontal smooth pipe loop with a transparent pipe viewing section of inner diameter 40 mm. Particle movement along the pipe invert and particulate stationary bed, created by two layers of spherical particles of the same size as the conveyed particles, was studied. The effect of stationary bed on local velocity values of the carrier liquid and conveyed particles were determined. It was conducted that the maximum liquid velocity is significantly shifted from pipe centre to a higher position in the flow pattern with stationary bed.
Keywords:
coarse-grained slurry; flow structure; visualisation; liquid local velocity; particle velocity; rychlost; částice
Available at various institutes of the ASCR
Coarse-grained particles conveying along a pipe bed
The paper describes the results of a flow visualisation of model coarse-grained fully stratified particle-water mixtures. Investigation was focussed on study of the particle behaviour and carrier ...
Early warning system for flash floods in the Krkonoše Mts
Tesař, Miroslav; Šír, Miloslav
2013 - English
The present contribution describes a sophisticated local warning system (LWS) for detection of local flash floods that is built in the Krkonoše Mts. in the upper of the Úpa river with the closing profile at Horní Maršov (573–1602 m a.s.l., 81.70 km2). This system is based on the new knowledge of the discontinuous character of water transport in an unsaturated zone and involves: (i) instrumentation: (1) stream gauge monitoring stations with data transfer to the internet, (2) monitoring stations (equipped by rain gauge, air and soil thermometers, soil water tensiometers and soil moisture meters) with data transfer to the internet, (ii) software: (1) the internal software of the stream gauge and monitoring stations for the measurement, storage and transfer the data to the dispatching centre, (2) software of a central data repository, (3) software for data transmission in the internet browser, (3) software for the forecasting of flood risk and sending flood alert, (iii) dispatching centre: (1) operating of the data repository, (2) forecasting of the water level for the each of connected stream gauge station, (3) sending flood alert, (iv) handbooks and user’s Guides: (1) hydrological and soil surveying, (2) LWS design, (3) operation and maintenance of the LWS, (v) complete projection documentation of the LWS, (vi) installation of the LWS in a catchment, (vii) testing and routine operation of the LWS. The described LWS is supported by the Technology Agency of the Czech Republic (Project TA02021451).
Keywords:
early warning system; flash flood; surface and soil water monitoring
Available at various institutes of the ASCR
Early warning system for flash floods in the Krkonoše Mts
The present contribution describes a sophisticated local warning system (LWS) for detection of local flash floods that is built in the Krkonoše Mts. in the upper of the Úpa river with the closing ...
Improvements of saltation model
Kharlamova, Irina; Vlasák, Pavel
2013 - English
The present paper introduces a new model of a bed-load transport. The model simulates a particle motion in the channel with turbulent flow and rough bed. The effects of mutual interaction of conveyed particles with carrier liquid, with bed particles, and also with other conveyed particles are taken into account. The model predicts average saltation characteristics, e.g. saltation length and height, particles distribution in vertical direction, and mass rate of conveyed particles per unit area of channel bed.
Keywords:
částice; modely
Available at various institutes of the ASCR
Improvements of saltation model
The present paper introduces a new model of a bed-load transport. The model simulates a particle motion in the channel with turbulent flow and rough bed. The effects of mutual interaction of conveyed ...
Saltation of sand in vicinity of cylindrical column
Kharlamova, Irina; Kharlamov, Alexander; Vlasák, Pavel
2013 - English
The paper presents a model of sand sediment transport in water stre am in vicinity of a high cylindrical col umn. It is assumed that an averaged turbulent flow is horizontally layered in vicinity of the cylinder. In ea ch layer the flow around the cylinder is modelled as a potential flow generated by a vertical dipole line. Flow in viscous sub-layer on the surface of the cylinder is neglected. The presented flow model is approximate; however it is simple for use. Trajectories of saltating particles near the cylinder were calculated. Further investigation of such flow will allow a determination of zones where solid particles will collide with the column. That might be useful for prevention of its damage or destruction
Keywords:
saltation of sand; flow around cylinder; logarithmic profile; dipole line; averaged turbulent flow
Available on request at various institutes of the ASCR
Saltation of sand in vicinity of cylindrical column
The paper presents a model of sand sediment transport in water stre am in vicinity of a high cylindrical col umn. It is assumed that an averaged turbulent flow is horizontally layered in ...
Extreme runoffs from the Modrý důl basin in the vegetation season
Šír, Miloslav; Tesař, Miroslav; Dvořák, Igor
2013 - English
The main objective of the present article is to advance understanding of the complex role of various vegetation cover in extreme runoff formation in the Modrý potok basin. This watershed (1010–1554 m a.s.l., 2.62 km2) is situated in the northern part of the Czech Republic in the eastern part of the Krkonoše Mts. The soil types are the mountainous Podzole and Lithosol with a thin humic layer on crystalline bedrock. Monitoring stations with data transfer to the internet are installed on several localities differing in the type of vegetation cover (in the grassland and dwarf pine above the forest margin, in the growth of mature spruce forest, and in the grassland below the spruce forest). The discharge at the closing profile is continuously recorded. Meteorological data are collected at a station close to the Výrovka chalet (1360 m a.s.l.): year-round precipitation, solar radiation, wind speed and direction, air and soil temperatures and soil moisture. The long-term monitoring of the water balance of the headwater catchment Modrý potok and its soil water regime was evaluated taking into account the discontinuous character of water transport in an unsaturated zone. Extreme runoffs in a vegetation season are caused by these factors: (1) oversaturation of the soil profile, (2) water repellency of the soil surface, (3) gravitationally destabilized flow of water in the soil profile, (4) extreme rainfall. The typical combinations are (1) and (3) – gravitationally destabilized flow of water can be caused even by a small rainfall under the oversaturation, (2) and (4) – long-term drought can cause the water repellency of the soil surface and the extreme rainfall. The research is supported by the Czech Science Foundation (205/09/1918) and by the Technology Agency of CR (TA02021451).
Keywords:
surface runoff formation; headwater catchment; water balance; soil water monitoring
Available at various institutes of the ASCR
Extreme runoffs from the Modrý důl basin in the vegetation season
The main objective of the present article is to advance understanding of the complex role of various vegetation cover in extreme runoff formation in the Modrý potok basin. This watershed (1010–1554 ...
Oblique collisions of non-rotating spherical particles with a wall
Chára, Zdeněk; Vlasák, Pavel; Kysela, Bohuš
2013 - English
In the present paper non-rotating particle-wall collisions were experimentally investigated. By means of the PIV method a velocity field around falling spheres was analyzed. It was shown that the wake behind the particle which approached a bed in non-normal direction was asymmetrical and after the impact the wake passed the particle only along one side. This non-symmetrical velocity field resulted in additional forces which pushed the particle to an opposite direction than was the direction of the particle motion just after the impact.
Keywords:
wake; particle trajectory; velocity field
Available on request at various institutes of the ASCR
Oblique collisions of non-rotating spherical particles with a wall
In the present paper non-rotating particle-wall collisions were experimentally investigated. By means of the PIV method a velocity field around falling spheres was analyzed. It was shown that the ...
Numerical model of saltation in open channel with rough bed
Kharlamova, Irina; Vlasák, Pavel
2012 - English
The present contribution deals with a numerical modelling of a saltation of solid spherical particle in turbulent flow along rough bed in the open channel. The goal of the research is to obtain the dependences of average characteristics of particle saltation motion (as length and height of one particle jump) on flow parameters (which can be characterized e.g. by shear velocity and water depth) and bed roughness. The suggested dependences and calculated results are compared with analogical relationships introduced by other authors in literature.
Keywords:
saltation length; saltation height; bed roughness; bed shear stress; shear velocity
Available on request at various institutes of the ASCR
Numerical model of saltation in open channel with rough bed
The present contribution deals with a numerical modelling of a saltation of solid spherical particle in turbulent flow along rough bed in the open channel. The goal of the research is to obtain the ...
Collision of a rotating spherical particle with flat wall in liquid
Lukerchenko, Nikolay; Kvurt, Y.; Chára, Zdeněk; Vlasák, Pavel
2012 - English
The collision of the rotating spherical particle with a flat wall in liquid was studied experimentally. The glass and steel beads rotating in water and silicon oil were used. A high-speed video system recorded the bead motion before and after the collision. It was shown that the restitution coefficient depends not only on the Stokes number but also on the particle angular velocity; the restitution coefficient decreases with increasing of the rotational Reynolds number and decreasing of the Stokes number. These results can be useful in modelling of the two-phase flows near solid boundaries.
Keywords:
restitution coefficient; spherical particle; particle rotation; liquid viscosity
Available on request at various institutes of the ASCR
Collision of a rotating spherical particle with flat wall in liquid
The collision of the rotating spherical particle with a flat wall in liquid was studied experimentally. The glass and steel beads rotating in water and silicon oil were used. A high-speed video system ...
Dependence of saltation parameters on bed roughness and bed porosity
Kharlamova, Irina; Vlasák, Pavel
2012 - English
In numerical models of bed load transport a bed structure of channel could be described by two parameters, a size of bed particles and a standard deviation of normal distribution of bed particles in the vertical direction. The present paper deals with the effect of bed parameters on average length and height of one jump of saltating particle. A new formula was proposed for bed roughness based on size and standard deviation of the normal distribution of the bed particles. The dependences of length and height of the jump on the diameter of the saltating and bed particles were determined for different variation of vertical distribution of the bed particles.
Keywords:
saltation parameters; saltation length; saltation height; bed structure; normal distribution of bed particles; bed roughness
Available on request at various institutes of the ASCR
Dependence of saltation parameters on bed roughness and bed porosity
In numerical models of bed load transport a bed structure of channel could be described by two parameters, a size of bed particles and a standard deviation of normal distribution of bed particles in ...
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