As has often been observed in the literature, an utterance of a generic such as ‘Boys don’t cry’ can convey a normative behavioral rule that applies to boys, roughly: that boys shouldn’t cry. This observation has led many authors to the claim that generics are ambiguous: they allow both for a descriptive as well as a normative reading. The present paper argues against this common assumption: it argues that the observation in question should be addressed at the level of pragmatics, rather than at the level of semantics. In particular, the paper argues that the normative force of utterances of generics results from the presence of a conversational implicature. This result should somewhat alleviate the task of finding a proper semantic analysis of generics since it shows that at least one of their intriguing features need not be reflected in their truth-conditions.
Management of reservoirs for drinking water supply should be based on a thorough knowledge of water quality changes within variable conditions of hydrology, climate, nutrient loading and water storage. The two-dimensional longitudinal water quality model CE-QUAL-W2 was tested for its ability to predict concentrations of organic matter and trophic conditions in Rimov Reservoir, a small dimictic reservoir (volume 33,000,000 m3, maximum depth 43 m, hydraulic retention time 40 to 160 d) suffering from seasonally increased concentrations of humic substances and symptoms of eutrophication. The model was calibrated on two seasonal courses differing in hydrology and validated on a 1074 day period. The averages of absolute mean errors between simulated and measured vertical profiles of temperature, and concentrations of dissolved organic matter, dissolved oxygen and chlorophyll a in the validation run were 0.9 °C, 0.8 mg l-1, 1.2 mg l-1 and 0.008 mg l-1, respectively. Analysis of results and sensitivity analysis of modelling phytoplankton and phosphorus showed suitability of the mathematical description of their dynamics in the photic zone but not in the deeper layers. In spite of this partial problem, the model was found appropriate for the reliable predictions of water quality dynamics in Rimov Reservoir. and Hospodaření s vodou ve vodárenských nádržích by mělo být založeno na podrobné znalosti vlivu hydrologických, klimatických a limnologických veličin na kvalitu vody. Možnosti matematického modelování změn kvality vody byly testovány pro nádrž Římov na Malši za pomoci dvourozměrného modelu kvality vody CE-QUAL-W2. Model byl zkalibrován na dvou sezónních řadách dat pro hydrologicky různá období a poté byl uplatněn na 1074-denní řadě dat. Byly vyhodnoceny rozdíly mezi měřenými a simulovanými vertikálními profily teploty, koncentrací rozpuštěných organických látek, rozpuštěného kyslíku a chlorofylu. Tyto rozdíly vyjádřené jako velikost absolutní střední chyby byly 0,9 °C, 0,8 mg l-1 , 1,2 mg l-1 a 0.008 mg l-1 . Analýza získaných výsledků a citlivostní analýza modelu ukazují dobrou shodu mezi naměřenou a simulovanou dynamikou zmíněných veličin v eufotické zóně, v nižších a tmavších vrstvách nádrže dochází k nárůstu odchylek modelu od reality. Přes tyto dílčí problémy byl model shledán jako užitečný a nenahraditelný pomocník při úlohách řešících dopad vnějších vlivů na kvalitu vody v nádrži.
This paper reports the processes by which a single-phase 3-D CFD model of hydrodynamics in a 17-km-long dam reservoir was developed, verified and tested. A simplified VOF model of flow was elaborated to determine the effect of wind on hydrodynamics in the lake. A hexahedral mesh with over 17 million elements and a k-ω SST turbulence model were defined for single-phase simulations in steady-state conditions. The model was verified on the basis of the extensive flow measurements (StreamPro ADCP, USA). Excellent agreement (average error of less than 10%) between computed and measured velocity profiles was found. The simulation results proved a strong effect of wind on hydrodynamics in the lake, especially on the development of the water circulation pattern in the lacustrine zone.
The paper describes a 3D numerical model of the spherical particle saltation. Two stages of particle saltation were distinguished - the particle free motion in water and the particle-bed collision. The particle motion consists of the translational and rotational particle motion. A stochastic method of calculation of the particle-bed collision was developed. The collision height and the contact point were defined as random variables. Impulse equations were used and the translational and angular velocity components of the moving particle immediately after the collision were expressed as functions of the velocity components just before the collision. The dimensionless coefficients of the drag force and drag torque were determined as functions of both translational and rotational Reynolds numbers. The model is in good agreement with known experimental data. Examples of calculation of the particles’ lateral dispersion and the mean absolute values of the deviation angle of the particle trajectory are presented. and Studie popisuje 3D numerický model saltačního pohybu kulovité částice, v němž jsou uvažována dvě fáze saltačního pohybu - volný pohyb částice v proudící vodě a kolise částice se dnem. Model počítá s translačním i rotačním pohybem částice. Byla vyvinuta stochastická metoda výpočtu kolise částice se dnem. Kolizní výška a kontaktní bod byly definovány jako náhodné proměnné. Byla použita soustava momentových rovnic a složky translační a rotační rychlosti pohybující se částice po kolizi byly vyjádřeny jako funkce složek rychlosti těsně před kolizí. Bezrozměrné koeficienty odporu částice a odporu rotující částice byly určeny jako funkce translačního i rotačního Reynoldsova čísla částice. Výsledky modelu jsou v dobré shodě se známými experimentálními daty. Studie presentuje příklady výpočtu příčné disperze částice a střední absolutní hodnoty deviačního úhlu trajektorie částice.
In the marine ecological system, the prime role of water management and durability of an ecosystem is being played by the vegetation patches. The vegetation patches in open channels can significantly affect the flow velocity, discharge capacity and hinder energy fluxes, which ultimately helps in controlling catastrophic floods. In this study, the numerical simulation for turbulent flow properties, i.e. velocity distribution, Reynolds stresses and Turbulent Intensities (TI) near the circular vegetation patches with progressively increasing density, were performed using the computational fluid dynamics (CFD) code ANSYS FLUENT. For examination of the turbulent flow features in the presence of circular patches with variable densities, Reynolds averaged Navier-Stokes equations, and Reynolds stress model (RSM) were employed. The numerical investigation was performed in the presence of in-line emergent and submerged patches having variable vegetation density in the downstream direction. Two of the cases were investigated with three circular patches having a clear gap to patch diameter ratio of La/D = 1 (where La is the clear spacing between the vegetation patches and D is the diameter of the circular patch), and the other two cases were analyzed with two patches having a clear gap ratio of La/D = 3. The case with a clear gap ratio (La/D = 3) showed 10.6% and 153% inflation in the magnitude of longitudinal velocity at the downstream of the sparse patch (aD = 0.8) and upstream of the dense patch (aD = 3.54), respectively (where aD is the flow blockage, in which “a” represents the patch frontal area and “D” represents the patch diameter). The velocity was reduced to 94% for emergent and 99% for submerged vegetation due to successive increase in vegetation density made by introducing a middle patch which reduced the clear gap ratio (La/D = 1). For La/D = 1, the longitudinal velocities at depth z = 15cm were increased by 319% than at depth z = 6cm at the downstream of the dense patch (aD = 3.54). Whereas it was observed to 365% higher in the case of La/D = 3. The magnitude of turbulent characteristics was observed 36% higher for submerged vegetation cases having a clear gap ratio of La/D = 1. The successive increase in the patch density reduced the Reynolds stresses, turbulent kinetic energy and turbulent intensities significantly within the gap region. The major reduction in the flow velocities and turbulent properties in the gaps provides a stable environment for aquatic ecosystems nourishment and fosters sediment deposition, and supports further vegetation growth.
Monthly evapotranspiration (ET) rates over Hungary for 2000-2008 are mapped at a spatial scale of about 1 km with the help of MODIS daytime land surface temperature as well as sunshine duration, air temperature and humidity data. Mapping is achieved by a linear transformation of MODIS daytime land surface temperature values employing the complementary relationship of evaporation. Validation of the ET rates has been performed at spatial scales spanning almost three magnitudes from a few hundred meters to about a hundred kilometers employing eddy-covariance (EC) measurements and catchment water balance closures. Typically the unbiased ET estimates are within 15 % of EC values at a monthly basis, within 7 % at an annual, and within only a few percent at a multi-year basis. The ET estimates yield an especially remarkable match (relative error of 0.2 %, R2 = 0.95) with high-tower EC measurements at a monthly basis. The spatial distribution of the ET estimates confirm earlier, complex regional hydrologic model results and observations as well as yields a perfect estimate of the country’s precipitation recycling index (the ratio of the multi-year mean ET and precipitation rates spatially aggregated for the whole country) of 89.2 % vs an observed value of 89.6 %. The CREMAP method is very simple, easy to implement, requires minimal data, calibration-free, and works accurately when conditions for the complementary relationship are met. and Pomocou údajov ročlenených podľa MODIS (moderate resolution imaging spectroradiometer), s využitím dennej povrchovej teploty, trvania slnečného svitu, teploty vzduchu a jeho vlhkosti boli zostrojené mapy mesačnej evapotranspirácie (ET) Maďarska pre roky 2000-2008 s priestorovým rozlíšením približne 1 km. Mapovanie bolo zrealizované lineárnou transformáciou MODIS dennej teploty povrchu s uvážením doplňujúceho vzťahu pre evapotranspiráciu CR, navrhnutou Bouchetom (1963). Výsledky dosiahnuté touto metódou boli verifikované v priestorovej mierke pokrývajúcej tri rády od niekoľkých stoviek metrov po stovky kilometrov, použijúc merania metódou pulzácií (eddy covariance, EC), a bilanciou vody v koncovom profile povodí. Typicky, hodnoty ET sú v medziach 15 % mesačných hodnôt EC a 7 % ročných hodnôt a len v medziach niekoľkých percent viacročných hodnôt evapotranspirácie, ktoré boli určené inými metódami. Hodnoty ET sú v dobrej zhode s výsledkami meraní ET na vysokej veži metódou EC (relatívna chyba 0.2 %, R2 = 0,95). Priestorové rozdelenia vypočítaných hodnôt ET potvrdzujú predchádzajúce výsledky modelovania regionálnymi modelmi, ako aj hodnoty indexu recyklácie zrážok krajiny (precipitation recycling index), čo je pomer mnohoročnej priemernej ET a zrážok agregovaných v krajine, s hodnotou 89,2 % vs pozorovaná hodnota 89,6 %. Metóda CREMAP je jednoduchá, ľahko implementovateľná, vyžaduje minimum vstupných hodnôt, nie je ju potrebné kalibrovať a keď sú splnené podmienky jej použiteľnosti, je aj dostatočne presná.
In order to fulfil their essential roles as the bearers of truth and the relata of logical relations, propositions must be public and shareable. That requirement has favoured Platonist and other non-mental views of them, despite the well-known problems of Platonism in general. Views that propositions are mental entities have correspondingly fallen out of favour, as they have difficulty in explaining how propositions could have shareable, objective properties. We revive a mentalist view of propositions, inspired by Artificial Intelligence work on perceptual algorithms, which shows how perception causes persistent mental entities with shareable properties that allow them to fulfil the traditional roles of (one core kind of) propositions. The clustering algorithms implemented in perception produce outputs which are (implicit) atomic propositions in different minds. Coordination of them across minds proceeds by game-theoretic processes of communication. The account does not rely on any unexplained notions such as mental content, representation, or correspondence (although those notions are applicable in philosophical analysis of the result).
Serious damage may occur to concrete hydraulic structures, such as water galleries, spillways, and stilling basins, due to the abrasive erosion caused by the presence of solid particles in the flow. This underlines the importance of being capable in providing characterization of the concrete from the point of view of its vulnerability to abrasive erosion, in order to improve the design of the structure and the material selection. Nevertheless, the existing apparatus for concrete abrasive erosion testing are either far from allowing realistic simulation of the actual environment in which this phenomenon occurs, or show a large degree of complexity and cost. An alternative method has been developed with the aid of Computational Fluid Dynamics (CFD). CFD was first employed to verify the effectiveness of a new laboratory equipment. Afterwards, a parameter has been introduced which, by successful comparison against preliminary experiments, proved suitable to quantify the effect of the fluid dynamic conditions on the concrete abrasive erosion, thereby opening the way to CFD-based customization of the apparatus. In the future, the synergy of numerical and physical modelling will allow developing predictive models for concrete erosion, making it possible to reliably simulate real structures.
A number of correlations for friction factor determinations in smooth pipes have been proposed in the past decades. The accuracy and applicability of these friction factor formulas should be examined. Based on this notion the paper is designed to provide a comparative study of friction factor correlations in smooth pipes for all flow regimes of Bingham fluids. Nine models were chosen. The comparisons of the selected equations with the existing experimental results, which are available in the literature, were expressed through MARE, MRE+ , MRE- , RMSE, Ѳ, and S. The statistical comparisons were also carried out using MSC and AIC. The analyses show that the Wilson-Thomas (1985) and Morrison (2013) models are best fit models to the experimental data for the Reynolds number up to 40000. Within this range, both models can be used alternately. But beyond this Re value the discrepancy of the Wilson-Thomas model is higher than the Morrison model. In view of the fact that the Morrison model requires fewer calculations and parameters as well as a single equation is used to compute the friction factor for all flow regimes, it is the authors’ advice to use this model for friction factor estimation for the flow of Bingham fluids in smooth pipes as an alternative to the Moody chart and other implicit formulae.
Physicalism demands an explication of what it means for something to be physical. But the most popular way of providing one—viz., characterizing the physical in terms of the postulates of a scientifically derived physical theory—is met with serious trouble. Proponents of physicalism can either appeal to current physical theory or to some future physical theory (preferably an ideal and complete one). Neither option is promising: currentism almost assuredly renders physicalism false and futurism appears to render it indeterminate or trivial. The purpose of this essay is to argue that attempts to characterize the mental encounter a similar dilemma: currentism with respect to the mental is likely to be inadequate or contain falsehoods and futurism leaves too many significant questions about the nature of mentality unanswered. This new dilemma, we show, threatens both sides of the current debate surrounding the metaphysical status of the mind.
This paper deals with the application of a fluidized layer of granular material (FLGM) for the direct separation of destabilized impurities during drinking water treatment. Further, it investigates the effect of operation parameters (fluidized layer grain size, technological arrangement, velocity gradient, retention time, dosage of destabilisation reagent and temperature) on the aggregation and separation efficiency of the layer. The tests were carried out in a pilot plant scale. Aluminium sulphate was used as the destabilisation reagent. The highest separation efficiencies were achieved, when the particles entered the fluidized layer immediately after the dosing of the destabilisation reagent, when they had the lowest degree of aggregation. The separation efficiency (ϕ) also increased with increasing velocity gradient and the maximal value was reached at the velocity gradient of about 250 s-1. The most efficient separation of aluminium was achieved at 5 °C, but the effect of temperature on the efficiency of organic matter separation (ϕTOC) was not very significant. The maximal efficiency of separation on the layer grains reached the values ϕAl = 0.81 at the optimal dosage DAl = 1.55 mg L-1 and ϕTOC = 0.31 at the optimal dosage DAl = 2.36 mg L-1. The indisputable advantage of using FLGM for the separation of impurities is that they are intercepted on the layer grains in a form of solid, water-free shell (or coat) with the density of 2450 kg m-3, and there is no need to deal with the sludge dewatering. and Příspěvek se zabývá využitím fluidní vrstvy zrnitého materiálu (FLGM) pro přímou separaci destabilizovaných nečistot při úpravě vody a vlivem provozních parametrů (velikost zrn náplně, technologické uspořádání, gradient rychlosti, doba zdržení, dávka destabilizačního činidla, teplota) na agregační a separační účinnost vrstvy. Testy byly prováděny na poloprovozním modelu fluidní vrstvy. Jako destabilizační činidlo byl použit síran hlinitý. Nejvyšší separační účinnosti byly dosahovány, pokud částice nečistot vstupovaly do fluidní vrstvy bezprostředně po nadávkování destabilizačního činidla, kdy byl jejich stupeň agregace nejnižší. Separační účinnost (ϕ) se také zvyšovala s narůstající hodnotou gradientu rychlosti ve fluidní vrstvě a maximální hodnoty dosáhla při gradientu kolem 250 s-1. Hliník byl nejúčinněji separován při nízké teplotě (5 °C), nicméně na účinnost separace organických látek (ϕTOC) teplota příliš velký vliv neměla. Maximální účinnost separace na zrnech fluidní vrstvy dosáhla hodnot ϕAl = 0,81 při optimální dávce DAl = 1,55 mg L-1 a ϕTOC = 0,31 při optimální dávce DAl = 2,36 mg L-1. Nespornou výhodou využití fluidní vrstvy jako separačního prvku je skutečnost, že nečistoty jsou na zrnech FLGM zachycovány ve formě pevné skořápky (hustota 2450 kg m-3), která neobsahuje kapalnou vodu, a kal tudíž nemusí být odvodňován.
Slurry transport in horizontal and vertical pipelines is one of the major means of transport of sands and gravels in the dredging industry. There exist 4 main flow regimes, the fixed or stationary bed regime, the sliding bed regime, the heterogeneous flow regime and the homogeneous flow regime. Of course the transitions between the regimes are not very sharp, depending on parameters like the particle size distribution. The focus in this paper is on the homogeneous regime. Often the so called equivalent liquid model (ELM) is applied, however many researchers found hydraulic gradients smaller than predicted with the ELM, but larger that the hydraulic gradient of liquid. Talmon (2011, 2013) derived a fundamental equation (method) proving that the hydraulic gradient can be smaller than predicted by the ELM, based on the assumption of a particle free viscous sub-layer. He used a 2D velocity distribution without a concentration distribution. In this paper 5 methods are described (and derived) to determine the hydraulic gradient in homogeneous flow, of which the last method is based on pipe flow with a concentration distribution. It appears that the use of von Driest (Schlichting, 1968) damping, if present, dominates the results, however applying a concentration distribution may neutralise this. The final equation contains both the damping and a concentration distribution giving the possibility to calibrate the constant in the equation with experimental data. The final equation is flexible and gives a good match with experimental results in vertical and horizontal pipelines for a value of ACv = 1.3. Data of horizontal experiments Dp = 0.05-0.30 m, d = 0.04 mm, vertical experiments Dp = 0.026 m, d = 0.125, 0.345, 0.560, and 0.750 mm.
The paper approaches problem of the flow forecasting for the Liptovska Mara reservoir with a hybrid modelling approach. The nonlinear hybrid modelling framework was investigated under the specific physiographic conditions of the High Core Mountains of Slovakia. The mean monthly flows of rivers used in this study are predominantly fed by snowmelt in the spring and convective precipitation in the summer. Therefore, their hydrological regime exhibits at least two clear seasonal patterns, which provide an intuitive justification for the application of nonlinear regime-switching time series models. Differences in the prevailing geology, orientation of slopes and their exposure to atmospheric circulation for the right and left-sided tributaries of the Vah River indicate that the hydrological regime of mean monthly discharge time series in this area with respect to seasonality and cyclicity may differ, too. Therefore, a simple deterministic water balance scheme was set up for estimating the reservoir inflow from the left and right-sided tributary flows separately. It consists of the linear combination of the measured tributary flows and estimated ungauged tributary flows. The contributions of the ungauged catchments were estimated from flows from gauged tributaries with similar physiographic conditions by weighting these by the ratio of the catchment areas. Separate nonlinear regime-switching time series models were identified for each gauged tributary. The forecasts of the tributaries were combined into a hybrid forecasting model by the water balance model. The performance of the combined forecast, which could better include the specific regime of the time series of tributaries, was compared with the single forecast of the overall reservoir inflow in several combinations. and V štúdii sme porovnávali kvalitu predpovede viacerých lineárnych a nelineárnych modelov časových radov pri predpovedaní prítokov do nádrže Liptovská Mara. Testovali sme výkonnosť modelov ARMA, SETAR na samotnej rieke Váh a v kombinácii jej prítokov do nádrže Liptovská Mara. Ďalej bol uplatnený jednoduchý deterministický model vodnej bilancie pre prítok do nádrže, ktorý pozostáva z lineárnej kombinácie meraných prietokov prítokov Váhu vážených plochou subpovodia. Výber analogónov sa vykonal vzhľadom na podobnosť fyzicko-geografických podmienok v meraných a nemeraných subpovodiach. Modely typu ARMA a SETAR boli zostavené pre každý prítok osobitne a predpovede prietokov na prítokoch boli skombinované modelom vodnej bilancie a do predpovede celkového prítoku do nádrže. Kombinovanú hybridnú predpoveď (stochasticko-deterministická), zachovávajúcu špecifický režim prítokov a vodnej bilancie v povodiach, sme porovnali s predpoveďou celkového prítoku do nádrže získanou pomocou modelov identifikovaných na hlavnom toku.
The paper introduces the test of aggregation as a simple, inexpensive method of evaluating suspension quality during drinking water treatment, suitable for use in both laboratory and operation conditions. The procedure and derivation of the aggregation test is described. The method is used for a demonstration of the influence of mean velocity gradient and mixing time on floc properties formed during the aggregation in a Couette reactor. It was proved that with increasing velocity gradient, the size of the aggregates present in the suspension decreases, and the suspension is substantially more homogeneous than with use of lower gradients. Further, it was confirmed that the size of aggregates reaches the steady state after a specific mixing time, which becomes shorter with increasing value of velocity gradient. and Příspěvek představuje test agregace jako jednoduchou a levnou metodu stanovení kvality suspenze při úpravě vody vhodnou pro použití v laboratorních i provozních podmínkách. Je popsán metodický postup i odvození testu agregace. Metoda je použita pro hodnocení vlivu středního gradientu rychlosti a doby míchání na vlastnosti vytvářených agregátů (vloček) při agregaci v Couettově reaktoru. Bylo prokázáno, že se vzrůstajícím gradientem se snižuje velikost agregátů přítomných v suspenzi a suspenze je značně více homogenní než při použití nízkých gradientů rychlosti. Dále bylo potvrzeno, že velikost agregátů dosahuje po určité době míchání stabilní hodnoty. Čas pro dosažení tohoto ustáleného stavu se zkracuje s rostoucí hodnotou použitého gradientu.
In present paper we assess the climate change impact on mean runoff between the periods 1961-1990 (control period) and 2070-2099 (scenario period) in the Czech Republic. Hydrological balance is modelled with a conceptual hydrological model BILAN at 250 catchments of different sizes and climatic conditions. Climate change scenarios are derived using simple delta approach, i.e. observed series of precipitation, temperature and relative air humidity are perturbed in order to give the same changes between the control and scenario period as in the ensemble of 15 transient regional climate model (RCM) simulations. The parameters of the hydrological model are for each catchment estimated using observed data. These parameters are subsequently used to derive discharge series under climate change conditions for each RCM simulation. Although the differences in the absolute values of the changes in runoff are considerable, robust patterns of changes can be identified. The majority of the scenarios project an increase in winter runoff in the northern part of the Czech Republic, especially at catchments with high elevation. The scenarios also agree on a decrease in spring and summer runoff in most of the catchments. and V článku předkládáme výsledky modelování změn hydrologického režimu v důsledku změn klimatu mezi časovými obdobími 1961-1990 a 2070-2099 podle souboru patnácti regionálních klimatických modelů pro 250 povodí v České republice. Hydrologická bilance byla modelována pomocí konceptuálního hydrologického modelu BILAN. Časové řady ovlivněné změnou klimatu byly získány jednoduchou přírůstkovou metodou, tj. pozorované časové řady srážek, teplot a vlhkostí vzduchu (vstupy do modelu BILAN) byly opraveny pro každou simulaci pomocí přírůstkových faktorů tak, aby měsíční změny těchto veličin byly stejné jako podle uvažované simulace klimatického modelu. Hydrologický model je nakalibrován s využitím pozorovaných dat, identifikované parametry jsou následně využity pro simulaci hydrologické bilance pro řady ovlivněné klimatickou změnou. Základní podstata možných změn hydrologické bilance na území České republiky vyplývá z projekcí srážek a teplot pro Evropu, tj. postupné zvyšování teplot během celého roku a pokles letních, růst zimních a stagnace ročních srážek. V období od začátku podzimu do začátku léta dochází k růstu srážek, jenž je doprovázen řádově stejným růstem územního výparu způsobeným růstem teplot. V letním období dochází k poklesu srážek a v důsledku úbytku zásob vody v povodí nemůže docházet k výraznému zvyšování územního výparu. Důležitým faktorem ovlivňující změny odtoku je posun doby tání v důsledku vyšší teploty přibližně z dubna na leden-únor. Změny odtoku v období leden-květen jsou tedy dominantně určeny právě odlišnou dynamikou sněhové zásoby, změny v letním období zejména úbytkem srážek. Výsledné odhady změn odtoku jsou zatíženy značnou nejistotou, nicméně lze identifikovat robustní jevy společné pro řadu simulací. Jak ukazují výsledky, na většině modelovaných povodí je pokles odtoků v období od dubna do října společný valné většině modelů. Na druhé straně, růst odtoku v zimních měsících je značně nejistý. S tím souvisí i nejistota spojená se změnami roční bilance odtoků.
Backward erosion piping is driven by seepage forces acting on the soil grains at the downstream end of the seepage path. A new device for the laboratory testing of backward erosion progression was developed and tested. The device consists of a plexiglass prism at which the seepage path has been predefined. The prism was equipped with an inflow consisting of gravel separated from tested sand by a strainer. The hydraulic gradient along the seepage pipe was observed by a set of piezometers and pressure cells, and the seepage discharge was measured volumetrically. The transported sediment was trapped in a vertical cone located downstream from the device. The progression of the seepage path, the piezometric heads and the trapped material was observed by two synchronous cameras. 15 trial tests have been carried out to date, and from these, the interim results are presented.